Method of accelerating photoiniferter polymerization, polymer produced thereby, and product produced therewith

The invention relates to an accelerated photoiniferter polymerization method which involves the addition of a polymerization accelerating amount of a at least one metal compound accelerator during the photoiniferter polymerization process. Preferably, the metal compound or compounds used are represented by the general formula M.sub.x L.sub.z wherein PA0 M is a cation having a valency of z of a metal which is selected from the group consisting of tin, zinc, cobalt, titanium, palladium, and lead; PA0 x is an integer of at least 1; PA0 L is an anion having a valency of x which is selected from the group consisting of C.sub.1-20 alkyl, -aryl, --OR, ##STR1## NO.sub.3.sup.--, SO.sub.4.sup..dbd., and PO.sub.4.sup.-3 ; R is selected from the group consisting C.sub.1-20 alkyl and aryl; and PA0 z is an integer of at least 1. Most preferably, the metal compound is selected from the group consisting of stannous 2-ethylhexanoate, zinc 2-ethylhexanoate and mixtures thereof.

TECHNICAL FIELD 
This invention relates to the acceleration of a photoiniferter 
polymerization method, polymers produced by the method, and products 
produced with the polymers. 
BACKGROUND 
Photoiniferter technology is a recently developed technology which allows 
for the polymerization of block copolymers from various monomers An 
advantage of photoiniferter technology is that it allows for the 
"tailoring" of block copolymers made therewith. The control of the 
polymerization provided by the photoiniferter technology permits 
"tailoring" of the block copolymers formed thereby so that a polymer 
having a wide spectrum of physical properties can be prepared. Such high 
precision tailoring is not possible with previously known polymerization 
methods such as thermal polymerization. 
The term "iniferter", or "photoiniferter" as it is also known, refers to a 
chemical compound that has a combined function of being a free radical 
initiator, transfer agent, and terminator, the term "iniferter" being a 
word formed by the underlined portions of the terms identifying these 
functions. The photo portion of the term indicates that the polymerization 
is photolytically induced. This term and its use in the production of 
block copolymers is well known, particularly because of the work of 
Takayuki Otsu of the Department of Applied Chemistry, Osaka City 
University, Osaka, Japan. This work is discussed, for example, in an 
article by Otsu et al entitled "Living Radical Polymerizations in 
Homogeneous Solution by Using Organic Sulfides as Photoiniferters", 
Polymer Bulletin, 7, 45-50 (1982), an article by Otsu et al entitled 
"Living Mono-and Biradical Polymerizations in Homogeneous System Synthesis 
of AB and ABA Type Block Copolymers", Polymer Bulletin, 11, 135-142 
(1984), and in European Patent Application No. 88303058.7, Publication No. 
0 286 376, publication date Oct. 12, 1988. 
Copending U.S. application Ser. No 07,356,650, filed May 19, 1989, which is 
a Continuation-In-Part of U.S. application Ser. No 7/212,594, Ali, et al., 
filed June 28, 1988 (assigned to the assignee of the present case) 
discloses the use of iniferter technology in the preparation of acrylic 
block copolymers having the requisite physical properties making them 
suitable for use in pressure-sensitive adhesive compositions. The control 
of the polymerization permits tailoring of the reinforced acrylic block 
copolymer to provide a balance of adhesion, cohesion, stretchiness and 
elasticity to make a successful pressure-sensitive adhesive. 
Copending U.S. application Ser. No. 07/212,593, filed June 28, 1988, Andrus 
Jr. et al., (also assigned to the assignee of the present case) discloses 
the use of iniferter technology in the preparation of acrylic block 
copolymers which can be tailored to provide optical clarity and resistance 
to oxidative and photochemical degradation which are employed to make 
shaped articles, sheet materials, and the like. 
Copending U.S. application Ser. No. 07/393,550, filed Aug. 14, 1989, Kumar, 
et al., provides novel siloxane iniferter compounds which can be used in 
making tailor-made vinyl-siloxane block copolymers. The control of the 
polymerization provided by the novel siloxane iniferter compounds permits 
"tailoring" of the vinyl-siloxane block copolymers so that a wide spectrum 
of physical properties can be introduced. 
Copending U.S. application Ser. No. 7/393,557, filed Aug. 14, 1989, Kumar, 
et al., discloses flexible substrates coated with a release coating 
comprising the vinyl-siloxane block copolymers prepared according to 
copending U.S. application Ser. No. 07/393,550. 
While photoiniferter technology provides a unique way to make precisely 
tailored block copolymers which cannot be made by conventional techniques, 
such photopolymerization reactions can sometimes take an extended period 
of time to occur. Reaction times on the order of 2 to 50 hours, depending 
upon the components used, with the majority of reactions requiring 24 
hours or more have been found to be typical, depending upon the intensity 
of the radiation with faster reaction times being observed at greater 
intensities. None of the above references disclose or suggest any methods 
of accelerating the photoiniferter polymerization processes. 
Okuzuwa, Hirai and Hakishima, Journal of Polymer Science, Volume 7, 
1039-1053, 1969, discusses the thermal polymerization of acrylates and 
methacrylates with AIBN (azo-isobutyronitrile) in the presence of 
ZnCl.sub.2 and SnCl.sub.4. The thermal polymerizations of Okuzuwa are 
conducted in bulk since, according to Okuzuwa, ZnCl.sub.2 acts as a 
complexing agent with methyl methacrylate (MMA) resulting in a decrease in 
activation energy. No solvent was found which dissolved the complex 
without causing its dissociation. Thus, no polymerization rate 
acceleration was observed in the presence of solvents. 
Levens U.S. Pat. No. 4,421,822 (assigned to the assignee of the present 
case) teaches that the conventional photopolymerization of acrylates in 
solution or in film can be carried out in the presence of oxygen wherein 
oxidizable tin salts are added. However, rate enhancement in the absence 
of oxygen is not discussed. Moreover, no data is provided on the extent of 
rate enhancement in the presence and absence of oxidizable tin salts. 
Furthermore, Levens does not teach or suggest the use of such oxidizable 
tin salts as accelerators in photoiniferter polymerizations. 
A need therefore exists for an accelerated photoiniferter polymerization 
technique which can substantially increase the reaction rate of 
photoiniferter polymerization reactions resulting in a more time-efficient 
photoiniferter polymerization process. 
BRIEF DESCRIPTION OF THE INVENTION 
We have found an accelerated method of preparing block polymers and 
copolymers which involves the addition of a polymerization accelerating 
amount of a metal compound accelerator during the photoiniferter 
polymerization process. 
The invention relates to a method of making a polymer or copolymer which 
comprises mixing (i) an iniferter represented by the general formula 
I(T).sub.n, capable upon being subjected to an appropriate energy source 
of forming a terminator free radical of the formula nT.multidot. and an 
initiator free radical of the formula I(.multidot.).sub.n wherein n is an 
integer of at least 1, wherein the initiator free radical 
I(.multidot.).sub.n is a highly reactive free radical capable of 
initiating free radical polymerization, and the terminator free radical 
T.multidot. is a less reactive free radical which is generally much less 
capable of initiating free radical polymerization of free radically 
polymerizable monomer but capable of rejoining with I(.multidot.).sub.n or 
a free radical polymer segment free radically polymerized with 
I(.multidot.).sub.n upon termination of the energy source and (ii) a first 
monomer charge comprising free radically polymerizable monomer, in order 
to form a first mixture; 
exposing the mixture to an energy source capable of forming free radicals 
I.multidot. and nT.multidot.; 
maintaining the exposure until the free radically polymerizable monomer of 
the first monomer charge polymerizes with I.multidot. to form a free 
radical polymer segment represented by the formula IA'.multidot.; 
wherein A' comprises a polymer block comprising polymerized free radically 
polymerizable monomer of the first monomer charge; 
terminating the exposure, whereby I(A'.multidot.).sub.n and nT.multidot. 
combine to form a polymer represented by the formula I(A'T).sub.n or 
alternatively maintaining the exposure of I(A'.multidot.).sub.n and 
nT.multidot. to the energy source; 
optionally mixing I(A'T).sub.n or mixing I(A'.multidot.).sub.n and 
nT.multidot. with a second monomer charge comprising free radically 
polymerizable monomer in order to form a second mixture; 
exposing the mixture of I(A'T).sub.n and the second monomer charge to an 
energy source capable of forming free radicals I(A'.multidot.).sub.n and 
nT.multidot., or alternatively maintaining the exposure of 
I(A'.multidot.).sub.n and nT.multidot. which is mixed with the second 
monomer charge, to the energy source; 
maintaining the exposure until the free radically polymerizable monomer of 
the second monomer charge polymerizes with the free radical 
I(A'.multidot.).sub.n to form a free radical copolymer segment represented 
by the formula I(A'A".multidot.).sub.n wherein A" comprises a polymer 
block comprising polymerized free radically polymerizable monomer of the 
second monomer charge; 
and terminating the exposure whereby I(A'A".multidot.)n and nT.multidot. 
combine to form a copolymer represented by the formula I(A'A"T).sub.n : 
wherein the improvement comprises adding a polymerization accelerating 
amount of at least one metal compound which is capable of accelerating the 
free radical polymerization wherein the metal compound is present during 
the polymerization of at least one monomer charge, and wherein said metal 
compound does not interact with said free radically polymerizable monomer 
of said first monomer charge or said free radically polymerizable monomer 
of said second monomer charge in order to form an insoluble compound in an 
amount which would substantially interfere with the free radical 
polymerization of said free radically polymerizable monomer of said first 
monomer charge or said free radically polymerizable monomer of said second 
monomer charge. 
The resultant polymer is characterized by having the formula I(A'A".sub.y 
T).sub.n where I,A', A", T and n are defined above and y is zero or 1, and 
by including residual metal compound accelerator.

DETAILED DESCRIPTION OF THE INVENTION 
I. Accelerated Photoiniferter Polymerization 
Thus, the present invention relates to the use of at least one metal 
compound accelerator during a photoiniferter polymerization reaction in 
order to dramatically increase the polymerization reaction rate. 
Useful metal compounds include but are not limited to those of general 
formula M.sub.x L.sub.z wherein 
M is a cation having a valency of z of a metal which is selected from the 
group consisting of tin, zinc, cobalt, titanium, palladium, and lead; 
x is an integer of at least 1; 
L is an anion having a valency of x which is selected from the group 
consisting of C.sub.1-20 alkyl, -aryl, --OR, 
##STR2## 
NO.sub.3.sup.-, SO.sub.4.sup.=, and PO.sub.4.sup.-3 ; 
R is selected from the group consisting C.sub.1-20 alkyl and aryl; and 
z is an integer of at least 1. 
Suitable metal compound accelerators include but are not limited to the 
following: Sn.sub.x L.sub.z, Co.sub.x L.sub.z, Zn.sub.x L.sub.z, Ti.sub.x 
L.sub.z, Pb.sub.x L.sub.z, Pd.sub.x L.sub.z, etc. and mixtures thereof. 
Examples of specific metal compound accelerators include: (C.sub.4 
H.sub.9).sub.2 Sn(OCH.sub.3).sub.2, (C.sub.4 H.sub.9).sub.2 
Sn(OOCCH.sub.3).sub.2, (C.sub.4 H.sub.9).sub.3 SnOOCCH.sub.3, cobalt 
octanoate, lead disulfone, Zn(Oct).sub.2, tin octanoate, etc. 
Most preferably, the metal compound is selected from the group consisting 
of stannous 2-ethylhexanoate, [Sn(Oct).sub.2 ], zinc 2-ethylhexanoate, 
[Zn(Oct).sub.3 ], and mixtures thereof, for reasons of their high 
solubility in organic solvents and the very high acceleration rate 
obtained therewith. 
The metal compound should be present in an amount sufficient to accelerate 
the polymerization of the free radically polymerizable monomer. 
Preferably, about 0.1 to about 10 mole % of metal compound is used based 
upon the monomer charge to which the metal compound is added in order to 
obtain a high rate of acceleration. Most preferably, about 1 to about 3 
mole % of metal compound is used based upon the monomer charge to which 
the metal compound is added, for reasons of optimum acceleration and 
optimum performance of the final polymer. The metal compound accelerator 
used should be soluble in any organic solvent used or in free radically 
polymerizable monomer. 
Above about 3 mole % of metal compound results in a plasticizing effect 
which is not desirable for some applications, but which could be desirable 
for certain applications such as pressure sensitive adhesive compositions. 
Also, the use of above about 3 mole % of metal compound has not been found 
to increase the acceleration rate to a greater extent than 3 mole %. The 
use of above about 10 mole % of metal compound accelerator results in the 
absorption of radiation from the radiant energy source, thus causing 
interference with the polymerization process. 
According to the above described accelerated photoiniferter polymerization 
reaction either a first monomer charge or both a first monomer charge and 
a second monomer charge can be used in forming the polymer. When only a 
first monomer charge is used a polymer represented by the formula 
I(A'T).sub.n is formed. When both a first monomer charge and a second 
monomer charge are used a copolymer represented by the formula 
I(A'A"T).sub.n is formed. The first monomer charge can comprise one or 
more types of free radically polymerizable monomer compound. Similarily, 
the second monomer charge can comprise one or more types of free radically 
polymerizable compound. 
An accelerator compound is present, of course, when only a first monomer 
charge is used in order to accelerate the polymerization reaction. If both 
a first monomer charge and second monomer charge are used a polymerization 
accelerating amount of an accelerator metal compound may be present during 
the polymerization of the first monomer charge, the second monomer charge, 
or both the first monomer charge and the second monomer charge. The stage 
or stages at which the accelerator compound is added depends upon a number 
of factors such as the reactivity and structure of the monomer which is 
being polymerized. In the case of two monomer charges, the metal compound 
accelerator is preferably added to the monomer charge comprising the less 
reactive monomer. In both the cases wherein one or two monomer charges are 
used, the accelerator compound is preferably added all at once rather than 
gradually in order to minimize interruption of the polymerization 
reaction. 
In order to conduct the accelerated photoiniferter polymerization, the 
reactants, including the photoiniferter, free radically polymerizable 
monomer, and any solvent employed, are charged into an energy 
source-transparent vessel and therein subjected to the energy source. The 
reactants can be charged into the vessel in any order. Preferably, 
however, the solvent, photoiniferter, and monomer are combined to form a 
mixture prior to the addition of the metal compound accelerator. Most 
preferably, a mixture is formed by dissolving the photoiniferter in the 
solvent prior to the addition of the monomer charge. This is followed by 
the addition of the metal compound accelerator. 
If only a first monomer charge is to be used, a polymerization accelerating 
amount of accelerator metal compound is added to the vessel as indicated 
above. If both a first monomer charge and second monomer charge is used a 
polymerization accelerating amount of the accelerator metal compound can 
be added to the vessel so that it is present during the polymerization of 
the first monomer charge or it can be added later so that it is present 
during the polymerization of the second monomer charge. Alternatively, an 
excess of accelerator metal compound can be added so that it is present 
during the polymerization of the first monomer charge and the second 
monomer charge. 
The reaction is preferably conducted in a vessel with agitation to permit 
uniform exposure of the reactants to the energy source. While most of the 
reactions have been conducted by employing a batch process, it is possible 
to utilize the same technology in a continuous polymerization operation. 
The reaction mixture may include a suitable inert solvent but it is not 
necessary since some of the monomeric materials are liquid themselves and 
may thus be charged into the reaction vessel without utilization of a 
solvent. 
In the situation wherein two monomer charges are used, preferably the 
I(A'T).sub.n block polymer formed from the first monomer charge, solvent, 
and second monomer charge are combined prior to the addition of the metal 
compound accelerator if the metal compound accelerator is used during the 
polymerization of the second monomer charge. 
The solvent, if utilized in the free radical polymerization, may be any 
substance which is liquid in a temperature range of about -10.degree. C. 
to about 50.degree. C., is substantially transparent to the energy source 
employed to permit dissociation of the iniferter to form free radicals, is 
inert to the reactants and product, and will not otherwise adversely 
affect the reaction. Suitable solvents include water, toluene, alkyl 
acetates such as ethyl acetate, alkanes such as hexane or heptane, and 
alcohols such as methyl alcohol, ethanol, isopropyl alcohol, and mixtures 
of one or more of these. Other solvent systems are useful. The amount of 
solvent is generally about 30 to 80 percent by weight based on the total 
weight of the reactants and solvent. In addition to solution 
polymerization herein described, the polymerization may be carried out by 
other well known techniques such as suspension, emulsion and bulk 
polymerization. 
The particular energy source and its intensity are selected to result in 
dissociation of the iniferter to free radicals. When employing a 
photoiniferter which will dissociate upon exposure to ultraviolet light 
radiation, an ultraviolet light source is utilized. When employing a 
photoiniferter which will dissociate upon exposure to visible light 
radiation, a visible light source is utilized. A visible light source is 
preferably used since it is more convenient and is considered less 
hazardous. The intensity and rate of radiation is chosen so that it will 
advance the polymerization at a reasonable rate without deleteriously 
affecting the polymer segment being produced. A light source having a 
wavelength on the order of 200 to 800 nm spaced approximately 10 cm from 
the reactants to provide an exposure of 2 milliwatts per square centimeter 
has been found to produce suitable results. If the energy source is 
ultraviolet radiation, a suitable ultraviolet light transparent vessel is 
utilized. 
In the presence of a polymerization accelerating amount of at least one 
metal compound, reaction times have been found to range from about 0.2 to 
about 5 hours, typically about 2.4 to about 5 hours for the majority of 
cases for the preparation of I(A'T).sub.n and I(A'A''T).sub.n depending 
upon the type of monomer used. 
The iniferter is caused to dissociate to form free radicals by exposure to 
an appropriate energy source. The preferred iniferter is one which will 
dissociate upon exposure to a radiant energy source. The amount of 
iniferter used depends upon the molecular weight of the polymer desired. 
The more iniferter used, the lower the molecular weight of the resultant 
polymer. 
Upon exposure to the energy source, the iniferter dissociates to form free 
radicals which promote free radical polymerization. Upon completion of the 
free radical polymerization of the free radically polymerizable monomer, 
the energy source is discontinued to permit the free radically polymerized 
segments to recombine with the terminator portion of the iniferter to form 
polymer segments. A second monomer charge may then be introduced if 
desired, which is free radically polymerizable to the block A', and the 
new mixture is exposed to the energy source to cause dissociation of the 
terminator radical and free radical polymerization of the second monomer 
charge onto the first polymer segment, that now being the initiator of the 
second free radical polymerization. Upon completion of polymerization of 
the second monomer charge, the energy source is terminated and the 
terminator portion of the iniferter recombines with the polymer block to 
provide a block copolymer of the formula I(A'A''T).sub.n. 
The accelerated photoiniferter polymerization method of the present 
invention can be used in the preparation of a variety of copolymers 
including, but not limited to, acrylic block copolymers useful as 
toughened thermoplastics, acrylic block copolymers useful as pressure 
sensitive adhesives, vinyl siloxane copolymers, etc. 
The use of accelerator metal compounds in the preparation of shaped dental 
articles comprising certain acrylic block copolymers is described in 
copending, concurrently filed U.S. patent application entitled "Dental 
Compositions, A Method of Making Shaped Dental Articles Via Photoiniferter 
Polymerization of the Dental Compositions, and Shaped Dental Articles 
Produced Thereby", Mitra, et al., Ser. No. 454,176, filed Dec. 21, 1989 
incorporated by reference herein. 
I.A. Accelerated Photoiniferter Polymerization of Acrylic Block Copolymers 
Useful as Toughened Thermoplastics 
The metal compound accelerator can be used according to the method of the 
present invention to accelerate the polymerization of the acrylic block 
copolymers prepared by the use of iniferter technology in copending U.S. 
application Ser. No. 212,593, Andrus Jr., et al., which is incorporated by 
reference herein. 
The method is similar to that described above wherein with respect to the 
iniferter I(T).sub.n, n is an integer of at least 2 and the first monomer 
charge is selected from the group consisting of (i) acrylic monomer 
polymerizable to form an acrylic polymer block having a glass transition 
temperature of less than 0.degree. C. and (ii) monomer polymerizable to 
form a thermoplastic polymer block having a glass transition temperature 
of at least 50.degree. C. which is free radically polymerizable in the 
presence of (I.multidot.).sub.n to form a first polymer block; 
and wherein a second monomer charge is added, wherein the second monomer 
charge is a member of the group consisting of monomer (i) and monomer (ii) 
which was not selected as the first monomer charge, the second monomer 
charge comprising monomer which is free radically polymerizable in the 
presence of I(A'.).sub.n to form a second polymer block. 
The invention also relates to sheet materials containing the copolymer 
formed according to the above accelerated method. 
The most preferred iniferters for producing the ABA block copolymers 
(wherein A.dbd.A" and B.dbd.A') are selected from the group consisting of 
xylylene bis (N,N-diethyl dithiocarbamate) and xylylene bis (N-carbazolyl 
dithiocarbamate). 
I.B. Accelerated Photoiniferter Polymerization of Acrylic Block Copolymers 
Useful as Pressure Sensitive Adhesives 
The metal compound accelerator can also be used according to the method of 
the present invention to accelerate the polymerization of acrylic block 
copolymers having the requisite physical properties making them suitable 
for use in pressure sensitive adhesive compositions prepared by the use of 
iniferter technology in copending U.S. application, Ser. No. 07/212,594, 
Ali, et al., which is incorporated by reference herein. 
This particular accelerated method is similar to the general acceleration 
method described above wherein said iniferter is represented by the 
general formula I(T).sub.n wherein n is an integer of at least 2 and 
wherein the first monomer charge comprises acrylic monomer which is free 
radically polymerizable in the presence of I(.multidot.).sub.n to form an 
acrylic polymer block having a glass transition temperature of less than 
0.degree. C.; 
and the second monomer charge comprises monomer which is free radically 
polymerizable in the presence of I(A'.multidot.).sub.n to form a 
thermoplastic block having a glass transition temperature of at least 
30.degree. C.; 
and sufficient compatible tackifier is blended with the second monomer 
charge, I(A'.multidot.).sub.n and nT or I(A'A"T).sub.n in order to endow 
I(A'A"T).sub.n with adhesive tack. 
The most preferred iniferters for producing the ABA block copolymers 
(wherein A.dbd.A" and B.dbd.A') according to the accelerated method of 
present invention are selected from the group consisting of xylylene bis 
(N,N-diethyl dithiocarbamate) and xylylene bis (N-carbazolyl 
dithiocarbamate). 
The PSA compositions comprise reinforced acrylic ABA block copolymer of the 
formula I(BAT).sub.n, as previously defined, and adhesive tackifier. If 
tackifier is employed, the amount is selected to provide sufficient 
adhesive tack to make the composition useful as a PSA. This amount would 
typically be on the order of 0 to 150 parts by weight per 100 parts ABA 
block copolymer. 
The adhesive copolymer compositions prepared in accordance with the present 
invention are easily coated upon suitable flexible or inflexible backing 
materials by conventional coating techniques to produce adhesive coated 
sheet materials in accordance with the present invention. The flexible 
backing material may be any material conventionally utilized as a tape 
backing or any other flexible material. 
I.C. Accelerated Photoiniferter Polymerization of Vinyl-Siloxane Copolymers 
The metal compound accelerator can also be used according to the method of 
the present invention to accelerate the polymerization of vinyl-siloxane 
copolymers described in copending U.S. application Ser. No. 07/393,550, 
Kumar, et al., Siloxane Iniferter Compounds, Block Copolymers Made 
Therewith and a Method of Making The Block Copolymer incorporated by 
reference herein. The vinyl siloxane copolymers prepared according to the 
accelerated method can be used to prepare coated sheet materials therewith 
as in copending U.S. application Ser. No. 07/393,557, Kumar, et al., 
General Purpose Siloxane Release Coatings, which is incorporated by 
reference herein. 
The method is similar to the general acceleration method described above 
wherein the iniferter of the general formula I(T).sub.n is represented by 
the formula 
##STR3## 
wherein 
T and X are organic groups selected so that the T--X bond is capable of 
dissociating upon being subjected to an appropriate energy source to form 
a terminator free radical of the formula T. and an initiator free radical 
of the formula 
##STR4## 
the initiator free radical being sufficiently reactive to initiate free 
radical polymerization of free radially polymerizable monomer and the 
terminator free radical being insufficiently capable of initiating free 
radical polymerization of free radically polymerizable monomer but capable 
of rejoining with the initiator free radical or a free radical polymer 
segment free radically polymerized with the initiator free radical; 
wherein 
R.sup.1, R.sup.2, R.sup.5 and R.sup.6 are monovalent moieties selected from 
the group consisting of hydrogen, C.sub.1-4 alkyl C.sub.1-4 alkoxy and 
aryl which can be the same or are different; 
R.sup.3 and R.sup.4 are monovalent moieties which can be the same or 
different selected from the group consisting of C.sub.1-4 alkyl, C.sub.1-4 
fluoroalkyl including at least one fluorine atom and aryl; 
R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are selected so 
that they do not prevent the initiator free radical from initiating free 
radical polymerization or the combining of the terminator free radical 
with the initiator free radical or a polymer free radical segment 
including the initiator free radical; 
Y is selected from the group consisting of --X--T and --Z wherein X and T 
are defined above and Z is an organic moiety that will not dissociate to 
form free radicals when subjected to the energy source; 
Y.sub.1 is selected from the group consisting of --X. and --Z; 
m is an integer of 10 or greater; 
the exposing the first mixture to an energy source forms free radicals 
T.multidot. and 
##STR5## 
the maintaining the exposure results in the polymerization of the initiator 
radical and the free radically polymerizable monomer of the first monomer 
charge to form a free radical block copolymer segment represented by the 
formula 
##STR6## 
wherein A' represents a polymer block comprising polymerized free 
radically polymerizable monomer of the first monomer charge; and 
G is selected from the group consisting of --Z and --X--A'.multidot.; 
the terminating the exposure forms a block copolymer represented by the 
formula 
##STR7## 
wherein P is selected from the group consisting of --X--A'--T and --Z, 
wherein X, A', T, and Z are defined above or alternatively maintaining the 
exposure of 
##STR8## 
and T.multidot.; 
the optionally mixing 
##STR9## 
or the mixing nT.multidot. and 
##STR10## 
with the second monomer charge comprising free radically polymerizable 
monomer forms the second mixture; 
the exposing the mixture of 
##STR11## 
and the second monomer charge to an energy source capable of forming free 
radical T.multidot. and 
##STR12## 
or alternatively maintaining the exposure of 
##STR13## 
and nT.multidot., which is mixed with the second monomer charge, to the 
energy source; 
the maintaining the exposure results in the polymerization of the radically 
polymerizable monomer with the free radical 
##STR14## 
to form a free radical block copolymer segment represented by the formula 
##STR15## 
wherein A" represents a polymer block comprising polymerized free 
radically polymerizable second monomer; and 
K is selected from the group consisting of --X--A'--A".multidot. and --Z; 
and 
the terminating the exposure results in the combining of 
##STR16## 
and T.multidot. to form a block copolymer represented by the formula 
##STR17## 
wherein N is selected from the group consisting of --X--A'A"T and --Z. 
The present invention also relates to a coated sheet material similar to 
that described in U.S. application Ser. No. 07/393,550, incorporated by 
reference herein, comprising a flexible sheet material and a release 
coating prepared according to the accelerated method described above 
covering at least a portion of one major surface thereof wherein the 
release coating comprises a block copolymer having a formula selected from 
the group consisting of AB and ABA; 
wherein A comprises at least one vinyl polymeric block; 
wherein each polymeric block comprises polymerized free radically 
polymerizable monomer, wherein each polymeric block has a T.sub.g or 
T.sub.m above about -20.degree. C. and wherein A comprises at least about 
40 weight percent of the block copolymer; 
wherein B is a siloxane polymeric block having a number average molecular 
weight above about 1000; 
and wherein the weight percent of said siloxane polymeric block is enough 
to provide said block copolymer with a surface release value not greater 
than about 50 Newtons/dm; and 
wherein the block copolymer has the formula 
##STR18## 
wherein T, A, X, L, R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5 and 
R.sub.6 are as previously defined. 
EXAMPLES 
The following detailed description includes exemplary accelerated 
preparations of acrylic copolymers useful as pressure sensitive adhesives, 
acrylic copolymers useful as toughened thermoplastics, and vinyl-siloxane 
copolymers. All parts and percentages are by weight unless otherwise 
specified. 
Definitions of Terms 
The number-average molecular weight (M.sub.n ), and weight-average 
molecular weight (M.sub.w ), are well known mathematical descriptions of 
the molecular weight distribution of a polymer sample. 
Each of the foregoing is a well known term used by polymer chemists and 
others. Further explanation of the derivation of these terms may be found 
in Experimental Methods in Polymer Chemistry, Wiley and Sons, 1981, 
Chapter 3 entitled "Molecular Weight Averages", pages 57-61. 
The block copolymers prepared according to the accelerated method of the 
present invention are described in a short-hand way depending upon the 
monomer forming each block. For example, MMA-b-BA-b-MMA refers to a 
copolymer having blocks ("b") of polymerized methyl methacrylate ("MMA") 
and a block of butyl acrylate ("BA"). For example, MMA-b-BA-b-MMA refers 
to an ABA block copolymer having two A (polymethyl methacrylate) blocks 
and a single B midblock (butyl acrylate). 
Abbreviations 
BA=Butyl acrylate; 
MMA=Methyl methacrylate; 
IOA=Isooctyl acrylate; 
AA=Acrylic acid; 
NVP=N-vinyl-2-pyrrolidone; 
XDC=Xylylene bis(N,N-diethyl dithiocarbamate); 
Sn(Oct).sub.2 =Stannous 2-ethylhexanoate; and 
Zn(Oct).sub.2 =Zinc 2-ethylexanoate. 
Test Methods 
The test methods used to evaluate the block copolymers of the examples are 
industry standard tests. The test methods which characterize the polymers 
prepared according to the accelerated method of the invention are those 
which demonstrate its molecular architecture. The gel permeation 
chromatography (GPC), inherent viscosity (I.V.) modulus, percent 
elongation, and tensile strength measurement results have been obtained. 
The standard tests are described in detail in various publications of the 
American Society for Testing and Materials (ASTM), Philadelphia, Pa. The 
standard test methods are described in detail below. The reference source 
of each of the standard test methods is also given. 
Gel Permeation Chromatography 
The characterization of the molecular weight distribution of the polymers 
has been by conventional gel permeation chromatography (GPC). A 
Hewlett-Packard Model 1084B, high performance liquid chromatograph 
equipped with Styragel.TM. columns was used. The system was calibrated 
using polystyrene standards. All molecular weight averages are polystyrene 
equivalent molecular weights. The molecular weight averages and 
polydispersities were calculated according to accepted practices. GPC test 
methods are further explained in "Modern Size Exclusion Liquid 
Chromatography" Practice of Gel Permeation Chromatography, John Wiley and 
Sons, 1979. 
Modulus--Elongation--Tensile Measurements 
The mechanical properties of the films formed from the MMA-BA-MMA copolymer 
formed according to the method of this invention were measured according 
to the procedures established by the American Standard Test Methods (ASTM) 
which can be found under the designations: D-412-83, "Rubber Properties in 
Tension" and D 638M-84, "Tensile Properties of Plastics". 
Preparation of films for test purposes occurred as follows. Films were cast 
from solution upon a substrate which permitted subjecting the film to 16 
hours of drying in a vacuum oven at 50.degree. C. The film thus formed was 
cut to standard dumbbell shapes in order to provide test samples for 
insertion into the jaws of an Instron.TM. tensile test instrument 
available from Instron Company (Model #1122) where they were tested under 
ambient conditions in a testing room controlled at 23.degree. C. and a 
humidity of 50%. 
The prescribed dumbbell-shaped specimens were stretched at a constant rate 
to the breaking point. The tensile strength at break was recorded. The 
elongation was expressed as a percentage of the original length. The 
modulus (stiffness) and tensile strength were calculated based on the 
following formulae where "force" is expressed in Newtons (N), linear 
dimensions in meters and the modulus and tensile units are expressed as 
mega pascals (MPa). 
##EQU1## 
EXAMPLE 1 
Control Experiment Involving the Polymerization of BA with Photoiniferter 
Compound XDC in the Absence of both Stannous 2-ethylhexanoate and Zinc 
2-ethylhexanoate 
A cylindrical reaction bottle was charged with 30 ml butyl acrylate (BA) 
monomer, 0.15 grams of xylylene bis(N,N-diethyl dithiocarbamate) (XDC) 
photoiniferter and 50 ml toluene solvent. The cylindrical reaction bottle 
was purged with nitrogen for 10 minutes before sealing and placing the 
sealed bottle in a roller mechanism. The rotating sealed bottle was 
exposed for 3 hours to ultraviolet radiation from six General Electric 15 
watt cylindrical black light lamps. The reaction bottle was unsealed and 
.sup.1 H NMR spectroscopy was utilized to determine the percentage 
conversion of a small removed sample. The reaction bottle was again purged 
with nitrogen, resealed, and further subjected to ultraviolet radiation 
until a total exposure time of approximately 24 hours had elapsed. .sup.1 
H NMR spectroscopy was again utilized to determine the percentage 
conversion of a small removed sample. The .sup.1 H NMR results for Example 
1 are set forth in Table I below. 
EXAMPLE 2 
Polymerization of BA with XDC in Presence of Stannous 2-ethylhexanoate 
The procedure of Example 1 was followed. The amount of components utilized 
were as follows: 30 ml of butyl acrylate monomer, 0.15 grams of xylylene 
bis(N,N-diethyl dithiocarbamate) (XDC) photoiniferter, 50 ml of toluene 
solvent. In addition, 1.54 grams of stannous 2-ethylhexanoate (metal 
compound accelerator) were charged into the reaction bottle before 
exposure to the ultraviolet radiation. Percentage conversion was 
determined by .sup.1 H NMR spectroscopy. The NMR results for Example 2 are 
reported in Table I below. 
EXAMPLE 3 
Polymerization of BA with XDC in Presence of Zinc 2-ethylhexanoate 
The procedure of Example 2 was followed. The amount of components utilized 
were as follows: 30 ml of butyl acrylate monomer, 0.15 grams of (XDC) 
photoiniferter, 50 ml (43.3 grams) of toluene solvent, and 5.8 grams of 
zinc 2-ethylhexanoate (metal compound accelerator). The .sup.1 H NMR 
spectroscopy results for Example 3 are reported in Table I below. 
TABLE I 
__________________________________________________________________________ 
Difunctional 
Metal Metal 
Photoiniferter 
Compound 
Compound 
Monomer 
Compound 
Accelerator 
Accelerator 
Solvent 
Exposure 
Percentage 
Example 
BA XDC Sn(Oct).sub.2 
Zn(Oct).sub.2 
Toluene 
Time (hours) 
Conversion (%)* 
__________________________________________________________________________ 
1 30 ml 0.15 g 00 00 50 ml 
3 h 28 
30 ml 0.15 g 00 00 50 ml 
.about.24 
h 100 
2 30 ml 0.15 g 1.54 g 00 50 ml 
3 h 87 
30 ml 0.15 g 1.54 g 50 ml 
4 h 100 
3 30 0.15 g 00 5.9 g 50 ml 
3 h 44 
(22% solid) 
__________________________________________________________________________ 
*percentage conversion was determined by NMR. 
The data contained in Table I above demonstrates that the rate of 
photopolymerization reactions are much faster in the presence of metal 
compound accelerators than photopolymerization reactions in the absence of 
metal compound accelerators. 
Examples 4 and 5 describe the preparation of toughened thermoplastics. 
EXAMPLE 4 
Control Experiment Involving the Synthesis of Triblock Polymer MMA-BA-MMA 
in the Absence of Stannous 2-ethylhexanoate 
A cylindrical reaction bottle was charged with 113.3 grams of BA monomer, 
0.75 grams of XDC photoiniferter and 113.3 grams of EtoAC solvent. The 
mixture was purged with nitrogen for 10 minutes before sealing and placing 
the sealed bottle in a roller mechanism. The rotating, sealed bottle was 
exposed to ultraviolet radiation from six General Electric 15 watt black 
light lamps 47 hours. At this point, the ultraviolet source was turned 
off. A percent solid calculation revealed greater than 98% reaction. 
Into a second cylindrical reaction bottle of 120 ml was charged 20 grams of 
the above poly BA-XDC, 23.7 grams of methyl methacrylate monomer and 38.6 
grams of ethyl acetate solvent. The reaction bottle was then purged for 10 
minutes with nitrogen. The reaction bottle was then sealed and placed in 
the roller mechanism for further exposure to ultraviolet radiation which 
continued for 66 hours. The resulting triblock copolymer solution was 
removed. The composition of the resultant polymer was determined by .sup.1 
H NMR spectroscopic analysis. A thin film of the triblock copolymer 
solution was cast and dried and then subjected to mechanical tests. The 
results of these tests are reported in Table II, Example 4. 
EXAMPLE 5 
Synthesis of Triblock Polymer MMA-BA-MMA in the Presence of Stannous 
2-ethylhexanoate 
A cylindrical reaction bottle was charged with 7.05 g of dry polybutyl 
acrylate prepared according to the method of Example 4, 28.2 grams of 
methyl methacrylate monomer, 35.2 grams of toluene solvent and 14 grams of 
stannous 2-ethylhexanoate (metal compound accelerator). Purging for 10 
minutes with nitrogen followed before the reaction bottle was sealed and 
placed in the roller mechanism. The rotating, sealed bottle was exposed to 
ultraviolet radiation from six General Electric 15 watt black light lamps 
for 6.6 hours. The resulting triblock copolymer solution was removed. The 
composition of the resultant polymer was determined by .sup.1 H NMR 
spectroscopic analysis. A thin film of the polymer was cast and dried and 
then subjected to mechanical tests. The results of these tests are 
reported in Table II, Example 5. 
TABLE II 
______________________________________ 
Ex- Expo- Tensile 
Modu- 
am- sure Strength 
lus Elonga- 
ple Composition Time (MPa) (MPa) tion % 
______________________________________ 
4 MMA--BA--MMA 66 h 20.65 452.018 
10 
36-28-36 
made in absence 
of stannous 
2-ethylhexanoate 
5 MMA--BA--MMA 6.6 h 22.9974 
410.298 
17 
40-20-40 
made in presence 
of stannous 
2-ethylhexanoate 
______________________________________ 
The data contained in Table II above demonstrates that copolymer of 
MMA-BA-MMA was prepared about 10 times faster in the presence of 
Sn(Oct).sub.2 than in absence of Sn(Oct).sub.2 with very similar 
mechanical properties observed. 
EXAMPLES 6-10 
An additional series of experiments were performed to attempt the 
polymerization of BA, without the use of an accelerator, with the use of 
stannous 2-ethylhexanoate as an accelerator, with the use of zinc 
2-ethylhexanoate as an accelerator, with the use of both stannous 
2-ethylhexanoate and zinc 2-ethylhexanoate as accelerators, without the 
use of initiator XDC (control experiment), etc. The results of the 
experiments are reported in Table III below. It was observed that the 
reaction rate was greater when the combination of accelerators stannous 
2-ethylhexanoate and zinc 2-ethylhexanoate were used rather than the use 
of either accelerator stannous 2-ethylhexanoate or zinc 2-ethylhexanoate 
separately. 
EXAMPLE 6 
Control Experiment Involving the Polymerization of BA with XDC in the 
Absence of both Stannous 2-ethylhexanoate and Zinc 2-ethylhexanoate 
A 120 ml volume cylindrical reaction bottle was charged with 26.6 grams of 
BA monomer, 0.15 grams of XDC photoiniferter and 43 grams of toluene 
solvent. The mixture was purged with nitrogen for 10 minutes before 
sealing and placing the sealed bottle in a roller mechanism. The rotating, 
sealed bottle was exposed to ultraviolet radiation from six General 
Electric 15 watt black light lamps. The reaction was monitored from 10 
minutes up to 24 hours. The percent conversion was determined by .sup.1 H 
NMR spectroscopy. The results are reported in Table III, Example 6. The 
percentage reaction versus time for Example 6 is plotted as line A in FIG. 
1. 
EXAMPLE 7 
Polymerization of BA with XDC in Presence of Stannous 2-ethylhexanoate 
A 120 ml volume cylindrical reaction bottle was charged with 26.6 grams of 
BA monomer, 0.15 grams of XDC photoiniferter, 43 grams of toluene solvent 
and 1.55 grams of stannous 2-ethylhexanoate accelerator metal compound. 
The mixture was purged with nitrogen for 10 minutes before sealing and 
placing the sealed bottle in a roller mechanism. The rotating, sealed 
bottle was exposed to ultraviolet radiation from six General Electric 15 
watt black light lamps. The reaction was monitored from 10 minutes up to 
the completion of the reaction. The percent conversion was determined by 
.sup.1 H NMR spectroscopy. The results are reported in Table III, Example 
7. The percentage reaction versus time for Example 7 is plotted as line B 
in FIG. 1. 
EXAMPLE 8 
Polymerization of BA with XDC in Presence of a Mixture of Stannous 
2-ethylhexanoate and Zinc 2-ethylhexanoate 
A 120 ml volume cylindrical reaction bottle was charged with 26.6 grams of 
BA monomer, 0.15 grams of XDC photoiniferter, 43 grams of toluene solvent 
and 0.77 grams of stannous 2-ethylhexanoate (accelerator metal 
compound)and 0.15 gram (22% solid) of zinc 2-ethylhexanoate (accelerator 
metal compound). The mixture was purged with nitrogen for 10 minutes 
before sealing and placing the sealed bottle in a roller mechamism. The 
rotating, sealed bottle was exposed to ultraviolet radiation from six 
General Electric 15 watt black light lamps. The reaction was monitored 
from 10 minutes up to the completion of the reaction. The percent 
conversion was determined by .sup.1 H NMR spectroscopy. The results are 
reported in Table III, Example 8. The percentage reaction versus time for 
Example 8 is plated as line C in FIG. 1. 
FIG. 1 contains a plot of percent conversion versus time for Examples 6, 7 
and 8 designated as lines A, B, and C, respectively. FIG. 1 demonstrates 
that when photoiniferter reactions were performed in the presence and in 
the absence of metal accelerators, dramatically different slopes of the 
straight line plots were obtained. In the presence of Sn(Oct).sub.2 (line 
B) the photoiniferter reaction rate was increased significantly. Even 
greater rate acceleration was observed when mixtures of Sn(Oct).sub.2 and 
Zn(Oct).sub.2 were used (line C). 
EXAMPLE 9 
Control Experiment to Determine whether Stannous 2-ethylhexanoate can 
Initiate Polymerization of BA Monomer in the Absence of a Photoiniferter 
A 120 ml volume cylindrical reaction bottle was charged with 26.6 grams of 
BA monomer, 1.56 grams of stannous 2-ethylhexanoate (accelerator metal 
compound) and 42.8 grams of toluene solvent. The mixture was purged with 
nitrogen for 10 minutes before sealing and placing the sealed bottle in a 
roller mechamism. The rotating, sealed bottle was exposed to ultraviolet 
radiation from six General Electric 15 watt black light lamps. The 
reaction was monitored from 10 minutes up to 3.7 hours of irradiation. The 
percent conversion was determined by .sup.1 H NMR spectroscopy. The 
results are reported in Table III, Example 9. 
EXAMPLE 10 
Control Experiment to Determine whether Zinc 2-ethylhexanoate can Initiate 
Polymerization of BA Monomer in the Absence of a Photoiniferter 
A 120 ml volume cylindrical reaction bottle was charged with 26.6 grams of 
BA monomer, 5.9 (22% solid) grams of zinc 2-ethylhexanoate (accelerator 
metal compound) and 43 grams of toluene solvent. The mixture was purged 
with nitrogen for 10 minutes before sealing and placing the sealed bottle 
in a roller mechamism. The rotating, sealed bottle was exposed to 
ultraviolet radiation from six General Electric 15 watt black light lamps. 
The reaction was monitored from 10 minutes up to 3.7 hours of irradiation. 
The percent conversion was determined by .sup.1 H NMR spectroscopy. The 
results are reported in Table III, Example 10. 
TABLE III 
______________________________________ 
Example Example Example 
Example 
Example 
Exposure 
6 7 8 9 10 
Time % Yield % Yield % Yield 
% Yield 
% Yield 
______________________________________ 
10 min 9.2 41.5 49.8 No Rxn. 
No Rxn. 
20 min 13 58.2 65.2 No Rxn. 
No Rxn. 
30 min 19.9 68.3 76.5 No Rxn. 
No Rxn. 
1 hr 33 79.7 87.8 No Rxn. 
No Rxn. 
3.7 hr 66.8 92.5 100 &lt;5% No Rxn. 
.about.24 
hr 100 -- -- 
______________________________________ 
Example 6 BA + XDC + Toluene (line A, FIG. 1) 26.6 g + 0.15 g + 43 g 
Example 7 BA + XDC + Sn(Oct).sub.2 + Toluene (line B, FIG. 1) 26.6 g + 
0.15 g + 1.55 g + 43 g 
Example 8 BA + XDC + Zn(Oct).sub.2 + Sn(Oct).sub.2 + Toluene 26.6 g + 0.1 
g + 3.0 g 22% solid + 0.77 g + 43 g (line C, FIG. 1) 
Example 9 BA + Sn(Oct).sub.2 + Toluene 26.19 g + 1.56 g + 42.8 g 
Example 10 BA + Zn(Oct).sub.2 + Toluene 26.6 g + 5.9 g 22% solid + 43 g 
EXAMPLE 11 
Polymerization of MMA with XDC 
A 120 ml volume cylindrical reaction bottle was charged with 50 ml of MMA 
monomer and 0.3 grams of XDC photoiniferter. The mixture was purged with 
nitrogen for 10 minutes before sealing and placing the sealed bottle in a 
roller mechamism. The rotating, sealed bottle was exposed to ultraviolet 
radiation for 1 hour and 15 minutes from six General Electric 15 watt 
black light lamps. Analysis using .sup.1 H NMR spectroscopy revealed 22.7% 
conversion. 
EXAMPLE 12 
Polymerization of MMA with XDC in Presence of Stannous 2-ethylhexanoate 
A 120 ml volume cylindrical reaction bottle was charged with 50 ml of MMA 
monomer, 0.3 grams XDC photoiniferter, 3.0 grams of stannous 
2-ethylhexanoate (accelerator metal compound). The mixture was purged with 
nitrogen for 10 minutes before sealing and placing the sealed bottle in a 
roller mechamism. The rotating, sealed bottle was exposed to ultraviolet 
radiation for 1 hour and 15 minutes from six General Electric 15 watt 
black light lamps. Analysis using .sup.1 H NMR spectroscopy revealed 42% 
conversion. 
Examples 11 and 12 demonstrate a greater rate of MMA polymerization in the 
presence of Sn(Oct).sub.2 compared to MMA polymerization in absence of 
Sn(Oct).sub.2. 
EXAMPLE 13 
Polymerization of NVP with XDC 
A 120 ml volume cylindrical reaction bottle was charged with 28.25 grams of 
NVP monomer and 0.188 grams of XDC photoiniferter. The mixture was purged 
with nitrogen for 10 minutes before sealing and placing the sealed bottle 
in a roller mechanism. The rotating, sealed bottle was exposed to 
ultraviolet radiation for 1 hour and 15 minutes from six General Electric 
15 watt black light lamps. A percent solid calculation revealed that 17.7% 
reaction of NVP occurred. 
EXAMPLE 14 
Polymerization of NVP with XDC in Presence of Stannous 2-ethylhexanoate 
A 120 ml volume cylindrical reaction bottle was charged with 28.Z5 grams of 
NVP monomer, 0.188 grams of XDC photoiniferter and 2.07 grams of stannous 
2-ethylhexanoate (accelerator metal compound). The mixture was purged with 
nitrogen for 10 minutes before sealing and placing the sealed bottle in a 
roller mechamism. The rotating, sealed bottle was exposed to ultraviolet 
radiation for 1 hour and 15 minutes from six General Electric 15 watt 
black light lamps. 48.7% conversion of polymerization reaction of NVP 
occurred which was determined by a percent solid analysis. 
Examples 13 and 14 demonstrate a large rate enhancement of the 
photopolymerization of NVP monomer in the presence of accelerator compound 
compared to a photopolymerization reaction in the absence of accelerator 
compound. Examples 15 and 16 describe the preparation of 
pressure-sensitive adhesives. 
EXAMPLE 15 
Polymerization of IOA/AA with Photoiniferter Compound XDC 
A cylindrical 16 oz. reaction bottle was charged with 98 grams of IOA 
monomer, 2 grams of AA monomer, 1.02 grams of XDC photoiniferter and 200 
grams of EtoAc solvent. The mixture was purged with nitrogen for 10 
minutes. The bottle was sealed and placed in a roller mechamism. The 
rotating, sealed bottle was exposed to ultraviolet radiation from six 
General Electric 15 watt black light lamps for 48 hours. A conversion of 
greater than 97% was obtained. 
EXAMPLE 16 
Polymerization of P-(IOA/AA) with MMA in Presence of Stannous 
2-ethylhexanoate 
A 50 g portion of the polymer solution P-(IOA/AA) from Example 15 was 
charged into a 100 ml volume flask and the solvent was removed by rotary 
evaporation under vacuum. Into a small 4 ml volume vial 1.72 grams of 
P-(IOA/AA) polymer, 0.42 grams of MMA monomer and 0.11 grams of stannous 
2-ethylhexanoate (accelerator metal compound) were charged and the vial 
was placed in a shaker for homogeneous mixing. The solution was coated on 
a polyester film. The film was placed under General Electric 15 watt black 
light lamps and irradiated for 10 minutes. The polymer coated film was 
conditioned for 24 hours in a constant temperature testing room at 
22.degree. C. and 50% relative humidity, after which a shear strength test 
was performed. A shear value of 311 minutes was obtained. 
EXAMPLE 17 
Polymerization of P-(IOA/AA) with MMA 
Following the procedure of Example 16, 1.20 grams of dry P-(IOA/AA) polymer 
prepared according to Example 15 and 0.30 grams of MMA monomer were 
charged into a 4 ml volume vial which was placed in a shaker for mixing 
for 15 minutes in order to form a homogeneous solution. The homogeneous 
solution was coated onto a polyester film. The film was exposed for 10 
minutes to ultraviolet radiation from six General Electric 15 watt black 
light lamps. The polymer coated film was conditioned for 24 hours in a 
constant temperature testing room at 22.degree. C. and 50% relative 
humidity, after which a shear strength test was performed. A shear value 
of less than one minute was obtained. 
Examples 16 and 17 demonstrate that MMA incorporation into the midblock of 
a polymer prepared according to photoiniferter polymerization is much 
greater in the presence of accelerator compound as shown by the greater 
shear strength of the polymer prepared therewith. 
EXAMPLE 18 
Kinetic Studies Performed Using Varying Concentrations of Stannous 
2-ethylhexanoate Metal Compound Accelerator in the Polymerization of Butyl 
Acrylate 
In order to gain insight into the enhanced polymerization rate obtained 
using metal compound accelerators, kinetic studies were performed using 
varying amounts of stannous 2-ethylhexanoate metal compound accelerator 
during the polymerization of BA by use of a photoiniferter. The reaction 
components were charged into 8 separate 120 ml clear glass bottles which 
were purged with nitrogen for 10 minutes before sealing and placing the 
sealed bottle in a roller mechanism. Each rotating sealed bottle was 
exposed to ultraviolet radiation from six General Electric 15 watt black 
light lamps for 1 hour. The reaction components included 28 g of BA, 0.2 g 
XDC, 28g toluene and varying amounts of stannous 2-ethylhexanoate. 
The reaction can be represented by the following equation : 
##STR19## 
wherein X .TM.mole % of stannous 2-ethylhexanoate. Percent solid 
calculations were used to determine the percent conversion, the results of 
which are shown in FIG. 1. FIG. 1 clearly demonstrates that samples 
containing higher levels of stannous 2-ethylhexanoate metal compound 
accelerator (shown in mole % of the monomer BA) polymerize more 
efficiently than the control sample which contained no stannous 
2-ethylhexanoate. The most efficient polymerization occurred in the range 
of 2-3 mole % stannous 2-ethylhexanoate. Lower conversion values were 
observed for amounts much greater or much less than 2-3 mole% stannous 
2-ethylhexanoate when irradiated for shorter times. 
However, with longer irradiation times and conversions near completion 
(.about.85%) the reactivity difference between varying amounts of stannous 
2-ethylhexanoate was small except for at very low levels of stannous 
2-ethylhexanoate. The results of the experiment with respect to the long 
irradiation times are reported in Table IV below. 
TABLE IV 
______________________________________ 
Mole % Irradiation Time 
% Conversion 
______________________________________ 
0.0 1 hour 28 
0.1 1 hour 77 
0.5 1 hour 87 
1.0 1 hour 86 
2.0 1 hour 88 
3.0 1 hour 87 
4.0 1 hour 88 
6.0 1 hour 86 
10.0 1 hour 84 
______________________________________ 
It was observed that the use of 0.5-1 mole % stannous 2-ethylhexanoate 
resulted in approximately the same percent conversion as the use of higher 
percentages of stannous 2-ethylhexanoate. Thus, the use of 0.5-1 mole % of 
stannous 2-ethylhexanoate would be more economical. 
The low and high conversion kinetic studies suggest that the rate of 
acceleration of the photoiniferter reactions using stannous 
2-ethylhexanoate is probably due to several factors Although we do not 
wish to be limited to a particular mechamism, we believe that one of the 
roles of the accelerator stannous 2-ethylhexanoate may be that of oxygen 
scavenging. Oxygen is an inhibitor which combines with free radically 
polymerizable monomer thus hindering polymerization. This is the known 
role of stannous 2-ethylhexanoate in conventional photopolymerization 
reactions which is demonstrated by the lower induction time exhibited by 
such a reaction conducted with stannous 2-ethylhexanoate in FIG. 2, line D 
of Example 19. 
We believe that a second role of stannous 2-ethylhexanoate accelerator 
metal compound may be the complexing action of stannous 2-ethylhexanoate 
with the free radically polymerizable monomer. The higher percent 
conversion of butyl acrylate obtained with a higher percentage of stannous 
2-ethylhexanoate (0.1 mole vs. 0.5 mole and above, Table IV) may indicate 
such a complexation mechanism. 
We believe that a third role of stannous 2-ethylhexanoate metal compound 
accelerator may be the removal of the terminating radical 
##STR20## 
by stannous 2-ethylhexanoate. Stannous 2-ethylhexanoate may selectively 
remove the terminating radical 
##STR21## 
without reacting with the propagating polymer radical and thus enhance the 
polymerization reaction. This enhanced polymerization rate which occurs in 
the presence of stannous 2-ethylhexanoate is shown by the higher slope 
obtained when accelerator stannous 2-ethylhexanoate was used compared to a 
control reaction in which no stannous 2-ethylhexanoate was used. See FIG. 
1, lines B and A, respectively. 
This higher rate suggests that the acceleration of the photoiniferter 
reaction by stannous 2-ethylhexanoate is due to more than oxygen 
scavenging. The effect of stannous 2-ethylhexanoate in conventional 
photopolymerization is principally reduction of oxygen inhibition as shown 
in FIG. 2, line E. 
Although I do not wish to be limited to any particular mechanism I theorize 
that the metal compound accelerator used to accelerate the free radical 
polymerization remains in its initial form intermixed within the polymer 
or copolymer system formed by the accelerated method. It is possible that 
a minor portion of the metal compound accelerator may become incorporated 
into the polymer or copolymer produced thereby. It is also possible that a 
minor portion of the metal compound accelerator may become involved in 
side reactions involving H.sub.2 O, O.sub.2, etc. 
EXAMPLE 19 
Effect of Stannous 2-ethylhexanoate on the Polymerization of Butyl Acrylate 
Using a Conventional Initiator 
The effect of stannous 2-ethylhexanoate on the polymerization of butyl 
acrylate with conventional initiator Irgacure 651 (2,2-dimethoxy-2-phenyl 
acetophenone), available from Ciba-Geigy according to the procedure of 
Example 6 was studied. The reaction components are listed below. 
______________________________________ 
Irgacure Tolu- 
Plot BA + 651 + ene + 2-ethylhexanoate 
______________________________________ 
D 26.6 g 0.1 g 43 g 1.6 g 
E 26.6 g 0.1 g 43 g 0 
______________________________________ 
The results are plotted as lines D and E in FIG. 2. The data does not 
indicate any rate enhancement besides the decreased induction period in 
the presence of stannous 2-ethylhexanoate. The slope of each plot is the 
same which is indicative of the same reaction rate. 
EXAMPLE 20 
Synthesis of Siloxane lniferter Compound 
A. Synthesis of 1-(dimethylchlorosilyl)-2-(p,m-chloromethyl-phenyl)ethane 
(1): 
Into a 100 ml flask were charged 10g of 1-(dimethylchlorosily)-2-(p,m 
chloro-methylphenyl)ethane and 50 g of H.sub.2 O. The mixture was stirred 
at room temperature for 4 hours. Next, 50 ml of ether was added to the 
flask and the flask contents were stirred for 15 minutes. The flask 
contents were then transferred to a separatory funnel. The ether layer was 
separated out and washed with 50 ml of H.sub.2 O each four times. The 
ether layer was dried over anhydrous MgSO.sub.4, filtered and rotary 
evaporated out to remove the solvent. A viscous colorless liquid was 
obtained. 
B. Synthesis of 
##STR22## 
Into a 250 ml three necked flask fitted with a magnetic stirrer, condenser, 
thermometer and nitrogen in/outlet were charged compound (1) from Step A 
(6.05 g), D.sub.4 (61 g) and Darco 60 carbon black (6.7 g). After stirring 
the mixture for 10 minutes, H.sub.2 SO.sub.4 (0.34 g) was added. The 
mixture was heated at 90.degree. C. for 6 hours while the system was kept 
under nitrogen atmosphere. The mixture was then filtered The viscous 
liquid was placed in a vacuum oven at 90.degree. C. overnight. 
C. Synthesis of 
##STR23## 
Into a 100 ml flask were charged compound (2) (10.2 g) from Step B, 1.2 g 
of 
##STR24## 
and 20 g of THF. The mixture was stirred overnight at room temperature. A 
solid precipitate of NaCl was formed. The reaction mixture was filtered 
and the THF was rotary evaporated out at 50.degree. C. A viscous clear 
liquid was obtained. Hexane (50 g) was added to the liquid. The hexane 
layer was washed 5 times with water. The hexane layer was dried over 
anhydrous MgSO.sub.4, filtered and dried by rotary evaporation. A viscous 
liquid was obtained for which .sup.1 H NMR and IR spectroscopy revealed 
the formation of compound (3). GPC analysis revealed Mn=7,674 and 
.rho.=3.1 
EXAMPLE 21 
Differential Photocalorimetry Studies Comparing The Rate of Reaction In The 
Presence And In The Absence of Stannous 2-ethylhexanoate 
(i) Reaction of BA with XDC in the Presence of Stannous 2-ethylhexanoate: 
Into a 10 ml volume vial was charged 5 g BA, 0.0286 g XDC and 0.3 g (2 mole 
%) stannous 2-ethylhexanoate. The vial was then sealed and shaken to mix 
the vial contents in order to form a solution. Into a circular pan having 
a diameter of 6.6 mm and a depth of 1.6 mm pan, was charged 14.4 mg of the 
above solution. The pan was placed in the photocell chamber of a 
Differential Photocalorimetor (model #930, DuPont). The cell was kept 
under nitrogen atmosphere and the sample was irradiated by a high pressure 
mercury 200 Watt arc lamp for 2 minutes. The observed enthalpy was 241.9 
J/g. 
(ii) Reaction of BA with XDC: 
A solution was made by mixing 5 g BA and 0.0286 g XDC according to the 
procedure of Example 21(i). A 13.6 mg sample of the solution was 
irradiated for 2 minutes as in Example 21(i). An enthalpy of 34.5 J/g was 
observed. Thus, Examples 21(i) and Example 21(ii) demonstrated that the 
photoiniferter polymerization of BA in the presence of stannous 
2-ethylhexanoate occurred seven times faster than in the absence of 
stannous 2-ethylhexanoate. 
(iii) Reaction of MMA with XDC in the Presence of Stannous 
2-ethylhexanoate: 
Following the procedure described in Example 21(i), a solution was prepared 
by mixing 10 g of MMA, 0.06 g of XDC and 0.6 g of stannous 
2-ethylhexanoate. A 10.0 mg sample of the above solution was irradiated 
for 2 minutes as described in Example 21(i). An enthalpy of 23.6 J/g was 
observed. 
(iv) Reaction of MMA with XDC: 
Following the procedure described in Example 21(i), a solution of 10 g MMA 
and 0.06 g XDC was prepared and a 13.9 mg sample was irradiated for 2 
minutes as in Example 1. No heat of evolution was observed indicating that 
no reaction occurred. 
(v) Reaction of Siloxane Iniferter with BA in the Presence of Stannous 
2-ethylhexanoate: 
Following the procedure described in Example 11(i) a solution of 0.27 g 
siloxane iniferter from Example 20 (m.w. .TM.7,674) of the formula 
##STR25## 
0.4 g BA and 0.02 g (1.58 mole %) stannous 2-ethylhexanoate was prepared. 
A 13.1 mg sample was irradiated following the procedure described in 
Example 21(i). An enthalpy of 133.6 J/g was observed. 
(vi) Reaction of Siloxane Iniferter with BA: 
A solution of 0.2 g siloxane iniferter from Example 20 and 0.4 g BA was 
prepared. A 10.8 mg sample of the solution was irradiated as in Example 
21(i). An enthalpy of 44.0 J/g was observed. Thus, the reaction of the 
siloxane iniferter with BA in the presence of stannous 2-ethylhexanoate 
was three times faster than the siloxane iniferter reaction with BA in the 
absence of stannous 2-ethylhexanoate. 
(vii) Reaction of Siloxane Iniferter with MMA in the Presence of Stannous 
2-ethylhexanoate: 
A solution of 0.27 g siloxane iniferter from Example 20, 0.8 g MMA, and 
0.065 g (2 mole %) stannous 2-ethylhexanoate was prepared according to the 
procedure of Example 21(i). A 14.1 mg portion of this sample was 
irradiated following the procedure described in Example 21(i). An enthalpy 
of 31.4 J/g was observed. 
(viii) Reaction of Siloxane Iniferter with MMA: 
A solution of 0.1 g of siloxane iniferter from Example 20 and 0.3 g MMA was 
prepared. A 12.2 mg sample of the solution was irradiated according to the 
procedure of Example 21(i). An enthalpy of 10.5 J/g was observed. 
Since the rate of reaction is directly proportional to the rate of heat 
evolution (i.e., enthalpy) Example 21 thus demonstrates that for 
photoiniferter reactions whether monoiniferters or macroiniferters are 
used, the rate of polymerization are much greater in the presence of the 
metal compound accelerator than in absence of the metal compound 
accelerator. 
While this invention has been described in connection with specific 
embodiments, it should be understood that it is capable of further 
modification. The claims herein are intended to cover those variations 
which one skilled in the art would recognize as the chemical equivalent of 
what has been described here.