Random monoalkenyl arene-conjugated diene copolymers are produced by controlling the continuous rate of addition of the conjugated diene monomer to a reactor containing the monoalkenyl arene monomer, organolithium initiator and solvent, the rate being adjusted in response to the photometer measured presence of an active chromophore comprising a lithium ion directly associated with a poly(monoalkenyl arene) carbanion.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a process for preparing a random monoalkenyl 
arene-conjugated diene copolymer. More particularly, the invention relates 
to a process for preparing an anionic random monoalkenyl arene-conjugated 
diene copolymer employing a photometer to control the rate of addition of 
the conjugated diene monomer. 
2. Description of the Prior Art 
The copolymerization of conjugated dienes and styrene has been widely 
utilized for some time. The most commonly used process for the 
copolymerization has been by an emulsion technique utilizing a free 
radical catalyst such as an organic peroxide or hydroperoxide. More 
recently, styrene-diene random copolymers have been prepared by the 
solution polymerization of styrene and a conjugated diene with 
organolithium initiators. 
With regard to such lithium initiation, it is known that in the batchwise 
copolymerization, the diene monomer polymerizes considerably faster than 
the styrene monomer. As a result of this, if no special measures are 
taken, tapered block copolymers are formed (see e.g. U.K. Pat. No. 
888,624). 
Several attempts have already been made to counteract this block formation 
and to promote the formation of copolymers of which the monomer units are 
distributed more statistically over the polymer molecule. For instance, a 
process has been proposed in which the two monomers are added at a rate 
lower than the normal polymerization rate of the system under the 
conditions applied (U.S. Pat. No. 3,094,512), which means that the 
monomers are added in such a way that a complete reaction takes place 
while the addition is going on. This implies that, if application of a 
relatively low polymerization temperature, for instance, below 110.degree. 
C., is desired, the monomers should be added very slowly and in accurately 
determined quantities, as a result of which the process is time-consuming 
and the polymer yield per unit of time small. 
By polymerization at higher temperatures the monomer addition can indeed be 
made to proceed faster, but then thermal decomposition of the initiator 
may take place at an unacceptable rate. In addition the harmful influence 
of the higher temperature on the polymer formed is greater. Moreover, when 
styrene is applied as the vinylaromatic compound, a high polymerization 
temperature is undesirable in view of the risk of thermal 
homopolymerization of the monomer by free radicals. These objections and 
risks carry weight at temperatures higher than 90.degree. C. and can 
particularly become inconvenient at temperatures higher than 150.degree. 
C. 
In the last-mentioned process invariably only one preselected monomer ratio 
is employed, namely, that at which the monomers are added. The monomer 
ratio at which the copolymerization starts is equal to this ratio. 
Another process for the preparation of statistical copolymers is disclosed 
in U.K. Pat. No. 994,726. In that patent, random copolymers are prepared 
by first forming a mixture of a portion of the butadiene monomer and all 
of the styrene monomer in a ratio selected to give the desired copolymer 
content. Then the mixture is contacted with a lithium-based catalyst under 
polymerization conditions. Incremental additions of butadiene monomer are 
added to maintain the monomer ratio. Again, in this process only one 
preselected monomer ratio is applied. As during the copolymerization, 
since no vinylaromatic compound is added, per unit of time a decreasing 
amount of diene should be supplied. As a result not only the 
concentration, but also the absolute quantity of each of the monomers 
present in the reactor steadily decreases. Consequently, though the 
monomer ratio is kept constant, the monomer concentration, which as a rule 
is fairly high initially, decreases to a value which is rather low at the 
end of the copolymerization. It is not easy to control this process since 
the butadiene is added in discrete, incremental amounts pursuant to 
pre-selected addition rates. If the calculations are wrong or if 
conditions change in the reactor, then the resulting polymer will not be 
statistically random. 
Still another copolymerization process is disclosed in U.K. Pat. No. 
1,283,327. In that patent both monomers are added continuously to the 
reactor. The rate of addition of monomer is pre-set at the rate required 
to maintain the specific concentration of monomers. To maintain a constant 
copolymer ratio (the definition of a random copolymer) the monomer ratio 
in the reactor must be constant and will be completely different from the 
ratio in the polymer. The flow of monomer to the reactor must equal the 
disappearance of monomer by polymerization. The resulting polymer will 
become non-random or tapered if the precalculated monomer supply rate is 
incorrect, if the initial monomer concentration is incorrect, or if the 
initial monomer ratio is incorrect. For example, if the desired ratio of 
styrene to isoprene in a polymer is 11:1, preparation of such a polymer by 
the process of U.K. Pat. No. 1,283,327 would require a monomer ratio of 
styrene to isoprene of greater than 140:1 due to the extremely high 
reactivity of isoprene monomer in this system. Precisely maintaining such 
a monomer ratio is impractical. Another consideration is the extent of 
thermal termination or dieout of the active polymer chains. 
Another approach to making random styrene-diene copolymers is to add a 
randomizing agent to solution mixtures of diene, styrene and organolithium 
initiators. Various randomizing agents are disclosed in U.S. Pat. Nos. 
2,975,160; 3,366,611; 3,496,154; 3,498,960 and 3,673,166. These strong 
randomizing agents are typically employed at fairly high levels of 
addition in order to equalize the diene monomer and styrene monomer 
reaction rate constants. However, this technique is not always acceptable 
because altering the polarity of the solvent to the extent of equalizing 
the rate constants would necessarily result in an unacceptably large 
change in the microstructure of the diene polymer units. For example, a 
significant increase in the 3,4 content of isoprene polymer units might 
result. 
A new polymerization process has now been found that overcomes many of the 
difficulties found in the prior art. 
SUMMARY OF THE INVENTION 
The present invention is directed to a much improved process for preparing 
statistically random monoalkenyl arene-conjugated diene copolymers. 
Further, the present invention may be used to prepare random copolymer 
blocks as part of a multiblock copolymer. In a specific embodiment the 
present invention is an improvement in the process for preparing anionic 
random copolymers, which process comprises: 
(a) adding a monoalkenyl arene monomer, minor portion of a conjugated diene 
monomer and an inert solvent to a reactor; 
(b) adding a polymerizing amount of an organolithium initiator to the 
resulting solution, therein commencing the polymerization of said 
monoalkenyl arene monomer; and 
(c) continuously adding a conjugated diene monomer to the solution of step 
(b); 
the improvement comprising controlling the rate of addition of said 
conjugated diene monomer in step (c) in response to the photometer 
measured relative presence of an active chromophore comprising a lithium 
ion directly associated with a poly(monoalkenyl arene) carbanion wherein 
the desired relative presence has been previously determined to give a 
desired ratio of monoalkenyl arene monomer units to conjugated diene 
monomer units in said copolymer. 
As expressed in an alternative embodiment, the present invention is an 
improvement in the process for preparing anionic random copolymers, which 
process comprises: 
(a) adding a monoalkenyl arene monomer, minor portion of a conjugated diene 
monomer and an inert solvent to a reactor; 
(b) adding a polymerizing amount of an organolithium initiator to the 
resulting solution, therein commencing the polymerization of said 
monoalkenyl arene monomer; and 
(c) continuously adding a conjugated diene monomer to the solution of step 
(b); 
the improvement comprising: 
(i) continuously sampling the solution of step (c) and determining, by use 
of a photometer, the relative concentration of active chromophores, said 
active chromophores comprising a lithium ion directly associated with a 
poly(monoalkenyl arene) carbanion; 
(ii) producing a first signal representative of said concentration; 
(iii) comparing said first signal to a predetermined level representative 
of the desired chromophore concentration to obtain a first control signal, 
the magnitude of which is related to the difference between said first 
signal and said predetermined level; and 
(iv) adjusting the flow rate of said conjugated diene monomer to said 
reactor responsive to the magnitude of said control signal until the 
desired level of said concentration is obtained. 
The process of the present invention has many advantages over the prior art 
processes. For one, the process avoids the necessity for large amounts of 
strong randomizing agents which would otherwise result in a significantly 
modified diene microstructure by reducing the 1,4 addition. Further, the 
present invention results in a reduced reaction time (e.g., 11/2 to 3 
hours) compared to, for example, the process of U.K. Pat. No. 1,283,327. 
Since all of the monoalkenyl arene monomer is in the starting mixture, the 
reaction rate is very fast, particularly during the first part of the 
reaction. Another advantage of the present invention is that there is low 
thermal dieout of living polymer chains since low temperatures 
(45.degree.-50.degree. C.) may be utilized with the short reaction times. 
Still another advantage for the present process is that there is no need 
to maintain constant reactor temperature or constant initiator 
concentration in order to insure that a completely random copolymer is 
obtained. By monitoring the chromophore concentration it is possible to 
automatically make the necessary adjustments that are required as 
temperature and initiator concentration change. The resulting polymer has 
a more statistically random structure (without a modified microstructure 
for the diene component) than have polymers prepared according to other 
processes. Further, the process of the present invention is more forgiving 
and controllable than the prior art processes. 
DETAILED DESCRIPTION OF THE INVENTION 
The monoalkenyl arene monomers employed herein include styrene, alphamethyl 
styrene, tertbutyl styrene, paramethyl styrene and other ring alkylated 
styrenes as well as mixtures of the same. The much preferred monoalkenyl 
arene is styrene. 
The conjugated dienes include specifically 1,3 butadiene, piperylene, and 
isoprene, with butadiene and isoprene being preferred. 
The relative amounts of monoalkenyl arene and diene in the resulting 
polymers is between about 1% by weight and 80% by weight diene, preferably 
about 2% to about 50% by weight diene. 
The polymers of the present invention are produced by anionic 
polymerization employing an organomonolithium initiator. The first step of 
the process involves contacting the monoalkenyl arene, diene and the 
organomonolithium compound (initiator) in the presence of an inert 
diluent. The inert diluent may be an aromatic or naphthenic hydrocarbon, 
e.g., benzene or cyclohexane, which may be modified by the presence of an 
alkene or alkane such as pentenes or pentanes. Specific examples of 
suitable diluents include n-pentane, n-hexane, isooctane, cyclohexane, 
toluene, benzene, xylene and the like. The organomonolithium compounds 
(initiators) that are reacted with the polymerizable additive in step one 
of this invention are represented by the formula RLi; wherein R is an 
aliphatic, cycloaliphatic, or aromatic radical, or combinations thereof, 
preferably containing from 2 to 20 carbon atoms per molecule. Exemplary of 
these organomonolithium compounds are ethyllithium, n-propyllithium, 
isopropyllithium, n-butyllithium, sec-butyllithium, tertoctyllithium, 
n-decyllithium, n-eicosyllithium, phenyllithium, 2-naphthyllithium, 
4-butylphenyllithium, 4-tolyllithium, 4-phenylbutyllithium, 
cyclohexyllithium, 3,5-di-n-hepthylcyclohexyllithium, 
4-cyclopentylbutyllithium, and the like. The alkyllithium compounds are 
preferred for employment according to this invention, especially those 
wherein the alkyl group contains from to 3 to 10 carbon atoms. A much 
preferred initiator is sec-butyllithium. See U.S. Pat. No. 3,231,635. The 
concentration of the initiator can be regulated to control molecular 
weight. Generally, the initiator concentration is in the range of about 
0.25 to 50 millimoles per 100 grams of monomer although both higher and 
lower initiator levels can be used if desired. The required initiator 
level frequently depends upon the solubility of the initiator in the 
hydrocarbon diluent. These polymerization reactions are usually carried 
out at a temperature in the range of -60.degree. to +300.degree. F. and at 
pressures which are sufficient to maintain the reaction mixture in the 
liquid phase. 
In the first step of the present process, a minor portion of the conjugated 
diene monomer is added with the entire amount of monoalkenyl arene and the 
inert solvent. This minor amount is less than 10% weight of the total 
amount of diene in the random copolymer, preferably about 5 to about 10% 
by weight of the total amount of diene. This diene is added initially in 
order to avoid making homopolystyrene while diene flow commences and 
enters the reactor. 
In the next step, the remaining portion of the conjugated diene monomer is 
continuously added at a specified rate. This rate is in response to the 
photometer measured relative presence of an active chromophore comprising 
a lithium ion directly associated with a poly(monoalkenyl arene) carbanion 
wherein the desired relative presence of said chromophore has been 
previously determined to give a desired ratio of monoalkenyl arene monomer 
units to conjugated diene monomer units in said copolymer. There are a 
number of key aspects to this step of the process. The method and 
apparatus for measuring the presence of the chromophore is discussed in 
U.S. Pat. No. 3,743,629, which disclosure is herein incorporated by 
reference. 
According to the '629 patent, the use of the photometer results in a rapid, 
continuous, and direct indication of the active chain concentration in an 
active cement comprising living polymers of a lithium ion directly 
associated with a monoalkenyl arene polymer. This is provided by comparing 
the absorbance of one narrow band width wavelength of transmitted 
radiation by an active portion of the cement with the absorbance of a 
second narrow band with wavelength of transmitted radiation by the same 
active portion of the cement. This comparison is accomplished using two 
narrow band wavelengths of radiation in a single cell photometer. This 
procedure is applicable to reaction admixtures which, in the active state 
during polymerization, have quantitatively measurable absorbance 
characteristics (attributable to the living chain ends) for a first 
predetermined wavelength of radiation which are different from those of 
the same cement at the same stage of polymerization for a second 
quantitatively measurable predetermined wavelength of radiation. The 
procedure is particularly desirable where the background interference is 
small in comparison with the absorbance of the active chromophore which is 
associated with the living chain ends. 
The indication of the active chain concentration in the polymerization zone 
may be recorded for visual observation, such as, for example, on a moving 
graph. In the present invention, the indication of the active chain 
concentration is converted into a suitable signal which is transmitted 
through known control devices to regulate or adjust the rate of continuous 
addition of the conjugated diene monomer as more fully explained below. If 
desired, both a visual indication, in the form of a moving graph or other 
means, and automatic regulation of the diene addition may be provided. 
A calibration curve is conveniently established by plotting the net 
photometer readings obtained for the differential absorbance of 
transmitted radiation against values obtained for the same active cements 
by known analytic procedures, such as for example, tritium-counting. This 
analytic procedure is described in the Journal of Polymer Science, part A, 
vol. 3, pp. 2243-2257 (1965), "Alkyl-Free Cobalt Catalyst for the 
Stereospecific Polymerization of Butadiene"; J. G. Balas et al. Using such 
a calibration curve it is possible to obtain a direct indication of the 
active chain concentration in an active cement. 
According to the '629 patent, a homogeneous solution polymerization 
reaction admixture is established in a reaction zone according to known 
procedures and using a lithium-based initiator for polymerization of vinyl 
arene-containing polymers wherein at least one vinyl arene unit is 
directly associated with a lithium ion to form "living polymer." A 
representative sample of the reaction mixture is withdrawn from the 
reaction zone. Preferably the sample is withdrawn from the reaction zone. 
Preferably the sample is withdrawn continously and at a high flow rate. At 
least a portion of the sample is passed through a measuring cell in a 
single cell photometer. A beam of transmitted radiation is passed through 
the sample containing measuring cell, after which it is split into two 
beams having different optical characteristics. The measuring wavelength 
is chosen from those strongly absorbed by the chromophore which is 
associated with the living chain ends, and the reference wavelength is 
chosen so that the active cement absorbs the radiation very weakly, or not 
at all. The differential absorbance of the radiation passed through the 
measuring cell is obtained by impinging the two beams on separate 
phototubes and comparing the output from the two phototubes. In the 
present invention, the output from the phototubes is amplified and 
recorded and is used to activate means for regulating the diene addition 
rate into the polymerization zone. 
The wavelengths of transmitted radiation which are employed in the 
photometer are selected so that there will be a minimum of interference 
from chromophores other than that which it is desired to detect. In 
general the selected wavelengths for both the reference and sample 
measuring beams are within the ultraviolet and visible range of from about 
1,800 to 7,000 angstroms. When desired, wavelengths from the infrared 
range of from about 7,000 to 14,000 angstroms may be used where active 
chromophores are present for this infrared range. Preferably the selected 
wavelength for both beams are as close to one another as possible and are 
in the visible and near visible range of from about 3,000 to 6,000 
angstroms. 
Part of the present invention involves determining the desired relative 
presence of the chromophore. This may be done by rigid calculation and 
knowledge of the kinetics involved. However, it is preferred to employ an 
empirical (trial and error) method to determine the desired relative 
chromophore presence. This empirical method involves first selecting a 
level based on previous experience. The higher the diene level of the 
polymer, the lower the photometer reading, and vice-versa. Then it is 
necessary to run some trials (usually two are sufficient) and measure the 
diene content of the polymer. Finally, the photometer target level is 
readjusted based on gas chromotography (GC) analyses of diene and arene. 
An important consideration is to maintain a constant relative 
disappearance of monomers at the target polymer content level throughout 
the reaction, resulting in simultaneous depletion of both monomers. 
In a specific example (Illustrative Embodiment I), a polymer block having a 
monomer ratio of styrene to isoprene of 11 to 1 was desired (92% weight 
styrene). The desired absorbance value was determined as follows: 
1. Through previous experience involving empirical trial runs, it was 
determined that about 2.3% of the active chromophores must be SLi active 
chromophores. 
2. The known amount of lithium initiator required for the desired molecular 
weight and quantity of polymer was 483 ppm (parts per million expressed as 
butyllithium). Therefore, the desired concentration of styryllithium 
chromophores was 483.times.0.023 or 11.1 ppm. 
3. Next it is necessary to choose a unit for sensitivity on the photometer. 
For purposes herein, a unit of one (1) was selected. Accordingly, for 
purposes herein the desired setting was 11.1 ppm styrlyllithium per unit. 
From historical information it was known that the absorbance per ppm 
styryllithium was 0.00466 abs/ppm. Accordingly, the absorbance per unit 
value was 11.1 ppm/unit.times.0.00466 abs/ppm=0.0517 abs/unit. 
4. Next it was necessary to set the colorimeter sensitivity. The calibrated 
filter employed in Illustrative Embodiment I had a rated absorbance of 
0.843. Accordingly, the colorimeter sensitivity was 0.843 divided by 
0.0517 or 16.3 units (with the filter in the light path). In order to set 
the colorimeter sensitivity, the Kodak glass filter was placed in the 
light path. Then the instrument sensitivity was adjusted until the 
precalculated value of 16.3 colorimeter units was set. The sensitivity was 
then locked in. 
5. The technician controls the addition rate of the diene by monitoring the 
colorimeter setting. The net reading (gross minus base) is controlled to 
1.0 units (equivalent to 11.1 ppm styryllithium). If the reading drops 
below 1.0 net unit, there is too much diene being added and the technician 
cuts back on the diene addition rate. Specifically, the magnitude of the 
diene addition rate is controlled in response to the magnitude of the 
difference between the measured level of chromophore concentration and the 
desired level of chromophore concentration. In other words, the diene 
addition rate is decreased if the colorimeter reading decreases below the 
selected level and is increased if the colorimeter reading increases above 
the selected level. The response in the reactor is quite rapid. 
If desired, a small amount of a randomizing agent may be added at about the 
same time (or earlier than) the lithium initiator is added. The amount 
added should be low enough not to effect microstructure. The randomizer, 
however, is not essential in the present invention. Examples of various 
randomizers are given in the various patents cited in the Description of 
the Prior Art. Specific examples of randomizers are polar compounds 
including dimethyl ether, diethyl ether, ethyl methyl ether, ethyl propyl 
ether, di-n-propyl ether, di-n-octyl ether, dibenzyl ether, diphenyl 
ether, anisole, tetramethylene oxide (tetrahydrofuran), 
1,2-di-methoxyethane, dioxane, paraldehyde, dimethyl sulfide, diethyl 
sulfide, di-n-propylsulfide, di-n-butyl sulfide, methyl ethyl sulfide, 
dimethylethylamine, tri-n-propylamine, tri-n-butylamine, trimethylamine, 
triethylamine, N,N-dimethylamine, pyridine, quinoline, N-ethylpiperidine, 
N-methyl-N-ethylaniline, N-methylmorpholine, and the like. It is to be 
understood also that mixture of polar compounds can be employed in the 
practice of the instant invention. Preferred randomizers include 
orthodimethoxybenzene and triethylorthoacetate. 
As discussed earlier the present invention may be used to make an excellent 
random monoalkenyl arene-diene copolymer per se or it may be used to form 
the first "block" in a multiblock copolymer. Such multiblock copolymers 
can be formed by adding additional conjugated diene monomer after all the 
monoalkenyl arene monomer has been polymerized (depleted). The result is 
an end block A comprising a random monoalkenyl arene-conjugated diene 
polymer block and a conjugated diene homopolymer block B. If desired the 
living ABLi copolymer may be coupled by known coupling techniques to form 
an (AB).sub.x BA multiblock copolymer. The letter x, which refers to the 
number of arms may be 1 or more, preferably 1 to about 10.

The invention is further illustrated by means of the following illustrative 
embodiments, which are given for the purpose of illustration only and are 
not meant to limit the invention to the particular reactants and amounts 
disclosed. 
Illustrative Embodiment I 
In Illustrative Embodiment I, a radial (AB).sub.x BA block copolymer was 
prepared. The A block was a random styrene-isoprene copolymer having a 
styrene content of 92 weight percent. The B block was an isoprene 
homopolymer block. In this example, 89.53 pounds of cyclohexane, 15.8 
pounds of styrene and 40 grams of isoprene were charged to the reactor. 
Also added to the reactor was 2.2 milliliters (mls) orthdimethoxybenzene 
(ODMB), making the concentration 50 ppm. Then 472 mls of an 8% solution of 
sec-butyllithium in cyclohexane (0.08 grams butylithium per milliliter 
cyclohexane) was added. The remainder of the isoprene (659 grams) needed 
for the A block was added continuously over a thirty three minute period 
in response to the continuous photometer reading. An extensive series of 
GC (gas chromotography) analyses were taken during the run. The various 
conditions and results are presented below in Table I: 
TABLE I 
__________________________________________________________________________ 
GC 
Colorimeter 
Total Iso- % 
Time Temp 
Reading 
prene added 
% Isoprene 
Minutes 
.degree.C. 
Gross Grams Styrene 
Isoprene + Styrene 
__________________________________________________________________________ 
0 46.4 
10 40 12.9 0.015 
2 49.9 
12 230 12.2 1.34 
4 48.5 
13 300 9.5 1.28 
7 44.8 
12.5 367 7.8 0.77 
20 45.0 
11 620 4.1 0.85 
33 43 11 699 1.91 1.19 
__________________________________________________________________________ 
The desired gross reading on the colorimeter was 11.1. From 2 minutes to 33 
minutes in the run, corresponding to 5% to 85% of total styrene 
conversion, the percent isoprene monomer in the reaction mixture was 
maintained at from about 0.8% to about 1.3% of total monomer. Meanwhile, 
the colorimeter indicated the presence of 1.2 to 3.8% of S.sup.- Li+ chain 
ends. 
Next, 46.1 pounds of isoprene and 201.3 pounds cyclohexane (previously 
titrated with 32 mls butylithium solution to remove impurities) was added 
to the reactor, therein forming the B blocks. After the isoprene monomer 
was reacted, 354 grams of 55% w pure divinylbenzene coupling agent was 
added. The reaction mixture was then held at 60.degree. C. for about 30 
minutes. After termination of any active sites by the addition of 
2-ethylhexanol and after addition of a phenolic antioxidant, the radial 
(AB).sub.x BA block copolymer was stream coagulated and dried. 
During the run samples were withdrawn at periodic intervals and analyzed by 
gas chromotography (GC). From these values a percent styrene conversion 
was calculated. From a smoothed-out rate plot, the number of pounds of 
styrene reacted were calculated. The calculation for pounds of isoprene 
reacted was similar, except that the amount of isoprene added to the 
reactor had to be taken into account. The various results are presented in 
Table 2 along with a calculated percentage of active polymer as SLi. In 
Table 3, the pounds of styrene and isoprene reacted over the various time 
intervals are presented and a percentage of styrene in the polymer was 
calculated. The results are extraordinary, and reveal the excellent 
control obtained by use of the present invention. 
TABLE 2 
__________________________________________________________________________ 
Styrene Isoprene 
GC, % Total 
GC, % Calculated 
Time Total 
% Lbs Lbs Total 
Lbs Lbs % Active Polymer 
Minutes 
Charge 
Converted 
Reacted 
Added 
Charge 
Remaining 
Reacted 
as SLi 
__________________________________________________________________________ 
0 12.9 
-- -- 0.88 
0.002 
-- -- -- 
2 12.2 
12.9 1.87 0.51 
0.166 
0.27 0.24 2.5 
4 9.5 32.1 4.65 0.66 
0.123 
0.19 0.47 3.8 
7 7.8 44.3 6.42 0.81 
0.061 
0.10 0.71 3.1 
20 4.1 70.7 10.24 
1.37 
0.035 
0.06 1.31 1.2 
33 1.91 
86.4 12.51 
1.54 
0.023 
0.04 1.50 1.2 
__________________________________________________________________________ 
TABLE 3 
______________________________________ 
Lbs Lbs Lbs 
Time Styrene Isoprene Monomer % Styrene 
Interval (min) 
Reacted Reacted Reacted in Polymer 
______________________________________ 
0-2 1.87 0.24 2.11 88.4 
2-4 2.78 0.23 3.01 92.5 
4-7 1.77 0.24 2.01 88.0 
7-20 3.82 0.60 4.42 86.4 
20-33 2.27 0.19 2.46 92.3 
______________________________________ 
Illustrative Embodiment II 
A similar polymer to that of Illustrative Embodiment I was prepared in this 
example. The only major change in the process was that there was no 
addition of orthodimethoxybenzene randomizer. In Illustrative Embodiment 
II 110 pounds of cyclohexane, ten pounds of styrene and 40 grams of 
isoprene were added to the reaction along with 400 mls butylithium 
solution. The reactor was held at about 50.degree. C. and the additional 
isoprene (414 grams) was added continuously in response to the colorimeter 
readings. After the polymerization was complete, an additional 182.6 
pounds cyclohexane and 35.9 pounds isoprene (titrated with 35 mls 
butyllithium) were added, therein forming the B blocks. After 
polymerization was completed, the polymer arms were coupled with 253 grams 
divinyl benzene. After coupling was complete, the solution was terminated 
with methanol and the radial polymer was stream coagulated and dried. 
As with Illustrative Embodiment I, various samples were withdrawn from the 
reactor at various intervals and analyzed by GC analysis. The results are 
presented below in Tables 4 and 5. 
As shown in Table 4, the target range for the percentage of SLi chains was 
substantially higher than that in Illustrative Embodiment II. The reason 
for this is that in Illustrative Embodiment II, there is no additional 
randomizing agent. Accordingly, it has been shown through experience that 
a greater percentage of styryllithium is required. 
The polymer produced herein had an A block molecular weight of 11,500 and 
an AB two block molecular weight of 72,700. After coupling, the polymer 
had a peak molecular weight of about 540,000. Coupling efficiency was 
96.8% and the homopolystyrene content was only 0.3% w. The very low 
homopolystyrene content is significant in that it shows very good control 
and the lack of significant amounts of thermal die out. 
TABLE 4 
__________________________________________________________________________ 
Styrene Isoprene 
GC % Lbs Lbs GC Lbs Calculated 
Time/Min. 
% Converted 
Reacted 
Added 
% Reacted 
% SLi 
__________________________________________________________________________ 
0 6.76 
0 0 0.11 
.017 
.09 
15 2.98 
55.9 5.6 0.45 
.002 
.44 12 
20 2.57 
61.2 6.2 0.57 
.018 
.55 10 
35 1.68 
75.1 7.5 0.72 
.001 
.72 17 
50 1.16 
82.8 8.3 0.80 
.001 
.80 .about.17 
60 0.77 
88.6 8.9 0.85 
.002 
.84 14 
75 0.52 
92.3 9.2 0.91 
.001 
.91 13 
97 .about.100 
.about.10 
0.99 .99 9.5 
__________________________________________________________________________ 
TABLE 5 
______________________________________ 
Lbs Lbs Lbs 
Time Styrene Isoprene Monomer % Styrene 
Interval (min) 
Reacted Reacted Reacted in Polymer 
______________________________________ 
0-15 5.6 0.44 6.04 93 
15-20 0.6 0.11 0.71 85 
20-35 1.3 0.17 1.47 88 
35-50 0.8 0.08 .88 91 
50-60 0.6 0.04 .64 94 
60-75 0.3 0.07 .37 81 
75-97 .about.0.8 
0.08 .88 91 
TOTAL 10.0 0.99 11 91 
______________________________________