Process for making silyl endblocked organic polymers

A process for making silyl endblocked organic polymers of the formula R.sup.1.sub.3 SiM is disclosed which comprises contacting under anhydrous conditions M' monomers and/or oligomers of M' with a silyl cation R.sup.1.sub.3 Si.sup.+ devoid of any siloxane bonds wherein each R.sup.1 independently denotes an optionally substituted hydrocarbon or hydrocarbonoxy group, hydrogen, a halogen or a monovalent siloxane-free silicon-containing group and M is an organic polymer made by the addition polymerisation of ethylenically unsaturated monomers M' of the formula H(R.sup.3)--C.dbd.C--(R.sup.2).sub.2 wherein each R.sup.2 independently denotes an optionally substituted hydrocarbon, hydrogen or a halogen and R.sup.3 denotes a hydrogen or methyl group. Preferably the monomer M' is an olefin.

This invention relates to a process for making silyl endblocked organic 
polymers and more particularly to a process for making silyl endblocked 
polyolefins. 
Silyl endblocked organic polymers are organic polymers having a 
silicon-containing group at the end of the polymer chain linked via a 
Si--C bond. Silyl endblocked organic polymers are known and prior art 
methods for their preparation usually involve the reaction of a pre-formed 
polymer with a silicon-containing compound. 
For example, in U.S. Pat. No. 4,758,631 a method of preparing 
allyl-terminated polyisobutylene polymer is described which comprises 
allylation of tertiary chloro-capped polyisobutylene with 
allyltrimethylsilane in the presence of a Friedel-Crafts Lewis Acid. 
Derwent abstract of JP 04154816 describes the reaction of an isobutylene 
polymer having branched terminal alkyl groups with an organo-silicon 
chloride complex to form isobutylene polymers containing silyl groups at 
the end. Derwent abstract of JP 08100028 discloses the manufacture of 
isobutylene copolymers having reactive silicon groups which comprises, for 
example, the mixing of olefin-terminated isobutylene polymer, 
Pt-divinyltetramethyldisiloxane complex and methyldichlorosilane at 
100.degree. C. for 10 hours and at 80.degree. C. for 2 hours to give a 
polymer containing silyl Si(Me)(OCMe).sub.2 and isopropyl units. 
There has been a continued search for a process for making silyl endblocked 
organic polymers which does not use a pre-formed polymer thus forming the 
organic polymer and incorporating the silicon-containing group at the end 
of the organic polymer in a one-step process. 
We have now found a process for the production of silyl endblocked organic 
polymers and more particularly silyl endblocked polyolefins in which the 
corresponding monomers and/or oligomers of the organic polymer are 
contacted with a silicon-containing compound. 
According to the invention there is provided a process for making silyl 
endblocked organic polymers of the formula R.sup.1.sub.3 SiM by contacting 
under anhydrous conditions M' monomers and/or oligomers of M' with a silyl 
cation R.sup.1.sub.3 Si.sup.30 devoid of any siloxane bonds wherein each 
R.sup.1 independently denotes an optionally substituted hydrocarbon or 
hydrocarbonoxy group, hydrogen, a halogen or a monovalent siloxane-free 
silicon-containing group and M is an organic polymer made by the addition 
polymerisation of ethylenically unsaturated monomers M' of the formula 
H(R.sup.3)--C.dbd.C--(R.sup.2).sub.2 wherein each R.sup.2 independently 
denotes an optionally substituted hydrocarbon, hydrogen or a halogen and 
R.sup.3 denotes a hydrogen or methyl group. 
The use of silyl cations during a polymerisation process is known. WO 
96/08519 provides a polymerisation process comprising contacting one or 
more addition polymerisable monomers under addition polymerisation 
conditions with a catalyst system which includes a silylium salt 
corresponding to the formula R.sub.3 Si(X').sub.q.sup.+ A.sup.- wherein R 
independently each occurrence is selected from the group consisting of 
hydrocarbyl, silyl, hydrocarbyloxy, dihydrocarbylamino and combinations 
thereof having up to 30 non-hydrogen atoms, X' is an optional, neutral 
Lewis base having up to 20 non-hydrogen atoms, q is zero or one and 
A.sup.- is a non-coordinating, compatible anion. However to form the 
catalyst system, the silylium salt requires to be contacted with a Group 4 
metal complex. 
In their studies of the cationic polymerisation of 1,3-pentadiene with 
AlCl.sub.3 in n-hexane carried out in the presence of trimethylsilyl 
chloride, Y. X. Peng and W. M. Shi in Polymer Bulletin Volume 37, page 149 
to 153 (1996) have proposed a theoretical route from trimethylsilyl 
chloride and 1,3-pentadiene to a silyl endblocked polymer. However Peng et 
al. state very clearly that this route has not been made to work in their 
process. It is also clear from the discussion and references (see M. 
Kamigaito, M. Sawamoto and T. Higashimura in J. Polym. Sci., Polym. Chem. 
(Part A), Volume 29, page 1909 to 1915 (1991)) that the formation of 
carbocation C.sup.+ is intended rather than a silyl cation. 
In a process according to the invention a silyl cation must be provided. A 
silyl cation is a species that contains an electron deficient 
tri-coordinate silicon atom. In the silyl cation R.sup.1.sub.3 Si.sup.+ 
used in a process according to the invention, each R.sup.1 substituent 
independently denotes an optionally substituted hydrocarbon or 
hydrocarbonoxy group, hydrogen, a halogen or a monovalent siloxane-free 
silicon-containing group with the proviso that the silyl cation is devoid 
of any siloxane bonds (i.e. there is no presence of a Si--O--Si bond). 
Preferably R.sup.1 represents an aliphatic or aromatic hydrocarbon or a 
halogen, more preferably an alkenyl or a saturated alkyl group and most 
preferably methyl, ethyl, vinyl, hexenyl or cyclopentenyl. 
Methods for the preparation of silyl cations are known and are reported in 
Science Volume 260 pages 1917 to 1918 (1993) and Chemical Reviews Volume 
95, pages 1191 to 1201 (1995). One method requires exchanging Z from a 
compound of the formula R.sup.1.sub.3 SiZ with a suitable counter-anion 
B.sup.- optionally in the presence of solvent wherein R.sup.1 is as 
defined above and Z may be hydrogen or halogen. Preferably Z is hydrogen 
or chlorine and more preferably hydrogen. The reaction time required for 
the exchange in the preparation of the silyl cation will depend upon such 
factors as the reaction temperature, and the nature of the R.sup.1.sub.3 
SiZ compound. Preferably the reaction time is between 5 minutes to 6 
hours, preferably 5 to 90 minutes and more preferably 10 to 60 minutes. 
We have found that particularly suitable R.sup.1.sub.3 SiZ compounds for 
formation of silyl cations for use in a process according to the invention 
include trimethylsilane, triphenylsilane, methyldiphenylsilane, 
dimethylphenylsilane, dimethylchlorosilane, methyldichlorosilane, 
trichlorosilane and vinyldimethylchlorosilane and 
tri(trimethylsilyl)silane more preferably triethylsilane, 
dimethylhexenylsilane and 
[1-(3-cyclopentenyl)-3,3-dimethylbutyl]dimethylsilane. R.sup.1.sub.3 SiZ 
compounds containing siloxane bonds have been found not suitable for use 
in a process according to the invention. 
Compounds which provide counter-anions to be used for the exchange of Z are 
compounds having the formula F.sup.+ B.sup.- wherein B.sup.- is the 
counter-anion and F.sup.+ is a hydrocarbyl group. The percentage of 
cationic character of silyl cations derived from a compound of the formula 
R.sup.1.sub.3 SiZ will be affected by the choice of counter-anion B.sup.-. 
For example, the counter-anion may be of a non-coordinating nature such as 
arylborates and carboranes, for example, closocarboranes and 
bromocarboranes or of a highly coordinating nature such as derivatives of 
Lewis acids. 
In the case of non-coordinating counter-anions, preferably the 
counter-anion B.sup.- is an arylborate ion, for example, 
tetrakis[bis(3,5-trifluoromethylphenyl)]borate ion, 
tetrakis(2,3,5,6-tetrafluorophenyl)borate ion, 
tetrakis(2,3,4,5-tetrafluorophenyl)borate ion, 
methyltris(perfluorophenyl)borate ion and 
phenyltris(perfluorophenyl)borate ion and more preferably the 
counter-anion is tetrakis(pentafluorophenyl)borate ion. The hydrocarbyl 
group F.sup.+ may be represented by alkyl, aryl and aryl substituted 
alkyl groups, preferably aryl substituted alkyl groups and more preferably 
triphenylmethyl groups. Examples of suitable F.sup.+ B.sup.- compounds 
providing a counter-anion of a non-coordinating nature are 
triphenylmethyltetrakis[bis(3,5-trifluoromethylphenyl)]borate, 
triphenylmethyltetrakis(2,3,5,6-tetrafluorophenyl)borate, 
triphenylmethyltetrakis(2,3,4,5-tetrafluorophenyl)borate, 
triphenylmethylmethyltris(perfluorophenyl)borate and 
triphenylmethylphenyltris(perfluorophenyl)borate with 
triphenylmethyltetrakis(pentafluorophenyl)borate preferred. 
The F.sup.+ B.sup.- compound may also be derived from a Lewis acid where 
for example, the Lewis acid provides a counteranion B.sup.- with a 
tendency to highly coordinate to the silyl cation. Examples of suitable 
Lewis acids providing the counter-anion B.sup.- include aluminium alkyl 
halides, zirconium halides e.g. zirconium chloride, vanadium halides e.g. 
vanadium chloride, iron halides and complexes e.g. iron chloride and boron 
complexes. It is preferred that the Lewis acid is derived from halides of 
titanium, boron e.g. BF.sub.3, aluminium or antimony, e.g. antimony 
chloride and more preferably the Lewis acids is derived from aluminium 
trichloride, aluminium alkyl chloride, e.g. Al(C.sub.2 H.sub.5).sub.2 Cl, 
titanium tetrachloride or boron trichloride. The hydrocarbyl group F is as 
defined above and is preferably a triphenylmethyl group which may be 
derived from, for example, triphenylmethylchloride or diphenylmethyl group 
derived from, for example, diphenylmethylchloride. For a process according 
to the invention it is preferred that the F.sup.+ B.sup.- compound is 
derived from a Lewis acid as the exchange of Z with B.sup.- can be less 
complex and expensive. 
The F.sup.+ B.sup.- compounds can be pre-prepared or prepared in situ 
whilst in contact with the R.sup.1.sub.3 SiZ compound. Example of 
pre-prepared F.sup.+ B.sup.- compounds include 
triphenylmethylhexachloroantimonate and 
triphenylmethylpentachlorostannate. Preferably in the case of Lewis acid 
derived F.sup.+ B.sup.- compounds the F.sup.+ B.sup.- compound is 
prepared in situ. 
It is particularly preferred that in a process according to the invention 
the silyl cation is a reaction product of a prior process step in which 
R.sup.1.sub.3 SiZ has been contacted with F.sup.+ B.sup.- wherein 
R.sup.1, Z, F and B are as defined above. 
The silyl cation may be provided neat or in solvent. Suitable solvents 
include aromatic solvents, polar or non-polar solvents and mixtures of two 
or more of any of these types. Preferably non-polar solvents are not used 
for silyl cations having counter-anions derived from Lewis acids. Example 
of suitable solvents are chlorinated solvents, e.g., dichloromethane and 
1,2-dichloroethane, nitrites, hexane, toluene and benzene. The solvent is 
preferably dichloromethane or toluene. It is preferred that oxygen 
containing solvents for example, methanol, are not used with the silyl 
cation. Alternatively the silyl cation may be prepared in situ in a 
process according to the invention. By preparing the silyl cation in situ 
the process gives all the advantages of a one-step process. 
The ethylenically unsaturated monomers M' and/or oligomers of M' suitable 
for use in a process according to the invention are those which can 
undergo addition polymerisation. 
The ethylenically unsaturated monomers M' are represented by the formula 
H(R.sup.3)--C.dbd.C--(R.sup.2).sub.2 wherein each R.sup.2 and R.sup.3 is 
as defined above. Preferably R.sup.2 represents hydrogen or an alkyl group 
and more preferably methyl and preferably R.sup.3 represents hydrogen. 
Suitable monomers M' for use in a process according to the invention 
include olefins e.g., ethylene, propylene, 1-butylene, 2-methyl-2-butene, 
isobutylene, 1-pentene, 1-hexene, 2-pentene, 2-hexene, 3-methyl-1-pentene, 
4-methyl-1-pentene, 1-octene, 2-octene and 1-decene and other monomers 
such as styrene and substituted styrenes. Preferably M' represents an 
olefin having from 2 to 10 carbon atoms or styrene and more preferably 
isobutylene. Oligomers of M' may also be used. Oligomers are defined as 
polymerised molecules having fewer monomers than the polymer M for 
example, 2 to 50,000 monomers. Preferably monomers M' are used in a 
process according to the invention. A mixture of two or more types of 
monomers M' and/or oligomers of M' may also be used in a process according 
to the invention. Preferably however all monomer units M' have the same 
chemical structure. 
R.sup.1.sub.3 SiM polymers produced by a process according to the invention 
have a M portion which is an organic polymer made by the addition 
polymerisation of M' monomers and/or oligomers of M'. Examples of M are 
polyethylene, polypropylene, polyisobutylene, polystyrene and 
polypropylene/polyisobutylene co-polymers. Preferably the M portion is a 
substantially linear polymer and most preferably M is polyisobutylene. The 
R.sup.1.sub.3 Si- portion of the polymers results from the silyl cation 
used. Examples of suitable silyl endblocking groups R.sup.1.sub.3 Si- are 
trimethylsilyl, triphenylsilyl, methyldiphenylsilyl, dimethylphenylsilyl, 
dimethylchlorosilyl, methyldichlorosilyl, trichlorosilyl, 
vinyldimethylsilyl and tri(trimethylsilyl) groups with 
[1-(3-cyclopentenyl)-3,3-dimethylbutyl]dimethylsilyl, dimethylhexenylsilyl 
and triethylsilyl preferred. The molecular weight of the silyl endblocked 
organic polymer may range from 500 to 1000000 preferably from 1000 to 
500000. By careful selection of R.sup.1 substituents the silyl endblocked 
polymers may provide silicon-bonded substituents (for example 
silicon-bonded hydrogen, chlorine or vinyl groups) which can react 
according to known organosilicon chemistry teaching. For example, the 
provision of a silicon-bonded vinyl group in the silyl endblocked organic 
polymer may allow reaction via hydrosilylation with silicon-bonded 
hydrogen atoms of organosilicon compounds. 
A process according to the present invention may be carried out by merely 
mixing the reagents i.e. the ethylenically unsaturated monomers M' and/or 
oligomers of M' and the silyl cation R.sup.1.sub.3 Si.sup.+ in a reaction 
vessel optionally in the presence of a solvent. Alternatively the monomers 
and/or oligomers may be mixed directly with the pre-cursors of the silyl 
cation. Reaction conditions of temperature and pressure are not critical 
and will depend upon, for example, the monomer type and the desired 
end-product although it is preferred that a process according to the 
invention is carried out at a temperature of from below ambient to ambient 
temperature, for example, -100 to 25.degree. C., more preferably -100 to 
0.degree. C. and most preferably at -80 to -20.degree. C. and at a 
pressure of from above and below atmospheric pressure. Preferably the 
reaction is at atmospheric pressure. 
It is important that a process according to the invention is carried out in 
anhydrous conditions. The term "anhydrous" indicates that there is no free 
water present in the system i.e. no water is present which is able to 
interfere with the polymerisation reaction. The anhydrous conditions may 
be achieved by, for example, drying the reagents by known methods and/or 
by adding a suitable water scavenger to the reaction mixture for example, 
4-methyl-2,6-di-tert-butylmethylpyridine and 
4-tert-butyl-2,6-di-tert-butylmethylpyridine. It is preferred that the 
amount of water scavenger used is sufficient to merely remove any free 
water available. Excess scavenger may interfere with the reaction 
conditions, for example, the availability of the silyl cation or inhibit 
polymerisation. 
A process according to the invention may be performed in the absence of 
solvent, however, it is preferred that a solvent is present. Suitable 
solvents include aromatic solvents, non-polar and polar solvents and 
mixtures of two or more of these. However it is preferred that non-polar 
solvents are not used when silyl cations derived form Lewis acids are 
present. Examples of suitable solvents are chlorinated solvents such as 
dichloromethane and 1,2-dichloroethane, nitrites, hexane, benzene, toluene 
and xylene. It is preferred that oxygen containing solvents for example 
methanol are not used as the reaction medium. The solvent is preferably 
dichloromethane. A process according to the invention may be carried out 
in a continuous or batch mode. The process is preferably performed in an 
inert atmosphere for example nitrogen or argon. 
Sufficient silyl cation is employed to achieve the desired rate of 
polymerisation having regard to the temperature of the process, starting 
materials and other factors. In most cases it is preferred to employ from 
0.001 to 10%. by weight of the silyl cation based on the total weight of 
monomers and/or oligomers. 
When the desired silyl endblocked organic polymer has been produced, the 
process may be terminated by, for example, the inactivation of the 
counter-anion. Deactivation may be achieved by the addition of a 
neutralising agent such as methanol, methanolic solution of ammonium 
hydroxide and sodium methoxide or by heating at high temperatures. The 
silyl endblocked polymer R.sup.1.sub.3 SiM may be recovered from the 
reaction mixture by, for example, extraction, precipitation, 
centrifugation, solvent evaporation and/or other forms of separation 
techniques and may be purified as required. 
Silyl endblocked polymers made according to a process of the invention are 
usefully employed in a variety of applications, for example, in sealing 
materials, adhesives or as intermediates for the production of 
siloxane-organic copolymers.

The following examples are provided to illustrate the invention in 
conjunction with comparative examples. 
EXAMPLE 1 
Preparation of Triethylsilyl Endblocked Polyisobutylene using Isobutylene, 
Triethylsilane and Triphenylmethyl-tetrakis(pentafluorophenyl)borate 
(TTFB) 
a: Pre-preparation of Silyl Cation. 
1.1 g of liquid isobutylene and 2.times.10.sup.-3 g of 
4-methyl-2,6-di-tert-butylmethylpyridine (DBMP) were added to a reaction 
flask A containing 22 ml of toluene (previously dried over calcium hydride 
and stored under argon) and cooled to -78.degree. C. In a separate 
reaction flask B, 117.7 .mu.mole TTFB (synthesised according to the method 
of Chien et al. as described in the Journal of American Chemical Society 
1991, Volume 113, pages 8570 to 8571) was mixed with 117.7 .mu.mole of 
triethylsilane in 2 ml of toluene and the mixture allowed to react for 60 
minutes at 25.degree. C. before addition via a syringe to the reaction 
flask A. The temperature of the reaction was maintained at approximately 
-78.degree. C. for a further 20 minutes before termination by the addition 
of a methanolic solution of ammonium hydroxide. The reaction mixture was 
then subjected to the following work-up procedure. Solvent was removed 
from the reaction mixture by stripping the mixture under reduced pressure. 
The recovered reaction product was dissolved in tetrahydrofuran (THF) and 
precipitated in 0.5 l methanol and then characterised by GPC, .sup.29 Si 
and .sup.13 C NMR. The reaction product was shown to be polyisobutylene 
endblocked with triethylsilyl groups with a .sup.29 Si NMR chemical shift 
at 9.0 ppm attributed to the silicon in the (C.sub.2 H.sub.5).sub.3 
SiCH.sub.2 -terminal unit and .sup.13 C NMR chemical shifts of 6.17 ppm 
and 5.79 ppm attributed to the methyl and methylene groups respectively in 
the (CH.sub.3 CH.sub.2 ).sub.3 SiCH.sub.2 terminal unit. 
b: In-situ Preparation of Silyl Cation. 
0.50 g, 0.785 mmol of TTFB was added to a reaction flask and dried under 
vacuum at 150.degree. C. The reaction flask was cooled by immersion in an 
acetone-dry ice bath and 20 ml of anhydrous dichloromethane (dried over 
phosphorus pentoxide) and 2.4 ml of liquid isobutylene were distilled into 
the reaction flask. 0.785 mmol of DBMP dissolved in anhydrous 
dichloromethane and 0.785 mmol triethylsilane were added to the reaction 
flask via a syringe and stirred under nitrogen for one hour at -60.degree. 
C. The reaction was quenched by the addition of methanol (2 ml). Solvent 
was removed from the mixture by stripping the reaction mixture under 
reduced pressure. The reaction product was dissolved in hexane (2 ml) and 
precipitated in an excess of methanol (200 ml). Characterisation of the 
reaction product by GPC and .sup.29 Si NMR indicated that the product was 
triethylsilyl endblocked polyisobutylene (Mw 62100, Mw/Mn 1.39) with a 
.sup.29 Si NMR chemical shift at 9.00 ppm attributed to the silicon in the 
(C.sub.2 H.sub.5).sub.3 SiCH.sub.2 -terminal unit. 
COMATIVE EXAMPLE 1 
Absence of Water Scavenger 
The procedure of Example 1a was repeated, in the absence of DBMP using 
1.518 g of liquid isobutylene, 463.2 .mu.mole of TTFB and 463.2 .mu.mole 
of triethylsilane. 
Characterisation of the reaction product by GPC, .sup.29 Si and .sup.13 C 
NMR indicated that the isobutylene had polymerised to form polyisobutylene 
(Mw 17440, Mw/Mn 5.76) with no triethylsilyl endblocking units present. 
This example shows the importance of working in anhydrous conditions. 
EXAMPLE 2 
Preparation of Silyl Endblocked Polyisobutylene using Isobutylene, 
Dimethylhexenylsilane and TTFB 
The procedure of Example 1b was repeated using 0.785 mmol of 
dimethylhexenylsilane in place of triethylsilane. Characterisation of the 
reaction product by GPC and .sup.29 Si NMR indicated that the product was 
dimethylhexenylsilyl endblocked polyisobutylene (Mw 10100, Mw/Mn 2.75) 
with a .sup.29 Si NMR chemical shift at 7.65 ppm attributed to the silicon 
in the Me.sub.2 (CH.sub.2 .dbd.CHCH.sub.2 CH.sub.2 CH.sub.2 
CH.sub.2)SiCH.sub.2 -terminal unit. 
EXAMPLE 3 
Preparation of Silyl Endblocked Polystyrene using Styrene, Triethylsilane 
and TTFB 
The procedure of Example 1a was repeated using 1.82 g, 48 mmol of 
pre-distilled styrene in place of the isobutylene. Triethylsilyl 
endblocked polystyrene (Mw 326000, Mw/Mn 2.35) was obtained in 89% yield 
with a .sup.29 Si NMR shift of 6.29 ppm corresponding to the silicon in 
the (C.sub.2 H.sub.5).sub.3 SiCH.sub.2 -terminal unit. 
EXAMPLE 4 
Preparation of Silyl Endblocked Polystyrene using Styrene, 
Dimethylhexenylsilane and TTFB 
The procedure of Example 1b was repeated using 0.785 mmol of 
dimethylhexenylsilane and 1.82 g, 48 mmol of predistilled styrene in place 
of triethylsilane and isobutylene respectively. Dimethylhexenylsilyl 
endblocked polystyrene (Mw 52000, Mw/Mn 2.58) was obtained in quantitative 
yield with a .sup.29 Si NMR shift of 7.90 ppm corresponding to the silicon 
in the Me.sub.2 (CH.sub.2 .dbd.CHCH.sub.2 CH.sub.2 CH.sub.2 
CH.sub.2)SiCH.sub.2 -terminal unit. 
EXAMPLE 5 
Preparation of Silyl Endblocked Polyisobutylene using Isobutylene, 
Triethylsilane, Titanium Tetrachloride and Triphenylmethylchloride 
a: Use of Dichloromethane as Solvent. 
0.641 g (2.3 mmole) of triphenylmethylchloride was added to a reaction 
flask and dried under reduced pressure. The reaction flask was cooled to 
-70.degree. C. in an acetone-dry ice bath and 20 ml of dry dichloromethane 
(distilled over phosphorous pentoxide), 5.6 g of isobutylene and 0.2 mmole 
of DBMP were added to the flask. 4 ml of titanium tetrachloride (1M 
solution in dichloromethane) was then added to the flask followed by the 
injection of 0.233 g (2 mmole) of triethylsilane. The reaction mixture was 
stirred for 30 minutes at approximately -70.degree. C. under nitrogen 
before the addition of excess of methanol (2 ml) to quench the reaction. 
The reaction product was recovered following the work-up procedure of 
Example 1a. Characterisation of the resulting polymer via .sup.29 Si NMR 
indicated that the polymer was triethylsilyl endblocked polyisobutylene 
with a .sup.29 Si NMR signal at -9.0 ppm corresponding to the silicon in 
the (C.sub.2 H.sub.5).sub.3 SiCH.sub.2 -terminal unit. 
b: Use of Hexane as Solvent. 
The procedure of Example 5a was repeated using hexane in place of 
dichloromethane. The .sup.29 Si NMR indicated that the resulting polymer 
was triethylsilyl endblocked polyisobutylene with a .sup.29 Si NMR signal 
at 9.04 ppm corresponding to the silicon in the triethylsilyl group. 
EXAMPLE 6 
Preparation of Silyl Endblocked Polyisobutylene using Isobutylene, 
Dimethylhexenylsilane, Titanium Tetrachloride and Triphenylmethylchloride 
The procedure of Example 5a was repeated using dimethylhexenylsilane in 
place of triethylsilane. The resulting polymer was dimethylhexenylsilyl 
endblocked polyisobutylene at 70% yield with a .sup.29 Si NMR signal at 
7.435 ppm corresponding to dimethylhexenylsilyl terminal groups. 
EXAMPLE 7 
Preparation of Silyl Endblocked Polyisobutylene using Isobutylene, 
Dimethylhexenylsilane and Triphenylmethyl hexachloroantimonate 
0.52 g (1.87 mmole) of triphenylmethylhexachloroantimonate was added to a 
50 ml reaction flask, pre-dried with a heat gun under reduced pressure and 
then 30 ml of dry methylene chloride, 0.5 mmole of DBMP was added. The 
mixture was cooled to approximately -70.degree. C. before the addition of 
9.5 ml (0.1 mole) of isobutylene and 0.2 ml (1.38 mmole) of 
dimethylhexenylsilane. The reaction mixture was stirred for a period of 30 
minutes at approximately -70.degree. C. The polymerisation was terminated 
by the addition of methanol and the reaction product recovered by 
following the work-up procedure of Example 1a. The .sup.29 Si NMR of the 
reaction polymer indicated that dimethylhexenylsilyl endblocked 
polyisobutylene was formed with a signal at 7.435 ppm corresponding to 
dimethylhexenylsilyl terminal groups and this was also confirmed by a 
.sup.1 H NMR signal at 0.466 ppm corresponding to --CH.sub.2 
--Si(CH.sub.3).sub.2 C.sub.6 H.sub.11. 
EXAMPLE 8 
Preparation of Silyl Endblocked Polystyrene using Styrene, 
Dimethylchlorosilane, Chlorodiethylaluminium and Triphenylmethylchloride 
0.69 g (2.48 mmole) of triphenylmethylchloride was added to a dry reaction 
flask followed by 30 ml of dry methylene chloride and 0.5 mmole of DBMP. 
The mixture was cooled to approximately -70.degree. C. and then 4.5 g 
(0.043 mole) of styrene, 0.5 ml (4.8 mmole) of dimethylchlorosilane and 4 
ml of chlorodiethylaluminium (1 M solution in hexane) were added. After a 
reaction period of 30 minutes the reaction product was recovered following 
the work-up procedure of Example 1a. Characterisation of the resulting 
polymer indicated the presence of dimethylsilyl end groups attached to 
polystyrene with a .sup.29 Si NMR signal at -18.716 ppm. 
EXAMPLE 9 
Preparation of Silyl Endblocked Polyisobutylene using Isobutylene, 
Dimethylchlorosilane, Titanium Tetrachloride and Triphenylmethylchloride 
The procedure of Example 8 was repeated using 0.957 g (3.44 mmole) of 
triphenylmethylchloride and 0.4 ml (2.8 mmol) of chlorodimethylsilane. 3.6 
g (0.064 mole) of isobutylene and 4 ml of titanium tetrachloride (1 M 
solution in dichloromethane) was used in place of styrene and 
chlorodiethylaluminium. Characterisation of the reaction product indicated 
the presence of silyl endblocking groups attached to polyisobutylene with 
a .sup.29 Si NMR signal at -18.92 ppm.