Polyisobutylene initiator

Postpolymerization of difunctional monomers to effect star branching has been successfully applied in cationic polymerization, e.g. in the case of polyisobutylene initiated with 2-chloro-2,4,4,-trimethylpentane/TiCl4. Addition of divinylbenzene leads to star polymers [104], Vinyl ethers, when polymerized with HI/ZnI2 in toluene at — 40°C, can be copolymerized with divinylether... 

Fig. 1. Polymerization of isobutyiene with various initiating ions in conjunction with (C2H )2A1C1 (3). PIB =polyisobutylene.

This section concerns the synthesis of polyisobutylenes (PIB) bearing a Si-H head-group (HSi-PIB) by the use of Si-H containing functional initiator in conjunction with Me3Al coinitiator. First the effect of reaction conditions on the rate and molecular weight have been investigated and subsequently a H1 NMR method for the quantitative characterization of Si-H groups in HSi-PIB was developed. 

Further, while conventional Friedel-Crafts halides produce high molecular weight polyisobutylenes or polyisobutylene copolymers (e.g., butyl rubbers, HR) only at relatively low ( —100 °C) temperatures, alkylaluminum-based initiator systems produce high molecular weight materials at much higher ( —40 °C) temperatures. 

In previous papers1,2 we described reactivity studies of cationic isobutylene polymerization using r-butyl halide initiators, alkylaluminum coinitiators and methyl halide solvents. The effects of these reagents as well as temperature on the overall rate of polymerization and polyisobutylene (PIB) yield were studied and reactivity orders were established. These results were explained by a modified initiation mechanism based on an earlier model proposed by Kennedy and co-workers3,4. This paper concerns the effects of f-butyl halide, alkylaluminums and methyl halide, as well as temperature and isobutylene concentration on PIB molecular weights. 

Puskas, J.E., Pattern, W.E., Wetmore, P.M., and Krukonis, A. Multiarm-star polyisobutylene-polystyrene thermoplastic elastomers from a novel multifunctional initiator, Polym. Mater. Set Eng., 82,42 3, 1999. Brister, L.B., Puskas, J.E., and Tzaras, E. Star-branched PIB/poly(p-t-bu-Styrene) block copolymers from a novel epoxide initiator, Polym. Prepr., 40, 141-142, 1999. 

Puskas, J.E., Brister, L.B., Michef A J., I-anzenddrfer, M.G., Jamieson, D., and Pattern, W.G. Novel substituted epoxide initiators for the carbocationic pol3mierization of isobutylene, 7. Polym. Set, 38,444-451, 2000. Puskas, J.E. and Michel, A.J. New epoxy initiators for the controlled synthesis of functionalized polyisobutylenes, Makromol. Chem., Macromol. Symp., 161, 141-148, 2000. 

Fig. 117.—Log (RTA2) for polyisobutylene fractions in cyclohexane at 30°C plotted against log M. The filled circles represent the initial slopes RTA2) of the curves shown in Fig. 38. The open circles are from earlier results on the same system. Dashed line calculated as described in text. (Krigbaum ).

When this procedure is applied to the data shown for polystyrene in Fig. 116 and to those for polyisobutylene shown previously in Fig. 38 of Chapter VII, the values obtained for t/ i(1 — /T) decrease as the molecular weight increases. The data for the latter system, for example, yield values for this quantity changing from 0.087 at AT-38,000 to 0.064 at ilf = 720,000. This is contrary to the initial definition of the thermodynamic parameters, according to which they should characterize the inherent segment-solvent interaction independent of the molecular structure as a whole. 

The conductimetric, kinetic, and radiochemical experiments lead to the conclusion that alkenes, but not strainless alkanes, are aluminated by A1X2+. This and the balance of the number of C-Al bonds in our polyisobutylenes support Proposition 2 that initiation is by reaction (iii). 

New Telechelic Polymers and Sequential Copolymers by Polyfunctional Initiator-Transfer Agents (Inifers) End Reactive Polyisobutylenes by Semicontinuous Polymerization... 

In the absence of substantial unsaturation and of active groups on the chain for either polymer, only linear block copolymers are formed, according to the initiation Reactions 1 and 4. Low density polyethylene and high molecular weight polyisobutylene are typical of polymers which form block copolymer fractions on intensive mechanical working. The composition of block copolymers is related also to the relative rates of reaction, (Reactions 2 and 3) which is determined by the relative radical reactivity. 

This review concerns the synthesis and characterization of octa-arm polyisobutylene (PIB) stars, allyl-terminated octa-arm PIB stars, and octa-arm star blocks by using a novel octafunctional caHx[8]arene-based initiator 1. Scheme 1 shows the structure of 1 and the target architectures. The syntheses were carried out under living carbocationic polymerization conditions. 

T. Sawaguchi and M. Seno, Thermal degradation of polyisobutylene effect of end initiation from terminal double bonds, Polym. Degrad. Stab., 54(l) 33-48, October 1996. 

J.P. Kennedy and R.A. Smith, New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (inifers). II. Synthesis and characterization of a, a>-di(ferf-chloro)polyisobutylenes,. Polym. Sci., Part A Polym. Chem., 18(5) 1523-1537,1980. 

Dependencies of total strain b = 1/10 upon time t, in extension of polyisobutylene 11-20 (USSR) at constant force F for different initial stresses ct0 = F/S0 (here S0 is the cross-sectional area of the sample at t = 0) are given in Fig. 4. 

Division of the total tensile strain under conditions of F = const into several components 25,6R,69) produced interesting results (see Fig. 8). It has been found that the behavior of molten low-density polyethylene (Fig. 8a) is qualitatively different from polyisobutylene (Fig. 8 b) the extension of which was performed under temperature conditions where the high-elasticity modulus, relaxation time, and initial Newtonian viscosity practically coincided (in the linear range) in the compared polymers. Flow curves in the investigated range of strain velocities were also very close to one another (Fig. 21). It can be seen from the comparison of dependencies given in Fig. 8a,... 

The Inifer Method. A special case of controlled initiation is the inifer method (17). The word inifer (from initiator trans/t / agents) describes compounds that function simultaneously as initiators and as chain-transfer agents. Chain transfer to inifer regenerates R+. The inifer technique provided the first carbocationic route toward the synthesis of telechelic (a,G) functional) polyisobutylenes and more recendy telechelic poly( >-chlorostyrenes) (18). To prepare telechelic products chain transfer to monomer must be absent, and with BC13 as coinitiator this requirement is fulfilled. 

The radical initiated copolymerization of C2H4 and CO in the presence of a polyolefin has been reported to result in the grafting of the C2H —CO copolymer onto the polyolefin backbone31). Polyolefins used included polyethylene, ethylene-propylene copolymer and polyisobutylene. 

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