Polyisobutene macromonomers

Kennedy 67,77 118) studied the ability of w-styryl-polyisobutene macromonomers to undergo free-radical copolymerization with either styrene or butyl or methyl methacrylate. Here, the macromonomers exhibited a relatively high molecular weight of 9000, and the reaction was stopped after roughly 20% of the comonomer had been converted. The radical reactivity ratios of styrene and methyl methacrylate with respect to macromonomer were found to be equal to 2 and to 0.5, respectively. From these results, Kennedy concluded that in the ra-styrylpolyisobutene/styrene system the reactivity of the macromonomer double bond is reduced whereas with methacrylate as the comonomer the polar effect is the main driving force, yielding reactivities similar to those observed in the classical system styrene/MMA. 

However, no indications are given of the molecular weights nor of the compositional heterogeneity of the graft copolymers, their properties or potential applications. The existence of a microphase separation was evidenced however on methyl metha-crylate/polyisobutene graft copolymers by means of DSC measurements. Two glass transitions were observed at —68 °C (polyisobutene) and at 102 °C (PMMA), i.e. at the same temperatures at which they occur in the corresponding hono-polymers. 

The polyisobutene macromonomers bearing a methacryloyl group at both chain ends have not been copolymerized so far. Yet this would provide a route to a new kind of tailor-made networks. 

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Other functionalizations of polyisobutene have been performed 78) by means of the inifer technique and subsequent reaction at the chain end. Polymers bearing terminal carboxylic acid or anhydride functions can also be considered as potential starting materials for the synthesis of polyisobutene macromonomers. 

Apart from the syntheses by living cationic polymerizations, a variety of polyisobutene macromonomers have been prepared by converting the chloride terminal derived from the inifer method (Section IV.A.3) [166-170] and more recently from living cationic polymerization... 

It should be recalled that various other two-step macromonomer synthesis have been developed using the inifer technique as an adequate functionalization method for preparing the precursor. Thus, starting from to-chloro-polyisobutene, the de-hydrohalogenation can be followed by hydroboration and selective oxidation to yield almost quantitatively the -hydroxy precursor 78) ... 

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