Recent Advances in Controlled Grafting of Elastomers

Abstract

Abstract This review describes recent results for preparing graft copolymers with controlled structures. In general, the macromonomer approach appears to be the most promising method for preparation of graft polymers with well defined structures. Not only can macromonomers be prepared using radical, cationic, or anionic polymerization procedures, but the resultant macromonomers can be polymerized using these same methods. Obviously, the macromonomer functionality must be high and well defined. In addition, the average chain length and chain length distribution should be well characterized. In principle, the macromonomer approach can provide comb-type graft copolymers with a random distribution of well characterized graft branches. However, the actual copolymerization of the macromonomers with a variety of comonomers requires careful examination under a variety of reaction conditions before that expectation can be realized. These macromonomers provide an excellent opportunity to examine the effects of chain length on the problem of heterogeneity (i.e., phase-separation) which is expected and found in many grafting systems. “Grafting-from” reactions also should provide graft polymers whose structures are more amenable to prediction and analysis. Like the macromonomer method, it should be possible to eliminate the presence of unwanted homopolymer using this method. However, much more research is required before the generality and value of this method can be evaluated. In conclusion, this era appears to be an exciting time for graft polymerization research. The potential exists for the preparation of model graft polymers with precise structural definition using the methods described herein. This development will, at last, provide graft polymers which can be used to define the relationships between the structure, morphology, and properties of these materials.