Block and Graft Copolymers of Polypivalolactone : Poly(Acrylate-g-Pivalolactone)

Abstract

Abstract Thermoplastic poly(acrylate-g-pivalolactone) elastomers depend upon the crystallization of polypivalolactone side chains into discrete domains for the reversible formation of elastomeric networks. The high crystallinity of the grafted polyPVL chains and their chemical inertness leads to a highly reinforced, effectively crosslinked copolymer of unusual stability. The physical properties of the graft copolymer are similar to those of elastomeric polyacrylates compounded with carbon black and chemically crosslinked. At high deformation, as on a two-roll mill, the crystalline domains are sufficiently disrupted to allow the polymer to flow easily. At low deformation, for example in the compression-set test, there is very little flow, as shown by resistance to compression set fully equivalent to that of covalently crosslinked elastomers. The synthesis of polyacrylate-g-PVL copolymers is remarkably simple and subject to few limitations. Grafting efficiency is high and should approach 100% under slightly more rigorous conditions than employed in this work. These copolymers are unique in the ease and precision with which both hard and soft segment length can be varied to control the physical properties of the product.