ABSTRACT
The search for monomers that exhibit either zero volume change or positive volume change during polymerization has been an intriguing and sometimes frustrating problem. One of the more significant observations made in reduction of shrinkage was that the single ring-containing monomers, which polymerize through the ring-opening polymerization process, produce less shrinkage than any of the other forms of polymerization. During ring-opening polymerization, it is possible to go directly from a low molecular weight heterocyclic or ring monomer to a linear, straight-chain, high molecular weight polymer composed of many monomeric units. The three effects that influence degree of volume change during ring-opening polymerization are ring size, number of rings per unit volume, and the ring opening effect. The chapter presents the synthesis and polymerization of a few select monomers from each class of cyclic materials found to expand during polymerization. The possibility of attaining a ring-opening monomer from a purely cycloaliphatic system that would exhibit expansion during polymerization becomes extremely remote.
