INVESTIGATIONS ON FREE-RADICAL POLYMERIZATION OF PHENYL-SUBSTITUTED 2-METHYLENE-1,3-DIOXANES

We have investigated the free radical polymerization of phenyl-substit uted 2-methylene-1,3-dioxanes. It was shown that there isa basic tende ncy of such ketenacetals to undergo exclusively a vinyl polymerization forming high-molecular polyacetals without any detectable ring openin g. The polymerization with the desirable ring opening reaction cannot be controlled by factors like resonance stabilized chain ends or steri c hindrance in the growing step. From densitometric measurements we go t new information about the shrinkage behaviour. It was demonstrated t hat bulky substituents attached to the 2-methylene-1,3-dioxane system result in a significant low shrinkage in homopolymerization and the sh rinkage of common comonomers can be decreased by copolymerization.