Volume contraction of the polymerizing system

Calculated contraction values for polymerizations of some monomers [76] 

To a first approximation, the contraction of hydrocarbon monomers appears to be related to the number of their atoms (the contraction of styrene with eight carbon atoms is four times less than that of ethylene). Polar substituents cause deviations from this rule. In ring-opening propagation. 

Monomers opening at least two rings in linear chains formation polymerize either without any volume change, or with a small expansion.  

Many such monomers have been found [77-79], one of which is shown as an example [80]. 

11-tetraoxaspiro [5,5] undecane is a crystalline compound of m. p. 514 K. It is polymerized both in the solid and in the liquid phases. By cationic polymerization at 523 K, it yields a macromolecular polycarbonate with ether bonds with a volume expansion of 2 %. Polymerization of the crystalline monomer yields the same polymer with a volume expansion of 17 %. 

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