Extended‐chain crystals of POM‐copolymers: Synthesis, structure and properties

The synthesis of extended chain crystals of copolymers of trioxane and 1,3‐dioxolane, 1,3‐dioxane, 1,3‐dioxepane, and 1,3,6‐trioxocane by cationic copolymerization is described. Density, melting point, and enthalpy of melting are reported as depending on the mole fraction x2 of the comonomer units. In each series the density decreases linearly with increasing comonomer content for x2 < 0,1. The melting temperature Tm decreases first linearly with increasing x2, but reaches a plateau in which Tm becomes independent of the composition. The data are analysed in terms of Eby's theory of melting behaviour, and defect enthalpies related to the individual comonomer units are derived.