Isomorphism phenomena in macromolecules

Abstract

AbstractThrough x‐ray and infrared examinations of stereoregular polymers and copolymers of vinylaromatic monomers, the occurrence of chain isomorphism phenomena, together with many cases of a new type of isomorphism between monomeric units, have been proved. Isomorphism of macromolecules, allowing true solid solutions, has been observed when melting and crystallizing mixtures of homopolymers (i.e., isotactic polystyrene) and of crystalline copolymers (i.e., styrene‐p‐methylstyrene) having the same identity period and differing very little in lattice constants. Isomorphism among monomeric units occurs in copolymerizing monomers that have a chemical nature and shape slightly different one from the other, e.g., styrene and o‐fluorostyrene. This allows the formation of crystallizable copolymers in the entire composition range. They show physical properties (lattice constants, melting temperatures, etc.) continuously varying between those of the pure homopolymers. The occurrence of isodimorphism phenomena has been observed in crystalline copolymers obtained from monomers the homopolymers of which have different crystalline structures (e.g., styrene‐p‐fluorostyrene), and also in copolymerizing styrene with monomers (e.g., p‐methyl, p‐chlorostyrene) giving only amorphous homopolymers. In the latter case, of course, the copolymers show crystallinity only in a limited composition range.