Electrostatic Forces-Induced Transformation of an Atactic Polymer from Amorphous to Semicrystalline

Quaternization of P4VP by alkyl halides with varying number of carbons (n = 1 – 12) presents a platform to study the interplay between electrostatic attractive and steric repulsive forces. In P4VP-based random copolymers, the competition between these forces results in two distinct short-range ordering: ion clusters and backbone-to-backbone spacing. For copolymers quaternized with methyl or ethyl halides (n = 1 – 2), dipole forces are dominant forming ion clusters; while for copolymers quaternized with longer alkyl halides (n = 3 – 8), steric repulsion is dominant resulting in backbone-to-backbone spacing. The competition between electrostatics and sterics also governs the morphology of quaternized P4VP homopolymer. Unlike in the copolymers where clusters of ions are formed when dipole forces are dominant, for P4VP_CnI and P4VP_CnBr, the atactic amorphous microstructure is transformed into an atactic semicrystalline. Characterization of P4VP_C2I and P4VP_C2Br by WAXS show distinct Bragg peaks of a primitive simple cubic structure with possible polymorphism.Thermal analysis shows double melting endotherms with a single recrystallization exotherm. Macrostructures of samples probed by POM show that crystals upon nucleation can grow into spherulites or dendrites.