Solvent- and solvothermal-induced phase transitions and crystallisations in syndiotactic polystyrene and multiblock copolymer syndiotactic polystyrene-co-cis-1,4-polybutadiene

Abstract

The complex polymorphism of nanoporous syndiotactic polystyrene never stops to amaze. Simple and rapid solvent- and solvothermal-induced crystallisation of syndiotactic polystyrene (sPS) and syndiotactic polystyrene polymer segments in the multiblock copolymer syndiotactic polystyrene-co-cis-1,4-polybutadiene (sPSB) into the desired crystalline form have been disclosed and herein reported. Stirring polymer powders of sPS in the chloroform/water solvent mixture allows crystallisation of the amorphous phase and the conversion of the co-crystalline δ forms into the highly crystalline δ form; variable combinations of water with other common non-polar solvents, or of chloroform with methanol failed in this transformation. The γ form has been obtained by solvothermal treatment of the δ form by simple refluxing in acetonitrile. Stirring the γ form in chloroform/water mixture affords its rapid conversion into the ε form with elevated crystallinity. Finally, applying the chloroform/water treatment to the β form yields the δ form with high crystallinity. The complex polymorphism of the sPS was also found in sPSB copolymer, even with short styrene segments. The thermal behaviour, in terms of melting enthalpy and temperature, was investigated at the variance of styrene content.