A new route toward imidazoline-functionalized porous polymeric materials from corresponding polystyrene-polylactide diblock copolymers

Novel imidazoline-functionalized diblock copolymers based on polystyrene (PS) and poly(D,L-lactide) (PLA) were synthesized as precursors to corresponding functional PS-based porous materials through a three-step sequential methodology starting from an asymmetric heterobifunctional initiator. α-Hydroxyl poly(4-cyanostyrene-co-styrene) random copolymers were first obtained via an atom transfer free-radical polymerization (ATRP) procedure by varying the amount of 4-cyanostyrene in the comonomer feed. Cyano groups were then transformed into corresponding imidazoline rings. Subsequently, the microwave-assisted ring-opening polymerization (ROP) of d,l-lactide from the imidazoline-functionalized PS-based macroinitiators allowed for the generation of semi-degradable diblock copolymers with different PLA volume fractions so as to develop microphase-separated morphologies. The precursors and resulting copolymers were analyzed by 1H, 13C NMR, and FT-IR spectroscopy. Upon induced shear-flow via channel-die processing, oriented materials constituted of PLA nanodomains in a polystyrene-based continuous matrix were formed. Hydrolysis in alkaline conditions of the PLA sacrificial block yielded imidazoline-functionalized porous PS-based matrices. The resulting porous frameworks were analyzed by scanning electron microscopy (SEM) and nitrogen sorption porosimetry.