New mesogenic maleimide-styrene copolymers via N-oxyl mediated free radical copolymerization

Abstract

New mesogenic N-substituted maleimide monomer was obtained starting 4-maleimido benzoic acid, hydroquinone and hexadecyloxy benzoic acid by successive Schotten-Bauman condensations. The copolymerization of this monomer in 1:1 ratio with styrene was performed both by stable free radical polymerization (SFRP) and conventional free radical polymerization (CFRP). High molecular weight polymeric material in high conversion and with low polydispersity was obtained under SFRP conditions. By using ¹H- and ¹³C-NMR techniques, structural characteristics of the polymers were evidenced that could sustain the alternating character of the copolymers and the participation of the electron donor–acceptor complex in the propagation step. The copolymers formed a liquid crystal mesophase in the melt. This was ascribed to the strong tendency of the rod-like side groups on the stiff imide ring to order even in 1:1 dilute systems such as the alternating copolymers.

Keywords:

• Liquid-crystalline polymers
• stable free radical polymerization
• alternating copolymers
• mesogenic maleimide
• styrene.