Synthesis and Characterization of Sequence-Controlled Semicrystalline Comb Copolymers: Influence of Primary Structure on Materials Properties

Sequence-controlled semicrystalline copolymers were prepared by nitroxide-mediated copolymerization of a large excess of octadecylstyrene with small amounts of functional N-substituted maleimides (i.e., N -( n -propyl)maleimide, N -benzylmaleimide, pentafluorophenyl 4-maleimidobenzoate, 4-( N -maleimido)azobenzene, N -(1-pyrenyl)maleimide, and N -(2-(amino-BOC)ethylene)maleimide). These copolymers were prepared in bulk at 110 °C using the commercial alkoxyamine BlocBuilder MA as initiator and control agent. Time-controlled additions protocols were used to place the N-substituted maleimides at precise chain location along the poly(octadecylstyrene) backbones. Size exclusion chromatography and 1 H NMR studies indicated that well-defined copolymers with controlled monomer sequences, composition, chain length, and molecular weight distribution were formed in all cases. Although possessing an atactic backbone, these polymers exhibit a semicrystalline behavior. The electron diffraction method indicated that the octadecyl side chains form lamellar phases. Moreover, differential scanning calorimetry studies evidenced a melting temperature in the range 40–45 °C and a crystallization temperature around 30–35 °C. It was observed that melting is influenced by the composition and sequence distribution of the copolymers. Thus, small microstructural variations allow a precise control over order–disorder transitions.