Self-regulated phase transitions in poly(4-{2-[4′-(11-vinyloxyundecyloxy)biphenyl-4-yl]ethyl}benzo-15-crown-5) and poly(4-{2-[4′-(11-methacryloylundecyloxy)biphenyl-4-yl]ethyl}benzo-15-crown-5)via molecular recognition

Abstract

The syntheses of 4-{2-[4′-(11-vinyloxyundecyloxy)biphenyl-4-yl]ethyl}benzo-15-crown-5 (12) and 4-{2-[4′-(11-methacryloylundecyloxy)biphenyl-4-yl]ethyl}benzo-15-crown-5 (14) and their respective cationic and radical polymerizations to yield liquid-crystalline poly(12) and poly(14) are described. Poly(12) with a degree of polymerization of 6 exhibits a monotropic smectic A (S_A) phase, while the higher-molecular-weight polymers exhibit an enantiotropic S_A phase. Poly(14) displays an enantiotropic S_A and an unidentified higher-order smectic phase. Both poly(12) and poly(14) display crystalline phases also. The mesomorphic behaviour of the complexes of both polymers with NaSO₃CF₃ was investigated. Complexation increases the isotropization temperature of the highest temperature mesophase and decreases the temperature transition of crystalline and higher-order smectic phases. Therefore, this complexation transforms virtual and monotropic mesophases into enantiotropic mesophases and also increases the thermodynamic stability of the highest temperature mesophase. These results have demonstrated the ability of these polymers to self-regulate their phase behaviour via molecular recognition of metal salts by their 15-crown-5 receptor.