Whisker of poly(p-oxybenzoyl-co-p-mercaptobenzoyl) - influence of sequence on polymer morphology

Aromatic polymers are expected to possess outstanding properties. However, in many cases they do not show good processability because of their chain regidity. We have been studying the morphology control of rigid polymers during polymerization to overcome this problem and succeeded in preparing the whiskers of poly (p-oxybenzoyl) and poly (p-mercaptobenzoyl) by the polymerization in liquid paraffin at around 300 °C. These whiskers are formed by the reaction induced crystallization of oligomers during solution polymerization. The preparation of copolymer whiskers is very interesting to design the new materials which are endowed with novel functions. The aim of this study is to prepare the whisker of poly (p-oxybenzoyl-co-p-mercaptobenzoyl) and to clarify the influence of the copolymerization on the morphology, especially focusing on the sequence regularity. The introduction of comonomer unit into polymer chain structure extinguishes the crystal habit due to the lower crystallizability and the whiskers can be obtained by the random copolymerization of 4-acetoxybenzoic acid (ABA) and S-acetyl-4-mercaptobenzoic acid (AMBA) only when %f (the molar ratio of ABA/AMBA in feed) is 1.0-0.7 and 0.05-0. However, the copolymer whiskers are obtained by the polymerization of OS, OOS and SSO monomers which produce the alternating and periodic copolymers. These copolymer whiskers consist of the alternating or periodic copolymer chains and their chains align along the long axis of the whisker. The sequence regularity enhances the crystallizability of cooligomers and this leads to the formation of the whiskers. The sequence regularity in copolymers is a very influential parameter to control the morphology and the copolymer whiskers can be prepared by giving the regular sequences.