Graft copolymers of para‐hydroxybenzoic acid (PHB). I. A general method for grafting mesogenic oligo‐PHB to oligomers

Abstract A method for grafting oligo‐(p‐hydroxybenzoic acid) to carboxyl‐functional oligomers or polymers to give copolymers having mesogenic side chains was developed. The method employs dicyclohexylcarbodiimide (DCC) to promote esterification of PHB at mild temperatures and to remove water. Pyridine is used as solvent, and catalytic amounts of p‐TSA are added to suppress side reactions. Grafting efficiencies are estimated to range from 74 to 90%. Ungrafted oligo‐PHB and other by‐products are readily removed. Structure assignments were supported by IR,1H‐NMR, GPC, DSC and model compound studies. The method appears capable of grafting oligo‐PHB side chains to any pyridine soluble oligomer or polymer having carboxyl groups and no other reactive groups that could interfere.