PREPARATION AND PROPERTIES OF LIQUID-CRYSTALLINE ALKYD RESIN WITH PARA-HYDROXYBENZOIC ACID MESOGENIC SIDE-CHAIN

Liquid crystalline (LC) alkyd resins with mesogenic side chains are prepared with the following three methods: (a) grafting p-hydroxybenzoic acid (PHBA) to hydroxy-terminated alkyd resin, (b) grafting PHBA to carboxyl-terminated alkyd resin, and (c) grafting PHBA to an excess succinic anhydride-modified alkyd resin. Dicyclohexylcarbodiimide (DCC) is employed to react with formed water in promoting esterification of PHBA with alkyd at room temperature. Pyridine is used as a solvent, and the catalytic amounts of p-toluene-sulfonic acid (p-TSA) is added to suppress side reaction and to promote esterification. Grafting efficiency (% GE) is estimated to range from 70 to 95%. The character of liquid crystallinity is imparted only when at least two or more aromatic units of PHBA are connected to form the rodlike mesogenic side chain. At present, we have found that LC alkyd resins have the following merits: the polymer solution viscosity is reduced; the coating's dry-to-touch time is reduced; and the coating film is both hardened and toughened and has excellent resistance to water and acid.