Syntheses of hyperbranched liquid-crystalline biopolymers with strong adhesion from phenolic phytomonomers

A novel thermotropic liquid-crystalline (LC) biocopolymer, poly{ trans -3-methoxyl-4-hydroxycinnamic acid (MHCA: ferulic acid)- co - trans -3,4-dihydroxycinnamic acid (DHCA: caffeic acid)}, was synthesized by a thermal acidolysis-polycondensation of MHCA and DHCA, efficiently catalyzed by Na 2 HPO 4 . When the MHCA composition of poly(MHCA- co -DHCA) was 60, 75, and 90 mol %, the copolymers showed a nematic LC phase although individual homopolymers such as polyMHCA and polyDHCA did not exhibit LC phase. Poly(MHCA- co -DHCA)s showed high molecular weight ( M w ) ranged between M n 2.6 × 10 4 to 3.7 × 10 4 and M w 8.2 × 10 4 to 13.1 × 10 4 , respectively, high glass-transition temperature ( T g ) with the range of 115 to 140 °C and high degradation temperature T 10 , from 315 to 356 °C. In the adhesive test of copolymers against the surface of carbon substrate, the copolymers showed high shear strength at fracture.