Pure and Applied Chemistry

Abstract: 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 Na₂HPO₄. 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 × 10⁴ to 3.7 × 10⁴ and M_w 8.2 × 10⁴ to 13.1 × 10⁴, respectively, high glass-transition temperature (T_g) with the range of 115 to 140 °C and high degradation temperature T₁₀, 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.