Unexpected Strengthening of Polyamide 11 with Liquid Crystalline Oligomers of 2-Alkoxy-4-hydroxybenzoic Acids. 1

Abstract

Novel liquid crystalline (LC) oligomers of 2-alkoxy-4-hydroxybenzoic acids (5a−d) containing flexible side chains were produced, and their compatibilities with polyamide 11 (PA 11) were investigated. DSC and FTIR studies revealed variable interfacial adhesion between blended compounds. They indicated that oligomers with short or medium long alkoxy substituents (5a−c) have adhesion to PA 11 while the interactions between oligomers of 4-hydroxybenzoic acid (5e) or 2-octadecanyloxy-4-hydroxybenzoic acid (5d) and PA 11 were poor. FTIR spectra proved that oligomeric structures could self-associate and affect on the final mechanical properties of the polyamide. Strength of PA 11 in a three point bending test was increased by addition of only 1% of LC oligomers 5a−e to the matrix.