Bio-based, amorphous polyamides with tunable thermal properties

The aim of this work is to synthesize amorphous polyamides from renewable monomers derived from vegetable oils and sugars. By making use of the odd-even effect to hamper intermolecular hydrogen bonding, combined with either the incorporation of dimerized fatty acid monomers or isoidide diamine (IIDA) produced from fructose, the crystallization of the polyamides was suppressed considerably. Polyamides based on the dimerized fatty acid showed T_g values below 10 °C. The introduction of the isoidide-based diamine enhanced the rigidity of the polymer backbone, which enabled the synthesis of amorphous polyamides with T_g values up to 100°C. For both series incomplete reaction has been observed as both end groups, i.e. amine and carboxylic acid, were detected in ¹H NMR. This results in M_n values from ¹H NMR for the fatty acid-based series in the range of 4700-21,000 g mol^-1. The M_n values measured by SEC for the IIDA-based were in the range of 3000-10,700 g mol^-1. The broad range of T_g values found for these materials in combination with their relatively low molecular weights and the corresponding large amount of reactive end-groups make them suitable for application in coatings, composites, or soft-touch surfaces.