Synthesizing Novel Biobased Molecules for Enhanced Polymer Properties
Biobased molecules are promising building blocks for polymer synthesis as they can provide new and unique properties that are unavailable from conventional petrochemicals. The overarching goal of this research is to explore the chemistry of muconic acid, an unsaturated diacid that is produced from biomass by fermentation using metabolically-engineered bacteria or yeast. A cyclic unsaturated monomer, CH1DA, is produced from a Diels-Alder reaction between trans,trans-muconic acid and ethylene. This monomer is then incorporated as a novel biobased monomer for tuning the properties of Nylon 6,6. While adipic acid and hexamethylenediamine are polymerized in equal proportions to produce PA6,6, varying molar percentages of the adipic acid can be replaced by the novel monomer (10 mol% to 25 mol%) to produce a biobased polyamide. Differential Scanning Calorimetry (DSC) on the new polymer showed the melting temperature decreased compared to conventional nylon 6,6, thereby increasing the processibility of the new biobased polymer. Dynamic Mechanical Analysis (DMA) indicated that mechanical properties were not sacrificed on inserting this cyclic molecule as an increased glass transition temperature and higher storage modulus were observed. Water uptake tests showed increased hydrophobicity of the biobased polyamide, which is desired since nylons are susceptible to water absorption that degrades the mechanical properties of the polymer.
While CHDA (1,4-cyclohexanedicarboxylic acid) is commercially available and used in polyester synthesis, our novel biobased monomer, CH1DA, contains an unsaturated double bond that can be used for polyamide synthesis. Due to the presence of an unsaturated bond in the cyclic monomer, it can be functionalized further to impart different enhanced properties, such as flame retardance. As a proof of concept, phosphorous-based flame retardant molecules will be grafted onto the monomer to produce a novel biobased polymer with enhanced flame-retardant properties. The resulting polymer will be characterized by various thermal and mechanical tests.