Polymers from fatty acids: Poly(co-hydroxyl tetradecanoic acid) synthesis and physico-mechanical studies

This chapter describes the synthesis and physicomechanical properties of bioplastics prepared from methyl-hydroxytetradecanoic acid (Me-ω-OHC14), a new monomer available by a fermentation process using an engineered Candida tropicalis strain. Melt-condensation experiments were conducted using titanium tetraisopropoxide (Ti[OiPr]₄) as a catalyst in a two stage polymerization (2h at 200 °C under N₂,4h at 220 °C under 0.1 mmHg). Poly(ω-hydroxytetradecanoate), P(ω-OHC1₄), M _W, determined by SEC-MALLS, increased from 53K to 110K as the Ti(OiPr)₄ concentration increased from 50 to 300 ppm. By varying the polymerization conditions (catalyst concentration, reaction time, second-stage reaction temperature) a series of P(ω-OHC14) samples were prepared with M_w values from 53K to 140K. The synthesized polyesters with M _w ranging from 53K to 140K were subjected to characterization by DSC, TGA, DMTA and tensile testing. Influences of P(ω-OHC14) molecular weight, melting point, and enthalpies of melting/crystallization on material tensile properties were explored. Cold-drawing tensile tests at room temperature for P(ω-OHC14) with M_W 53K to 78K showed a brittle-to-ductile transition. In contrast, P(ω-OHC14) with M_w 53K undergoes brittle fracture. Increasing P(ω-OHC14) M_W above 78K resulted in strain-hardening phenomenon and tough properties with elongation at break about 700% and true tensile strength about 50 MPa. Comparisons between HDPE and P(ω-OHC14) mechanical and thermal properties as a function of their respective molecular weights are discussed.