Polymers from Fatty Acids: Poly(ω-hydroxyl tetradecanoic acid) Synthesis and Physico-Mechanical Studies

This Article describes the synthesis and physicomechanical properties of bioplastics prepared from methyl omega-hydroxytetradecanoic acid (Me-omega-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 (2 h at 200 degrees C under N-2, 4 h at 220 degrees C under 0.1 mmHg). Poly(omega-hydroxytetradecanoate), P(omega-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(omega-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(omega-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(omega-OHC14) with M-w 53K-78K showed a brittle-to-ductile transition. In contrast, P(omega-OHC14) with M-w 53K undergoes brittle fracture. Increasing P(w-OHC14) M-w above 78K resulted in a strain-hardening phenomena and tough properties with elongation at break similar to 700% and true tensile strength of similar to 50 MPa. Comparisons between high density polyethylene and P(omega-OHC14) mechanical and thermal properties as a function of their respective molecular weights are discussed.