Designing Hydrolysis-Resistant Ti/Zn Bimetallic Catalyst Based on the Coordination Activation Mechanism to Synthesize High Molecular Weight Ppet

Abstract

The high molecular weight poly (1,5-pentene terephthalate) (PPeT) synthesis and its molecular weight distribution control are still challenging, and one of the critical problems is the lack of efficient catalysts. Based on the coordination activation mechanism, a heavy metal free, hydrolysis-resistant and 1,5-Pentanediol (1,5-PeDO) soluble Ti/Zn bimetallic catalyst (TZC) has been synthesized and characterized. The Ti/Zn bimetallic active center increases catalyst electronegativity to promote the esterification process, and the diol-metal alkoxide structure increases the production of oligomer ligands, which can effectively improve transesterification efficiency. The optimal polycondensation reaction temperature for PPeT synthesized with TZC can be reduced to 230 °C, with an average reaction rate of 90.33 g·mol-1·min-1. The number average molecular weight of PPeT can be increased to 3.02 × 104 g·mol-1, and the polymer dispersive index (Ð) can be as low as 1.90. As the number average molecular weight increases, PPeT has a tensile strength of 29.80 MPa and an elongation at break of 16.39%. More importantly, TZC retains excellent catalytic activity after treatment with boiling water and has significantly improved hydrolysis resistance and storage stability. TZC can significantly increase the molecular weight and melt viscosity of PPeT, giving it the potential for a wider range of applications in plastics and fiber fields.

Keywords: Poly (1, 5-pentylene terephthalate), Ti/Zn catalyst, bimetallic active center, hydrolysis resistance, heavy metal free