Hyperbranched polyesters by polycondensation of fatty acid-based ABn-type monomers

TL;DR

This study presents a method to synthesize hyperbranched polyesters from vegetable oil-derived ABn-type monomers, demonstrating tunable properties and potential for bio-based polymer applications.

Contribution

It introduces a new approach to produce hyperbranched polyesters from bio-sourced monomers with controlled structure and properties, using simple derivatization and polycondensation techniques.

Findings

Achieved molar masses of 3000-10000 g/mol with dispersities 2-15.

Degree of branching ranged from 0.07 to 0.45.

Polyesters exhibited amorphous or semi-crystalline behavior with Tg from -33 to 9°C.

Abstract

Widely available vegetable oils were readily derivatized into chemically pure ABn-type monomers (n = 2 or 3). Their polymerization led to unprecedented hyperbranched polyesters. Four different AB2/AB3-type monomers bearing one A-type methyl ester and two or three B-type alcohol functions were purposely synthesized via two elementary steps, i.e. epoxidation of the internal double bond of the vegetable oil precursors followed by ring-opening of the epoxy groups under acidic conditions. The polycondensation of these bio-sourced monomers was performed in bulk, in the presence of an appropriate catalyst, giving access to modular hyperbranched polyesters with tunable properties. Among the catalysts tested, zinc acetate, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and sodium methoxide proved the most effective, allowing the achievement of molar masses in the range 3000--10 000 g mol--1 and dispersities varying from 2 to 15, depending on the initial conditions. The degree of branching, DB, as determined by 1H NMR spectroscopy, was found to be between 0.07 and 0.45. The as-devised hyperbranched polyesters displayed either amorphous or semi-crystalline properties, as a function of the selected AB2/AB3-type initial monomers, with a glass transition temperature, Tg, ranging from --33 to 9 {\textdegree}C and a decomposition temperature at 5 wt% of the sample, Td5%, varying from 204 to 340 {\textdegree}C.