Systematic Study of Thermal and (Bio)Degradable Properties of Semiaromatic Copolyesters Based on Naturally Occurring Isosorbide

Abstract

Here we present a series of copolyesters of poly­(butylene terephthalate) (PBT) with the renewable building block isosorbide (1,4:3,6-dianhydro-d-glucitol, IS), designated PBIT. The aim of this work is to systematically elucidate how the inherent properties (reactivity, structural asymmetry, structural rigidity, and hydrophilicity) of IS would affect the synthesis and thermal/(bio)­degradable performance of PBIT copolyesters. The target copolyesters containing 0–50 mol % IS units were successfully synthesized by melt polycondensation and were afforded in fully random microsequential structures. Their number-average molecular weights and intrinsic viscosities are in the ranges of 22 400–31 000 g/mol and 0.5–0.65 dL/g, respectively. The thermal properties determined by differential scanning calorimetric analysis firmly confirmed the remarkable T g-enhancing effect of IS. Comprehensive degradation study further revealed that IS incorporation promotes remarkable hydrolytic degradation in a relatively harsh acidic environment at high temperature (80 °C), but maintains excellent stability in a neutral hydrolytic and enzymatic environment (with porcine pancreatic lipase) at low temperature (37 °C). The synergistic effects of IS incorporation on thermal properties and degradability are dependent on degrading conditions. The results shown in this work are expected to give some insights regarding property improvement of the existing semiaromatic polyesters via copolymerization, as well as consideration of suitable working conditions for these polymers.

Thermal Stability of Bio‐Based Aliphatic‐Semiaromatic Copolyester for Melt‐Spun Fibers with Excellent Mechanical Properties

“…This indicates that the incorporation of LA units made the thermal‐mechanical properties of the PETLAs fibers exhibited better flexibility. [ 40,41 ] The glass transition behavior of PETLAs fibers amorphous phase decreased with the increase of LA units, and the Tg decreased from 65 to 60 °C. The correlation between T g and LA content was basically consistent with DSC analysis results in Figure 2.…”

Low‐crystallinity to highly amorphous copolyesters with high glass transition temperatures based on rigid carbohydrate‐derived building blocks

“…35 Our previous study regarding the (bio)degradability of terephthalic acid-based copolyesters showed that the presence of IS moieties enhances the hydrolytic degradation of the polymers to a certain extent, yet insignificantly influences their biodegradation properties. 23 For PBIF copolyesters, the crystallinities are much inhibited which, together with the high hydrophilicity of the materials, might result in degradable polyesters with enhanced thermal properties. To evaluate the degradation performance of the synthesized copolyesters, film samples of PBF homopolyester and PBIF copolyesters containing 7, 17, 27 and 51 mol% of IS were prepared and investigated under neutral hydrolytic, acidic hydrolytic and enzymatic degradation environments.…”

“…PP enzyme comes from animal pancreas after crystallization and has been frequently employed for biodegradation assay of polyesters. 23,36,37 Recently, a number of studies have shown that cutinase exhibits high efficiency for depolymerizing aliphatic or aromatic polyesters, [38][39][40] which significantly reduces the observation duration of enzymatic degradation experiments. The mechanism of both enzymes for degrading polyesters is generally believed to be via ester bond scission by a nucleophilic substitution process.…”

“…The mechanism of both enzymes for degrading polyesters is generally believed to be via ester bond scission by a nucleophilic substitution process. 23,41 The biodegradation results obtained under the catalysis of the two types of enzymes were apparently different. The biodegradation of PBIF in the presence of PP enzyme was closely correlated with IS content.…”

“…We recently have systematically investigated such a synergistic effect by incorporating IS units progressively into PBT or poly(butylene succinate). 23,24 Crystallinity is known to be a key factor determining the biodegradability of plastics. A high crystallinity of polymers, meaning a dense and ordered packing of macromolecules, tends to prevent fast diffusion of water into the inner part of the plastics.…”