Acetalised Galactarate Polyesters: Interplay between Chemical Structure and Polymerisation Kinetics

Abstract

In spite of the progress that has made so far in the recent years regarding the synthesis of bio-based polymers and in particular polyesters, only few references address the optimisation of these new reactions with respect to conversion and reaction time. Related to this aspect, we here describe the transesterification reaction of two different acetalised galactarate esters with a model aliphatic diol, 1,6-hexanediol. The kinetics of these two apparently similar reactions is compared, with a focus on the conversion while varying the concentration of a di-butyltin oxide catalyst (DBTO), respectively, the used N2 flow-rate. During the first stage of polymerisation, the molecular weight of the end-products is more than doubled when using a 250 mL/min flow as opposed to an almost static N2 pressure. Additionally, the resulted pre-polymers are subjected to further polycondensation and the comparison between the obtained polyesters is extended to their thermal, mechanical and dielectrical characterisation. The influence of the acetal groups on the stability of the polyesters in acidic conditions concludes the study.

Radical Formation in Sugar-Derived Acetals under Solvent-Free Conditions

“…The published findings were never translated to solvent-free methods and were never widely explored for the whole class of similar sugar-derived molecules. In addition, a similar dispersity trend has also been reported for polyester synthesis in the melt, which is less thermally demanding, using GalXH and GalXMe monomers, where broadening of the dispersity with GalXH was also observed and was attributed to transesterification [16]. This similarity suggests that the observed trend could be valid for all solvent-free polycondensations involving GalXH.…”

Enzymatic bulk synthesis, characterization, rheology, and biodegradability of biobased 2,5-bis(hydroxymethyl)furan polyesters

“…Furthermore, the catalytic reaction mechanism of DBTO is proposed to proceed via Sn coordination of the ester group or an exchange/insertion pathway of the diol. 48 Hence, since the mechanism is not fully understood, the effect of the size of the dimethyl ester cannot be contested.…”

Short-Loop Chemical Recycling via Telechelic Polymers for Biobased Polyesters with Spiroacetal Units

“…This observed conversion threshold indicated that the polyacetalization reached the equilibrium condition. , Further optimization of the reaction conditions was not attempted in this work. The molecular weight of the final crude r -PNVT 30 (crude, Figure S16A, SI) could be calculated as ∼8.1 kg/mol based on the conversion according to the Carothers equation (eqs S17 and S18, SI) . The repolymerization of the longer telechelic polymer obtained after hydrolysis of PNVT-5 (i.e., t -PNT 7.5 ) was carried out similarly.…”

“…The molecular weight of the final crude r-PNVT 30 (crude, Figure S16A, SI) could be calculated as ∼8.1 kg/mol based on the conversion according to the Carothers equation (eqs S17 and S18, SI). 60 The repolymerization of the longer telechelic polymer obtained after hydrolysis of PNVT-5 (i.e., t-PNT 7.5 ) was carried out similarly. After 17 h, the conversion of the aldehyde end groups reached the maximum The molecular weight of the initial polymers could not be estimated by using the same Carothers method (because the initial polymers were not made by coupling the end groups), but it could be estimated by 1 H NMR spectroscopy using end-group analysis (Figure S19, SI), which showed a similar range of estimated molecular weights compared to the repolymerized polymers (Table S6, SI).…”