Study of the transesterification of a main-chain mesomorphic polyester by small-angle neutron scattering

Abstract

The phenomenon of transesterification of a mesomorphic polyester is investigated in the isotropic and the nematic phase using small-angle neutron scattering (SANS). In the isotropic phase, the kinetic experiment results are in good agreement with the theoretical predictions of Benoit et al. for the determination of rate constant and activation energy of the transesterification process. In the nematic phase, SANS in the intermediate scattering vector range is not sensitive to the transesterification. This is perhaps due to the cylindrical shape adopted by the polymer chain. The results are discussed as a function of the molecular weight for two different spacers.

Rates of transesterification in epoxy–thiol vitrimers

“…In Leibler's case, 22 the similar analysis gives DG E 100 kJ mol À1 (or 45k B T at room temperature) for the TBD catalyst at 5 mol%, and DG E 83 kJ mol À1 (or 34k B T) for the zinc acetate catalyst also at 5 mol%. It is also interesting to compare with the activation energy of the straight ester-ester bond exchange without any catalyst added, reported in the old papers, 53,54 with values DG E 155 kJ mol À1 , evidently not very far from our EDDT result.…”

Rates of transesterication in epoxy-thiol vitrimers

“…In Leibler's case, 22 the similar analysis gives ∆G ≈ 100 kJ/mol (or 45k B T at room temperature) for the TBD catalyst at 5 mol%, and ∆G ≈ 83 kJ/mol (or 34k B T ) for the zinc acetate catalyst also at 5 mol%. It is also interesting to compare with the activation energy of the straight ester-ester bond exchange without any catalyst added, reported in the old papers, 53,54 with values ∆G ≈ 155 kJ/mol, evidently not very far from our EDDT result.…”

Fully Biobased Vitrimers from Glycyrrhizic Acid and Soybean Oil for Self-Healing, Shape Memory, Weldable, and Recyclable Materials

“…In this paper, we report on the preparation of fully biobased vitrimers from epoxidized soybean oil (ESO) and natural glycyrrhizic acid (GL) based on the transesterification reactions. 31 GL is a natural triterpene saponin found mainly in licorice roots and has been widely applied as food sweeteners and medicinal ingredients. 32−35 It has a rigid hydrophobic triterpenoid and a hydrophilic diglucuronic unit (Figure 1), which allow GL to be easily incorporated into the biocompatible self-assembled materials.…”

“…Therefore, we find it necessary to develop fully biobased vitrimers using renewable resources without excessive chemical modification before curing. In this paper, we report on the preparation of fully biobased vitrimers from epoxidized soybean oil (ESO) and natural glycyrrhizic acid (GL) based on the transesterification reactions …”