Solution-based synthesis of a four-arm star-shaped poly(L-lactide)

Abstract

The mechanical properties of biocompatible poly(L-lactide) (PLA) could be dramatically enhanced by cross-linking and interesting network structures might be achieved via the formation of branched and star-shaped structures prior to such cross-linking. However, the synthesis of a four-armed starshaped PLA is limited to bulk melt polymerization at relatively high temperatures that may degrade the monomer and render the reaction kinetics difficult to control. In this work, a solution-based polymerization approach is introduced with dimethylformamide as the solvent for the initiator and all other reactants. Varying the reactant concentrations and reaction temperature, four-arm PLA star structures were produced in solution and their properties were analyzed. The progress of the polymerization reaction was studied using the 1 H NMR and Fourier transform infrared spectroscopy. The quantitative evaluation of the monomer conversion was discussed on theoretical basis. The thermal properties and the crystallinity of the product polymers were evaluated using differential scanning calorimetry. Results indicate polymerization and cross-linking of the four-armed PLA were successful. The introduced solution-based method could open venues for better controlled and more economic reactions of star-shaped and cross-linked PLA.

Biodegradable Star-Shaped Poly(lactic acid): Synthesis, Characterization and Its Reaction Kinetics

“…4, when the reaction time exceeded 5 h, the number average molecular weight (M n ) increased, but the decrease of L -lactide concentration led to a decrease of the reaction rate with the reaction time longer. At the same time, with the increase of reaction time, the viscosity of the reaction system increased, which resulted in by-products such as water difficult to be expelled and molecular weight distribution (PDI) wider [32,33]. In addition, as the reaction time increased, for the target product, the molecular weight was much higher than the theoretical molecular weight, which meant that PLA chains had reacted with more small molecules and would increase the steric hindrance of molecular microstructure resulting in hinder the further end-functionalization reaction of the target product [13].…”

Branched Polyurethanes Based on Synthetic Polyhydroxybutyrate with Tunable Structure and Properties

“…The peak observed at 1381 cm −1 on FTIR spectra of R,S-PHB (Figure S1) was ascribed as banding deformation vibration of CH 3 according to Eldessouki et al [13]. Its presence was noted on FTIR spectra of branched PURs based on R,S-PHB at 1380 cm −1 .…”

Controlled organocatalyzed d,l-lactide ring-opening polymerizations: synthesis of low molecular weight oligomers

“…16 Alternatives such as strongly basic amine organocatalysts are favored, particularly 4-dimethylaminopyridine (DMAP), which was pioneered by Nederberg et al 17 DMAPmediated ROP is used for one-pot PLA polymerizations and conjugations, 18 diblock or triblock copolymerizations with lactide as a rst or second block, [19][20][21] graing lactide to cellulose polymer bers, 22 and synthesizing star-shaped/cross-linked PLA networks. 23 PLA has also been exploited to tether and release drugs from linear polymers and hydrogel depots. 24 Drug tethers are typically low molecular weight oligo(lactide) composed of fewer than seven lactide repeat units to avoid crystallinity and associated challenges with solubility and control over degradation rates.…”