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Polycondensation for PLA synthesis is widely used due to its cost-effectiveness, but it often leads to low molecular weight PLA. To address this limitation, researchers have explored different catalysts, with the stannous chloride and p-toluene sulfonic acid combination being a popular choice. However, this method typically yields PLA with a MW of no more than 35000 g/mol, which is unsuitable for commercial applications. In contrast, ring-opening polymerization is considered the most effective method for synthesizing high MW PLA, despite its complexity and cost. Industrial-scale production predominantly employs ROP due to its capability to produce high MW PLA. The use of stannous octoate as a catalyst for ROP has shown promise in synthesizing higher MW PLA. However, its sensitivity to water limits its use in polycondensation, where stannous chloride is commonly employed but is not capable of synthesizing high MW PLA. This study explores the use of stannous octoate for the synthesis of high MW PLA with higher yield. [ABSTRACT FROM AUTHOR]

The ring opening polymerization (ROP) kinetics of L-lactide was studied in bulk at 150, 160, and 180 °C using stannous octoate [Sn(Oct)2] catalyst and 1-pyrene butanol co-catalyst. The effect of different parameters namely, time and co-catalyst to catalyst ratio was studied on the properties of polylactide. The experimental results showed high conversion of L-lactide. The kinetics of L-lactide ROP follows the co-ordination insertion mechanism. The experimental results obtained were studied to account for the reversible activation, propagation, termination, and validated by modeling using MATLAB. The model developed successfully predicts the monomer conversion and the kinetics of L-lactide ROP. [ABSTRACT FROM AUTHOR]

Series of poly(L-Lactide) diols with molecular weights (Mn) in 2,069–4,811 g mol−1were synthesized fromL-Lactide using stannous octoate catalyst and 1,4-butanediol chain extender. Operating conditions, i.e., temperature, catalyst concentration, chain extender concentration, and reaction time, were optimized. Maximum monomer conversion andMnwere observed at 0.5 mol% SnOct2and 1.0 mol% 1,4 butanediol (BDO) at 145°C. Poly(L-Lactide) diols were analyzed by Fourier transform infrared, proton nuclear magnetic resonance, end-group analysis, and X-ray diffraction techniques. Fourier transform infrared confirmed the formation of poly(L-Lactide) diols. Poly(L-Lactide) diols’ % degree of crystallinity was determined by X-ray diffraction.Mnwas calculated by proton nuclear magnetic resonance and end-group analysis. [ABSTRACT FROM PUBLISHER]

The bulk ring-opening copolymerization of l-lactide with ε-caprolactone was conducted at 140 °C. The reaction was catalyzed with stannous octoate and initiated using hydroxyethyl methylacrylate to produce acrylated biomass macromonomers. The effects of varying monomer compositions as well as polymer chain lengths on the copolymerizations were experimentally investigated. A mathematical model is developed considering reversible initiation, propagation, chain transfer, and transesterification reactions. The diffusion control associated with polymer chain length is considered in the model. The model successfully predicts monomers conversions, number-average molecular weights, polydispersity index values, and cumulative copolymer compositions for ring-opening copolymerizations of l-lactide with ε-caprolactone. [ABSTRACT FROM AUTHOR]

The ring opening polymerization of L-lactide was studied in bulk using stannous octoate as initiator. In some experiments, triphenylphosphine, a Lewis base was also used as co-initiator. The polymerization was carried out at 130°C up to 29 h. The monomer was used after recrystallizing three times with dry toluene. Experiments were carried out using a wide range of monomer to initiator ratio. The averages and distributions of molar masses of resulting PLA have been determined by means of size exclusion chromatography, SEC. It is shown that the (mode, process) procedure of dispersion of the catalyst in polymerization system affects the molar mass distribution of the product as is evidenced by the bimodality or even trimodality observed in the SEC chromatograms. [ABSTRACT FROM AUTHOR]

Laboratory- and pilot-scale racemic polylactides (PLA50) were synthesized in the presence of stannous octoate (SnOct2) or zinc-metal as initiators in the absence of alcohol. The resulting polymers were processed by compression molding or injection molding depending on the batch scale. The hydrolytic degradation of compression-molded samples selected to be comparable was investigated first in order to show the influence of the initiator system. Differences in water uptake were found between PLA50–Zn (zinc-metal initiation) and PLA50–Sn (SnOct2 initiation), PLA50–Zn being much more hydrophilic. PLA50–Sn exhibited a slower molecular weight decrease and delayed onsets of weight loss, release of acidity and stereocomplex formation, with respect to PLA–Zn. The concentration in residual tin in PLA50–Sn increased from 306 to 795 ppm during aging. In the case of PLA50–Zn the residual metal remains constant at ca. 40 ppm. In a second series of experiments, high molecular weight PLA50 different in characteristics and in initiator, synthesized under pilot-scale, were compared. The effects of the initiator on the degradation of the polymers well agreed with laboratory-scale findings, differences in hydrophobicity being enlarged by the up scaling. PLA50–Sn polymers appeared much more degradation resistant than PLA50–Zn ones. Contributions of the other characteristics (e.g. molecular weight, purity, stereoregularity, processing) were shown to be important as well. [Copyright &y& Elsevier]

A functional cyclic carbonate, 5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one (MBC), was utilized in the synthesis of novel poly(ester-carbonates) containing pendent carboxylic acid groups. Copolymers with ε-caprolactone (CL) and L-lactide (LLA) were synthesized by ring-opening polymerization (ROP) using either an Al-alkoxide (solution) or Sn(Oct)2-alcohol (bulk) initiating system. Analysis of the copolymers revealed a random distribution of the comonomer units along the polymer chain. The copolymers exhibited amorphous character at low MBC incorporations despite the crystalline nature of homo-poly(ε-caprolactone) (PCL) and homo-poly(L-lactide) (PLLA). Removal of the benzyl protecting group by hydrogenolysis yielded carboxylic acidfunctional copolymers. It was observed that the benzyl ester group of MBC became susceptible to transesterification reactions at ROP temperatures ≥ 135°C, and the corresponding copolymers were insoluble in both organic and aqueous solvents. It is proposed that carboxylic acid functionality will allow an improvement in the biodegradability and physical properties of PCL and PLLA and possibly improve their utility for biomedical applications such as time-released drug delivery. Moreover, polymerization of comonomers at high temperature may present a pathway toward the synthesis of new biodegradable hydrogels. [ABSTRACT FROM AUTHOR]