An Experimental and Theoretical Investigation of the Ring‐Opening Polymerization of L,L‐Lactide

Abstract

A comprehensive mathematical model was developed based on a detailed kinetic mechanism to predict the dynamic evolution of monomer conversion and molecular weight averages. The predictive capabilities of the mathematical model are demonstrated by a direct comparison of model predictions with literature and new experimental data on monomer conversion as well as number and weight average molecular-weight of PLLA. The effects of monomer to initiator molar ratio and polymerization temperature on the polymerization rate and average molecular weight properties of polylactide were experimentally determined and compared with model predictions. For this reason, high molecular weight polylactides were synthesized in melt via the ring-opening polymerization of L,Llactide, in the presence of stannous octoate.

Dynamic Monte Carlo Simulation of thel,l‐Lactide Ring‐Opening Polymerization

“…The above kinetic mechanism is sufficiently general and includes a number of reaction steps, namely, initiator activation, chain initiation, propagation, chain transfer reactions (i.e., chain transfer to water, to octanoic acid, and to monomer), cyclization, esterification, transesterification, and chain scission reactions as well as reactions leading to the formation of specific end‐groups . This mechanism is simplified compared with the one presented in a previous publication of our group and in accordance to similar work appearing in the open literature for the ROP of l,l ‐lactide in the presence of coinitiators. In addition, the kinetic rate parameters (see Table ) were reduced in number by considering equal reactivity of the chain transfer reactions.…”

“…In this section the predictive capabilities of the proposed kinetic model are demonstrated by a direct comparison of model predictions with experimental measurements on monomer conversion and number and weight average molecular weights, reported by Pladis et al In Table , the numerical values of all the kinetic rate constants used in the present model simulations are reported. In all simulated cases, the initial water concentration was estimated to be equal to 1.25 × 10 −4 g H 2 O/g l,l ‐lactide.…”

“…Based on a series of previous investigations, it was assumed that the ring opening polymerization of l,l ‐lactide in the presence of Sn(Oct) 2 followed a coordination insertion mechanism, comprising the following set of elementary reactions…”

“…The validity of the implemented kinetic model and the accuracy of the produced simulation results are assessed via a direct comparison with theoretical predictions of monomer conversion and average molecular properties by the method of moments as well with available experimental data by our group . Among the novelties of the present work are the stochastic prediction of the detailed molecular characteristics of the polymer, the implementation of a comprehensive and detailed kinetic mechanism as well as the comparison of the theoretical predictions with experimental measurements from the characterization of high purity and high molecular weight PLLA polymers.…”

Multiscale modeling of poly(lactic acid) production: From reaction conditions to rheology of polymer melt

“…Last but not least, group of Kiparissides developed probably kinetically most complex model for L,L-lactide ROP in the presence of water traces, which included several reaction steps neglected in other works (intramolecular transesterifications, formation of cyclic chains, ester end-group formation and others). The model was successfully applied to predict conversion and average molar masses in the case of polymerizations initiated by water [27] and various polyalcohols [28]. Recently, the model was extended by Monte Carlo simulation in order to predict full molar mass distribution (MMD) of PLA [29].…”