Ring-Opening Polymerization ofl,l-Lactide: Kinetic and Modeling Study

Abstract

Ring-opening polymerization of L,L-lactide with various amounts of catalyst, 2-ethylhexanoic acid tin(II) salt, and cocatalyst, 1-dodecanol, at 130 °C in bulk is examined. Monomer-to-catalyst and cocatalyst-to-catalyst molar ratios were changed from 500 to 4000 and from 1 to 600, respectively. In agreement with previous literature, the catalyst concentration is affecting the reaction rate, whereas OHbearing species (such as cocatalyst and impurities) are controlling both reaction rate and polymer molecular weight. A model implementing a living kinetic scheme is first developed and validated by comparison with the experimental results. The rate coefficients of the main reactions (activation, propagation, and reversible chain transfer) have been evaluated. Finally, to predict with accuracy the broadening of the molecular weight distribution, we introduce ester interchange reactions, so-called "transesterifications", into the kinetic scheme, and the corresponding rate coefficient is evaluated.

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

“…Note that at high monomer conversions and high polymerization temperatures (i.e., higher than 130 °C), scission and trans‐esterification reactions become important, resulting in a decrease of and an increase of polydispersity index. On the other hand, at low polymerization temperatures, their contribution to the molecular weight developments is not significant . The experimentally measured values of the polydispersity index (i.e., ) varied from 1.0 to 2.6.…”

“…Thus, it is of paramount importance to precisely know their concentration since they largely affect the polymerization rate and molecular weight of PLLA . In order to ensure accurate control of the concentration of all possible sources of hydroxyl bearing species, the polymerization is usually carried out in the presence of a known concentration of an alcohol (i.e., a co‐initiator), which is actually the dominant source of hydroxyl groups . In the present study, the only source of hydroxyl groups was the residual water moisture present in the polymerization recipe.…”

Multiple strategies to produce lipophilic nanoparticles leaving water-soluble poly(HPMA)

“…The GPC and MALDI-TOF data are in a good agreement, and we observed that the most abundant species are the macromonomers with an even number of lactoyl units (as expected, LT was a dimer). 27 26 The same procedure that was used to produce and verify the effective HPMA-LA 8 was applied for the lower MW macromonomers, specifically, HPMA-LA 4 and HPMA-LA 6 .…”

l-Lactide polymerization catalysed by tin(ii) 2-ethyl-hexanoate. A deeper look at chain transfer reactions

“…The experimental evidence of the exchange reactions is broadening of molar mass distribution which can be detected by Size Exclusion Chromatography (SEC) at the late polymerization stages. [7][8][9][10][11] Penczek, et. al. conducted kinetic studies and numerical modelling of the segmental exchange reactions, leading to the introduction of a selectivity/reactivity parameter for this system.…”