Chain-end scission in acid catalyzed hydrolysis of poly (d,l-lactide) in solution

Shih, Chung

doi:10.1016/0168-3659(94)00100-9

Cited by 135 publications

(81 citation statements)

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“…In contrast, even a small number of random scissions cause a reduction in molecular weight. It has been reported that end scission may occur 100 times more frequently than random scission in PLA [1], in which case the results here indicate the degradation of molecular weight is due to random scission as opposed to end scission. It should be noted that for a very narrow molecular weight distribution, the effect of end scission is that M n reduces at the same rate as the monomer weight fraction increases in the polymer.…”

Section: Details Of the Computer Simulation Schemesupporting

confidence: 46%

“…During degradation, the ester bonds within polymer chains are cleaved due to the hydrolysis reaction in the presence of water. It has been suggested that both chain end scission and random chain scission occur [1] and mathematical models have been able to fit experimental data with assumptions of random scission [2][3][4], end scission [5], or a combination of both [6]. In random scission, every bond in a polymer chain is assumed to be equally susceptible to hydrolysis.…”

Section: Introductionmentioning

confidence: 99%

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Computer Simulation of Polymer Chain Scission in Biodegradable Polymers

Gleadall¹

2013

J Biotechnol Biomater

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Biodegradable polymers degrade due to the hydrolysis (chain scission) of the polymer chains. Two theories of hydrolysis are that 1) scissions occur randomly at any bond in chains, and 2) scissions occur in the final bond at chain ends. In this study, a simulation tool was developed to simulate both random chain scission and chain end scission. The effect of each type of scission was analysed. Random scissions were found to have over 1000 time's greater impact on molecular weight reduction than end scissions. For the degradation of poly lactic acid by random scission, it was found that M n must reduce to <5000 g/mol in order for a polymer to exhibit significant mass loss due to the diffusion of water-soluble short chains. In contrast, end scission was able to produce a significant fraction of water-soluble chains with little or no effect on M n . The production rate of water-soluble chains was linearly related to end scission but increase in an accelerated manner due to random scission. Molecular weight distributions were fitted to experimental data for the degradation of poly D-lactic acid.

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Section: Details Of the Computer Simulation Schemesupporting

confidence: 46%

Section: Introductionmentioning

confidence: 99%

Computer Simulation of Polymer Chain Scission in Biodegradable Polymers

Gleadall¹

2013

J Biotechnol Biomater

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“…Experimental evidence for which hydrolysis mechanisms are dominant is conflicting due to the number of factors that affect degradation and inconsistency between experiments. Shih [36] suggested that end scission is dominant with approximately 10 times the rate of random scission. However for a high molecular weight sample, a single random scission has a greater impact on molecular weight than 1000 end scissions so their experiment actually indicates that random scission controls the molecular weight reduction.…”

Section: Introductionmentioning

confidence: 99%

Degradation mechanisms of bioresorbable polyesters. Part 1. Effects of random scission, end scission and autocatalysis

Gleadall

Pan

Kruft³

et al. 2014

Acta Biomaterialia

117

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“…Since the bulk degradation of PLGA is trivial during the initial period, the drug release time, 24 hr in this study, is considerably shorter than the degradation lifetime of PLGA (Shih 1995;Hsu et al 1996). The polymer backbone may retain its integrity without significant degradation/dissolution.…”

Section: Resultsmentioning

confidence: 99%