jp8b07930_si_001.pdf (2.58 MB)
Comparative Role of Chain Scission and Solvation in the Biodegradation of Polylactic Acid (PLA)
journal contribution
posted on 2018-09-25, 00:00 authored by Aleena Alex, Nirrupama Kamala Ilango, Pijush GhoshThe
molecular mechanism behind the process of biodegradation and
consequently the loss in mechanical properties of polylactic acid
(PLA) requires detailed understanding for the successful designing
of various technological devices. In this study, we examine the role
of free water and chain scission in this degradation process and quantify
the mechanical properties of pristine and nanoparticle-reinforced
PLA as it degrades over time. The in situ mechanical response of the
degrading polymer is determined experimentally using nano-dynamic
mechanical analysis (nanoDMA). Water present in the polymer matrix
contributes to hydrolysis and subsequent scission of polymer chains.
Water in excess of hydrolysis, however, alters the load transfer mechanism
within the polymer chains. Molecular mechanism study applied in this
work provides detailed insights into the relative role of these two
mechanisms, (i) chain scission and (ii) solvation, in the reduction
of mechanical properties during degradation. Functional groups such
as ester (−COO−) and terminal acid (−COOH) interact
with water molecules leading to the formation of water bridges and
solvation shells, respectively. These are found to hinder the load
transfer between polymer chains. It is observed that, compared to
scission, solvation plays a more active role in the reduction of mechanical
properties of degrading PLA.