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6
Shape Memory Systems with Biodegradable Polyesters
József Karger Kocsis and Suchart Siengchin

6.1
Introduction

Growing environmental concerns and public awareness of the necessity of
sustainable growth trigger the present research and development (R&D) works
to produce and use biodegradable polymers, especially those which are derived
from renewable resources. Environmental issues are mostly related to dwindling
fossil fuels (crude oil, natural gas) as feedstock in petrochemistry, carbon dioxide
emission of the latter, and the problem of disposal of plastic waste. Bio-based,
biodegradable polymers are promising candidates that could overcome these
problems when they are capable of replacing the competing petroleum-based
counterparts. Biodegradable polymers decompose to carbon dioxide, water,
and biomass under aerobic conditions, whereas the product range is enlarged
by methane when decomposition takes place under anaerobic conditions. The
decomposition itself is a rather complex process involving hydrolysis, micro-
biological attack, enzymatic cleavage, and thermal degradation. Nevertheless,
the controlling ester cleavage is mostly due to enzymatic attack [1]. Bio-based
polymers originate from biomass (e.g., thermoplastic starch), synthesized by
microorganisms (polyhydroxyalkanoates, PHAs, of bacterial origin) or pro-
duced by biotechnological routes from suitable monomers (e.g., polylactic acid,
PLA, synthesized by ring-opening polymerization from lactide). PHAs are real
biopolymers, in fact, because they have been produced by living organisms.
Note that biodegradable polymers can be produced from petrochemical sources
as well. Poly(ε-caprolactone) (PCL), polyesteramides, aliphatic, and aromatic
copolyesters belong to the “petro-based” biodegradable polymers. The above
listing makes clear that the major part of biodegradable polymers are polyesters,
and in particular, aliphatic polyester versions. A further peculiar feature of
aliphatic polyesters is that practically all of their monomers can be synthesized
from renewable resources [1].
Shape memory polymers (SMPs) and composites thereof are emerging smart
materials in different applications, especially in biomedical, aerospace, and con-
struction engineering fields. SMPs may adopt one (dual-shape), two (triple-shape),

Biodegradable Polyesters, First Edition. Edited by Stoyko Fakirov.
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA. Published 2015 by Wiley-VCH Verlag GmbH & Co. KGaA.