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4
Synthesis, Properties, and Mathematical Modeling of
Biodegradable Aliphatic Polyesters Based on 1,3-Propanediol
and Dicarboxylic Acids
Dimitris S. Achilias and Dimitrios N. Bikiaris

4.1
Introduction

4.1.1
Aliphatic Polyesters

Biodegradable polymers have attracted considerable interest as they can be the
solution to environmental pollution associated with conventional and nondegrad-
able polymers that are used extensively in many applications. Most of the polymers
used, such as polyethylene, polypropylene, and polystyrene are hydrophobic mate-
rials resistant to biodegradation because their repeating units cannot be degraded
to smaller parts by microorganisms. Even though polyethylene can be procured
today from monomers deriving from renewable resources in order to become
−1
biodegradable, its molecular weight should be reduced to 300–500 g mol .On
the contrary, aliphatic polyesters have ester bonds which, due to their mobility,
can be cleaved by enzymes such as lipases, with the generated chain fragments
finally dissolving in the surrounding water phase. The degradation proceeds either
at the surface (homogeneous) or within the bulk (heterogeneous) and is controlled
by a wide variety of compositional and property variables, for example, matrix
morphology, chain orientation, chemical composition, stereochemical structure,
sequence distribution, molecular weight and distribution, the presence of residual
monomers, oligomers and other low-molecular-weight products, size and shape
of the specimen, and the degradation environment, for example, presence of mois-
ture, oxygen, microorganisms, enzymes, pH, and temperature [1, 2]. The enzy-
matic degradation of polymers generally proceeds in one of types of the chain
cleavages: endo-cleavage (random scission) or exo-cleavage (proceeding from the
chain terminal). Which degradation mechanism dominates depends on both the
structure of the polyester and the environment.
Aliphatic poly(alkylene dicarboxylate) polyesters (APDs) are among the
biodegradable polyesters of maximum interest and they can be prepared
by biomass-derived monomers (renewable resources), petroleum-derived
monomers (nonrenewable resources), or a mixture of both. Examples of APDs

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