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2
Functional (Bio)degradable Polyesters by Radical
Ring-Opening Polymerization
Seema Agarwal

2.1
Introduction

Aliphatic polyesters represent an important class of biodegradable and biocom-
patible polymers used for various biomedical applications and as environmental
friendly materials for packaging, and so on. [1–4]. Well-established examples
of commercially available biodegradable aliphatic polyesters are either based on
cyclic ester monomers such as lactide, lactones, and glycolide, or bifunctional
diacid/diacid derivatives and diols. Anionic, cationic, metal, and enzyme-
catalyzed ring-opening polymerization (ROP) of cyclic esters give aliphatic
polyesters [5, 6]. Many different homo- and co-polyesters have been made
using the ROP method both for commercial and academic interests. These
aliphatic polyesters are hydrophobic with ester functionality in the backbone. For
introducing additional functionalities, which could be of interest for hydropho-
bicity modification or attachment of biomolecules, and so on, the syntheses
of the polyesters by ROP require the use of specially synthesized functional
cyclic esters such as α-and γ-substituted lactones or chemical derivatization of
presynthesized polyesters with polymer-analogous reactions [5b, 7]. Sometimes
protection–deprotection chemistry and special precautions are required during
synthesis of functional polyesters as functional groups could be sensitive to
the initiators used and/or ROP reaction conditions. The condensation reaction
of diols and diacids/diacid derivatives is another route for the formation of
aliphatic polyesters [8, 9]. This method has the advantage of availability of many
different types of diols and diacids/diacid derivatives not only petro-based but
also bio-based [10]. Different combinations of diols and diacids/diacid derivatives
provide a wide variety of property profiles to aliphatic polyesters but the method
has the limitation in getting high-molar-mass polyesters.
Recently, there has been fast progress in the use of radical chemistry for making
polyesters. The present chapter provides an insight into the method of radical ring-
opening polymerization (RROP) for the formation of biodegradable polyesters.
This is an unconventional route to the formation of polyesters which is still at the
research stage. The chemistry and utility of RROP in making functional polyesters
intended for use in various applications are discussed in this chapter.

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