ABSTRACT
CONTENTS 8.1 Introduction ................................................................................................103 8.2 One-Step Synthesis of Caprolactone-Glycolide Segmented
Copolymers and Monofilament Sutures Thereof .................................104 8.2.1 Design of the Polymerization Scheme and Rationale.............104 8.2.2 Properties of Typical Polymers ...................................................105 8.2.3 Physicochemical and Biological Properties of Typical
Monofilament Sutures ..................................................................105 8.3 Copolyesters Made by End-Grafting Cyclic Monomers onto
Polyalkylene Succinate and Monofilament Sutures Thereof..............108 8.3.1 Design of Polymerization Scheme and Rationale....................108 8.3.2 Properties of Typical Polymers ...................................................109 8.3.3 Physical and In Vivo Properties of Typical Monofilament
Sutures.............................................................................................109 8.4 Conclusion and Perspective on the Future ........................................... 110 References ............................................................................................. 110
Segmented copolymers geared for the production of compliant monofilament sutures described in Chapter 3 dealt with the use of end-grafting of an amorphous, or low melting, polyaxial polymeric initiator with cyclic monomers to form crystalline end-grafts. In this particular chain design, the
amorphous core, due to the polyaxial initiator, is responsible for the imparted high compliance. In a search for other approaches to the production of absorbable, segmented copolyesters for conversion to compliant monofilament sutures, two new experimental strategies were recently explored.1-3 The first strategy was to:
• Use two monomers with vastly different rates of polymerization to yield segmented chains by direct copolymerization
• Use the two monomers in certain relative amounts to allow the formation of soft, noncrystalline segments that resist ester-ester interchange under prevailing polymerization and extrusion conditions
• Rely on a fast polymerizing comonomer as the source of the crystalline fraction, which retains its crystalline morphology through most of the polymerization and subsequent processes
• Conduct the copolymerization well below the Tm of the crystalline component of the segmented polymer
Accordingly, the first part of this chapter deals with the copolymerization of an I-caprolactone/glycolide mixture that is rich in glycolide wherein the critical stage of the copolymerization is conducted in the solid state below 200rC, which is well below the 225rC of the Tm of polyglycolide.1
