Department of Chemistry, University of Chiang Mai^* Biomedical Polymers Technology Unit, Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand^** Polymer Science Centre, University of Reading, Reading RG6 6AF, UK^***
○Jintana Siripitayananon^* Robert Molloy^** Yodthong Baimark^** Geoffrey R. Mitchell^***

Co/terpolymers of L-lactide, ε-caprolactone and glycolide are biodegradable and have potential for use as absorbable monofilament surgical sutures. Both random and segmented triblock co/terpolymers of various compositions were melt spun at slow speeds into cooled water to obtain almost completely “quenched amorphous” monofilament as-spun fibres. Combinations of hot-drawing and annealing steps under different conditions of rate, temperature and time were employed to increase crystallinity and molecular orientation. The processed fibres were then characterized using DSC and XRD. A novel approach using a series of spherical harmonic functions to represent XRD patterns enabled the molecular orientation to be evaluated. Mechanical (tensile) properties of the fibres were determined and related as far as possible to their physical morphologies. The results showed that the block copolymers had more potential to be developed as absorbable monofilament sutures than the random copolymers. As an example, the tensile strength of an L-lactide : ε-caprolactone (79:21 mol %) block copolymer fibre tested at 25^oC, as obtained from its stress-strain curve, was found to be about 94% of that of a commercial 'PDS II' monofilament surgical suture of similar size (size 2-0) tested under identical conditions.