Synthesis of copolymers of ε-caprolactone and L-lactide and a preliminary study on their electrospinning process

A kind of ε-caprolactone/L-lactide copolymers with varying compositions and molecular weights has been synthesized by using Sn(II)octoate as catalyst and 1, 4-butanediol as initiator. The copolymerization was carried out under vacuum at 130°C for 24 h.The copolymer structure was characterized in detail by using GPC, FTIR, ¹H-NMR, DSC and XRD analyses. It was shown that the chemical compositions and molecular weights of the copolymers were adjustable by changing the monomer molar ratios in feed, and their appearances and physical characteristics were closely related with the variation of composition and molecular weight. The number average molecular weight is changed from 1 × 10 to 1 × 10. The melting temperature is in a range from 15°C to 55°C. A preliminary study was also conducted on the electrospinning process of the resulting copolymers. The copolymer was first dissolved in CH₂ Cl₂ at a concentration of 6 wt%. The solution was then delivered at a constant flow rate (5 mL/h) with an air gap of 20 cm between the metal collector and the needle tip at a driving voltage of 20 kV. Finally ultrafine fibers were obtained, and melting binding between different fibers was evidenced by SEM observation. The solvent cast membrane of LC-96-6k was found to be stronger than that of LC-50-6k. However, their electrospinning nonwoven fabrics showed lower but comparable mechanical properties.