Tailor-made ultra-crystalline, high molecular weight poly(ε-caprolactone) films with improved oxygen gas barrier and optical properties: a facile and scalable approach.
The work presents a facile and scalable approach for fabricating tailor-made ultra-crystalline, high molecular weight biodegradable polymer poly(ε-caprolactone) [PCL] through ring-opening polymerization. Linear homopolymer of PCL were fabricated by tuning the molar ratio of monomer: initiator: catalyst in associated with organometallic catalyst (tin octoate) and a non-toxic and structurally symmetric initiator ethylene glycol (EG). High molecular weight PCL homopolymer formation with molecular weight higher than 90,000 Da was examined by FTIR, NMR and GPC. The ultra-crystalline characteristics (percent crystallinity, %Xc >70%) and unique crystal morphology of PCL were thoroughly scrutinized using DSC, XRD, HRTEM, SAED patterns and POM analysis. The developed protocol for the solvent-free technology allows high conversion ~99% at lowest possible reaction time of 1 h suggesting it a cost effective process, which is scalable to larger volume (5000 mL) without compromising the final product properties. The fabricated ultra-crystalline, high molecular weight PCL films showed good oxygen barrier property (~197 cm3 mm-1 day-1), surface free energy (133.7 mN/m) and optical transparency, recommending its niche in envisioned applications like low temperature flexible packaging and biomedical field.