Thermal, mechanical, and topographical evaluation of nonstoichiometric α‐cyclodextrin/poly(ε‐caprolactone) pseudorotaxane nucleated poly(ε‐caprolactone) composite films. Issue 22 (4th October 2018) - Narayanan, Ganesh
ABSTRACT: Three pseudorotaxanes (PpR) comprised of poly (ε‐caprolactone) (PCL) and α‐cyclodextrin (α‐CD) with varying stoichiometric ratios were synthesized and characterized. Wide‐angle X‐ray diffraction (WAXD) and thermogravimetric (TGA) analyses provided conclusive evidence for complexation between the guest PCL and host α‐CD. The as‐synthesized and characterized PpRs were used at 10 and 20% concentrations as nucleants to promote the bulk PCL crystallization in composite films. Both WAXD and TGA provided evidence for intact PpR structures in the composite films. Isothermal differential scanning calorimetric (I‐DSC) analyses, performed at various crystallization temperatures demonstrated significant differences in the crystallization patterns among the composite films. In addition, I‐DSC analyses showed higher Avrami constant values (n) in the PpR‐nucleated composite PCL films (n ~ 3), indicating 3‐dimensional crystal growth. In the case of neat PCL films, however, lower n values indicated crystal growth in 1‐dimensions or 2‐dimensions. Moreover, atomic force microscopic analyses showed large crests and pits in PpR‐nucleated PCL composites, with irregular morphologies leading to higher surface roughness. To the contrary, the crests and pits were much smaller in the neat PCL films, resulting in lower surface roughness values. Finally, mechanical testing revealed higher tensile strength for PpR‐nucleated PCL composites films, demonstrating larger load bearing capabilities. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys.2018, 56, 1529–1537 Abstract : Improving the mechanical and topographical properties of biomedical polymers such as poly(ε‐caprolactone) (PCL) is a paramount factor in improving its interaction with biological systems. A major aspect of this work is to demonstrate the mechanical and topographical properties of PCL containing pseudorotaxanes (PpRs), which are comprised of PCL and nontoxic α‐cyclodextrin as nucleants. By varying stoichiometric ratios and loading of PpRs, composite films were prepared that showed modulated and improved mechanical and topographical properties.