POSS end-linked peptide-functionalized poly(ɛ-caprolactone)s and their inclusion complexes with α-cyclodextrin

Abstract

In this report, we have synthesized organic/inorganic hybrid peptide–poly(ɛ-caprolactone) (PCL) conjugates via ring opening polymerization (ROP) of ɛ-caprolactone (CL) in the presence of two sequence defined peptide initiators, namely POSS-Leu-Aib-Leu-NH2 (POSS: polyhedral oligomeric silsesquioxane; Leu: Leucine; Aib: α-aminoisobutyric acid) and OMe-Leu-Aib-Leu-NH2. Covalent attachment of peptide segments with the PCLs were examined by 1H and 29Si NMR spectroscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and FTIR spectroscopy. Supramolecular inclusion complexations of synthesized peptide-PCL conjugates with α-cyclodextrin (α-CyD) were studied to understand the effect of POSS/OMe-peptide moieties at the PCL chain ends. Inclusion complexation of peptide-PCL conjugates with α-CyD produced linear polypseudorotaxane, confirmed by 1H NMR, FTIR, powder X-ray diffraction (PXRD), polarized optical microscopy (POM) and differential scanning calorimetry (DSC). Extent of α-CyD threading onto the hybrid peptide-PCL conjugated polymers is less than that of α-CyD threaded onto the linear PCL. Thus, PCL chains were not fully covered by the host α-CyD molecules due to the bulky POSS/OMe-peptide moieties connected with the one edge of the PCL chains. PXRD experiment reveals channel like structures by the synthesized inclusion complexes (ICs). Spherulitic morphologies of POSS/OMe-peptide-PCL conjugates were fully destroyed after inclusion complexation with α-CyD and tiny nanoobjects were produced. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3643–3651.