Inclusion complex formation between α,γ-cyclodextrins and a triblock copolymer and the cyclodextrin-type-dependent microphase structures of their coalesced samples

A triblock copolymer (PCL-PPG-PCL, M-n = 1.38 x 10(4)) of poly(epsilon-caprolactone) (PCL) and poly(propylene glycol) (PPG) was synthesized by ring-opening polymerization of epsilon-caprolactone. Cyclodextrin (CD)-type-dependent formation of inclusion complexes (ICs) between cyclodextrins and this triblock copolymer was studied. Only PCL blocks were included as guests in the IC formed with alpha-cyclodextrin (alpha-CD), while both PCL and PPG blocks were included in the IC formed with gamma-cyclodextrin (gamma-CD). As a result, the copolymer coalesced from its IC crystals with alpha-CD showed an increased crystallinity, while to the contrary, the copolymer coalesced from its IC crystals with gamma-CD exhibited a decreased crystallinity, when both were compared to the as-synthesized triblock copolymer. Fourier transform infrared (FTIR) spectra, C-13 CP/MAS solid-state NMR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and wide-angle X-ray diffraction (WAXD) measurements were employed to study the formation of ICs as well as to gauge the microphase separation in the coalesced samples.