Supramolecular self-assembly of architecturally variant α-cyclodextrin inclusion complexes as building blocks of hexagonally aligned microfibrils

Inclusion complexes (ICs) were prepared by the host-guest reaction between (x-cyclodextrin (aCD) and four poly(epsilon-caprolactone)s (PCLs) with different molecular architectures: star-shaped PCL (SPCL) with a radial architecture, random branched PCL (RPCL) with a conical architecture, poly(propylene glycol)-PCL block copolymer (PPG-PCL) with a diblock architecture, and PCL-diol (LPCL) with a linear architecture. Then, the ICs were self-assembled by treatment with suitable polar solvent such as THE From WAXD, it was found that both the ICs and the self-assembled ICs (SA-ICs) obtained from THF treatment of ICs had hexagonally organized channel-type crystalline structure, resulting from inclusion complexation between (x-CD and PCL chain. Combined results of WAXD, FE-SEM, and SAXS further revealed that ICs had the microfibril structure in which single IC strands were hexagonally aligned in the horizontal direction. The microfibrils in ICs were then reorganized by THF treatment, thereby developing well-defined supramolecular structure for ICs with RPCL (R-1C), PPG-PCL (P-IC), and LPCL (L-IC), except IC with SPCL (S-IC). From SAXS experiments, it was verified that the self-assembled supramolecular structures were attributed to continuous alignment of the microfibril by THE Furthermore, SA-ICs with RPCL, PPG-PCL, and LPCL (R-SA-IC, P-SA-IC, and L-SA-IC, respectively) exhibited the different supramolecular structure, depending on the architecture of the respective polymeric guests. In particular, both R-SA-IC and P-SA-IC showed the microphase separated supramolecular structure because of block-selected inclusion complexation of alpha-CD as confirmed by H-1 NMR. However, the radial architecture of SPCL was considered to hinder the continuous packing of microfibril, thereby supramolecular structure being not accomplished in S-SA-IC. Interestingly, the development of the supramolecular structures was found to be obtained only by treatment with the THF among the various polar solvents.