A spramolecular star-like polymer

This study reports the creation of star-like chain architecture through complexation of a mono-amino terminated poly(ethylene oxide) (PEO-NH2) with a macrocyclic compound, 4-sulfonic calix[n]arene (n = 4 and 8) (SCA-n). The complexes were prepared in aqueous solution to render proton transfer from the sulfonic acid groups in SCA-n to the amino groups in PEO-NH2, and thereby generated 4- and 8-arm star-like complexes with the PEO arms attached to the SCA-n cores via ionic bonding. Formation of the complexes was verified by titration, solubility test, and dilute solution viscometry. The intrinsic viscosities ([eta]) of the complexes in toluene were 60% higher than that of neat PEO-NH2, showing that the star-like structure retained in nonpolar solvents. On the other hand, PEO arms dissociated from the cores in water, so that the complexes and neat PEO-NH2 displayed similar [eta]. The star-like supramolecules showed a SAXS peak associated with the core-core correlation in the melt with the inter-core distance of 7.3 nm. The concentration fluctuation in the melt was completely destroyed upon the crystallization of PEO arms. In the semicrystalline state, the SCA-n cores were excluded from the crystal lattice and resided in the interlamellar amorphous regions. Measurements of the crystal thickness by SAXS indicated that the PEO chains in the crystals were once- and twice-folded in neat PEO-NH2 and the complexes crystallized at 40 degreesC, respectively.