文摘
Synthesis and living cationic ring-opening polymerization of a 2-oxazoline containing self-assembling minidendrons with hexadecyl groups are reported. Structural analysis using X-ray diffraction, molecular modeling, and reconstructed electron density maps revealed multiple self-organized periodic arrays, including columnar hexagonal P6mm, cubic Pm3̅n, and tetragonal P42/mnm phases, which have not been observed before in a single homopolymer. The degree of polymerization (DP) of the poly(2-oxazoline) programs the sequence of these periodic arrays. The cubic Pm3̅n phase was observed for DP = 5 whereas the tetragonal P42/mnm for 10 ≤ DP ≤ 50. For DP ≥ 75, only a columnar hexagonal P6mm phase was accessible because the polymer chains are too long to form a single supramolecular sphere. This sequence was rationalized by the columnar character of supramolecular spheres to provide the richest diversity of structures assembled from a single polymer and an unprecedented example of a tetragonal phase organized from macromolecular spheres comprising a single polymer chain.