Synthesis, Structure, and Crystallization Behavior of Amphiphilic Heteroarm Molecular Brushes with Crystallizable Poly(ethylene oxide) and n-Alkyl Side Chains

A series of heteroarm amphiphilic molecular brushes (AMBs) with poly(ethylene glycol) (PEG) and long chain n-alkyl side chains were synthesized via conventional free radical polymerization (FRP) of mainly 4-vinylbenzyl-PEG methyl ether and N-alkylmaleimide macromonomers. By varying PEG side chain degree of polymerization (DP = 12, 16, and 20) and n-alkyl chain lengths (C16 and C20), we produced AMBs with varying combinations of side chain lengths. This enabled the elucidation of the effect of side chain length on AMB phase behavior, semicrystalline morphologies, and crystallization kinetics via differential scanning calorimetry, polarized light optical microscopy, and X-ray diffraction experiments. Calculations of segregation strength together with SAXS measurements indicate that all materials have probably phase-segregated structure in the melt. Most of the AMB materials prepared were double crystalline, i.e., contained crystals from alkyl and PEG chains. AMB crystallization was constrained by AMB archit...