An Amphiphilic Corona-Forming Block Promotes Formation of a Variety of 2D Platelets via Crystallization-Driven Block Copolymer Self-Assembly
Shaofei Song, Hang Zhou, Garion E. J. Hicks, Jingjie Jiang, Yefeng Zhang, Ian Manners, Mitchell A. Winnik
Abstract
We describe the crystallization-driven self-assembly of a poly(ferrocenyldimethylsilane) (PFS) block copolymer [PFS50-b-P(EG-E)MA48] with amphiphilic pendant groups in the corona-forming block P(EG-E)MA (poly(tetraethylene glycol monododecyl ether methacrylate)). The block ratio in terms of the degree of polymerization (the subscripts) was designed to be close to 1 in order to promote formation of two-dimensional micelles by self-assembly in poor solvents for the PFS block. The amphiphilic corona-forming block is soluble in a wide variety of solvents of distinct hydrophilicities and polarities (e.g., 2-propanol, 1-pentanol, 1-octanol, and decane). This property enabled us to examine self-assembly of the block copolymer by the seeded growth protocol in this wide range of different solvents. In 2-propanol, self-assembly was difficult to study except at very low seed micelle concentrations and led to the formation of rounded rectangular platelets. Nearly circular but uniform disks formed in 1-pentanol, and leaf-shaped structures with irregular edges formed in 1-octanol. In 1-pentanol, 3D circular spirals were formed at elevated levels of unimer addition, presumably due to screw dislocations. These structures are all very different from the spherulite objects that we reported previously (Angew. Chem. Int. Ed, 2021, 60, 10,950–10,956) for similar self-assembly experiments with this polymer in decane. We also examine the transition in morphology in mixtures of decane and 1-octanol.