An Amphiphilic Corona-Forming Block Promotes Formation of a Variety of 2D Platelets via Crystallization-Driven Block Copolymer Self-Assembly

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We describe the crystallization-driven self-assembly of a poly(ferrocenyldimethylsilane) (PFS) block copolymer [PFS 50 - b -P(EG-E)MA 48 ] 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.