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[摘要]：Diblock copolymers with a crystalline poly(ferrocenyldimethylsilane) (PFDMS) core-forming block have been previously shown to self-assemble in selective solvents for a coblock such as polyisoprene (PI) to form cylindrical micelles (where the material is asymmetric, with a PI:PFDMS block ratio of ca. >5:1) or platelets (where the block ratio is ca. 1:1). Moreover, upon addition of further cylinder-forming block copolymer to the ends of the crystalline cores of the cylinders, the faces of the platelets and also the surfaces of thin films of PFDMS homopolymer has been shown to initiate the further growth of cylinders by a living self-assembly process. This is believed to involve an epitaxial growth mechanism. To obtain more detailed insight and to examine the generality of this behavior, we report here detailed comparative studies of the analogous poly(ferrocenyldiethylsilane) (PFDES) homopolymer and the corresponding PI-PFDES diblock copolymers. Significantly, although PI-b-PFDES diblock copolymers with a semicrystalline PFDES core-forming block show similarities to their known PFDMS counterparts in terms of their self-assembly behavior in selective solvents for PI, important differences were also observed. For example, a pronounced tendency of PFDES diblock copolymers to form tape-like structures in solution was noted for PI:PFDES block ratios of ca. 6:1. Uniform cylindrical structures were obtained as the exclusive morphology by increasing the length of the PI block to block ratios of 19:1. Nevertheless, the successful crystallization-driven living self-assembly of PFDES block copolymers involving homoepitaxial growth was demonstrated by the addition of block copolymer unimers to preformed stub-like crystallites formed by sonication. This allowed controlled growth of monodisperse cylinders with the length controlled by the unimer to seed ratio. However, heteroepitaxial growth of PFDES block copolymer from seed micelles of the PFDMS analogue (and vice versa) could not be accomplished. This may be a consequence of the lattice mismatch between the materials and/or kinetic effects. The results demonstrate that crystallization-driven living self-assembly is not limited to PFDMS diblock copolymers and suggest that, although significant differences in self-assembly behavior are likely, this process may be expected to be applicable to other diblock copolymers with a semicrystalline core-forming block. |
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