Differently from bulk, solution, suspension, emulsion, and miniemulsion polymerizations, the controlled radical dispersion polymerization (CRDP) demonstrates self-assembly of the block copolymers formed in the homogeneous system, forming various kinds of micelles or vesicles. Thus, this technology can prepare both the block copolymers and the polymeric aggregates directly. Among CRDP, the reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization has been studied in relative detail and has been successfully developed to prepare a diverse range of assemblies. Several typical systems for RAFT dispersion polymerization are presented in detail and the factors influencing the polymerization and the in situ self-assembly are also highlighted in this minireview.
The self-assembly of block copolymers attracts wide interest due to many potential applications of the polymeric aggregates. Great effort has been made to realize the convenient fabrication of abundant polymeric materials with well-defined nanostructures. This review introduces the development of the in situ preparation of block copolymer aggregates by heterogeneous polymerization. Great emphasis is put on discussing the formation mechanism of aggregates with different morphologies. Some important factors that influence the morphologies are illustrated when different polymerization methods are employed. By demonstrating some recent advances and existing problems in this area, more attention and effort should be paid to this field to facilitate its further progress.
5 April 2012 in Macromolecular Rapid Communications
Poly(vinylidene fluoride) (PVDF) homopolymer and its copolymers in their β phases are the most promising polymeric materials for electroactive devices. In this work, a simple and effective strategy is developed to fabricate β-poly(vinylidene fluoride-co-hexafluoropropylene) (β-PVDF-hfp) with characteristic piezo-/ferro-electric properties using mesoporous SiO2 nanorods. The nanorods offer 2-fold arrangement for the –OH groups, namely, anisotropic rod shape and ordered mesopores. We report, for the first time in the PVDF system, the direct evidence of hydrogen bond interaction during β phase formation through XPS analysis. Our study further reveals that besides well-known facilitation by intermolecular interaction, the arrangement of surface functional groups is essential for the formation of β-PVDF-hfp. This proposed mechanism manages to explain the current controversy in the formation mechanism. We further demonstrate that our approach can be extended to a wider intermolecular interaction regime than hydrogen bonding, thus benefitting current development in PVDF homo/copolymer-based electroactive devices.