Grafting and Patterned Grafting of Block Copolymer Nanotubes onto Inorganic Substrates

Self-assembly and chemical processing of block copolymers: a roadmap towards a diverse array of block copolymer nanostructures

Block copolymers can yield a diverse array of nanostructures. Their assembly structures are influenced by their inherent structures, and the wide variety of structures that can be prepared especially becomes apparent when one considers the number of routes available to prepare block copolymer assemblies. Some examples include self-assembly, directed assembly, coupling, as well as hierarchical assembly, which can yield assemblies having even higher structural order. These assembly routes can also be complemented by processing techniques such as selective crosslinking and etching, the former technique leading to permanent structures, the latter towards sculpted and the combination of the two towards permanent sculpted structures. The combination of these pathways provides extremely versatile routes towards an exciting variety of architectures. This review will attempt to highlight destinations reached by LIU Guojun and coworkers following these pathways.

Simultaneous coating of silica particles by two diblock copolymers

Silica particles have been coated by two diblock copolymers, P1 and P2, through a one-pot reaction, and the resultant particles were characterized. The P1 and P2 used were synthesized by anionic polymerization and denote PIPSMA-b-PFOEMA and PIPSMA-b-PtBA, respectively. Here PIPSMA, PFOEMA, and PtBA correspond individually to poly[3-(triisopropyloxysilyl)propyl methacrylate], poly(perfluorooctylethyl methacrylate), and poly(tert-butyl acrylate). Catalyzed by HCl, the PIPSMA blocks of P1 and P2 co-condensed onto the surface of the same silica particles, exposing the PtBA and PFOEMA blocks. The relative amounts of grafted P1 and P2 could be tuned by changing the P1 to P2 weight ratio and were quantified by thermogravimetric analysis. The vertical segregation of the PFOEMA and PtBA chains could also be adjusted. Casting a dispersion of the coated particles in a solvent selective for either PFOEMA or PtBA onto glass plates or silicon wafers yielded films consisting of bumpy silica particles whose surfaces were enriched by the polymer that was soluble in the casting solvent. Particulate coatings with tunable surface wetting properties were obtained by changing either the proportion of grafted P1 and P2 or the casting solvent for coated silica. When a silica dispersion in perfluoromethylcychohexane (C(7)F(14)) was cast, films of coated silica that had P1 weight fractions of 25, 50, and 75% were all superhydrophobic because the particle surfaces were enriched by PFOEMA, which was selectively soluble in C(7)F(14).

Layer-by-layer deposition of block copolymer nanofibers and porous nanofiber multilayer films

We report in this paper the preparation of multilayer films from the layer-by-layer deposition of block copolymer nanofibers bearing carboxyl and amine groups in their coronas. The film formation process was followed by atomic force microscopy and UV absorbance measurements. For the large size of the nanofibers and probably also for the difficulty associated with reshuffling the positions of nanofibers once they were adsorbed by an underlying layer, nanofibers could not be packed densely. We took advantage of this "defective" feature and showed that these porous nanofiber multilayer films could be used to separate nanospheres of different sizes and probably also of different surface functionalities.