Synthesis of polymer nanograss and nanotubes by surface-initiated photopolymerization in cylindrical alumina nanopores

Abstract

Functional polymer nanograss and nanotubes with active epoxy groups were synthesized by a surface-initiated photopolymerization pattern transfer method in cylindrical alumina nanopores. The nanograss structures were obtained when the neat glycidyl methacrylate (GMA) monomer or the mixture of GMA monomer and ethylene glycol dimethacrylate (EGDMA) crosslinker solution was injected into the photoinitiator-immobilized template. In contrast, uniform polymer nanotubes that completely follow the contour of the template were generated with the mixture of GMA monomer, EGDMA crosslinker and pre-synthesized poly(glycidyl methacrylate) (PGMA) polymer as the precursor material. The mechanism of the formation of polymer nanograss and nanotubes was discussed in terms of mechanical strength of polymer and polymerization shrinkage. The incorporation of the pre-synthesized polymer into the monomer solution as the precursor material allows for precompensation of the structure shrinkage induced by photopolymerization reactions. Effects of the pre-synthesized PGMA polymer percentage and the amount of the EGDMA crosslinker on the morphology of the formed polymer nanostructures were investigated respectively. FT-IR spectra confirmed the chemically immobilized photoinitiators, and chemical component, poly(GMA-co-EGDMA), of the polymer nanotubes inside the cylindrical alumina nanopores respectively. Finally, an intriguing dendritic-shaped fractal pattern was formed from concentrated crosslinked polymer nanoneedles by self-assembly and droplet evaporation.