Synthesis and fabrication of nanostructional functional polymeric materials via plasma processes and polymer modification

Abstract

Plasma processes and polymer modification are two versatile tools for the fabrication of polymer nanostructures and nanopatterns. Nanostructures of functional polymers, such as fluoropolymers, electroactive polypyrrole (PPY), and others, can be prepared potentially via plasma processes or polymer modification. The aim of this work was to develop simple and novel methods for the fabrication of fine polymer nanostructures and nanopatterns from fluoromonomers and pyrrole via plasma polymerization, plasma etching, or polymer modification. It was also the objective of this work to explore useful functionalities and potential applications for these nanostrutured polymers after characterization. Initially, via plasma polymerization and deposition at room temperature, highly hydrophobic fluoropolymers were synthesized by exploring various polymerization parameters, such as the wide range of system pressures (13 ¿ 107 Pa) and glow discharge powers (100 ¿ 400 W), and the natures of fluoromonomers of different boiling points (b. p.), molecule weight (MW), and degree of saturation. Mesoporous fluoropolymer nanospheres were prepared via the agglomeration of fine poly(heptadecafluorodecyl acrylate) (pp-HDFA) nanoparticles from plasma polymerization and deposition. Relationships between particle size and glow discharge duration during the high energy plasma polymerization of the HDFA monomer were elucidated. With these mesoporous nanospheres, a series of ultra-thin (< 100 nm) and low dielectric constant nanoporous films were obtained by means of one-round or multiple pulse plasma polymerizations. In addition, by carefully controlling the monomer concentrations and polymerization parameters, two-dimensionally and three-dimensionally self-assembled pp-HDFA nanospheres on hydrogen-terminated Si(100) (H-Si) wafers were fabricated in dry ambience. The morphology of horizontally aligned particles could be changed from particle `chains¿ to particle `bars¿ by reducing the particle distribution density on the wafer surface. The vertically assembled nanoparticles in the form of pyramids were obtained under a very low initial monomer concentration and the effect of the electric field in the reaction chamber. Furthermore, by carefully controlling the input plasma power, system pressure, and glow discharge duration, mesoporous polypentafluorostyrene (pp-PTFS) nanospheres and films were synthesized from the PTFS monomer. The porous nanospheres can be used to fabricate magnetic porous nanospheres upon thermal-decomposition of the adsorbed pentacarbonyl iron. By using the two different plasma functions (viz. plasma polymerization and plasma etching) in a plasma system, mesoporous fluoropolymer nanospheres of 200 - 300 nm in size were prepared directly via one-pot plasma polymerization and deposition, followed by controlled argon plasma dry etching. The porous fluoropolymer nanospheres can be used as substrate to adsorb PtFe nanoparticles, and thus imparting magnetic functionality on the mesoporous nanospheres. Finally, via polymer modification in wet process, functional micro- and nano-structures from conductive aqueous PPY colloidal dispersions were created. The stable PPY colloidal dispersions were prepared via oxidative polymerization of pyrrole by FeCl3 in the presence of surfactants in an aqueous medium. Zero to three dimensional (0 - 3D) PPY nanostructures, such as 0D nanoparticles, 1D nanofibres, 2D nanofilms, and 3D nanoflowers were fabricated by casting, coating, or spraying. When using these PPY nanospheres as substrates, magnetic CoFe shell/conductive PPY core nanospheres, hollow magnetic CoFe nanospheres, and conductive microspheres with magnetic handles were also prepared.