Fabrication Of Fluorinated Polymer Porous Materials By Self-Assembly

Fluorinated polymer porous films and porous polymeric films doped with nano-SiO₂ were prepared by self-assembly. The resulting polymeric porous films and doped films were characterized by means of transmission electron microscopy (TEM) and atomic force microscopy (ATM). The chemical states of some typical elements in the films before and after annealing were analyzed by means of X-ray photoelectron spectroscopy (XPS). At the same time, the tribological properties of the two types of polymeric films were investigated. The main contents and results are as follows:(1) Preparation and characterization of fluorinated porous polymeric film Hexafluorobutyl acrylate (HFBA), methyl methacrylate (MMA), 2-hydroxyethyl methacrylate (HEMA), and acrylic acid (AA) were used as monomers to prepare poly(2-hydroxyethyl methacrylate-methyl methacrylate-hexafluorobutyl acrylate-acrylic acid) latex particles [coded as poly(MMA-HFBA-AA-HEMA)] by surfactant-free emulsion polymerization in the presence of (NH₄)₂S₂O₈ as the initiator. The obtained polymeric emulsion was blended with a proper amount of hexa-methoxyrnethyl-melamine (HMMM), followed by film-formation at room temperature. The as-formed film was then annealed at a certain temperature to generate fluorinated porous polymer films. The morphology, microstructure, and grit size of the spherical polymeric emulsion particles were analyzed using a transmission electron microscope. The morphology of the fluorinated porous polymeric film was observed using an atomic force microscope, and the effects of annealing temperature, content of coupling agent, content of hydroxyl group, and content of HFBA on the morphology and microstructure of the films were investigated. Moreover, the chemical states of some typical elements in the films before and after annealing were analyzed by means of X-ray photoelectron spectroscopy (XPS). The wetting behavior of the porous polymeric films was evaluated using a contact angle meter. And the tribological behavior of the films was evaluated using a UTM-2 multi-specimen test rig. It was found that the spherical polymeric emulsion particles had regular core-shell structure and uniform grit size. Porous array structures were obtained after annealing of the polymeric film, and the size of the pores increased gradually with increasing annealing temperature until it turned to decrease after reaching a maximum. At the same time, the size of the pores increased with increasing content of coupling agent, decreasing content of hydroxyl group, and increasing content of HFBA, but its ordered structure was damaged to some extent at a too high content of HFBA. Besides, the content of F decreased, while that of N increased after annealing of the polymeric porous films. And the hydrophicility of the films increased with increasing content of coupling agent, indicating that it could be feasible to manipulate the wetting behavior of the films by properly adjusting the content of coupling agent. Moreover, the introduction of HFBA at various contents led to decreased friction coefficient and increased wear resistance of the porous polymeric films.(2) Preparation and characterization of in-situ SiO₂ doped polymeric porous filmsOrganic compounds such as C₆H₅CH=CH₂, CH₂=C(CH₃)COOCH₃, H₂C=CHCOO(CH₂)₃CH₃, CH₂=C(CH₃)COOCH₂CH₂OH and H₂O=CHCOOH were used as monomers to prepare doped emulsion spheres with core-shell structure via surfactant-free emulsion polymerization in the presence of [(NH₄)₂S₂O₈] as the initiator, where dopant SiO₂ [including superhydrophobic silica soluble in the monomers (coded as DNS-3) and superhydrophilic silica soluble in solvents (coded as RNS-A)] was in-situ introduced into the emulsion sphere. The obtained emulsion was blended with a proper amount of hexa(methoxyme-thyl)-melamine (HMMM), followed by film-formation at room temperature. The as-formed films were then annealed at 180℃ for 30 min. generating porous polymer films doped with SiO₂. The morphology, microstructure. and grit size of the doped polymeric emulsion spheres were analyzed using a transmission electron microscope. The morphology of the doped porous polymeric film was observed using an atomic force microscope. It was found that the two types of doped SiO₂ appeared as agglomerated clusters in the emulsions, and RNS-A was less severely agglomerated and able to adhere onto the surface of the emulsion spheres. Porous array structures were obtained after annealing of the doped polymeric films, and the two types of doped SiO₂ appeared as agglomerated clusters in the doped porous polymeric films. Moreover, although dopant SiO₂ did not affect the formation of the porous structure, it led to damage to the smoothness of the doped porous films.