ABSTRACT:The fluorosilicone block copolymers of poly(perfluoroalkylethyl acrylate)-bpoly(3-[tris(trimethylsilyloxy)silyl] propyl methacrylates) (PFA-b-PSiMAs) having perfluoroalkyl and silicone-containing side chains were obtained by three-step synthetic approaches. In the first step, hydroxyl-terminated poly(perfluoroalkylethyl acrylate) macromonomer (PFAM) was prepared by the free-radical polymerization of perfluoroalkylethyl acrylate and 2-mercaptoethanol. In the second step, PFAM initiator (PFAMI) was prepared from the condensation reaction of the hydroxyl-terminated PFAM and 4,4Ј-azobis-4-cyanopentanoic acid chloride (ACPC). ACPC was obtained from the reaction of 4,4Ј-azobis-4-cyanopentanoic acid and phosphorus pentachloride. In the third step, PFA-b-PSiMAs (BPFSs) were synthesized from the reaction of PFAMI macroinimer and SiMA. Fourier transform infrared spectroscopy and 1 H-NMR analyses verified that the syntheses of ACPC, hydroxyl-terminated PFAM, PFAMI, and BPFS were completed successfully. The intrinsic surface energies of BPFSs and their surface modification effects on poly(vinyl chloride) film were investigated by analyzing the surface free energies and atomic compositions of the outermost layer of the surfaces. BPFSs exhibit extremely low surface free energies of about 9.7-13.0 dynes/cm. It was confirmed that BPFS, having extremely low surface free energy, is preferentially enriched at the outermost layer of the surface of BPFS/poly(vinyl chloride) blend.

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Dihydroxyl-terminated macromonomers with two groups, a perfluoroalkyl group and a silicone-containing group, were synthesized by free-radical polymerization with perfluoroalkylethyl acrylate (FA), 3-[tris(trimethylsilyloxy)silyl] propyl methacrylate (SiMA), and 1-thioglycerol (TG). Using these macromonomers and toluene-2,4diisocyanate (TDI), various urethane graft-co-(septadecafluorodecylacrylate)-(tris(trimetylsiloxy silylpropyl acrylate) copolymers (PUFSGs) with differing FA and SiMA contents were synthesized. The macromonomers and PUFSGs synthesized were characterized and identified by GPC, DSC, (X-ray photoelectron spectroscopy (XPS), FTIR, and 1 H-NMR analysis. The surface free energies of PUFSGs, 9 -12 dynes/cm, depend strongly on FA content but not on SiMA content. The glass transition temperature of PUFSG is strongly dependent on SiMA content. The perfluoroalkyl group originating from FA is preferentially arranged to the outermost layer at the air-polymer interface to the silicone-containing group originating from SiMA. The surface free energies of PUFSG/polyvinyl chloride (PVC) blends exhibit extremely low values, 10 -14 dynes/cm, indicating that extreme segregation of PUFSG occurs at the air-polymer interface. Most PUFSGs added to PVC are located at the air-polymer interface, and PUFSGs are very effective in lowering the surface free energy.

Dihydroxyl-terminated macromonomers with two groups, a perfluoroalkyl group and a silicone-containing group, were synthesized by free-radical polymerization with perfluoroalkylethyl acrylate (FA), 3-[tris(trimethylsilyloxy)silyl] propyl methacrylate (SiMA), and 1-thioglycerol (TG). Using these macromonomers and toluene-2,4-diisocyanate (TDI), various urethane graft-co-(septadecafluorodecylacrylate)-(tris(trimetylsiloxy silylpropyl acrylate) copolymers (PUFSGs) with differing FA and SiMA contents were synthesized. The macromonomers and PUFSGs synthesized were characterized and identified by GPC, DSC, (X-ray photoelectron spectroscopy (XPS), FTIR, and 1 H-NMR analysis. The surface free energies of PUFSGs, 9 -12 dynes/cm, depend strongly on FA content but not on SiMA content. The glass transition temperature of PUFSG is strongly dependent on SiMA content. The perfluoroalkyl group originating from FA is preferentially arranged to the outermost layer at the air-polymer interface to the silicone-containing group originating from SiMA. The surface free energies of PUFSG/polyvinyl chloride (PVC) blends exhibit extremely low values, 10 -14 dynes/cm, indicating that extreme segregation of PUFSG occurs at the air-polymer interface. Most PUFSGs added to PVC are located at the air-polymer interface, and PUFSGs are very effective in lowering the surface free energy.

The surface conditions of LiFePO4 powder were modified by adding AlF3 and Al2O3 by using the sol-gel process to improve its electrochemical properties. The surface of LiFePO4 powders was partially covered with nano-sized AlF3 and Al2O3, which is confirmed by using a transmission electron microscope image. The states of coated Al materials were examined by using X-ray photoelectron spectrometer results. The nano-sized AlF3- and Al2O3-coated LiFePO4 powders showed no difference in the bulk structure compared with the pristine one. However, the AlF3- and Al2O3-coating on LiFePO4 powders improved the overall electrochemical properties such as the discharge capacity, the cyclability, and the rate capability compared with those of a pure LiFePO4. Such enhancements were attributed to the presence of a stable AlF3 and Al2O3 layer which acts as an interfacial stabilizer on the surface of LiFePO4 powders.