Polystyrene- and Poly(3-vinylpyridine)-Grafted Magnetite Nanoparticles Prepared through Surface-Initiated Nitroxide-Mediated Radical Polymerization

et al. 2008

Polym J

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Surface-initiated atom transfer radical polymerization of 2-(perfluorooctyl)ethyl acrylate on a flat silicon wafer was carried out to give poly{2-(perfluorooctyl)ethyl acrylate} (PFA-C 8 ) brush thin film with three different thicknesses of 4, 11, and 43 nm, respectively. The water contact angle of the PFA-C 8 brush surface was 120. The molecular aggregation state of the perfluoroalkyl (R f ) group of PFA-C 8 brush was analyzed by X-ray reflectivity (XR), wide-angle X-ray diffraction, and grazing incidence X-ray diffraction (GIXD) measurements. XR analysis revealed that R f groups at the air/brush interface formed a densely packed structure, while a relatively low-density region was generated at the brush/substrate interface. The peaks of in-plane GIXD for brush films with thicknesses of 11 and 43 nm were observed at q xy ¼ 12:5 nm À1 , which indicated that R f groups at the outermost surface oriented perpendicular to the surface of silicon substrate. In an out-of-plane diffraction profile of the 43 nm-thick PFA-C 8 brush film, peaks corresponding to a periodic length of the bilayer lamellae were observed. Therefore, R f groups of the thicker brush film were crystallized and formed ordered bilayer lamellar structure at the outermost surface. In contrast, no diffraction pattern was observed from the PFA-C 8 at a thickness of 4 nm by WAXD and GIXD. These results indicate that an amorphous layer was formed at the interface of the brush/substrate. The R f groups at the anchoring region of the brush could not form a sufficiently ordered structure due to immobilization of brush chain ends on the substrate. It was suggested that the R f groups in a PFA-C 8 brush thin film at the outermost surface aggregated in a different manner from those in the anchoring region.KEY WORDS: Perfluoroalkyl Acrylate / Polymer Brush / Water-Repellant Surface / X-Ray Reflectivity / Grazing Incidence X-ray Diffraction / Surface-initiated Polymerization / It has been well-known that polymers with perfluoroalkyl (R f ) groups show excellent chemical and thermal stability, nonadhesive properties, low friction coefficients, low surface free energy, and antifouling behavior. These properties of fluorinated polymers are primarily caused by unique C-F bonds which have a large binding energy and quite a low dielectric constant due to short bonding distance between carbon and fluorine atom with high electro negativity. However, the surface component, orientation packing, and end groups also affect the surface behavior of the polymer films.1-3 When the surface is uniformly covered with trifluoromethyl (CF 3 ) groups, 4 excellent water repellency and a very low energy surface can be achieved. 5 In the case of poly(fluoroalkyl acrylate)s with long R f groups, the molecular aggregation state of the R f groups at the side chains affects the surface wettablity. 6,7 We have recently reported the relationship between the molecular aggregation states and the water repellency of poly(perfluoroalkyl acrylate) (PFA-C y , where y is the number of fluoromethylene...

Section: Results and Disscusionmentioning

confidence: 99%

Molecular Aggregation State of Surface-grafted Poly{2-(perfluorooctyl)ethyl acrylate} Thin Film Analyzed by Grazing Incidence X-ray Diffraction

Yamaguchi

Honda

et al. 2008

Polym J

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“…Table 1 lists the M n s and MWDs of free polymers determined by SEC. The authors have previously found that the grafted polymer chains possess almost the same M n and MWD as those of the free polymers based on SEC measurement of the grafted polymers cleaved from the Fe 3 O 4 surface by acidic hydrolysis [32]. Accordingly, the M n and MWD of polymer brushes on TiO 2 nanoparticle were evaluated by SEC measurements of the corresponding free polymers, suggesting that controlled NMRP successfully proceeds from surface-immobilized TP and the free initiator at the same rate of propagation.…”

Section: Preparation and Physicochemical Properties Of Highdensity Pomentioning

confidence: 98%

“…1 The formation of P-O-M bonds was detected by IR and XPS spectra, indicating the anchoring of TP on the surfaces of the metal oxide nanoparticles. Surface-initiated NMRP of styrene and 3VP from nanoparticles was carried out as shown in our previous report [32] (Scheme 2). Table 1 lists the M n s and MWDs of free polymers determined by SEC.…”

Section: Preparation and Physicochemical Properties Of Highdensity Pomentioning

confidence: 99%

Precise surface structure control of inorganic solid and metal oxide nanoparticles through surface-initiated radical polymerization

Science and Technology of Advanced Materials

Matsuno

Otsuka

et al. 2006

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Surface-initiated radical polymerization was carried out in order to modify the surface of inorganic solid and metal oxide nanoparticles. Novel (inorganic nanoparticles/polymer) nanocomposites were prepared through a direct polymer grafting reaction from the surfaces of magnetite (Fe 3 O 4 ) (d ¼ 10 and 25 nm) and titanium oxide (TiO 2 ) (d ¼ 15 nm) nanoparticles. The initiator for nitroxidemediated radical polymerization with a phosphoric acid group was chemisorbed onto the nanoparticles and gave controlled polystyrene (PS) and poly(3-vinylpyridine) (P3VP) graft layers on their surfaces. The PS-and P3VP-modified nanoparticles were finely dispersed in organic solvents, whereas protonated P3VP-modified magnetite nanoparticles were dispersed in aqueous phase. The fine dispersion of nanoparticles in the polymer matrix was confirmed by microscopic observation. In order to realize tribological control, atom transfer radical polymerization of (2,2-dimethyl-1,3-dioxolan-4-yl)methyl methacrylate was also carried out from an immobilized initiator on a flat silicon wafer, resulting in a high-density polymer brush that was subsequently converted to a hydrophilic polymer brush consisting of 2,3-dihyroxypropyl methacrylate units. The poly(2,3-dihydroxypropyl methacrylate) brush-immobilized surface showed a low dynamic friction coefficient in water due to the highly stable hydrophilicity. r

“…TEMPO-based alkoxyamine with a hydroxy group 15,16 was prepared as previously reported. 1-[Isocyanatopropyldimethylsilyl]-3,5,7,9,11,13,15-heptacyclopentylpentacyclo[9.5.1.1 3;9 .1 5;15 .1 7;13 ]octasiloxane (POSS-NCO) was purchased from Aldrich Chemical Co. Styrene and deuterated styrene were purchased from commercial sources and purified by distillation under reduced pressure over calcium hydride.…”

Section: Methodsmentioning

confidence: 99%

Dewetting Inhibition and Interfacial Structures of Silsesquioxane-terminated Polystyrene Thin Films

Miyamoto

Hosaka

et al. 2007

Polym J

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ABSTRACT:Polyhedral oligomeric silsesquioxane (POSS)-terminated polystyrene (PS-POSS) was prepared by nitroxide-mediated radical polymerization of styrene with POSS-containing initiator, and the thermal stability of PS-POSS thin films was investigated. Rheological measurement of PS-POSS revealed that the rheological properties were profoundly affected by the presence of POSS end groups in low molecular weight region (M n % 2000), while those were nearly unaffected in high molecular weight region (M n %