Papers by Keyword: Organic-Inorganic Hybrid

Abstract: Natural bone has excellent mechanical properties such as high fracture toughness and high flexibility. These properties are achieved by specific microstructure of natural bone that is composed of the organic collagen and inorganic apatite. On the basis of these findings, apatite-polymer hybrids are expected as novel bone substitutes having excellent mehcanical performances and high bone-bonding ability, i.e. bioactivity. In this study, we attempted preparation of apatite-polyglutamic acid hybrids through biomimetic process that mimics the principle of biomineralization. Simple chemical modification of the polyglutamic acid gel with 1 M (= mol/L) calcium chloride solution provided the gel with apatite-forming ability in simulated body fluid (SBF, Kokubo solution). This type of hybrid is also useful for designing bioactive bone substitutes with injectability, since viscosity of the polyglutamic acid gel can be easily controlled according to degree of cross-linking.

Abstract: Organic polymers with ability of apatite formation in body environment are expected as novel bone substitutes having not only bone-bonding ability, i.e. bioactivity, but also mechanical performance analogous to natural bone. Several metal oxides have been found to be effective for the apatite deposition in body environment. In addition, release of calcium ions from the materials significantly enhances it. In this study, we attempted to synthesize bioactive organic-inorganic hybrids from poly(vinyl alcohol) (PVA) by incorporation of titanium oxide or zirconium oxide as well as calcium salt. Ability of apatite formation on the hybrids was examined in vitro using simulated body fluid (SBF, Kokubo solution). Apatite deposition was observed to occur on the surfaces of PVA/titanium oxide hybrids in SBF, when their compositions were appropriately controlled.

Abstract: A new porous benzene-silica hybrid clay heterostructure has been prepared by a template-assisted method. The synthesis of Hybrid Porous Clay Heterostructures (HPCH) has been performed via the intercalation of a quaternary ammonium cation surfactant (cetyltrimethylammonium bromide) and a neutral amine (octylamine) as cosurfactant, in a Portuguese clay, to direct the interlamellar hydrolysis and condensation polymerisation of neutral inorganic etraethylorthosilicate (TEOS) together with an organic precursor, the 1,4- bis(triethoxysilyl)benzene (BTEB). The material has been characterised by elemental analysis, powder X-ray diffraction, nitrogen adsorption, 13C CP MAS, 29Si MAS and CP MAS NMR spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and thermal analyses. The hydrophobicity of the material was tested by water adsorption. Its potential application as adsorbent of volatile organic compounds was studied by the adsorption of methanol, methyl ethyl ketone, toluene and trichloroethylene.

Abstract: Nanometric ferrihydrite, maghemite and magnetite particles formed within an organicinorganic hybrid matrix were obtained by the sol-gel process. In contrast to precipitation techniques, sol-gel process appears as suitable way to achieve size-controlled nanoscopic magnetic particles anchored in a hybrid structure. The hybrid matrix here reported, named di-ureasil, is composed of poly(oxyethylene) chains grafted to siloxane groups by means of urea cross-linkages. The formation of ferrihydrite particles was achieved incorporating iron nitrate during the sol-gel process, at low pH. The formation of maghemite takes place after the incorporation of a mixture of Fe3+ and Fe2+ ions and treatment with an ammonia solution, after the sol-gel process. Magnetite nanoparticles are formed after the incorporation of Fe2+ ions and treatment with ammonia at 80°C. The AC magnetic susceptibility shows thermal irreversibility with a blocking temperature TB≈13K and ≈25K depending on frequency for the ferrihydrite and maghemite particles, respectively. The magnetite nanoparticles are blocked at room temperature. Above the irreversibility the magnetization of ferrihydrite and maghemite follows a Langevin function modified with a linear term, as found in antiferromagnetic and ferrimagnetic particles.

Abstract: This paper focuses on the influence of interactions between different species in hybrids (CnH2n+1NH3)2MCl4 (M = Mn, Cu; n =2,4,6,8,10) on the structural stabilities. DSC-TG curves were used to find out the onset and the end decomposition temperatures. The results show that the hybrids of M =Cu start to decompose at about 210 centigrade degrees, average 25 centigrade degrees lower than that of M=Mn. The end temperatures of M=Cu are also lower. This suggests that in this case the thermal stabilities of the hybrids would be governed by the interactions between the organic and inorganic species and are little affected by weak Van de Waals interactions between the organic and organic species.

Abstract: This paper focuses on the structural change and the thermochromism of the phase transition of the hybrid (C12H25NH3)2FeCl4. The temperature and the structures of the phase transition is investigated by a thermal gravimetry (TG) and differential scanning calorimetry (DSC), an infrared spectra (IR) and X-ray diffraction (XRD) patterns. The UV adsorption spectra account for the thermochromism. The results suggest that the reversible phase transition arises from the structural changes of the organic chains. The thermochromism is presumably due to the electrons redistribution on the levels and to the energy transition to translational and rotational motions of the organic chains.

Abstract: Apatite formation in living body is essential condition for artificial materials to exhibit bone-bonding ability, i.e. bioactivity. It has been recently revealed that sulfonic group triggers apatite nucleation in body environment. Organic-inorganic hybrids consisting of organic polymer and the sulfonic group are therefore expected to be useful for novel bone-repairing materials exhibiting flexibility as well as bioactivity. In the present study, organic-inorganic hybrids were prepared from vinylsulfonic acid sodium salt and hydroxyethylmethacrylate (HEMA), a kind of acrylic polymer. Bioactivity of the hybrids was assessed in vitro by examining their acceptance of apatite formation in simulated body fluid (SBF, Kokubo solution). The obtained hybrids showed the apatite deposition after soaking in SBF within 7 d.

Abstract: Organic-inorganic hybrids involving Ti-O bonds were coated on stainless-steel (SUS316L)substrates. Tetraisopropoxide and titanium methacrylate triisopropoxide were employed as the major starting chemicals to provide TiO2-polydimethylsiloxane (PDMS) layers or organotitanium molecular thin layers, respectively. Fourier transform infrared spectra indicated that each layer contained Ti-O bonds in their structure. The obtained hybrid layers had little effects on the blood-clotting times such as active partial thromboplastin time and prothrombin time. In addition, the number of adhered platelet on the TiO2-PDMS layers depended on the composition, while the organotitanium molecular thin layers suppressed fibrinogen adsorption compared with coating-free SUS 316L substrate.

Abstract: Organic polymers with ability of apatite formation in body environment are expected as novel bone substitutes having not only bone-bonding ability, i.e. bioactivity, but also mechanical performance analogous to natural bone. Several metal oxides have been found to be effective for the apatite deposition in body environment. In addition, release of calcium ions from the materials significantly enhances it. In this study, we attempted to synthesize bioactive organic-inorganic hybrids from Poly(vinyl alcohol) (PVA) by incorporation of various metal oxides and calcium salt. Silica and molybdenum oxides were selected as metal oxides. Ability of apatite formation on the hybrids was examined in vitro using simulated body fluid (SBF, Kokubo solution). Apatite deposition were observed to occur on the surfaces of PVA/silica and PVA/molybdenum oxide hybrids in SBF, when their compositions were appropriately controlled.

Abstract: The photopolymerization of aromatic methacrylate in organic-inorganic nanocomposite films for holographic recording media was investigated. Thick photopolymer films (thickness>200 µm) were prepared using organic-inorganic hybrid solutions containing high refractive index monomers, through the sol-gel process. These photopolymer films were polymerized upon exposure to a visible light with high photo conversions. The photopolymerization was highly effective under visible light irradiation and could be applied to a holographic medium with high diffraction efficiency (>95 %) by using a 532nm laser. The diffraction efficiency of the film was much affected by morphology, which might affect monomer diffusion during the recording.