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1.
Elastomers typically require the incorporation of reinforcing fillers in order to improve their mechanical properties. For commercial silicone systems silica and titania are typically used as fillers. Fumed and precipitated silica are made on an industrial scale for many applications; however, we have shown recently that biological and synthetic macromolecules can generate new silica structures using a bioinspired route. Herein we have incorporated bioinspired silica fillers into poly(dimethylsiloxane) (PDMS) elastomers and investigated their mechanical, morphological and thermal properties as a function of filler loading. The equilibrium stress-strain characteristics of the PDMS-bioinspired silica hybrids were determined as a function of bioinspired filler loading and the Mooney-Rivlin constants (2C1 and 2C2) were calculated. The thermal characteristics, in particular glass transition temperatures (Tg) and melting points (Tm), of the PDMS-bioinspired silica hybrids were characterized using differential scanning calorimetry (DSC). The thermal stability of these hybrid materials were investigated using thermogravimetric analysis (TGA). The morphology of the samples was characterized using scanning electron microscopy (SEM), and the filler dispersion was characterized using ultra small angle X-ray scattering (USAXS) and scanning electron microscopy (SEM). Although spherical silica particles were used here, we have demonstrated elsewhere that this bioinspired synthetic route also enables highly asymmetric silica structures to be prepared such as fibres and sheets. This methodology therefore offers the interesting possibility of preparing new hybrid systems where the properties are highly anisotropic.  相似文献   

2.
In this paper, a new type of soluble polyester/silica (PE/SiO2) hybrid was prepared by the ultrasonic irradiation process. The coupling agent γ-glycidyloxypropyltrimethoxysilane (GOTMS) was chosen to enhance the compatibility between the polyester (PE) and silica (SiO2). Furthermore, the effects of the coupling agent on the morphologies and properties of the PE/SiO2 hybrids were investigated using UV-vis and FT-IR spectroscopies and FE-SEM. The densities and solubilities of the PE/SiO2 hybrids were also measured. The results show that the size of the silica particle was markedly reduced by the introduction of the coupling agent, which made the PE/SiO2 hybrid films become transparent. Furthermore, thermal stability, residual solvent in the membrane film and structural ruination of membranes were analyzed by thermal gravimetric analysis (TGA). The effects of SiO2 nanoparticles on the glass transition temperature (Tg) of the prepared nanocomposites were studied by differential scanning calorimetry (DSC). Moreover, their mechanical properties were also characterized. It can be observed that the Young's moduli (E) of the hybrid films increase linearly with the silica content. The results obtained from gas permeation experiments with a constant pressure setup showed that adding SiO2 nanoparticles to the polymeric membrane structure increased the permeability of the membranes.  相似文献   

3.
Considering the importance of the nanocomposites, the present work focuses on some new hybrid materials prepared by introducing reactive organoclay (OC) into the chiral poly(amide-imide) (PAI) matrix. At first, Cloisite Na+ was modified with protonated l-isoleucine amino acid. Then, PAI containing phenylalanine was synthesized via solution polycondensation of chiral diacid chloride with 4,4′-diaminodiphenylsulfone and was characterized with Fourier transform infrared (FTIR) and 1H NMR techniques. At last, PAI/OC nanocomposite films containing 2, 5, 10, and 15 % of OC were prepared via solution intercalation method. The effect of OC dispersion and the interaction between OC and polymer chains on the properties of nanocomposites were investigated using FTIR, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, tensile testing of thin films, and thermogravimetry analysis techniques. The thermal stability of hybrids such as the decomposition temperature and mass residue at 800 °C was improved. Mechanical data indicated improvement in the tensile strength of the nanocomposites with OC loading up to 10 wt%. The transparency of the hybrid films was investigated by means of UV–Vis spectra.  相似文献   

4.
This research is aimed at characterizing the thermal, mechanical, and morphological properties of carbon nanotubes (CNTs) reinforced poly(amide-imide) (PAI) composites having thiazol and amino acid groups which were prepared by sonication-assisted solution compounding. To increase the compatibility between the PAI matrix and CNTs, carboxyl-functionalized multiwall CNTs (MWCNTs-COOH) were used in this study. The MWCNTs were dispersed homogeneously in the PAI matrix while the structure of the polymer and the MWCNTs structure are stable in the preparation process as revealed by transmission electron microscopy. MWCNT/PAI composite films have been prepared by casting a solution of precursor polymer containing MWCNTs into a thin film, and its tensile properties were examined. The thermal stability, Young’s modulus, and tensile strength of PAI were greatly improved by the incorporation of MWCNTs and their good dispersion. Composites were also characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and thermal gravimetric analysis.  相似文献   

5.
Epoxy–silica hybrids with interfacial bonding using aminophenyl-trimethoxysilane (APTMOS) have been prepared by the sol–gel process. In a sequential polymerization procedure the amine groups present on the APTMOS were used to partially cure diglycidyl ether of bisphenol-A (DGEBA) whereas the methoxy groups created silica-network simultaneously, through the sol–gel process. Complete curing and cross-linking were carried out later using curing agent jeffamine D-400 at higher temperature. The nature of silica network structure chemically bonded with the epoxy chains was studied by Fourier transformed infrared spectroscopy and the morphology of the hybrid through scattering electron and atomic force microscopies. The visco-elastic properties of the resulting hybrids were measured through dynamical thermal mechanical analysis. The effect of inter-phase bonding of the resulting hybrids and their thermal mechanical properties are compared with the similar DGEBA epoxy matrix where un-bonded silica network was produced from tetraethoxysilane. The properties of the hybrids using APTMOS show considerable improvement in thermal mechanical properties and the coefficient of thermal expansion is reduced in contrast to the un-compatiblized system.  相似文献   

6.
In the present investigation, novel poly(amid-imide)/zinc oxide nanocomposites (PAI/ZnO NCs) containing benzoxazole and benzimidazole pendent groups with different amounts of modified zinc oxide nanoparticles (ZnO NPs) were successfully prepared via the ex situ method. Poly(amid-imide) (PAI) was prepared by direct polycondensation of 2-[3,5- bis(N-trimellitimidoyl)phenyl]benzoxazole (DCA) with 5-(2-benzimidazole)-1,3-phenylenediamine (DAMI) and provided the polymeric matrix with well-designed groups. The surface of ZnO NPs was functionalized with 3-aminopropyltriethoxysilane (APS) coupling agent to have a better dispersion and enhancing possible interactions of NPs with functional groups of polymer matrix. The amount of APS bonded to the ZnO surface was determined by thermogravimetric analysis. PAI/ZnO nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). SEM analysis showed that the modified ZnO nanoparticles were homogeneously dispersed in polymer matrix. In addition, TGA data indicated an enhancement of thermal stability of the nanocomposite compared with the neat polymer.  相似文献   

7.
In this work, the synthesis strategy of a multifunctional system of [SBA-16/P(N-iPAAm)/Fe3O4] hybrids of interest for magneto-hyperthermia was explored. Magnetite nanoparticles coated by mesoporous silica were prepared by an alternative chemical route using neutral surfactant and without the application of any functionalization method. Monomer adsorption followed by in situ polymerization initiated by a radical was used to incorporate the hydrogel into the pore channels of the silica nanocomposite. Structural and magnetic characterization of the obtained materials was carried out by using thermal analysis, X-ray diffraction, N2 adsorption desorption isotherms, 57Fe Mössbauer spectroscopy, vibrating sample magnetometry and transmission electron microscopy. Measurements of alternating current magnetic-field-induced heating behaviour under different applied magnetic fields showed that the [SBA-16/P(N-iPAAm)/Fe3O4] hybrid here synthesized is suitable as a hyperthermia agent for biological applications.  相似文献   

8.
陈枫  傅强 《高分子科学》2013,31(11):1546-1553
Two kinds of poly(vinyl alcohol)(PVA)-silica composites were prepared with different methods. One composite was prepared by directly mixing PVA with 80 nm silica nano-particles which were made from tetraethoxysilane(TEOS). The another was obtained by the mixing PVA and hydrolyzed TEOS in the presence of acid-catalyst. The properties of the two PVA/silica hybrids were characterized by means of scanning electron microscopy(SEM), UV-Visible spectroscopy,solubility tests, limiting oxygen index(LOI) test, tensile test and dynamical mechanical analysis(DMA), respectively. The results indicate that PVA-TEOS composites(PT for short) display more transparency than PVA-silica nano-particles hybrids(PS for short). At the same time, The PT composites presented more excellent performance than PS in water resistance, fire resistance and mechanical properties. Moreover, the Tg of PT increased with increasing TEOS content, while that of PS decreased.  相似文献   

9.
Green polymer nanocomposites (NCs) show unique properties of combining the advantages of nanofillers and organic polymers. In this study, in order to control the dispersion of nanoparticles (NPs) in a polymer matrix, first, poly(vinyl alcohol) (PVA) as a green modifier was grafted on the surface of the CuO NPs to obtain CuO-PVA nanohybrid. Then poly(amide-imide) (PAI) was synthesized by the direct step growth polymerization of N-trimellitylimido-L-valine and 4,4′-methylenebis(3-chloro-2,6-diethylaniline) in ionic liquid medium. Finally, CuO-PVA hybrids were incorporated into the PAI matrix using ultrasonic technique for the preparation of PAI/CuO-PVA NCs. The obtained PAI/CuO-PVA NCs were characterized by different methods. The results of thermogravimetric analysis showed that thermal stability of the NCs was enhanced by incorporation of CuO-PVA nanohybrid compared to the pure PAI.  相似文献   

10.
In this work, multi-wall carbon nanotubes coated with polypyrrole (PPy/MWCNT) have been used as counter electrode (CE) materials for dye-sensitized solar cells (DSSCs). PPy was deposited onto fluorine-doped tin-oxide-coated glass by electrochemical polymerization of pyrrole. Three surfactants were used in the preparation of the hybrids: cationic cetyltrimethylammonium bromide, anionic sodium dodecylbenzenesulfonate (DBSNa), and non-ionic polyoxyethylene sorbitan monolaurate (Tween20). The morphologies of the PPy and PPy/MWCNT hybrids were investigated using scanning electron spectroscopy. Chemical composition of the prepared CEs was determined by X-ray photoelectron spectroscopy and Fourier-transformed infrared spectroscopy. The catalytic activity of the PPy and PPy/MWCNT layers was evaluated using cyclic voltammetry, and the photovoltaic properties of DSSCs with PPy and PPy/MWCNT CEs were characterized using IV measurements. PPy/MWCNT samples that were prepared by electrochemical polymerization showed the best results when the anionic surfactant DBSNa was used during polymerization. The photoelectric conversion efficiency of PPy/MWCNT prepared by electrochemical polymerization was 2.9%, which was 59% of that of Pt CE (4.9%).  相似文献   

11.
Imide-siloxane block copolymer/silica hybrid membranes with covalent bonds were prepared via sol–gel reaction. The structural informations of these hybrid membranes were obtained by using Fourier transform-infrared spectrometry (FT-IR), 29Si nuclear magnetic resonance (29Si NMR), XPS and thermogravimetric analysis (TGA). The gas separation properties of the hybrid membranes were also investigated in terms of organosiloxane (PDMS) or silica content at various temperatures. In the hybrids, the addition of PDMS phase increased the permeabilities of gases such as He, CO2, O2, and N2, indicating that the gas transport occurred mainly through rubbery organic matrix. Meanwhile, the PDMS phase contributed the decreased gas selectivities to nitrogen but the reduction in selectivities was very small in comparison with other siloxane containing polymeric membranes. This might be due to the restriction of chain mobility by the existence of inorganic component such as silica network in the hybrids. Additionally, the increase of silica content in these hybrid membranes considerably retarded the falling-off of gas selectivity at elevated temperature. The increase of silica content in hybrid membranes resulted in well-formed silica networks and hence these inorganic components restricted the plasticization of organic matrix by the thermal segmental motion of organic components, leading to preventing the large decrease of the gas selectivity.  相似文献   

12.
Recently, mesoporous silica was blended with polyimide to develop low dielectric constant (k) materials with improving mechanical and thermal properties of polyimide by utilizing both the nanoporous structure and silica framework. However, even the use of mesoporous silica did not show a significant decrease of k due to the phase segregation in between polyimide and the mesoporous silica materials. In this work, we attempted to prepare polyimide/mesoporous silica hybrid nanocomposites having relatively good phase mixing behavior by utilizing polyimide synthesized from a water soluble poly(amic acid) ammonium salt, which lead to low k up to 2.45. The thermal properties of polyimide were improved by adding mesoporous silicas. For this work, we have fabricated mesoporous silicas through surfactant-templated condensation of tetraethyl orthosilicate (TEOS). Pyromellitic dianhydride (PMDA)-4,4′-oxydianiline (ODA) polyimide was prepared from poly(amic acid) ammonium salt, which had been obtained by incorporating triethylamine (TEA) into PMDA-ODA poly(amic acid) in dimethylacetamide (DMAc), followed by thermal imidization.  相似文献   

13.
Nylon 6 (PA6)/clay hybrids have been prepared using a direct melt intercalation technique by two processes. One is PA6 melt-mixing with modified clay, the other is PA6 melt-mixing with natural (Na+ base) clay using an ammonium salt bearing long alkyl chains as a polymer/clay reactive compatibilizer. Their structure and flammability properties are characterized by X-ray diffraction, transmission electron microscopy and cone calorimeter experiments. The results of the cone calorimeter experiments show that hybrids made by these two processes have a lower heat release rate peak and higher thermal stability than that of original PA6. Meanwhile, X-ray diffraction was used to investigate PA6/clay hybrids with various cooling histories from the melt, including medium-rate cooling (air cooling) and rapid cooling (water-quenched). In contrast to pure PA6 dominated by the α phase, the addition of clay silicate layers by these two methods favors the formation of the γ crystalline phase in PA6/clay hybrids. Flammability and phase-transition studies confirm that silicate layers added by these two methods have a similar nanoeffect and nanodispersion in the PA6 matrix.  相似文献   

14.
In this study, a series of polymer–clay nanocomposite materials, consisting of organosoluble poly(amide-imide) (PAI) matrix and dispersed nanolayers of inorganic montmorillonite clay, were successfully prepared by solution dispersion technique. At first, the reactive organoclay was prepared by using protonated l-isoleucine amino acid as a swelling agent for silicate layers of Cloisite Na+. Then, organosoluble PAI containing isoleucine amino acid was synthesized through step-growth polymerization reaction of N,N′-(pyromellitoyl)-bis-isoleucine diacid and 2-(3,5-diaminophenyl)-benzimidazole under green condition using molten tetrabutylammonium bromide. This polymer was end-capped with amine end groups near the completion of the reaction to interact chemically with acidic group of organoclay. Finally, PAI/organoclay nanocomposite films containing 2%, 5%, 10%, and 15% of organoclay were prepared via solution intercalation method through blending of organoclay with the PAI solution. Dispersion of the modified clay in the PAI matrix resulted in a nanostructured material containing intercalated polymer between the silicate layers. Structures of exfoliation were confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy. Thermogravimetric analysis data indicated that the addition of organoclay into the PAI matrix increased the thermal decomposition temperatures of the obtained nanocomposites compared to the pure PAI.  相似文献   

15.
A novel flame-retardant silane containing phosphorus and nitrogen, tetramethyl(3-(triethoxysilyl)propylazanediyl) bis(methylene) diphosphonate (TMSAP), is firstly synthesized and then incorporated into poly(methyl methacrylate) (PMMA) matrix through sol–gel method to produce organic–inorganic hybrids. The chemical structure of TMSAP was confirmed by Fourier transform infrared spectra, 1H nuclear magnetic resonance (NMR) and 31P NMR spectra. The hybrids obtained maintain relatively high transparency, and exhibit a significant improvement in thermal properties, mechanical performance and flame retardancy when compared to pure PMMA, including increased glass transition temperature (T g ) by 11.4 °C, increased onset thermal degradation temperature (T0.1) by 82.6 °C, increased half thermal degradation temperature (T0.5) by 42.0 °C, increased hardness, increased limited oxygen index and decreased heat release rate. Morphological studies of hybrids by scanning electron microscopy (SEM) and 29Si MAS NMR suggest that cross-linked silica network is formed in the hybrids and the inorganic silica particles are distributed well in the polymer matrix. Thermal degradation behaviors investigated by thermogravimetric analysis and char structure analysis studied by SEM and X-ray photoelectron spectroscopy demonstrate the catalytic charring function of TMSAP, and synergistic effect between phosphorus, nitrogen and silicon element. The formation of network structure, homogeneous distribution of silica and the char formation during degradation play key roles in these property enhancements. Detailed mechanisms for these enhancements are proposed.  相似文献   

16.
Nanostructured amino acid containing poly(amide-imide) (PAI) was synthesized from the direct polycondensation reaction of 2–(3,5–diaminophenyl)–benzimidazole and N,N′–(pyromellitoyl)–bis–phenylalanine diacid under green condition by using tetrabutylammonium bromide as molten ionic liquid. Field emission scanning electron microscopy images show that the average diameter of polymeric nanoparticles with spherical shape was around 20–35 nm. In the next step, these polymeric nanoparticles were used as nano-fillers for reinforcement of poly(vinyl alcohol) (PVA) for the first time. Bionanocomposite of PVA and various compositions of PAI nanoparticles were produced through ultrasound-assisted technique. Fourier transform infrared spectroscopy, x-ray diffraction, field emission scanning electron microscopy, and thermogravimetric analysis were utilized to characterize the obtained hybrid materials, morphology, and properties. Results of thermal properties indicated that the thermal stability is enhanced. The improvement of thermal properties was attributed to the homogeneous and good dispersion of PAI nanoparticles in the PVA matrix and the strong hydrogen bonding between O–H groups of PVA and the carbonyl of amide and imide groups of the used PAI nanoparticles.  相似文献   

17.
A series of polyurethane/polyaniline/silica organic/inorganic hybrids were synthesized via the conventional polyurethane (PU) prepolymer technique. Amine-endcapped polyaniline (PANI) with low molecular weight and higher solubility was firstly synthesized. This PANI oligomer was then used together with nano-silica bearing silanol groups as chain extenders to prepare the conducting polyurethane hybrids. The polyurethane hybrids were designated as PU-xPANI-ySiO2 (x + y = 1). For comparison, the urethane-aniline block copolymer and the PU/silica hybrid were designated as PU-PANI and PU-SiO2, respectively.The structures of PU-PANI, PU-SiO2 and conducting polyurethane hybrids were confirmed by FT-IR, solid-state 13C, and 29Si NMR spectra. In nano-silica containing organic/inorganic conducting polyurethane hybrids, UV-vis spectra revealed the maximum absorption bands similar to that of PU-PANI. X-ray diffraction patterns indicated that these samples are typical of semicrystalline/amorphous materials. SEM image of PU-0.5PANI-0.5SiO2 showed that PANI was dispersed homogeneously and interconnected continuously in the insulating PU-silica matrix. TGA results of the polymer hybrids exhibited higher thermal stabilities and lower decomposition rates than that of PU-PANI both in nitrogen and air. Differential scanning calorimetry (DSC) studies indicated that the polyurethane hybrids had higher glass-transition temperatures (Tg) with the increase of PANI, but lower than that of PU-PANI. Stress-strain curves for all of the polyurethane hybrids showed the elastomeric behavior of typical polyurethanes. The surface resistivity values of all hybrids were about 108 ∼ 1010 Ω/sq. and might meet the requirement of the anti-electrostatic materials.  相似文献   

18.
Physical and gas transport properties of novel hyperbranched polyimide–silica hybrid membranes were investigated and compared with those of linear‐type polyimide–silica hybrid membranes with similar chemical structures. Hyperbranched polyamic acid, as a precursor, was prepared by polycondensation of a triamine, 1,3,5‐tris(4‐aminophenoxy)benzene (TAPOB), and a dianhydride, 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA). 6FDA‐TAPOB hyperbranched polyimide–silica hybrids were prepared using the polyamic acid, water, and tetramethoxysilane (TMOS) by sol–gel reaction. 5% weight‐loss temperature of the 6FDA‐TAPOB hyperbranched polyimide–silica hybrids determined by TG‐DTA measurement considerably increased with increasing silica content, indicating effective crosslinking at polymer–silica interface. CO2, O2, N2, and CH4 permeability coefficients of the 6FDA‐based polyimide–silica hybrids increased with increasing silica content. In addition, CO2/CH4 selectivity of the 6FDA‐TAPOB–silica hybrids remarkably increased with increasing silica content. From 129Xe NMR analysis, characteristic distribution and interconnectivity of cavities created around polymer–silica interface were suggested in the 6FDA‐TAPOB–silica hybrids. It was indicated that size‐selective separation ability is effectively brought by the incorporation of silica for the 6FDA‐TAPOB hyperbranched polyimide–silica hybrid membranes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 291–298, 2006  相似文献   

19.
Combining multiple inorganic components is an effective approach to improve the mechanical properties of inorganic–organic hybrid materials. The inorganic components can form interactions with the organic polymer matrix, and there is thus a need to understand the reinforcement mechanism under the optimal combination of organic polymer and inorganic particles. In this work, we prepared a series of dual inorganic particle–based titania/silica–poly(tetrahydrofuran)–poly(ε-caprolactone) (TiO2/SiO2–PTHF–PCL) hybrids by means of simultaneous cationic ring-opening polymerization and sol–gel reaction. In addition to constructing hybrid networks, the SiO2 and TiO2 components play important roles in multiple toughening mechanisms. The prepared dual inorganic hybrids feature enhanced thermal stability and mechanical properties when compared with the ones with a single inorganic component. The optimized mixing of such two inorganic components is identified through mechanical tests, revealing that the hybrid polymer70/(Si0.6Ti0.4)30 (70/18/12 mass ratio) has the highest compressive failure strain (80%) and compressive ultimate strength (1.3 MPa) as well as storage modulus (120 kPa), enabling elongation of up to 37% when compared with its original length. We thus find that the dual inorganic component approach is an effective strategy to enhance the mechanical properties of hybrid materials, suggesting potential applications as scaffolds for tissue engineering and soft robotics.  相似文献   

20.
To improve the ultraviolet resistance and thermal stability of waterborne polyurethane, stable waterborne polyurethane/nano-cerium oxide hybrid dispersions were obtained by adding nano-cerium colloids to previously synthesized waterborne polyurethane dispersions. The dried ceria colloid was characterized by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The XRD results indicated the prepared CeO2 was a face-centered cubic structure. The prepared polyurethane/CeO2 dispersions were studied by dynamic light scattering (DLS), transmission electron microscopy (TEM), UV–Vis spectroscopy and accelerated weathering test. The dried polyurethane/CeO2 films were characterized using thermogravimetric analysis (TGA). The DLS analysis indicated the particles average diameter of hybrids emulsion was bigger than that of the pure waterborne polyurethane dispersion. TG analysis and accelerated weathering test suggested the hybrid latex films had better thermal stability and mechanical properties than those of the pure waterborne polyurethane. The UV–Vis absorption capacity of the dispersions prepared was increasing with the amount of CeO2 colloid increased.  相似文献   

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