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1.
A series of functional polyhedral oligomeric silsesquioxane (POSS)/polyimide (PI) nanocomposites were prepared using a two‐step approach. First, octa(aminophenyl)silsesquioxane (OAPS) was mixed with poly(amic acid) (PAA) prepared by reacting bis(4‐amino‐3,5‐dimethylphenyl)‐3‐quinolylmethane and 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride. Second, the resulting solution was subjected to thermal imidization. The well‐defined ‘hard particles’ (POSS) and the strong covalent bonds in the amide linkage between the carbon atom of the carboxyl side group in PAA and the nitrogen atom of the amino group in POSS lead to a significant improvement in the thermal and mechanical properties. Homogeneous dispersion of POSS cages in the PI is evident from scanning electron microscopy, which further confirms that the POSS molecule becomes an integral part of the organic‐inorganic inter‐crosslinked network system. Differential scanning calorimetry and dynamic mechanical analysis show that the glass transition temperatures of the POSS‐containing nanocomposites are higher than that of the corresponding neat PI system, owing to the significant increase of the crosslinking density in the PI/POSS nanocomposites. Increasing the concentration of OAPS in the PI networks decreases the dielectric constant. Pure PI and PI/POSS systems have good antimicrobial activity. Copyright © 2011 Society of Chemical Industry  相似文献   

2.
Research into organic–inorganic nanocomposites has recently become popular, particularly the development of new polymer nanocomposites. Compared to pristine polymers or conventional composites, these nanocomposites exhibit improved properties. The storage modulus of a poly(vinyl chloride) (PVC)/polyhedral oligomeric silsesquioxane (POSS) nanocomposite slightly decreased with POSS content, but had a higher modulus from 50 to 100 °C. Some of the material appeared to be aggregated with 1 wt% POSS in the polymeric matrix. Conversely, with a POSS content of 5 wt%, a better dispersion of the nanoparticles was observed. The presence of POSS in the plasticised PVC compound had little influence on the final properties of the nanocomposites, showing weaker interactions between the POSS and the plasticised PVC compound. Copyright © 2010 Society of Chemical Industry  相似文献   

3.
Poly(ε‐caprolactone)/clay nanocomposites were synthesized by in situ ring‐opening polymerization of ε‐caprolactone in the presence of montmorillonite modified by hydroxyl functionalized, quaternized polyhedral oligomeric silsesquioxane (POSS) surfactants. The octa(3‐chloropropyl) polyhedral oligomeric silsesquioxane was prepared by hydrolytic condensation of 3‐chloropropyltrimethoxysilane, which was subsequently quaternized with 2‐dimethylaminoethanol. Montmorillonite was modified with the quaternized surfactants by cation exchange reaction. Bulk polymerization of ε‐caprolactone was conducted at 110°C using stannous octoate as an initiator/catalyst. Nanocomposites were analyzed by X‐ray diffraction, transmission electron microscopy, thermo gravimetric analysis, and differential scanning calorimetry. Hydroxyl functionalized POSS was employed as a surface modifier for clay which gives stable clay separation for its 3‐D structure and also facilitates the miscibility of polymer with clay in the nanocomposites due to the star architecture. An improvement in the thermal stability of PCL was observed even at 1 wt % of clay loading. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

4.
Jun Kai Herman Teo 《Polymer》2011,52(9):1975-5343
In this article, we report novel epoxy-based hybrids prepared via incorporating 1,2-dimethyl-3-(benzyl-heptaisobutyl-POSS) imidazolium chloride (POSS-IMC) and POSS-IMC-modified clay (POSS-MMT) into the resin based on 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate (ECHM) and hexahydrophthalic anhydride (HHPA). We demonstrate that both POSS-IMC and POSS-MMT can reduce the cure temperature of the epoxy/anhydride system, and the catalyzing effect involves chemical reactions between POSS-IMC and ECHM/HHPA, which may lead to the attachment of POSS cages at chain ends. The incorporation of the POSS-IMC, free and ionically bonded in clay, gives rise to dissimilar morphologies that affect the thermo-mechanical properties of the hybrids. The ECHM/HHPA/POSS-IMC resin exhibits a slight improvement in glassy modulus as compared with the neat ECHM/HHPA resin, which is attributed to the formation of sub-micron and nano-sized POSS domains that act as physical cross-link points hindering polymer chain motions. The much enhanced reinforcing effect of POSS-MMT is ascribed to the effective stress transfer between the matrix and clay layers that may originate from the strong interactions between the pendent POSS in the network and POSS attached to the clay surfaces. Reduction in coefficient of thermal expansion (CTE) was also found for the hybrids.  相似文献   

5.
廖明义  范诚 《弹性体》2011,21(1):75-81
多面体低聚倍半硅氧烷(POSS,Polyhedral Oligomeric Silsesquioxane)作为一种特殊的有机/无机杂化纳米粒子备受关注。本文综述了国内外通过离子型反应机理制备聚合物/POSS纳米杂化材料的一些进展,着重介绍反应机理、特点,并对这一领域的前景进行了展望。  相似文献   

6.
The synthesis and characterization of POSS containing ABA triblock copolymers is reported. The use of atom transfer radical polymerization (ATRP) enabled the preparation of well-defined model copolymers possessing a rubbery poly(n-butyl acrylate)(pBA) middle segment and glassy poly(3-(3,5,7,9,11,13,15-heptaisobutyl-pentacyclo[9.5.1.13,9.15,15.17,13]-octasiloxane-1-yl)propyl methacrylate(p(MA-POSS)) outer segments. By tuning the relative composition and degree of polymerization (DP) of the two segments, phase separated microstructures were formed in thin films of the copolymer. Specifically, dynamic mechanical analysis and transmission electron microscopy (TEM) observations reveal that for a small molar ratio of p(MA-POSS)/pBA (DP=6/481/6) no evidence of microphase separation is evident while a large ratio (10/201/10) reveals strong microphase separation. Surprisingly, the microphase-separated material exhibits a tensile modulus larger than expected (ca. 2×108 Pa) for a continuous rubber phase for temperatures between a pBA-related Tg and a softening point for the p(MA-POSS)-rich phase. Transmission electron microscopy (TEM) images with selective staining for POSS revealed the formation of a morphology consisting of pBA cylinders in a continuous p(MA-POSS) phase. Thermal studies have revealed the existence of two clear glass transitions in the microphase-separated system with strong physical aging evident for annealing temperatures near the Tg of the higher Tg phase (p(MA-POSS). The observed aging is reflected in wide-angle X-ray scattering as the strengthening of a low-angle POSS-dominated scattering peak, suggesting some level of ordering during physical aging. The Tg of the POSS-rich phase observed in the microphase separated triblock copolymer was nearly 25 °C higher than that of a POSS-homopolymer of the same molecular weight, suggesting a strong confinement-based enhancement of Tg in this system.  相似文献   

7.
A novel polyhedral oligomeric silsesquioxane (POSS) containing a mercaptopropyl group [mercaptopropyl polyhedral oligomeric silsesquioxane (MPOSS)] was synthesized via the hydrolytic condensation of γ-mercaptopropyl triethoxysilane in an ethanol solution catalyzed by concentrated hydrochloric acid and was used to modify epoxy–amine networks by a cocuring reaction with diglycidyl ether of bisphenol A (DGEBA). The structure, morphology, and thermal and mechanical properties of these MPOSS/DGEBA epoxy nanocomposites were studied and investigated with thermogravimetric analysis/differential thermal analysis (TGA–DTA), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). From SEM analysis, we observed that the miscibility between epoxy and POSS occurred at a relatively high POSS content, which characterized this mixture as a polymer nanocomposite system. The impact test showed that MPOSS reinforced the epoxy effectively, and the SEM study of the impact fracture surface showed that the fibrous yielding phenomenon observed was an indication of the transition of the brittle stage to a ductile stage and correlated well with the large increases in the impact strength; this was in agreement with the in situ reinforcing and toughening mechanism. The TGA–DTA analysis indicated that the MPOSS/DGEBA epoxy hybrids exhibited lower thermostability at a lower temperature but higher thermostability and higher efficiency in char formation at an elevated temperature. Differential scanning calorimetry showed that the glass transition temperature (Tg) of the MPOSS/epoxy hybrids were lower than that of the neat epoxy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

8.
The structure and properties of organic-inorganic hybrid nanocomposites prepared from a resole phenolic resin and a POSS mixture containing >95 wt% trisilanolphenyl POSS was investigated by POM (polarized optical microscopy), SEM, TEM, WAXD, FT-IR, DSC, and TGA techniques. Composites with 1.0-10.4 wt% of POSS were prepared by dissolving the POSS and the phenolic resin into THF, followed by solvent removal and curing. Both nano- and micro-sized POSS filler aggregates and particles were shown to be heterogeneously dispersed in the cured matrix by POM, TEM, SEM, and X-EDS. POSS was found everywhere, including in both dispersed phase domains and in the matrix. The nanocomposite morphology appears to form by a multi-step POSS aggregation during the process of phase separation. Both the matrix and dispersed ‘particulate’ phase domains are mixtures of phenolic resin and POSS. POSS micro-crystals act as the core of the dispersed phase. The bigger dispersed domains consist of smaller particles or aggregates of POSS molecules that exhibit some order but regions of matrix resin are interspersed. A WAXD peak at 2θ∼7.3° indicates crystalline order in the POSS aggregates. This characteristic peak's intensity increases with an increase in POSS loading, suggesting that more POSS molecules have aggregated or crystallized. FT-IR spectra confirm that hydrogen bonding exists between the phenolic resin and POSS Si-OH groups. This increases their mutual compatibility, but H-bonding does not prevent POSS aggregation and phase separation during curing. TGA measurements in air confirmed the temperature for 5% mass loss in increases with increase of POSS loading and at T>550° the thermal stability increases more sharply with POSS loading. The nanocomposite glass transition temperatures (Tg) are only slightly be affected by the POSS filler.  相似文献   

9.
Fc-CHCH-C6H6-(C5H9)7Si8O12 (POSS1, Fc: ferrocene) which contain both metal and CC double bond was firstly synthesized by Wittig reaction. The chemical structure of POSS1 was characterized by FTIR, 1H, 13C and 29Si NMR, mass spectrometry and elemental analysis, and the magnetic property of POSS1 have also been studied. Polystyrene composites containing inorganic-organic hybrid polyhedral oligomeric silsesquioxane (POSS1) were prepared by bulk free radical polymerization. XRD and TEM studies indicate that POSS1 is completely dispersed at molecular level in PS matrix when 1 wt% POSS1 is introduced, while some POSS1-rich nanoparticals are present when content of POSS1 is beyond 3 wt%. GPC results show that molecular weight of the PS/POSS1 nanocomposites are increased with addition of POSS1. TGA and TMA data show the thermal stabilities of PS/POSS1 nanocomposites have been improved compared to neat PS. The PS/POSS1 nanocomposites also display higher glass transition temperatures (Tg) in comparison with neat PS. Viscoelastic properties of PS/POSS1 nanocomposites were investigated by DMTA. The results show the storage modulus (E′) values (temperature>Tg) and the loss factor peak values of the PS/POSS1 nanocomposites are higher than that of neat PS. Mechanical properties of the PS/POSS1 nanocomposites are improved compared to the neat PS.  相似文献   

10.
The poly(styrene‐co‐octavinyl‐polyhedral oligomeric silsesquioxane) (PS–POSS) organic–inorganic hybrid nanocomposites containing various percent of POSS were prepared via one‐step free radical polymerization and characterized by FTIR, high‐resolution 1H NMR, 29Si NMR, GPC, DSC, and TGA technologies. The POSS contents in these nanocomposites were determined using FTIR calibration curve. The result shows that the POSS contents in nanocomposites can be tailored by varying the POSS feed ratios. On the basis of the POSS contents in the nanocomposites and the 1H NMR spectra, the number of reacted vinyl groups of each octavinyl‐POSS macromonomer were calculated to be 6–8. DSC and TGA measurements indicate that the incorporation of POSS into PS homopolymer can apparently improve the thermal properties of the polymeric materials. The dramatic Tg and Tdec increases are mainly due to the formation of star and low cross‐linking structure of the nanocomposites, where POSS cores behave as the joint points and hinder the motion and degradation of the polymeric chains. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007  相似文献   

11.
A series of cyanate ester resin (CE) based organic–inorganic hybrids containing different contents (0, 5, 10, 15 and 20 wt%) of epoxy‐functionalized polyhedral oligomeric silsesquioxane (POSS‐Ep) were prepared by casting and curing. The hybrid resin systems were studied by the gel time test to evaluate the effect of POSS‐Ep on the curing reactivity of CE. The impact and flexural strengths of the hybrids were investigated. The micromorphological, dynamic mechanical and thermal properties of the hybrids were studied by SEM, dynamic mechanical analysis (DMA) and TGA, respectively. Results showed that POSS‐Ep prolonged the gel time of CE. CE10 containing 10 wt% POSS‐Ep displayed not only the optimum impact strength but the optimum flexural strength. SEM results revealed that the improvement of mechanical properties was attributed to the large amount of tough whirls and fiber‐like pull‐outs observed on the fracture surfaces of CE10. DMA results indicated that POSS‐CE tended to decrease E′ of the hybrids in the glassy state but to increase E′ of the hybrids in the rubbery state. TGA results showed that CE10 also possesses the best thermal stability. The initial temperature of decomposition (Ti) of CE10 is 426 °C, 44 °C higher than that of pristine CE. © 2013 Society of Chemical Industry  相似文献   

12.
The isothermal crystallization of HDPE/POSS (polyhedral oligomeric silsesquioxane) nanocomposites (POSS content varying from 0.25 to 10 wt %) was studied using differential scanning calorimetry (DSC) technique. The Avrami model could successfully describe the isothermal crystallization behavior of the nanocomposites. The value of Avrami exponent (n) varies between 2 and 2.5 for all the compositions studied. For a given composition, the values vary with crystallization temperature and in general increased with POSS content up to 1 wt % POSS content and decreased thereafter. The presence of POSS was found to increase the rate of crystallization, which manifested itself in the increased value of the Avrami rate constant (K) and reduced value of crystallization half‐time (t1/2). The rate of crystallization peaked at 1 wt % POSS content and was almost constant at higher POSS loadings. X‐ray diffraction studies revealed that POSS exists as nanocrystals in HDPE matrix while some POSS gets dispersed at molecular level too. It is observed that only the POSS dispersed at molecular level acts as a nucleating agent while the POSS nanocrystals do not affect the crystallization process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007  相似文献   

13.
A series of poly(vinyl pyrrolidone‐co‐octavinyl polyhedral oligomeric silsesquioxanes) (PVP‐POSS) organic–inorganic hybrid nanocomposites containing different percentages of POSS were prepared via free radical polymerization and characterized by FTIR, high‐resolution 1H‐NMR, solid‐state 29Si‐NMR, GPC, DSC, and TGA. POSS contents in these nanocomposites can be effectively controlled by varying the POSS feed ratios which can be accurately quantified by FTIR curve calibration. On the basis of 29Si‐NMR spectra, average numbers of reacted vinyl groups of each octavinyl‐POSS macromer are calculated to be 5–7, which depends on POSS feed ratios. Both GPC and DSC results indicate that these nanocomposites display network structure and the degree of crosslinking increases with the increase of the POSS content. The incorporation of POSS into PVP significantly improves their thermal properties (Tg and Tdec) primarily due to crosslinking structure and dipole–dipole interaction between POSS cores and PVP carbonyl groups. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

14.
Yuan-Jyh Lee 《Polymer》2004,45(18):6321-6331
We have successfully synthesized a novel benzoxazine ring-containing polyhedral oligomeric silsesquioxane (BZ-POSS) monomer by two routes: (1) hydrosilylation of a vinyl-terminated benzoxazine using the hydro-silane functional group of a polyhedral oligomeric silsesquioxane (H-POSS) and (2) reaction of a primary amine-containng POSS (Amine-POSS) with phenol and formaldehyde. The benzoxazine-containing POSS (BZ-POSS) monomer can be copolymerized with other benzoxazine monomers through ring-opening polymerization under conditions similar to that used for polymerizing pure benzoxazines. Thermal properties of these POSS-containing organic/inorganic polybenzoxazine nanocomposites have been improved over the pure polybenzoxazine analyzed by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The BZ-POSS monomer is poorly miscible with the benzoxazine monomer and tends to aggregate and forms its own domains, both before and after polymerization. At a higher BZ-POSS content, gross aggregation occurs and results in a lower than expected improvement in the thermal properties.  相似文献   

15.
Yonghong Liu 《Polymer》2006,47(19):6814-6825
A readily available octa(3-chloropropyl) polyhedral oligomeric silsesquioxane (POSS) [(ClCH2CH2CH2)8Si8O12] framework was used to prepare octa(3-hydroxypropyl) POSS [(HOCH2CH2CH2)8Si8O12], which was further used as an initiator to synthesize star poly(?-caprolactone) with POSS core via ring-opening polymerization catalyzed by Stannous (II) octanoate [Sn(Oct)2]. The organic-inorganic star PCLs were characterized by means of gel permeation chromatograph (GPC), Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR). The wide-angle X-ray diffraction (WAXRD) experiments indicate that the presence of POSS cores did not alter the crystal structure of PCL. The star PCLs exhibited enhanced melting temperatures in comparison with the linear counterpart. The isothermal crystallization kinetics shows that both the overall crystallization rate and the spherulitic growth rate of the star PCLs increased with increasing the concentration of POSS (or with decreasing the arm lengths of the stars). The fold surface free energy of the star PCLs decreased with increasing the concentration of POSS. These results could be interpreted based on the effect of the heterogeneous nucleation of POSS cores, which accelerates the process of crystallization.  相似文献   

16.
为了提高环氧树脂的耐热性,采用笼型倍半硅氧烷(POSS)改性双酚A型环氧树脂E51,得到有机无机杂化树脂。采用Ozawa和Kissinger两种方法研究了杂化树脂/4,4′-二氨基苯砜(DDS)体系的固化反应动力学。TGA分析表明,POSS的加入提高了E51/DDS固化树脂体系的热性能。  相似文献   

17.
5,11,14,17‐Tetraanilinooctaphenyl double decker silsesquioxane, a well‐defined tetraamino polyhedral oligomeric silsesquioxane (POSS), was synthesized in this work. This novel tetrafunctional POSS amine was employed to prepare polyimide nanocomposites. It was found that the hybrid polyimide nanocomposites displayed nanostructures in which the POSS component was aggregated into spherical microdomains with a diameter of 40 ? 80 nm. Compared to unmodified polyimide, the POSS‐containing polyimide nanocomposites displayed improved thermal stability and surface hydrophobicity. Owing to the introduction of the POSS microdomains, the dielectric constants of the polyimide nanocomposites were significantly decreased in comparison with plain polyimide. © 2017 Society of Chemical Industry  相似文献   

18.
Polyhedral oligomeric silsesquioxane (POSS)/poly(ethylene glycol) diacrylate (PEGDA) biodegradable nanohybrids were synthesized in which modified POSS was chemically incorporated into the polymer chain as reinforcing nanoparticles during a blue light photocuring process. First, POSS diacrylate (POSSA) was prepared by the simple reaction of POSS with acryloyl chloride and the product obtained was identified by Fourier transform infrared spectroscopy and 13C NMR. Second, POSSA was incorporated into the PEGDA matrix in various concentrations in the presence as well as the absence of a reactive diluent. Finally, some characterizations such as XRD, TEM, equilibrium swelling, viscoelastic behavior, mechanical properties and cytocompatibility tests were performed to evaluate the effectiveness of these nanoparticles within the PEGDA polymer matrix. The results revealed that POSSA acted as a crosslinking agent as well as an inorganic nanofiller to enhance the properties of PEGDA and also that the most effective content of these nanoparticles should be optimized in the range 1.5–3 wt%. This study suggests acrylated POSS as an effective nanoparticle to promote the efficiency of photocured nanohybrids used in medical applications. © 2020 Society of Chemical Industry  相似文献   

19.
Dielectric techniques, including thermally stimulated depolarization currents (TSDC, ?150 to 30°C) and, mainly, broadband dielectric relaxation spectroscopy (DRS, 10?2 – 106 Hz, ?150 to 150°C) were employed, next to differential scanning calorimetry (DSC), to investigate molecular dynamics in rubbery epoxy networks prepared from diglycidyl ether of Bisphenol A (DGEBA) and poly(oxypropylene)diamine (Jeffamine D2000, molecular mass 2000) and modified with polyhedral oligomeric silsesquioxanes (POSS) units covalently bound to the chains as dangling blocks. Four relaxations were detected and analyzed: in the order of increasing temperature at constant frequency, two local, secondary γ and β relaxations in the glassy state, the segmental α relaxation associated with the glass transition and the normal mode relaxation, related with the presence of a dipole moment component along the Jeffamine chain contour. Measurements on pure Jeffamine D2000 helped to clarify the molecular origin of the relaxations observed. A significant reduction of the magnitude and a slight acceleration of the α and of the normal mode relaxations were observed in the modified networks. These results suggest that a fraction of polymer is immobilized, probably at interfaces with POSS, due to constraints imposed by the covalently bound rigid nanoparticles, whereas the rest exhibits a slightly faster dynamics due to increaseof free volume resulting from loosened molecular packing of the chains (plasticization by the bulky POSS units).The increase of free volume is rationalized by density measurements. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

20.
Star‐shaped amphiphilic polymeric surfactants comprising a hydrophobic polyhedral oligomeric silsesquioxane (POSS) core and hydrophilic poly(ethylene glycol) (PEG) arms with various chain lengths are successfully synthesized using copper(I)‐catalysed azide–alkyne cycloaddition (CuAAC) click reaction. Their chemical structures and molecular characteristics are clearly confirmed using Fourier transform infrared and 1H NMR spectroscopies and gel permeation chromatography, and no homopolymer is found after CuAAC click reaction. Aqueous solutions of these star‐shaped polymers have been investigated using atomic force and transmission electron microscopies and dynamic light scattering studies and it is found that they can self‐assemble into micelles. The sizes of the micelles can be adjusted by the length of the PEG arms, where longer chains not only lead to increased micelle sizes, but also reduce the contact angle values. Moreover, the melting points and root mean square roughness of the obtained star‐shaped polymers are slightly increased on increasing the chain length of the PEG arms. © 2017 Society of Chemical Industry  相似文献   

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