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1.
Poly(methylphenylsiloxane)–poly(methyl methacrylate) interpenetrating polymer networks (PMPS–PMMA IPNs) were prepared by in situ sequential condensation of poly(methylphenylsiloxane) with tetramethyl orthosilicate and polymerization of methyl methacrylate. PMPS–PMMA IPNs were characterized by infrared (IR), differential scanning calorimetry (DSC), and 29Si and 13C nuclear magnetic resonance (NMR). The mobility of PMPS segments in IPNs, investigated by proton spin–spin relaxation T2 measurements, is seriously restricted. The PMPS networks have influence on the average activation energy Ea,av of MMA segments in thermal degradation at initial conversion. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1717–1724, 1999  相似文献   

2.
A facile preparation of polyimide–silica gel hybrids by the simultaneous in-situ formation of polyimides during the hydrolysis–condensation of tetramethoxysilane (TMOS) is reported here. The hydrolysis and condensation of TMOS was carried out in a solution of DMAc containing 5% LiCl, CaCl2 or ZnCl2 and the seven-membered cyclic polyimide intermediate. The seven-membered cyclic intermediates, precursors of polyimides, were derived from the low-temperature polycondensation of dianhydrides [benzophenonetetracarboxylic dianhydride (BTDA), pyromellitic dianhydride (PMDA), and 4,4-bis(hexafluoroisopropylidene)phthalic dianhydride (6FDA)] and di-isocyanates [isophorone di-isocyanate (IPDI), toluene di-isocyanate (TDI), hexamethylene di-isocyanate (HDI) and 4,4′-diphenylmethane di-isocyanate (MDI)]. These intermediates could readily be converted to the corresponding polyimides. Films were cast from the resulting mixtures and the solvent was gradually evaporated at 130 °C to result in the formation of clear, transparent, pale yellow or amber-colored hybrid films in which the salts were dispersed at the molecular level. Pyrolysis of polyimide–silica gel hybrids at 600 °C gave mesoporous silica. Silica gel obtained from hybrids HPI-8 (containing no salt) and HPI-11 (containing ZnCl2) had a pore radius (BJH method) of 2.9 nm, while that from hybrid HPI-9 (containing LiCl) had a pore radius of 11.4 nm. The surface areas (BET method) obtained were 203 m2 g−1, 19 m2 g−1 and 285 m2 g−1, while the pore volumes were 0.373 cm3 g−1, 0.158 cm3 g−1 and 0.387 cm3 g−1, respectively, for samples obtained from hybrids HPI-8, HPI-9 and HPI-11. © 1997 by John Wiley & Sons, Ltd.  相似文献   

3.
Poly(methyl methacrylate)–silica hybrid materials (PMMA–SiO2) were prepared by in situ polycondensation of alkoxysilane in the presence of trialkoxysilane‐functional PMMA. Infrared, differential scanning calorimetry, 29Si and 13C nuclear magnetic resonance spectroscopy, and thermogravimetric analysis were used to study the PMMA–SiO2 hybrids. The effects of the content and kind of the alkoxysilane on the dynamics and stability of the PMMA–SiO2 hybrids were investigated in this study.The dynamics of SiO2within hybrids were investigated with 29Si–1H cross‐polarization. The spin‐diffusion path length was on a nanometer scale estimated with the spin–lattice relaxation time in the rotating frame (T). The apparent activation energies for the degradation of the hybrids under air and nitrogen were evaluated by the van Krevelen method. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1972–1980, 2000  相似文献   

4.
The chemically covalent polyethylenimine–siloxane hybrids doped with various amounts of ortho‐phosphoric acid (H3PO4) were prepared and characterized by FTIR, DSC, TGA, and solid‐state NMR spectra. The protonic conduction behavior of these materials was also investigated by means of impedance measurements. These observations indicate that the hydrogen bonding and protonic interactions exist between the dopant H3PO4 and the hybrid host, resulting in an increase in T g of polyethylenimine segments. These hybrids are thermally stable up to 200 °C from TGA analysis. Conductivity studies show an Arrhenius behavior characteristic and the Grotthus‐like proton conduction, and a high conductivity of 10?2–10?3 S cm?1 at 110 °C in dry atmosphere for the hybrid membrane with H3PO4/EI of 0.5. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2135–2144, 2006  相似文献   

5.
Microphase separation in poly(acrylonitrile–butadiene–styrene) (ABS) was studied as a function of the butadiene content and method of preparation with electron spin resonance (ESR) spectra of nitroxide spin probes. Results for the ABS polymers were evaluated by comparison with similar studies of the homopolymers polybutadiene (PB), polystyrene (PS), and polyacrylonitrile (PAN) and the copolymers poly(styrene‐co‐acrylonitrile) (SAN) and poly(styrene‐co‐butadiene) (SB). Two spin probes were selected for this study: 10‐doxylnonadecane (10DND) and 5‐doxyldecane (5DD). The probes varied in size and were selected because their hydrocarbon backbone made them compatible with the polymers studied. The ESR spectra were measured in the temperature range 120–420 K and were analyzed in terms of line shapes, line widths, and hyperfine splitting from the 14N nucleus; the appearance of more than one spectral component was taken as an indication of microphase separation. Only one spectral component was detected for 10DND in PB, PS, and PAN and in the copolymers SAN and SB. In contrast, two spectral components differing in their dynamic properties were detected for both probes in the three types of ABS samples studied and were assigned to spin probes located in butadiene‐rich domains (the fast component) and SAN‐rich domains (the slow component). The behavior of the fast component in ABS prepared by mass polymerization suggested that the low‐Tg (glass‐transition‐temperature) phase was almost pure PB. The corresponding phase in ABS prepared by emulsion grafting also contained styrene and acrylonitrile monomers. A redistribution of the spin probes on heating occurred with heating near the Tg of the SAN phase, suggesting that the ABS polymers as prepared were not in thermodynamic equilibrium. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 415–423, 2002; DOI 10.1002/polb.10109  相似文献   

6.
Poly(methylphenylsiloxane)–poly(methyl methacrylate) graft copolymers (PSXE-g-PMMA) were prepared by condensation reaction of poly(methylphenylsiloxane)-containing epoxy resin (PSXE) with carboxyl-terminated poly(methyl methacrylate) (PMMA), and they were characterized by gel permeation chromatography (GPC), infrared (IR), and 29Si and 13C nuclear magnetic resonance (NMR). The microstructure of the PSXE-g-PMMA graft copolymer was investigated by proton spin–spin relaxation T2 measurements. The thermal stability and apparent activation energy for thermal degradation of these copolymers were studied by thermogravimetry and compared with unmodified PMMA. The incorporation of poly(methylphenylsiloxane) segments in graft copolymers improved thermal stability of PMMA and enhanced the activation energy for thermal degradation of PMMA. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2521–2530, 1998  相似文献   

7.
In this work, we present values for the Mark–Houwink–Sakurada (MHS) and Stockmayer–Fixman (SF) constants for a series of homopolymers of para‐substituted styrenes (4‐X‐styrene; X = OCH3, OCH2CH3, CH3, F, Cl, and Br) in THF at room temperature. The respective values of K (in 10−5 dL/g) and α were: 0.685 and 13.2; 0.662 and 14.1; 0.740 and 8.41; 0.781 and 5.24; 0.726 and 8.95; 0.700 and 7.79. The respective values for Kθ (in 10−4 dL/g) and K' (in 10−7 dL/g) were: 6.01 and 16.1; 6.22 and 9.07; 7.64 and 17.4; 5.59 and 23.7; 6.29 and 17.3; 4.44 and 10.3. These constants were measured using size‐exclusion chromatography with on‐line viscometry. As part of this work, we investigate the applicability of common model fitting procedures to this method of measuring MHS/SF constants and the effect of uncertainties in their estimated values on the accuracy of molecular weight analysis. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2557–2570, 1999  相似文献   

8.
A series of poly(amide–imide)s IIIa–m containing flexible isopropylidene and ether groups in the backbone were synthesized by the direct polycondensation of 4,4′‐[1,4‐phenylenebis(isopropylidene‐1,4‐phenyleneoxy)]dianiline (PIDA) with various bis(trimellitimide)s IIa–m in N‐methyl‐2‐pyrrolidone (NMP) using triphenyl phosphite and pyridine as condensing agents. The resulting poly(amide–imide)s had inherent viscosities in the range of 0.80–1.36 dL/g. Except for those from the bis(trimellitimide)s of p‐phenylenediamine and benzidine, all the polymers could be cast from DMAc into transparent and tough films. They exhibited excellent solubility in polar solvents. The 10% weight loss temperatures of the polymers in air and in nitrogen were all above 495°C, and their Tg values were in the range of 201–252°C. Some properties of poly(amide–imide)s III were compared with those of the corresponding poly(amide–imide)s V prepared from the bis(trimellitimide) of diamine PIDA and various aromatic diamines. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 69–76, 1999  相似文献   

9.
The crystalline–noncrystalline structure and its structural changes from thermal treatments for ethylene ionomers have been investigated with solid‐state 13C and 23Na NMR spectroscopy. 13C spin–lattice relaxation time (T1C) measurements reveal that as‐received ethylene ionomers have much enhanced molecular mobility in the crystalline region in comparison with conventional polyethylene samples. By appropriate annealing, however, polyethylene‐like morphological features reflecting T1C behavior can also be observed. 13C spin–spin relaxation time (T2C) measurements for the noncrystalline region reveal the existence of two components with different T2C values, and these two components have been assigned to the crystalline–amorphous interfacial and rubbery–amorphous components. These results indicate that the structure of the major part of the noncrystalline region in the ethylene ionomers is similar to that of bulk‐crystallized polyethylene samples, regardless of possible ionic aggregates. The origin of the lower temperature endothermic peak in the heating process of the differential scanning calorimetry curve observed for the as‐received sample has also been examined somewhat in detail. As a result, it is proposed that the melting of smaller crystallites produced during storage at room temperature is the origin of the lower temperature peak. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1142–1153, 2002  相似文献   

10.
Different chlorine-free alkylaluminum compounds were active cocatalysts for ethylene polymerization in the presence of 1,4-bis(2,6-diisopropylphenyl)-acenaphthenediimine-dichloronickel (II) (1). The combination of 1 with trimethylaluminum or triisobutylaluminum produced catalytically active species that polymerized ethylene with productivities up to 469 kgpolymer/(molNi · h). The activity of the catalytic system and the properties of the polymeric materials were influenced strongly by the reaction temperature. The polymers had a high molecular weight (up to 642 × 103 g · mol−1), and the molecular weight increased with the reaction time. The polyethylenes were branched, and the branching could be modulated by the proper choice of reaction parameters. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4656–4663, 1999  相似文献   

11.
A study on poly(tetrafluoroethylene) (PTFE) reinforced with tetraethoxysilanes (TEOS) derived SiO2 is described. It included the manufacturing process of SiO2‐reinforced PTFE and the effects of silylation agent on the properties of the hybrid material, such as porosity, hydrophobic, thermal resistance, dielectric and mechanical properties, and microstructure. PTFE/SiO2 hybrids of 50 wt % SiO2 loading were prepared via a sol–gel process and were shaped by a two‐roll milling machine. Trimethylchlorosilane and hexamethydisilazane were used as the silylation agents. Our results showed that the water absorption and dielectric loss of PTFE/SiO2 hybrid had significantly improved with silylation agent. The silylation process replaced Si? OH with Si? CH3 on the surface of the TEOS‐derived silica colloidal particle. The existence of trimethylsilyl [? Si(CH3)3] on the surface of the modified PTFE/SiO2 hybrid was confirmed via infrared and solid‐state 29Si magic‐angle spinning nuclear magnetic resonance spectra. Nitrogen‐sorption techniques were used to characterize the modified and unmodified PTFE/SiO2 hybrids. The microstructure of SiO2 in the matrix was also evaluated with scanning electron microscopy and transmission electron microscopy. Our results showed that the silylated sol–gel‐derived PTFE/SiO2 hybrids had exhibited high porosity (53.7%) with nanosize pores (10–40 nm) and nanosize colloidal particles (20–50 nm). This manifests itself as have the ultralow dielectric properties (Dk = 1.9 and Df = 0.0021), low coefficient of thermal expansion (66.5 ppm/°C), high tensile modulus (141 MPa), excellent thermal resistance (Td = 612 °C), and an increased hydrophobia (θ = 114°); moreover, the hydrophobic property of the PTFE/SiO2 hybrid was thermally stable up to 400 °C. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1789–1807, 2004  相似文献   

12.
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   

13.
The graft copolymerization of undecylenic acid onto acrylonitrile–butadiene–styrene terpolymer (ABS) was initiated with benzoyl peroxide (BPO) in a 1,2‐dichloroethane solution. IR spectra confirmed that undecylenic acid was successfully grafted onto the ABS backbone. The influence of the concentrations of undecylenic acid, BPO, and ABS on the graft copolymerization was studied. A reaction mechanism was proposed: the grafting most likely took place through the addition of poly(undecylenic acid) radicals to the double bond of the butadiene region of ABS. A monomer cage effect on the graft reaction was observed to depend on the 1.5 power of the monomer concentration from the experimental results of the initial rate of graft copolymerization. The initial rate of graft copolymerization was written as Rp = 1.77 × 10−3[P][I2][M]2.5/([P]+2.75[M]2.5)2. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 486–494, 2001  相似文献   

14.
The influence of an in situ‐grown, sol → gel‐derived silicon oxide filler on mechanical, gas permeation and solvent affinity properties of Surlyn® materials, and melt processibility of Surlyn®/[silicon oxide] hybrid resin, was studied. Tensile modulus increases while elongation‐at‐break decreases with increasing silicon oxide uptake. He gas permeation vs. pressure profiles imply dual mode sorption. Swelling in n‐hexane, 1‐PrOH and xylene decreases as silicon oxide loading increases, the highest uptake being that of xylene. [Surlyn®Zn+2]/[silicon oxide] has better solvent resistance than the H‐form hybrid for each solvent. Affinity of the Zn‐form hybrid for xylene is considerably greater than that for 1‐PrOH and n‐hexane. Melt flow index of the filled H‐form is lower than that of the unfilled H‐form but higher than that of the partially Zn neutralized unfilled form. FTIR analysis of hybrids previously subjected to the melt flow index experiment shows that the silicon oxide phase remained intact but that the high temperatures drove condensation reactions between SiOH groups. After in situ sol–gel reactions and drying [Surlyn®‐H]/[silicon oxide] flakes were passed through an extruder to assess the effect on silicon oxide structure of melt‐processing conditions. All silicon oxide IR fingerprint bands for the processed hybrid persist, the spectrum closely resembling that of a nonextruded hybrid including the signature of Si–OH groups. 29Si solid‐state NMR spectroscopy was used to probe degree of molecular connectivity within the silicon oxide phase. The spectrum is consistent with those of nonextruded hybrids in that Si atom coordination around SiO4 units is predominantly Q3 and Q4, the bias in the distribution toward Q3 being in harmony with the IR results. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 143–154, 1999  相似文献   

15.
The glass transition temperatures Tg of butyl acrylate–methyl methacrylate copolymers obtained by free radical polymerization in 3 and 5 mol/L benzene solution have been measured using differential scanning calorimetry (DSC) and the values have been correlated using Johnston's equation with inter‐intramolecular copolymer structure. From the data calculated with copolymer prepared at low conversion, the variation of glass transition temperature with copolymer conversion has been theoretically predicted. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2512–2520, 1999  相似文献   

16.
Novel polyesteramides were synthesized by copolymerization in bulk of 5-(4,5-dihydro-1,3-oxazol-2-yl)-1-pentanol and various cyclic dicarboxylic acid anhydrides at temperatures varying between 120 and 200°C. The polymers resulting from polycondensation were characterized by means of 1H–NMR, FTIR, MALDI–TOF–MS, SEC, and DSC. The glass transition temperatures, Tg, of the copolymers were varied between −28 and +31°C as a function of the anhydride type. Molecular weights, Mw, were dependent on reaction temperature, reaction time, and anhydride type. Spectroscopic investigation of reaction products and esteramide model compounds provided evidence for imide by-product formation, which accounts for the low degree of polymerization. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3367–3376, 1999  相似文献   

17.
Butadiene‐isoprene copolymerization with the system V(acac)3‐MAO was examined. Crystalline or amorphous copolymers were obtained depending on isoprene content. Both butadiene and isoprene units exhibit a trans‐1,4 structure and are statistically distributed along the polymer chain. Polymer microstructure, comonomer composition, and distribution along the polymer chain were determined by 13C and 1H NMR analysis. The thermal and X‐ray behaviors of the copolymers were also investigated and compared with results from solid‐state 13C NMR experiments. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4635–4646, 2007  相似文献   

18.
Electronic structures of the weakly bound Rn2 were calculated by the two‐component Møller–Plesset second‐order perturbation and coupled‐cluster methods with relativistic effective core potentials including spin–orbit operators. The calculated spin–orbit effects are small, but depend strongly on the size of basis sets and the amount of electron correlations. Magnitudes of spin–orbit effects on De (0.7–3.0 meV) and Re (−0.4∼−2.2 Å) of Rn2 are comparable to previously reported values based on configuration interaction calculations. A two‐component approach seems to be a promising tool to investigate spin–orbit effects for the weak‐bonded systems containing heavy elements. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 72: 139–143, 1999  相似文献   

19.
This research was focused on the design and execution of new synthetic routes to low‐temperature‐curable poly(silarylene–siloxane)polyimides. The synthesis of individual oligoimide and silarylene–siloxane blocks was followed by hydrosilylation polymerization to produce crosslinked copolymers. The silarylene–siloxane and polyimide blocks were structurally characterized by IR and 1H NMR spectroscopy and size exclusion chromatography. The high‐temperature resistance of the copolymers was evaluated through the measurement of heat distortion temperatures (THD's) via thermomechanical analysis and by the determination of the weight loss at elevated temperatures via thermogravimetric analysis. Glass‐transition temperatures (Tg's) of the silarylene–siloxane segments were measured by differential scanning calorimetry. Hydrosilylation curing was conducted at 60 °C in the presence of chloroplatinic acid (H2PtCl6). The copolymers displayed both high‐temperature resistance and low‐temperature flexibility. We observed Tg of the silarylene–siloxane segment as low as ?77 °C and THD of the polyimide segment as high as 323 °C. The influence of various oligoimide molecular weights on the properties of copolymers containing the same silarylene–siloxane was examined. The effect of various silarylene–siloxane molecular weights on the properties of copolymers containing the same oligoimide was also examined. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4922–4932, 2005  相似文献   

20.
This work reports on the comprehensive calculation of the NMR one‐bond spin–spin coupling constants (SSCCs) involving carbon and tellurium, 1J(125Te,13C), in four representative compounds: Te(CH3)2, Te(CF3)2, Te(C?CH)2, and tellurophene. A high‐level computational treatment of 1J(125Te,13C) included calculations at the SOPPA level taking into account relativistic effects evaluated at the 4‐component RPA and DFT levels of theory, vibrational corrections, and solvent effects. The consistency of different computational approaches including the level of theory of the geometry optimization of tellurium‐containing compounds, basis sets, and methods used for obtainig spin–spin coupling values have also been discussed in view of reproducing the experimental values of the tellurium–carbon SSCCs. Relativistic corrections were found to play a major role in the calculation of 1J(125Te,13C) reaching as much as almost 50% of the total value of 1J(125Te,13C) while relativistic geometrical effects are of minor importance. The vibrational and solvent corrections account for accordingly about 3–6% and 0–4% of the total value. It is shown that taking into account relativistic corrections, vibrational corrections and solvent effects at the DFT level essentially improves the agreement of the non‐relativistic theoretical SOPPA results with experiment. © 2016 Wiley Periodicals, Inc.  相似文献   

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