The influence of the 2-, 3-, and 4-OH phenols on the type of interaction with Co-exchanged montmorillonite and thermal properties of these materials were studied. The results of XRD, IR, and thermal (TG, DTG) analysis show that organic species are intercalated into the interlayer space of montmorillonite. Thermal decomposition in the temperature interval 20?C700?°C of studied samples with 2- and 3-hydroxyphenol proceeds in three steps (the release of adsorbed H2O molecules, combustion/desorption of protonated hydroxy phenols and dehydroxylation), while the sample with 4-hydroxyphenol decompose in four steps (the new peak at ~222?°C corresponds to directly coordinated organic species). The effect of different position of the hydroxyl groups on the phenol ring on the thermal decomposition is evident. 相似文献
Tris(dimethylsilyl)methyl lithium, (HSiMe2)3CLi, reacts with allyl, phenyl, benzyl, n‐propyl and n‐butyl glycidyl ethers in THF at ‐5 °C to give 1‐oxa‐2‐silacyclopentane derivatives. It seems that ring closure is facilitated by conversion of the Si? H bond into an Si? O bond. Glycidyl methacrylate (GM) random copolymers with 4‐methyl‐ and 4‐methoxy styrene, synthesized by solution free radical polymerization at 70 (±1) °C with α,α‐azobis(isobutyronitrile) (AIBN) as initiator, contained pendant epoxide functions. Treatment of these with (HSiMe2)3CLi did not lead to intramolecular nucleophilic attack as found for simple epoxides. 相似文献
Das Gemisch aus dem E- und Z-Isomeren des [2,2-Dimethyl-1-(trimethylsiloxy)propyliden]phosphans ist bei 20°C im diffusen Tageslicht nicht beständig; im Laufe einiger Wochen scheidet sich das Dimere 2,4-Di(tert.butyl)-2,4-bis(trimethylsiloxy)-1,3-diphosphetan 1 ab. Die Verbindung kristallisiert triklin in der Raumgruppe P1 mit a = 1044,5(3); b = 647,8(2); c = 883,8(2) pm; α = 100,39(2); β = 102,84(2); γ = 93,70(2)°; Z = 1. Wie die Röntgenstrukturanalyse (R = 3,7%) zeigt, besitzt das Molekül als kristallographisches Symmetrieelement ein Inversionszentrum. Die mit 190,3 und 189,5 pm langen P? C? Abstände weisen auf eine beträchtliche Ringspannung hin; in Lösung zerfällt das Diphosphetan wieder leicht in das E- und Z-isomere Monomere. Weitere charakteristische Bindungsabstände und -winkel sind: C1? O 140,8; Si? O 163,5 pm sowie P? C1? P' 92,7; C1? P? C1′ 87,3; C1? O? Si 146,2° Acyl and Alkylidene Phosphines. XIII. Molecular and Crystal Structure of 2,4-Di(tert.-butyl)-2,4-bis(trimethylsiloxy)-1,3-diphosphetane Kept at 20°C in diffuse daylight the mixture of the E and Z isomer of [2,2-dimethyl-1-(trimethylsiloxy)propylidene]phosphine is not stable; within several weeks the dimer 2,4-di(tert.-butyl)-2,4-bis(trimethylsiloxy)-1,3-diphosphetane 1 precipitates. The compound crystallizes triclinic in the space group P1 with a = 1044.5(3); b = 647.8(2); c = 883.8(2) pm; α = 100.39(2); β = 102.84(2); γ = 93.70(2)°; Z = 1. As shown by an x-ray structure determination (R = 3.7%) the molecule has a centre of symmetry. The long P? C distances (189.5 and 190.3 pm) indicate a strained ring-system; in solution the diphosphetane decomposes again to form the E and Z isomeric monomer. Further characteristic bond distances and angles are: C1? O 140.8; Si? O 163.5 pm as well as P? C1? P' 92.7; C1? P? C1′ 87.3; C1? O? Si 146.2°. 相似文献
The thermal decomposition of nitrocellulose (NC) 12.1% N, has been studied with regard to kinetics, mechanism, morphology and the gaseous products thereof, using thermogravimetry (TG), differential thermal analysis (DTA), IR spectroscopy, differential scanning calorimetry (DSC) and hot stage microscopy. The kinetics of the initial stage of thermolysis ofNC in condensed state has been investigated by isothermal high temperature infrared spectroscopy (IR). The decomposition ofNC in KBr matrix in the temperature range of 142–151°C shows rapid decrease in O?NO2 band intensity, suggesting that the decomposition of NC occurs by the rupture of O?NO2 bond. The energy of activation for this process has been determined with the help of Avrami-Erofe'ev equation (n=1) and is ≈188.35 kJ·mol?1. Further, the IR spectra of the decomposition products in the initial stage of thermal decomposition ofNC, indicates the presence of mainly NO2 gas and aldehyde. 相似文献
Abstract Postpolymerization of vinyl monomers initiated by pendant peroxycarbonate groups of grafted polymer chains on carbon black (CB) was investigated. The grafting of polymers having pendant peroxycarbonate groups onto CB was achieved by the trapping of polymer radicals formed by the thermal decomposition of copolymers of t-butylperoxy-2-methacryloyloxyethyl-carbonate (HEPO) with vinyl monomers such as vinyl acetate (VAc), styrene (St) and methyl methacrylate (MMA). The copolymers having pendant peroxycarbonate groups were prepared by copolym-erization of HEPO with vinyl monomers using azo initiator under irradiation of UV light at room temperature. The amount of remaining pendant peroxycarbonate groups of the poly(VAc-co-HEPO)-grafted CB obtained from the reaction at 90°C was maximum and decreased above the temperature. Furthermore, the postpolymerization of vinyl monomers, such as St, MMA, and VAc was initiated in the presence of poly(VAc-co-HEPO)-grafted and poly(St-co-HEPO)-grafted CB and the corresponding polymers were postgrafted onto CB to give branched polymer-grafted CB. The percentage of poly(St)-postgrafting (proportion of post-grafted poly(St) to poly(MMA-co-HEPO)-grafted CB used) increased with increasing polymerization time, but became constant at 20% after 4 hours. 相似文献
Abstract Using UV light as the energy source and polystyrene- (PS-) or polymethyl methacrylate- (PMMA-) macroinitiators with active aromatic or aliphatic thiyl end groups, PS-PMMA and PMMA-PEA (poly-ethyl acrylate) block copolymers were synthesized. The molecular weights of both block copolymers increased with increasing reaction time. The reactivity of macroinitiators depended on the type of thiyl groups and monomer and not on the length of the polymer chain. The most reactive were macroinitiators containing resonance stabilized non-substituted or substituted aromatic end groups. The decomposition of the macroinitiators took place over the formation of the thiyl radical and macroradical. The bond length, the bond dissociation energy, and the bond order of macroradical end groups were calculated. The most reactive monomer was ethyl acrylate; the less reactive was styrene. The structure, the molecular weight, and the Tg of the styrene-acrylate block copolymers were determined. The PMMA/PEA block copolymer had two of block's Tgs, the first at 105°C, the second at ?24°C, and a third at 16°C which probably represents contacting segments. 相似文献
Synthesis and Structure of Lithium Tris(trimethylsilyl)silanide · 1,5 DME Lithium tris(trimethylsilyl)silanide · 1,5 DME 2a synthesized from tetrakis(trimethylsilyl)silane 1 [6] and methyllithium in 1,2-dimethoxyethane , crystallizes in the monoclinic space group P21/c with following dimensions of the unit cell determined at a temperature of measurement of ?120 ± 2°C: a = 1 072.9(3); b = 1 408.3(4); c = 1 775.1(5) pm; β = 107.74(2)°; 4 formula units (Z = 2). An X-ray structure determination (Rw = 0.040) shows the compound to be built up from two [lithium tris(trimethylsilyl)silanide] moieties which are connected via a bridging DME molecule. Two remaining sites of each four-coordinate lithium atom are occupied by a chelating DME ligand. The Li? Si distance of 263 pm is considerably longer than the sum of covalent radii; further characteristic mean bond lengths and angles are: Si? Si 234, Li? O 200, O? C 144, O?O (biß) 264 pm; Si? Si? Si 104°, Li? Si? Si 107° to 126°; O? Li? O (inside the chelate ring) 83°. Unfortunately, di(tert-butyl)bis(trimethylsilyl)silane 17 prepared from di(tert-butyl)dichlorsilane 15 , chlorotrimethylsilane and lithium, does not react with alkyllithium compounds to give the analogous silanide. 相似文献
The surface properties and abhesion of both N/Si and U/Si series of random copolymers were studied by contact angle and peel strength measurements. When these copolymers are coated on clean glass slides, the contact angles of water on the polymer films are over 105° for copolymers with less than 50 mol % of Si , and 98-104° for those with more than 50 mol % of Si. All the polymers have similar critical surface energies, 21 dyn/cm (from hydrocarbon probes) and 20 dyn/cm (from EtOH/H2O probes), within the experimental error. This demonstrates that the amide groups in the polymer backbones are buried and all the polymers have methyl surfaces. The copolymers with less than 50 mol % Si (for N/Si copolymers) or 20 mol % (for U/Si copolymers) are stable and show good abhesive properties toward Scotch magic tape at or below 50°C. The peel strengths of Scotch magic tape with the copolymer coated slides rise dramatically as the annealing temperatures approach to the melting points of the polymers. 相似文献
The IR laser-induced degradations of liquid polydimethylsiloxane (PDMS) vapor and of hexamethyldisiloxane vapor have been studied in order to determine whether the high temperature thermal properties of the dimethylsiloxane unit is best represented by Si? O bond rearrangement (the conventional pyrolysis mechanism) or Si? C bond cleavage (the thermodynamic reaction pathway). The volatile products of these pulsed laser experiments with various viscosities of PDMS are methane, ethane, ethylene, and hydrogen. These results are consistent with Si? C bond cleavage to form methyl radicals, which can then recombine to form ethane or abstract a hydrogen atom from a matrix molecule to form methane. The presence of ethylene and hydrogen can be explained by the decomposition of hot ethane molecules. No evidence of Si? O bond cleavage was observed. Reaction temperatures are estimated with computer modeling using heat capacity data. 相似文献
Copolymers of 1,2,2,2-tetrachloroethyl esters of unsaturated acids and halogenated N-phenyl maleimides with styrene were pyrolyzed; volatile products were analyzed with a mass spectrometer combined with a gas chromatograph. Hydrogen halide and carbon dioxide in the volatile products were determined during the thermal decomposition of copolymers in glass ampoules; the acyl chloride groups were determined in the residues. The thermal decomposition of copolymers of tetrachloroethyl esters with styrene sets in at ca. 230° by the release of chloral from the copolymer and splitting of some of the CCl bonds in the copolymer. The decomposition of copolymers of styrene with halogenated N-phenyl maleimides starts above 300° by depolymerization of the polystyrene chain sections and by splitting of some of the carbon-halogen bonds. At 310 and 500° for copolymers of tetrachloroethyl esters and at 500° for halogenated N-phenyl maleimides, there is radical dehydrohalogenation of the copolymers, with depolymerization of polystyrene blocks and splitting of carbon-carbon bonds in the main chain. 相似文献
Trimethylsilyl Derivatives of Vb-Elements. V. Molecular and Crystal Structure of Lithium Bis(trimethylsilyl)arsenide · DME Lithium bis(trimethylsilyl)arsenide · DME 1 obtained from tris(trimethylsilyl)-arsine and n-butyl or methyl lithium in 1,2-dimethoxyethane crystallizes monoclinic with {a = 1813(3); b = 1327(3); c = 968(1) pm; β = 119.3(1)°; Z = 4} at +20°C. Experimental conditions unfavourable for an X-ray structure determination caused high standard deviations of all structural parameters. The refinements of these values calculated with respect to the centrosymmetric space group C2/m converged at a relatively high R-value of 0.090. In contrast to the homologous antimonide lithium bis(trimethylsilyl)arsenide · DME 1 is found to be dimeric in solution as well as in the solid state. The four-membered ring built up by bis(trimethylsilyl)arsino groups and DME-coordinated lithium atoms in alternating sequence is planar; the carbon atoms statistically occupy positions on both sides of a mirror plane. Characteristic bond lengths and angles are: As? Si 230.7(7); As? Li 259(2); Li? O 205(4) and 215(4) pm; Si? As? Si 103.2(4)°; Li? As? Li 81(1)°; As? Li? As 99(1)° and Li? As? Si 115(1)°. 相似文献
The electron diffraction data for methyltrimethoxysilane are consistent with a C3 symmetry model, the predominant forms of which have rotational angle(s) between 100 and 155° around the SiO bond (the anti conformation of the CSiOC chain would respond to 0°). There is probably large amplitude motion around the SiO bonds. The following bond lengths and bond angles were determined: ra(CH) 1.093 ± 0.005, ra(SiC) 1.842 ± 0.013, ra(SiO) 1.632 ± 0.004, ra(OC) 1.425 ± 0.004 », ∠CSiO 109.6 ± 0.5°. and ∠SiOC 123.6 ± 0.5°. 相似文献
The thermal stability and degradation process for a specific poly(aryl ether) system have been studied. In particular, the polymer which is available from Union Carbide Corporation as Bakelite polysulfone has been examined in detail. Polysulfone can be prepared from 2,2-bis(4-hydroxyphenyl)propane and 4,4′-dichlorodiphenyl sulfone by nucleophilic aromatic substitution. Because of a low-temperature transition at ? 100°C. and a glass transition at 195°C., polysulfone retains useful mechanical properties from ?100°C. to 175°C. A number of experimental methods were utilized to study the thermal decomposition process for this polymer system. Polysulfone gradually degraded in vacuum above 400°C. as demonstrated by mass spectrometry. Thermogravimetric analysis in argon, air, or high vacuum indicated that rapid decomposition began above 460°C. From gas chromatography, mass spectrometry and repeated laboratory pyrolyses, a number of products from polymer decompositions were identified. The most important degradation process in vacuum or inert atmosphere was loss of sulfur dioxide. Several model compounds representative of portions of poly(aryl ether) molecules were synthesized and the relative thermal stabilities determined. Possible mechanisms for pure thermal decomposition of polysulfone were derived from the product analyses, model studies, and consideration of bond dissociation energies. 相似文献
The simultaneous thermal studies (TG/DTG/DSC) coupled with the FTIR analysis of the gaseous decomposition products created under oxidative heating of starch-g-poly(neryl acrylate) and starch-g-poly(geranyl acrylate) copolymers have been presented. To these studies, the copolymers with the following grafting percents (G) were selected: starch-g-poly(neryl acrylate) copolymers: 36.6?±?0.3%, 40.3?±?0.4%, 42.8?±?0.4% and starch-g-poly(geranyl acrylate) copolymers: 28.9?±?0.2%, 32.4?±?0.6%, 35.6?±?0.4%. The performed tests proved that the thermal resistance of the copolymers was strongly dependent on their G values, despite a small difference in the G values between the samples. The slight increase (ca. 6.2–6.7%) in the G value caused the significant drop of the thermal stability of all the studied materials. The TG/DTG/DSC studies confirmed at least three-stage decomposition mechanism of the copolymers where simultaneous pyrolysis, oxidation, dehydration and decarboxylation processes took place. The TG/FTIR analyses showed the emission of various structure fragments; among them, one can mention the creation of some organic fragments such as aldehyde, acid, alkene, alkane, furan fragments, CH4 and inorganic species (CO2, CO, H2O) as a result of the oxidative decomposition processes of the studied copolymers. In addition, the conducted studies demonstrated similar decomposition course and mechanism for both types of the copolymers, regardless of the monomer type used to the graft process.
The title molecule is dimeric, i.e. di‐μ‐trimethylsiloxy‐bis(dichloroaluminium), [Al2Cl4(C3H9Si)2], and possesses exact crystallographic inversion symmetry. The O atoms of the trimethylsiloxy groups bridge the two Al atoms to form a four‐membered ring. The Si—O bond distance [1.711 (3) Å], the Al—O mean bond distance [1.806 (4) Å] and the mean Si—C bond distance [1.875 (6) Å] appear to agree well with standard data. Mean values for C—Si—C, O—Si—C, and Si—O—Al angles are 112.9 (3), 105.8 (2), and 131.8 (2)° repectively. The two ring angles O—Al—O and Al—O—Al are 84.43 (16) and 95.57 (16)°, respectively. 相似文献
Complexes with Aromatic Carboxylic Acids. V. On the Layer Structure of Cd[C6H4(COO)2] · H2O Single crystals of Cd[C6H4(COO)2] · H2O were grown in aqueous silica gel. According to differential thermal analysis the dehydration commences at 160°C, and decomposition to CdO occurs between 380 and 420°C. Cd2+ is surrounded by one water molecule and six oxygen atoms stemming from carboxylate groups (Cd? O: 225.4–247.0 pm). One carboxylate group chelates Cd2+. Two carboxylate oxygen atoms are bound to two Cd2+ each. The coordination polyhedra are interlinked by a common edge and two common corners. Further connection is established by the phthalate dianions. This leads to layers parallel (010). The COO? groups are titled differently against the plane of the C6 ring (40° and 71°). The C? O bond lengths reach from 125.9 to 128.3 pm, the C? C bonds of the C6 ring from 136.7 to 140.3 pm. 相似文献
Soluble copolymers containing both pendant cyclic iminoethers such as 4,4-dimethyl-2-oxazoline or 4,4,6-trimethyl-4H-dihydro-1,3-oxazine and carboxylic acid were successfully synthesized by radical copolymerizations of 4,4-dimethyl-2-vinyl-2-oxazoline, 4,4-dimethyl-2-isopropenyl-2-oxazoline, or 4,4,6-trimethyl-2-vinyl-4H-dihydro-1,3-oxazine with methacrylic acid and styrene, methyl methacrylate, or ethyl acrylate using AIBN as an initiator in benzene or DMF at 60 or 80°C. The crosslinking reaction of the copolymers obtained did not occur by heating at 70°C. However, these copolymers quantitatively produced gel products by heating at 130°C. The rate of crosslinking reaction of the copolymer increased with increasing pendant cyclic iminoether and carboxylic acid groups. The rate of crosslinking was also affected by the molecular motion of the polymer chain. Our results show that the copolymers of more sterically hindered 2-vinyl-2-oxazolines are more stable and so they can be crosslinked in a controlled manner and at higher temperatures than the previously studied polyoxaziline system. 相似文献