首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
The monomer reactivity ratios for the copolymerization of triphenyltin methacrylate with methyl acrylate, ethyl acrylate, and butyl acrylate have been found to be r1 = 2.58, r2 = 0.66, r1 = 2.37, r2 = 0.43, and r1 = 1.27, r0.39 = 0.39, respectively. also, the copolymerization parameters of triphenyltin methacrylate with methyl methacrylate and butyl methacrylate were as follows: r1 = 0.94, r2 = 0.99, and r1 = 0.68, r2 = 0.83, respectively. Copolymerization reactions were carried out in solution at 70°C using 1 mol % AIBN, and the copolymer compositions were determined by tin analysis. The sequence distribution of the alternating diad fractions for the systems studied were calculated at various feed compositions. The structure of the triphenyltin methacrylate monomer as well as its azeotropic copolymer with butyl methacrylate were investigated by IR spectroscopy.  相似文献   

2.
Summary Copolymerization of N-(2-hydroxyethyl) carbazolyl mathacrylate (M1) with 2,4-dinitrophenyl methacrylate (M2) takes place through the simple terminal mechanism having the parameters r1=0.35 and r2=0.53. Intramolecular charge transfer complexes with different donor/acceptor ratios are obtained. The intramolecular complexation is correlated with the alternating diad fraction and with the copolymer conformation through the 1H-NMR spectra registration temperature.  相似文献   

3.
The radical copolymerization of tetrafluoroethylene (TFE) and trifluorovinyl ω‐hydroxy comonomers [F2CCF(CH2)mOH with m = 1 (FA1) and m = 3 (FA3)] for the synthesis of fluorinated polymers bearing hydroxy side groups is presented. FA1 was prepared by dehydrofluorination of 2,2,3,3‐tetrafluoropropanol, whereas FA3 was obtained in a three‐step scheme starting from the radical addition of 1,2‐dichloroiodotrifluoroethane to allyl alcohol. The copolymerization conditions (in bulk or in solution in di n‐butyl ether) and the polymer compositions considerably influenced the molecular weights, the molecular weight distributions, and the thermal properties of these copolymers. The kinetics of copolymerization of both couples enabled to determine the reaction order to the initiator (being 0.9) and the close values of apparent activation energies for [TFE/FA1 (Ea = 52.4 kJ · mol−1) and for TFE/FA3 (Ea = 46.8 kJ · mol−1)] couples. From the Tidwell and Mortimer method, the relative reactivity ratios were calculated by elemental analysis or by 19F‐NMR spectroscopy, showing a higher reactivity of the TFE to incorporate the copolymer (rTFE = 2.47 and rFA1 = 0.41; rTFE = 1.57 and rFA3 = 0.45). The high values of the reaction order to the initiator and low molecular weights of copolymers were associated to the allylic chain transfer of the hydroxy comonomers and a mechanism of copolymerization was proposed. The comonomer diad and triad distribution was determined by the statistic theory and allowed one to calculate the average length of the comonomer sequences. Finally, the thermal decomposition of these cooligomers showed that those containing FA3 units are more thermostable than those synthesized from FA1, and that the higher the fluorinated alcohol content, the faster the thermal decomposition. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 189–202, 1999  相似文献   

4.
Anionic copolymerizations of styrene (M1) with excess 1-(4-dimethyl-aminophenyl)-1-phenylethylene (M2) were conducted in benzene at 25°C for 24h, using sec-butyllithium as initiator. Narrow molecular weight distribution copolymers with M?;n = 16.1 × 103 g/mol (M?w/M?n = 1.04) and 38.2 × 103g/mol (M?w/M?n = 1.05), and 24 and 38 moles of M2 per macromolecule, respectively, were characterized by size exclusion chromatography, 1H NMR spectroscopy and DSC. The monomer reactivity ratio, r1 = 5.6, was obtained from the copolymer composition at complete consumption of M1, assuming that the rate constant k22 =0,i.e. r2 =0. The polymers exhibited Tg values of 128 and 119°C, respectively, which correspond to an estimated Tg = 217°C for the hypothetical homopolymer of M2.  相似文献   

5.
Acrylonitrile–styrene–methyl methacrylate (A–S–M) terpolymers were prepared by photopolymerization using uranyl nitrate ions as photo initiators, which were analyzed by NMR spectroscopy. The terpolymer compositions were determined by Goldfinger's equation using comonomer reactivity ratios: ras = 0.04; rsa = 0.31; ram = 0.17, rma = 1.45; rsm = 0.52; rms = 0.47. The terpolymer compositions were also determined from the quantitative 13C(1H)‐NMR spectroscopy. The sequence distribution of the acrylonitrile‐, styrene‐, and methyl methacrylate–centered triads were determined from the 13C(1H)‐NMR spectra of the terpolymers and are in good agreement with triad concentrations calculated from the statistical model. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3026–3032, 1999  相似文献   

6.
A controlled/living photopolymerization of styrene (St) and acrylic acid (AA) mediated by FeCl3·6H2O/tetramethylethylenediamine (TMEDA) was performed in N,N-dimethylformamide using 4-bromomethylbenzophenon (4-BMBP) as photoinitiator at room temperature under UV irradiation. 4-BMBP was first used as ATRP initiator and photoinitiator. A well-defined poly(styrene-co-acrylic acid) with predetermined molecular weight and narrow molecular weight distribution was obtained. The kinetic rule of controlled free radical photopolymerization of St and AA was studied. The kinetic results showed that the obtained random poly(St-co-AA) copolymers produced narrow polydispersity (PDI) within the range of 1.25–1.32 when the conversion was beyond 16.5 %, which was characterized by GPC. The plots of number average molecular weight versus conversion and ln([M]0/[M]) versus time were linear, indicating a controlled/living photopolymerization process. The system proceeded under mild and environmentally friendly conditions. The effects of initiator, catalyst, ligand, and vitamin C(VC) concentrations on polymerization process were investigated. The copolymers were characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H NMR). The methods of Mayo-Lewis (ML), Kelen-Tudos (KT), and Yzrielev-Brokhina Roskin (YBR) were used to calculate the monomer reactivity ratios of controlled/living photopolymerization of St and AA at low conversions under selected conditions. The monomer reactivity ratios of St and AA were calculated to be r St = 0.82 and r AA = 0.30, respectively in this system. The living characteristics were demonstrated by chain extension experiment.  相似文献   

7.
The operation of the SDERF-cell in the study of the electron transfer kinetics of the Fe(CN)4?6/Fe(CN)3?6-system in 1 M KCl and 1 M KNO3-solutions at a stationary Pt-disk electrode is reported. The experimental current—overpotential curves are recorded by linear sweep voltammetry and analysed by two different methods using the theoretical relationship derived for a stationary disk electrode placed in a free rotating fluid. Both methods give the same value for the experimental rate constant k*. The effects of the temperature (0° to 40°C) and of the ratio of the rotor radius (rr) to the electrode radius (re)(rr/re = 0.50 to 0.81) have been studied. The activation energy for the redox process in 1 M KCl and 1 M KNO3 are: Ea = 3.4 ± 0.6 kcal/mol and Ea = 3.7 ± 0.7 kcal/mol respectively, while the k*-values at 25°C are: k* = (5.67 ± 0.41) × 10?3 cm.s?1 and k* = (4.53 ± 0.29) × 10?3 cm.s?1 respectively. The difference from the standard rate constant k0 ? 0.100 cm.s?1 is explained by the effect of the cell-geometry characterized by the G-factor, so that k° = Gk*, where G ? 19 for our cell.  相似文献   

8.
PVC, which was polymerized at atmospheric pressure (so called U-PVC) contains relatively high concentrations of defects contrary to normal PVC. The number of chain scissions in U-PVC determined by ozonolytic cleavage resulted in values between 0.026 and 0.058 per 100 monomer units (100 VC). The determination of allylic and tertiary chlorine was done by selective reaction of U-PVC with phenol and NMR-spectroscopic investigations of the phenolized polymers. The average ‘labile chlorine’ content amounts to 0.65/100 VC. Hydroxyl radicals formed during the decomposition of the initiator (K2S2O8) resulted in alcoholic endgroups in U-PVC, which were detectable in the IR-spectrum at 3580 cm?1. The termination with hydroxyradicals also led to structures at the chain ends changing into ß-chloraldehyde groups accompanied by HCl-elimination. The corresponding signal in the IR-spectrum appeared at 1720 cm?1. U-PVC raw material contained about two branch points per 100 VC. The CCl4 extracts of the same polymers revealed the ten-fold content of branching. The olefinic structures ? CH?CH? CHCl? and ? CHCl? CH?CH2 were determined by NMR-spectroscopy. The concentrations of each ranged from 0.25 to 0.3/100 VC. A typical double bond for U-PVC at the chain ends represented the structure ? CH?CH? CH2Cl, which was preferably present in the low molecular weight material.  相似文献   

9.
The microstructure of trans‐4‐methacryloyloxyazobenzene–methyl methacrylate copolymers prepared by solution polymerization process using AIBN as initiator is analyzed by one‐and two‐dimensional spectroscopy. Sequence distribution was calculated from the 13C(1H)‐NMR spectra of the copolymers. Comonomer reactivity ratios were determined using the Kelen–Tudos and the nonlinear error‐in‐variables methods are rA = 1.14 ± 0.08 and rM = 0.51 ± 0.03; rA = 1.13 ± 0.1 and rM = 0.50 ± 0.04, respectively. The sequence distribution of A‐ and M‐centered triads determined from 13C(1H)‐NMR spectra of copolymer is in good agreement with triad concentration calculated from a statistical model. The 2‐D heteronuclear single‐quantum correlation and correlated spectroscopy (TOCSY) was used to analyze the complex 1H‐NMR spectrum. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3016–3025, 1999  相似文献   

10.
Copolymers of 1‐vinyl‐1,2,4‐triazole (VTAz) and acrylic acid (AA) having different mole ratios were synthesized using free radical‐initiated solution polymerization in dimethylformamide at 70 °C with α,α′‐azobisisobutyronitrile as initiator in nitrogen atmosphere. The compositions of the synthesized copolymers for a wide range of monomer feeds were determined using Fourier transform infrared (FTIR) spectroscopy through recorded absorption bands for VTAz (1510 cm?1, C?N (triazole ring) stretching mode) and AA (1710 cm?1, C?O stretching mode) units. The structures of the copolymers were characterized using FTIR and 1H NMR spectroscopy. The copolymer compositions were also determined from 1H NMR analysis following proton signals of carboxyl group at 11.8–12.5 ppm of AA and of triazole ring at 7.5–8.1 ppm of VTAz. Monomer reactivity ratios for the VTAz‐AA pair were estimated using linear methods, i.e. Fineman–Ross (FR) and Kelen–Tüdös (KT). From FTIR evaluation, monomer reactivity ratios were calculated as r1 = 0.404 and r2 = 1.496 using the FR method and r1 = 0.418 and r2 = 1.559 using the KT method. These values were found to be very close to those obtained from NMR evaluation. The two cases r1r2 < 1 and r1 < r2 indicated the random distribution of the monomers in the final copolymers and the presence of a greater amount of AA units in the copolymer than in the feed, respectively. The observed relatively high activity of complexed growing radical‐AA? … VTAz was explained by the effect of complex formation between carbonyl groups and triazole fragments in chain growth reactions. Thermal behaviours of copolymers with various compositions were investigated using thermogravimetric and differential scanning calorimetric analyses. It was observed that thermal stabilities and glass transition temperatures of the copolymers increased resulting from complex formation between acid and triazole units. © 2012 Society of Chemical Industry  相似文献   

11.
The copolymerization of butadiene (Bd) and isoprene (Ip) with a supported titanium‐triisobutyl aluminum catalyst system was studied. An analysis using differential scanning calorimetry, X‐ray diffraction, and 13C‐NMR spectra indicated that products with 25–60 mol % Bd units were random copolymers and that the melting temperatures and glass‐transition temperatures (Tg) were 30–40 and ?74°C (or thereabout), respectively, which were very similar to those of natural rubber. The chemical structure of these copolymers was characterized by a high‐trans 1,4‐configuration: the trans 1,4‐content of Ip units was greater than 98%, and the trans 1,4‐content of Bd units was greater than 90%. The reactivity ratio of Bd was greater than that of Ip (rBd = 5.7 and rIp = 0.17). The sequence distribution of the monomer units of the copolymers followed a first‐order Markov statistical model. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1800–1807, 2003  相似文献   

12.
Acrylonitrile‐styrene‐glycidyl methacrylate (N/S/G) terpolymers were prepared by bulk polymerization by using benzoyl peroxide as initiator and analyzed by NMR spectroscopy. The compositions of terpolymers were determined by quantitative 13C{1H}‐NMR spectra and compared with those calculated by Goldfinger's equation by using comonomer reactivity ratios: rNS = 0.04, rSN = 0.40; rNG = 0.22, rGN = 1.37; rSG = 0.44, rGS = 0.53. The 13C{1H}‐ and 1H‐NMR spectra were overlapping and complex. The spectral assignments were done with the help of distortionless enhancement by polarization transfer and two‐dimensional 13C‐1H heteronuclear single quantum correlation experiments. 2D total correlated spectroscopy was used to ascertain the various coupling between the protons. The methyl, methine, methylene, and oxymethylene carbon resonances showed compositional sensitivity. 2D nuclear Overhauser enhancement spectroscopy (NOESY) experiment was used to ascertain the spatial proton–proton couplings. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1779–1790, 2003  相似文献   

13.
After comparison of three catalyst systems, i.e. [Nd(Oct)3/Al2Cl3ET3/Al(i-But)3, Ni(Oct)2/BF3OEt2/AlEt3 and Al(i-But)3/I2/TiCl4] the titanium catalyst system was used for the copolymerization of 1,3-butadiene with propylene oxide. The effects of monomer ratio on copolymer composition, conversion, microstructure, molar mass and molar mass distribution as well as of time of polymerization and of the aluminium/titanium ratio were evaluted. The copolymerization parameters were determined according to Kelen-Tüd?s as rbutadiene = 0,9 and rpropylene oxide = 3,9. Copolymerization was confirmed by 13C NMR spectroscopy and extract evaluation combined with 1H NMR spectroscopy.  相似文献   

14.
Two novel low-εr microwave dielectric ceramics AGa4O7 (A = Ca, Sr; called CGO and SGO, respectively) were analyzed by XRD, SEM, and Raman spectroscopy, showed the monoclinic structure with a C2/c space group. Encouraging microwave dielectric properties (CGO: εr = 9.1, Q × f = 40 600 GHz (f = 12.4 GHz), and τf = ?86.3 ppm °C?1; SGO: εr = 9.2, Q × f = 62 400 GHz (f = 14.6 GHz), and τf = ?63.4 ppm °C?1) are obtained. The PVL chemical bond theory indicated that GaO bonds play a role in affecting the εr and Q × f values. The τf of AGa4O7 (A = Ca, Sr) had adjusted close to zero (0.93CGO-0.07CaTiO3:εr = 11.3, Q × f = 31,043 GHz, and τf = 3.97 ppm °C?1; 0.82SGO-0.18LiCa2Mg2V3O12:εr = 11.8, Q × f = 55,564 GHz, and τf = 5.62 ppm °C?1).  相似文献   

15.
Copolymers of N‐vinyl‐2‐pyrrolidone (V) and glycidyl methacrylate (G) monomers of different compositions were prepared by free‐radical solution polymerization. The copolymer composition of these copolymers was determined with 1H‐NMR spectra. The reactivity ratios calculated from the Kelen–Tudos and nonlinear least‐square error‐in‐variable methods were rV = 0.03 ± 0.01 and rG = 5.05 ± 0.84 and rV = 0.02 and rG = 4.72, respectively. The triad sequence distribution in terms of V and G centered triads was determined from 13C{1H}‐NMR spectroscopy. The complete spectral assignment of 13C{1H}‐ and 1H‐NMR spectra was performed with the help of distortionless enhancement by polarization transfer and two‐dimensional 13C–1H heteronuclear single quantum coherence. The 1H–1H couplings were explained with total correlation spectroscopy and nuclear Overhauser enhancement spectroscopy spectra. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 50–60, 2002; DOI 10.1002/app.10186  相似文献   

16.
A waterborne‐polyurethane‐based fluorescent dye 4‐amino‐N‐cyclohexyl‐1,8‐naphthalimide (WPU‐ACN) was synthesized by attaching 4‐amino‐N‐cyclohexyl‐1,8‐naphthalimide (ACN) into polyurethane chains according to a prepolymer?ionomer process. The structure of WPU‐ACN was confirmed by means of Fourier transform infrared spectroscopy and UV?visible absorption. The number‐average molecular weight, glass transition temperature and average emulsion particle size for WPU‐ACN were determined as 7.8 × 105 g mol?1, 60 °C and 60 nm, respectively. The improved thermal stability of WPU‐ACN could be attributed to the incorporation of naphthalimide units in the preformed urethane groups. The fluorescence intensity of WPU‐ACN was dramatically enhanced compared with that of ACN. It was found that the fluorescence intensity of WPU‐ACN increased with increasing temperature, and the fluorescence spectra of WPU‐ACN showed a positive solvatochromic effect. In addition, the fluorescence of WPU‐ACN emulsion was very stable not only for long‐term storage but also for fluorescence quenching. © 2013 Society of Chemical Industry  相似文献   

17.
Copolymerization reactions of di-(tri-n-butyltin) itaconate with styrene and methyl methacrylate were carried out in solution at 70°C using 1 mol% azobisisobutyronitrile as a free radical initiator. The copolymer compositions were determined by chemical analysis as well as from 1H-NMR data. The monomer reactivity ratios for copolymerizations of di-(tri-n-butyltin) itaconate with styrene and methyl methacrylate have been found to be r1 = 0.228, r2 = 0.677, and r1 = 0.220, r2 = 1.635, respectively. The sequence distribution of the triad fractions were calculated from reactivity ratios and compared with those obtained from 1H-NMR data.  相似文献   

18.
Standard Gibbs energies of transfer, ΔG°t of alkali metal chlorides (M = Li, Na, K, Rb and Cs) and potassium bromide and iodide from water to the aqueous mixtures of 20, 40, 60 and 80 mass per cents of acetonitrile (ACN) have been determined at 25°C from emf measurements performed on the double cell comprising AgAg X and M (Hg) electrodes. The individual ionic contributions to ΔG°t have also been evaluated using the reference electrolyte (RE = Ph4AsBPh4) method, the required ΔG°t's of the RE being obtained from the measured solubilities of salts viz. Ph4AsPic, KBPh4 and KPic (Pic = picrate and Ph = phenyl). The observed increasing ΔG°t values of the halide ions X? and their order Cl? ? Br? ? I? furnish the thermodynamic evvidence for the effect of the well known decreased H-bonding and the anion destabilizing propensities of dipolar aprotic cosolvent ACN. But the observed shallow minima in ΔG°t-composition profiles for M+ and H+ are indicative of the result of the oppositg effects of water structure breaking propensities and the protophobic character of ACN and their relative order is the combined effects of acid—base, Born-type and soft—soft interactions. Moreover, while the distinctly pronounced stabilization of large tetraphenyl ionshas been ascribed as the combined effects of dispersion and cavity-forming interactions, the less pronounced solvation of Pic? has been attributed to the combined effects of increased dispersion interactions of benzene nucleus and of decreased H-bonding interactions of O-atoms of the substituents. These contentions have been further substantiated by comparing ΔG°t(i) values of some selected ions in ethylene glycol—water mixtures.  相似文献   

19.
The effects of addition of acetonitrile (ACN) on electrodeposition of nickel were investigated in a hydrophobic room-temperature ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) containing Ni(TFSA)2. Addition of ACN resulted in the change of the color of the ionic liquid. The UV-vis and FT-IR spectra of the electrolyte showed the coordination environment of Ni(II) changed gradually from [Ni(TFSA)3] to [Ni(ACN)6]2+ with an increase in the concentration of ACN. The diffusion coefficient of Ni(II) in BMPTFSA was increased and the reduction potential of Ni(II) shifted to the more positive side in the presence of ACN. The nucleation/growth process of Ni was not affected by the change in the coordination environment of Ni(II) from the chronoamperometric results although the more nuclei formed on the electrode surface. SEM showed smoother deposit was obtained in Ni(TFSA)2/BMPTFSA with ACN.  相似文献   

20.
Nanoarchitectonics of nanoporous carbon materials (NCMs) derived from natural resource; Areca Catechu Nut (ACN) with enhanced electrochemical supercapacitance properties is reported. ACN powder is chemically activated in a tubular furnace at 400?°C and the effect of activating agent sodium hydroxide (NaOH), zinc chloride (ZnCl2) and phosphoric acid (H3PO4) on the textural properties, surface functional groups and electrochemical supercapacitance properties was thoroughly examined. We found that ACN derived NCMs are amorphous in nature comprising of macropores, micropores and hierarchical micro- and mesopore architecture depending on the activating agent. Surface area and pore volume are found in the range 25–1985 m2 g?1 and 0.12–3.42 cm3 g?1, respectively giving the best textural properties for H3PO4 activated NCM. Nevertheless, despite the different chemical activating agent used, all the prepared NCMs showed similar oxygen-containing surface functional groups (carboxyl, carboxylate, carbonyl and phenolic groups). The H3PO4 activated NCM showed excellent supercapacitance properties giving a high specific capacitance of ca. 342 F g?1 at a scan rate of 5 mV s?1 together with the high cyclic stability sustaining capacitance retention of about 97% after 5000 charging/discharging cycles. Electrochemical supercapacitance properties have demonstrated that the ACN derived novel nanoporous carbon material would be a potential material in energy storage application.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号