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1.
Sodium tetrazodiphenyl naphthionate and pyromellitic dianhydride were polycondensed under microwave irradiation and oil‐bath heating. The resultant poly(amic acid) was imidized in the solid phase by microwave irradiation and oil‐bath heating. The effects of the reaction temperature, the concentration of monomers, the monomer ratio, and the microwave irradiation time on the conversion, intrinsic viscosity, and third‐order nonlinear optical (NLO) coefficient of the polymer were investigated. The results showed that the polycondensates had high third‐order NLO coefficients (χ(3) = 1.476 × 10?12esu) and very fast time responses (15.79 ps). The χ(3) values of the polycondensates under microwave irradiation were higher than those of conventional thermopolymerization. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1121–1128, 2003  相似文献   

2.
A single‐pot atom‐transfer radical polymerization (ATRP) under microwave irradiation was first used to successfully synthesize polyacrylonitrile. This was achieved by using FeCl2/succinic acid as the catalyst and 2‐chloropropionitrile as the initiator. Using the same experimental conditions, the apparent rate constant under microwave irradiation was found to be higher than that under conventional heating. The FeCl2/succinic acid ratio of 1 : 2 not only gives the best control of molecular weight and its distribution but also provides rather rapid reaction rate. When FeCl2 was replaced with CuCl, ATRP of AN does not show an obvious living characteristics. To demonstrate the active nature of the polymer chain end, the polymers were used as macroinitiators to proceed the chain‐extension polymerization. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1598–1601, 2006  相似文献   

3.
Poly(D ,L ‐lactide) (PDLLA) was synthesized by microwave‐irradiated ring‐opening polymerization catalyzed by stannous octoate (Sn(Oct)2) under atmosphere. The effects of heating medium, monomer purity, catalyst concentration, microwave irradiation time, and vacuum level were discussed. Under the appropriate conditions such as carborundum (SiC) as heating‐medium, 0.15% catalyst, lactide with purity above 99.9%, 450 W microwave power, 30 min irradiation time, and atmosphere, PDLLA with a viscosity–average molecular weight (Mη) over 2.0 × 105 and a yield over 85% was obtained. The dismission of vacuum to ring‐opening polymerization of D ,L ‐lactide (DLLA) under microwave irradiation simplified the process greatly. The temperature under microwave irradiation and conventional heating was compared. The largely enhanced ring‐opening polymerization rate of DLLA under microwave irradiation was the coeffect of thermal effects and microwave effects. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2244–2247, 2006  相似文献   

4.
We performed the emulsion polymerization of styrene successfully with potassium persulfate (KPS) as an initiator and sodium dodecylsulfonate as an emulsifier under high‐power pulsed microwave irradiation (PMI). We investigated the effects of the temperature, the concentration of initiator, and various parameters of PMI (i.e., irradiation power, duty cycle, irradiation energy, and pulse width) on the polymerization. The results indicated that PMI, compared to conventional heating (CH), caused a significant increase in the decomposition rate of KPS (2.4 times higher than that under CH at about 70°C) and in the amount of particles (5 times higher than that under CH); consequently, the polymerization rate was effectively enhanced. For initiator concentrations of 0.10 and 0.20 wt %, the enhancement of the polymerization rate under PMI was 129 and 38% greater, respectively, than that under CH. The glass‐transition temperature and the regularity composition of the polymers under PMI and CH showed no difference, which indicated that PMI had little effect on the physical properties and microstructure of the polymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 28–35, 2003  相似文献   

5.
The well-dispersed silver nanoparticles were prepared in reactive methacrylate monomers under microwave irradiation without polymerization. In contrast to conventional heating, the synthesis of Ag nanoparticles proceeded uniformly throughout the reaction vessel only under microwave irradiation, reaching the completion of the reaction simultaneously in the whole reaction solution. Successive polymerization of the monomer containing the resulting nanoparticles has successfully produced a monohybrid of the silver nanoparticles dispersed in polymer matrix.  相似文献   

6.
Reverse atom transfer radical polymerization was first used to successfully synthesize polyacrylonitrile under microwave irradiation. FeCl3, coordinated by isophthalic acid, was used as the catalyst, and 2,2′‐azobisisoheptonitrilewas used as the initiator. N,N‐Dimethylformamide was used as the solvent to improve the solubility of the ligand. Under the same experimental conditions, the apparent rate constant under microwave irradiation was higher than that under conventional heating. The polymerization not only showed the best control of the molecular weight and its distribution but also provided a rather rapid reaction rate with the [acrylonitrile]/[2,2′‐azobisisoheptonitrile]/[FeCl3]/[isophthalic acid] ratio of 300 : 1 : 1 : 2. The polymers obtained were used as macroinitiators to initiate the chain extension and successfully synthesize acrylonitrile polymers with a molecular weight higher than 50,000 and a narrow polydispersity as low as 1.30. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

7.
The kinetics of polymerization of ?‐caprolactone (CL) in bulk was studied by irradiating with microwave of 350 W and frequency of 2.45 GHz with different cycle‐heating periods (30–50 s). The molecular weight distributions were determined as a function of reaction time by gel permeation chromatography. Because the temperature of the system continuously varied with reaction time, a model based on continuous distribution kinetics with time/temperature‐dependent rate coefficients was proposed. To quantify the effect of microwave on polymerization, experiments were conducted under thermal heating. The polymerization was also investigated with thermal and microwave heating in the presence of zinc catalyst. The activation energies determined from temperature‐dependent rate coefficients for pure thermal heating, thermally aided catalytic polymerization, and microwave‐aided catalytic polymerization were 24.3, 13.4, and 5.7 kcal/mol, respectively. This indicates that microwaves increase the polymerization rate by lowering the activation energy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1450–1456, 2004  相似文献   

8.
微波辐射快速合成乙二醇硬脂酸酯   总被引:4,自引:0,他引:4  
张永刚  郭祥峰  王清滨 《精细化工》2003,20(10):612-614
在微波辐射条件下,以对甲苯磺酸(PTSA)为催化剂,乙二醇和硬脂酸快速合成了乙二醇硬脂酸酯。讨论了微波功率、辐射时间、催化剂用量和醇酸量比对反应转化率的影响,得出最佳反应条件为:硬脂酸17 1g、乙二醇4 1g、PTSA0 23g、微波功率600W、反应时间5min,转化率为97%。该条件下的反应速率是常规加热条件下的36倍。实验中,采用煤油温度计测量了反应过程中的温度变化。  相似文献   

9.
The aim of this work is to study the use of an ionic liquid (IL) as surfactant in emulsion polymerization reactions and to evaluate its effect when these reactions are heated under microwave irradiation. The IL 1‐n‐dodecyl‐3‐methylimidazolium chloride was chosen to replace the surfactant dodecyltrimethylammonium bromide (DTAB) in methyl methacrylate emulsion polymerizations. The conversion evolutions and the final average diameter of polymeric particles were quite similar for reactions using the surfactant DTAB or the IL, showing that the IL acted efficiently as surfactant in emulsion polymerizations. Comparing the polymerization reactions performed under microwave irradiation and conventional heating, reaction rate enhancements were obtained for both DTAB and IL. Using a pulsed scheme, under high‐power microwave irradiation, slightly higher reaction rates and molecular weights were obtained in reactions using IL, in comparison with surfactant DTAB, indicating the existence of some specific effects linked to IL–microwaves interaction. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

10.
采用微波加热与催化剂相结合对植物纤维素进行降解。探讨在微波加热条件下降解条件对植物纤维素降解过程的影响,确定适宜的降解条件为催化剂浓度5%,反应温度100℃,反应时间3h,此时降解液中还原糖浓度为2.68g/L。在相同条件下,微波加热降解较常规加热还原糖浓度提高了33.5%。利用SEM分析微波加热和常规加热条件下降解剩余物的结构特征,结果表明,微波作用使纤维素的聚合度降低。红外分析结果表明,微波条件与常规条件下的剩余物结构一致。  相似文献   

11.
4‐(4′‐Aminophenyl)‐1,2,4‐triazolidine‐3,5‐dione ( 1 ) was reacted with 1,8‐naphthalic anhydride ( 2 ) in a mixture of acetic acid and pyridine (3 : 2) under refluxing temperature and gave 4‐(4′‐N‐1,8‐naphthalimidophenyl)‐1,2,4‐triazolidine‐3,5‐dione ( NIPTD ) ( 3 ) in high yield and purity. The compound NIPTD was reacted with excess n‐propylisocyanate in N,N‐dimethylacetamide solution and gave 1‐(n‐propylamidocarbonyl)‐4‐[4′‐(1,8‐naphthalimidophenyl)]‐1,2,4‐triazolidine‐3,5‐dione ( 4 ) and 1,2‐bis(n‐propylamidocarbonyl)‐4‐[4′‐(1,8‐naphthalimidophenyl)]‐1,2,4‐ triazolidine‐3,5‐dione ( 5 ) as model compounds. Solution polycondensation reactions of monomer 3 with hexamethylene diisocyanate ( HMDI ), isophorone diisocyanate ( IPDI ), and tolylene‐2,4‐diisocyanate ( TDI ) were performed under microwave irradiation and conventional solution polymerization techniques in different solvents and in the presence of different catalysts, which led to the formation of novel aliphatic‐aromatic polyureas. The polycondensation proceeded rapidly, compared with conventional solution polycondensation, and was almost completed within 8 min. These novel polyureas have inherent viscosities in a range of 0.06–0.20 dL g?1 in conc. H2SO4 or DMF at 25°C. Some structural characterization and physical properties of these novel polymers are reported. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2861–2869, 2003  相似文献   

12.
Microwave‐assisted ring‐opening polymerization (MROP) of trimethylene carbonate (TMC) was carried out with four different types of zinc lactate, as the catalyst. Poly(trimethylene carbonate)s (PTMC) with a number–average molar mass ranging from 2990 to 75,410 g/mol and a TMC conversion ranging from 85.2% to 98.2% were synthesized effectively in 30 min at 120°C under microwave irradiation. The effects of the catalyst type, catalyst concentration, and microwave irradiation time on the MROP of TMC were studied. The MROP of TMC was much faster than that under conventional heating conditions. Thermal analysis suggested that PTMC with higher molar mass exhibited higher glass transition temperature (Tg) and thermal stability. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

13.
α, ω-dihydroxyl polydimethylsiloxane (DHPDMS) was prepared via anionic ring-opening polymerization of octamethyl cyclotetrasiloxane (D4) under microwave irradiation (MI) in the presence of water. The conversion and polymerization rate were calculated by the gravimetric method. The effect of microwave power on the polymerization was investigated. FTIR was used to verify the DHPDMS prepared at different irradiation times. The results show that the conversion is the highest when the initial microwave power is preset at 700 W. Compared with conventional heating (CH), the polymerization rate and equilibrium conversion are both enhanced by the introduction of microwave irradiation. The species and concentration of the cyclosiloxane mixture caused by backbiting reaction were determined by gas chromatography/mass spectrometry (GC/MS). The lower concentration of cyclosiloxane in the polymer prepared under MI indicates that side reactions have been reduced and a pure polymer obtained. The molecular weight and polydispersity index (PDI) measured by GPC show that under MI, the molecular weight of DHPDMS is lower and PDI is narrower than those under CH.  相似文献   

14.
阳鹏飞  周继承  王宏礼 《应用化工》2014,(10):1820-1824,1829
在新型微波催化反应器上进行微波协同活性炭催化还原NO反应与常规加热条件下活性炭与NO还原反应的宏观动力。结果表明,在微波辐射条件下,该反应的活化能为20.754 5 kJ/mol。常规加热条件下为29.568 8 kJ/mol。这说明微波作用不仅具有热效应,而且大大降低了反应活化能,具有促进活性炭与NO还原反应的催化效应。  相似文献   

15.
The phase-transfer catalysts, long-chain quaternary ammonium salts, were rapidly synthesized from fatty alcohols by the reactions with hydrogen halides in the presence of trialkyl amines under microwave irradiation. The catalysts could be widely applied in a variety of quick and new organic reactions, whether by conventional heating or under microwave irradiation. The reaction efficiencies under microwave irradiation were higher than those obtained with conventional heating.  相似文献   

16.
微波辐射下合成庚酸乙酯   总被引:2,自引:0,他引:2  
马宏勋  董金龙 《应用化工》2010,39(3):417-419
以对甲苯磺酸(PTSA)为催化剂运用微波辐射技术合成庚酸乙酯。其适宜的工艺条件为:酸醇物质的量比为1∶2.0,辐射时间5 min,辐射功率240 W,催化剂用量为2%(质量分数),产率可达89.6%以上。该条件下的反应速率是常规加热条件的30倍。  相似文献   

17.
在微波辐射下,强酸性阳离子交换树脂为催化剂,一步酯化合成了8种空间位阻较高的L-氨基酸异丙酯和异丁酯,并用1HNMR和IR对其结构进行了表征。研究结果表明,微波辐射大大加速了酯化反应,所得8种酯的酯化收率均在50~70%之间。微波辐射反应所需时间大幅缩短,仅为常规加热时间的1/48~1/72,且反应物极性越大,反应时间缩短越明显。同时,就微波辐射功率、辐射时间及加热方式对酯化反应的影响进行了研究。  相似文献   

18.
Zhu MQ  Chen GC  Li YM  Fan JB  Zhu MF  Tang Z 《Nanoscale》2011,3(11):4608-4612
One-step facile synthesis of monoporous polymer microspheres via microwave-controlled dispersion polymerization is introduced. This template-free method employing the dispersion polymerization of styrene under microwave irradiation induces directly the formation of uniform monoporous polymer microspheres, with controllable morphologies and sizes, which can be tuned by simply adjusting parameters for the synthesis. A comparison to conventional heating indicates that microwave irradiation plays a vital role in the formation of this novel morphology.  相似文献   

19.
微波辐射对甲苯磺酸催化合成柠檬酸三丁酯   总被引:6,自引:0,他引:6  
在微波辐射下 ,以对甲苯磺酸作催化剂 ,柠檬酸和正丁醇直接酯化生成柠檬酸三丁酯。优惠反应条件为 :柠檬酸 5 0 g ,催化剂 0 3 g ,正丁醇 2 0ml,微波功率中高火 ,辐射时间 3 0min ,酯化收率为 91 2 %。该条件下的反应速度是常规加热法反应速度的 6倍。  相似文献   

20.
Palladium particles were generated by reduction of palladate anions bound to an ion exchange resin inside microreactors. The size and distribution of the palladium particles differed substantially depending on the degree of cross‐linking and the density of ion exchange sites on the polymer/glass composites, the latter parameter having a larger influence than the former. The polymer phase of the composite materials was used for the loading with clusters composed of palladium particles which are 1 to 10 nm in diameter. The reactivity and stability of six different palladium‐doped polymer/glass composite samples for transfer hydrogenations was investigated both under conventional and microwave heating in the batch mode as well as under continuous flow conditions using the cyclohexene‐promoted transfer hydrogenation of ethyl cinnamate as a model reaction. Regarding the heating method it was found that catalysts that are composed of larger metal particles perform better under microwave irradiating conditions whereas samples with smaller particle sizes perform better under conventional heating. Comparing batch experiments with flow‐through experiments the latter technique gives better conversion. Reusability was better in microwave heated experiments than in traditional heating.  相似文献   

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