超声辐照引发MMA微乳液聚合动力学研究

用自由基捕捉剂N,N-二苯基-2,4,6-三硝基苯肼基(DPPH)进行超声辐照引发甲基丙烯酸甲酯(MMA)微乳液聚合引发过程的动力学研究,结果表明,所得速率常数比超声辐照引发纯单体聚合的速率常数大一个数量级,说明超声辐照在微乳液聚合体系中的引发作用远远强于本体聚合;得到的表观活化能为正值,说明升温有利于超声辐照引发微乳液聚合.对聚合过程动力学的研究表明,引发剂用量决定聚合反应速率曲线恒速期的长短.     

Initiating free radical polymerization

The kinetics and mechanism of the initiation and reinitiation of free radical polymerization is reviewed. The importance of understanding the kinetics, specificity and efficiency of initiation and chain transfer when predicting polymerization kinetics and polymer composition is highlighted. These factors are particularly important when making low molecular weight polymers and in living or controlled polymerization processes. Examples of RAFT polymerization and catalytic chain transfer are provided.     

INVERSE EMULSION POLYMERIZATION OF ACRYLAMIDE: POLYMERIZATION KINETICS AND PROCESS DEVELOPMENT

Inverse emulsion polymerization confers the benefits of emulsion polymerization kinetics — rapid polymerization rates combined with high polymer molecular weights — on water-soluble polymers, particularly polyacrylamide and its copolymers and derivatives, and allows easy dissolution of the polymer in water by inversion of the latex. The mechanism and kinetics of the inverse emulsion polymerization of acrylamide in o-xylene containing Tetronic 1102 emulslfier and benzoyl peroxide initiator are described, particularly the formation of 10-200nm multiple emulsion droplets resulting from the particulate emulsifier, and their effect on the polymerization process     

Reversible addition-fragmentation chain transfer polymerization in microemulsion

This tutorial review first details the uncontrolled microemulsion polymerization mechanism, and the RAFT polymerization mechanism to provide the necessary background for examining the RAFT microemulsion polymerization mechanism. The effect of the chain transfer agent per micelle ratio and the chain transfer agent aqueous solubility on the RAFT microemulsion polymerization kinetics, polymer molecular weight and polydispersity, and polymer nanoparticle size are discussed with a focus on oil-in-water microemulsions. Modeling of RAFT microemulsion polymerization kinetics and the resulting final polymer molecular weight are presented to assist with the analysis of observed experimental trends. Lastly, the current significance of RAFT microemulsion polymerization and the future directions are discussed.     

偏氯乙烯悬浮聚合反应速率模型

通过实验研究了偏氯乙烯悬浮聚合反应动力学,比较了偏氯乙烯与氯乙烯聚合动力学行为的异同.在假定偏氯乙烯聚合反应发生在单体相和液固界面两个区域的基础上,提出了偏氯乙烯沉淀聚合反应速率模型.模型预测的转化率值几乎在全转化率范围内都与本文的偏氯乙烯悬浮聚合实验结果一致.     

KINETICS OF THE ZIEGLER-NATTA POLYMERIZATION OF 1-OCTENE(I)----THE KINETICS OF THE STATIONARY PERIOD

The kinetics of the Ziegler-Natta polymerization of C6~C20 α-defines has been seldom studied,which showed no apparent differences from the kinetics of the polymerization of ethylene and propylene.1-Octene polymerizes in alkanes in a solution state,differing from the slurry polymerization of ethylene.We have found and studied the inordinary kinetics of the polymerization of 1-octene on α-TiCl3-AlEt3[or-Al(i-Bu)3,-AlEt2Cl] catalysts in n-heptane,and have given a primary explanation to this phenomenon.     

环氧乙烷环氧丙烷开环聚合反应动力学研究

环氧乙烷和环氧丙烷由于具有较高的环张力,因而容易发生开环聚合。本文综述了环氧乙烷合环氧丙烷开环聚合反应的动力学研究进展,考察了环氧乙烷和环氧丙烷开环聚合反应的机理,分别讨论了各类催化剂体系中环氧乙烷和环氧丙烷开环聚合的动力学常数、两者的竞聚率及开环聚合产物的分子量分布,并指出了开环聚合反应动力学研究对于环氧乙烷和环氧丙烷的开环聚合研究及工业应用的重要性。     

Substituted Benzophenones as Photoinitiators

Substituted benzophenone photoinitiators were synthesized and characterized by spectroscopy methods. Their absorption spectra and kinetics of the polymerization were compared to benzophenone itself. The kinetics of the photopolymerization of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol triacrylate (TMPTA) was studied by measuring the polymerization heat evolution of sample, irradiated with a laser. The influence of photoinitiator concentration and light intensity on the polymerization was also studied.     

表面活性单体AMC14AB在水溶液中的聚合动力学研究

采用溴酸钾-溴化钾法研究了阳离子型表面活性单体(2-丙烯酰胺基)乙基十四烷基二甲基溴化铵(AMC14AB)在水溶液中的聚合动力学,分别考察了引发剂浓度与单体浓度对聚合速率的影响,确定了聚合速率方程,分析了聚合机理,考察了温度对聚合反应的影响,测定了聚合表观活化能。研究结果表明,由于AMC14AB在水溶液中的胶束化行为,使其具有较快的聚合速率,于60℃下聚合,40min内转化率即可达到80%以上;AMC14AB的聚合速率方程为Rp=k[M]0.92[I]0.48,说明链终止为双基终止方式,引发过程与单体无关;聚合表观活化能为80.72kJ/mol。     

Monitoring photopolymerization of trimethylolpropane triacrylate using a quartz crystal resonator

The UV photopolymerization of trimethylolpropane triacrylate with a photoinitiator of 2‐ethylanthraquinone is monitored using the variation of resonant resistance of a quartz crystal resonator to investigate the polymerization kinetics. The roles of initiator concentration and irradiation time are experimentally examined, and it is found that two different kinetics are involved in the photopolymerization. The initiator radicals produced by the UV light proceed the polymerization as long as the monomer remains even after the UV illumination has stopped. The experimental results indicate that the photopolymerization has the first‐order kinetics at the first‐ and the zeroth‐order kinetics followed. With the high concentration of initiator the polymerization occurs in the first‐order kinetics only, and so does with long irradiation time. The polymerization constants of the first and zeroth‐order kinetics are estimated from monitoring monomer amounts at different polymerization conditions. The photopolymerization is characterized with the FTIR spectroscopy. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

工业丙烯聚合过程的模型化研究进展

基于我国聚丙烯生产状况,指出我国在聚丙烯合成技术上的研究缺陷.针对国内缺陷并遵循"聚丙烯合成过程模型化"主线,本文从聚丙烯生产工艺、丙烯聚合机理、丙烯聚合动力学以及聚合反应器模型四方面对丙烯聚合过程模型化的近期研究进展进行综述,重点简述我国科研工作者在相关方面的研究进展.     

Molecular Versus Conventional Kinetics of Emulsion Polymerization

Summary: Experimental data are discussed challenging the deterministic kinetics of emulsion polymerization. Examples are given for the overall rate of polymerization, in-situ stabilizer formation, and swelling of latex particles. Improving the deterministic view on emulsion polymerization kinetics requires the consideration of results of molecular modelling and the application of multiscale integration techniques.     

Differential scanning calorimetric study on free-radical polymerization of <Emphasis Type="Italic">gem</Emphasis>-dinitroalkyl acrylates and methacrylate

2,2-dinitropropyl acrylate (DNPA), 2,2-dinitrobutyl acrylate (DNBA) and 2,2-dinitrobutyl methacrylate (DNBMA) were synthesized and the kinetics of their free-radical polymerization in the presence of 2,2′-azobisisobutyronitrile (AIBN) were investigated by DSC in the non-isothermal mode. The kinetics of the free-radical polymerization as estimated by the Kissinger and Ozawa methods showed that the reaction is disfavoured by increasing steric hindrance around the acrylyl double bond. The rate constants calculated from the activation parameters showed the structural dependency. The polymerization kinetics revealed that the polymerizability of three monomers decreased due to the presence of substituent methyl groups on the acrylyl double bond and 2,2-dinitrobutyl on ester group. Thus, the polymerization tendency increased in the order DNPA>DNBA>DNBMA.     

自由基聚合速率的深入讨论

自由基聚合是高分子化学课程中的重要一章,自由基聚合动力学(包括聚合速率、平均相对分子质量及分布)是教学中的重要内容。本文讨论了建立自由基聚合微观动力学模型的基础:三个基本假设和四个简化条件,阐释了传统单官能度引发剂引发的聚合体系速率方程推导中这些假设和条件的运用,并扩展到双官能度引发剂体系,得到基元反应速率和总速率。提出从三个层次讨论影响自由基聚合速率的因素,深化了对自由基聚合速率教和学。     

Synthesis of poly(methyl methacrylate) via ARGET ATRP and study of the effect of solvents and temperatures on its polymerization kinetics

This investigation reports the synthesis of poly(methyl methacrylate) via activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) and studies the effect of solvents and temperature on its polymerization kinetics. ARGET ATRP of methyl methacrylate (MMA) was carried out in different solvents and at different temperatures using CuBr₂ as catalyst in combination with N,N,N′,N″,N″‐pentamethyldiethylenetriamine as a ligand. Methyl 2‐chloro propionate was used as ATRP initiator and ascorbic acid was used as a reducing agent in the ARGET ATRP of MMA. The conversion was measured gravimetrically. The semilogarithmic plot of monomer conversion versus time was found to be linear, indicating that the polymerization follows first‐order kinetics. The linear polymerization kinetic plot also indicates the controlled nature of the polymerization. N,N‐Dimethylformamide (DMF), tetrahydrofuran (THF), toluene, and methyl ethyl ketone were used as solvents to study the effect on the polymerization kinetics. The effect of temperature on the kinetics of the polymerization was also studied at various temperatures. It has been observed that polymerization followed first‐order kinetics in every case. The rate of polymerization was found to be highest (k_app = 6.94 × 10⁻³ min⁻¹) at a fixed temperature when DMF was used as solvent. Activation energies for ARGET ATRP of MMA were also calculated using the Arrhenius equation.     

Investigation of the radical polymerization kinetics using DSC and mechanistic or isoconversional methods

In this research, an effort was undertaken to investigate radical polymerization kinetics using experimental data from DSC measurements and mechanistic or isoconversional models. Polymerization of a polar monomer, namely 2-hydroxyethyl methacrylate in the presence of benzoyl peroxide initiator was studied. The variation of the effective activation energy with conversion was directly interpreted in terms of the physical phenomena taking place during the reaction in a microscale. Both isothermal and non-isothermal DSC data were employed and the effect of diffusion-controlled phenomena on the reaction kinetics at different conversion regimes was assessed. Finally, the effect of the presence of nanofiller on polymerization kinetics and the activation energy values were estimated and correlated to physical phenomena taking place during polymerization.     

苯乙烯在顺1,4-聚丁二烯上的接枝共聚反应动力学的Monte Carlo模拟

用ＭｏｎｔｅＣａｒｌｏ模拟方法对苯乙烯在顺１，４－聚丁二烯上的接枝反应动力学进行了研究。模拟结果表明，对于不同的橡胶浓度，接枝的和均聚的聚苯乙烯的数均聚合度、接枝效率与苯乙烯在顺１，４－聚丁二烯上的接枝共聚反应的动力学的解析解十分吻合，证明本方法能够有效地应用于自由基型接枝共聚合反应体系。     

Microemulsion polymerization of styrene

Initiation of polymerization in styrene oil-in-water microemulsions by water-soluble potassium persulfate of oil-soluble 2,2′-azobis-(2-methyl butyronitrile) at 70°C gave stable latexes which were bluish and less translucent than the original microemulsions. The effects of initiator concentration, polymerization temperature, and monomer concentration on the kinetics, particle size distributions, and molecular weight distributions were investigated. The kinetics of polymerization were measured by dilatometry. In all cases, the polymerization rate shows only two intervals, which increased to a maximum and then decreased. There was no apparent constant rate period and no gel effect. A longer nucleation period was found for polymerizations initiated by potassium persulfate as compared to 2,2′-azobis-(2-methyl butyronitrile). The small latex particle size (20–30 nm) and high polymer molecular weight (1–2 × 10⁶) implies that each latex particle consists of two or three polystyrene molecules. The maximum polymerization rate and number of particles varied with the 0.47 and 0.40 powers of potassium persulfate concentration, and the 0.39 and 0.38 powers of 2,2′-azobis-(2-methyl butyronitrile) concentration, respectively. This is consistent with the 0.4 power predicted by Smith–Ewart Case 2 kinetics. Microemulsion polymerizations of styrene–toluene mixtures at the same oil-water phase ratio gave lower polymerization rates and lower molecular weights, but the same latex particle size as with styrene alone. A mechanism is proposed, which comprised initiation and polymerization in the microemulsion droplets, by comparing the kinetics of microemulsion polymerization with conventional emulsion and miniemulsion polymerization systems.     

Photopolymerization kinetics in and of self‐assembling lyotropic liquid crystal templates

Photopolymerization in and of lyotropic liquid crystal (LLC) template phases shows great promise for generating nanostructure in organic polymers. Interestingly, the order imposed on the polymerization system in LLCs significantly alters polymerization kinetics. The rate of polymerization of hydrophilic monomers increases with increasing LLC order, primarily due to monomer/polymer association with surfactant and the resulting decrease of growing polymer chain diffusion. Conversely, as LLC order increases, hydrophobic monomers become less segregated as nonpolar volume increases, which decreases polymerization rate. The efficiency of initiators is also dependent on LLC template order, further contributing to polymerization rate changes. When reactive surfactants are used, LLC mesophase, location of reactive group, and aliphatic tail length also affect polymerization kinetics. Overall, these photopolymerization kinetics directly relate to the segregation behavior and local order of reactive groups and thus can be used to probe nanostructure evolution, facilitating understanding and control of ultimate polymer nanostructure. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 471–489     

Kinetics of dispersion polymerization of soluble monomers. I. Methyl methacrylate

The kinetics of the free-radical-initiated polymerization of methyl methacrylate in n-dodecane to produce dispersions of polymer stabilized with a steric barrier of soluble polymer chains have been determined by thermal analysis. The mode of the polymerization can be described in terms of a bulk polymerization within the monomerswollen polymer particles. A theoretical expression has been derived on the basis of a reaction scheme in which all the radicals produced in the diluent phase are transferred immediately to the polymer particles, monomer swells the polymer particles in partition equilibrium with monomer in the diluent, and polymerization proceeds within the polymer particle according to the kinetics of bulk polymerization, taking into account Trommsdorff acceleration and plasticization effects.