Kinetics and Mechanism of the Polymerization of Methyl Methacrylate in a Y(acac)_3/n-BuMgCl System

Based on the kinetics equation proposed by T. Kagiya, the kinetic study on the polymerization of methyl methacrylate(MMA) by Y(acac)_3/n-BuMgCl was carried out with a dilatometer. It was found that the rate of propagation is the first order with respect to the concentration of both active center and monomer. Thus, the equation of propagation rate can be described as R_p=K_p[c][M]. In addition, the instantaneous chain initiation and single molecular termination were concluded for the present system. The activation energy is close to 32 kJ/mol. In the polymerization, n-BuMgCl acts not only as the cocatalyst, but also as chain transfer agent with c_I=3. 6 × 10^(-4).

KINETICS OF POLYMERIZATION OF METHYL METHACRYLATE INITIATED BY COPPER POLYPROPYLENE-BASED POLYAMIDOXIME-SODIUM SULFITE SYSTEM~*

The aqueous polymerization of methyl methacrylate initiated by copper polypropylene-based polyamidoxime (PPAO-Cu) -sodium sulfite system was investigated. The overall rate of polymerization (R_p) isR_p=9.7 x 10^(12) e^(-21.200/RT) [MMA]^(O.88)[Na_2 SO_3]^(0.50) The length of the induction period (τ) is inversely proportional to the concentration of sodium sultite and independent of the amount of polymer supported copper and the concentration of monomer. It could be expressed as follows:1/τ =1.2x10^(12)e^(-15.600/RT)[Na_2SO_3]=K_τR_iThe polymerization is initiated by a primary radical generated from the redox reaction rather than induced by 'coordination-proton transfer' mechanism.

Kinetic Modeling of the Photocatalytic Degradation of Methyl Orange by Supported TiO2

The photocatalytic degradation of methyl orange （MO） in UV/Supported-TiO2 system was investigated and a kinetic model was presented. The experimental results show that the photocatalytic degradation rate is favored by high concentration of dye in solution and is enhanced by the solution temperature. A simple kinetic model has been proposed which can describe the discoloration process in an adequate way. The calculated results obtained were in good agreement with experimental data. The model predicts the concentration of MO during the photocatalytic degradation process.

Nonlinear Multiple Model Predictive Control of Solution Polymerization of Methyl Methacrylate

A sequential linearized model based predictive controller is designed using the DMC algorithm to control the temperature of a batch MMA polymerization process. Using the mechanistic model of the polymerization, a parametric transfer function is derived to relate the reactor temperature to the power of the heaters. Then, a multiple model predictive control approach is taken in to track a desired temperature trajectory.The coefficients of the multiple transfer functions are calculated along the selected temperature trajectory by sequential linearization and the model is validated experimentally. The controller performance is studied on a small scale batch reactor.

Kinetics of Atom Transfer Radical Polymerization of Methyl Methacrylate Initiated by Cellulose Chloroacetate in BMIMCI

The kinetics of atom transfer radical polymerization（ATRP） of methyl methacrylate（MMA） initiated by cellulose based macroinitator, cellulose chloroacetate, performed in ionic liquid（1-N-butyl-3-methylimidazolium chloride, BMIMC1）, dimethyl sulfoxide（DMSO） and dimethyl formamide（DMF） were respectively studied in detail. The polymerizations were carried out under homogeneous conditions with CuBr as catalyst and 2,2＇-bipyridine（bpy） as ligand. The dependences of the rate of polymerization on solvent, temperature, monomer/initiator ratio and catalyst/ligand ratio were presented. Plots of ln（[M]0/[M]t） vs. time and molecular weight vs. conversion showed a linear dependence, indicating a constant number of propagating species throughout the polymerization as well as a negligible contribution of termination or transfer reactions. On the basis of an Arrhenius plot, the apparent energy of activation（AEaapp ） for ATRP of MMA in BMIMC1 was 16.6 kJ/mol which is much lower than that in diphenyl ether.

Kinetic Study of Atom Transfer Radical Polymerization of 2-(N,N-Dimethylamino)ethyl Methacrylate

A kinetic model was developed to describe the atom transfer radical polymerization (ATRP) of 2(N,N-dimethylarnino) ethyl methacrylate (DMAEMA). The model was based on a polymerization mechanism, which included the atom transfer equilibrium for primary radical, the propagation of growing polymer radical, and the atom transfer equilibrium for the growing polymer radical. An experiment was carried out to measure the conversion of monomer, the number-average molecular weight of polymer and molecular weight distribution for the ATRP process of DMAEMA. The experimental data were used to correlate the kinetic model and rate constants were obtained. The rate constants of activation and deactivation in the atom transfer equilibrium for primary radical are 1.0 x 10(4) L(.)mol(-1.)s(-1) and 0.04 L(.)mol(-1.)s(-1), respectively. The rate constant of the propagation of growing polymer radical is 8.50 L(.)mol(-1.)s(-1), and the rate constants of activation and deactivation in the atom transfer equilibrium for growing polymer radical are 0.045 L(.)mol(-1.)s(-1) and 1.2 x 10(5) L(.)mol(-1.)s(-1), respectively. The values of the rate constants represent the features of the ATRP process. The kinetic model was used to calculate the ATRP process of DMAEMA. The results show that the calculations agree well with the measurements.

Studies on the Mechanism of Methyl Methacrylate Polymerization Initiated by Volatile and Nonvolatile Products of Methyl Methacrylate Plasma

he volatile (VPP) and nonvolatile (NVPP) products of methyl methacrylate(MMA) reaction in plasma chamber were used as initiators of MMA polymeriza-tion. From the structure analyses of the two initiators, the measurement of poly-merization kinetics, and the determination of the molecular weight of resultantpolymers , we found tliat MMA polymerization initiated by NVPP is a typical radical mechanism of polymerization which undergoes a process of continuous initiationand bifunction termination , while VPP-initiated polymerization suggested a mech-anism of living radical process fpolymerization with instantaneous initiation , chain-transfer to monomer , without termination).

Preparation and shaping of solid acid SO_4^(2-)/TiO_2 and its application for esterification of propylene glycol monomethyl ether and acetic acid

The solid acid SO_4^(2-)/TiO_2 was prepared by immersion method and applied for synthesis of propylene glycol methyl ether acetate(PMA) through esterification reaction of propylene glycol monomethyl ether(PM)and acetic acid(HAc). The optimal catalyst preparation condition was determined by orthogonal analysis of parameters in a five-factor and four-level test. The obtained solid acid catalysts were characterized in detail by means of X-ray powder diffraction, thermogravimetry, pyridine adsorbed IR analysis, scanning electron microscopy, and BET surface area method. Synthesis of PMA was studied in this paper through experimental investigation of reaction conditions such as temperature, molar ratio of reactants, catalyst dosage and agitation speed. Based on its possible reaction mechanism, a pseudo-homogeneous kinetic model was established and its activation energies E_a^+ and E_a^-,65.68 × 10~3J·mol^(-1) and 57.78 × 10~3J·mol^(-1), were estimated. To prepare shaped solid acid catalyst SO_4^(2-)/TiO_2, the shaping method of impregnation–shaping–impregnation was applied. The optimal molding formulation of solid acid catalyst, obtained from the orthogonal test, was found to be binder 7 wt%, reinforcing agent 20 wt%, pore forming material 2.5 wt%, and lubricant 4 wt%.The results of performance test of catalyst demonstrated that the shaped solid acid catalyst exhibited high activity and stability.

Liquid-phase esterification of methacrylic acid with methanol catalyzed by cation-exchange resin in a fixed bed reactor:Experimental and kinetic studies

The kinetic behavior of esterification between methacrylic acid and methanol catalyzed by NKC-9 resin was studied in a fixed bed reactor.The reaction was conducted in the temperature range of 323.15 to 368.15 K with the molar ratio of reactants from 0.8 to 1.4 under certain pressure.The measurement data were regression with the pseudo-homogeneous(P-H),Eley-Rideal(E-R),and Langmuir-Hinshelwood(L-H)heterogeneous kinetic models.Independent adsorption experiments were implemented to gain the adsorption equilibrium constants of four components.Among the above three models,the L-H model exhibited the best fitting results.The stability of NKC-9 was evaluated by long-term running with the yield of methyl methacrylate no decrease during 3000 h operation.The structure and physicochemical properties of the new and used catalyst were performed by several characterizations including thermogravimetric analysis(TG),scanning electron microscope(SEM),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FT-IR)and so on.

A novel method for fabricating polydimethylsiloxane microfluidic chip master molds

We proposed a novel method of fabricating polydimethylsiloxane (PDMS) microfluidic chip polymer master molds in this paper. The method mainly includes two steps. First, a stainless steel slice was laser etched to form a metal model. Then, the organic solution of poly(methyl methacrylate) (PMMA) was casted onto the metal model to fabricate the PMMA master which subsequently would be used to fabricate PDMS chips. We systematically researched different laser parameters influencing the surface status of microchannels and obtained optimized etching parameters. We investigated and optimized the organic solution composition of PMMA while casting chip masters, and developed a method to form fine polymer masters using two different viscosity solutions to cast the model in turn, and studied the repeatable replication. Then, we investigated physical performance of this chip and evaluated the practicability by analyzing Rhodamine B. Compared with present methods, the proposed method does not need photolithography on photoresistant and chemical etching. The entire fabricating progress is simple, fast, low-cost and can be controlled easily. Only several minutes are required to make a metal model, 3 hours for a PMMA master, and one day for PDMS chips.

Kinetics of Elution of Gentamicin from a Gentamicin-Loaded PMMA Bone Cement

Antibiotic-loaded poly (methyl methacrylate) bone cement (ALBC) is widely used for anchoring joint replacements as a means of reducing the potential for peri-prosthetic joint infection (primary cases) and treating a patient who has an infected joint replacement (revision cases). One shortcoming of the cement is the high maximum exothermic temperature experienced upon polymerization (Tmax), a phenomenon that, it has been postulated, may cause or be implicated in thermal necrosis of peri-prosthetic tissues. There are many reports in the literature on methods of reducing Tmax, with one such study involving the addition of a phase change material (microencapsulated paraffin) (MEPAR) to the cement powder or adding a chain-stopping chemical (1-dodecyl mercaptan) (DDM) to the liquid. In that report, the results of gentamicin elution tests were presented. In the present work, those results were used to calculate various indices of gentamicin elution kinetics, namely 1) diffusion coefficient (Dgent);and 2) values of the coefficients in four equations that are widely used to model antibiotic elution from ALBCs. We found 1) the difference in Dgent of either a MEPAR- or DDM-containing formulation, on the one hand, and that of the control cement, on the other, was not significant;and 2) a consistent trend in the value of only one coefficient in one of the four model equations, with this change suggesting insignificant difference in gentamicin elution mechanism between an experimental cement formulation and the control cement. The implications of these findings for guiding selection of additives that simultaneously produce significant reduction of Tmax but minimal effect on gentamicin elution kinetics are discussed. This guide is a novel contribution to the literature.

Constrained Nonlinear Model Predictive Control of a Polymerization Process via Evolutionary Optimization

In this work, a nonlinear model predictive controller is developed for a batch polymerization process. The physical model of the process is parameterized along a desired trajectory resulting in a trajectory linearized piecewise model (a multiple linear model bank) and the parameters are identified for an experimental polymerization reactor. Then, a multiple model adaptive predictive controller is designed for thermal trajectory tracking of the MMA polymerization. The input control signal to the process is constrained by the maximum thermal power provided by the heaters. The constrained optimization in the model predictive controller is solved via genetic algorithms to minimize a DMC cost function in each sampling interval.

Cs/SiO_(2)催化合成MMA工艺及宏观动力学研究

采用浸渍法制备了不同Cs质量分数的Cs/SiO_(2)催化剂,并利用XRD､氮气物理吸附､CO_(2)-TPD和NH3-TPD等技术对其进行表征。在固定床反应器中,优化了Cs/SiO_(2)催化丙酸甲酯与甲醛缩合制备甲基丙烯酸甲酯(MMA)的反应条件,并初步进行了动力学分析。结果表明,Cs质量分数为10%的Cs/SiO_(2)催化剂性能最优,在反应温度为370℃､反应空速为1.2 h^(-1)､酯醛摩尔比为1∶1的优化条件下,丙酸甲酯的转化率为46.3%,MMA的选择性接近100%。动力学分析显示丙酸甲酯与甲醛缩合制备MMA的表观活化能为39.1 kJ/mol,非常接近理论值。

钛酸四丁酯催化甲基丙烯酸甲酯与正丁醇酯交换反应动力学研究

由于设备腐蚀和环境污染等问题,甲基丙烯酸丁酯生产工艺逐渐倾向于更为经济环保的酯交换生产工艺。以钛酸四丁酯为催化剂,甲基丙烯酸甲酯与正丁醇通过酯交换法合成甲基丙烯酸丁酯的反应及机理进行了初步研究。首先,根据路易斯酸催化理论,在合理假设和简化的基础上对该反应的机理进行了分析,在此基础上分别建立了基于理想溶液和非理想溶液的动力学模型。通过酯交换反应实验,主要研究了反应温度、反应物初始物质的量之比和催化剂量等因素对反应速率的影响,并根据实验数据回归得到了动力学模型参数和反应的基本热力学数据。结果显示,该酯交换反应为吸热反应,标准摩尔反应焓为14.406 kJ·mol^(-1),正、逆反应活化能分别为70.2和51.1 kJ·mol^(-1)。通过模型计算值与实验数据的比较,证明了推导得到的动力学模型具有较高的可靠性,将为钛酸四丁酯催化甲基丙烯酸甲酯与正丁醇酯交换合成甲基丙烯酸丁酯反应提供一定的理论指导。

PEI@SA微球制备及其对甲基蓝的吸附研究

以海藻酸钠(SA)为基材,通过交联法制备聚乙烯亚胺(PEI)改性吸附剂PEI@SA,研究其对甲基蓝(MB)的吸附性能。采用SEM和FTIR对吸附剂表面形貌和化学结构进行表征。考察pH值、初始染料浓度、吸附时间对吸附性能的影响,然后对吸附过程进行等温线模型和动力学模型拟合。结果表明:PEI@SA对MB的吸附符合Langmuir吸附模型和准二级动力学模型,吸附过程为单分子层吸附,以化学吸附为主。25°C时对MB最大吸附量为88.34 mg/g,是未改性SA的10倍。

偶氮二异丁腈引发甲基丙烯酸甲酯微乳液聚合

以一种新的Y型乳化剂 1 2 丁酰氧基 9 十八烯酸 (BOA) ,制备了甲基丙烯酸甲酯 (MMA)含量高达 2 0 %的微乳液 ,并以油溶性引发剂偶氮二异丁腈 (AIBN)引发其聚合 .实验表明 ,与单体含量较低的微乳液聚合相比 ,MMA在其含量较高的微乳液中聚合时表现出一些明显不同的特征 ,如在聚合初期 ,聚合主要在大粒子内进行 .MMA的聚合与非极性单体的微乳液聚合相比也比较特殊 ,其聚合速度和聚合物分子量与引发剂浓度、单体浓度及乳化剂浓度的关系如下 :Rp ∝ [AIBN]0 .83 [MMA ]0 .49[BOA]-0 .98,Mn ∝ [AIBN]-0 .2 9[MMA]0 .61[BOA]-0 .2 2 .

甲基丙烯醛一步氧化酯化制备甲基丙烯酸甲酯

制备了用于甲基丙烯醛(MAL)一步氧化酯化为甲基丙烯酸甲酯(MMA)的新型催化剂. 在常压和连续搅拌的条件下,考察了反应条件对MAL转化率和MMA选择性的影响,并对反应动力学进行了初步研究. 实验结果表明:当反应温度50℃、氧气流速6 mL/min、甲醇与甲基丙烯醛的摩尔比75、催化剂在反应物中含量2.4%、反应时间60 min时,MAL的转化率可达99.4%, MMA的选择性为95.7%.

甲基丙烯酸甲酯-马来酸酐共聚物的合成及热性能

通过溶液聚合法,在不同的反应温度、不同马来酸酐投料质量百分比的条件下,合成了甲基丙烯酸甲酯-马来酸酐共聚物P(MMA-co-MAH)。通过傅立叶红外光谱以及滴定法对合成的P(MMA-co-MAH)共聚物进行表征,结果表明,在实验条件下甲基丙烯酸甲酯(MMA)与马来酸酐(MAH)均能发生共聚合反应。提高共聚合反应温度以及马来酸酐的投料比都能够显著提高P(MMA-co-MAH)共聚物中的马来酸酐含量。通过对P(MMA-co-MAH)共聚物的热失重分析,利用Ozawa及Kissinger方程研究了共聚物的降解动力学,结果表明,P(MMA-co-MAH)共聚物的热稳定性受聚合反应温度和马来酸酐投料比的共同影响,共聚物中马来酸酐含量对P(MMA-co-MAH)共聚物的热稳定性起决定性作用。

氧化-还原低温引发甲基丙烯酸甲酯/丙烯酸丁酯超浓乳液聚合研究

以乳化剂十二烷基硫酸钠 (SDS)和共乳化剂十六烷醇 (HD)作为复合乳化体系 ,过氧化二苯甲酰(BPO)和N ,N 二甲基苯胺 (DMA)作为氧化还原引发体系 ,甲基丙烯酸甲酯 丙烯酸丁酯 (MMA BA)作为混合单体 ,制备了分散相占 83 %以上的稳定的超浓乳液 ,然后在低温下引发聚合 .探讨了引发剂浓度、氧化剂与还原剂的摩尔比、乳化剂的浓度、液膜增强剂的种类、聚合温度等因素对聚合稳定性和聚合速率的影响 ,测定并计算得到了聚合速率的公式 ;用激光散射粒度分布仪测定了聚合物乳胶粒子的大小及粒径分布 ,用透射电子显微镜观察了聚合物乳胶粒的形态 ,讨论了乳化剂浓度、聚合温度等对乳胶粒形态。

微悬浮聚合法制备纳米聚甲基丙烯酸甲酯微粒

利用微悬浮聚合法对甲基丙烯酸甲酯(MMA)进行聚合,研究了单体、引发剂用量和分散速率对动力学的影响,以及聚合的相关要素与聚合物PMMA微粒大小、分子量和体系黏度的关系。结果表明,单体和引发剂用量对MMA微悬浮聚合的动力学影响符合自由基聚合规律,剪切分散速率增加会提高单体的转化速率及最终转化率。利用此聚合方法,可以得到纳米级PMMA微粒,体系黏度均低于5mPa.s,获得的聚合物具有较高的黏均分子量。