动态扭振法研究聚甲基丙烯酸甲酸／蒙脱土纳米复合材料的本体插层聚合

用动态扭振法研究塑性塑料聚甲基丙烯酸甲酸（PMMA）／蒙脱土（MMT）复合体系的本体插层聚合，并试用处理交联体系固化的Folry理论，非平衡态热力学涨落理论和Avrami方程研究PMMA／MMT复合体系的本体插层聚合，求取表观活化能Ea.实验发现，PMMA／MMT插层聚合转化率曲线中后期与热固性树脂的固化曲线极为类似，表明剥离后的蒙脱土片层在复合材料中起到交联点的作用。     

动态扭振法研究聚甲基丙烯酸甲酯/蒙脱土纳米复合材料的本体插层聚合

用动态扭振法研究热塑性塑料聚甲基丙烯酸甲酯 (PMMA) /蒙脱土 (MMT)复合体系的本体插层聚合 .并试用处理交联体系固化的 Flory理论、非平衡态热力学涨落理论和 Avrami方程研究 PMMA/ MMT复合体系的本体插层聚合 ,求取表观活化能 Ea.实验发现 ,PMMA/ MMT插层聚合转化率曲线中后期与热固性树脂的固化曲线极为类似 ,表明剥离后的蒙脱土片层在复合材料中起到交联点的作用     

改进的微乳液聚合制备的聚甲基丙烯酸甲酯的力学和光学性能研究

研究了改进的微乳液聚合方法制备的聚甲基丙烯酸甲酯(PMMA)的力学和光学性能, 并与本体聚合制备的PMMA相比较. 研究结果表明, 由改进的微乳液聚合制备的PMMA具有较高的Tg和富间规度, 在较宽的温度范围内具有较高的力学模量. 此外, 它的拉伸强度、拉伸模量及断裂伸长率均比本体聚合制备的PMMA样品高. PMMA的折光率与制备方法关系不大, 但由改进的微乳液聚合制备的PMMA样品消光系数更小, 更加透明. 这说明由改进的微乳液聚合方法制备的PMMA具有更广泛的应用前景.     

超临界二氧化碳中无水相涂料的合成与表征

为了减小传统纸张涂布中涂料水分对涂布能耗、涂布质量以及对涂布原纸质量的影响,研究了以超临界二氧化碳为反应介质,制备聚甲基丙烯酸甲酯(PMMA)和碳酸钙颜料混合的粉末涂料粒子.通过FTIR、GPC-十八角度激光光散射联用技术对PMMA组成结构进行了表征,考察了反应体系中引发剂浓度、单体浓度、稳定剂浓度、反应温度和反应时间对聚合反应的转化率和聚合产物的分子量的影响.实验表明,当反应条件为反应压力10MPa,反应温度75℃,反应时间8h,单体浓度0.10g/mL,引发剂浓度0.10×10-2g/mL,稳定剂浓度0.06×10-2g/mL时,其聚合反应的转化率较高,同时PMMA的分子量适中,分子量分布窄.SEM观察到混合涂料粒子颗粒均匀,表明颜料在粉末涂料体系中分散性良好.     

聚甲基丙烯酸甲酯接枝多壁碳纳米管的制备及表征

采用原位聚合的方法,分别在本体及超临界CO2介质中将聚甲基丙烯酸甲酯(PMMA)接枝到多壁碳纳米管(MWNTs)表面,通过GPC、拉曼光谱、TGA等手段对样品进行表征.聚合产物的GPC结果表明,体系中的PMMA存在游离和接枝两种状态;拉曼光谱中峰的红移以及D峰与G峰强度比值的增加证明PMMA与MWNTs之间存在化学键作用;TGA结果表明PMMA在本体和超临界CO2中的接枝率分别为39 %和27%.     

Cu0/2,2′-联吡啶/CCl4和CuCl2/2,2′- 联吡啶/偶氮二异丁腈催化引发体系中的苯乙烯 "活性"自由基乳液聚合研究

分别以Cu0/2,2′-联吡啶(Bpy)和CuCl2/Bpy配合物为催化剂,CCl4和偶氮二异丁腈(AIBN)为引发剂,较为详细地研究了苯乙烯的原子转移自由基乳液聚合规律.结果表明:其乳液聚合体系均显示出了"活性"聚合的基本特征,即数均分子量与转化率呈线性关系,但聚合反应一经引发,聚合物的分子量就达数万,且分子量约为理论值的5至20倍;Cu0/Bpy/CCl4体系的MWD与本体聚合相当,而CuCl2/Bpy/AIBN体系的MWD比其本体聚合体系大,最小为1.64;研究Cu0/Bpy/CCl4体系发现,乳液聚合与悬浮聚合在"活性"特征上没有本质的区别,但两者在动力学上有些差异;跟踪乳液聚合过程中的pH值发现,体系中的pH值随反应时间的延长呈下降趋势,并可能影响聚合速率.     

2,2′-二邻甲氧基苯基-4,4′,5,5′-四苯基-1,2′-二咪唑复合光引发体系的光聚合动力学研究

本文研究了对2,2′-二邻甲氧基苯基-4,4′,5,5′-四苯基-1,2′-二咪唑(BMOIM)复合光引发体系引发聚合动力学过程.采用紫外光谱仪对引发剂、供氢体、增感剂在紫外区的吸收谱图进行了表征.利用实时红外光谱仪对复合光引发体系引发聚合动力学过程进行实时监测,考察了不同光强、引发剂浓度以及不同官能度单体对反应速率及最终双键转化率的影响.结果表明,在引发剂浓度为0.6%(质量分数)时,20s内双键转换率达到96%,随着引发剂浓度的提高,聚合速率增大.聚合速率以及最终双键转化率随着光强增大而增大;双官能团单体的最终双键转化率比三官能团单体的最终双键转化率要高.     

Reversible Addition‐fragmentation Chain Transfer Polymerization Grafted from Silicon Surface to Prepare Poly(methyl methacrylate) Brushes

通过共价键锚固链转移剂4-氰基-4-二硫代苯甲酰基戊酸琥珀酯于硅片表面,然后采用可逆加成-断裂链转移（RAFT）自由基聚合方法制备了聚甲基丙烯酸甲酯（PMMA）高分子刷. 聚合动力学研究表明,在反应进行2小时后,PMMA的厚度随聚合时间的增大而几乎呈线性增大,具有明显的活性聚合特征. 用椭圆偏光仪、X-光电子能谱（XPS）、原子力显微镜（AFM）及接触角测试对硅片表面的PMMA高分子刷进行了表征.     

纳米AgBr/PMMA光致变色杂化材料制备与表征

采用本体聚合法制备了纳米AgBr/PMMA(聚甲基丙烯酸甲酯)光致变色杂化材料. XRD分析表明，纳米AgBr/PMMA杂化材料是无定形的. SEM分析表明， AgBr含量不同，杂化材料的断面形貌明显不同，随AgBr含量的增加，杂化材料由韧性断裂向脆性断裂转变. EDS面分析表明， Ag、Br元素在杂化材料中均匀分布.所制备的纳米AgBr/PMMA杂化材料具有一定的光致变色效应.     

橡胶接枝苯乙烯本体共聚合全程动力学研究(Ⅰ)--接枝行为

橡胶接枝苯乙烯本体聚合的研究目前主要集中于预聚阶段接枝动力学和聚合条件对相转变的影响[1]. 对于后聚阶段, 即相转变后的接枝行为, 尤其是接枝率与橡胶相内包容物的关系、接枝率与高转化率聚合动力学的关系, 接枝率与橡胶相结构的关系等则研究很少. 这些因素对最终聚合物的性能起着至关重要的作用, 因此, 研究橡胶接枝苯乙烯本体聚合相转变以后接枝率的变化, 并找出橡胶相形态演绎过程的规律很有意义.     

Characteristic Events in Free Radical Polymerization of Lower n-alkyl Methacrylates

It is well known that the free radical bulk polymerization of lower n-alkyl methacrylates is characterized by autoacceleration after definite conversions of the monomers. The conversion vs.time curves of polymerization have a typical 'S' shape. There are several characteristic points in these curves: the onset of autoacceleration (point M), the maximum in the polymerization rate (point S) and the end of the polymerization (point K). We have observed points P and R (maximum and minimum of autoacceleration) as inflection points in the derived polymerization rate vs. time curve. In this work, the free radical bulk polymerizations of methyl, ethyl and butyl methacrylates were investigated by differential scanning calorimetry. The effects of the polymerization temperature and the alkyl group length in the esters on the monomer conversions at the points M, P, S, R and K were studied. By regression analysis of the experimental results, relations were developed with which it is possible to predict the positions of the characteristic points, depending on the polymerization temperature and the alkyl group length. This revised version was published online in July 2006 with corrections to the Cover Date.     

Organosilicon hydrides in macromolecular design: Reactions of chain-transfer and hydrosilylation

The chain-transfer constants through silicon hydrides in bulk polymerization of styrene and methyl methacrylate (MMA) were measured with using 15 organosilicon compounds belonging to four classes: oligoorganohydrosilanes, oligoorganohydrosiloxanes, disilalkanes and alkylhydrosilanes. The linear dependences of the logarithm of chain-transfer constant on the sum of the Taft inductive constants of substituents at silicon atoms of a Si-H group were found. The negative values of reaction constants ρ indicate that an electrophilic attack of macroradical onto a hydrogen atom occurs at the limiting stage of the process. Oligoorganohydrosilanes proved to be the most effective chain-transfer agents that can be explained by high electron-donating properties of R₃Si substituents. The increase of the chain-transfer constant values takes place on the accumulation of both trimethylsilyl and silicon hydride groups in a molecule of hydrosilane. The high electrophilicity of PMMA macroradical as compared with a macroradical of polystyrene (PS) is responsible for a greater sensitivity of the polymerization reaction of MMA to the change of the electron density on a hydrogen atom of the organosilicon chain-transfer agent. In the radical polymerization of MMA and styrene in the presence of the chain-transfer agents till high conversion the polymers with a narrower molecular weight distribution (MWD) in comparison with those synthesized by usual polymerization in bulk are formed. The polymers prepared in the presence of multifunctional silanes can be functionalized by the reaction of hydrosilylation and further used in the synthesis of block copolymers.     

Synthesis of iron oxide/poly(methyl methacrylate) composite latex particles: Nucleation mechanism and morphology

A magnetic poly(methyl methacrylate) (PMMA) composite latex was prepared by soapless emulsion polymerization in the presence of ferrofluid, and the ferrofluid was prepared by means of a coprecipitation method. The effects of various polymerization parameters, such as the monomer concentration, ferrofluid content, and initiator concentration, on the conversion curve and particle size of the magnetic composite latex particles were examined in detail. The results showed that two nucleation mechanisms were involved according to the polymerization conditions. In the monomer‐rich and less ferrofluid system, self‐nucleation of PMMA was dominant over the entire course of emulsion polymerization. In the ferrofluid‐rich system, seeded emulsion polymerization was the main course to form the magnetic composite latex particles. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5695–5705, 2004     

Polymerization of methyl methacrylate with ethylene bridged heterodinuclear metallocene of samarium and titanium

A novel heterodinuclear catalyst, ethylene bridged samarocene and titanocene chloride (Sm-Ti), was used both as a single component catalyst (cat.) and also by activation with triisobutyl aluminum (TIBA) to polymerize methyl methacrylate (MMA). The binary catalyst demonstrated higher activity than the single component, but the molecular weight of the resultant PMMA is lower. Ultrahigh molecular weight PMMA (1.5×10⁶) was obtained at an attractive conversion (87%) without any cocatalyst. The effects of polymerization parameters, such as temperature, time, molar ratios of Al(i-Bu)₃/cat. and MMA/cat., were studied in detail. The results showed that the catalytic activity had a rather different dependence on the polymerization temperature with/without TIBA. High molecular weight PMMA was much more easily prepared in a bulk system than in toluene solution. The polymer yielded with about 65% syndiotacticity by 1H NMR and 75% by IR spectroscopy, but its stereoregularity did not change too much with polymerization temperature and the concentration of TIBA.     

Polymerization of methyl methacrylate up to high degrees of conversion: Experimental investigation of the diffusion-controlled polymerization

The kinetic model given by Marten and Hamielec that describes the bulk polymerization of methyl methacrylate (MMA) and accounts for diffusion-controlled termination and propagation was modified to include termination by combination and reaction diffusion and was then tested using isothermal conversion/time and molecular weight data obtained dilatometrically at various temperatures and with three different initiators. For each series of measurements two adjustable parameters were fitted to the conversion/time data. Excellent fits were obtained and the adjustable parameters were found to be the same for all concentration levels of the three initiators and to vary in a simple manner with temperature. The predicted molecular weight averages and molecular weight distributions were in satisfactory agreement with those found experimentally considering the difficulty of measuring high molecular weight PMMA by GPC. This model thus satisfies the specifications for a polymer reactor model that can be used to optimize commercial production systems.     

Polymerization of vinyl chloride in the presence of precipitants. I

The kinetics of bulk and precipitation polymerization of vinyl chloride has been studied over wide range of reaction temperature by using γ-ray induced initiation. The autoacceleration effect, which has been observed by many investigators in the case of chemically initiated bulk polymerization of vinyl chloride above 40°C and has been the most controversial aspect of the bulk polymerization of vinyl chloride, was found to disappear in the bulk polymerization below 0°C. In the bulk polymerization at 40°C, the autoacceleration effect was observed up to 20%, in agreement with the results of previous investigators, and a pronounced effect of the size of polymer particles on the time–conversion curve was observed. The kinetics of precipitation polymerization of vinyl chloride in the presence of some nonsolvents was successfully described by a oneparameter equation. A kinetic scheme, which clearly explains the zero-order reaction behavior of bulk polymerization at low temperature and the kinetic behavior of precipitation polymerization described by the empirical equation, is proposed. The autoacceleration effect in the bulk polymerization at 40°C was considered to be essentially the same phenomenon as the small retardation period observed in the bulk polymerization at low temperature.     

用双硫酯链转移法合成嵌段聚合物

研究了以双硫酯为链转移剂进行的均聚和嵌段共聚物的合成 .首先合成大分子链转移剂 ,得到分子量可控、多分散性系数较小的均聚物PMMA、PBMA、PEMA、PEA、PBA、PMA、PSt,多分散性系数一般小于 1 30 .在相同的条件下 ,甲基丙烯酸酯类的聚合速度最快 ,苯乙烯其次 ,丙烯酸酯类最慢 .用末端带有双硫酯基团的PSt、PBMA、PBA为链转移剂 ,加入多种第二单体聚合得到实测分子量与理论分子量接近 ,且多分散性系数较小的两嵌段聚合物 .在链转移剂和引发剂的比例为 3∶1～ 6∶1的范围内 ,聚苯乙烯同样可以作为第一嵌段得到和其它酯类单体的两嵌段聚合物 .1 H NMR方法证明了聚合物的末端带有双硫酯基团 .嵌段聚合时必须加入微量的自由基引发剂以形成大分子自由基 ,达到较好的控制聚合效果     

PMMA/organomodified montmorillonite nanocomposites prepared by in situ bulk polymerization

Kinetics of the in situ bulk polymerization of methyl methacrylate in the presence of organomodified montmorillonite (MMT) was investigated using differential scanning calorimetry (DSC) and gravimetrically. Different amount and types of MMT under the trade names Cloisite were employed. Using DSC, the amount of heat released versus time, under isothermal conditions, was recorded, and eventually, the time evolution of polymerization rate and monomer conversion was calculated. Results on the variation of monomer conversion with reaction time were in good agreement to corresponding from the gravimetric measurements. The nanocomposites prepared were characterized with WAXD, TEM and FTIR, and their glass transition temperature, T _g, was measured with DSC. Depending on the added amount of nano-MMT, either exfoliated or intercalated structures were obtained. An enhancement of the polymerization rate with the presence of the nanoparticles was observed especially in the gel effect region. This was accompanied by a higher T _g and average molecular weight, as measured by GPC, of all nanocomposites compared to neat PMMA.     

Free-radical polymerization induced macrophase separation in poly(methyl methacrylate)/dimethacrylate blends: Experiment and modeling

This work presents the analysis of a polymerization-induced macrophase separation taking place during free-radical copolymerization of styrene and dimethacrylate in the presence of poly(methyl methacrylate) (PMMA) as a modifier. The PMMA does not participate in the polymerization but induces phase separation in the course of the reaction. An experimental study based on real-time static light scattering measurements with the aim of monitoring the phase behavior during the isothermal copolymerization is firstly presented. Then, an original and innovative contribution is made by modeling the evolution of the unstable region of the phase diagram as a function of conversion and by predicting phase separation in spinodal condition. The analysis is performed using an expression for the free energy of a reactive network-forming mixture based on the Flory–Rehner lattice model for swollen gels. The accuracy of the proposed model is verified by the good agreement found between its predictions and the experimental results.     

Synthesis of PMMA‐b‐PBA block copolymer in homogeneous and miniemulsion systems by DPE controlled radical polymerization

In this research, poly(methyl methacrylate)‐b‐poly(butyl acrylate) (PMMA‐b‐PBA) block copolymers were prepared by 1,1‐diphenylethene (DPE) controlled radical polymerization in homogeneous and miniemulsion systems. First, monomer methyl methacrylate (MMA), initiator 2,2′‐azobisisobutyronitrile (AIBN) and a control agent DPE were bulk polymerized to form the DPE‐containing PMMA macroinitiator. Then the DPE‐containing PMMA was heated in the presence of a second monomer BA, the block copolymer was synthesized successfully. The effects of solvent and polymerization methods (homogeneous polymerization or miniemulsion polymerization) on the reaction rate, controlled living character, molecular weight (M_n) and molecular weight distribution (PDI) of polymers throughout the polymerization were studied and discussed. The results showed that, increasing the amounts of solvent reduced the reaction rate and viscosity of the polymerization system. It allowed more activation–deactivation cycles to occur at a given conversion thus better controlled living character and narrower molecular weight distribution of polymers were demonstrated throughout the polymerization. Furthermore, the polymerization carried out in miniemulsion system exhibited higher reaction rate and better controlled living character than those in homogeneous system. It was attributed to the compartmentalization of growing radicals and the enhanced deactivation reaction of DPE controlled radical polymerization in miniemulsified droplets. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4435–4445, 2009