漆酚缩甲醛钕聚合物的特性与表征

由漆酚甲醛缩聚物(PUF)与三氯化钕制备漆酚缩甲醛钕聚合物(PUFN), 并采用元素分析、 IR、 DMTA和GPC对其进行表征. 结果表明, PUF与Nd3+发生配位反应, 其产物PUFN的弹性模量比PUF的大, 热稳定性提高, 并且具有优良的耐化学介质腐蚀性能, 对正丁醇和冰乙酸的酯化反应具有催化活性.     

漆酚缩甲醛钇聚合物的热性能及其表征

利用漆酚甲醛缩聚物(PUF)在非水热溶剂中与三异丙氧钇反应制得漆酚缩甲醛钇聚合物(PUFY),用IR、XPS和TG-DSC对其结构进行表征。结果表明,三异丙氧钇中Y(Ⅲ)与PUF中酚羟基上的氧形成了配位键;在Y(Ⅲ)的作用下PUF侧链进一步交联聚合,产物PUFY的耐热性和耐溶剂性较配体PUF的好。     

AIBN/SmCl3/乳酸体系催化甲基丙烯酸甲酯的反向原子转移自由基聚合

利用稀土金属化合物三氯化钐(SmCl3)和二氯化钐(SmCl2)之间的单电子转移反应,以AIBN/SmCl3/乳酸作为反向原子转移自由基聚合(ReverseATRP)的催化体系,成功地实现了甲基丙烯酸甲酯(MMA)的反向ATRP,并考察了温度、溶剂和组分比对聚合反应的影响.MMA在该体系中的聚合反应是一级反应,所得PMMA的分子量与单体转化率成正比,聚合物的分子量分布较窄(Mw/Mn<1.5),具有活性聚合的特征.     

含硼—氮配键漆酚高分子铜（Ⅱ）：配合物的特性及其表征

含硼－氮配键漆酚高分子与氯化铜的反应产物ＰＵＢＮ－Ｃｕ（Ⅱ）在亚硫酸钠水溶液中能使甲基丙烯酸甲酯于室温下聚合。用红外光谱、Ｘ射线光电子能谱、高效液相色谱等方法对ＰＵＢＮ－Ｃｕ（Ⅱ）进行了表征，并探讨了其引发甲基丙烯酸甲酯聚合的特性和机理。     

碳酸钙在St-MMA悬浮聚合中的应用研究

以碳酸钙为分散剂,过氧化二苯甲酰为引发剂,采用悬浮聚合法合成苯乙烯-甲基丙烯酸甲酯共聚物。研究了碳酸钙用量、反应温度、反应时间、引发剂用量、水与单体体积比、苯乙烯与甲基丙烯酸甲酯体积比对悬浮聚合的影响。结果表明,碳酸钙用量为2.0~3.0g,反应温度为75~80℃,反应时间为3h,引发剂用量为0.3115g,水与单体体积比为5:1~7:1,苯乙烯与甲基丙烯酸甲酯体积比为1/8.5~1:1(单体总体积为9.5m L)时,制得的共聚物颗粒大小均匀,粒径在0.31mm~0.60mm,产率在90%以上。     

Eu0.5La0.5（TTA）3/PMMA温敏漆的制备及性能研究

以氯化铕、氯化镧、噻吩甲酰基三氟丙酮(TTA)为原料合成了Eu0.5La0.5(TTA)3探针分子,将探针分子与甲基丙烯酸甲酯(MMA)混合后聚合,获得Eu0.5La0.5(TTA)3/PMMA温敏漆。采用红外光谱、扫描电镜、紫外吸收光谱及荧光光谱对探针分子及温敏漆性能进行了表征。红外光谱表明,Eu(La)与TTA形成配位键,且镧的掺入并未改变Eu(TTA)3结构;SEM照片显示探针分子为片状晶体;紫外吸收光谱表明,探针分子的最佳吸收波段位于226～381 nm处。340 nm激发下,发现温敏漆在613 nm处具有最强荧光发射峰,且镧的掺杂对Eu(TTA)3发光存在增益作用;不同温度下荧光光谱表明,随着温度的升高,温敏漆荧光发射强度逐渐减弱,说明温敏漆具有良好的温度猝灭特性。     

漆酚铁聚合物的制备及性能研究

以生漆和三氯化铁反应制备漆酚铁聚合物,用红外光谱、涂膜鲜映性仪和光泽度仪等对聚合物结构和漆膜性能进行表征.结果表明,反应温度65℃,反应时间3h,漆酚和三氯化铁物质的量比为8∶1,所生成的漆酚铁聚合物性能较好.     

漆酚缩甲醛钕聚合物催化合成环己酮乙二醇缩酮

以环己酮和乙二醇为原料,漆酚缩甲醛钕聚合物为催化剂合成了环己酮乙二醇缩酮。实验结果表明：在环己酮100mmol,n(环己酮)：n(乙二醇)=1：1,漆酚缩甲醛钕聚合物3．0g,环己烷7．5mL,回流反应1．0h,目标化合物的收率达74％。     

溶剂热体系中甲基丙烯酸甲酯的原子转移自由基聚合

以FeCl3/ PPh3为催化体系,在无引发剂、溶剂热体系中进行甲基丙烯酸甲酯(MMA)的原子转移自由基聚合(ATRP)反应.考察了反应温度与还原剂对反应的影响.实验结果表明,在溶剂热体系中进行的MMA聚合反应符合"活性"/可控聚合,聚合过程中转化率和分子量随时间的增加而增大,所得聚甲基丙烯酸甲酯分子量分布较窄.     

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.     

Determination of Monomer Transfer Constants in Emulsion Polymerization

The monomer transfer constant, C_m can be determined from the chain length distribution (CLD) under conditions in which the monomer transfer reaction rate is much larger than the other chain termination processes. Such reaction conditions are feasible in emulsion polymerization where bimolecular termination reactions are relatively less important. We conducted theoretical investigations aimed at finding the necessary reaction conditions to apply the CLD method to emulsion polymerization. The number of polymer chains per polymer particle needs to be large enough in order to keep the effects of unknown chain lengths to a minimum, i.e., the unknown chains formed during the nucleation period and those which stop growing when the polymerization is stopped for sampling. In emulsion polymerization, the polymer concentration at the polymerization locus is higher than the corresponding bulk polymerization as long as monomer droplets exist, and the polymer transfer reaction may possess significant effects under conditions where monomer transfer reactions are important. The Monte Carlo (MC) simulation results have shown that although the CLD profile becomes broader due to the polymer transfer reactions, they do not significantly change the slope, from which C_m is determined. According to the present simulation results, the CLD method is considered applicable even when the polymer transfer reaction cannot be neglected. The MC simulation method can be used to find the experimental conditions where the CLD method is applicable.     

Cationic polymerization of 1,3-pentadiene in the presence of vanadium oxychloride

The cationic polymerization of 1,3-pentadiene in the presence of vanadium oxytrichloride is studied. 1,3-Pentadiene is shown to polymerize at a high rate to high monomer conversions in the absence of proton-donor compounds in the catalytic system. The initial rate of 1,3-pentadiene polymerization is proportional to the concentration of VOCl₃ in the system and demonstrates an extremal dependence on the initial concentration of 1,3-pentadiene. The polymerization process is distinguished by an induction period whose duration increases with a decrease in the reaction temperature. Regardless of polymerization conditions, with an increase in the monomer conversion, the molecular-mass distribution of the polymer widens owing to formation of a high-molecular-mass fraction, which, depending on reaction conditions, can be consumed in formation of the gel fraction. It is shown that the degree of unsaturation and the microstructure of poly(1,3-pentadiene) are almost independent of the polymerization conditions.     

Deviations from topotaxy in trioxane polymerization

It is shown by photomicrographic techniques that the polymer does not always form in a unique crystallographic direction in the solid-state polymerization of trioxane. The polymerization in these instances cannot therefore be considered topotactic in the usually accepted sense. The crystallization of the polymer is attributed to factors which are, in a sense, secondary to the actual reaction mechanism.     

Preparation and colloidal stability of monodisperse magnetic polymer particles

A previously proposed method was examined for producing monodisperse, submicrometer-sized magnetic polymer particles. The method applies soap-free emulsion polymerization during which Fe3O4 magnetic nanoparticles are heterocoagulated onto precipitated polymer nuclei. To chemically fix the magnetic particles to the polymer nuclei, vinyl groups were introduced on the Fe3O4 particles in a preliminary surface modification reaction with methacryloxypropyltrimethoxysilane, and methacryloxypropyldimethoxysilane (MPDMS) was added to reaction systems of the soap-free emulsion polymerization. The colloidal dispersion stability of magnetic polymer particles was improved by the addition of an ionic monomer, sodium p-styrenesulfonate (NaSS), during the polymerization. The polymerizations were carried out with styrene monomer and potassium persulfate initiator in ranges of NaSS concentrations (0-2.4 x 10(-3) M), NaSS addition times (60-80 min), and monomer concentrations (0.3-0.6 M) at fixed concentrations of 1.6 x 10(-2) M initiator and 1.3 x 10(-2) M MPDMS for pH 4.5 adjusted with a buffer system of [CH3COOH]/[NaOH]. The addition of NaSS during the polymerization could maintain the dispersion stability of magnetic polymer particles during the polymerization. Selection of the reaction conditions enabled the preparation of colloidally stable, submicrometer-sized magnetic polymer particles that had coefficients of variation of distribution smaller than the standard criterion for monodispersity, 10%.     

Potentiometric saccharide detection based on the pK(a) changes of poly(aniline boronic acid)

A novel approach for the potentiometric detection of saccharides using poly(aniline boronic acid) is presented. A model is described in which the electrochemical potential is sensitive to the change in the pK(a) of the conducting polymer as a result of boronic acid-diol complexation. In this system, boronic acid complexation is the mode of transduction and it is manifested as changes in the electrochemical potential of the polymer with remarkable selectivity. Characteristics of both transient and steady-state response associated with the complexation are discussed. The presence of Nafion and fluoride during the electrochemical polymerization of 3-aminophenylboronic acid are shown to impact the sensitivity and the stability of the electrode response. The sensor sensitivity is improved significantly by increasing the concentration of sodium fluoride during the polymerization. Finally, the nature of the selectivity of the boronic acid-diol reaction under these conditions is explored by using molecular orbital calculations.     

LaCl3-KCl熔体结构的分子动力学研究

用分子动力学计算机模拟方法研究了LaCl3-KCl熔体的结构和输运性质, 获得了熔体的偏径向分布函数、配位数、键角分布及均方位移等信息. 计算结果表明, 熔体中存在变形的八面体LaCl63-离子. K 和Cl-离子是熔体电流的主要携带迁移者, 而LaCl3浓度对熔体结构有较大的影响.     

Catalyst-transfer polycondensation. mechanism of Ni-catalyzed chain-growth polymerization leading to well-defined poly(3-hexylthiophene)

We studied the mechanism of the chain-growth polymerization of 2-bromo-5-chloromagnesio-3-hexylthiophene (1) with Ni(dppp)Cl2 [dppp = 1,3-bis(diphenylphosphino)propane], in which head-to-tail poly(3-hexylthiophene) (HT-P3HT) with a low polydispersity is obtained and the M(n) is controlled by the feed ratio of the monomer to the Ni catalyst. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectra showed that the HT-P3HT uniformly had a hydrogen atom at one end of each molecule and a bromine atom at the other. The reaction of the polymer with aryl Grignard reagent gave HT-P3HT with aryl groups at both ends, which indicates that the H-end was derived from the propagating Ni complex. The degree of polymerization and the absolute molecular weight of the polymer could be evaluated from the 1H NMR spectra of the Ar/Ar-ended HT-P3HT, and it was found that one Ni catalyst molecule forms one polymer chain. Furthermore, by reaction of 1 with 50 mol % Ni(dppp)Cl2, the chain initiator was found to be a bithiophene-Ni complex, formed by a coupling reaction of 1 followed by insertion of the Ni(0) catalyst into the C-Br bond of the dimer. On the basis of these results, we propose that this chain-growth polymerization involves the coupling reaction of 1 with the polymer via the Ni catalyst, which is transferred intramolecularly to the terminal C-Br bond of the elongated molecule. We call this mechanism "catalyst-transfer polycondensation".     

Emulsion polymerization of vinyl acetate. II

The emulsion polymerization of vinyl acetate was investigated at low ionic strengths and has quite unusual kinetics. The rate of polymerization is dependent on the initiator concentration to the first power and independent of soap concentration. In seeded polymerizations, the rate of polymerization depends on initiator to the 0.8 power, particle concentration to the 0.2 power, and monomer volume to 0.35 power. In all cases the rate of polymerization is almost independent of monomer concentration in the particles until 85–90% conversion. These results were rationalized by the following mechanism: (a) polymerization initiates in the aqueous phase because of the solubility of the monomer and is stabilized there by adsorption of ionic soap on the growing polymer molecule; (b) the growing polymer is swept up by a particle at a degree of polymerization (under our conditions) of about 50–200. Growth continues in the particle. This sweep-up is activation-controlled as both particle and polymer are charged. (c) Chain transfer to the acetyl group of monomer gives a new small radical which cyclizes to the water-soluble butyrolactonyl radical, and reinitiates polymerization in the aqueous phase; (d) the main termination step is reaction of an uncharged butyrolactonyl radical with a growing aqueous polymer radical. A secondary reaction at low ionic strength is sweep-up of an aqueous radical by a particle containing a radical. At high ionic strength, this is the major termination step. The unusual kinetic steps are justified by data from the literature. They are combined with the usual mechanisms operating for vinyl acetate polymerization and kinetic equations are derived and integrated. The integral equations were compared with the experimental data and shown to match it almost completely over the whole range of experimental variables.