Radiation-induced cationic polymerization of vinyl ethers in solution: 3. The influence of monomer and solvent concentrations on the rate of polymerization of ethyl vinyl ether in ether solvent

The influence of the monomer concentration on the rate of propagation of the radiation-induced polymerization of super-dry ethyl vinyl ether has been examined in detail in two ether solvents, diethyl ether and diglyme, chosen for their different dielectric constants and their different abilities to solvate ions. Estimations of the rate of initiation and of the rate of termination have made possible the evaluation of the rate constants of polymerization. Very similar values were obtained in both ethers. Experiments were also performed in benzene-diglyme and diglyme-methylene chloride mixtures. The results are in good agreement with the previous studies, made in benzene and methylene dichloride, and confirm the important role of the solvation of the free propagating species concerning the reactivities observed in the radiation-induced polymerization of EVE in solution.     

分子印迹功能单体选择方法研究进展

分子印迹技术是以一种化合物作为模板,制备出对该模板分子具有特定＂记忆功能＂的聚合物。在分子印迹技术中,功能单体的选择对分子印迹聚合物的识别性能起着至关重要的作用,总结了近些年关于预测功能单体的分析方法及其分析原理,并做了详细的介绍。     

Substitution effects and average molecular weights in non-linear stepwise polymerization

The authors' method of calculating average molecular weights, in the pre-gel region, for stepwise polymerization of polyfunctional monomers, is extended to systems where the functional groups exhibit unequal reactivities induced by substitution effects in the course of the reaction.     

Kinetic model for lonic polymerization initiated by difunctional initiator with monomer transfer

The kinetics of difunctional ionic polymerization with monomer transfer and without assumption of instantaneous initiation is studied theoretically. The set of kinetic differential equations is rigorously solved by way of graphical theory. Expressions for the molecular weight distribution (MWD) function, the number- and weight-average degrees of polymerization, and the distribution of functionality are obtained. A procedure is proposed for calculating the MWD curve and the values of other molecular parameters.     

Intrinsic unequal reactivity and average molecular weights in non-linear stepwise polymerization

The general expressions of average molecular weights in the pre-gel region, for stepwise polymerization of polyfunctional monomers endowed with both A and B coreactive functional groups, are extended to systems where some or all of the B groups react at different rates. The method of calculation is always based on the propagation expectation and the presence of by-product in the reactions is taken into account.     

辐射聚合在高分子合成中的应用

简要综述了辐射聚合的引发聚合原理以及特点,分别介绍了辐射聚合在水凝胶、药物缓释剂、增稠剂、高吸水性树脂以及其他领域的应用,报道了辐射聚合在应用领域的最新研究进展,并对辐射聚合合成高分子的应用前景做了进一步的展望。     

Preparation and polymerization of vinyl monomers containing a heterocyclic pendant group

New vinyl monomers having an isoxazole heterocyclic group were synthesized and were polymerized in dimethylformamide using azobisisobutyro-nitrile as a free radical initiator. The dependence of the rate of polymerization on monomer and initiator concentrations was determined, as well as the activation energy of polymerization. The addition of Lewis acid was found to affect the rate of polymerization. The prepared monomers were copolymerized with styrene, vinyl acetate, acrylonitrile and methyl methacrylate. The monomer re-activity ratios of all the systems were determined by linear and non-linear methods, and the Q and e values for the monomers were calculated by considering the four copolymerization systems in each case. ©1997 SCI     

离子液体在原子转移自由基聚合中的应用进展

综述了离子液体作为溶剂、单体、引发剂或配体参与原子转移自由基聚合。离子液体具有独特的物理化学性能,可作为溶剂或配体直接参与聚合反应,也可以通过化学修饰合成离子液体型聚合单体或引发剂,利用ATRP技术制备出含有聚合离子液体链段或端基的功能性高分子材料。这种材料可应用于太阳能电池、聚合物电池、光敏元件、吸附剂或传感元件等多个领域,成为高分子材料研究领域的一个重要课题。     

Seeded emulsion polymerization of vinyl acetate: order of reaction with respect to initiator

The emulsion polymerization of vinyl acetate has been studied using carefully prepared seed lattices. Experiments were carried out in which temperature, particle size and the monomer-polymer ratio could be varied independently. In all cases the polymerization rate was proportional to the initiator concentration raised to the 0.7 power. No new particles were formed. The importance of polymerization in the aqueous phase and changes in the propagation rate coefficient are discussed.     

Molecular weight distribution in living polymerization

An easily obtained parameter for characterizing polymers is the molecular weight distribution (MWD). Polymers with different MWD have different properties. The MWD can be easily influenced with controlled polymerization technologies. Examples of how these methods influence the properties of block and gradient copolymers in wetting and dispersing additives are discussed. These wetting and dispersing additives are used to make solvent-borne paints and aqueous pigment concentrates. An advantage of modulation of the MWD is the ability to fine tune-specific properties, such as the compatibility or the wetting activity of the polymer.     

阴离子聚合体系活性种聚合活性的探讨

讨论了非极性和极性溶剂中有机锂活性种的活性,指出添加少量极性添加剂或在极性溶剂中,由于溶剂化作用,有机锂活性种的聚合活性有所降低。     

Modeling of the bulk free radical polymerization up to high conversion—three stage polymerization model. II. Number-average molecular weight and apparent initiator efficiency

The equations for predicting the number-average molecular weight are derived on the basis of the three stage polymerization model (TSPM) in this paper. By applying the equations, a plotting approach is proposed to determine the apparent initiator efficiency defined as f[(α_td+1)/2] and the constant of chain transfer to monomer, where f is the initiator efficiency and α_td denotes the fraction of the termination rate constants by disproportionation. Using the approach to plot the experimental data in the literature, it is found that the chain transfer to monomer can be neglected for both methylmethacrylate (MMA) and styrene (St) polymerizations, but it can exert a significant effect on ethylmethacrylate (EMA) polymerization. In addition, the apparent initiator efficiency is found to be independent of reaction temperature and initiator concentration at each stage. The values of f[(α_td+1)/2] at gel effect stage are slightly reduced as compared with that at low conversion stage for MMA and EMA polymerizations. However, it decreases significantly at gel effect stage for St polymerization. Using the equations derived and the apparent initiator efficiencies obtained from TSPM plots, the number-average molecular weights at different conversions can be predicted. Comparisons show that the agreement between predictions and experimental data is satisfactory.     

自交联丙烯酸酯类反应性微凝胶乳液的聚合稳定性

采用半连续种子乳液聚合方法合成了自交联丙烯酸酯类反应性微凝胶乳液,研究了聚合工艺条件对聚合反应稳定性的影响。结果表明,当增大乳化剂SDS/OP-10的用量或加快预乳化单体的滴加速度时,聚合反应稳定性增加;随着引发剂过硫酸钾(KPS)、交联剂三羟甲基丙烷三丙烯酸酯(TMPTMA)和单体用量的增加,微凝胶颗粒分子间的交联反应增强,聚合反应稳定性下降。加入功能性单体甲基丙烯酸(MAA)和丙烯酸(AA)都能使聚合反应的稳定性增强,随着MAA用量的增加,聚合反应稳定性呈先增强后下降的趋势。当所加入的SDS/OP-10质量分数为3%~4%、KPS为0.4%~0.6%、TMPTMA为1%~3%、MAA不超过3%及单体为30%~40%,预乳化单体滴加速率为20~30 mL/h时,聚合过程的稳定性最好。由傅里叶变换红外光谱分析可知,通过优化聚合条件,得到了含有官能性环氧基和羧基的丙烯酸酯类反应性微凝胶乳液。     

The effect of the compostion of heterogeneous polymerization catalyst on ethylene–1-butene copolymerization

The effect of ethylaluminium dichloride (EADC) in the heterogeneous Ziegler-Natta catalyst on the ethylene–1-butene copolymerization and the molecular structure of the resulting copolymer was investigated. SiO₂-supported TiCl₄ catalysts having different EADC/Ti molar ratio were prepared by changing the amount of EADC in feed during the catalyst preparation. Ti oxidation states of the prepared catalysts were changed with EADC/Ti molar ratio, and it contained the higher fraction of Ti(3+) and Ti(2+) at the higher EADC/Ti molar ratio. The change in EADC/Ti molar ratio of the catalyst was also shown to influence on the copolymerization performance. Xylene-solublility value corresponding to the fraction having low molecular weight with higher 1-butene content, decreased as EADC/Ti molar ratio decreased. The chemical compositional distribution of PE copolymer was shown not to be affected by EADC/Ti molar ratio of the catalyst significantly.     

Modeling of branching density and branching distribution in low-density polyethylene polymerization

Low-density polyethylene (ldPE) is a general purpose polymer with various applications. By this reason, many publications can be found on the ldPE polymerization modeling. However, scission reaction and branching distribution are only recently considered in the modeling studies due to difficulties in measurement and computation of scission effect and branchings of polymer. Our previous papers [Kim, D.M., et al., 2004. Molecular weight distribution modeling in low-density polyethylene polymerization; impact of scission mechanisms in the case of CSTR. Chemical Engineering Science 59, 699-718; Kim, D.M., Iedema, P.D., 2004. Molecular weight distribution modeling in low-density polyethylene polymerization; impact of scission mechanisms in the case of a tubular reactor. Chemical Engineering Science, submitted for publication] are concerned with the scission reaction during ldPE polymerization and its effect on molecular weight distribution (MWD) of ldPE for various reactor types. Here we consider branching distributions as a function of chain length for CSTR and tubular reactor processes. To simultaneously deal with chain length and branching distributions, the concept of pseudo-distributions is used, meaning that branching distributions are described by their main moments. The computation results are compared with properties of ldPE samples from a CSTR and a tubular reactor. Number and weight average branchings and branching density increase as chain length increases until the longest chain length. The concentrations of long chain branching (LCB) are close to those of first branching moment in both CSTR and tubular reactor systems. The branching dispersity, a measure for the width of the branching distribution at a certain chain length, has the highest value at shorter chain length and then monotonously decreases approaching to 1.0 as chain length increases. Excellent agreements in branching dispersities between calculation with branching moments and prediction with assumption of binomial distribution for a tubular reactor and CSTR processes show that the branching distribution follows a binomial distribution for both processes.     

马尿酸分子印迹聚合物的合成及性能研究

以马尿酸为模板分子,2-乙烯基吡啶为功能单体,乙二醇二甲基丙烯酸酯为交联剂,偶氮二异丁腈为引发剂,在甲醇溶液中制备了马尿酸分子印迹聚合物。该聚合物对模板分子具有良好的亲和性和选择性,用作液谱固定相可将其与结构类似物酪氨酸快速基线分离,并对功能单体种类进行了选择。     

微反应器在聚合反应中的应用

微反应器因其良好的混合和传热性能近年来开始应用到聚合反应中,并表现出巨大潜力。本文对微反应器在自由基聚合、离子聚合和逐步聚合中的应用进行了系统综述。相比于传统的釜式反应器,微反应器可以更好地调节聚合产物分子量和分子量分布、控制共聚组成和分子结构。在强放热聚合反应中,利用微反应器可以获得窄分子量分布的聚合产物;在扩散控制的聚合反应中,利用微反应器可以大大缩短反应所需时间。微反应器在聚合反应领域中的拓展依赖于对反应机理和微反应器特点的深入理解,相关的基础研究将成为这一领域发展的关键。     

分子印迹技术的研究与应用

分子印迹技术是一种制备具有分子识别功能的聚合物的新技术,介绍了分子印迹技术的基本原理与印迹聚合物的制备方法,综述了该技术在传感器、色谱、固相萃取、药物手性分离方面的研究与应用,并对未来的发展方向进行了展望。     

Configurational statistics of copolymers prepared by complex-radical polymerization

Radical copolymerization is considered theoretically taking into account the effect of complexing on the configurational statistics of macromolecules formed. Akinetic model has been developed that considers, apart from the ordinary addition of single monomer units to a propagating chain, the possible addition of monomer unit pairs along with a complexing agent in the form of a ternary complex. Within the framework of this model, the problem of calculating the probabilities of formation of any sequences of monomer units (taking into account their microtacticity) in a macromolecule has been rigorously solved as well as the problem of finding the composition distribution of the copolymer formed. It has been shown that this distribution is described by a conventional Gauss law and the appropriate parameters are given. Possible generalizations of the suggested approach are indicated.     

2，4-二羟基二苯甲酮分子印迹聚合物的合成及性能研究

采用分子印迹技术,以2,4-二羟基二苯甲酮为模板分子,2-乙烯基吡啶为功能单体,二甲基丙烯酸乙二醇酯为交联剂,偶氮二异丁腈为引发剂,在乙腈溶液中合成2,4-二羟基二苯甲酮分子印迹聚合物。通过平衡吸附和液相色谱的方法分析了印迹聚合物的识别特性。研究结果表明,聚合物对印迹分子具有很好的亲和性和特定的选择性,用作液谱固定相可将其与结构类似物2-羟基-4-甲氧基二苯甲酮快速基线分离。