PSt-TMI合成及其共聚动力学研究

以BP0为引发剂,甲苯为溶剂,采用溶液聚合法合成了低3-异丙烯基一α,α’-二甲基苄基-异氰酸酯(TMI)含量的PSt-TMI共聚物(wTMI-O．03～O．11),确定了FTIR方法测定共聚物中TMI含量的方法,并对反应动力学与共聚物组成进行了研究。结果表明：总体反应速率与单体浓度成正比,与引发剂浓度O．5次方成正比,80℃下反应时还存在热引发,终止方式为双基终止;反应总体活化能随单体配比中TMI分率增大而升高。引发剂浓度增大则产物分子量减小,分子量分布不变。随反应转化率提高分子量分布指数增大、产物中TMI含量略有下降。GPC串联紫外分析表明,产物中高分子量部分TMI含量高于低分子量部分中TMI含量。     

(N,N′—二乙基)偶氮二异丁脒盐酸盐引发下的丙烯酰胺水溶液聚合

本文研究了(N,N′—二乙基)偶氮二异丁脒盐酸盐引发下丙烯酰胺水溶液聚合的反应动力学。得出了聚合速率方程式为RP=KP[EAIBA]05[AM]。测定了聚合表观活化能。并研究了聚合条件对产物分子量及其分布的影响。利用该引发—聚合体系,获得了相对分子量上千万超高分子量聚丙烯酰胺。     

丁二烯在烯土配位催化剂下的活性聚合

本文用动力学方法处理了丁二烯在NdCl₃·3i-PrOH-AlEt₃催化体系中,-70℃下聚合结果:发现聚合体系中不存在可检测出的使活性中心失活的不可逆的链终止反应和限制产物分子量的链转移反应,产物的分子量分布较窄并具有特高顺1,4-微观结构,平均活性链寿命相当长。     

（N,N‘—二乙基）偶氮二异丁脒盐酸盐引发下的丙烯酰胺水溶液聚合

本文研究了（Ｎ,Ｎ‘－二乙基）偶氮二异丁脒盐酸盐引发下丙烯酰胺水溶液聚合的反应动力学。得出了聚合速率方程式为Ｒｐ＝Ｋｐ「ＥＡＩＢＡ」＾０．５「ＡＭ」．测定了聚合表观活化能。并研究了聚合条件对产物分子量及其分布的影响。利用该引发一聚合体系,获得了相对分子量上千眼高分子量聚丙烯酰胺。     

兖州煤与大庆减压渣油在共处理过程中的相互作用：Ⅱ.甲苯可溶重质产物族组

通过对兖州煤与大庆减压渣油共处理重质产物的组成,分子量及分子量分布的考察,研究了甲苯可溶重质产物组成性质随反应条件的变化规律。结果表明,在较低反应温度（３７５－４２５℃）下,共处理减缓了重质产物中饱和份的转化,同时使树脂和沥青质含量降低;在较高反应温（４５０℃）下,由于煤与渣油的裂解程度增加,共处理与单独处理重质产物中饱和份含量均降为０,共处理重质产物的树脂＋沥青质含量显著增加,共处理使重质产物的分子量增大,且随着反应温度的升高,重质产物的分子量逐渐减小,同时分子量分布逐渐变窄 。     

兖州煤与大庆减压渣油在共处理过程中的相互作用Ⅱ.甲苯可溶重质产物族组成和分子量的变化规律

通过对兖州煤与大庆减压渣油共处理重质产物的组成、分子量及分子量分布的考察,研究了甲苯可溶重质产物组成性质随反应条件的变化规律.结果表明,在较低反应温度(375～425℃)下,共处理减缓了重质产物中饱和份的转化,同时使树脂和沥青质含量降低;在较高反应温度(450℃)下,由于煤与渣油的裂解程度增加,共处理与单独处理重质产物中饱和份含量均降为0,共处理重质产物的树脂+沥青质含量显著增加.共处理使重质产物的分子量增大,且随着反应温度的升高,重质产物的分子量逐渐减小,同时分子量分布逐渐变窄.     

高聚物的分子量分布

研究分子量分布的意义高聚物的分子是由单体分子聚合而成,除了少数几种蛋白质外,其分子量是不均一的。分子量多分散性是高聚物的基本特性之一,其多分散程度决定于聚合反应的机理,试样的处理过程,以及老化裂解等影响。高聚物所表現的性质,均为其不同分子量的分子对此种性质供献的总和。因此研究高聚物的分子量分布,无论对力学性能或溶液性质的了解,以及聚合机理的探討,产品质量的控制与改进都有重要的意义。聚合及降解反应的机理无疑是聚合或降解产物分子量分布的决定因素,从反应动力学可以导出分子量     

H_2O/TiCl_4/Py体系引发苯乙烯正离子聚合

研究了在少量吡啶(Py)存在下由水(H2O)四氯化钛(TiCl4)体系引发苯乙烯于二氯甲烷正己烷中进行碳正离子聚合,分别考察[Py]、[H2O]和[TiCl4]对聚合速率、产物分子量与分子量分布的影响.实验结果表明,少量亲核试剂吡啶(Py)对聚合反应起着重要作用,可有效地降低聚合速率和使分子量分布变窄;随着[H2O]和[Py]降低或[TiCl4]增加,聚合产物的分子量增加,而分子量分布指数(Mw Mn)基本维持在1.8左右;随着[Py]增加,聚合速率降低;随着[H2O]和[TiCl4]增加,聚合速率提高.聚合速率对单体浓度呈一级动力学关系,对Py、H2O和TiCl4的反应级数分别为-0.72、0.72和1.86.聚合速率对TiCl4浓度呈接近二级动力学关系,这可能与体系中TiCl4主要以二聚体形式存在有关.聚合转化率和产物分子量均随着反应时间延长而逐渐增大,PS的数均分子量与转化率呈线性增加关系.     

伯胺引发NNTA开环聚合对水的耐受性研究

研究了苄胺引发N-取代甘氨酸-N-硫代羧酸酐(NNTA)开环聚合.聚合对引发剂当量的水(100~600μg/g)具有很好的耐受性,能保持良好的可控性,聚类肽产率高(>70%),分子量可控(1600~7500),分子量分布较窄(1.13~1.25).随着水含量的增加(达到单体当量)(14000μg/g),聚合产率与产物分子量均有不同程度的下降.MALDI-To F质谱证明所得聚类肽均为苄胺引发产物,水不能引发NNTA聚合.聚合动力学实验表明该聚合体系表现出准一级动力学反应的特征,在不同单体转化率时,聚合物数均分子量与单体转化率呈线性关系,分子量分布窄,证明该聚合体系具有可控性.进一步地,使用未经除水精制处理的市售THF溶剂和未经烘烤除水的反应瓶进行NNTA聚合反应,也表现出很好的可控性.NNTA单体易合成、易储存,聚合时不受微量水的影响,极大地降低了聚类肽的合成难度,有利于聚类肽材料的推广与应用.     

六甲基环三硅氧烷非平衡聚合的研究

六甲基环三硅氧烷(D_3)在为催化剂,二甲亚砜为促进剂的情况下聚合,得到了分子量分布窄且没有大环体的聚二甲基硅氧烷。本文指出了反应溶液中溶解的氧会降低催化剂的活性。在除去了溶液中的氧以后,聚合反应速度大为加快,D_3转化率几乎达100％,而且得到的聚合物是活性高分子,可以继续进行聚合。同时还研究了在除氧以后D_3非平衡聚合反应的特点。     

Use of germanium initiators in ring‐opening polymerization of L‐lactide

Three different, new germanium initiators were used for ring‐opening polymerization of L ‐lactide. Chlorobenzene and 120 °C was a usable polymerization system for solution polymerization, and the results from the polymerizations depended on the initiator structure and bulkiness around the insertion site. The average molecular weights as measured by size exclusion chromatography increased linearly with the monomer conversion, and the molecular weight dispersity was around 1.2 for initiators 1 and 2 , whereas it was around 1.4 for initiator 3 . The average molecular weight of poly(L ‐lactide) could be controlled with all three initiators by adding different ratios of monomer and initiator. The reaction rate for the solution polymerization was, however, overall extremely slow. With an initial monomer concentration of 1 M and a monomer‐to‐initiator ratio of 50, the conversion was 93% after 161 h for the fastest initiator. In bulk polymerization, 160 °C, the conversion was 90% after 10 h. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3074–3082, 2003     

Dispersion polymerization of styrene in ethanol: Monomer partitioning behavior and locus of polymerization

A thermodynamic model has been proposed for the simulation of monomer partitioning behavior in the dispersion polymerization of styrene in ethanol. The monomer concentration in the polymer particles is very low (20 vol% at 5% conversion) and decreases further as the polymerization proceeds. It is independent of stabilizer concentration but is strongly dependent on initial monomer concentration. The partitio n coefficient ([M_p]/[M_c]) of styrene increases from 0.8 to 1.1 with incresing conversion. There are two polymerization loci in dispersion polymerization, namely the continuous and polymer phases. Competition between solution and heterogeneous polymerization has been observed in this system. The rate of dispersion polymerization is dependent on initial monomer concentration but is independent of initiator concentration at higher conversions. The molecular weight of the polymers produced by this process increases with increasing conversion and decreases with increasing initiator concentration.     

Effect of synthesis parameters on polymethacrylic acid xerogel structures and equilibrium swelling

Hydrogels based on crosslinked polymethacrylic acid were synthesized via free-radical polymerization in aqueous solution, using N,N′-methylene bisacrylamide as a crosslinking agent and 2,2′-azobis-[2-(2-imidazolin-2-yl)propane] dihydrochloride as an initiator. The influence of the reaction parameters (the neutralization degree of methacrylic acid and the initial monomer concentration) on the equilibrium swelling degree, the swelling kinetic parameters and the basic structural properties of xerogels was investigated. The change of synthesis parameters leads to the change of the basic structural parameters of xerogel, as well as the equilibrium swelling degree and the initial swelling rate of the hydrogels. It is found that there are power form relationships between the equilibrium swelling degree, the initial swelling rate and the structural xerogel’s properties and the change of the neutralization degree of monomer, i.e. the monomer concentration. The examined correlations proved that the crosslinking density is the crucial parameter which determines all the other investigated structural and swelling parameters. The article is published in the original.     

Equilibrium anionic polymerization of α-methylstyrene in p-dioxane

The equilibrium anionic polymerization of α-methylstyrene in p-dioxane, with potassium as initiator, has been investigated at 5, 15, 25, and 40°C by using high-vacuum techniques. The comparison of these results with those obtained previously for the equilibrium polymerization of α-methylstyrene in tetrahydrofuran revealed that, although the values of ΔG_1c, the free-energy change upon the polymerization of 1 mole of liquid monomer to 1 bases-mole of liquid amorphous polymer of infinite chain length, are the same for both systems, there is a distinct effect of the solvent. This effect is reflected in the value of monomer equilibrium concentration and its variation with polymer concentration and is explained in terms of a solvent–monomer and solvent–polymer interaction parameter.     

Polymerization of vinyl chloride at reduced monomer accessibility. II. Polymerization at subsaturation pressure with emulsion PVC as seed

Vinyl chloride was polymerized at 59–92% of saturation pressure in a water-suspended system at 45–65°C with an emulsion poly(vinyl chloride) (PVC) latex as a seed. A water-soluble initiator was used in various concentrations. The monomer was continuously charged as vapor from a storage vessel kept at lower temperature. Characterization included determination of molecular-weight distribution and degree of long-chain branching by gel permeation chromatography (GPC) and viscometry, thermal dehydrochlorination, and microscopy. The polymerization rate decreases with decreasing pressure but is reasonable even at the lowest pressure. The molecular weight decreases with decreasing pressure and increasing initiator concentration and also with increasing polymerization temperature, if the initiator concentrations are chosen to give a constant initiator radical concentration. The degree of long-chain branching increases with increasing initiator concentration and decreasing monomer pressure but is unaffected by the polymerization temperature, if the initiator radical concentration is kept constant. The thermal stability decreases with decreasing M _n, while the degree of long-chain branching has only a minor influence. The most important factor in the system influencing the molecular parameter is the monomer accessibility.     

分散聚合法制备PVP微球的研究

以N-乙烯基吡咯烷酮(NVP)为初始单体,乙酸乙酯为分散介质,采用分散聚合法制备了分散性能良好、粒径为3～4μm的聚乙烯基吡咯烷酮(PVP)微球.考察了单体、分散剂及引发剂浓度对PVP微球的粒径、单体转化率及分子量的影响,并对PVP的结构和性能进行研究.结果表明,单体浓度增加,PVP微球粒径和分子量增大,单体转化率升高;分散剂浓度增加,PVP微球粒径变小,分子量增大,单体转化率升高;引发剂浓度增加,PVP微球粒径变大,分子量减小,单体转化率升高.与溶液聚合法相比,分散聚合法制备的PVP分子量较小且具有一定的结晶性.     

极性单体阴离子型聚合反应产物的分子量分布

关于任意官能度多官能团引发剂瞬时引发并有单体链终止的阴离子型聚合反应体系,本工作通过非稳态动力学分析,求得了分子量分布函数和平均聚合度的一般表示式,讨论了单体的最大消耗量和聚合物的官能度分布问题,建立了从反应的初始条件和单体转化率计算产物的各种分子参数的方法。上述理论结果适用于甲基丙烯酸甲酯等极性单体在极性溶剂中的阴离子型聚合反应。数值计算的结果表明:当引发剂的官能度为2时,除了少数例外,所得聚合物的分子量分布一般具有双峰。     

Photo-initiated polymerization of N-vinylcarbazole in dichloromethane solution containing azobisisobutyronitrile

Azobisisobutyronitrile, as a photosensitizer of the polymerization of N-vinylcarbazole in dichloromethane solution at λ = 366 nm, has also been shown to quench the polymerization that normally occurs in its absence. As the initiator concentration is raised, the polymer yields at first decrease and pass through a minimum before increasing to about twice the initial value, at the solubility limit of the initiator. The product polymers are predominantly formed through a cationic mechanism though a free radical fraction is also evident, particularly at high initiator concentrations. Kinetic mechanisms compatible with the experimental evidence are considered and indicate that the higher molecular weight cationic fraction is formed through the intermediacy of the first excited triplet states of both the monomer, and a complex of the monomer and solvent. Quenching of the former species by azobisisobutyronitrile results in initiation of the polymerization, but quenching of the latter species quenches polymerization. The low molecular weight radical fraction, on the other hand, is considered to be formed through the quenching of the first excited singlet state of the monomer by azobisisobutyronitrile.     

The effect of MWCNTs on molar mass in in situ polymerization of styrene and methyl methacrylate

Two different in situ-polymerization techniques were studied, emulsion polymerization and combined emulsion/suspension polymerization, with styrene and methyl methacrylate in the presence of different multiwalled carbon nanotubes (MWCNTs). Molar masses and molar mass distributions were determined by size exclusion chromatography, and particle size of the emulsions by dynamic light scattering and rotation rheometry. The compatibility of the MWCNTs and monomer affected polymerization and therefore the molar masses. The MWCNTs stabilized the emulsions, and molar mass distributions narrowed with higher amounts of MWCNTs. In emulsion polymerization of styrene, MWCNTs increased the molar mass. The increase of molar mass was based on the compatible molecular structures of MWCNTs and styrene, so that individual nanotubes were covered by monomer clouds when initiator arrived. In combined emulsion/suspension polymerization of styrene, MWCNTs reacted with the initiator and there was less initiator to polymerize the monomer. There is probably a critical surface area of MWCNTs, for which more initiator is consumed in the reaction with MWCNTs than in polymerization of the monomer. In emulsion polymerization of MMA, monomer clouds around MWCNTs do not form due to incompatible molecular structures, and nanotubes do not enhance polymerization of MMA. In combined polymerization, the initiator is reacting with the nanotubes and the tube is acting as a carrier for initiator, and molar masses are higher.     

Anionic heterogeneous polymerization of methacrylonitrile by n-butyllithium

The anionic heterogeneous polymerization of methacrylonitrile by butyllithium in petroleum ether was investigated. The polymerization was of the “living” type, as seen from the linear dependence of the molecular weights on [MAN]/[BuLi]. This behavior was further supported by block polymerization experiments in which the monomer was added in two portions and the molecular weights obtained were directly proportional to the total monomer concentration. The initiator efficiency was low, and initiator consumption was only about 2%. This fact, together with the results of the block polymerizations showed that there was preferential addition of monomer to the growing chain ends rather than to the initiator. The molecular weights were independent of the rate of monomer addition. This as well as the “living” behavior of the polymerization of methacrylonitrile on a wide range of monomer and catalyst concentrations and the absence of chain transfer to monomer was essentially different from that of the similar heterogeneous polymerization of acrylonitrile by butyllithium previously investigated. This is due to the absence of an α-acidic hydrogen in methacrylonitrile.