窄分布低分子质量端羟基聚四氢呋喃的合成与研究

以三氟化硼乙醚配合物(BF3·OEt2)为催化剂,环氧丙烷(PO)为起始剂,二氯甲烷(CH2 Cl2)作溶剂,通过四氢呋喃的阳离子开环聚合合成了窄分子质量分布(Mw/Mn＜1.3)的端羟基聚四氧呋喃(PTHF).研究了三氟化硼乙醚配合物用量、溶剂用量、起始剂用量、反应时间对PTHF分子质量(Mn)及其分布(Mw/Mn)...     

宽或双峰分子量分布HDPE的研制Ⅱ.聚合工艺条件对聚合产物性能的影响

采用双金属复合催化剂制备出了宽或双峰分子量分布的高密度聚乙烯（ＨＤＰＥ）,并对所合成出的聚合物进行了结晶行为分析,分子量及分子量分布测试。结果表明：用双金属复合催化剂法制备的ＨＤＰＥ的力学性能优于传统方法。     

烯烃共聚物的分子质量分布和短链支化分布的同步去卷积方法

烯烃共聚物的分子质量分布(MWD)和短链支化分布(SCBD)可通过凝胶渗透色谱和红外检测器联用进行表征,MWD和SCBD的去卷积对反应动力学特性分析和动力学参数估计具有重要作用。基于微观结构瞬时分布方法提出了一种MWD和SCBD的同步去卷积方法,对比阐述了MWD单独去卷积、MWD和SCBD分步和同步去卷积3类方法,通过解析模拟生成的微观结构数据和实际样品的表征结果,比较了分步和同步去卷积方法。结果表明,同步去卷积方法应用于模拟生成的微观结构数据时能更为高效、准确地还原已知的原始特征参数;应用于实际样品表征结果时能得到更具物理意义和规律性变化的可靠特征参数。     

α—甲基苯乙烯与苯乙烯和丙烯腈悬浮共聚合反应的研究

研究了α-甲基苯乙烯与苯乙烯和丙烯腈三种单体在羟基磷酸钙-SMA钠盐复合分散体系中进行悬浮共聚合反应,制取三元共聚物.介绍了羟基磷酸钙-SMA钠盐复合分散剂的分散与稳定作用,并就各组分及聚合条件对所得共聚物性能的影响进行探讨.同时分别用DSC法和PGC法测定产物的玻璃化温度和组成.     

生物可吸收材料PDLLA的聚合条件研究

通过乳酸脱水合成出高纯度的D,L 丙交酯。以辛酸亚锡为引发剂,进行丙交酯开环聚合为聚乳酸(PDL LA)的实验研究。讨论了D,L 丙交酯开环聚合的影响因素和PDLLA聚合条件。     

超分子组装与聚合研究的新进展

超分子化学的组装与聚合是化学学科的一门新兴热点边缘学科,本文简要介绍了超分子化合物的组装、聚合及应用,详细综述了:(1)大环超分子化合物的聚集与组装;(2)大环超分子凝胶的形成;(3)磺化杯芳烃的合成及其分子组装。     

聚合条件对聚丙烯酸乳胶增稠性影响的研究

用反相乳液聚合方法制备了增稠性好的聚丙烯酸乳胶。研究了引发剂、交联剂、单体浓度、水相ｐＨ、聚合温度和油－水相重量比对聚丙烯酸乳胶增稠性影响。试验结果表明，通过控制水相ｐＨ和引入非离了型亲水单体（如丙烯酰胺）可制得耐电解质性能好的聚丙烯酸增稠剂。     

基于聚合物分子量分布的乙烯淤浆聚合工艺优化

分子量及分布是聚合物生产过程中极其重要的质量指标,但目前的技术水平并不能实现分子量及其分布的实时测量,基于反应机理的动态建模是实现其软测量的重要方法。以乙烯淤浆聚合工艺为研究对象,基于聚合机理,分别以聚合物的平均分子量和分子量分布为目标,以循环气中氢气乙烯比为决定变量,采用稳态优化方法求取聚合物生产的工艺条件。结果表明:以平均分子量为优化目标所得的结果与分析值的偏差较大,虽然聚合物的平均分子量符合要求,但聚合物的分子量分布曲线与所需产品的分子量分布曲线之间的最大误差可达0.092;而以分子量分布曲线为目标所得的最大误差只有0.069。因此,以分子量分布曲线作为目标的优化方法明显比常规的以平均分子量为目标的优化方法优越。     

乙烯淤浆聚合动态分子量分布模拟计算

以乙烯淤浆聚合反应过程为研究对象,提出动态分子量分布的严格模型的数值计算方法。将动态分子量分布的大规模微分代数混合模型解耦为小规模微分代数方程组动态矩模型与大规模常微分方程组粒数衡算模型,然后通过变量解耦的方法进一步将大规模粒数衡算方程组转换为序贯差分方程组,实现了乙烯动态分子量分布严格模型的数值模拟计算。动态模拟乙烯聚合反应从一个稳态切换到另一个稳态,通过在切换后稳态的分子量分布计算结果与Flory分布计算方法进行比较,两者得到的分子量分布曲线吻合很好,证实了本文提出的动态模拟计算方法的精度和准确度都获得良好的保障。     

On the molecular weight distribution polydispersity of continuous living‐radical polymerization

Batch living‐radical polymerization techniques were used to produce polymers with molecular weight distributions approaching the narrowness of truly living (ionic) systems. Continuous reactors may offer some advantages for living polymerization in copolymer morphology, but continuous polymerization with any level of backmixing will broaden the molecular weight distribution. This study used simple moment techniques to demonstrate that idealized living‐radical polymerization in a single stirred tank reactor will have a polydispersity of 2. This is also the theoretical minimum polydispersity for a truly living polymerization. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 539–542, 2004     

Calculating molecular weight distributions in emulsion polymerization under conditions of diffusion limited chain transfer

When highly reactive chain transfer agents with low water solubilities (e.g., long chain thiols) are used in emulsion polymerizations, transport of the chain transfer agent (CTA) from the monomer droplets to the polymer particles can become diffusion limited. Consequently, the concentration of CTA in the particles is lower than expected, resulting in apparent transfer constants that can be much lower than the actual transfer constants obtained from studies with homogeneous systems such as bulk or solution. Furthermore, molecular weights will be greater than those obtained in homogeneous systems with the same overall concentration of CTA. There are currently no techniques or methodologies available for predicting molecular weight distributions when the transport of CTA is diffusion limited. Apparent transfer constants may be used but they are typically restricted to a given system and operating conditions. In this work, we describe how the actual CTA concentration in the polymer particles can be estimated through analysis of instantaneous molecular weight distributions. This information is then used to calculate the cumulative molecular weight distribution during the polymerization. Comparisons with experimental molecular weight distributions validate the essential correctness of the approach, but also highlight potential problems. The extension of the approach to online applications is discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 217–227, 2000     

Determining molecular weight scale and molecular weight distribution of ethylene-tetrafluoroethylene alternating copolymer via a rheological technique

A self-scaling rheology-based technique was developed to determine the molecular weight (MW) and molecular weight distribution (MWD) of ethylene-tetrafluoroethylene alternating copolymer (ETFE). The self-scaling technique makes determining MW and MWD with isolated completely rheological method possible. Moreover, the two key parameters (the plateau modulus and zero-shear viscosity) were obtained by more robust numerical technique, which let determining MW and MWD via rheological method initiated by Tuminello [Macromolecules 1993, 26, 499] being building on more robust and rigid basis. Our case overcomes the shortage of Tuminello's method and gives more practical and simply mean to analyze the MW scale and MWD in the production and application of ETFE. It is found that the peak MW of a ETFE (commercial grade: EP541) is 1.73 × 10⁵ g/mol, the MWD curve is a pattern with a slightly raised “shoulder” at high-molecular mass end, and a high peak on the median and the polydispersity is broad (the polydispersity index is near to 10.3). The wide polydispersity indicates the commercial ETFE combining good processability of relative lower MW molecules with physical properties of high MW ones. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

高分子量水溶性疏水缔合聚合物的合成条件研究

对合成AM/AHAC二元共聚物的引发体系进行了筛选,研究发现,用K2S2O8-DMAAM引发体系合成的聚合物相对分子量高于其它引发体系,并在此基础上进一步考察了DMAAM浓度、单体浓度、反应温度及反应时间对聚合物分子量的影响。结果表明,单体浓度为20%、K2S2O8浓度为80 mg/L,DMAAM浓度为60 mg/L,反应温度为30℃,反应时间为6 h条件下,合成的聚合物分子量较高。     

Emulsion polymerization of tetrafluoroethylene: effects of reaction conditions on the polymerization rate and polymer molecular weight

The emulsion polymerization of tetrafluoroethylene (TFE) was carried out in a semibatch reactor using a chemical initiator (ammonium persulfate) and a fluorinated surfactant (FC-143). The effects of the reaction condition were investigated though the polymerization rate, molecular weight of polytetrafluoroethylene (PTFE), and stability of the dispersion. The emulsion polymerization of TFE was different from conventional emulsion polymerization. The polymerization rate was suppressed when the polymer particles were significantly coagulated. The polymerization rate increased with operating temperature, surfactant concentration, and agitation speed, due to the enhanced stability of the polymer particles. However, once the parameter value was reached, the rate decreased due to the coagulation of the particles. Stable PTFE dispersion particles were obtained when the surfactant concentration was in the range between 3.48 × 10⁻³ and 32.48 × 10⁻³ mol/liter, which is below critical micelle concentration (CMC). The molecular weight of the PTFE obtained was a function of the surfactant and initiator concentrations, and the polymerization temperature. The molecular weight increased as each parameter decreased. This is against the phenomena observed in a conventional emulsion polymerization. A stable PTFE dispersion polymer having a high molecular weight was obtained by optimizing the reaction conditions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 777–793, 1999     

Optimal operation of ethylene polymerization reactors for tailored molecular weight distribution

This work presents a comprehensive steady‐state model of the high‐pressure ethylene polymerization in a tubular reactor able to calculate the complete molecular weight distribution (MWD). For this purpose, the probability generating function technique is employed. The model is included in an optimization framework, which is used to determine optimal reactor designs and operating conditions for producing a polymer with tailored MWD. Two application examples are presented. The first one involves maximization of conversion to obtain a given MWD, typical of industrial operation. Excellent agreement between the resulting MWD and the target one is achieved with a conversion about 5% higher than the ones commonly reported for this type of reactor. The second example consists in finding the design and operating conditions necessary to produce a polymer with a bimodal MWD. The optimal design for this case involves a split of the initiator, monomer, and modifier feeds between the main stream and two lateral injections. To the best of our knowledge, this is the first work dealing with the optimization of this process in which a tailored shape for the MWD is included. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Calculation method of molecular weight averages in polymerization with chain-length-dependent termination

A systematic method for calculating the molecular weight distribution moments in free radical polymerization where termination rate depends on the size of the participating radicals, is presented. The central part of the method is the evaluation of the distribution of termination rates in the balance equations. From an adopted functional form of the termination rate constant, the moment equations are derived. For evaluating the moments of the termination rate distribution an approximate reconstruction of the radical chain length distribution using Laguerre polynomials is proposed. The calculation method can handle termination by disproportionation and combination simultaneously and allows easily to take into account diffusioncontrolled initiation, propagation and chain transfer reactions. The usefulness of the method is illustrated by simulating the bulk polymerization of methyl methacrylate and styrene. The calculated results of conversion, molecular weight averages (M _n,M _w,M _z and M _z+1) and polydispersity are in good agreement with the reported experimental data.     

The molecular weight distribution of oligomers

It is shown that the relation $\text{P}{}_{\mathrm{w}}\text{P}{}_{\mathrm{n}}\text{= 2}$ or the nonuniformity U = 1 is only a limiting case for high degrees of polymerization, is no more valid for oligomers. Two new relations are derived, one including and one excluding monomers. For the oligomer part of cationically produced polystyrenes the second relation is in good agreement with experiments.