甲基丙烯酸甲酯-苯乙烯自由基共聚合微型化研究

采用甲基丙烯酸甲酯-苯乙烯自由基共聚合微型化实验,研究了微型化实验条件下,聚合反应工艺条件对共聚产物性能及转化率的影响,说明了高分子微型化实验的可行性。同时,通过微型实验与常规实验相比,进一步阐述微型高分子化学实验不仅装置精巧、新颖,还有利于减少火灾、爆炸等事故的发生几率,而且原料用量及废液量大幅减少,具有节约和环保的双重意义。微型化学实验由于简化了实验装置和实验操作,将其用在教学或科研上,比起常规实验更加简单易行、安全可靠。     

微型高分子化学实验研究

开展了高分子化学实验微型化的研究工作。研制成功了MPC 3型微型高分子化学实验装置 ,研究设计了可操作性较强的微型高分子化学实验方案     

自由基水溶液聚合实验的改进

在高分子化学学生实验中,模仿工业生产中自由基水溶液聚合合成高分子量聚丙烯酰胺的过程,即采用氧化还原引发剂、偶氮类引发剂、过氧化物引发剂三者形成复合引发体系,在较高的单体浓度、非恒温、无搅拌的反应条件下,消耗较低的能量,高效率的聚合过程。该实验改进弥补了现有实验教材内容的空白,更有利于加深对课堂知识的理解,同时加强学生环保与节能意识,培养学生理论联系实际的能力和学生全面考虑问题的能力。     

可控自由基聚合系列实验教学中的一些尝试与经验*

设计了基于可控自由基聚合的系列实验教学,包括:单体和引发剂精制、RAFT试剂合成、不同单体的RAFT/ATRP聚合、RAFT聚合制备嵌段聚合物、ATRP制备嵌段聚合物等。这些实验环环相扣,互相支撑,又有着明显的对比效果。这种尝试有效改进和扩充了常规高分子合成教学中的自由基聚合部分,有效激发了学生的主动性,提高了其分析问题、解决问题的能力。     

DOPA-PSPMA仿生共聚物综合探究性实验研究

为提高本科学生的创新创业能力,通过高分子化学实验教学使学生深入了解仿生共聚物的制备及性能的相关知识,设计了综合探究性实验。通过原子转移自由基聚合法制备仿生共聚物,并将其修饰在多种材料表面。采用X射线光电子能谱、扫描电子显微镜、生物显微镜分别对修饰材料进行表征。该实验通过共聚物的制备使学生掌握高分子化学中活性可控自由基聚合制备共聚物的方法;掌握仿生共聚物设计及构筑方法;使学生学习科研仪器的操作方法,切实提高学生的实践能力。该实验重复性好、创新性及拓展性强,将共聚物设计制备及应用有机结合,适用于高分子专业本科生综合探究性实验。     

高分子聚合工艺新型教学模式的探索与实践

掌握高分子聚合工艺的过程和控制是高分子类相关专业学生必须具有的最基本技能。本文在《高分子聚合工艺学》的课程教学和生产实习的实践教学基础上,介绍了高分子聚合工艺的一种新型教学新模式,即通过增加工艺仿真实验把教学中的学与实习中的看有效地结合起来,并在此基础上升华到产品生产的开、停运转及故障处理的综合设计,形成四合一的新型教学模式。实践证明,这种新型的教学模式可提高学生对高分子大规模聚合工艺的实际操作控制能力、工艺运行方案的综合设计能力及生产的协调组织能力。     

高职食品生物化学新型实验教学体系和案例分析

构建包括基础型实验、综合型实验和设计型实验3个层次内容的食品生物化学新型实验教学体系,并依据典型案例分析,介绍如何妥善处理理论与实践、本课程与后续课程、课内与课外、教学与科研的关系。     

淀粉与碘显色现象探究的微型实验设计

将常规实验"淀粉与碘显色因素探究"设计成微型实验,对浓度、溶液酸碱度、溶剂的种类和含量进行探究.该方案操作便捷、现象明显,适合单人探究,教学效果好.     

RAFT种子乳液聚合反应初期的Monte Carlo模拟

自由基聚合是制备聚合物材料最为重要的技术 .但由于自由基极易进行双基终止 ,一般很难对其结构进行精确的控制 ,所得产物分子量宽 ,组成分布不易控制 ,很难制备嵌段共聚物 . 2 0世纪 90年代出现的活性自由基聚合技术 (RAFT)克服了上述缺点 ,成为高分子化学研究的热点[1] .RAFT聚合以其适用单体广、聚合条件温和以及活性高而成为最具前途的活性自由基聚合技术之一 .迄今为止 ,RAFT的研究大多集中在溶液和本体等均相聚合体系 [2～ 5] .乳液聚合有聚合速率快、环境友好、体系粘度低等优点 ,是活性自由基聚合工业化首选工艺 ,因而近年来活…     

高压下开环聚合制备聚羟基乙酸的工艺研究

从乙交酯(GA)单体出发,以二水合氯化亚锡(SnCl2.2H2O)为催化剂,在高压条件下,进行开环聚合制备高分子量的生物可降解材料聚羟基乙酸(PGA);通过一系列的单因素实验研究了乙交酯的纯度、聚合压力、催化剂用量、聚合时间等因素对聚羟基乙酸相对重均分子量(Mw)的影响规律,根据单因素实验的结果设计并进行了正交试验。采用STATISTICA6.0对正交试验的数据进行分析,得出最优工艺:反应温度196.5℃,反应时间3.5h,催化剂用量n(cat.)/n(GA)=1.7×10-5。进行该工艺验证实验,制备了相对重均分子量可以达到1.61×105的聚羟基乙酸。     

Theories in polymer science - helpful or inhibiting?

Theories in polymer science play an important role in how experiments are designed and results interpreted. Three areas of polymer chemistry are focussed on: step growth polymerization, particularly predictions of equal reactivity of functional groups; free radical chain polymerization with emphasis on structural irregularities and the consequences of these structures for previous theories; free radical copolymerization and the many models at present under discussion aimed at providing a theoretical basis for predicting the outcome of such copolymerization. The question of whether or not we as polymer chemists have been helped or hindered by theory is addressed.     

不同聚合机理的“平均聚合度”公式的分析讨论

平均聚合度和聚合度分布是决定聚合物产品质量的一个重要指标。平均聚合度直接表征聚合产品的分子量的大小,它的大小又决定高分子材料的性能,因此,研究平均聚合度具有重要的理论意义和实际意义。聚合反应按机理分类,可分为链型聚合和逐步聚合,链型聚合又分为自由基聚合、离子聚合、配位聚合,逐步聚合又分为缩聚和加聚反应。本文以自由基聚合、离子聚合、配位聚合以及缩聚的聚合机理为主线,对不同聚合机理对应的平均聚合度的公式进行推导和讨论,并加深理解,掌握其内涵。旨在提高学生对平均聚合度的认识和把握。     

Molecular weight distribution in emulsion polymerizations

A mathematical formulation is given which describes the evolution of the number distribution of the molecular weight (MWD) of linear polymer chains that grow in emulsion polymerization systems. The resulting set of coupled ordinary differential equations takes into account the microscopic events of free radical entry, exit, chain annihilation, bimolecular termination (by combination and disproportionation), and chain transfer in a mono- or polydisperse system. Simple analytic solutions are presented for systems in which the number of particles, as well as the average number of free radicals per particle, is constant and in which the rate coefficients are size independent. These solutions indicate that compartmentalization of the free radicals in the latex particles results in a significant increase in the polydispersity of the polymer produced by emulsion polymerization, compared with that in bulk systems. The theory shows that significant mechanistic information may be obtained from experimental MWDs and that, in principle, experimental conditions may be prescribed to grow a desired MWD. The MWDs are presented in a novel manner that facilitates the comparison of theory with experiment.     

混杂聚合

混杂聚合是指同一体系内有两种或两种以上不同类型的聚合反应同时进行的过程,如自由基聚合与阳离子聚合,自由基聚合与缩聚等。混杂聚合能够在原位形成高分子合金,并有可能得到互穿网络结构（ＩＰＮ）,从而使聚合产物具备较好的综合性能。     

光调控的活性自由基聚合的研究新进展

从引发和催化两个方面概述了光辐照在活性自由基聚合(LRP)中的应用,从机理上详细地分析了光辐照对氮氧调控自由基聚合(NMP)、原子转移自由基聚合(ATRP)、可逆加成-断裂链转移自由基聚合(RAFT)以及有机钴催化的可控自由基聚合反应(CMRP)的影响。与传统自由基聚合相比,光调控的活性自由基聚合方法可在温和的条件下生成自由基,能够克服传统LRP的一些缺陷,如降低催化反应活化能、提高聚合物末端官能度等。同时,本文对光调控反应的进一步应用以及新方法的产生也进行了展望。     

On the formation of narrowly polydispersed PMMA by surface initiated polymerization (SIP) from AIBN-coated/intercalated clay nanoparticle platelets

Various free radical surface initiated polymerization (SIP) conditions were investigated on clay nanoparticles coated with monocationic 2,2'-azobisisobutyronitrile (AIBN) type free radical initiators. Interesting differences in the mechanism of polymer nanocomposite product formation and the role of nanoparticle surface bound AIBN initiators were observed on three types of poly(methyl methacrylate) (PMMA) polymerization conditions: bulk, suspension, and solution. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) measurements confirmed the attachment of the initiator on the clay particles without decomposition of the azo group. XRD and transmission electron microscopy (TEM) showed that a well-dispersed structure was accomplished only by bulk and solution SIP. The suspension SIP product consisted of a partially exfoliated structure as shown by XRD and clay particle aggregate formation as shown by TEM. In general, the molecular weights (MWs) of the surface bound polymers were found to be lower than those of the free polymer. Using the same clay loading and initiator concentrations, we observed that relatively higher MW polymers were obtained from suspension and bulk polymerizations in contrast to solution method. However, the most interesting observation is that the surface bound polymers (on all three conditions) showed much narrower polydispersity compared to that of a typical AIBN type free radical polymerization.     

Block polymer preparation via both anionic and free radical polymerization

A new method of block polymer preparation using combined anionic and free radical polymerization was investigated. In the method the first monomer was polymerized anionically. The resulting polymeric anions were then reacted with an episulfide to form a polymer with mercaptan end-groups. This mercapto—polymer was mixed with a second monomer(s) in an inert solvent for the free radical polymerization. Conventional free radical initiation methods were used to initiate the polymerization of the second monomer but because of the high chain transfer constant of the mercaptan groups, a large number of the free radical chains would grow from the first polymer to form a block polymer. Block polymers difficult or impossible to make by direct anionic polymerization can thus be prepared. Several block polymers, including the new thermoplastic elastomers, poly[(styrene-co-acrylonitrile)-b-butadiene-b-(styrene-co-acrylonitrile)] and poly(bromostyrene-b-butadiene-b-bromostyrene) were prepared by this method.     

Modeling of molecular weight development in atom transfer radical polymerization

A kinetic model has been developed for atom transfer radical polymerization processes using the method of moments. This model predicts monomer conversion, number‐average molecular weight and polydispersity of molecular weight distribution. It takes into account the effects of side reactions including bimolecular radical termination and chain transfers. The determining parameters include the ratios of the initiator, catalyst and monomer concentrations, as well as the ratios of the rate constants of propagation, termination, transfer and the equilibrium constant between radicals and their dormant species. The effects of these parameters on polymer chain properties are systematically simulated. The results show that an ideal living radical polymerization exhibiting a linear relationship between number‐average molecular weight versus conversion and polydispersity approaching unity is only achievable under the limiting condition of slow monomer propagation and free of radical termination and transfers. Improving polymerization rate usually accompanies a loss of this linearity and small polydispersity. For polymerization systems having a slow initiation, the dormant species exercise a retention effect on chain growing and tend to narrow the molecular weight distribution. Increasing catalyst concentration accelerates the initiation rate and thus decreases the polydispersities. It is also shown that for a slow initiation system, delaying monomer addition helps to reduce the polydispersities. Radical termination and transfers not only slow down the monomer conversion rates but also broaden polymer molecular weight distributions. Under the limiting conditions of fast propagation and termination and slow initiation, the model predicts the conventional free radical polymerization behaviors.     

Polybrusselator‐type models

In this paper, the possibility for autocatalysis in polymerization reactions is explored by introducing part of a polymerization mechanism in a model known as Brusselator. It is assumed that monomer concentration is practically constant. Four possibilities are examined: (1) a first radical propagator X, which has an isomer of position of the free electron, Y, dimerizes reversibly and this dimer catalyzes the isomerization of Y to X; (2) the radical propagator X is a polymer with a critical degree of polymerization and has an isomer of position of the free electron Y. This critical radical propagator catalyzes the conversion of Y to X; (3) any radical propagator has an isomer of position of the free electron, Y, and any polymer obtained by recombination of the radicals can catalyze the conversion of Y into its corresponding isomer X; and (4) any radical propagator with a critical degree of polymerization can catalyze the conversion of Y into its corresponding isomer. Isomorphism equations are obtained in all mechanisms, which implies the possibility of limit cycle oscillations (Brusselator model). © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 617–623, 2008     

Modelling Development in Radical (Co)Polymerization of Multivinyl Monomers

Radical polymerization (RP) of multivinyl monomers (MVMs) provides a facile solution for manipulating polymer topology and has received increasing attention due to their industrial and academic significance. Continuous efforts have been made to understand their mechanism, which is the key to regulating materials structure. Modelling techniques have become a powerful tool that can provide detailed information on polymerization kinetics which is inaccessible by experiments. Many publications have reported the combination of experiments and modelling for free radical polymerization (FRP) and reversible-deactivation radical polymerizations (RDRP) of MVMs. Herein, a minireview is presented for the most important modelling techniques and their applications in FRP/RDRP of MVMs. This review hopes to illustrate that the combination of modelling and wet experiments can be a great asset to polymer researchers and inspire new thinking for the future MVMs experiment optimization and product design.