丙烯酰胺分散聚合研究进展

简介分散聚合成核与稳定机理、分散聚合动力学及反应参数对产品质量的影响,重点介绍分散聚合研究进展及其应用领域。     

分散聚合反应的研究进展

介绍了分散聚合反应及其成核和稳定机理,并对分散聚合反应的研究进展情况进行了概述.     

超临界二氧化碳中的分散聚合

在介绍以超临界二氧化碳(Sc-CO2)为介质的分散聚合的成粒机理的基础上,阐明分散剂在分散聚合中的稳定作用,着重综述分散剂的结构组成及用量对分散聚合树脂颗粒特性、聚合速率、产物分子量及分布等的影响,并展望Sc-CO2中分散聚合的研发和应用。     

聚合方法对硅胶表面接枝聚合物过程的影响研究

分别用溶液聚合与分散聚合两种方法,在硅胶载体表面实施了苯乙烯的接枝聚合,重点考察了聚合方法对接枝聚合过程的影响。结果表明,在基本相同的反应条件下,分散聚合体系的接枝率明显高于溶液聚合体系的接枝率,最高可达47%(即47g/100g);除聚合方法之外,影响聚合物在硅胶表面接枝率的因素还有硅胶表面的双键含量、单体浓度、引发剂浓度、温度等。     

分散聚合法制备聚丙烯酰胺研究进展

聚丙烯酰胺在油气田工业、水处理、造纸等领域有着广泛的应用,分散聚合法制备聚丙烯酰胺乳液有着广阔的应用前景。文章从聚丙烯酰胺分散聚合方法、聚合成核机理与聚合稳定机理三个方面综述了国内外分散聚合法制备聚丙烯酰胺的技术现状,通过分析研究,总结出了该研究课题待解决的问题,指出了该课题未来研究方向。     

非水分散聚合

本文综述了非水分散聚合体系的组成、表征、理论研究（如稳定机理、聚合机理、反应动力学）及实际应用等方面的情况。     

原位分散聚合制备聚甲基丙烯酸甲酯/超细碳酸钙复合粒子

为了提高聚合物在超细碳酸钙粒子表面的接枝和包覆,对超细碳酸钙锚固偶氮引发剂及甲基丙烯酸甲酯(MMA)/改性碳酸钙原位分散聚合进行了研究. 碳酸钙粒子经氨基硅烷偶联剂处理后能与偶氮二氰基戊酸反应而实现锚固化,由红外光谱和元素分析证明了偶联和锚固反应.通过锚固在碳酸钙上的偶氮引发剂的引发作用,由MMA分散聚合制备了聚甲基丙烯酸甲酯(PMMA)接枝率高的PMMA/超细碳酸钙复合粒子,PMMA接枝率随聚合转化率增加而增加,而接枝效率随之降低;接枝PMMA的碳酸钙粒子在四氢呋喃和MMA中的分散稳定性明显优于未改性碳酸钙.     

稳定剂对MMA/MA分散共聚合的影响

以乙醇 /水混合溶剂为分散介质 ,偶氮二异丁腈、聚乙烯吡咯烷酮和双甲基丙烯酸乙二醇酯分别为引发剂、稳定剂和交联剂进行了甲基丙烯烯酸甲酯 /丙烯酸 (MMA/AA)的分散共聚合研究。用透射电子显微镜和离心式粒径分布仪测定了粒子大小和粒度分布 ,重点讨论了稳定剂浓度对聚合速率 ,共聚物微球粒径及粒径分布的影响。发现随着稳定剂浓度的增加聚合速率增加 ,转化率提高 ,微球的粒径变小而分散性变好。提出了该体系分散聚合的接枝稳定机理。     

苯乙烯和丙烯腈在聚醚介质中分散共聚合的过程

引言 自20世纪60年代提出分散聚合的概念以来,研究者进行了大量的研究,主要包括成核机理、粒子增长方式、粒子稳定、粒子尺寸分布及控制等[1];特别是90年代后,针对分散聚合制备单分散微米级聚合物微粒子的研究使分散聚合的研究得到了很大的深化, Paine等[2-4] ,Kawaguchi等[5], Prochazka等[6],Lu等[7],Chernyshev等[8],Ahem等[9-10]对分散聚合的机理和动力学过程进行了细致的研究,对聚合过程提出了合理的描述,对控制粒子尺寸及分布提供了有意义的指导.     

分散聚合及单分散聚合物微球制备技术

分散聚合是一种新的聚合方法 ,反应开始前 ,单体、引发剂和分散剂均溶解在介质中 ,随着反应的进行 ,当聚合物链达到临界值时便会从介质中分离出来 ,并借助于分散剂稳定地悬浮在介质中。分散聚合方法已被应用于许多领域 ,如涂料工业、生物工程、医学、信息产业、化学工业等。介绍了分散聚合及单分散聚合物微球制备技术的进展 ,并对其聚合机理及聚合反应影响因素进行了概述。     

Carbonization properties of partially hydrogenated aromatic compounds—I: Carbonization of partially hydrogenated pyrene prepared by Birch reduction

The carbonization properties of pyrene hydrogenated by Birch reduction to a variable extent were studied at 600°C under atmospheric pressure, in order to examine the influence of partial hydrogenation on the carbonization reactivity. Pyrene, which did not yield any coke, produced coke with flow texture after partial hydrogenation. Carbon yield of partially hydrogenated pyrene sharply depended on the hydrogenation extent. The intermediate stage of the carbonization pursued by hot-stage microscopy followed the steps of nucleation, growth and coalescence of anisotropic sphere. Considerable fluidity was observed at the final stage of mesophase development prior to the complete solidification where the benzene insoluble content exceeded 90%. The carbonization mechanism was discussed from the view of the polymerization of hydrogenated pyrene in relation with its structure.     

Time-dependent density functional study for nanodroplet coalescence

The coalescence of nanodroplets is an important interfacial phenomenon and is the key to many real-world applications. However, the microscopic mechanism for this process remains unclear. In this work, we propose a time-dependent density functional theory (TDDFT) to understand and predict this process. The formation of a “peanut” nanodroplet seems key to the coalescence process, before and after which the system is dominated by a nucleation mechanism and an ordinary diffusion mechanism, respectively. It appears that molecular attraction is not only the driving force but also the resistance of droplet coalescence. The velocity distribution indicates that there is a significant mass transfer on the vapor–liquid interphase. During coalescence, there is a clear linear correlation between the free energy and the surface area of the vapor–liquid interface, which means surface tension is the dominant contribution to the free energy.     

Seeding as a means of controlling particle size in dispersion polymerization

Two distinctively different seeded dispersion polymerization processes employing micron and submicron size seed particles, respectively, have been used to gain a better mechanistic understanding of the dispersion polymerization process. Using monodisperse micron-size PMMA particles as seed, it was found that when low monomer/polymer ratios (M/P < 2.50) were used in methyl methacrylate (MMA) seeded dispersion polymerizations, particle growth dominates and the number of particles remains unchanged (i.e., narrow distributions are preserved). However, when higher M/P ratios (>2.50) were applied, bimodal or trimodal particle size distributions were produced, which is considered to result from the competition between particle growth and secondary nucleation. When small amounts of submicron seeds were used with the initial intention of gaining a better understanding of the nucleation process, it was surprisingly found that the final number of micron size particles was nearly the same as the initial number of submicron seed particles over a relatively wide range of reaction conditions, including seed, initiator, stabilizer, and monomer concentrations, and the medium composition. These results indicate that within certain limits seeded dispersion polymerization can be a more robust means of controlling particle size than ab initio dispersion polymerization in terms of reproducibly producing a target particle size. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Role of micellar equilibria on modelling of batch emulsion polymerization reactors

A comprehensive model of emulsion polymerization batch reactors is presented. The nucleation mechanism via micelles is examined in detail through the introduction of a micellar equilibria model. This allows to predict the influence on the process of the emulsifier amount and type and of the solution ionic strength. A comparison with experimental data of styrene and butadiene polymerization is performed.     

On the relation between synthesis parameters and morphology of anionic polycaproamide obtained in organic media. I. Influence of the Na[O(CH2)2OCH3]2AlH2/isophorone diisocyanate catalytic system

Polycaproamide granules were obtained by anionic polymerization of caprolactam in ethylbenzene, using the sodium bis(2-methoxyethoxy) aluminium hydride/isophorone diisocyanate catalytic system. Under these conditions, polymerization occurs heterogeneously and the nature of the particle growth seems to be essentially a microbulk one. The most suitable reaction conditions were established. The morphology of the granules was investigated by scanning electron microscopy. These granules result from the coalescence of a great number of small, spherical particles. the coalescence occurs during solidification of the separated polymer. Numerous globular formations were observed at the surface of the particles. The particles were individualized through mechanical dispersion and measured, and the average number of particles composing the aggregates was calculated. Using wide-angle X-ray scattering and differential scanning calormetry technics, the crystalline structure of the granular polycaproamide was studied. It contains almost entirely the α phase. The heat of fusion decreases slightly as compared with that corresponding to the anionic bulk polycaproamide. A schematic mechanism containing the stages involved in the obtaining of the granular polycaproamide is proposed. © 1996 John Wiley & Sons, Inc.     

Study of kinetics and mechanisms of dispersion polymerization of 2‐hydroxypropyl methacrylate

In the present work, the dispersion polymerization of 2‐hydroxypropyl methacrylate (HPMA) was carried out in No. 120 gasoline/n‐pentanol medium using azobisisobutyronitrile as initiator and a comb‐structured amphipathic polymer as dispersant. The effects of many factors such as the type, structure and concentration of dispersants, and the reaction temperature, on the reaction and the morphology of the polymer microspheres obtained were investigated. It is proposed that the dispersion polymerization of HPMA has two nucleation mechanisms, homogeneous nucleation and inverse mini‐emulsion nucleation. Furthermore, the kinetic of HPMA dispersion polymerization was also studied. © 2001 Society of Chemical Industry     

A population balance model for high shear granulation

In a previous paper, Hoornaert et al. ( Powder Technol. 96 (1998); 116-128) presented data from granulation experiments performed in a 50 L Lödige high shear mixer. In this study that same data was simulated with a population balance model. Based on an analysis of the experimental data, the granulation process was divided into three separate stages: nucleation, induction, and coalescence growth. These three stages were then simulated separately, with promising results. It is possible to derive a kernel that fit both the induction and the coalescence growth stage. Modeling the nucleation stage proved to be more challenging due to the complex mechanism of nucleus formation. From this work some recommendations are made for the improvement of this type of model.     

高分子聚合物包覆无机纳米粒子的研究进展

简单介绍了非液滴内成核法、液滴内成核法包覆无机纳米粒子的原理,重点讨论了乳液聚合法、无皂乳液聚合法、分散聚合法、悬浮聚合法、细乳液聚合法包覆无机纳米粒子的优缺点。针对包覆过程中产生的独立聚合物粒子、独立无机粒子,提出采用引发剂吸附在无机颗粒表面、采用反应性乳化剂和偶联剂处理无机粒子并控制单体用量;针对包覆多个无机粒子,提出采用聚合前超声空化技术。