纳米SiO2表面接枝聚合苯乙烯

通过对纳米SiO2进行表面修饰，引入乙烯基功能基，将其与苯乙烯进行溶液聚合，制备了PS表面接枝纳米SiO2。苯乙烯转化率，接枝率和接枝效率分别为60．7％，24．0％和1．31％。透射电镜表明PS表面接枝纳米SiO2在有机溶剂中具有较好的分散性，可用于制备无机纳米聚合物材料。     

聚合物表面引发接枝聚合

聚合物可以用臭氧氧化,其表面形成过氧化物密度可用碘化物、DPPH 和过氧化酶三种方法测定。经臭氧氧化后的 PU 膜表面可接技共聚 AAm,使其表面的物理及生物性能得到改进。     

纳米Al_2O_3表面接枝聚合改性的研究

为改善纳米Al2O3粒子在聚合物中的分散状况,本工作先在粒子表面引入双键,然后通过溶液自由基引发接枝单体丙烯酰胺和苯乙烯在Al2O3粒子表面的聚合,使接枝物与纳米粒子之间形成化学键合。系统研究了投料方式、引发剂浓度、单体浓度、反应时间等对接枝效果的影响,为调控纳米粒子表面的化学性质提供依据。     

炭黑表面的接枝聚合改性方法

通过接枝高聚物对炭黑表面改性，可显著提高炭黑与基质的相容性，本文介绍了带有可反应端基的聚合物和可分解自由基官能团的聚合物与炭黑间的接枝反应，这种接枝方法可控制接枝链分子量及其分布。     

聚合物表面紫外光接枝改性的研究

介绍聚合物表面紫外光接枝改性的研究方法,其中包括液相和气相接枝、接枝反应的引发方式及其机理,溶剂的影响和选择,针对不同改性要求对接枝单体的使用以及连续化操作的发展。此外,还简要介绍了聚合物表面接枝效果的测试方法和接枝后表面形态的观测方法     

聚合物接枝改性及接枝率的表征

综述了聚合物接枝改性的几种常见方法。如溶液接枝聚合、悬浮接枝聚合、超声波引发接枝聚合、超临界流体技术引发接枝聚合等,介绍了接枝聚合原理、研究和应用,并总结了接枝改性聚合物接枝率的表征方法,包括酸碱滴定法、傅里叶红外光谱（FTIR）、X射线衍射图谱分析（XRD）和元素分析法等。     

硅灰石表面接枝聚合DL-乳酸的研究

研究了一种在硅灰石粒子表面开环聚合嫁接外消旋乳酸的新方法,将外消旋聚乳酸通过化学键直接连接到硅灰石表面.聚乳酸接枝的硅灰石颗粒在乙醇等有机溶剂中分散性更好,可以稳定数天.傅立叶变换红外光谱证实了硅灰石表面成功引入了聚乳酸分子.聚乳酸在硅灰石粒子表面的最大接枝率约为5.8%.聚乳酸/乳酸接枝改性硅灰石复合材料的拉伸强度和...     

LDPE悬浮聚合接枝PS及其表征

研究了ＬＤＰＥ悬浮接枝ＰＳ合成ＬＤＰＥ－ｇ－ＰＳ接枝共聚物的工艺，此接枝共聚物可作为某些聚合物共混的相容剂。讨论了苯乙烯溶胀ＬＤＰＥ时间、引发剂浓度和ＬＤＰＥ与苯乙烯投料比对接枝率的影响，发现溶胀时间为４ｈ、反应时间为８ｈ、引发剂浓度为１％时、ＬＤＰＥ与苯乙烯投料比为１∶１时，其接枝共聚物接枝率最大可达３８．５％。并对ＬＤＰＥ－ｇ－ＰＳ接枝共聚物进行了ＤＳＣ、ＩＲ及接枝率测定的表征。     

溶液接枝聚合EPDM-g-MS的研究

采用溶液接枝聚合法制备EPDM接枝甲基丙烯酸甲酯(MMA)-苯乙烯(St)共聚物(EPDM-g-MS),研究反应条件对接枝聚合反应的影响.结果表明,反应温度为80 ℃、反应时间为20 h时,EPDM-g-MS的优化制备条件为:过氧化二苯甲酰与反应物(EPDM和MMA-St共单体)质量百分比 1%;反应物质量分数 0.2;甲苯和正庚烷混合溶剂中甲苯体积分数 0.75;EPDM/MMA-St共单体质量比 50/50;MMA与MMA-St共单体质量百分比 85%.在此条件下,接枝体系的单体转化率为80.1%,接枝率为55.1%,接枝效率为69.5%.     

A comparative study on effects of two kinds of polymerization methods on grafting of polymer onto silica surface

In this article we present the result of a comparative study of two kinds of polymerization methods—solution polymerization (sol. poly.) and dispersion polymerization (dis. poly.) for grafting polymer onto silica. As a model for the grafting polymerization reaction, styrene was chosen as the monomer and azo diisobutyronitrile (AIBN) as the initiator. The study aims at supplying theoretical reference for better selecting polymerization method to graft polymer on the silica particle surface. First, monolayers of 3‐methacryloylpropyl trimethoxysilane were chemically bonded onto the surfaces of micrometer‐sized silica gel particles, and so double bonds were immobilized onto the silica surface. Second, the copolymerizations between the immobilized double bonds and the monomer styrene were carried out, homopolymerizations of styrene followed, and finally polystyrene was grafted to the silica surfaces. Two kinds of polymerization methods, sol. poly. and dis. poly., were adopted respectively, and the effects of polymerization methods on grafting process were examined mainly. At the same time, the effects of different polymerization conditions on the grafting degree were researched. It was found that in the dis. poly. system the grafting degree is obviously higher than that in the sol. poly. system under the same polymerization conditions, and the grafting degree can go up to 47%, i.e. 47g/100g. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5808–5817, 2006     

Investigation of acrylonitrile polymerization on the surface of porous microspherical silica gel

The kinetics of acrylonitrile polymerization on the surface of porous microspherical silica gel (PMSS) was studied and some kinetic parameters were determined. The structure of PMSS-based sorbents was analyzed by FTIR-spectroscopy, XRD and sorption analysis before and after microcapsulation with polyacrylonitrile.     

Novel surface ionic imprinting materials prepared via couple grafting of polymer and ionic imprinting on surfaces of silica gel particles

In this paper, a new surface molecular imprinting technique is put forward, and a kind of novel ion-imprinted polymers (IIPs) were prepared through a new approach: firstly functional macromolecule polyethyleneimine (PEI) was grafted onto the surfaces of silica gel particles via the coupling grafting method (“grafting to” method) and the composite material PEI/SiO₂ with chemical linking was formed; secondly the ionic imprinting was carried out towards the macromolecule PEI grafted on the surface of silica particles using Cu²⁺ or Cd²⁺ ion as a template, epichlorohydrin (ECH) as a crosslinking agent and by coordination linkage actions, and Cu²⁺ ion (or Cd²⁺ ion)-imprinted material IIP-PEI/SiO₂ was prepared. The binding characteristics of IIP-PEI/SiO₂ for Cu²⁺ ion (or Cd²⁺ ion) were studied in detail by adopting both static and dynamic methods. The experimental results show that the ion-imprinting material IIP-PEI/SiO₂ has specific recognition ability for the template ions, and this character displays mainly in two aspects: (1) it has high affinity for the template ions, its binding amounts for the template ions are much greater than that of the non-imprinted composite material PEI/SiO₂, and the adsorption capacity enhances nearly two times compared to PEI/SiO₂; (2) it has excellent selectivity for the template ions, for the IIP-PEI/SiO₂ by using Cu²⁺ as template ion, its selectivity coefficients relative to Zn²⁺ and Ni²⁺ are 80.21 and 86.08, respectively, and for the IIP-PEI/SiO₂ by using Cd²⁺ as template ion, its selectivity coefficients relative to Cr³⁺ and Pb²⁺ are 77.05 and 88.22, respectively. Besides, the imprinting material IIP-PEI/SiO₂ has a fine elution property using HCl solution as eluent. The obtained imprinting material by using the new surface molecular imprinting techniques possesses superexcellent binding property for template molecules or ions because of the distribution of imprinted cavities in a thin polymer layer and smaller diffusion barrier.     

Thixotropic interparticle interaction between silica and nonionic polymer particles prepared by static dispersion polymerization

Static dispersion polymerization of styrene, methyl methacrylate, ethyl methacrylate, butyl methacrylate and benzyl methacrylate, initiated by a lipophilic initiator in an aqueous dispersion with unmodified silica particles was investigated. Polymerization of styrene gave a mixed dispersion of silica and monodisperse polystyrene (PS) particles, which was extremely stable compared with the aqueous dispersion of silica particles. The enhanced dispersion stability is due to a thixotropic effect based on weak attractive interparticle interactions between silica and PS particles in aqueous dispersion. An aggregate in which silica particles are surrounded by the smaller PS particles is formed and inhibits flocculation of silica particles, thus giving enhanced dispersion stability. The results of similar static polymerization reactions with methacrylate analogs indicate that hydrogen bonds between benzene ring and hydroxy groups on the silica surface, and not electrostatic interaction derived from initiator residues, are the origin of weak interaction for thixotropic aggregation.     

Grafting polystyrene onto silica nanoparticles via RAFT polymerization

Reversible addition-fragmentation chain transfer (RAFT) polymerization was used to graft polystyrene (PS) onto silica nanoparticles. A novel route was used to prepare the RAFT agent, 2-butyric acid dithiobenzoate (BDB) by substitution of dithiobenzoate magnesium bromide with sodium 2-bromobutyrate under alkali condition in aqueous solution. Epoxy groups were covalently attached to silica nanoparticles by condensation reaction of 3-glycidyloxypropyltrimethoxysilane (GPS) with the hydroxyl on the silica particle surface. RAFT agent functionalized nanoparticles were produced by ring-open reaction of the epoxy group with the carboxyl group of BDB. Then, PS chains with controlled molecular weights and narrow polydispersities (less than 1.1) were grown from the RAFT agent anchored nanoparticle surface. FT-IR, transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) results showed that PS chains grew from silica particles by surface RAFT polymerization.     

Model development for the description of silica particles dispersion in silicone polymer

In order to improve the mechanical characteristics of silicone polymer, silica particulate filler can be dispersed in the continuous phase. During the dispersion process, silicone is adsorbed on the particle surfaces, and at the same time, the particles are submitted to breakage and erosion phenomena, modifying therefore their particle size distribution (PSD). A numerical tool, that can simulate the evolution of the silica PSD in polydimethylsiloxane (PDMS) during dispersion, and allows an a priori knowledge of the evolution of the suspension properties, is developed. The comparison between experimental and calculated PSD as well as process viscosity values is presented.The advantage of such a modelization lies in the prediction of the final product properties, or in the design and optimization of a process for obtaining a desired product. This approach also shows the effect of the particle porosity on the product characteristics evolution during the dispersion process. The influence of parameters such as the filler quantity, the stirring speed or the number of silanols sites on the silica surface is also investigated.     

Experimental tracking of silica dispersion into silicone polymer

This work deals with the experimental tracking of a dispersion of very fine silica particles in PDMS using a new, easily implemented methodology. The dispersion experiments are carried out in an 8-l capacity mixer equipped with a torquemeter. Using a Couette analogy, the torque-rotational speed data can be converted into process viscosity-effective shear rate data. Simultaneously, the Particle Size Distribution (PSD) evolution is followed through Laser Light Scattering measurements on diluted samples. The PSD evolution allowed us to interpret the dispersion process in terms of different mechanisms, such as breaking-up and erosion of aggregates, as well as, in some cases, re-agglomeration (or flocculation) of particles.     

A novel and facile approach for preparing composite core-shell particles by sequentially initiated grafting polymerization

With the commercially available vulcanized acrylonitrile butadiene rubber (NBR) latex as a model, a facile approach for the preparation of composite core-shell particles was developed. As the first step, UV photoreduction followed by cross-linking/coupling reactions with benzophenone (BP) as the photoinitiator and trimethylpropane triacrylate (TMPTA) as the accelerator were carried out in order to attach dormant semi-pinacol groups to the surface of the NBR particles (NBR-SP). The second step, carried out under heating, involved the grafting of styrene (St) which was induced from the particle surface by bond breaking of NBR-SP and propagation towards the center of the particles. The grafting efficiency could be kept at a high level, i.e. approx. 90%, and the grafting yield increased with time (could reach up to 140%). Finally, by adding acrylamide (AM) or N-vinyl pyrrolidone (NVP) as a second monomer under heating, a composite core-shell particle could be prepared.     

Atom transfer radical polymerization from silica nanoparticles using the ‘grafting from’ method and structural study via small-angle neutron scattering

Polymer chains were grafted from silica beads (colloidal sol in dimethylacetamide) by atom transfer radical polymerization (ATRP), via the ‘grafting from’ method. The grafting of the initiator onto the silica surface was done in two steps. First, thiol-functionalization of the surface was achieved via silanization with a mercaptopropyl triethoxysilane. Second, we performed an over-grafting of the surface by reacting the thiol with 2-bromoisobutyryl bromide to generate the halogen-functional ATRP initiator. The nanoparticles were kept in solution (in the same solvent) at each stage of the functionalization (even during the purification steps), as this is the only way to avoid irreversible aggregation. Then, the polymerization of styrene was conducted. Control of both the molecular weight and the density of grafted chains can be achieved by this method. Careful characterization such as gel permeation chromatography, ²⁹Si CP/MAS NMR, elemental analysis, infrared spectroscopy and thermo-gravimetric analysis is performed. The state of dispersion of the grafted nanoparticles is followed in details by small angle neutron scattering and results obtained from this technique are presented here as well as the way the SANS data can be treated. Connection is systematically done between the information provided by this technique and the improvement of the synthetic procedure.     

甲基丙烯酸β-羟乙酯分散聚合过程中粒径变化研究

采用十二烷基硫酸钠和聚乙烯醇为分散剂,偶氮二异丁腈为引发剂,用激光散射粒度分布仪对甲基丙烯酸β-羟乙酯（HEMA）分散均聚合过程中粒径变化进行了分析。结果表明聚合物平均粒径起始变化不大,而后随着反应时间的增加大幅下降,说明在聚合过程中大的粒子凝聚,有新的粒子产生;用强度-粒径分布曲线描述聚合过程中粒径变化表明在HEMA分散聚合过程中有周期性成核现象发生,不断有新粒子产生,直到单体聚合完毕。