辐射接枝改性聚合物的研究进展

本文介绍了辐射接枝技术改性聚合物的研究与应用情况，并讨论了辐射接枝过程中的主要影响因素。     

高分子材料表面接枝的方法及应用

介绍了高分子材料表面接枝的方法以及近年来的发展和应用情况。表面接枝方法包括化学接枝、辐射接枝、等离子体接枝、臭氧化接枝和光接枝     

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     

Synthesis of fluorinated polymer electrolyte membranes by radiation grafting and atom transfer radical polymerization techniques

A novel polymer electrolyte membrane was synthesized by radiation-induced grafting and consequent atom transfer radical polymerization (ATRP). First, bromine-containing perfluorinated grafts were prepared by radiation grafting of 2-bromotetrafluoroethyl trifluorovinyl ether (BrTFF) into a poly(ethylene-co-tetrafluoroethylene) (ETFE) film. Then, the bromine atoms in the ETFE-g-PBrTFF grafted films were acted as initiators, and the films were treated with Cu(I)-based catalytic system of a CuBr and 2,2′-bipyridyl (bpy) for the ATRP. By adjusting the molar ratio of initiator/CuBr/bpy and the reaction temperature, branched poly(styrene) with a grafting yield of above 100% on the poly(BrTFF) main chains was constructed in ETFE-g-PBrTFF films. Thermal analysis revealed that the perfluorinated poly(BrTFF) main chains were miscible to ETFE, whereas the hydrocarbon poly(styrene) branches were phase-separated from the ETFE-g-PBrTFF film. Sulfonic groups could be further introduced into the poly(styrene) grafts of ETFE-g-PBrTFF-g-PS films with homogeneous distribution in a perpendicular direction to the membrane surface. The resulting membrane with a styrene grafting yield of 15% exhibited higher proton conductivity than commercial Nafion 117 membrane. Likewise, it had better chemical stability than ETFE-g-PSSA membrane prepared by conventional radiation-induced grafting.     

Polyurethane-poly(methyl methacrylate) interpenetrating polymer networks: 1. Early steps and kinetics of network formation; intersystem grafting

Several side-reactions occurring during the early stages of the formation of polyurethane-poly(methyl methacrylate) interpenetrating polymer networks (PUR/PAc IPNs) have been examined. Thus, the PUR catalyst, stannous octoate, is able to initiate the polymerization of the methacrylic monomers, or to accelerate it in the presence of the proper initiator of the system, azo-bisisobutyronitrile. Nevertheless, this effect does not influence the overall reaction process. On the other hand, light has to be excluded in order to obtain transparent IPNs. The kinetics of formation of the individual networks have been investigated in experimental conditions as close as possible to the actual preparation of the corresponding IPNs. Intersystem grafting, if any, is very limited and its influence on the mechanical properties may therefore be neglected.     

油田含聚污水聚合物降解技术室内实验研究

三次采油技术是油田开发后期稳油增产的主要措施,但随着三次采油技术大规模推广应用,原油脱出污水含聚合物增加,含聚污水处理量也大幅度增加。聚合物的存在造成污水黏度增加、油水分离速度减慢,是造成油田污水处理难度增加的主要原因。因此选择技术经济可行的聚合物降解技术是油田含聚污水处理的关键,通过对几种聚合物降解技术室内模拟实验评价对比,为油田含聚污水处理技术优选提供依据。     

聚合物接枝对脂肪酶活性及稳定性的影响

酶的稳定性和活性一直是困扰其工业应用的主要瓶颈，因此改造酶分子以提升其催化性能是当前研究的重要课题。本工作引入甲基丙烯酸异丁酯(IBMA)和甲基丙烯酸乙酯(EMA)两种疏水性不同的单体分子，通过原子转移自由基聚合分别接枝于褶皱假丝酵母脂肪酶(CRL)表面，合成聚合物接枝脂肪酶pIBMA-g-CRL和pEMA-g-CRL。酶学实验结果显示，聚合物接枝脂肪酶的催化活性和稳定性显著提升。pIBMA-g-CRL和pEMA-g-CRL的催化效率分别达到了野生型CRL的4.39倍和4.68倍。在50℃条件下孵育6 h后，pIBMA-g-CRL和pEMA-g-CRL仍分别保留51%和92%的活性，而野生型CRL的活性则仅剩14%。同样，在pH=9条件下孵育3 h后pIBMA-g-CRL和pEMA-g-CRL能够分别保留52%和83%的活性，并在pH=4~9范围内显示出更好的耐受性。光谱学实验进一步证实了聚合物接枝脂肪酶催化性能的提升与其二级结构和三级结构的变化密切相关。本研究表明，IBMA和EMA的接枝对脂肪酶的稳定性和活性的提升效果显著，是改造脂肪酶的优良材料。     

Electrochemical microscopy of polymer layers

Electrochemical imaging of holes in a polymer layer lying on a metal is demonstrated. Electrochemical imaging has been used to obtain high definition “pictures” of metal/insulator composite surfaces (under aqueous solutions), and porous materials, eg dentine and membranes, [1]. The principle of the method depends on scanning the surface of interest with a microelectrode (the “tip”) which either responds to changes in potential or changes in current as it is scanned [2]. We demonstrate here how the method can be used to image holes in a thin polymer coating on a metal surface.     

Macromolecular and supramolecular chirality: a twist in the polymer tales

Significant advances have been made recently in generating chiral polymer surfaces and materials using a range of methods such as block copolymer self‐assembly, layer‐by‐layer assembly and surface functionalization by polymer brushes. This paves the way for novel chiral materials that can harness and tailor chiral interactions for specific functionalities and properties in a range of biomedical and bioanalytical applications. This paper reviews these advances and speculates on the future of chiral surfaces. © 2013 Society of Chemical Industry     

Electroactive polymer blends

The rapid development of two new classes of electrically active polymer materials, electronically conducting and electroactive polymers and ion-conducting polymers respectively, offers new possibilities for application of both classes of material, especially in combination with each other. While some of these combinations have been attempted before, they all met serious problems due to poor interpenetration of the two polymers. The recent availability of solubilized and soluble electroactive and conductive polymers has greatly advanced the possibilities of reducing the interpenetration problem. Some experimental studies using the combination of solubilized electroactive polypyrrole with poly(ethylene oxide) in an electroactive polymer blend electrode for solid-state polymer batteries are discussed. The opportunities for using polymer blends for solid-state electrochemical polymeric devices, and avenues for the development of materials for such devices, are also reviewed.     

Recent advances in polymer shape memory

Traditional shape memory polymers (SMPs) are those capable of memorizing a temporary shape and recovering to the permanent shape upon heating. Although such a basic concept has been known for half a century, recent progresses have challenged the conventional understanding of the polymer shape memory effect and significantly expanded the practical potential of SMPs. In this article, notable recent advances in the field of SMPs are highlighted. Particular emphasis is placed on how the new developments have changed the conventional view of SMPs, what they mean for practical applications, and where the future opportunities are.     

Schizophrenic copolymer from natural biopolymer by facile grafting

A novel schizophrenic copolymer responsive to pH and temperature change was developed through copolymerization of N-isopropylacrylamide (NIPAm) and acrylic acid (AA) on chitosan chains by a bio-friendly initiator. The behavior of purified graft copolymer in solution phase was studied in detail by NMR, Zetasizer, TEM, SEM and ATR-FTIR techniques. In dilute aqueous media, two types of reversible nanoparticles can be obtained by changing temperature and pH: positively charged micelles with chitosan-shell in acidic solutions above 33 °C and negatively charged micelles with P(NIPAm-co-AA)-shell in alkaline solutions. The transform between these two oppositely charged micelles can be easily controlled by changing pH at human body temperature. The effect of graft degree on the solution behavior was also studied. This novel schizophrenic copolymer has potential applications in drug delivery and other controlled releases.     

Controlled grafting of N-isoproply acrylamide brushes onto self-standing isotactic polypropylene thin films: surface initiated atom transfer radical polymerization

Surface initiated atom transfer radical polymerization (ATRP) technique using CuBr/CuBr₂/bpy complex is employed to graft N-isopropyl acrylamide (NIPAA) brushes onto ‘self-standing’ isotactic polypropylene (iPP) film surface via iPP-Br macro-initiator. The successful accomplishment of surface grafting is understood from the UV-Vis, ATR-FTIR, XPS, SEM analysis and contact angle measurements of the modified samples. The ability to control the degree of grafting of NIPAA brushes reaffirms the elegance of the surface initiated ATRP technique to develop tailor-made polymer surfaces. The LCST nature of the NIPAA brushes would introduce stimuli responsive character onto the surface of the iPP films used for various specialty applications, especially for biomedical purposes.     

Calculating barrier properties of polymer/clay nanocomposites: Effects of clay layers

We analyzed the effects of clay layers on the barrier properties of polymer/clay nanocomposites containing impermeable and oriented clay layers. Using the relative permeability theory in combination with the detour theory, we obtained new relative permeability expressions that allow us to investigate the relative permeability R_p as a function of lateral separation b, layer thickness w, gallery height H, layer length L, and layer volume fraction Φ_s. It was found that intercalated and/or incomplete exfoliated structures and dispersed tactoids with several layers can effectively enhance the barrier properties of the materials. Furthermore, we developed the chain-segment immobility factor to briefly discuss the chain confinement from clay layers. The results showed that the chain confinement enhanced the barrier properties of the intercalated nanocomposites. Our model is better consistent with the experiments when Φ_s>0.01. The findings provide guidelines for tailoring clay layer length, volume fraction and dispersion for fabricating polymer-clay nanocomposite with the unique barrier properties.     

Advanced functional polymer membranes

This feature article provides a comprehensive overview on the development of polymeric membranes having advanced or novel functions in the various membrane separation processes for liquid and gaseous mixtures (gas separation, reverse osmosis, pervaporation, nanofiltration, ultrafiltration, microfiltration) and in other important applications of membranes such as biomaterials, catalysis (including fuel cell systems) or lab-on-chip technologies. Important approaches toward this aim include novel processing technologies of polymers for membranes, the synthesis of novel polymers with well-defined structure as ‘designed’ membrane materials, advanced surface functionalizations of membranes, the use of templates for creating ‘tailored’ barrier or surface structures for membranes and the preparation of composite membranes for the synergistic combination of different functions by different (mainly polymeric) materials. Self-assembly of macromolecular structures is one important concept in all of the routes outlined above. These rather diverse approaches are systematically organized and explained by using many examples from the literature and with a particular emphasis on the research of the author's group(s). The structures and functions of these advanced polymer membranes are evaluated with respect to improved or novel performance, and the potential implications of those developments for the future of membrane technology are discussed.     

Multiple hydrophilic polymer ultra-thin layers covalently anchored to polyethylene films

A novel procedure has been developed to covalently graft multiple hydrophilic polymer ultra-thin layers to functionalized polyethylene surface. Polyethylene films have been functionalized by two methods, chromic acid oxidation and maleic anhydride grafting, to produce surfaces containing reactive groups, carboxylic acid and anhydride, respectively. The reactive groups formed in the functionalization were used to anchor a poly(vinyl alcohol) (PVA) ultra-thin layer by thermal esterification. After anchoring PVA, a second ultra-thin layer, constituted of poly(acrylic acid) (PAA), was also anchored. The second layer was anchored by thermal esterification between PVA hydroxyl groups and PAA carboxylic acid groups. The procedure presented in this work allows the formation of an ultra-thin layer. The macromolecule anchoring reactions occur only at the interfaces, consequently, only the macromolecules in contact with the interface are anchored. The formation of the ultra-thin layer and the surface characteristics have been analyzed through XPS, ATR-FTIR, SEM, and AFM data.     

Polymer adsorption in the grafting reactions of hydroxyl terminal polymers with multi-walled carbon nanotubes

Melt stirring of non-functional polymers such as poly(ethylene oxide) dimethylether (PEO-Me) and polystyrene (PS-H) with multiwalled carbon nanotubes (MWNTs) in the absence of solvent for 48 h induced a substantial amount of polymer adsorption on the MWNTs. The chloroform extraction of the reaction products using centrifugation yielded black colored solutions exhibiting UV absorbance corresponding to the presence of MWNTs. The adsorption of polymer was confirmed on the surfaces of solvent washed residual and recovered MWNTs from the reactions using thermogravimetric analysis (TGA) and FT-IR spectroscopy. Covalent grafting reactions carried out using hydroxyl-terminated PEO-OH and PS-OH with acid chloride containing MWNTs under identical melt stirring condition produced similar results. The presence of polymer on the residual and recovered MWNTs irrespective of the nature of the terminal groups indicates that the adsorption of polymers poses a problem in accurately determining the grafting efficiency. FT IR spectra of the PEO-g-MWNTs shows a substantial shift in CH stretching vibrations indicating a plausible weak intermolecular interaction with π electrons of the MWNTs.     

氰酸酯/聚甲基丙烯酸甲酯互穿聚合物网络的探究

用同步法合成了氰酸酯/聚甲基丙烯酸甲酯(CE/PMMA)互穿聚合物网络(IPN),研究了甲基丙烯酸甲酯(MMA)含量对CE/PMMA-IPN体系力学性能及密度的影响。结果表明CE/PMMA-IPN体系的性能比单一树脂的优异。     

Direct measurement of polymer segment orientation and distortion in shear: semi-dilute solution behavior

The shear induced backbone segment orientation and deformation of the polymeric chromophore diacetylene 4-butoxycarbonylmethylurethane (4BCMU) in semi-dilute solution has been measured with an extended dichroism technique. At low shear rates the random coil, visco-elastic polymer shows orientation in the flow direction. At higher shear rates a reduction in the average conjugation length is observed with an increase in the number of segments orienting perpendicular to the flow direction. Novel behavior, which is not consistent with standard models, is observed for this visco-elastic polymer at high shear rates. The results presented are discussed in view of prior experimental and theoretical work.     

Effects of phase behavior on mutual diffusion at polymer layers interface

Using oscillation mode of rheology and theoretical calculation, we have observed for the first time the crossover of mutual diffusion coefficient, D_m, from high to low temperatures at the multiple layers interface of polymer films. A model which reflects a more realistic terminal state has been proposed to fairly fit the experimental data, by which the mutual diffusion coefficient D_m can be determined. It is substantially found that the diffusion keeps proceeding for the multilayer system at the temperature lower than the critical temperature due to the requirement of a period of time for binodal compositions to reach. Moreover, it is found that the apparent activation energy, E_d, derived from the Arrhenius relation of D_m versus 1/T, increases surprisingly when the welding temperature is below 150 °C, which relates closely to the effects of the phase behavior occurring in the two-phase region of the blend.