在超临界二氧化碳中制备具有微／纳米表面结构的苯乙烯-丁二烯-苯乙烯嵌段共聚物接枝马来酸酐

在超临界CO2中进行了苯乙烯-丁二烯-苯乙烯嵌段共聚物（SBS）与马来酸酐（MAH）的接枝反应,用扫描电子显微镜对接枝共聚物进行了表征。结果表明,控制适当的接枝率,可以分别得到具有皱折型和乳突型的微／纳米表面粗糙结构的接枝共聚物。     

在超临界:氧化碳中制备具有微/纳米表面结构的苯乙烯-丁二烯-苯乙烯嵌段共聚物接枝马来酸酐

在超临界CO2中进行了苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)与马来酸酐(MAH)的接枝反应,用扫描电子显微镜对接枝共聚物进行了表征.结果表明,控制适当的接枝率,可以分别得到具有皱折型和乳突型的微/纳米表面粗糙结构的接枝共聚物.     

氢化苯乙烯-丁二烯-苯乙烯嵌段共聚物研究进展

概述了氢化苯乙烯-丁二烯-苯乙烯嵌段共聚物(SEBS)国内外生产状况,介绍了SEBS生产工艺技术及其加氢催化剂的开发进展,提出应加强SEBS的改性及应用技术开发,在国内尽快实现SEBS的规模化工业生产。     

苯乙烯-丁二烯-苯乙烯嵌段共聚物极性化研究进展

综述了苯乙烯-丁二烯-苯乙烯嵌段共聚物极性化在大分子化学改性和负离子原位聚合改性这两种方法中的研究进展,详细阐述了两种方法的技术手段及优缺点,并对极性化后SBS的应用进行简单概述.     

丁二烯—苯乙烯二嵌段共聚物

以正丁基锂为引发剂 ,环己烷为溶剂 ,THF,2G,TMEDA为极性调节剂 ,合成了丁二烯 -苯乙烯二元共聚物。结果表明,和普通溶聚丁苯橡胶相比 ,该共聚物不仅具有良好的物理机械性能 ,同时具有低滚动阻力和高抗湿滑性能     

坡缕石对苯乙烯-丁二烯-苯乙烯嵌段共聚物改性沥青性能的影响

研究了坡缕石对苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)改性沥青性能的影响.结果表明,坡缕石特殊的层链状结构和大的比表面积不仅改善了SBS改性沥青的低温性能和抗老化性能,同时形成的 .网状结构使SBS改性沥青稳定性增强.     

氢化苯乙烯-丁二烯-苯乙烯嵌段共聚物研究进展

从相态结构、改性及共混等几个角度分别概述了氢化苯乙烯-丁二烯-苯乙烯嵌段共聚物(SEBS)的研究近况，并对SEBS在塑料加工中的应用研究进展作了较详报道。     

苯乙烯-丁二烯-苯乙烯嵌段共聚物的加氢反应及产品性能

讨论了温度和压力在苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)加氢过程中对聚丁二烯链段中乙烯基及顺式-1,4-结构和反式-1,4-结构加氢速率的影响,比较了不同反应器对加氢反应的影响,考察了加氢前后SBS相对分子质量及其分布、动态力学性能、形态及力学性能的变化.结果表明,当反应温度为50～70 ℃和压力大于2.0 MPa...     

相转移催化剂对苯乙烯-丁二烯-苯乙烯嵌段共聚物环氧化反应的影响

研究了三辛基甲基氯化铵(MTAC)、三十二烷基三甲基氯化铵(TMAC)、十六烷基三甲基溴化铵(HTAB)、十八烷基三甲基溴化铵(OTAB)以及聚乙二醇(PEG-400)等5种相转移催化剂对苯乙烯-丁二烯-苯乙烯嵌段共聚物环氧化反应的影响.结果表明,MTAC的环氧化效果最好,当其质量分数为1.0%时,可使环氧化苯乙烯-丁二烯-苯乙烯嵌段共聚物(ESBS)的环氧基质量分数从18.1%提高到20.1%;HTAB和PEG-400有利于ESBS的环氧基质量分数的提高;而OTAB和TMAC由于自身较大的分子体积反而使ESBS的环氧基质量分数下降.傅里叶变换红外光谱分析表明,MTAC可以有效抑制环氧基开环副反应的发生.     

Reinforcement of styrene-butadiene-styrene tri-block copolymer by multi-walled carbon nanotubes via melt mixing

Styrene-butadiene-styrene tri-block copolymer (SBS) was reinforced with multi-walled carbon nanotubes (MWCNTs) by the interaction through melt mixing. The tensile strength of SBS/MWCNT composites increased with increasing MWCNT content. The interactions between SBS and MWCNTs were characterized by solubility of MWCNTs in tetrahydrofuran, dynamic mechanical analysis, X-ray photoelectron microscope, ultraviolet spectra and transmission electron microscopy. The results showed that there were interactions between MWCNTs and SBS occurred during melt mixing, leading to an improvement of the mechanical properties of SBS/MWCNT composites, as well as the homogeneous dispersion of MWCNTs in SBS. The interactions between MWCNTs and SBS were supposed to consist of the π-π interaction between MWCNTs and the phenyl groups of SBS, as well as the chemical bonding of polybutadiene segments with MWCNTs.     

Cross-linking polymerization of acrylic acid in supercritical carbon dioxide

Cross-linking polymerization of acrylic acid in supercritical carbon dioxide (scCO₂) was studied in a batch reactor at 50 °C and 207 bar with either triallyl pentaerythritol ether or tetraallyl pentaerythritol ether as the cross-linker and with 2,2′-azobis(2,4-dimethyl-valeronitrile) as the free radical initiator. All polymers were white, dry, fine powders. Scanning electron microscopy showed that the morphology of the polymer particles was not affected by cross-linking. As the cross-linker concentration was increased, the polymer glass transition temperature first decreased, then increased. Water-soluble and water-insoluble polymers were synthesized by adjusting the cross-linker concentration. Viscosity measurements showed that the polymer thickening effect strongly depended on the degree of cross-linking. Finally, cross-linking polymerization of acrylic acid in scCO₂ was carried out in a continuous stirred tank reactor. The use of cross-linker decreased the monomer conversion in this system.     

聚甲基丙烯酸接枝炭微球

以乙炔为碳源,采用化学气相沉积法,在氩气气氛下,制备了炭微球(CMSs);并用硫酸和高锰酸钾的混合溶液对CMSs进行氧化处理,使其表面引入含氧官能团;然后用KH-570对氧化CMSs进行修饰并将甲基丙烯酸(MAA)接枝于CMSs表面,制得了接枝微粒PMAA/CMSs.用场发射扫描电子显微镜、红外光谱和热重分析对产物的结构和形貌进行了表征和分析.结果表明:采用逐步接枝法成功地将MAA接枝到CMSs表面,为CMSs在聚合物基体中分散、制备功能材料提供了途径.     

Grafting of styrene/maleic anhydride copolymer onto PVDF membrane by supercritical carbon dioxide: Preparation,characterization and biocompatibility

Herein we report the surface modification of poly(vinylidene fluoride) (PVDF) microporous membrane via thermally induced graft copolymerization with maleic anhydride (Man)/styrene (St) in supercritical carbon dioxide (SC CO₂). SC CO₂, as a solvent and carrier agent, could accelerate mass transfer of monomers inside polymer matrixes and then facilitate the graft copolymerization on the surface of the membrane and within membrane pores, which were confirmed by FT-IR/ATR and XPS spectra together with SEM photographs. The effects of SC CO₂ pressure and temperature and the monomer concentration on the graft copolymerization were investigated. The modified PVDF membranes containing from 0 to 7 wt.% of grafted St–Man copolymer (SMA) were prepared and analysed in terms of surface microstructure, composition, hydrophilicity and biocompatibility. Solid-state ¹³C CP/MAS NMR and DSC indicated that the grafted SMA on the PVDF membrane had the alternative sequence structure and formed the different phases in the modified membrane, where the grafted SMA was associated with T_g of 122.8 °C and the PVDF matrix with T_m of 161.2 °C. The static contact angle measurements revealed that remarkable and permanent hydrophilicity was obtained upon grafting SMA. The experiments of BSA adsorption and cell growth also showed that the surface of SMA-based PVDF membrane has excellent biocompatibility.     

Grafting of acrylic acid onto corona-treated polyethylene surfaces

Peroxides formed on the surface by corona treatment of low-density polyethylene film can be used to initiate grafting of polar vinyl monomers such as acrylic acid. Different types of peroxides are probably formed on the surface, but at least hydroperoxides could be detected by XPS analysis. The grafting reaction was carried out directly after corona treatment, by placing the corona-treated film above a solution of acrylic acid heated to 100°C. The grafting reaction takes place in a vapor phase of the monomer. After extracting the reacted films with hot methanol and drying, surface analysis by XPS, IR, and contact angle measurements were carried out. Effect of degree of corona treatment and reaction time have been studied. The conclusion from this work is that acrylic acid in vapor phase can successfully be grafted onto corona-treated polyethylene film by this method. © 1992 John Wiley & Sons, Inc.     

Free‐radical grafting of acrylic acid onto isotactic polypropylene using styrene as a comonomer in supercritical carbon dioxide

Free‐radical grafting of acrylic acid (AAc) onto isotactic polypropylene (iPP) using styrene (St) as a comonomer in supercritical carbon dioxide (SCCO₂) medium was studied. The effects of temperature and pressure of reaction on functionalization degree (grafting degree of AAc) of the products were analyzed. The increase of reaction temperature increases the diffusion of monomers and radicals in the disperse reaction system of SCCO₂. In addition, the increase of temperature accelerates the decomposition rate of 2,2′‐azobisisobutyronitrile (AIBN), thus promoting grafting reaction. It was also observed that functionalization degree of the products decreases with the increase of pressure of SCCO₂ in the range of experiment. The effects of comonomer St on the functionalization degree of the products were investigated. The AAc graft degree of the resulting polymer was drastically higher in the present of St. It reached a maximum when the mass ratio of St and AAc was about 0.7 : 1. Because AAc is not sufficiently reactive toward iPP macroradicals, it would be helpful to use a second monomer that can react with them much faster than AAc. St preferentially reacts with the iPP macroradicals to form more stable styrene macroradicals, which then copolymerize with AAc to form branches. The highest functionalization degree was obtained when the AIBN was 0.75 wt %. When the initiator was used excessively, the functionalization degree decreased because of severe chain degradation of the iPP backbone. The morphologies of pure iPP and grafted iPP are different under the polarizing optical microscope. The diameter of the pure iPP spherulites is 20–38 μ and that of the grafted iPP spherulites is reduced with the increase of the functionalization degree of the products. This is proposed to be because the polar grafts formed during the reaction would have a tendency to associate in the hydrophobic PP environment. This might preserve some of the local crystalline order that existed during the reaction in the swollen iPP phase. It can be proven by a DSC cooling investigation that the crystallization temperature increased as the functionalization degree increased. This is proposed to be because the side‐chain of grafting polymer helps to bring about the heterogeneous nucleation in grafting polymer. Therefore, a large number of nuclei can emerge to a lesser supercooling degree. It can be also proven that the percent crystallization decreased as the functionalization degree increased, probably due to the grafted branches, which disrupted the regularity of the chain structure and increased the spacing between the chains. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2203–2210, 2004     

pH Sensitive polypropylene porous membrane prepared by grafting acrylic acid in supercritical carbon dioxide

pH sensitive membrane was prepared by grafting acrylic acid (AA) on the porous polypropylene (PP) membrane using supercritical (SC) CO₂ as a solvent. The monomer (AA) and the initiator (benzyl peroxide, BPO) were impregnated into the PP substrate with the aid of SC CO₂, and were grafted onto the microporous PP substrate. The grafted membranes were characterized by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), and the water permeability of the virgin and grafted membranes were determined at different pH values. It was demonstrated that the grafting degree (Dg) could be easily controlled by varying operating conditions, such as the monomer concentration, pressure, and temperature during the soaking process. The water permeation of the virgin membrane is nearly independent of pH. However, the water permeation of grafted membranes decreases dramatically with pH as the pH varies from 3 to 6 because the conformation of the PAA changes significantly with the pH of the contacting solution.     

超临界二氧化碳中乙烯基三乙氧基硅烷改性丙烯酸的合成及溶液性质

在超临界二氧化碳介质中,通过自由基沉淀聚合反应合成了一系列不同乙烯基三乙氧基硅烷（VTEOS）、丙烯酸十八酯（ODA）含量的丙烯酸疏水缔合丙烯酸聚合物。采用扫描电镜、红外光谱、滴定法和旋转黏度计对共聚物的形貌、组成及溶液性质进行了表征。实验结果表明共聚物形貌是由直径小于1 μm左右的球形颗粒组成。在疏水单体含量小于1%(mol)时,VTEOS疏水改性聚合物的黏度大于ODA疏水改性聚合物的黏度。在VTEOS含量为0.2%(mol)时,通过硅氧烷间化学反应,硅氧烷改性丙烯酸聚合物溶液黏度达到2400 mPa·s。     

Grafting of acrylonitrile onto styrene-maleic acid copolymer by tetravalent cerium ion

The graft copolymerization of acrylonitrile (AN) onto a styrene-maleic acid copolymer (SY-MAc) with ceric ammonium nitrate (CAN) as a redox initiator in an aqueous medium has been studied. The effects of various reaction parameters, including reaction time and temperature, concentrations of initiator, nitric acid, and monomer, on the grafting yields and the rates of polymerization (R_p), graft copolymerization (R_g), and homopolymerization (R_h) were studied systematically. The results are discussed. The kinetic scheme of free-radical graft copolymerization has been proposed and the equations relating the values of R_p, R_g, and R_h are also suggested. The experimental results are found to be in good agreement with the proposed kinetic scheme. The activation energies of graft copolymerization and total polymerization are calculated. © 1995 John Wiley & Sons, Inc.