共查询到19条相似文献,搜索用时 171 毫秒
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探索了聚乙二醇双丙烯酸酯在超临界二氧化碳中发生光聚合反应制备聚合物颗粒的过程.方法为向充满超临界二氧化碳的高压反应釜中,同时喷射二氧化碳与聚乙二醇双丙烯酸酯及光引发剂的溶液,溶液与二氧化碳形成均匀的喷雾并进一步通过反溶剂作用与超临界二氧化碳形成分散体系,当同步进行紫外光照射时,单体可以在超临界二氧化碳中发生光聚合.结果证明此方法是可行的,得到了聚合物微颗粒.研究了不同溶剂及反应原料用量对产物粒径分布的影响.采用不同溶剂,将改变反应原料及产物在超临界二氧化碳中的溶解度,进而改变产物的粒径分布;反应原料用量增加,其在超临界二氧化碳中的溶解度减小,导致产物粒径分布较宽。 相似文献
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超临界二氧化碳中药物控制释放体系的一步法制备研究 总被引:1,自引:0,他引:1
用一步法首次制备了以N-异丙基丙烯酰胺类共聚物为基料的药物释放体系。在此法中,超临界二氧化碳同时作为聚合介质和渗透试剂。制得的聚合物微球用扫描电镜、差示扫描量热仪、透射电镜、X射线衍射仪等进行了表征,并用体外释放模拟考察了原位法制备的微凝胶对渗入的目标药物布洛芬的释放效果。 相似文献
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采用分散聚合和无皂乳液聚合的方法,我们制备了粒径不同的交联聚合物微球。通过改变超临界二氧化碳的压力、处理微球的时间以及实验的温度,我们可以实现对这些微球塑化程度的调节。研究发现,随着超临界二氧化碳压力的升高,其对聚合物微球的塑化能力呈现出先增强后降低的趋势。文中我们对这种现象出现的机理也进行了相应的讨论。随着体系温度的升高或者延长处理微球的时间,超临界二氧化碳对两种微球的塑化能力都呈增强趋势。由于乳液聚合得到的聚合物的分子量通常会比分散聚合得到的聚合物的分子量大,因此在相同的条件下超临界二氧化碳对分散聚合法制备的微球塑化能力更强。 相似文献
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以超高分子量聚乙烯作为原料, 在超临界二氧化碳中通过热处理成功制备了聚合物微米球. 微球尺寸符合高斯分布, 并可以控制在较窄范围内, 微球表面多孔且内部中空. 微球的形成是恒温过程和超临界二氧化碳双重作用的结果. 降温过程导致聚合物溶解度降低, 超高分子量聚乙烯分子链析出结晶而形成微球, 内部包裹了少量二氧化碳; 温度进一步降低导致微球内外压力不平衡, 二氧化碳从空心球内部释放形成表面孔洞. 恒温结晶过程除了促使微球结晶度进一步提高外, 还可以使亚稳晶型单斜晶转化为稳定的正交晶. 相似文献
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超临界二氧化碳制备聚合物微孔膜的研究进展 总被引:1,自引:0,他引:1
超临界二氧化碳做非溶剂制备聚合物微孔膜是一个新的研究热点,具有传质系数高、聚合物膜干燥速度快且不破坏结构、溶剂容易回收、CO2可循环使用、CO2的低毒性与环境友好性等特点.本文介绍采用超临界CO2制备聚合物微孔膜的热力学及动力学原理,重点介绍近年来采用此技术制备微孔膜的研究成果,如以聚苯乙烯(PS)、聚丙烯腈(PAN)、聚醚砜(PES)等为基体的微孔聚合物膜. 相似文献
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近年来,超临界二氧化碳(sc-CO2)在聚合反应中的应用受到了越来越多的关注。本文主要综述了以sc-CO2为反应介质的自由基聚合、阳离子聚合、过渡金属催化聚合、热致开环聚合、溶胶-凝胶聚合以及氧化耦合聚合的研究概况。一系列研究结果表明sc-CO2是非常有前途的反应溶剂,在高分子合成领域将会有更加广阔的应用前景。 相似文献
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New silicone‐containing polymers with crosslinkable units have been synthesized by hydrosilation polymerization in both toluene and supercritical carbon dioxide (70°C, 3000 psi) catalyzed by platinum‐divinyltetramethyldisiloxane (Pt‐DVTMS). It was found that high molecular polymers were obtained in both toluene and supercritical carbon dioxide. The polymers were characterized by FTIR, NMR, GPC, TGA, and DSC. The molecular weights of these polymers ranged from 9000 to 39,000. With further hydrolysis and thermal curing, the molecular weight can be increased significantly. Comparison of the properties between reactions in toluene versus supercritical carbon dioxide indicated that the green solvent is a usable alternative for hydrosilation polymerization. The new polymers synthesized in either toluene or supercritical carbon dioxide are thermally stable, ranged from 350 to 488°C. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Joseph Desimone 《Macromolecular Symposia》1995,98(1):795-795
Fluoropolymers are used in many technologically demanding applications because of their balance of high-performance properties. A significant impediment to the synthesis of variants of commercially available amorphous fluoropolymers is their general insolubility in most solvents except chlorofluorocarbons (CFCs). The environmental concerns about CFCs can be circumvented by preparing these technologically important materials in supercritical fluids (SCFs). The homogeneous solution homo- and copolymerization of highly fluorinated acrylic, styrenic and olefinic monomers in supercritical carbon dioxide using free radical methods will be discussed [Science, 257 , 945 (1992)]. Detailed decomposition rates and efficiency factors will be presented for azobisisobutyronitrile (AIBN) in supercritical carbon dioxide and will be compared to conventional liquid solvents [Macromolecules, 26 , 2663 (1993)]. Additionally, viscosities of polymer solutions in supercritical CO2 have been measured using a high pressure, falling cylinder viscometer. The results show that the polymer solution viscosities in supercritical CO2 are an order of magnitude lower than with the same polymers in conventional organic solvents. The results from these homogeneous solution polymerization studies has allowed us to also consider heterogeneous polymerizations in a carbon dioxide continuous phase. Conventional emulsion polymerizations of unsaturated monomers are performed in either aqueous or organic dispersion media with addition of surface active agents (surfactants) to stabilize the colloidal dispersion that forms. With free radical initiators that are preferentially soluble in the continuous phase, high rates of polymerization and high molar mass polymers can be obtained simultaneously. Herein we describe an environmentally responsible alternative to aqueous and organic dispersing media for emulsion polymerizations which utilizes supercritical carbon dioxide, in conjunction with molecularly engineered free radical initiators and amphiphilic molecules that are specifically designed to be interfacially active in CO2. Conventional lipophilic monomers, exemplified by methyl methacrylate and styrene, can be polymerized heterogeneously using a fluorinated azo-initiator in supercritical CO2 in the presence of added surfactant to form stable emulsions that result in submicron size particles. Detailed surfactant and initiator syntheses and phase behavior will also be discussed. 相似文献
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Bungo Ochiai Yugo Hatano Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2009,47(12):3170-3176
The radical polymerization of glycidyl methacrylate (GMA) was conducted under a carbon dioxide atmosphere (1 atm) in the presence of catalysts for the reaction of carbon dioxide and the oxirane group to afford the five‐membered cyclic carbonate group. The degrees of the carbon dioxide fixation depended on catalysts, concentration, and solvents. In solution reaction, the slower polymerizations resulted in faster carbon dioxide fixation, due to the faster carbon dioxide fixation to GMA than to oxirane moieties in polymers. When the polymerization was conducted in 1,4‐dioxane, which is a good solvent for polyGMA but a poor solvent for the analogous polymer bearing cyclic carbonate moieties, the resulting polymers were precipitated out as the progress of the polymerization and the carbon dioxide fixation. As a result, polymers could be isolated by simple filtration and rinsing with methanol. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3170–3176, 2009 相似文献
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A novel strategy to synthesize hybrid metal–polymer nanocomposites has been achieved based on in situ free radical suspension and bulk polymerization techniques. An organometallic precursor complex is dissolved in a liquid monomer phase prior to polymerization, where upon the precursor molecules are immobilized inside the polymer matrix during its formation. In a separate step, metal nanoparticles are then formed by H2-assisted reduction of the precursor in the polymer product in supercritical carbon dioxide (scCO2). The synthesized nanocomposites were characterized by GPC, TGA, SEM and TEM. It is shown that the metal nanoparticles are uniformly distributed inside the polymer matrix and the inclusion of the metal precursor has no significant influence on the polymerization process. The current work represents a simple and universal way to prepare a variety of metal–polymer nanocomposite functional materials. 相似文献
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Tao Liu Joseph M. DeSimone George W. Roberts 《Journal of polymer science. Part A, Polymer chemistry》2005,43(12):2546-2555
The precipitation polymerization of acrylic acid in supercritical carbon dioxide was studied in a continuous stirred tank reactor with 2,2′‐azobis(2,4‐dimethylvaleronitrile) as the free‐radical initiator. The reactor temperature was between 50 and 90 °C, the pressure was 207 bar, and the average residence time was between 12 and 40 min. The product polymer was a white, dry, fine powder that dissolved in water. A wide range of polymer molecular weights (5–200 kg/mol) was obtained. The effects of the operating variables on the polymerization rate and on the polymer molecular weight were evaluated. The observed kinetics suggested that polymerization took place in both the supercritical fluid and the precipitated polymer particles. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2546–2555, 2005 相似文献
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Inga A. Ronova Lev N. Nikitin Ekaterina A. Sokolova Irina Bacosca Ion Sava Maria Bruma 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(10):929-936
Two series of polyheteroarylenes have been investigated with regard to their physical properties before and after swelling with supercritical carbon dioxide. The study of the dependence of glass transition temperature and free volume of polymers on their conformational rigidity showed that the process of swelling in supercritical carbon dioxide is influenced by the voluminous side groups and by the high boiling solvent N-methylpyrolidinone used for the preparation of the polymers which facilitates the formation of crosslinks or complexes with the macromolecular chains. 相似文献