共查询到19条相似文献,搜索用时 171 毫秒
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苯乙烯和二乙烯苯共聚体系是典型的不可控制的交联聚合体系,加入天然橡胶后,通过阳离子聚合方法,生成三元共聚物线团,由于橡胶分子链上含有大量的双键,聚合体系中能进行分子内反应,使不可控的交联聚合体系成为可控的交联聚合体系,其链增长不能无限制进行,从而可以合成可溶解的交联的聚苯乙烯-二乙烯苯-天然橡胶聚合物。 相似文献
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聚氯乙烯与丁腈橡胶交联反应的分子模拟 总被引:1,自引:0,他引:1
用分子模拟方法对聚氯乙烯(PVC)与丁腈橡胶(NBR)化学交联机理及交联反应位置进行了研究,通过DMol 3计算反应的自由能、活化能和反应热,进而研究他们对交联反应行为的影响。模拟结果显示:在453K时,过氧化二异丙苯(DCP)能够引发NBR发生夺取α-亚甲基活泼氢的反应和双键的加成反应,产生NBR大分子自由基,进而引发NBR的自交联反应,加成反应的速率要快于夺取α-亚甲基活泼氢的反应速率;DCP能够引发PVC发生脱氢反应,形成PVC大分子自由基进而引发PVC的交联,但不能引发PVC发生脱氯的反应;PVC与NBR能够发生共交联反应;NBR的自交联反应最快,PVC与NBR的共交联反应次之,PVC的自交联反应最慢。 相似文献
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刚性粒子在环氧树脂中的增韧行为研究 总被引:4,自引:0,他引:4
用乳液聚合的方法合成了一系列具有不同交联程度和带环氧官能团的刚性粒子,并将它们作为环氧树脂的增韧改性剂掺到环氧树脂中,研究了界面层结构对增韧的影响。结果表明:不同交联程度的刚性粒子参入到环氧树脂中,由于粒子与基体结构之间发生了不同程度的分子互穿而表现出不同的增韧效果;刚性粒子表面带环氧官能团后,与基本材料形成了化学键合的界面层结构,对粒子的增韧也十分有利。 相似文献
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聚丙烯亚胺树形分子是一种从中心核开始增长,具有确定代数和末端基的高度分支聚合物,可以通过重复反应顺序的逐步合成获得。由于该化合物具有高度的几何对称性、大量的端基、分子内存在空腔等结构特点,在工业、农业、国防、生命科学、医学等领域具有广泛的应用前景。文中通过介绍聚丙烯亚胺树形分子的合成、表征方法及其性能研究,讨论了聚丙烯亚胺树形分子的改性和应用。 相似文献
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采用反应挤出技术制备了以过氧化二异丙苯为引发剂、二乙烯基苯和苯乙烯的混合物为交联剂的交联接枝聚丙烯(PP)改性材料。通过熔体流动速率、动态流变性和差示扫描量热法等测试计算了改性材料的熔体强度、加工流动性和结晶行为,并分析了反应物组分变化对材料结构和行为的影响。研究结果表明,添加适量的过氧化二异丙苯、苯乙烯和二乙烯基苯既不会对材料的凝聚结构及结晶行为造成很大的影响,又都能一定程度提高材料的熔体强度。苯乙烯的加入可以增大交联点之间线型链段的长度,增加PP分子链间交联点分布的均匀性,起到部分替代或充分发挥二乙烯基苯交联剂的效果。 相似文献
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超分子化学自组装的重要研究内容是组装体的分子设计、合成及其组装过程。为了构筑和调控某些具有特殊功能的超分子自组装体,针对不同的应用要求,可引入具有独特光电性质及刚性的有机π-共轭分子作为基本组装单元,通过超分子弱相互作用组装成功能性纳米/微米材料。总结了近年来国内外有机共轭分子的自组装行为,并介绍了其在纳米/微米光波导材料、有机小分子光电器件、分子机器及超分子传感器中的相关应用。 相似文献
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硅烷接枝交联聚乙烯的研究 总被引:26,自引:2,他引:24
用不同结构的乙烯基硅烷与聚乙烯进行熔融接枝及水解缩合交联反应,通过对 支物的结构表征,交联行为以及交联前后结晶性质,高温应力-应变曲线的测定,研究了不同结构的乙烯基硅烷对硅与聚乙烯的接枝反应和交联反应的影响。 相似文献
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以α-溴代苯乙烷(BEB)为引发剂,CuB r/2,2′-联二吡啶(BPY)为催化体系,对二乙烯苯(DVB)进行原子转移自由基聚合(ATRP)原位生成自引发单体合成超支化聚合物进行了研究。用1H-NM R、GPC、M ALLS分别对聚合反应过程和聚合物进行了表征和分析。结果表明,可以由双烯化合物原位生成自引发单体合成超支化聚合物,聚合物分子质量M-n.GPC在104以下,分子质量分布为2~4,表现出较宽的分子质量分布,以光散射法测定的聚合物绝对分子质量M-w.MALLS达105以上。 相似文献
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Polymeric microparticles provide great potentials for applications originated from their high surface area and functionalities and thus have attained many attentions in various fields. Here, we attempt to fabricate polymeric micropowders based on the reversible thermal crosslinking (Diels-Alder reaction). Initially, poly(FEEMA) obtained from the radical polymerization of furan functionalized monomer and partially crosslinked poly(FEEMA) respectively. The physical properties of base-polymer for fabrication of microparticles have changed in order to control thermal responsible property of final micro particles. Based on Diels-Alder reaction, microparticles in the size range of 200 nm–2 μm were successfully prepared using polymer precursors and cross-linker in oil-in-water emulsion. Controlling the molecular weight as well as crosslinked density of polymer precursors makes it possible to adjust the thermal properties (glass transition temperature and retro-Diels-Alder temperature) of the microparticles. These series of method can provide thermal triggered, selective meltdown microparticles for several application fields such as selective gluing, patching, filling or healing by applying external heat. 相似文献
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以交联聚苯乙烯为母体,经过大分子化学反应,在聚合物侧基苯环上引入了具有引发聚合生的过氧酰基。研究了各种条件对过氧酰基含量的影响,并研究了此引发剂引发丙烯酸甲酯的聚合反应。结果证明,当交联度较小时,固载引发剂具有较好的引发活性。 相似文献
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含羟甲基丙烯酰胺共聚物乳液研究 总被引:9,自引:1,他引:8
研究了含羟甲基丙烯酰胺的丙烯酸酯共聚物乳液膜交联后的溶胀度、自交联反应。结果表明,交联共聚物的溶胀度随羟甲基丙烯酰胺含量的增加而降低;共聚物在受热过程中,活性基团之间发生交联反应,产生网状结构。并求得了交联反应的表观活化能。 相似文献
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Harvey Rich Marianne Odlyha Umber Cheema Vivek Mudera Laurent Bozec 《Journal of materials science. Materials in medicine》2014,25(1):11-21
The use of collagen scaffold in tissue engineering is on the rise, as modifications to mechanical properties are becoming more effective in strengthening constructs whilst preserving the natural biocompatibility. The combined technique of plastic compression and cross-linking is known to increase the mechanical strength of the collagen construct. Here, a modified protocol for engineering these collagen constructs is used to bring together a plastic compression method, combined with controlled photochemical crosslinking using riboflavin as a photoinitiator. In order to ascertain the effects of the photochemical crosslinking approach and the impact of the crosslinks created upon the properties of the engineered collagen constructs, the constructs were characterized both at the macroscale and at the fibrillar level. The resulting constructs were found to have a 2.5 fold increase in their Young’s modulus, reaching a value of 650 ± 73 kPa when compared to non-crosslinked control collagen constructs. This value is not yet comparable to that of native tendon, but it proves that combining a crosslinking methodology to collagen tissue engineering may offer a new approach to create stronger, biomimetic constructs. A notable outcome of crosslinking collagen with riboflavin is the collagen’s greater affinity for water; it was demonstrated that riboflavin crosslinked collagen retains water for a longer period of time compared to non-cross-linked control samples. The affinity of the cross-linked collagen to water also resulted in an increase of individual collagen fibrils’ cross-sectional area as function of the crosslinking. These changes in water affinity and fibril morphology induced by the process of crosslinking could indicate that the crosslinked chains created during the photochemical crosslinking process may act as intermolecular hydrophilic nanosprings. These intermolecular nanosprings would be responsible for a change in the fibril morphology to accommodate variable volume of water within the fibril. 相似文献
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Semiconducting Polymer Nanocavities: Porogenic Synthesis,Tunable Host–Guest Interactions,and Enhanced Drug/siRNA Delivery
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Haobin Chen Xiaofeng Fang Yue Jin Xin Hu Min Yin Xiaoju Men Nan Chen Chunhai Fan Daniel T. Chiu Youzhong Wan Changfeng Wu 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(21)
Nanocavities composed of lipids and block polymers have demonstrated great potential in biomedical applications such as sensors, nanoreactors, and delivery vectors. However, it remains a great challenge to produce nanocavities from fluorescent semiconducting polymers owing to their hydrophobic rigid polymer backbones. Here, we describe a facile, yet general strategy that combines photocrosslinking with nanophase separation to fabricate multicolor, water‐dispersible semiconducting polymer nanocavities (PNCs). A photocrosslinkable semiconducting polymer is blended with a porogen such as degradable macromolecule to form compact polymer dots (Pdots). After crosslinking the polymer and removing the porogen, this approach yields semiconducting polymer nanospheres with open cavities that are tunable in diameter. Both small molecules and macromolecules can be loaded in the nanocavities, where molecular size can be differentiated by the efficiency of the energy transfer from host polymer to guest molecules. An anticancer drug doxorubicin (Dox) is loaded into the nanocavities and the intracellular release is monitored in real time by the fluorescence signal. Finally, the efficient delivery of small interfering RNA (siRNA) to silence gene expression without affecting cell viability is demonstrated. The combined features of bright fluorescence, tunable cavity, and efficient drug/siRNA delivery makes these nanostructures promising for biomedical imaging and drug delivery. 相似文献
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用AlCl3、TiCl4、BF3OEt2和CF3SO3H在不同溶剂中引发异戊二烯阳离子聚合反应,结果表明,反应条件对聚合物结构有很大影响。AlCl3引发的聚合反应生成不溶性交联产物和可溶聚合物两部分,后者又包含了环状和线型链(主要是1,4和3,4结构单元)两种主要链节,由CF3SO3H引发的聚合反应只生成可溶性聚合物,聚合物链全部由环状结构组成。TiCl4和BF3OEt2引发的聚合反应受反应介质影响较大,在正己烷中有交联产物生成,可溶性聚合物链包含环状结构和线型链,当用极性的二氯甲烷或用甲苯作反应介质时,交联反应得到完全的抑制,且聚合物链的环状结构分数显著增加。 相似文献
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巯丙基硅烷在硅胶表面组装形成潜在的自由基链转移点,向表面的自由基链转移及表面引发聚合反应可在硅胶表面形成化学键合的聚合物膜,反应过程用红外光谱(FT-IR)、X射线光电子能谱(XPS)、拉曼光谱(Raman)及热重分析(TGA)进行表征。随着巯丙基硅烷修饰硅胶用量的增加,溶液中形成的自由聚合物的分子量及聚合物在硅胶表面的接枝量减小,单体的接枝量随着聚合时间的逐渐增大,直至平衡值。用此方法得到的聚甲基丙烯酸甲酯修饰的硅胶呈现良好的反相色谱性能,对几种含氧芳烃衍生物的保留时间按下列顺序增加:对羟基苯甲酸<α-萘乙酸<β-苯乙醇<苯酚<对羟基苯甲酸甲酯<苯甲酸甲酯<苯甲酸乙酯<苯甲酸丁酯。 相似文献