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氧化石墨烯(GO)片的基面和边缘上存在大量的含氧官能团,能很好地分散在水中,因而具有很好的加工性和广阔的应用前景。在较高浓度范围下,GO水分散液中存在着强烈的竞争性相互作用,从而对流变行为产生较大影响。在本文中,通过稳态、动态等流变实验以及理论分析,研究了pH值、温度和不同的有机溶剂对GO分散液流变行为的影响。结果表明,降低pH值、适当增加温度以及加入吡啶均可促进GO水分散液从粘弹性液体到凝胶态的转变。利用DLVO (Deryagin-Landau-Verwey-Overbeek)理论,探讨了GO片之间的范德华作用力以及双电层排斥作用的相互关系,及其对流变性能的影响。通过群体平衡模型(PBE)分析了GO分散液的屈服应力与体积分数的正相关关系。同时,通过蠕变和松弛实验发现,高浓度的GO分散液中结构变化及流变行为在很多方面与高聚物相似,利用Poyting-Thomson模型能较好地拟合其粘弹性行为。上述研究结果为深入研究复杂的GO分散体系提供理论支撑和实验依据。 相似文献
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In this work,surface-relief-grating formation behavior was studied by using two hyperbranched azo polymers.The hyperbranched polymers containing pseudo-stilbene type azo chromophores throughout the hyperbranched structure were synthesized by step-growth polycondensation of AB2 type monomers.The AB2 monomer,4-(4’-(bis(2-chloroethyl)amino)-phenylazo) benzoic acid(BAA),was prepared through azo-coupling reaction between N,N’-bis(2-chloroethyl)aniline and 4- aminobenzenic acid.The another AB2 monomer,4-(4’-(bis(2-chloroethyl)amino)phenylazo)-3-nitro-benzoic acid(BANA), was prepared through azo-coupling reaction between N,N-bis(2-chloroethyl)aniline and 3-nitro-4-aminobenzcnic acid.The hyperbranched polymers(PBAA and PBANA) were prepared through nucleophilic substitution reaction of BAA and BANA, respectively.The polymers synthesized were characterized by using spectroscopic methods and thermal analysis.The photoinduced dichroism and photo-induced surface-relief-grating(SRG) formation of the hyperbranched polymers were investigated upon irradiation with Ar+ laser at 488 nm.PBAA shows typical photoinduced dichroism SRG formation behavior.On the contrary,PBANA does not show the photoresponsive properties.The results indicate that the nitro at the ortho position of azo group of PBANA shows the effect of inhibiting the photoinduced variations.The effect can be attributed to the blockage of the trans-cis isomerization of the azobenzene moieties by the steric hindrance. 相似文献
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研究了支化侧链型偶氮无规共聚物(PMAPB6P-AA)在THF/H2O混合溶液中的自组装行为.研究发现,通过缓慢增加体系的水含量,可以制备出具有中空结构的非球形聚集体.调节聚合物的初始浓度,可以得到不同粒径的聚集体.聚集体中偶氮生色团的光致异构化速率与异构化程度随聚合物初始浓度的增大而减小.在此基础上,采用更加缓慢的增加水含量的方法,使聚合物分子进行充分的疏水聚集与H-聚集,制备出类囊泡状聚集体.在紫外光照射条件下,观察到类囊泡聚集体发生了光致解聚集. 相似文献
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Three epoxy-based azo polymers(PEP-AZ-Cl,PEP-AZ-CN and PEP-AZ-NT) with high chromophore density were synthesized by using post-polymerization azo-coupling reactions between epoxy-based precursor polymer(PEP-AN) and diazonium salts of 4-chloroaniline,4-aminobenzonitrile and 4-nitroaniline,respectively.The structures and properties of the azo polymers were characterized by using ~1H-NMR,FT-IR,UV-Vis and thermal analyses.The photoinduced birefringence of the azo polymers was studied by irradiating spin-coated films of the polymers with laser beam at three different wavelengths(488,532,and 589 nm).The results indicate that the photoinduced birefringence of the azo polymers is related with the electron-withdrawing group on azo chromophores and the excitation wavelength.The excitation wavelength that can cause the efficient responses is determined by the absorption band positions of the azo chromophores,which are mainly affected by the electron-withdrawing group on the chromophores.Therefore,the azo polymers containing chromophores with different electron-withdrawing groups show different responsive behavior to the irradiation light at different wavelengths.When irradiated with 488 nm light,PEP-AZ-Cl shows the shortest time to reach the saturated birefringence but with the lowest saturation birefringence level compared with the other two azo polymers.When irradiated with 532 nm light,PEP-AZ-CN shows the shortest time to reach the saturated birefringence.When irradiated with 532 and 589 nm light,PEP-AZ-NT shows the highest saturation birefringence level. 相似文献
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合成了偶氮单体2-[4-(4′-乙氧基苯基偶氮)苯氧基]乙基丙烯酸酯(EAPEA),利用核磁共振、傅立叶红外和元素分析法对其分子结构进行了表征.利用该单体与异丙基丙烯酰胺共聚得到一种对温度和光敏感的共聚物.共聚物中少量的EAPEA单元能够显著降低聚异丙基丙烯酰胺(PNIPA)的相转变温度.当EAPEA的摩尔含量为2.94%时,相转变温度从PNIPA均聚物的31.8℃下降为22.0℃.在波长为365nm的紫外光照射下,共聚物中的偶氮基团能够从反式构型转变为顺式构型.在紫外光下照30s后,EAPEA摩尔含量为0.98%的聚{异丙基丙烯酰胺-共-2-[4-(4′-乙氧基苯基偶氮)苯氧基]乙基丙烯酸酯}的相转变温度从27.2℃上升到29.3℃. 相似文献
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利用聚电解质逐层浸渍 ( layer- by- layer dipping)法制备自组装膜是最近发展起来的进行表面改性的新方法[1~ 3] .一方面 ,从理论上来说 ,只要是带电荷的聚合物都可以利用该技术制备具有优异性能的自组装膜 ;另一方面 ,还可以通过调节溶液的 p H值和离子强度等控制阴阳离子的组装过程 ,从而控制自组装膜的内部结构和表面形态 ,为在纳米级范围内设计和控制聚合物聚集态内部结构提供了可能性 .近年来 ,具有高度支化结构的超支化分子由于具有独特的物理和化学性能而受到了广泛的关注 [4 ,5] ,但以聚电解质逐层浸渍法制备超支化分子自组装膜… 相似文献
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近年来,偶氮苯类化合物的光学顺反异构现象已引起人们的广泛关注[1~7].在紫外光照射下,偶氮苯由反式结构转变为顺式结构,引起分子的偶极矩发生变化,导致分子的吸收光谱、尺寸及表面能等均发生变化[7].偶氮苯表面能的改变可引起其表面浸润性发生变化.据文献[1~4]报道,偶氮苯膜在紫外光照射前后接触角最大改变了11°.浸润性是固体表面的一个重要特性,主要受固体表面的化学组成和微观几何结构(粗糙度)影响[8~11].通常,与水的接触角大于150°的表面称为超疏水表面;而与水的接触角小于5°的表面称为超亲水表面.本文以2-(4-偶氮苯基苯氧基)丙烯酸… 相似文献
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