【作者】 仇伟；

【导师】 马利；

【作者基本信息】 重庆大学 ， 材料科学与工程， 2014， 博士

【摘要】 聚苯胺及其复合材料的微观结构、形貌及尺寸对其物理化学性能有着巨大的影响，使得其微/纳米结构的形貌调控研究引起了人们的广泛关注。因此设计和合成形貌可控的微/纳米结构聚苯胺及其复合材料已成为当前材料科学家研究的热点。本论文借助乙二醇反应介质的辅助，通过简单的化学聚合方法，制备了聚苯胺纳米纤维和纳米棒；并利用化学一步合成方法，合成了聚苯胺/纳米金复合纳米纤维和纳米球，以及聚苯胺/花状纳米金形貌复合材料，分析了反应条件与形貌结构间的关系，提出了其形成机理。主要结果如下：首先，分别以APS和H2O2为引发剂，在无模板条件下，利用化学聚合法制备出了尺寸和形貌可控的的聚苯胺纳米纤维和纳米棒。该材料可轻易地分散于水、乙醇等极性溶剂形成稳定的聚苯胺纳米胶体分散液。对其形成机理的研究发现：乙二醇与苯胺单体和聚苯胺间存在的强烈氢键，是导致聚苯胺一维取向生长的主要因素。其反应条件对产品的形貌、尺寸和性能具有明显的影响。随着温度的升高，一维纳米结构聚苯胺的纵横比和电导率减小，而产率增大。当H2O2与苯胺单体的摩尔比为2，APS与苯胺单体的摩尔比为1时，产品具有最佳的导电性能。此外，聚苯胺纳米纤维（APS为氧化剂）的电导率和形貌与掺杂酸的浓度和种类有明显的关系，掺杂酸浓度的增加，有利于电导率和产率的提高，而当用有机功能酸CSA为掺杂剂时却不能获得聚苯胺纳米纤维形貌。通过比较发现搅拌的存在，有利于产品氧化度、掺杂水平、电导率和产率的提高。其次，在乙二醇溶液中，通过化学一步合成法合成了一维形貌的聚苯胺/纳米金复合材料。结果表明，反应温度和氧化剂浓度对复合材料的形貌、纳米金粒径及分布均有很大的影响。随着温度的升高，聚苯胺纤维的长度增加，纤维直径和纳米金的粒径减小。电化学实验表明，反应温度为10℃时，复合材料具有更好的导电性和电活性，而纳米金也具有较好的分布。复合材料的长度及纳米金的粒径随氧化剂浓度的提高而增大，但纤维的直径却减小。当氧化剂与苯胺单体的摩尔比为1:5时，产物中同时存在聚苯胺/纳米金复合纤维和微米级的复合球。此外，当H2O2存在时，有利于纳米金粒径和分布均匀性的提高，从而获得了高均匀的聚苯胺/纳米金复合纤维。最后，以硫酸代替盐酸作为掺杂剂，在H2O2存在下，采用化学一步合成法制备了聚苯胺/花状纳米金复合材料。通过实验证实了盐酸中的氯离子对氯金酸的氧化还原反应有抑制作用，而硫酸根离子由于没有抑制作用，使反应速度更快，从而导致复合材料从一维形貌转变为聚苯胺/花状纳米金形貌。随后发现，不仅硫酸可以改变反应速度，而且双氧水也对反应速率产生影响。因此，当反应中无H2O2存在，且降低反应温度，获得了形貌和尺寸可控的聚苯胺/纳米金复合纳米球。对其形成机理的研究表明初形成纳米金或聚苯胺/纳米金复合颗粒间的不断聚集生长，以及Au3+在裸露金表面的不断还原是形成复合球形貌的主要原因。复合球的直径随氧化剂浓度的增大而减小，形成表面突枝更均匀的“刺球”形貌复合球。然而，当氧化剂过量时，却只能形成纳米金粒径只有5nm的聚苯胺/纳米金复合纤维。研究发现，搅拌的存在，对复合球的直径没有太大的影响，却有利于聚苯胺/纳米金复合球表面光滑度的提高。更多还原

【Abstract】 The research on morphological control of micro/nanostructured polyaniline(PANI) and its composite have caused extensive attentions due to the huge impact ofmicrostructure, morphology and size on their physical and chemical porperties.Therefore, controllable design andsynthesis of micro/nanostructured PANI materialsand its composites have become a new hotspot of material scientificresearches.In thiswork, the PANI nanofibers and nanorods have been prepared via a simple chemicalpolymerization reaction of aniline with oxidant carried out in ethylene glycol (EG)medium. The polyaniline/gold nanoparticles (PANI/AuNPs) composite with differentmorphology such as nanofibers, nanospheres and nanoflowers also have been perparedthrough an one-step chemical synthesized method withthe assistance of EGmedium.The relationship between reaction conditions and structures or morphology ofmaterials is analyzed, and the formation mechanisms of nanostructuresarepresented.The main contents are as follow:Firstly, the PANI nanofibers and nanorods with controlled size and morphologyare preapredby the chemical methodin the absences of any templates using ammoniumpersulfate (APS) and hydrogen peroxide (H2O2) as the initiator, respectively. Thismaterialcan be facilely dispersed in a polar solvent such as water or ethanol to formsteadyPANI colloids.Mechanism investigations demonstrate that the existence ofstrong hydrogen bonds between EG and aniline or PANI is the main factor leading tothe one-dimensional orientational growth of PANI. The reaction conditionssignificantly impactthe morphology, size, and performance of PANI.The aspect ratioand conductivity of one-dimensional PANIis decreasedwith the rise of temperature,while the yield is increased.When the mole ratio ofH2O2to aniline is two and APS toaniline is one, respectively, the conductivity of PANI is the best. In addition, theconductivity and morphology of PANI nanofibers can be impacted by theconcentration and type of doping acid, in which the higher concentration of acid isbeneficial for the enhancement of the conductivity and yield, but the PANI nanofibersare unable to obtain when the CSA organic functional acid is used as the doped agent.Itcan be found by comparison that the presence of stirring can improve the doping level,conductivity, degree of oxidation and yield of PANI.Secondly, the one-dimensional morphological PANI/AuNPs composites are prepared by one-step chemical synthesized method in EG solution.The results indicatethat the reaction temperature and oxidant concentration have great influence on themorphologyof composites, and size and distribution of gold nanoparticles. As thetemperature increases, the length of PANI fibers is increased, but the diameter of fiberand size of gold nanoparticle is decreased.The electrochemical experiments show thatthe conductivity and electrical activity of composite as well as the distribution of goldnanoparticles are better when the reaction temperature is10℃.On theother hand, thelength of composite fibers and the diameter of gold nanoparticles is increased with theincreasing concentration of oxidant, but the diameter of fibers is reduced. When themole ratio of oxidant to aniline is1:5, the PANI/AuNPscomposite fibers andmicrospheres both can be observed in the product.In addition, the uniformity of sizeand distribution of gold nanoparticles embedded in the PANI can be improved byintroduction of H2O2, and resulting in the formation of PANI/AuNPs composite fibers.Finally, the PANI/AuNPs flower-shaped composites are also prepared by one-stepchemical synthesized method using sulfuric acid (H2SO4) instead of hydrochloric acid(HCl) as a dopant in the presence of H2O2.The experiments confirm that the chlorideions which come from HCl can inhibit the redox reaction of HAuCl4with aniline, butthe H2SO4is used as dopant can improve the redox reaction speed due to the absenceof chloride ion, which leads to the morphological change of PANI/AuNPs compositesfrom one-dimensional to flower-shaped nanostructure.Subsequently, it is found that theabesence of H2O2also can impact the reaction rate. Therefore, the PANI/AuNPscomposite nanospheres are synthesized in the absence of H2O2at alower temperatuer.Mechanism investigations demonstrate that the continuousaggregated growthofpreformed gold or PANI/AuNPs composite particles and the constantly reduction ofAu3+on bare gold surface are major factors for the formation of compositenanospheres.With the concentration of HAuCl4increase, the diameter of compositenanospheres is decreased and the formation of “thorn sphere” shaped compositespheres with more uniform protruding branches is observed. However, when theoxidant is excess, only the PANI/AuNPs composite fibers are formed, in which the sizeof gold nanoparticles is about5nm. The experimental results indicate thatthe presenceof agitation is beneficial for improving the surface smoothness of compositenanosphere, but not significant effect on their diameter.更多还原