Graphene-Based Polymer Nanocomposites
Graphene-Based Polymer Nanocomposites
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DOI：
10.1201/b19488-14
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发表时间：
2016-04
影响因子：
3.4
通讯作者：
S. Chatterjee;B. T. T. Chu-B.-T.-T.-Chu-2262873342
中科院分区：
文献类型：
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作者：
S. Chatterjee;B. T. T. Chu-B.-T.-T.-Chu-2262873342
高分子复合材料发展迅速的主要原因是，传统的“纯”聚合物已经在很大程度上发挥了其性能，而技术要求材料具有新的性能和进步。与传统材料（金属、陶瓷、木材、“纯”聚合物等）相比，聚合物复合材料具有许多优势：- 一种独特的性能组合，对于其他单独的材料（强度、应变、热、流变、粘合、电、摩擦、传热等）来说不典型; -通过简单地改变组成和制备条件来控制复合材料性能的能力;-通常，复合材料在单独考虑的性能方面不是“冠军”。但就某些性质的组合而言，它们是不平等的。基于炭黑和碳纳米管的聚合物纳米复合材料已被用于改善聚合物的电、机械、热和气体阻隔性能。石墨烯的发现及其独特的性能组合创造了一类新的聚合物纳米复合材料。石墨烯基纳米复合材料具有独特的机械、气体阻隔、电和介电性能，可用作工程塑料和涂料，并可用作晶体管中的半导体片。本论文旨在探讨石墨烯奈米片作为多功能高分子材料之替代性填充物的潜力。胶乳技术概念包括混合预先制备的聚合物胶乳和剥离的石墨烯的分散体，然后冷冻干燥和压缩成型，应用于石墨烯/聚苯乙烯纳米复合材料的制备。通过以下途径获得的石墨烯用于纳米复合物制备：1）在表面活性剂存在下，在水中借助于水合肼氧化和剥离石墨，随后还原氧化石墨烯; 2）氧化石墨，随后热还原氧化石墨; 3）在表面活性剂存在下，通过长期浴超声处理在水中剥离石墨。找到了通过第一条路线制备石墨烯的最佳时间和温度。通过四点和局部电流测量技术获得的基于这种类型的石墨烯的纳米复合材料的最终电导率揭示了高达15 S/m的有趣的高值，这可以在低纳米填料负载（1.6- 2wt%）下实现。对于所产生的聚苯乙烯/石墨烯纳米复合材料，观察到表现出约0.8-0.9重量%的相当低的值的显著的逾渗阈值。通过原位还原氧化石墨烯制备纳米复合材料。氧化石墨烯的还原发生在压缩成型步骤期间。这种制备方式使我们能够消除耗时的还原步骤，并由于氧化石墨烯的亲水性而易于剥离和分散在水中的能力，使石墨烯片晶在复合膜中均匀分布。由于不完全还原，复合材料的最终电导率为0.1 S/m，尽管逾渗阈值较低，为0.6 wt%。类型2和3的石墨烯用于石墨烯的分散状态对导电石墨烯/聚苯乙烯纳米复合材料的逾渗阈值的影响的实验和理论研究。结果表明，由具有相对低的稳定性和相对低的剥离度的聚苯乙烯胶乳和石墨烯水性分散体制备的石墨烯/聚苯乙烯纳米复合材料比基于具有较大的石墨烯剥离度和较高的分散稳定性的分散体的复合材料表现出较低的逾渗阈值。利用导电聚合物表面活性剂PEDOT：PSS将石墨烯分散在水中。在研究中使用高和低导电PEDOT：PSS胶乳。结果表明，石墨烯本身在这样的系统中的导电性对纳米复合材料的最终导电性具有最小的影响，这表明石墨烯作为PEDOT：PSS的支架而不是有助于复合材料的最终导电性的填料，或者我们处理片晶（石墨烯）和球体（PEDOT：PSS）的随机混合物，其中在低导电性PEDOT：PSS利用的情况下，低导电性球体限制了系统的导电性。制备了基于碳纳米管/PEDOT：PSS分散体和纤维素晶须/PEDOT：PSS分散体的纳米复合材料，并比较了逾渗阈值和极限电导率。该研究表明，导电纳米填料，在这种情况下，碳纳米管，可以用具有相似纵横比的非导电填料代替，几乎不会失去纳米复合材料的导电性能。最有可能的是，增稠纤维素晶须网络将PEDOT：PSS组织成导电网络。
The main reason for the rapid development of polymer composite materials is that the traditional "pure" polymers have largely played out its performance capabilities whereas technology requires materials with new properties and advances. There are a number of advantages polymeric composites have over traditional materials (metals, ceramics, wood, "pure" polymers etc.): - a unique combination of properties, not typical for other individual materials (strength, strain, thermal, rheological, adhesive, electrical, friction, heat transfer, and others); - the ability to control composites properties by simply changing the composition and preparation conditions; Typically, composite materials are not "champions" with respect to separately considered properties. But with respect to the combination of certain properties they have no equal. Polymer nanocomposites based on carbon black and carbon nanotubes have been used for improving electrical, mechanical, thermal and gas barrier properties of polymers. The discovery of graphene with its unique combination of properties has created a new class of polymer nanocomposites. Graphene-based nanocomposites, with unique mechanical, gas barrier, electrical and dielectrical properties, could find use as engineering plastics and coatings, and could play a role as semi-conductive sheets in transistors. This thesis presents a study on the potential of graphene nanosheets as an alternative filler for multi-functional polymeric materials. The latex technology concept consisting of mixing of a preliminary prepared polymer latex and a dispersion of exfoliated graphene followed by freeze-drying and compression molding was applied for the preparation of graphene/polystyrene nanocomposites. Graphene obtained via the following routes was used for the nanocompsites preparation: 1) oxidation and exfoliation of graphite and subsequent reduction of graphene oxide with the aid of hydrazine hydrate in water in the presence of surfactant; 2) oxidation of graphite followed by thermal reduction of graphite oxide; 3) exfoliation of graphite in water by long term bath sonication in the presence of surfactant. Optimum time and temperature were found for obtaining of graphene via the first route. The final conductivities of the nanocomposites based on this type of graphene, obtained by both four point and local current measurement techniques, reveal interestingly high values up to 15 S/m, which can be achieved for low nanofiller loadings (1.6-2 wt%). A pronounced percolation threshold exhibiting a quite low value around 0.8-0.9 wt% was observed for the produced polystyrene/graphene nanocomposites. Nanocomposites via in-situ reduction of graphene oxide were prepared. The reduction of graphene oxide occurred during the compression molding step. This way of preparation allows us to eliminate the time consuming reduction step and gives a homogeneous distribution of graphene platelets in the composite film due to the ability of graphene oxide to be readily exfoliated and dispersed in water because of its hydrophilic nature. Due to incomplete reduction the ultimate conductivity of the composites is 0.1 S/m although the percolation threshold is low, 0.6 wt%. Graphene of types 2 and 3 was used for an experimental and theoretical study of the influence of the state of dispersion of graphene on the percolation threshold of conductive graphene/polystyrene nanocomposites. It was shown that graphene/polystyrene nanocomposites prepared from polystyrene latex and aqueous graphene dispersions with relatively low stability and relatively low degrees of exfoliation exhibit a lower percolation threshold than the composites based on dispersions with larger degree of graphene exfoliation and higher dispersion stability. Conductive polymeric surfactant, PEDOT:PSS, was utilized to disperse graphene in water. Both highly and low conductive PEDOT:PSS latexes were used in the study. It was shown that the conductivity of graphene itself in such a system has a minimal influence on the final conductivity of the nanocomposites which suggests that either graphene works as a scaffold for PEDOT:PSS rather than a filler contributing to the ultimate conductivity of the composites, or we deal with a random mixture of platelets (graphene) and spheres (PEDOT:PSS) where in the case of low-conductive PEDOT:PSS utilization the low conductive spheres limit the conductivity of the system. Nanocomposites based on carbon nanotubes/PEDOT:PSS dispersions and cellulose whiskers/PEDOT:PSS dispersions were prepared and both percolation thresholds and ultimate conductivities were compared. The study revealed that a conductive nanofiller, in this case carbon nanotubes, can be replaced with a non-conductive one with the similar aspect ratio, almost without losing the conductive properties of the nanocomposites. Most probably the percolating cellulose whiskers network organizes the PEDOT:PSS into a conductive network.