Effect of microdomain structure on the mechanical behavior of binary blends

The relationship between microphase structure and mechanical response of the binary blends consisting of polystyrene-block-polyisoprene-block-polystyrene copolymer and low molecular weight polystyrene has been investigated. Low molecular weight polystyrene was chosen to obtain uniformly solubilized nano-blends without macrophase separation. The specimens were solution-cast by adding different amounts of homo-polystyrene to acquire different microphase structures. Small angle X-ray scattering(SAXS), transmission electron microscopy(TEM) and atom force microscopy(AFM) have been used to study the microdomain and grain structure. It is observed that the structural changes in d-spacing and grain size on account of different amounts of polystyrene alter the mechanical behavior in both monotonic tensile and cyclic tests. The elastic and the Mullins effects are strongly sensitive to the changes in d-spacing and grain sizes. Moreover, the sample with bi-continuous structure shows the largest tensile strength and Mullins effect. In addition, the Mooneye-Rivlin phenomenological model was used to evaluate and explore the relationship between the polymer topological networks and the rubber elasticity of these styrenic nano-blends.     

对苯二胺功能化还原氧化石墨烯的结构和官能团变化

采用一步水热回流法,选取对苯二胺(PPD)对氧化石墨烯(GO)进行还原与改性处理,制备了功能化还原氧化石墨烯(GOP-X).采用傅里叶变换红外光谱(FTIR)、X射线光电子能谱(XPS)及X射线衍射(XRD)等研究了PPD与GO的反应作用类型及结构变化.结果表明,随着PPD与GO质量比的增加,GOP-X层间距(d值)先增大后减小,GOP-X共轭结构逐渐恢复,与溶剂分子作用时,层间距增幅呈减小趋势,并最终趋于恒定.PPD单体与GO反应时存在3种键合类型:(1)GO含氧官能团和PPD分子之间的氢键作用(C—OH…H2N—X);(2)质子化PPD与弱酸性GO带负电位置之间的离子键作用(—COO-H3+N—X);(3)PPD中氨基(NH2)与GO含氧官能团之间形成的共价键作用.与GO中羧基(COOH)的酰胺化反应将先于与环氧基(C—O—C)的亲核取代反应.提出了相应的作用机理.