报告人：Prof. John Texter
时间：2月22日（周三）上午 9: 30
地点：图书馆中心会议室
报告内容：Solvent-free nanofluids obtained by autocondensation of organo-trialkoxysilanes on nanoparticle (core) templates and surface decorated with both ionic liquid organic salt groups and with various reactive groups are exotic cross-linking agents that define new types of resins and nanocomposite materials. Such agents can be used to counter embrittlement provided by nanofillers while increasing toughness. We show that such materials can be used to produce thin films including UV protective clearcoats and an interesting new family of adhesives/sealants. Such reactive “inks” provide building blocks for additive micron scale additive printing (manufacturing) and for designing new soft materials. We also show that auto-condensation of such organoalkoxysilanes, followed by suitable anion exchange, produces solvent-free nanofluids that exhibit classical liquid properties with some distinct differences. We observe heat capacity anomalies manifested as lambda transitions in excess heat capacity centered around a glass transition (Tg) and around a freezing transition. The existence of such a connection or coincidence has undergone decades of theoretical conjecture. The second anomaly spanning the melting/freezing range is the first reported excess enthalpy ever reported for an experimental particulate fluid undergoing a phase transition. The integral enthalpy from these lambda transitions is quantitatively accounted for by the gain of specific surface area of the particles, and the associated surface free energy, upon freezing and upon cooling beneath the glass transition temperature. This system also is the first experimental particle system reported that exhibits multiphase coexistence that otherwise is frustrated from crystallizing due to polydispersity. This new material and cousins to be similarly derived promise to become useful in developing soft-sphere potentials in the thermodynamics of polymeric liquids.