Papers by Author: Gao Qing Max Lu

Abstract: An improved technique to fabricate PMMA/Ag core-shell nanocomposite via a two-step procedure is reported. The procedure includes an improved particle surface treatment and an improved, subsequent Ag reduction reaction strategy. Well-dispersed PMMA/Ag core-shell nanoparticles with uniform particle size distribution were successfully fabricated using this improved technique. Different functional group treatment on the PMMA particle surface led to an electronically graded transition from the covalent bond of PMMA core to the metallic bond of silver shell. The improved fabrication technique thus allows a highly tailorable size of PMMA core and controllable thickness of Ag shell, which is crucial to producing a tunable plasmon resonance signal to different bio-/chem-environments.

Abstract: Natural clay minerals are ideal nanofillers for polymer materials and have been attracted tremendous research and development interests in the past decade. The manufacture of clay nanofillers relies largely on the exfoliation of clay particle into individual clay platelets. Thus, understanding the interlayer swelling of clay minerals upon the adsorption of surfactants is important to the fabrication and design of polymer nanocomposites. This paper reports our recent experimental and theoretical studies on a variety of organoclays that show a linear relationship between the increase of d-spacing and the mass ratio between organic and clay.

Abstract: Highly ordered rods of large-pore periodic mesoporous organosilica (PMO) were successfully synthesized at low acid concentrations and in the presence of inorganic salt using triblock copolymer P123 as template. The roles of inorganic salt, acidity and temperature in the production of highly ordered mesostructure and the morphology control of PMOs were examined and elucidated. It was found that the addition of inorganic salt can dramatically widen the range of the synthesis parameters to produce highly ordered 2D hexagonal pore structure of p6mm symmetry. However, the uniform rods of PMOs can only be synthesized in a narrow range of acid and salt concentrations, which was sensitive to induction time. The results also showed that the optimized salt concentration (1 M) and low acidity (0.167 M) at 40 oC were beneficial to not only the production of highly ordered mesostucture but also the control of rod-like morphology. Highly ordered rods can also be produced at low temperature (35 oC) with high salt amount (1.5 M) or high temperature (45 oC) with low salt concentration (0.5 M).

Abstract: Polymer nanocomposites are recognized as the next generation of polymer composites due to their exceptional properties. Understanding the molecular origin of the reinforcement mechanism is crucial to the development of such promising materials. This paper reports our recent molecular dynamic study on clay-based polyurethane nanocomposites. The effect of clay platelets on phase separation behavior of polyurethane, at the clay-polyurethane interface, is quantified in terms of molecular interactions, structure and dynamics. The results show that the nanoconfinement of polyurethane chains in clay gallery impedes the development of phase separation commonly observed in bulk polyurethane. The absence of phase separation of intercalated polyurethane is believed to be related to the competitive interactions among clay platelet, polyurethane and surfactant.