Poly(methyl methacrylate) (PMMA) and polystyrene (PS)/clay nanocomposites were prepared via in-situ bulk polymerization. The compatibility of the initiator and monomer with the clay surface was found to profoundly affect the clay dispersion. By using a surfactant containing a polymerizable group to modify the clay surface, exfoliated PMMA and PS/clay nanocomposites were synthesized. The clay dispersion was quantified by both X-ray diffraction (XRD) and transmission electron microscopy (TEM). The dimension stability of nanocomposites was studied and related to both nanoscale (layer separation) and mesoscale (long-range distribution) clay dispersion.

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Polymeric nano-composites are prepared by melt intercalation in this study.Nano-clay is mixed with either a polymer or a polymer blend by twin-screw extrusion. The clay-spacing in the composites is measured by X-ray diffraction (XRD). The morphology of the composites and its development during the extrusion process are observed by scanning electron microscopy (SEW. Melt viscosity and mechanical properties of the composites and the blends are also measured. It is found that the clay spacing in the composites is influenced greatly by the type of polymer used. The addition of the nano-clay can greatly increase the viscosity of the polymer when there is a strong interaction between the polymer and the nano-clay. It can also change the morphology and morphology development of nylon 6/PP blends. The mechanical test shows that the presence of 5-10 wt.% nano-clay largely increases the elastic modulus of the composites and blends, while sign& cant& decreases the impact strength. The water absorption of nylon 6 is decreased with the presence of nano-clay. The effect of nano-clay on polymers and polymer blends is also compared with Kaolin clay under the same experimental conditions.

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Experimental investigations aimed at assessing the effectiveness of femtosecond (FS) laser ablation for creating microscale features on electrospun poly(ε-caprolactone) (PCL)/gelatin nanofiber tissue scaffold capable of controlling cell distribution are described. Statistical comparisons of the fiber diameter and surface porosity on laser-machined and as-spun surface were made and results showed that laser ablation did not change the fiber surface morphology. The minimum feature size that could be created on electrospun nanofiber surfaces by direct-write ablation was measured over a range of laser pulse energies. The minimum feature size that could be created was limited only by the pore size of the scaffold surface. The chemical states of PCL/gelatin nanofiber surfaces were measured before and after FS laser machining by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) and showed that laser machining produced no changes in the chemistry of the surface. In vitro, mouse embryonic stem cells (mES cells) were cultured on as-spun surfaces and in laser-machined microwells. Cell densities were found to be statistically indistinguishable after 1 and 2 days of growth. Additionally, confocal microscope imaging confirmed that spreading of mES cells cultured within laser-machined microwells was constrained by the cavity walls, the expected and desired function of these cavities. The geometric constraint caused statistically significant smaller density of cells in microwells after 3 days of growth. It was concluded that FS laser ablation is an effective process for microscale structuring of these electrospun nanofiber tissue scaffold surfaces.