Cyclic Olefin copolymers (COC) are a new class of polymers that may prove to be extremely useful in injection molding of micron scale fluidic devices. In microfluidic devices it is desirable to have a hydrophilic surface such as in flow driven by capillary action. However, such hydrophilic surfaces tend to display protein deposition when contacted with blood unlike hydrophobic surfaces. Alternatives to capillary action are then needed to control fluid flow for hydrophobic surfaces. Our goal in this research is to tune the slightly hydrophobic COC surfaces through simple surface modifications that are amenable to injection molding and other processing methods. In this study, the surface of an injection molded microfluidic component made from COC was modified in order to change the surface properties important to bio-fluidic devices. Some of the techniques used in this study were plasma treatments and ASG (aerosol gel) coating. Plasma treatments were conducted by using O2, CF4 and their combination gas. O2 treated surfaces became hydrophilic with increasing time of treatment. Combining O2 and CF4 made the surfaces more hydrophobic compared to CF4 only. The structural changes after the plasma treatments were examined by ATR (Attenuated Total Reflectance) spectroscopy. Titania and silica particles from the ASG process were synthesized from titanium iso-propoxide and tetraethoxysilane, respectively. Titania coated surfaces became more hydrophilic and the silica coated surfaces did not have much change in their surface characteristics. The hydrophobicity of the plastic surfaces was measured by their contact angle with water. The implication of these treatments on bio-fluidic devices and their adaptation to the injection molding process will also be discussed.

Carbon coated silica made by flame synthesis was investigated for reinforcement of styrene-butadiene (SBR) rubber. These composite silica/carbon fillers were examined through small angle x-ray scattering (SAXS), TEM, and AFM showing that these fillers have a rough fractal surface and have fractal aggregate structures. The carbon coated silica fillers were compounded with elastomers and their effect on reinforcement was measured using dynamic mechanical analysis and tensile testing. These fillers were also compared to commercial fumed silica, carbon black, and carbon black/silica composite fillers.

Poly(dimethylsiloxane) (PDMS) networks were prepared by tetrafunctionally endlinking hydroxyl-terminated chains with tetraethoxysilane (TEOS). The resulting networks were filled in-situ by hydrolysis-condensation reactions that were either acid or base catalyzed reactions on some novel precursors. These precursors included star-shaped molecules, rings, linear comb-like chains, and pre-hydrolyzed products of silanes such as TEOS. Both monomethoxy and trimethoxy groups were used as hydrolyzable groups on these molecules. The structures of the resulting composites were examined by small-angle X-ray scattering, and their mechanical properties were determined using equilibrium stress-strain measurements in elongation. Novel precursors with monomethoxy functionalities did not generate stable particulates, but those with trimethoxy functionalities did, with some improvements in mechanical properties. Partially-hydrolyzed TEOS provided the best reinforcement of these PDMS elastomers.

In this study, we described the first results from an x-ray reflectometer which has been modified from an existing Kratky small angle x-ray scattering (SAXS) camera at the UNM/Sandia scattering center. Typically, seven orders of magnitude of reflectivity can be obtained over a range of 0.02 to 0.5 Å−1 in q. This allows the resolution of surface features of 10 to 1000 Å. The conversion to reflectometer is reversible and can be achieved in a short time, allowing for dual use of an existing Kratky camera.

The structure and properties of a series of modified polydimethylsiloxane (PDMS) elastomers reinforced by in situ generated silica particles were investigated. The PDMS elastomer was modified by systematically varying the molecular weight between reactive groups incorporated into the backbone. Tetraethoxysilane (TEOS) and partial hydrolyzate of TEOS were used to generate silica particles. The chemistry and phase structure of the materials were investigated by 29Si magic angle spinning nuclear magnetic resonance (NMR) spectroscopy and swelling experiments.

Silica aerogels have numerous properties which suggest applications such asultra high efficiency thermal insulation. These properties relate directlyto the aerogel's pore size distribution. The micro and meso pore size rangescan be investigated by normal small angle x-ray scattering and possibly,nitrogen adsorption. However, the measurement of larger pores (> 250 Å)is more difficult. Due to their limited mechanical strength, mercuryporosimetry and nitrogen condensation can disrupt the gel structure andelectron microscopy provides only limited large scale structure information.The use of small angle light scattering techniques seems to have promise,the only hurdle is that aerogels exhibit significant multiple scattering.This can be avoided if one observes the gels in the wet stage since thestructure of the aerogel should be very similar to the wet gel (as theresult of supercritical drying). Thus, if one can match the refractiveindex, the morphology can be probed. The combination of certain alcoholicsolvents fit this index matching criteria. Preliminary results for the gelnetwork (micron range) and primary particle structure (nanometer) arereported by using small angle light scattering and ultra-small angle x-rayscattering. The effects on structure over the length scale range of <1 nmto >5 μπι under different conditions (precursors, pH, etc.) arepresented. The change in structure of an aerogel during isostatic compactionto 228 MPa (to simulate drying from wetting solvents) are alsodiscussed.

We have used neutron reflectivity to measure the concentration profile of carboxylic acid-terminated polystyrene at the liquid/solid interface. Two isotopic systems were studied: (1) deuterated polystyrene (DPS) in cyclohexane and (2) polystyrene (PS) in deuterated cyclohexane. Although measured at 24°C (a poor solvent condition), the high grafting density of PS tethered chains causes the chains to weakly stretch to 3-5 times its unperturbed dimension. Although of similar molecular weight, the height of the DPS layer is about 50% higher than that of the PS. In both systems, the volume fraction of polymer near the wall is ∼ 0.60. For the DPS system, reflectivity profiles can be simulated using a parabolic profile with a depletion layer at the silicon-liquid interface. However, in the PS system, no depletion is observed. Here, the shape. of the PS concentration profile is parabolic with a rounded tail.