Engineering Research Equipment Grant: Low Angle Light Scattering Photometer

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Technical Abstract: By means of this research equipment grant, a low angle light scattering photometer will help provide needed information in a number of research projects. Some of these include: i) Accurate determination of molecular weight and molecular weight distribution of novel photoresist polymers. These polymers are used in the production of integrated circuits on silicon chips and their properties are affected by their molecular weight. Copolymers which undergo chain scission with high yields when bombarded by electrons will be optimized with regard to their structure, molecular weight, and distribution. ii) A study of the compatibility and diffusion in polymer-polymer mixtures. The availability of compatible mixtures should wident the range of the properties and processability of thermoplastics. The effect of the approach to the phase separation curve (by temperature changes) on the interdiffusion of the two polymers is examined. iii) Determination of the interaction parameters of polymers with solvents. In a study of the properties of microgels underway, the low angle light scattering photometer provides information on both molecular weights and interaction parameters that play a major role in the swelling properties of hydrophilic gels. iv) Aggregation of colloidal particles and its relevance to ceramic processing. It is believed that the solid state properties of solution derived materials depend on the state of aggregation in the solution phase. Aggregation kinetics, sol-gel transformation, the effect of composition and polymer additives can all be indirectly monitored by total intensity scattering which complement other techniques being presently pursued. Innovation/Creativity: One of the uses of the photometer is the characterization of new photoresist systems. The aim is to produce new systems with enhanced sensitivity, resolution, and etch resistance without losing the inherent advantages of adhesion, durability, reproducibility, and versatility which poly(methyl methacrylate) (the standard photoresist) has shown over the years. In the area of compatible polymer-polymer mixtures, major efforts are being undertaken in a number of laboratories in the measurements of diffusion coefficients. Very little or no information is being gathered, however, on the size of the diffusing polymer molecules. Complementary total intensity measurements to be obtained with the light scattering photometer will provide important concentrations between size and diffusion coefficient hitherto unavailable. The characterization of polymer-solvent interaction which plays a crucial role in the swelling characteristics of gels and microgels can be readily determined from a Zimm-plot of total intensity scattering. This information is an important ingredient in developing a general framework for the classification of the properties of gels and microgels. Finally in the area of colloidal suspensions, total scattered light intensity is used to monitor the effect of polymer additives on the stability of the suspensions, the deposition of a coating (e.g. silica) on alumina and the sol-gel transformation of alkoxide gels.