Technique Boosts Development of Cheaper Materials
Brent D. Johnson
Combinatorial screening has become the method of choice for researchers who test drug candidates in parallel. Advanced by Xiao-Dong Xiang and Peter Schultz at Lawrence Berkeley National Laboratory and the University of California, Berkeley, in 1995, this technique has expanded its applicability into nonpharmaceutical materials, enabling them to be developed faster and more cost-effectively.
To understand how combinatorial chemistry methods can assist in the creation of organic protective coatings for automobiles, Radislav Potyrailo and co-workers from GE Glob-al Research Center and GE Silicones developed a scanning fiber optic CCD-based spectrofluorometer. They combined its operation with fluorescent tags in coatings to decouple the effects of temperature and UV light in the curing of these materials. Their work was published in the Nov. 1 issue of Analytical Chemistry.
Researchers used an experimental setup for high-throughput curing of coating arrays and for fluorescence analysis of how temperature affects the cure rate for UV-curable coatings. Adapted from Analytical Chemistry.
Their technique has several advantages. The measurements are performed without contact, so there is no probe to clean, and the process is completed in microseconds. The high spatial resolution makes even minute imperfections visible.
Curing multiple coatings at once was accomplished in air by periodic exposure of the coatings array to UV/VIS radiation from a portable cure system. A 337.1-nm nitrogen laser excited fluorescence of the incorporated tags. The emission spectra were collected with a fiber optic probe that automatically scanned each coating in the array and that was coupled to a portable spectrofluorometer.
Using this technique, the GE researchers could determine the relationship between the degree of cure and the requisite temperature under pulsed UV-curing conditions. From this they could deduce the optimal temperature range for UV curing.
The use of this combinatorial technique has accelerated at least tenfold the discovery phase in the development of exterior finishes that will provide vehicles with an extra component of protection from sun damage, aggressive solvents and scratches from road gravel and car washes.
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