Ex Situ Estimation of Dangling Bonds and Polymer Free Radicals

EX SITU ESTIMATION OF DANGLING BONDS AND POLYMER FREE RADICALS 

Free radicals react most efficiently with other free radicals, and the chemicals that have relatively stable free radicals, such as 2,2-diphenyl-1-pricylhydrazyl (DPPH), could be used, in principle, to quantitatively estimate the amount of free radicals (DPPH method). The peroxide formed on the surface that derived from free radical could be quantitatively analyzed by the determination of iodine liberated from KI solution, which could be used to calculate the amount of the original free radical from that peroxide was derived (iodine method). 

It is tempting to use such relatively simple wet chemical methods to determine the amount of free radical on plasma polymers and on polymers treated with glow discharge. However, these methods have serious limitations when applied to the dangling bonds in plasma polymers or polymer free radicals in polymers treated with glow discharge. The most serious limitation is the accessibility of the chemical to the free radicals to be analyzed. Another serious limitation is the specificity of chemical reactions. 

The dangling bonds and polymer free radicals (on the surface of glow discharge treated polymer) capture molecular O2 or H2O, producing hydroxyl and carbonyl groups as schematically shown  

Both methods might be useful to assess the overall reactivity of surfaces and could be used in many areas where the surface reactivity is an important factor. 

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