Rotational mobility of nitroxyl radicals in polyesters |
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Authors: | Susan C. Gross |
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Abstract: | Rotational mobility of nitroxyl radicals in polyester films was investigated at temperatures from ?180 to +240°C by ESR spin-probe techniques. Evidence obtained indicated that mobility of radicals was related to polymer structure and reflected increased volume made available to the probe molecule by the polymer matrix. A single correlation time, which followed the form τC = τ0 exp {Ea/RT}, was calculated for the temperature range of rapid reorientation (~109 Hz) of nitroxyl radicals. Ea ranged from 5 to 25 kcal/mole for various systems. Uniaxially oriented semicrystalline polymer matrix restricted radical mobility to a greater extent than a semicrystalline biaxially oriented sample. Effective local viscosity encountered by a nitroxyl radical in several polymers was calculated as 9–13 poise. |
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