“Vanishing” structural effects of temperature in polymer glasses close to the glass-transition temperature |
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| Affiliation: | 1. N.N. Semenov Institute of Chemical Physics Russian Academy of Sciencees, 4 Kosygin st., 119991 Moscow, Russia;2. High Energy Accelerator Research Organization KEK, Tsukuba 305-0801, Japan;3. A.V. Topchiev Institute of Petrochemical Synthesis Russian Academy of Sciences, 29 Leninskii pr., 117912 Moscow, Russia;1. Department of Chemistry, Faculty of Science, University of Maragheh, Maragheh 55181-83111, Iran;2. Department of Chemistry, Catalysis Division, University of Isfahan, Isfahan 81746-73441, Iran;1. School of Chemistry and Chemical Engineering, University of South China, Hengyang 421001, China;2. Department of Clinical Laboratory, The First Affiliated Hospital of University of South China, Hengyang 421001, China;1. Institute of Bioanalytical Chemistry, Campus B2.2, Saarland University, 66123 Saarbrücken, Germany;2. INM-Leibniz Institute for New Materials, Campus D2.2, 66123 Saarbrücken, Germany |
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| Abstract: | Positron annihilation lifetime (PAL) measurements were used for observation of structural effects of temperature in polystyrene (PS), super-cross-linked polystyrene networks (CPS), and in polyimides (PI) below and in the vicinity of glass-transition temperature Tg. “Vanishing” of these structural effects in the repeating cycles of the temperature controlled PAL experiments due to the slow relaxation processes in different conditions and details of chemical structure is demonstrated. Obtained results illustrate complex, dependent on thermal history, inhomogeneous character of the glass structure. In fact, structure of some polymer glasses is changing continuously. Calculations of the number density of free volume holes in these conditions are discussed. |
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