Auto-acceleration of radical polymerization rate in polymerization of styrene under the condition of predominant transfer |
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| Institution: | 1. Section of Pharmaceutical Technology, Department of Pharmacy, School of Health Sciences, National and Kapodistrian University of Athens, Athens, Greece;2. Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, Athens, Greece;3. Biomedical Research Foundation, Academy of Athens, Athens, Greece;4. Vaccine Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederic, MD, USA;5. Centre of Polymer and Carbon Materials, Polish Academy of Sciences, Zabrze, Poland;1. Departmento de Alimentos y Biotecnología, Facultad de Química, Universidad Nacional Autónoma de México, 04510, México City, Mexico;2. Department of Chemistry and Biomolecules, Institute of Chemistry, UNAM, Mexico;3. Department of Biochemistry, Faculty of Chemistry, UNAM, Mexico |
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| Abstract: | Styrene was polymerized at 20°C for 252 days in the presence of 2,2′-azobis(isobutyronitrite) azobis(isobutyronitrile) (AIBN). When AIBN]σ = 0.268 mmol l−1, the instantaneous weight-average degree of polymerization (140,000) of the polymer formed is independent of conversion x between 0.05 and 0.60. This independence shows predominant transfer to monomer. Auto-acceleration of polymerization starts at about x = 0.02. In order to explain this auto-acceleration, an equation derived previously for the relationship between termination rate, free volume and volume fraction of polymer is applied to the kinetic data obtained under the condition of predominant transfer to monomer. It is concluded that polymer molecules may move by reptation and the mobility of segments decreases with decreasing free volume. |
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