Pulsed electron beam irradiation of dilute aqueous poly(vinyl methyl ether) solutions |
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Authors: | Thomas Schmidt Ireneusz Janik Piotr Ulański Rudolf Reichelt |
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Affiliation: | a Institute of Physical Chemistry and Electrochemistry, Dresden University of Technology, Mommsenstr. 13, D-01062 Dresden, Germany b Institute of Applied Radiation Chemistry, Technical University of ?ód?, Wróblewskiego 15, 93-590 ?ód?, Poland c Institute for Medical Physics and Biophysics, University of Münster, Robert-Koch-Str. 31, D-48149 Münster, Germany |
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Abstract: | A dilute aqueous solution of the temperature-sensitive polymer, poly(vinyl methyl ether) (PVME), was irradiated by a pulsed electron beam in a closed-loop system. At temperatures, below the lower critical solution temperature (LCST), intramolecular crosslinked macromolecules, nanogels, were formed. With increasing radiation dose D the molecular weights Mw increase, whereas the dimensions (radius of gyration Rg, hydrodynamic radius Rh) of the formed nanogels decrease. The structure of the PVME nanogels was analyzed by field emission scanning electron microscopy (FESEM) and globular structures with d=(10-30) nm were observed. The phase-transition temperature of the nanogels, as determined by cloud point measurements, decreases from Tcr=36 °C (non-irradiated polymer) to Tcr=29 °C (cp=12.5 mM, D=15 kGy), because of the formation of additional crosslinks and an increase in molecular weights. The same behavior was observed for a pre-irradiated PVME (γ-irradiation) with higher molecular weight due to intermolecular crosslinks. After pulsed electron beam irradiation the molecular weight again slightly increases whereas the dimension decreases. Above D=1 kGy the calculated ρ-parameter (ρ=Rg/Rh) is in the range of ρ=0.5-0.6 that corresponds to freely draining globular structures. |
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Keywords: | Poly(vinyl methyl ether) Pulsed electron beam irradiation Nanogels |
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