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Molecular Dynamics in Poly( N ‐vinylpyrrolidone)‐Poly(ethylene glycol) Blends Investigated by the Pulsed‐Field Gradient NMR Method: Effects of Aging, Hydration and PEG Chain Length
Author(s) -
Vartapetian Ruben Sh.,
Khozina Elena V.,
Kärger Jörg,
Geschke Dieter,
Rittig Frank,
Feldstein Michail M.,
Chalykh Anatoly E.
Publication year - 2001
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/1521-3935(20010801)202:12<2648::aid-macp2648>3.0.co;2-l
Subject(s) - peg ratio , ethylene glycol , polymer chemistry , pulsed field gradient , chemical engineering , diffusion , chemistry , molecule , ethylene oxide , materials science , polymer , organic chemistry , copolymer , thermodynamics , physics , finance , engineering , economics
The self‐diffusion in PVP‐PEG blends has been studied as a function of PEG molecular weight, water content and temperature. The blend corresponding to a stoichiometric PVP‐PEG complex with 36 wt.‐% PEG400 results from hydrogen bonding of the PEG terminal hydroxyl groups to the carbonyls of the PVP repeating units. Changes in diffusion parameters during the time of storage of the samples up to 1.5–2 months after preparation have been established. The attainment of an equilibrium value is characterized by a redistribution of the PEG molecules bonded to the comparatively long PVP chains, resulting in the formation of a supramolecular network. The spin echo attenuation, S inc ( q, t d ), has been found to depend on the temperature, PEG chain length and water content. Water acts as a mediator in the complex formation, accelerating the PVP‐PEG complexation. The PVP blend with PEG200 retains about 21 wt.‐% of water after evacuation at 378 K. This amount of water is believed to be incorporated into the network. The longer the PEG chain length, i.e. the larger the flexibility of the chain, and the lower the OH group concentration in the blend, the smaller the number of PEG molecules bound to PVP. This has been established by comparing diffusion parameters of PVP blends containing PEG400 and PEG600, respectively.