Author/Editor		Kristl, J; Lahajnar, G; Jezernik, K; Šmid-Korbar, J
Title		Water behaviour in poly(methylmethacrylate) hydrocolloids studied by NMR techniques and electron microscopy
Type		članek
Source		S.T.P. Pharma Sciences
Vol. and No.		Letnik 2, št. 3
Publication year		1992
Volume		str. 265-9
Language		eng
Abstract		A proton NMR relaxation and pulsed field gradient translational diffusion study of water in poly(sodium methylmethacrylate) (PMMA, Na) hydrocolloids was performed with special emphasis to get a better insight into the structure and dynamics of water. Hydrocolloids of PMMA, Na display a precise structural order. Compared with the case of pure water, the NMR relaxation and diffusion properties of water in the hydrocolloids are modified. The proton relaxation times T1 and T2, was well as the translational diffusion coefficent of water, are found to decrease with increasing polymer concentration. This is easy to explain in terms of the fast exchaange of the water molecules between the free state in the bulk water and the nound state of water molecules at the polymer surface. The relaxation rate (1/T 1b or 1/t 2b) at the polymer surface is much higher than in the bulk free water. So, the effective measured relaxation rates, being represented as a weighted average of the corresponding relaxation rates in the two environments, are directly proportional to the fraction of the bounded water molecules at the polymer surface. In the range of diffusion time measured, the diffusion of water molecules is evidently not hindered. TEM of freeze fractured PMMA, Na hydrocolloid samples and the translational diffusion coefficient confirm the existence of the diffusional pathways between the polymer chains.
Descriptors		COLLOIDS WATER DIFFUSION NUCLEAR MAGNETIC RESONANCE MICROSCOPY, ELECTRON MODELS, BIOLOGICAL DRUG DELIVERY SYSTEMS