Solid-state 13C NMR study of poly(vinyl alcohol) gels.
Poly(vinyl alcohol) (PVA) with 55% and 61% syndiotacticity, and their related dry and hydrated gels obtained by two different freeze-thawing cycles have been investigated using the solid-state 13C CP-MAS NMR technique. From a comparative analysis of the spectra, evidence was obtained that the gelation process largely disrupts the intramolecular hydrogen-bonded network of the PVA. The addition of water to the dry gels favours their swelling, destroying intra-chain hydrogen bonds between hydroxyl groups as a function of the degree of tacticity and the gelation procedure, and promotes the formation of new networks of interchain hydrogen bonds. Information on the dynamics of the polymeric domains in the kilohertz range has been obtained from the analysis of the spin relaxation times T1rho(1H) and T1rho(13C) indicating that homogeneous arrangements of the amorphous or swollen polymeric chains exist, independent of the preparation method or the tacticity of the PVA chains.
Dipartimento di Scienze Chimiche, Universita' di Cagliari, Cittadella Universitaria di Monserrato, Italy.
Simona
S
Lai
Mariano
M
Casu
Giuseppe
G
Saba
Adolfo
A
Lai
Ivan
I
Husu
Giancarlo
G
Masci
Vittorio
V
Crescenzi
D005782:Gels; D009682:Magnetic Resonance Spectroscopy; D011142:Polyvinyl Alcohol / Q000737:chemistry*
D005782:Gels; D011142:Polyvinyl Alcohol