caa a22 4500 475764161 CHVBK 20180406123600.0 cr unu---uuuuu 170329e20000301xx s 000 0 eng 10.1007/s003960050031 doi (NATIONALLICENCE)springer-10.1007/s003960050031 Reentrant behavior of poly(vinyl alcohol)-borax semidilute aqueous solutions [Elektronische Daten] [H.-L. Lin, T. L. Yu, C.-H. Cheng]  The reentrant behavior of Poly(vinyl alcohol) (PVA)-borax aqueous semidilute solutions with a PVA concentration of 20 g/l and borax concentrations varies from 0.0 to 0.20 M was investigated using dynamic light scattering (DLS) and dynamic viscoelastic measurements. Two (fast and slow modes) and three (fast, middle, and slow) relaxation modes of PVA semidilute aqueous solutions without and with the presence of borax, respectively, were observed from DLS measurements. The fast and middle relaxation modes were q 2-dependent (q is the scattering vector) characteristic of diffusive behavior; however, the slow modes were q 3-dependent, characteristic of intraparticle dynamics. The experimental results showed that the slow relaxation mode dominates the DLS relaxation. The DLS slow mode relaxation time, τs, and the viscoelastic modulus G′(ω) and G′′(ω) data had a similar trend and demonstrated reentrant behavior as the borax concentration was increased from 0.0 to 0.20 M, i.e. τs, G′(ω), and G′′(ω) fluctuated with increasing borax concentration. The excluded-volume effect of polymers, charge repulsion among borate ions bound on PVA molecules, and intermolecular cross-linking didiol-borate complexation caused an expansion of the polymer chain; however, the screening effect of free Na+ ions on the negative charge of the borate ions bound on PVA and intramolecular cross-linking didiol-borate complexation led to a shrinkage of the polymer chain. The reentrant behavior was the consequence of the balance between expansion and shrinkage of the PVA-borate complex. Springer-Verlag Berlin Heidelberg, 2000 Key words Poly(vinyl alcohol) nationallicence Borax nationallicence Dynamic light scattering nationallicence Viscoelasticity nationallicence Lin H.-L Department of Chemical Engineering Yuan-Ze University Nei-Li, Taoyuan 32026, Taiwan, TW aut Yu T. L. Department of Chemical Engineering Yuan-Ze University Nei-Li, Taoyuan 32026, Taiwan, TW aut Cheng C.-H Department of Chemistry National Tsing-Hua University Hsinchu 30042, Taiwan, TW aut https://doi.org/10.1007/s003960050031 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s003960050031 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Lin H.-L Department of Chemical Engineering Yuan-Ze University Nei-Li, Taoyuan 32026, Taiwan, TW aut NATIONALLICENCE 700 1- Yu T. L. Department of Chemical Engineering Yuan-Ze University Nei-Li, Taoyuan 32026, Taiwan, TW aut NATIONALLICENCE 700 1- Cheng C.-H Department of Chemistry National Tsing-Hua University Hsinchu 30042, Taiwan, TW aut Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer