Intrinsic viscosity of intramolecularly crosslinked polyelectrolyte: Poly(vinyl alcohol)/borax systems

Abstract

The intrisic viscosity [q] of poly(viny1 alcohol) (PVA) was determined in aqueous solutions with various concentrations q, of borax (N%B40,) as functions of molecular weight Mand concentration cs of NaCl as an added salt. Polyelectrolyte viscosity behaviwr was observed for the systems containing both borax and NaCl, due to the complexation with negatively charged borate ions B(0H)c . [q] changes depending on the ionic strength I. It was found that the Stockmayer-Fixman treatment for the molecular-weight dependence of [q] is valid in the lower molecular-weight range (M < lo5), even though the present PVA chain contains some intrachain crosslinks. Theta conditions can be attained at an appropriate concentration of NaCl. The value of cso is dependent on q,, but the conformational parameter from the Stockmayer-Fixman treatment 4 is almost independent of q,. The effect of intrachain crosslinks becomes evident only as a considerably large negative value for the excluded volume parameter B at infinite ionic strength. In addition, the electrostatic part of the expansion factor 4' was found to be linearly correlated to a reduced parameter (M/Z)"z for all c, systems, from the slope of which the charge density was estimated.

Hybrid Polymer Salogels for Reversible Entrapment of Salt-Hydrate-Based Thermal Energy Storage Materials

“…The addition of borax did not result in the formation of a strong gel network capable of shape stabilizing and preventing leakage of CCH in the liquid state ( Figure S5 ). Similar results have been reported for borax complexation with diols in aqueous solutions 56 , 57 and hydrogels 58 , 59 containing NaCl. The decrease in viscosity 56 , 57 and modulus 58 , 59 were rationalized by a charge shielding effect of anionic boronate ester cross-links by chloride ions leading to enhanced intrachain crosslinking and polymer chain collapse.…”

“…Similar results have been reported for borax complexation with diols in aqueous solutions 56 , 57 and hydrogels 58 , 59 containing NaCl. The decrease in viscosity 56 , 57 and modulus 58 , 59 were rationalized by a charge shielding effect of anionic boronate ester cross-links by chloride ions leading to enhanced intrachain crosslinking and polymer chain collapse.…”

Borax Mediated Layer-by-Layer Self-Assembly of Neutral Poly(vinyl alcohol) and Chitosan

“…PVA forms cross-linked gels with many organic and inorganic cross-linkers . Particularly, gelation of PVA in the presence of boric acid and borax has been studied extensively. − The intermolecular hydrogen bonding takes place between hydroxyl groups on PVA chains which helps the gelation process. This mechanism is well established in literature .…”

DOSY NMR as a tool for predicting optimal conditions for hydrogel formation: The case of a hyperbranched polyglycidol cross-linked with boronic acids

“…However, the positive confirmation of cross‐linking between macromolecules is not obvious, especially for low‐molecular weight compounds, because other reactive functional groups present along the polymer chains could engage in intramolecular bond formation. The possibility of intramolecular cross‐linking is especially high for flexible linear polymers and cannot be excluded for hyperbranched polymers containing flexible branches . The formation of intramolecular bonds at the expense of intermolecular cross‐linking reduces the mechanical strength of the polymer network or may even prevent network formation.…”