Rheological Characterization of the Thermal Gelation of Poly(n-isopropylacrylamide) and Poly(n-isopropylacrylamide) Co-acrylic Acid

Some systems show high miscibility in water at low temperatures while they phase separate at high temperatures. Before the macroscopic phase separation there is a strong turbidity, defined as clouding [1, 2]. At certain circumstances, namely above a critical concentration, the polymer system stays turbid with a gel-like appearance, without any macroscopic phase separation [3]. Gels defined in terms of rheological characteristics can be considered as two component systems exhibiting a solid-like behaviour under small deformation. Thermal reversible gelation Abstract: The combined effect of charged addition and molecular weight, Mw, on the thermal gelation and gel dissolution of poly(N-isopropylacrylamide) chains was explored by using Rheological techniques. The synthesized charged derivative is poly(N-isopropylacrylamide co-Acrylic acid). The rheological behavior of the two macromolecules is clearly different: the thermal gelation of the high Mw and charged macromolecule is much more accentuated. This suggests that the gelation at high temperatures only occurs when the inter polymer aggregate distance is sufficiently short to allow polymer bridging; this situation can be achieved by different approaches, such as increasing polymer concentration and increasing polymer persistence length and polymer Mw .