To the Methodology of Phase Transition Temperature Determination in Aqueous Solutions of Thermo-Sensitive Polymers

Abstract

An advanced methodology of phase transition determination in aqueous solutions of thermo-sensitive polymers by using of the phase portraits method has been suggested. The methodology allows highly accurate determining the temperature when exactly a half of molecules loses solubility (from the maximum number that can go to another phase state under given conditions). It is shown that since phase transition passes usually in a wide enough temperature interval this indicator should be used as a quantitative parameter that characterizes phase transition process. Additionally the suggested methodology allows introducing one more quantitative parameter that reflects a sharpness of phase transition. The methodology is verified by an example of phase transitions study in aqueous solutions of thermo-sensitive copolymers based on N-vinylpyrrolidone and vinyl propyl ether.

Formation of Hydrophobic–Hydrophilic Associates in the N-Vinylpyrrolidone and Vinyl Propyl Ether Copolymer Aqueous Solutions

“…A similar expression finds applicability in representing turbidity dependencies with respect to pH [52].…”

“…Nonetheless, it is not uncommon for such intensity profiles to exhibit monotonic behaviors, thereby engendering certain complexities in the precise quantitative determination of pivotal control parameter thresholds (e.g., the critical temperature for phase transition). As delineated in [51,52], a viable strategy to surmount this challenge emerges through the identification of a phenomenological regularity encapsulating the underlying dependencies. The work of [52] illustrates that under specific circumstances, the temperature and pH profiles governing turbidity within a solution of a stimulus-sensitive polymer align harmoniously with the subsequent equation.…”

“…As delineated in [51,52], a viable strategy to surmount this challenge emerges through the identification of a phenomenological regularity encapsulating the underlying dependencies. The work of [52] illustrates that under specific circumstances, the temperature and pH profiles governing turbidity within a solution of a stimulus-sensitive polymer align harmoniously with the subsequent equation. This equation, harnessed via the phase portrait methodology [53], offers a satisfactory depiction of the turbidity variations.…”

“…It is noteworthy that the precise interpretation of the phase transition temperature within the context of monotonic dependencies remains an unresolved matter. In [51,52], a proposition was put forth to construe the phase transition temperature (or the critical pH value) as the temperature at which precisely half of the macromolecules in the solution undergo a change in their state. Given that Q a holds true, this criterion aligns with the value T = T 0 , as directly deduced from Equation (1).…”

Review of the Perspectives and Study of Thermo-Responsive Polymer Gels and Applications in Oil-Based Drilling Fluids

“…For thermo-responsive polymer gels, DLS can be used to measure the hydrodynamic size and distribution of particles within the system, with the temperature range of the abrupt change in particle size being indicative of the phase transition temperature [49]. Ribeiro et al [50] utilized DLS to analyze the sol-gel transition of diluted solutions (0.01% w/v) of PNVCL, NC-5%-80, and NC-5%-330 within the temperature range of 33.0 to 34.6 • C, demonstrating that the sphericity within the nanocomposites begins to increase below the phase transition temperature, leading to a decrease in optical transmittance and the diffusive reflectance profile.…”