Temperature and pH-Dependent Response of Poly(Acrylic Acid) and Poly(Acrylic Acid-co-Methyl Acrylate) in Highly Concentrated Potassium Chloride Aqueous Solutions.

Aleksander Sinek,Shin-Ichi Yusa,Andrzej Gierczycki,Dorota Neugebauer,Maria Kupczak,Marcin Lemanowicz,Anna Mielańczyk

doi:10.3390/polym12020486

Aleksander Sinek, Shin-Ichi Yusa + Show 5 more

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https://doi.org/10.3390/polym12020486

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Journal: Polymers	Publication Date: Feb 21, 2020
Citations: 7	License type: CC BY 4.0

Affiliation: Silesian University of Technology, University of Hyogo

Abstract

In this study, the phase transition phenomena of linear poly(acrylic acid) (PAA) and linear or star-shaped poly(acrylic acid-co-methyl acrylate) (P(AA-co-MA)) in highly concentrated KCl solutions were investigated. The effects of polymer molecular weight, topology, and composition on their phase transition behavior in solution were investigated. The cloud point temperature (TCP) of polymers drastically increased as the KCl concentration (CKCl) and solution pH increased. CKCl strongly influenced the temperature range at which the phase transition of PAA occurred: CKCl of 1.0–2.2 M allowed the phase transition to occur between 30 and 75 °C. Unfortunately, at CKCl above 2.6 M, the TCP of PAA was too high to theoretically trigger the crystallization of KCl. The addition of hydrophobic methyl acrylate moieties decreased the TCP into a temperature region where KCl crystallization could occur. Additionally, the hydrodynamic diameters (Dh) and zeta potentials of commercial PAA samples were examined at room temperature and at their TCP using dynamic light scattering. The salt concentration (from 1 to 3 M) did not impact the hydrodynamic diameter of the molecules. Dh values were 1500 and 15 nm at room temperature and at TCP, respectively.

Highlights

IntroductionStimuli-responsive polymers considerably change their properties, such as their hydrophilic/hydrophobic state and conformation due to small changes in environmental stimuli [1,2]in either a continuous or stepwise manner [3,4,5]
Stimuli-responsive polymers considerably change their properties, such as their hydrophilic/hydrophobic state and conformation due to small changes in environmental stimuli [1,2]in either a continuous or stepwise manner [3,4,5]
A few publications have been dedicated to polymers with an upper critical solution temperature (UCST), in which the phase transition occurs between 273 and

Summary

Introduction

Stimuli-responsive polymers considerably change their properties, such as their hydrophilic/hydrophobic state and conformation due to small changes in environmental stimuli [1,2]in either a continuous or stepwise manner [3,4,5]. A few publications have been dedicated to polymers with an upper critical solution temperature (UCST), in which the phase transition occurs between 273 and. Polymers 2020, 12, 486 solution temperature (LCST), especially in the temperatures close to 309 K since they are meant as drug delivery systems in human body. The specific mechanisms involved in phase transitions often restrict certain practical applications of polymers due to their strict requirements, such as salt-free solutions [10,19]. Recent publications have reported polymers that exhibit both a UCST and LCST depending on their concentration, such as poly(trimethylene ether)glycol [20,21]

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