Thermodynamic analysis of the conformational transition in aqueous solutions of isotactic and atactic poly(methacrylic acid) and the hydrophobic effect

Kogej, Ksenija (author)

The affinity of amphiphilic compounds for water is important in various processes, e.g., in conformational transitions of biopolymers, protein folding/unfolding, partitioning of drugs in the living systems, and many others. Herein, we study the conformational transition of two isomer forms of poly(methacrylic acid) (PMA), isotactic (iPMA) and atactic (aPMA), in water. These isomers are chemically equivalent and differ only in the arrangement of functional groups along the chain. A complete thermodynamic analysis of the transition of the PMA chains from the compact to the extended form (comprising the conformational transition) in water in the presence of three alkali chlorides is conducted by determining the free energy, enthalpy, and entropy changes of the process as a function of temperature, and therefrom also the heat capacity change. The heat capacity change of the transition is positive (+20 J/K mol) for aPMA and negative (–50 J/K mol) for iPMA. This result suggests a different affinity of PMA isomers for water. The conformational transition of iPMA is parallel to the transfer of polar solutes into water, whereas that of aPMA agrees with the transfer of nonpolar solutes into water.

• Language: English
• Keywords: polymethacrylic acid, isotactic, conformational transition, thermodynamics, temperature dependence, hydrophobic effect, hydrophobic hydration
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Publication status: Published
• Publication version: Version of Record
• Year: 2016
• Number of pages: 19 str.
• Numbering: Vol. 8, iss. 5, art. 168
• PID: 20.500.12556/RUL-130304
• UDC: 544.35:544.6.018.47-036.5
• ISSN on article: 2073-4360
• DOI: 10.3390/polym8050168
• COBISS.SI-ID: 1536889283
• Publication date in RUL: 13.09.2021

Record is a part of a journal

• Title: Polymers
• Shortened title: Polymers
• Publisher: MDPI
• ISSN: 2073-4360
• COBISS.SI-ID: 517951257

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.
• Licensing start date: 01.05.2016

Secondary language

• Language: Slovenian
• Keywords: fizikalna kemija, vodne raztopine, polielektrolitske raztopine, polielektroliti, termodinamika, konformacijski prehodi, temperaturna odvisnost, hidrofobni efekt, hidrofobnost, polimetakrilna kislina, izotaktična polimetakrilska kislina, PMA

Projects

• Funder: ARRS - Slovenian Research Agency
• Project number: P1-0201
• Name: Fizikalna kemija