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

Abstract

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.

Keywords

fizikalna kemija;vodne raztopine;polielektrolitske raztopine;polielektroliti;termodinamika;konformacijski prehodi;temperaturna odvisnost;hidrofobni efekt;hidrofobnost;polimetakrilna kislina;izotaktična polimetakrilska kislina;PMA;polymethacrylic acid;isotactic;conformational transition;thermodynamics;temperature dependence;hydrophobic effect;hydrophobic hydration;

Data

Language:	English
Year of publishing:	2016
Typology:	1.01 - Original Scientific Article
Organization:	UL FKKT - Faculty of Chemistry and Chemical Technology
UDC:	544.35:544.6.018.47-036.5
COBISS:	1536889283
ISSN:	2073-4360
Views:	170
Downloads:	54
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	Slovenian
Secondary keywords:	fizikalna kemija;vodne raztopine;polielektrolitske raztopine;polielektroliti;termodinamika;konformacijski prehodi;temperaturna odvisnost;hidrofobni efekt;hidrofobnost;polimetakrilna kislina;izotaktična polimetakrilska kislina;PMA;
Type (COBISS):	Article
Pages:	str. 1-19 (art. no. 168)
Volume:	ǂVol. ǂ8
Issue:	ǂiss. ǂ5
Chronology:	2016
DOI:	10.3390/polym8050168
ID:	13390867