Ion-macromolecule interactions studied with model polyurethanes

Borja Fernández-d'Arlas; Miguel Ángel Huertos; Alejandro J Müller

doi:10.1016/j.jcis.2017.08.099

Ion-macromolecule interactions studied with model polyurethanes

J Colloid Interface Sci. 2018 Jan 1:509:102-112. doi: 10.1016/j.jcis.2017.08.099. Epub 2017 Sep 2.

Authors

Borja Fernández-d'Arlas¹, Miguel Ángel Huertos², Alejandro J Müller³

Affiliations

¹ INAMAT (Institute for Advanced Materials) y Departamento de Física, Universidad Pública de Navarra (UPNA), Centro Jerónimo de Ayanz, Campus Arrosadía, 31006 Pamplona, Spain; POLYMAT and Polymer Science and Technology Department, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel de Lardizábal 3, 20018 Donostia-San Sebastián, Spain. Electronic address: Borja.fernandezdarlas@unavarra.es.
² Grupo de Investigación Química Inorgánica, Departamento de Química Aplicada, Universidad del País Vasco UPV/EHU, Avda. Manuel de Lardizábal 3, 20018 San Sebastian, Spain; IKERBASQUE, Basque Foundation for Science, Bilbao, Spain.
³ POLYMAT and Polymer Science and Technology Department, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel de Lardizábal 3, 20018 Donostia-San Sebastián, Spain; IKERBASQUE, Basque Foundation for Science, Bilbao, Spain.

PMID: 28892743
DOI: 10.1016/j.jcis.2017.08.099

Abstract

Hypothesis: The solubility and self-assembly of macromolecules in solution can be tuned by the presence of different salts. Natural proteins have been long manipulated with the aid of salts, and natural silk is processed in the gland tip across a gradient of different salts which modifies its solubility. Hence, the comprehensive understanding of the role of ion-macromolecule interactions should pave the way towards a biomimetic processing of macromolecules.

Experiments: A model polyurethane catiomer (PU⁺) with high density of hydrogen donors and acceptors (similar to proteins) has been designed and synthesized in order to study ion-macromolecule interactions by means of dynamic light scattering (DLS), infrared spectroscopy (FTIR) and nuclear magnetic resonance (¹³C NMR).

Findings: The PU⁺ solubility in the presence of different salts exhibited a reversed anion Hofmeister series (i.e., the anion ability to precipitate the PU⁺ was F^-<Cl^-<Br^-<NO₃^-<CH₃COO^-<H₂PO₄^-<H₂CO₃^-<I^-<ClO₄^-<SCN^-). The ordering of this series was found to be predicted, for the first time, by the Born-Landé-Ephraim-Fajans-Bjerrum model used here to estimate the degree of macromolecule-ion pairing in water solution. This work also helps understanding the role of cations and anions nature on their interaction with macromolecules backbone.

Keywords: Aqueous macromolecules; Hofmeister series; Ion-macromolecule interactions; Polyurethane; Self-assembly.