NMR studies of self-organization behavior of hydrophobically functionalized poly(4-styrenosulfonic-co-maleic acid) in aqueous solution Łukasz Lamch a, ⁎, Sylwia Ronka b , Piotr Warszyński c , Kazimiera A. Wilk a, ⁎ a Department of Engineering and Technology of Chemical Processes, Faculty of Chemistry, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland b Department of Engineering and Technology of Polymers, Faculty of Chemistry, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland c Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, ul. Niezapominajek 8, 30-239 Kraków, Poland abstract article info Article history: Received 24 January 2020 Received in revised form 21 March 2020 Accepted 24 March 2020 Available online 27 March 2020 Keywords: Aggregation in solution Hydrophobically functionalized polyelectrolyte Amphiphilic polyelectrolyte NMR diffusiometry NMR relaxometry Nuclear Overhauser effect Specially designed hydrophobically functionalized polyelectrolytes (HF-PEs) provide an important area of study, their unique properties being similar to those of biological systems, among them the strong tendency toward self-organization in aqueous solution caused by a combination of electrostatic and hydrophobic forces. A signif- icant issue in this context is the comprehensive physicochemical characterization of adsorption and aggregation properties of these amphiphilic polyelectrolytes. The main aim of the present research has been to synthesize and study aggregation properties in an aqueous solution of the hydrophobically functionalized poly(4- styrenosulfonic-co-maleic acid) (PSS/MA) with a differing degree of hydrophobization, side-chain lengths and pH-labile moiety type (i.e., ester (PSS/MA-g-C n OH) or secondary amide (PSS/MA-g-C n NH 2 ) groupings). Compre- hensive analysis of self-assembly properties, including utilization of high-resolution NMR techniques (diffusion- ordered and nuclear Overhauser effect spectroscopies, T 1 and T 2 relaxometry) and dynamic light scattering, re- vealed a strong dependence on concentration and type of labile linking group (ester or amide). It has been no- ticed that more rigid amide bonds hinder the formation of highly organized structures in aqueous systems compared to polyelectrolytes with ester moieties. Our results were supported by molecular modeling. The per- formed studies enabled us to obtain crucial information about the hydrophobized PEs structure and its influence on aggregation properties that are crucial for their application in pH-sensitive nanosized thin films and nanocarriers. © 2020 Elsevier B.V. All rights reserved. 1. Introduction Amphiphilic polymers may self-assembly in aqueous systems into various structures, including spheres and other micelle-like core-shell aggregates, lamellae, cylinders as well as gyroids. When a polymer is electrically neutral, its aggregation is controlled by thermodynamic fac- tors, i.e., interfacial tension and chain stretching energies [1–3]. On the other hand, self-assembly of amphiphilic polyelectrolytes is different from that of their neutral counterparts, mostly due to additional effects connected with long-range electrostatic interactions and the distribu- tion of counterions, those phenomena being largely related to adsorp- tion processes occurring at the interfaces during fabrication of polymeric drug nanocarriers [4,5]. For amphiphilic PEs, the presence of hydrophobic moieties covalently attached to the polyion backbone contributes both hydrophobic bonding, and long-range attractive inter- actions, the latter tend to minimize the chain expansion connected with the presence of strong repulsion by electrostatic forces in ionic groups [6,7]. Self assembly of hydrophobically functionalized polyelectrolytes (HF-PEs) or, more generally, decorated polyelectrolytes involves a sub- tle balance between repulsive and attractive forces, connected with nonpolar groups: hydrophobic bonding and long-range interactions as well as strong electrostatic repulsions of charged groups in polyelectro- lyte backbone [8,9]. Thus, processes of HF-PEs self-assembly, leading to the formation of different intra- or inter-pseudo-micelles, are strongly dependent on the polymer structure: generally polyelectrolytes with al- ternating groups or block sequence of hydrophobic tails are likely to form interchain associates in contrast to copolymers with random dis- tribution of these units tending to aggregate within a single polymer chain [1,2,6]. The structure of HF-PEs in aqueous systems is dependent on the content of hydrophobic units (generally, more hydrophobic co- polymers have a tendency to collapse into highly compact structures), their structure (linear bulky or highly branched) as well as Journal of Molecular Liquids 308 (2020) 112990 ⁎ Corresponding authors. E-mail addresses: lukasz.lamch@pwr.edu.pl (Ł Lamch), kazimiera.wilk@pwr.edu.pl (K.A. Wilk). https://doi.org/10.1016/j.molliq.2020.112990 0167-7322/© 2020 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq