Influence of Triphenylphosphonium Pendant Groups on the Rheological and Morphological Properties of New Quaternized Polysulfone Luminita-Ioana Buruiana, 1 Ecaterina Avram, 1 Adriana Popa, 2 Iuliana Stoica, 1 Silvia Ioan 1 1 ‘Petru Poni’ Institute of Macromolecular Chemistry, Department of Physical Chemistry of Polymers, Iasi 700487, Romania 2 Institute of Chemistry Timisoara of Romanian Academy, Department of Organic Chemistry, Timisoara 300223, Romania Correspondence to: S. Ioan (E-mail: ioan_silvia@yahoo.com) ABSTRACT: A new quaternized polysulfone with triphenylphosphonium pendant groups was synthesized by reacting chloromethylated polysulfone with triphenylphosphine. The molecular restructurations, generated by hydrogen bonding, electrostatic interactions, and association phenomena in ternary quaternized polysulfone/N,N-dimethylformamide (solvent)/water (nonsolvent) systems, were eval- uated by rheological investigations. The polyelectrolyte effect, induced by enhanced dissociation of the ionizable groups and by mixed sol- vents’ quality, modify the rheological functions, that is, dynamic viscosity, elastic shear modulus, and viscous shear modulus, as well as the thermodynamic parameters obtained from the rheological properties, such as apparent activation energy. These results were corre- lated with the morphological properties of the films obtained from solutions in solvent/nonsolvent mixtures and compared with other quaternized polysulfones, having different hydrophobic characteristics. V C 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 129: 1752–1762, 2013 KEYWORDS: polyelectrolytes; rheology; morphology Received 23 March 2011; accepted 24 November 2012; published online 19 December 2012 DOI: 10.1002/app.38872 INTRODUCTION Polymeric membranes have been developed for a wide variety of applications in separation technology, biological processes, med- ical devices, and blood purification. Systems generally composed of polymer, solvent, and nonsolvent are usually used to make asymmetric membranes, the process being governed by diffusion of the various low-molecular-weight components. The introduc- tion of nonsolvents plays an important role in membrane for- mation through the occurrence of specific interactions in the three-component system. 1,2 Owing to some emerging problems, such as fouling, either blending with an additional polymer or other modification of membrane polymers became necessary. 3,4 Also, the studies have been carried out on the miscibility behavior of polymers with different polarities. 5–7 In this context, it is known that polysulfones, possessing superior properties, such as chemical, mechanical, and thermal resistance represent the ideal candidates in the membrane industry. The use of these polymers for the aqueous phase is restricted by their hydrophobicity and may be improved by their modification through different proc- esses. Thereby, desirable combination between polysulfones’ properties and their availability makes them attractive materials for the manufacture of commercial membranes and biomedical applications, such as gas separation, pervaporation, hemodialysis, nano and ultrafiltration, cell culture, biological processes, or blood purification. 8–10 Several reviews on the chemical modification of polysulfones by different chemical mechanisms have reported the introduction of reactive groups onto the polysulfone backbone. Among them, phosphonium cations may improve the thermal stability of polymers, being preferred for long-term use applications, 11 for facilitating aggregation 12 or as an aid in matrix reinforcement of ionomers. 13,14 Owing to the enhanced thermal stability of phos- phonium versus ammonium cations, phosphonium-containing polymers have a significant technological importance as phase- transfer catalysts, antistatic agents, biocides, humidity sensors, and water filtration membranes. 15 In this context, the search for alternative proton-conducting membranes capable of operating at high temperatures has extended the focus of the research area, and increased the interest for investigating alternative phosphonic ‘‘protogenic’’ groups, having ability to facilitate pro- ton conductivity under low-humidity conditions. 16–19 Moreover, phosphonated model compounds have been recently shown to possess an attractive combination of properties that motivates the investigation of phosphonated polymers as proton conduc- tors under low-humidity conditions. 16 Thus, polymers carrying these groups have properties quite different from those of poly- sulfones. For example, phosphonated polymers generally show a higher degree of hydrogen bonding and a lower water uptake, comparatively with their sulfonated compounds. As this is a relatively new topic, some key characteristics of the phosphonic V C 2012 Wiley Periodicals, Inc. 1752 J. APPL. POLYM. SCI. 2013, DOI: 10.1002/APP.38872 WILEYONLINELIBRARY.COM/APP