Poly(Arylene Ether Sulfone)s with HEPES Pendants: Synthesis, Thermal, and Dielectric Studies

Polyethersulfone with active carboxylic acid pendants was prepared from solution polymerization via nucleophilic displacement polycondensation reaction among 4,4′-dichlorodiphenyl sulfone (DCDPS) and 4,4′-bis(4-hydroxyphenyl) valeric acid (BHPA). The conditions necessary to synthesize and purify the polymer were investigated in some details. The synthesized polyethersulfone comprises sulfone and ether linkages in addition to reactive carboxylic acid functionality; this reactive carboxylic acid group was exploited to hold the HEPES moiety via ester linkage and is achieved by simple DCC coupling condition at ambient temperature. Without impairing the primary polymeric backbone, three modified polymers were prepared by varying the stoichiometric ratio of HEPES. Characterization of the polymers by 1H & 13C NMR, FT-IR, and TGA demonstrated that HEPES was quantitatively incorporated into the prime polymer. All the prepared polymers were pressed into tablets, and electrical contacts were established to study the dielectric properties. Finally, the influence of the HEPES on the dielectric properties was examined. 1. Introduction The field of ionomers has expanded over the past few decades and has become fundamental to the science of polymer technology; the intriguing properties and the wide range technological interests have been an ever increasing stimulus to fully focus on specialized applications such as electrochemical sensors [1, 2], polymer electrolyte fuel cells (PEMFCs) [3–5]. In recent years, there have been a multitude of new simple synthetic methodologies developed to aid in the construction of high performance polymers with suitable ionic groups [6]. Concurrently with these developments, the field of ionomers has matured within the last few decades; the richness of physical and chemical properties of these polymers finds its fundamental and potential response to technical field. In order to attain controlled charge separation and ion mobility, a variety of chemical modifications to the high performance Udel poly(ethersulfone) polymer are in lively practice via appended ionic pendants in PEMFCs application [7, 8]. Modification reactions create the enormous diverse applications providing new linkages with different functionalities. There is an on-going uncertainty about the best way to mitigate the synthetic pathway by changing the basic monomer scaffolds to attain efficient synchronized properties of resulting polymers and copolymers. Much effort to synthesize relatively inexpensive and thermally stable macromolecules including sulfonated and