Precision Polyelectrolytes with Phenylsulfonic Acid Branches at Every Five Carbons

A precision polyethylene containing phenyl branches at every fifth carbon (p5Ph) is nearly quantitatively functionalized (≈95%) with sulfonic acid groups on the para‐position of each phenyl branch (p5PhS‐H). Unlike polystyrene sulfonate (PSS), p5PhS‐H has a glass transition temperature (Tg = 109 °C) well below its thermal decomposition temperature (Td ≈ 200 °C), making this new material capable of thermal processing into molds and films at temperatures between these thermal limits. Neutralization of the sulfonic acid groups with varying counter cations (Li+, Na+, Cs+) produces a new class of precision polyelectrolytes. Neutralization and increasing size of the counter cation improves the thermal decomposition temperature (Td) to over 400 °C for the Cs+ form. Neutralization causes Tg to increase above Td for the Li+ and Na+ form. The Cs+ form is found to have an accessible Tg = 294 °C. Further investigations of water absorption and the polyelectrolyte effect of these systems are discussed. Sulfonated poly(styrene‐alt‐trimethylene) is water soluble in the acid form and when neutralized with various countercations (Li+, Na+, Cs+). In the dry, bulk state, the acid form has a glass transition of ≈109 °C and is able to be thermally molded below the decomposition temperature. Synthesis, characterization, water absorption, thermal properties, and the polyelectrolyte effect in diluted salt solutions are also discussed.