Very fast CO2 response and hydrophobic properties of novel poly(ionic liquid)s

Abstract

A series of polymerizable tetraalkylammonium ionic liquids based on [2-(methacryloyloxy)ethyl]dimethylheptyl ammonium cation and bis(trifluoromethylsulfonyl)imide, nonafluoro-1-butanesulfonate, dodecylbenzenesulfonate, heptadecafluorooctanesulfonate, 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoroundecanoate anions, as well as their corresponding homo- and copolymers, have been synthesized and characterized by means of ¹H NMR, TG-DTA, DSC, MALDI-TOF, viscosimetry and XPS investigations. Hydrophobic and CO₂ sensing properties of the poly(ionic liquid)s have been explored by dynamic contact angle and quartz crystal microbalance measurements. The CO₂ sensing behavior of present polymers is very remarkable as they are featured by extremely rapid and completely reversible response without any memory-effect. Best results, in terms of sensitivity, have been obtained for [2-(methacryloyloxy)ethyl]dimethylheptyl ammonium nonafluoro-1-butanesulfonate-based homopolymer. Tensiometric data show good hydrophobic properties with θ_adv > 90° for all the polymers under study except the one involving 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoroundecanoate anion (θ_adv = 78.3°); receding contact angles, representative of the most hydrophilic portions of the polymers surface, lie in the range 22–54° and can be further improved by choosing the proper long-chained N-alkyl groups.