Enhanced Water Retention by Using Polymeric Microcapsules to Confer High Proton Conductivity on Membranes at Low Humidity

Abstract

AbstractWater retention is a pervasive issue in agriculture and industry. Inspired by the water‐storage mechanisms in plant cells, three kinds of polymeric microcapsules (PMCs) with carboxylic acid, sulfonic acid, and pyridyl groups are prepared using distillation–precipitation polymerization. The size of the lumen of the PMCs may govern the static water uptake by holding water molecules in a free‐water state, and the functional groups in the shell of PMCs may manipulate dynamic water release by holding water molecules in a bound‐water state, thus yielding PMCs with high and tunable water‐retention properties. Incorporation of PMCs into composite membranes gives rise to dramatically enhanced water‐retention properties and proton‐transfer pathway, and consequently increased proton conductivity by up to one order of magnitude over the control polymer membrane, under low relative humidity of 20%. This study may offer a facile and generic strategy to design and prepare a variety of materials with superior water‐retention properties.