(329d) Enhancing the Water Uptake and Retention of Membrane by Embedding Polymer Hollow Spheres as the Water Reservoirs

The development of high water-retention membranes has become a central goal of proton exchange membrane (PEM) fuel cell operating at a low relative humidity (RH) and elevated temperature. Intrigued by the water storage mechanisms in nature, we prepared three kinds of well-defined crosslinked polymer hollow spheres (PHSs) through distillation-precipitation polymerization. Changing the functional groups in the dense shell-layer of the PHSs can effectively tune the ratio of free water to bound water. After incorporating PHSs as the water reservoirs, the resultant composite membranes displayed an elevated water uptake, and the state of water can also be governed by the type and the content of the PHSs in the membranes. Water retention measurement revealed a much slower water release of the composite even at low relative humidity. This study suggests incorporating the polymer hollow spheres with diverse functional groups could manipulate the water uptake and retention capabilities and hence the proton conductivity, which offers a facile approach to fabrication of high proton conductive membranes for high-temperature and low humidity applications.