Study of Active Water Absorption of Polystyrene-Based Ionomers
- PDF / 3,212,848 Bytes
- 7 Pages / 595 x 842 pts (A4) Page_size
- 22 Downloads / 182 Views
Article www.springer.com/13233 pISSN 1598-5032 eISSN 2092-7673
Study of Active Water Absorption of Polystyrene-Based Ionomers In-Sub So1 Joon-Seop Kim*,1,2
1
Department of Renewable Energy Convergence, Chosun University, 309 Pilmun-daero, Dong-gu, Gwangju 61452, Korea 2 Department of Biochemical & Polymer Engineering, Chosun University, 309 Pilmun-daero, Dong-gu, Gwangju 61452, Korea Received January 14, 2020 / Revised May 27, 2020 / Accepted June 1, 2020
Abstract: The active water absorption behavior of poly(styrene-co-methacrylate) PSMANa and sulfonated polystyrene PSSNa ionomers was studied. On one hand, the acidic copolymers did not absorb water noticeably. On the other hand, the amount of water absorbed by the ionomer increased with increasing ion content. Especially when the ion contents of the PSMANa and PSSNa ionomers exceeded 6 and 10 mol%, respectively, the maximum amount of the water absorbed by the ionomers increased rapidly as the ion content increased. This indicated that the cluster-dominant ionomers exhibited stronger water absorption behavior, compared to the matrix-dominant ionomers. In addition, when the ion contents of the PSMANa and PSSNa ionomers were less than 6 and 10 mol%, respectively, the volume and shape of the bulk ionomers did not change significantly by the water absorption. Morphological studies on the soaked ionomers showed that the SAXS peak shifted to lower angles as the water uptake increased with increasing ion content of the ionomers, which was consistent with the results obtained by the swelling method. Keywords: water uptake, ionomer, multiplets, swelling, morphology.
1. Introduction Ionomers are polymers with a small amount of ionic groups in the polymer backbone chain. In the relatively non-polar polymer matrix of the ionomer, ionic aggregates, called multiplets, can be formed by the interactions between the ion pairs of the ionomer and the polarity difference between the nonpolar polymer main chains and the ionic groups of the ionomer; the multiplets of the ionomer in a dry state act as physical crosslinks.1 Since the ionomers have the ionic groups, studies on the water absorption of the ionomers have been an interesting topic from early on.1-7 When the ionomer absorbs water, the water molecules enter the multiplets. Then, the interactions between the ion pairs in the multiplets are weakened, and the multiplets can no longer function as effective physical crosslinks. Thus, the water molecules in the multiplets result in the rapid deterioration of the mechanical and physical properties of the ionomer. Therefore, ionomers used in bulk, except for ionomers used as fuel cell membranes, are used in situations that minimize contact with water. Studies on the water absorption of ionomers have mainly focused on polytetrafluoroethylene ionomers since their appearance in the late 1960’s, and a number of water absorption models have been proposed.7,8-23 In the case of ethylene-co-methacrylate ionomers, Yano et al. suggested that water molecules entered Acknowledgment: This study
Data Loading...
