Synthesis and Characterization of Phosphonated Graphene Oxide and Sulfonated Poly(styrene-isobutylene-styrene) Composite Membranes

Abstract

Graphene oxide (GO) and its phosphonated analogue (pGO) have been incorporated into sulfonated poly(styrene-isobutylene-styrene) (SO3H SIBS) to generate membranes with enhanced water retention. The polymer nanocomposite membranes (PNMs) were prepared per SIBS sulfonation level (i.e., 38, 61, and 90 mole %), filler type (i.e., GO and pGO) and filler loading (i.e., 0.1, 0.5 and 1.0 wt.%). FT-IR and TGA confirmed the functionalization and incorporation of the fillers into SO3H SIBS. No significant changes were observed in the thermal stability or FTIR spectra of the PNMs after addition of the fillers. Dissimilar behaviors were observed for the water absorption capabilities (i.e., swelling ratio and water uptake) after incorporation of the fillers. The nanofillers enhanced the water absorption of the sulfonated polymer, possibly due to interconnections between the ionic groups. Therefore, the PNMs could not only potentially function as proton exchange membranes (PEMs) for several applications such as direct methanol fuel cells (DMFCs).

Polymer Nanocomposite Membranes of Sulfonated Poly(Styrene‐Isobutylene‐Styrene) With Sulfonated Graphene Oxide for Fuel Cell and Protective Clothing Applications

“…The first region at approximately 100°C is attributed to the dehydration (i.e., loss of atmospheric moisture absorbed by the sulfonic groups) of the polymer. The second region in the 220–280 ° C range is attributed to the desulfonation (i.e., loss of the sulfonic groups) of the polymer and the third (410–430 ° C) to the degradation of the polymer backbone . Similar to other studies that incorporated fillers into SIBS or other polymers, the thermal stabilities of the membranes were unaffected by the incorporation of GO/sGO .…”

“…Only the spectra for the maximum filler loading (i.e., 10 wt%) will be shown because no significant changes were observed in the PNMs at lower nanofiller levels. The spectra for SO 3 H SIBS show four bands at 1,151, 1,124, 1,034, and 1,007 cm −1 , which are representative of the stretching vibrations associated to the sulfonic group [37,42,44,45]. Therefore, overlapping occurs for the C-O, SO 3 H, and Si − O stretching vibrations of GO/sGO.…”

“…Sulfonation reactions were prepared with an acetyl sulfate molar ratio of 1:1, 2:1, and 5:1 to obtain low, moderate and high sulfonation levels (i.e., 37, 61, and 88 mol%). The polymer sulfonation and washing procedures are described elsewhere [37,42,[44][45][46]. The membranes were prepared using the solvent casting procedure at ambient temperature.…”

Influence of carboxylated and phosphonated single‐walled carbon nanotubes on the transport properties of sulfonated poly(styrene‐isobutylene‐styrene) membranes

“…Efforts have been focused on the addition of fillers that may decrease the methanol permeability of the membranes without significantly decreasing the proton transport . Avilés‐Barreto and Suleiman found that SO 3 H SIBS is suitable as a dispersant matrix for SWCNTs .…”

“…26 Efforts have been focused on the addition of fillers that may decrease the methanol permeability of the membranes without significantly decreasing the proton transport. 17,20,25,27,28 Avilés-Barreto and Suleiman found that SO 3 H SIBS is suitable as a dispersant matrix for SWCNTs. 25 Out of all the functionalizations performed to the SWCNTs, only sulfonation enhanced the performance of SO 3 H SIBS for DMFC and chemical and biological protective clothing (CBPC) applications.…”