Abstract
The chemical structure and morphology of a set of sulfonic gel-type poly(styrene-divinylbenzene) resins (2 mol% DVB) prepared with different synthetic approaches were investigated by solid state NMR, Inverse Size Exclusion Chromatography (ISEC), FT-IR and elemental analysis to compare their swollen state structure. FT-IR and solid state NMR clearly show that the sulfonation mainly occurs in the para- position with respect the main polymer chain. Sensible proportions of sulfone bridges were found in the materials obtained with oleum and chlorosulfonic acid. With oleum, the presence of the sulfone bridges is clearly associated to a reduced ability to swell in the water medium relative to the proton exchange capacity. This highlights the cross-linking action of the sulfone bridges according to ISEC results, showing a high proportion of a dense polymer fraction in the swollen material. An even higher degree of sulfone-bridging, lower swelling ability, and a high proportion of a dense polymer fraction in the swollen material are found in the resin obtained with chlorosulfonic acid. As a matter of fact, Cross Polarization Magic Angle Spinning Nuclear Magnetic Resonance (CP-MAS 13C-NMR), elemental analysis, and ion exchange capacity, show that oleum and chlorosulfonic acid produced resins with remarkably smaller pores and lower swollen gel volume in polar solvents, with respect to concentrated sulfuric acid.
Highlights
Sulfonic resins based on polystyrene-divinylbenzene (PS-DVB) are widely used in the fields of acid catalysis, ion exchange, and separation processes [1,2]
The direct sulfonation of PS-DVB resins with either sulfuric acid or oleum, or with chlorosulfonic acid and subsequent alkaline hydrolysis [14], introduces the sulfonic groups, and sulfone bridges between pairs of phenyl rings
All these pieces of information might be useful for better controlling the production of sulfonated ion-exchange resins and tailoring their morphology to specific practical applications under solid-liquid condition processes
Summary
Sulfonic resins based on polystyrene-divinylbenzene (PS-DVB) are widely used in the fields of acid catalysis, ion exchange, and separation processes [1,2] They must be used in the presence of a suitable liquid phase (water, an aqueous solution, or a polar organic solvent) able to swell the polymer framework: under these conditions an extensive nanometer size porosity with a surface area of hundreds of square meters per gram is generated [3,4,5]. We investigated on the effect of the additional sulfone-bridge cross-links on the swollen state morphology of the ion-exchangers. For this purpose, the swollen sulfonated resins were characterized by ISEC in order to disclose differences in the porosity of ion-exchangers prepared with different sulfonating agents. All these pieces of information might be useful for better controlling the production of sulfonated ion-exchange resins and tailoring their morphology to specific practical applications under solid-liquid condition processes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
