Three series of amorphous cross-linked poly(ethylene oxide) (XLPEO) rubbers were prepared by photopolymerization of prepolymer solutions containing poly(ethylene glycol) diacrylate (PEGDA) cross-linker and one of three structurally similar short chain acrylate co-monomers: 2-hydroxyethyl acrylate (2-HEA), ethylene glycol methyl ether acrylate (EGMEA) and 2-ethoxyethyl acrylate (2-EEA). Copolymerization with the mono-functional acrylates led to the insertion of short side branches along the network backbone, terminated by either hydroxy, methoxy or ethoxy functional groups. Permeability measurements for the copolymers (35 °C) are presented for CO2, H2, CH4, O2 and N2; corresponding solubility and diffusivity data are presented for CO2 and CH4. The side branches significantly influenced the thermal and gas transport properties of the polymers: methoxy and ethoxy terminated side-branches modestly increased fractional free volume and gas permeability. This effect was more pronounced by the introduction of ethoxy-terminated 2-EEA, while the presence of hydroxy terminated 2-HEA side-branches reduced free volume, resulting in a strong decrease in gas permeability with increasing co-monomer content. In each case, gas diffusivity correlated with polymer fractional free volume, while gas solubility was a function of both free volume characteristics and the corresponding concentration and accessibility of polar groups within the networks. The resulting selectivity ratios reflected variations in penetrant affinity and size discrimination as a function of copolymer composition. This study highlights the significant changes in various XLPEO properties that can be achieved by making small changes to its network structure.
|Number of pages||13|
|Journal||Journal of Membrane Science|
|State||Published - Feb 5 2009|
Bibliographical noteFunding Information:
We gratefully acknowledge partial support of this work by the U.S. Department of Energy (Grant DE-FG02-02ER15362) and by the U.S. National Science Foundation (Grant CBET-0515425). Activities at the University of Kentucky were supported by a grant from the Kentucky Science and Engineering Foundation as per Grant Agreement KSEF-148-502-05-130 with the Kentucky Science and Technology Corporation, and by the U.S. National Science Foundation Research Experiences for Undergraduates Program administered through the University of Kentucky Center of Membrane Sciences (Grant DMR-0453488). We would also like to thank Mr. Gustavo A. Espinoza (Earlham College, Richmond IN) and Ms. Josefina Guzman (Texas A&M University, College Station TX), both formerly of Liberal Arts and Science Academy, Lyndon B. Johnson High School, Austin TX, for their assistance in developing the density measurement technique. Mr. Espinoza’s and Ms. Guzman’s work were supported in part by the Center for Layered Polymeric Systems under a grant from the U.S. National Science Foundation (Grant DMR-0423914).
- Carbon dioxide
- Gas separation
- Polyethylene oxide
- Short chain pendant
- Structure/property relationship
ASJC Scopus subject areas
- Materials Science (all)
- Physical and Theoretical Chemistry
- Filtration and Separation