Synthesis and Characterization of Two Isomeric Thermal Rearrangable (TR) Polyimides for Gas Separation Membranes

Synthesis and Characterization of Two Isomeric Thermal Rearrangable (TR)
Polyimides for Gas Separation Membranes

1Hailun Borjigin, 1Donghoon Lee, 2Qiang Liu, 1Kyle Gaines, 2Benny D Freeman, 1Sue J
Mecham and 1James E. McGrath*

1Macromolecules and Interfaces Institute and Department of Chemistry, Virginia Tech,
Blacksburg, VA 24061

2Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712

* Corresponding author: Prof. James E. McGrath

jmcgrath@vt.edu

Tel: 001-540-231-5976

Fax: 001-540-231-8517

Abstract

Soluble aromatic polyimides containing ortho-positioned functional groups (hydroxyl

or acetate groups) were synthesized for thermal rearrangement (TR) processing

to complex partially crosslinked polybenzoxazoles (PBOs). The latter have been

shown to have great potential for highly selective CO2/CH4 separation membranes

applications. Fully imidized film forming polyimides with high-molecular-weight were

afforded via a ‘one-pot’ solution imidization technique utilizing the ester-acid (EA)

method starting from 2,2'-bis-(3,4-dicarboxyphenyl) hexafluoropropane dianhydride

(6FDA) with two isomeric monomers, 3,3'-dihydroxy-4,4'-diaminobiphenyl (HAB)

and 3,3'-diamino-4,4'-dihydroxybiphenyl (AHB). The two isomeric polyimides were

comprehensively characterized with respect to chemical structure, molecular weight,

thermal and mechanical properties by SEC, NMR, DSC, DMA, TGA and stress-strain

testing. The synthesis, characterization, film casting, thermal treatment, and initial gas

transport properties of high molecular weight polyimides and the isomeric effect on the

properties of the polymers will be discussed.