Synthesis and Characterization of Toughened Thermally Rearranged Polymers, Poly(2,6-Dimethylphenylene-oxide) Based Copolymers and Polymer Blends for Gas Separation Membranes

Thermally rearranged (TR) polymers have outstanding gas separation properties, but are limited in their industrial application due to being mechanically brittle. A series of low volume fraction of a poly(arylene ether sulfone) (PAES) block was introduced into the TR precursor polyhydroxyimide (PI) chain to improve mechanical properties without compromising gas transport properties. The multiblock copolyhydroxyimide incorporated the PAES in systematically varied amounts and copolymerized it with 4,4'-(hexafluoroisopropylidene)diphthalic anhydride and 3,3’-dihydroxy-4,4’-diaminobiphenyl. Before thermal rearrangement, the PI-co-PAES precursors exhibited much more improved mechanical properties (tensile stress and strain at break) than those of homo polyimide precursor. After thermal rearrangement, tensile stress and strain at break of all TR copolymers decreased comparing to their corresponding precursors, but improved comparing to the homo TR polymer. Poly(phenylene oxide) (PPO) based copolymers (Chapter 4) and polymer blends (Chapter 5) were also studied for use as gas separation membranes. The polymer materials were cast into films, then crosslinked in the solid state with UV light. The ketone and benzylic methyl groups crosslinked upon exposure to UV light. For the study of PPO copolymers, copolymers were prepared by polycondensation of a difunctional PPO oligomer with 4,4’-difluorobenzophenone or 1,3-bis(4-fluorobenzoyl)benzene respectively. This study offers a means for fabrication of membrane films, fibers or composites, as well as tuning of gas transport properties through crosslinking in the solid state. While for the study of PPO polymer blends, PPO polymers with Mn’s from 2000-22,000 g/mole were synthesized and blended with a poly(arylene ether ketone) derived from bisphenol A and difluorobenzophenone (BPA-PAEK). The crosslinked blends had improved gas selectivities over their linear counterparts. The 90/10 wt/wt 22k PPO/BPA PAEK crosslinked blends gained the most O2/N2 selectivity and maintained a high permeability.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Macromolecular Science and Engineering

Department dc:contributor.department

Learning Sciences and Technologies

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2017

Author dc:creator

• Zhang, Wenrui

Chair dc:contributor.committeechair

• Riffle, Judy S.

Committee members dc:contributor.committeemember

• Davis, Richey M.
• Frazier, Charles E.
• Turner, S. Richard
• Mecham, Beverly S.

• gas separation membrane
• polyhydroxyimides
• thermally rearranged polymers
• poly(phenylene oxide)
• UV-crosslinking.

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

vt_gsexam:10331

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/86363