title: Porous polyimide membranes prepared by wet phase inversion for use in low dielectric applications.
abstract: A wet phase inversion process of polyamic acid (PAA) allowed fabrication of a porous membrane of polyimide (PI) with the combination of a low dielectric constant (1.7) and reasonable mechanical properties (Tensile strain: 8.04%, toughness: 3.4 MJ/m3, tensile stress: 39.17 MPa, and young modulus: 1.13 GPa), with further thermal imidization process of PAA. PAA was simply synthesized from purified pyromellitic dianhydride (PMDA) and 4,4-oxydianiline (ODA) in two different reaction solvents such as γ-butyrolactone (GBL) and N-methyl-2-pyrrolidinone (NMP), which produce Mw/PDI of 630,000/1.45 and 280,000/2.0, respectively. The porous PAA membrane was fabricated by the wet phase inversion process based on a solvent/non-solvent system via tailored composition between GBL and NMP. The porosity of PI, indicative of a low electric constant, decreased with increasing concentration of GBL, which was caused by sponge-like formation. However, due to interplay between the low electric constant (structural formation) and the mechanical properties, GBL was employed for further exploration, using toluene and acetone vs. DI-water as a coagulation media. Non-solvents influenced determination of the PAA membrane size and porosity. With this approach, insight into the interplay between dielectric properties and mechanical properties will inform a wide range of potential low-k material applications.
authors.affiliation: Energy Institute, Energy and Mineral Engineering, Pennsylvania State University, University Park, PA 16801, USA. jmhong@kist.re.kr.
authors.forename: Soohyun
authors.initials: S
authors.lastname: Kim
authors.forename: Keon-Soo
authors.initials: KS
authors.lastname: Jang
authors.forename: Hee-Dok
authors.initials: HD
authors.lastname: Choi
authors.forename: Seung-Hoon
authors.initials: SH
authors.lastname: Choi
authors.forename: Seong-Ji
authors.initials: SJ
authors.lastname: Kwon
authors.forename: Il-Doo
authors.initials: ID
authors.lastname: Kim
authors.forename: Jung Ah
authors.initials: JA
authors.lastname: Lim
authors.forename: Jae-Min
authors.initials: JM
authors.lastname: Hong
mesh_terms: D015107:4-Butyrolactone / Q000737:chemistry; D001555:Benzene Derivatives / Q000737:chemistry*; D004560:Electricity; D007094:Imides / Q000737:chemistry*; D008567:Membranes, Artificial; D008855:Microscopy, Electron, Scanning; D010797:Phthalimides / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D016062:Porosity; D012997:Solvents; D017550:Spectroscopy, Fourier Transform Infrared; D013718:Tensile Strength; D014867:Water / Q000737:chemistry*
chemical_list: D001555:Benzene Derivatives; D007094:Imides; D008567:Membranes, Artificial; D010797:Phthalimides; D011108:Polymers; D012997:Solvents; C513053:polyamic acid; D014867:Water; D015107:4-Butyrolactone