Accession Number:

ADA579466

Title:

From Green Aerogels to Porous Graphite by Emulsion Gelation of Acrylonitrile

Descriptive Note:

Journal article

Corporate Author:

MISSOURI UNIV OF SCIENCE AND TECHNOLOGY ROLLA

Personal Author(s):

• Sadekar, Anand G.
• Mahadik, Shruti S.
• Bang, Abhishek N.
• Larimore, Zachary J.
• Wisner, Clarissa A.
• Bertino, Massimo F.
• Kalkan, A. K.
• Mang, Joseph T.
• Sotiriou-Leventis, Chariklia
• Leventis, Nicholas

Report Date:

2012-01-01

Pagination or Media Count:

25.0

Abstract:

Porous carbons, including carbon C- aerogels, are technologically important materials, while polyacrylonitrile PAN is the main industrial source of graphite fiber. Graphite aerogels are synthesized herewith pyrolytically from PAN aerogels, which in turn are prepared first by solution copolymerization in toluene of acrylonitrile AN with ethylene glycol dimethacrylate EGDMA or 1,6-hexanediol diacrylate HDDA. Gelation is induced photochemically and involves phase-separation of live nanoparticles that get linked covalently into a robust 3D network. The goal of this work was to transfer that process into aqueous systems and obtain similar nanostructures in terms of particle sizes, porosity, and surface areas. That was accomplished by forcing the monomers into microemulsions, in essence inducing phase-separation of virtual primary particles before polymerization. Small angle neutron scattering SANS in combination with location-of-initiator control experiments support that monomer reservoir droplets feed polymerization in 3 nm radius micelles yielding eventually large approx. 60 nm primary particles. The latter form gels that are dried into macro-mesoporous aerogels under ambient pressure from water. PAN aerogels by either solution or emulsion gelation are aromatized 240 C, air, carbonized 800 C, Ar, and graphitized 2300 deg C, He into porous structures 49-64 vv empty space with electrical conductivities greater than 5x higher than those reported for other C-aerogels at similar densities. Despite a significant pyrolytic loss of matter up to 50-70 ww, samples shrink conformally 31-57 and remain monolithic. Chemical transformations are followed with CHN analysis, 13C NMR, XRD, Raman, and HRTEM. Materials properties are monitored by SEM and N2-sorption. The extent and effectiveness of interparticle connectivity is evaluated by quasi-static compression.

Descriptors:

• *ACRYLONITRILE POLYMERS
• *AEROGELS
• *EMULSIONS
• *GELATION
• *GRAPHITE
• *POROUS MATERIALS
• CARBON
• FIBERS
• SURFACE ACTIVE SUBSTANCES

Subject Categories:

• Physical Chemistry
• Polymer Chemistry
• Geology, Geochemistry and Mineralogy

Distribution Statement:

APPROVED FOR PUBLIC RELEASE