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From Flexible to Hard Polyurethane Aerogels: The Effect of Molecular Functionality vs. Molecular Rigidity

Published online by Cambridge University Press:  02 March 2012

Chakkaravarthy Chidambareswarapattar ,
Jared M. Loebs ,
Zachary J. Larimore ,
Patrick M. McCarver ,
Autumn M. Kosbar ,
Lokesh Dharani ,
Huiyang Luo ,
Hongbing Lu ,
Chariklia Sotiriou-Leventis  and
Nicholas Leventis
Chakkaravarthy Chidambareswarapattar
Affiliation:
Department of Chemistry, Missouri University of Science and Technology, Rolla, MO 65409, U.S.A. (leventis@mst.edu; cslevent@mst.edu)
Jared M. Loebs
Affiliation:
Department of Mechanical Engineering, Missouri University of Science and Technology, Rolla, MO 65409, U.S.A. (dharani@mst.edu)
Zachary J. Larimore
Affiliation:
Department of Mechanical Engineering, Missouri University of Science and Technology, Rolla, MO 65409, U.S.A. (dharani@mst.edu)
Patrick M. McCarver
Affiliation:
Department of Chemistry, Missouri University of Science and Technology, Rolla, MO 65409, U.S.A. (leventis@mst.edu; cslevent@mst.edu)
Autumn M. Kosbar
Affiliation:
Department of Chemistry, Missouri University of Science and Technology, Rolla, MO 65409, U.S.A. (leventis@mst.edu; cslevent@mst.edu)
Lokesh Dharani
Affiliation:
Department of Mechanical Engineering, Missouri University of Science and Technology, Rolla, MO 65409, U.S.A. (dharani@mst.edu)
Huiyang Luo
Affiliation:
Department of Mechanical Engineering, University of Texas at Dallas, Richardson, TX 75080, U.S.A. (hongbing.lu@utdallas.edu)
Hongbing Lu
Affiliation:
Department of Mechanical Engineering, University of Texas at Dallas, Richardson, TX 75080, U.S.A. (hongbing.lu@utdallas.edu)
Chariklia Sotiriou-Leventis
Affiliation:
Department of Chemistry, Missouri University of Science and Technology, Rolla, MO 65409, U.S.A. (leventis@mst.edu; cslevent@mst.edu)
Nicholas Leventis
Affiliation:
Department of Chemistry, Missouri University of Science and Technology, Rolla, MO 65409, U.S.A. (leventis@mst.edu; cslevent@mst.edu)
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Abstract

High performance all-polymer aerogels are not only interesting for their low thermal conductivity, but also for their mechanical strength and their conversion to porous carbons. The prevalent design rule dictates that crosslinking at the monomer level decreases solubility of the developing polymer and induces phase separation of nanoparticles with high surface to volume ratios. Hence, hyperbranched structures based on trifunctional single aromatic core monomers should have enhanced interparticle connectivity and rigidity compared to those based on either difunctional or multiple aromatic core monomers. That design rule is applied here to hyperbranched polyurethane (PU) aerogels synthesized from tris(4-isocyanatophenyl)methane (TIPM) and 1,1,1-tris(4-hydroxyphenyl)ethane (HPE) in anhydrous acetone using dibutyltin dilaurate (DBTDL) as catalyst. The resulting materials vary from highly flexible to rigid as the monomer concentration increases. FTIR and 13C solid NMR confirm formation of urethane. SEM shows that the flexible variety is macroporous with a beaded worm-like structure, while the rigid variety is mesoporous and nanoparticulate. Lower-density flexible aerogels are highly porous (92%) with surface area of 132 m2 g-1, while the rigid ones have higher surface areas, up to 256 m2 g-1. Polyurethane aerogels from other triols and diols, e.g., phloroglucinol (POL) and resorcinol (RES), respectively, have also been studied and for similar monomer concentrations shrinkage and bulk density increases.

Keywords

aerogelpolymernanostructure
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1403: Symposium V – Multifunctional Polymer-Based Materials , 2012 , mrsf11-1403-v17-37
Copyright
Copyright © Materials Research Society 2012

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