Preparation of a nanostructured organoceramic and its reversible interlayer expansion
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Preparation of a nanostructured organoceramic and its reversible interlayer expansion Phillip B. Messersmith Division of Biological Materials and Department of Biomedical Engineering, Northwestern University, Chicago, Illinois 60611
Paul Osenar Department of Materials Science and Engineering and The Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
Samuel I. Stuppa) Departments of Materials Science and Engineering and Chemistry, Materials Research Laboratory, and The Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (Received 25 May 1998; accepted 10 September 1998)
We described previously the liquid phase synthesis and characterization of a nanostructured composite from an aqueous solution containing organic polymer and inorganic ions [J. Mater. Res. 7, 2599 (1992)]. The nanocomposite, termed an organoceramic, consisted of poly(vinyl alcohol) chains intercalated between the principal layers of a hydrated calcium aluminate ceramic. A key structural feature of the organoceramic is the polymer-induced expansion of the interlayer spacing by ˚ compared to the unmodified ceramic. In this paper, we describe approximately 10 A the synthetic scheme that favors organoceramic formation and prove the existence of intercalated polymer by observation of reversible interlayer expansion and contraction in response to changes in ambient humidity. This property is unique to the organoceramic and is not observed in the unmodified calcium aluminate ceramic.
Nanostructured composites consisting of layered inorganic solids and organic polymers have been widely investigated in recent years due to their interesting mechanical, thermal, optical, magnetic, and barrier properties.1 Several approaches to the synthesis of layered nanocomposites have been described in the literature, including intercalation polymerization,2–5 delamination of layered solids in a monomer or polymer medium,6–9 intercalation of polymer from the melt,10 and liquid phase synthesis of the nanocomposite from solution.11–16 For many of these synthetic approaches, a guest-host interaction exists between the inorganic and organic components, with a preformed inorganic solid typically serving as host for the organic component. Previously, we described a novel approach to the synthesis of layered nanocomposites through which macromolecules and inorganic layers are assembled in a one-step process from a supersaturated ionic solution containing dissolved polymer.12 Unlike conventional
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Address all correspondence to this author. J. Mater. Res., Vol. 14, No. 2, Feb 1999
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guest-host syntheses, our synthetic strategy relies on the formation of the layered inorganic solid from soluble precursor ions during assembly of the nanocomposite. We successfully employed this approach to synthesize a novel nanocomposite of poly(vinyl alcohol
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