Synthesis of calcium silicate hydrate/polymer complexes: Part I. Anionic and nonionic polymers
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Synthesis of calcium silicate hydrate/polymer complexes: Part I. Anionic and nonionic polymers Hiroyoshi Matsuyamaa) and J. Francis Young Center for Advanced Cement-Based Materials, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (Received 19 October 1998; accepted 20 May 1999)
High molecular weight anionic polymers have been incorporated into the calcium silicate hydrate (C–S–H) structure during precipitation of quasicrystalline C–S–H from aqueous solution. The anionic polymers studied were poly(methacrylic acid), poly(acrylic acid), and the sodium salt of poly(vinyl sulfonic acid). Expansion of the interlayer spacing coupled with high-carbon contents confirmed that the polymers intercalated between the layers. D-gluconic acid behaves similarly. Intercalation characteristics strongly depended on both the type of polymer and Ca/Si molar ratio of C–S–H; intercalation reached a maximum at an initial Ca/Si ⳱ 1.3 in all cases. Poly(vinyl alcohol) was the only nonionic polymer among those studied that was incorporated into C–S–H. Evidence for interlayer intercalation is less definite. The C–S–H/polymer complexes were examined by Fourier transform infrared spectroscopy, 29 Si nuclear magnetic resonance magic angle spinning, and 13C cross-polarization, magic angle spinning nuclear magnetic resonance spectroscopy.
I. INTRODUCTION
The intercalation of organic molecule of low molecular weight, such as n-alkylamines, alcohols and alcohol esters, is well established in clays.1 Although the steric and entropic effects might be expected to preclude the entry of macromolecule into a preformed layer structure, clay-polymer complexes have been extensively studied2 because of the potential of polymers as aggregating agents for clay. Clay–anionic polymer interactions have been studied extensively2–6 because of the fact that polyanions can flocculate clay suspensions by forming interparticle bonds. However, anionic polymers most likely may be attached to the edge surfaces of the clay crystals in clay/anionic polymer complexes,2 because anionic polymers do not penetrate the interlayer space of clay.3–5 The interactions of nonionic polymers, such as poly(vinyl alcohol),7,8 poly(ethylene glycol),9 and (polyvinyl pyrrolidone)2 have been reported, although in many cases only surface adsorption occurred. Clay minerals and certain cement hydration products share commonality in the formation of layer-structured crystals. The intercalation of low molecular weight organic molecules into the layers of tetracalcium aluminate hydrate (4CaO4Al2O3 ⭈ 13H2O), which is one product of hydrated portland cement, was reported by Dosch.10 A variety of compounds, such as alcohols, glycols, amines, fatty acids, amino acids, dicarboxylic acids, and mercap-
a)
On leave from Asahi Chemical Co. Ltd. J. Mater. Res., Vol. 14, No. 8, Aug 1999
http://journals.cambridge.org
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tans were intercalated. A recent study11 showed that it was possible to intercalate poly(vinyl alcoho
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