Abstract
Natural montmorillonite, fractionated from bentonite produced in Yamagata, Japan, was ion-exchanged for NH +3 −(CH2)11−COOH, NH +3 −(CH2)5−COOH, Al3+, Cu2+, Mg2+, Co2+, Li+, K+ and H+. The mixtures of the ion-exchanged montmorillonite and ε-caprolactam were heated at 263°C in glass ampoules for various periods. The intercalated compounds before and after the heating were examined by X-ray powder diffraction, DSC and GPC. Although ε-caprolactam was not polymerized without montmorillonite, it was polymerized at 263°C in the presence of montmorillonite. The polymerization rate varied with the interlayer cations in the order of NH +3 −(CH2)11−COOH>Al3+>NH +3 −(CH2)5−COOH>H+>Cu2+>Mg2+>Co2+>Li+>K+. After heating at 263°C for 5 h, the mean number-average molecular weight was about 1.5×104. Although the interlayer distance of NH +3 −(CH2)11−COOH type montmorillonite/ε-caprolactam compound increased from 2.85 nm to 4.90 nm by heating at temperatures above the melting point of ε-caprolactam, those of other compounds were not changed. After heating at 263°C, an intercalated compound of montmorillonite and 6-polyamide, whose interlayer distance was more than 10 nm, was obtained. It is concluded that montmorillonite acts as a Brönsted acid and initiates the open ring polymerization of ε-caprolactam and that the driving force of swelling is the polymerization energy.
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Fukushima, Y., Inagaki, S. Synthesis of an intercalated compound of montmorillonite and 6-polyamide. Journal of Inclusion Phenomena 5, 473–482 (1987). https://doi.org/10.1007/BF00664105
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DOI: https://doi.org/10.1007/BF00664105