5 years ago

Effect of the graft density of cellulose diacetate-modified layered perovskite nanosheets on mechanical properties of the transparent organic–inorganic hybrids bearing covalent bonds at the interface

Kenji Shintani, Satoru Sato, Yoshiyuki Sugahara, Naokazu Idota, Takashi Nishino


Transparent organic–inorganic hybrids with a whitish colour were prepared from cellulose diacetate (CDA) nanosheets derived from Dion–Jacobson-type ion-exchangeable layered perovskite HLaNb2O7·xH2O (HLaNb) to prepare CDA-based hybrids bearing covalent bonds between HLaNb nanosheets and CDA matrices for improved mechanical properties. An n-decoxy derivative of HLaNb (C10_HLaNb) was exfoliated in acetonitrile by ultrasonication. TEM and AFM images revealed that C10_HLaNb was exfoliated into individual nanosheets. In order to explore the local environment around HLaNb nanosheets, a very small amount of CDA was reacted with a C10_HLaNb nanosheet dispersion [molar ratio COH:(NbOH + NbOC10H21) = 4:1] at 80 °C, and solid-state 13C NMR with cross polarization and magic angle spinning techniques showed that an alcohol-exchange-type reaction was proceeded to graft the CDA chains to the HLaNb nanosheets via new Nb–O–C covalent linkages. The CDA-based hybrids were prepared by dispersing 5 mass% of HLaNb nanosheets in CDA and subsequent heating at 80 °C for 1–7 days to cause a grafting reaction, and the product prepared by a 1-day grafting reaction exhibited improved mechanical properties compared to neat CDA; the Young’s modulus, tensile strength and toughness increased by 18, 34 and 78%, respectively. The mechanical properties deteriorated with further extension of the reaction period, however. In addition, a hybrid film prepared by mixing CDA and a C10_HLaNb nanosheet dispersion exhibited only a slight improvement in mechanical properties. These results clearly indicate that formation of an appropriate number of Nb–O–C bonds at the nanosheet/CDA interfaces is effective for improving mechanical properties.

Publisher URL: https://link.springer.com/article/10.1007/s10570-017-1475-7

DOI: 10.1007/s10570-017-1475-7

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