The physical properties of the copper polyaniline vermiculite intercalation compound [Cu(PANI)-VIC] have been studied by x-ray diffraction, electrical resistivity, and dc-magnetic-susceptibility measurements. Aniline is intercalated into the interlamellar space of Cu-VIC, where the ${\mathrm{Cu}}^{2+}$ ions act as oxidation centers for the polymerization of aniline, forming an insulator of polyaniline. A conductor is achieved by protonation via exposure to HCl gas. Cu(PANI)-VIC exhibits the following electrical properties: (i) ln(ρ)≊1/${\mathit{T}}^{\mathrm{\mu }}$, where μ≊1/3, suggesting a two-dimensional variable-range-hopping conduction mechanism in the range of 50 K≤T≤120 K; (ii) the Poole-Frenkel effect is observed in the range of 50 K≤T≤90 K, since, in an electric field F, ln(σ) is proportional to ${\mathit{F}}^{1/2}$. The dc magnetic susceptibility obeys the Curie-Weiss law above 150 K, with a Curie-Weiss temperature of FTHETA=12 K. The polymeric unit cell in Cu(PANI)-VIC contains one ${\mathrm{Cu}}^{2+}$ ion per two-ring protonated polyaniline, which may orient along the diagonal in the in-plane rectangular structure (a×b) with a=5.33 Å and b=9.26 Å. The dc-magnetic-susceptibility data show that 56% of ${\mathrm{Cu}}^{2+}$ ions are linked with protonated polyaniline. The in-plane structure of Cu(PANI)-VIC is formed of two types of commensurate structures having (a×b) and (3a×b) unit cells, where u is the number ${\mathrm{Cu}}^{2+}$ ions per unit cell of (a×b). The u=1-type structure contains the conductive polyaniline, while the u=4/3-type structure does not.

• Received 29 June 1992

DOI:https://doi.org/10.1103/PhysRevB.47.13664