Negative to positive magnetoresistance transition in functionalization of carbon nanotube and polyaniline composite

Abstract

Electrical resistivity and magnetoresistance(MR) in polyaniline(PANI) with carbon nanotube(CNT) and functionalized carbon nanotube(fCNT) composites have been studied for different weight percentages down to the temperature 4.2K and up to magnetic field 5T. Resistivity increases significantly in composite at low temperature due to functionalization of CNT compared to only CNT. Interestingly transition from negative to positive magnetoresistance has been observed for 10wt% of composite as the effect of disorder is more in fCNT/PANI. This result depicts that the MR has strong dependency on disorder in the composite system. The transition of MR has been explained on the basis of polaron-bipolaron model. The long range Coulomb interaction between two polarons screened by disorder in the composite of fCNT/PANI, increases the effective on-site Coulomb repulsion energy to form bipolaron which leads to change the sign of MR from negative to positive.

Large Room‐Temperature Magnetoresistance in a High‐Spin Donor–Acceptor Conjugated Polymer

“…Comparable changes in MR with respect to temperature have been observed in other organic systems, [ 39–42 ] and several mechanisms have been proposed to explain these magnetic field‐dependent effects. [ 43–45,46–50 ] In the open‐shell DA CP, both positive and negative MR can be explained by the VRH model.…”

Magnetic field driven dielectric relaxation in non-magnetic composite medium: A low temperature study

“…The degree of functionalization is varied by changing the duration (hour; denoted by 'h'; we have prepared particularly 6 h, 48 h and 96 h) of functionalization using acids [10]. Composites of 10 wt % MWCNT and fMWCNT with PANI are prepared by following the in-situ polymerization technique [11]. In this process, we added 2 ml aniline monomer with 40 ml 1 M HCl and required amount of MWCNT/fMWCNT to make 10 wt percentage composites and sonicated for 1 h to obtain well dispersed suspensions.…”

“…X-ray photo emission spectroscopy (XPS) measurement indicates that chemical functionalization attaches different functional groups (-C--O, -COOH) on the surface of MWCNT and their percentage varies with the variation of degree of functionalization [10,11].…”

Magnetic field driven dielectric relaxation in non-magnetic composite medium: a low temperature study

“…14 The composites of MWCNT and PANI are prepared by using in-situ polymerization technique which is explained in our previous reports. 15 The samples were made in the form of pallet with radius 10 mm and thickness 1.35 mm. The dielectric measurements are performed keeping the samples in between two silver plates, and put inside the Janis cryostat equipped with superconducting magnet.…”