The synthesis of a copolymer derived from poly(3-hexylthiophene), one of the monomers bearing an aniline group, is described. Like the homopolymer, this copolymer is able to functionalise carbon nanotubes by...

We report on transport measurements in monolayer MoS2 devices, close to the bottom of the
conduction band edge. These devices were annealed in situ before electrical
measurements. This allows us to obtain good ohmic contacts at low temperatures, and to measure
precisely the conductivity and mobility via four-probe measurements. The measured effective
mobility up to μeff = 180 cm2/Vs is among the largest obtained in CVD-grown MoS2 monolayer
devices. These measurements show that electronic transport is of the insulating type for σ≤ 1.4e2/h
and n ≤ 1.7×1012 cm-2, and a crossover to a metallic regime is observed above those values. In
the insulating regime, thermally activated transport dominates at high temperature (T > 100 K).
At lower temperatures, conductivity is driven by Efros-Schklovkii variable range hopping in all
measured devices, with a universal and constant hopping prefactor, that is a clear indication that
hopping is not phonon-mediated. At higher carrier density, and high temperature, the conductivity
is well modeled by the Boltzmann equation for a non-interacting Fermi gas, taking into account
both phonon and impurity scatterings. Finally, even if this apparent metal-insulator transition can
be explained by phonon-related phenomena at high temperature, the possibility of a genuine 2D
MIT cannot be ruled out, as we can observe a clear power-law diverging localization length close to
the transition, and a one-parameter scaling can be realized.

The functionalization of carbon nanotubes by polymers necessitates two steps, first their modification by oxidizing them or by covalently attaching small compounds to them, then the growth of the polymer chains from these anchors or their grafting onto them. In order to better control the process and the rate of functionalization, we develop polymers able to covalently react with the carbon nanotubes by their side chains in one step. We describe the synthesis of a copolymer of dodecylthiophene and its analogue bearing an aniline group at the end of the dodecyl side chain. This copolymer can functionalize single-walled carbon nanotubes (SWNTs) non-covalently and disperse more SWNTs than its hexyl analogues. UV-Vis and fluorescence spectroscopies show that in these non-covalent hybrids, the polymer forms p-stacked aggregates on the SWNTs. The non-covalent hybrids can be transformed into covalent ones by diazonium coupling. In these covalent hybrids the polymer is no longer p-stacked. According to Raman spectroscopy, the conformation of the poly(3-hexylthiophene) backbone is more ordered in the non-covalent hybrids than in the covalent ones.