Composites of Maghnite-H, a Montmorillonite sheet silicate clay, exchanged with protons, and Poly(3,4-ethylenedi oxythiophene) (PEDOT) were prepared by in situ chemical polymerization of the 3,4-ethylenedioxythiophene, without the use of solvent or oxidant. The effect of changing monomer/clay ratio was studied and the resultant composite struc tures were characterized by Inferred spectroscopy, 27Al and 13CSolid-State NMR spectroscopy, scanning electron mi croscopy and powder X-ray diffraction. All analyses are consistent with a structure were the polymer is (partially) in tercalated into the clay structure, which in favourable cases lead to exfoliation. The presence of the clay in the polymer leads to a desired increase in thermal stability as witnessed by thermogravimetry .
Polythiophene and its derivatives have attracted much interest over recent decades due to exceptional electrical properties and their environmental stability [1-6]. From this class of conducting polymers with conjugated π- bonds, especially poly 3,4-ethylenedioxythiophene (PEDOT) possess unique properties such as high environmental stability [7,8] and a small band gab (1.6 - 1.7 eV); a direct consequence of the electron donation properties of the ether functionality [
In this article, we examine the use of Maghnite-H+ (MagH), a Montmorillonite sheet silicate, in the synthesis of composites with PEDOT. The choice of MagH is based on related work where it acts as a catalyst of cationic polymerization of vinyl [34-37] and heterocylic [38-42] monomers. Here the synthesis takes place in a one pot reaction between the clay and the monomer without the use of solvent or oxidant. Specifically, we examine the effect of the relative ratios between the monomer and the clay on the intercalation and possible exfoliation of the clay structure.
MagH was prepared using the method of Belbachir et al. [
All reactions were performed using the same methodology described below, with however, a variation of time, for the 10% by weight of MagH/monomer 24 h reaction and for 50% 96 h reaction. The reaction times and relative concentration were altered according to
Hybrides from 10% by weight of MagH/monomer reaction mixtures.
In a round bottom flask fitted with a condenser was mixed 1 g (0.007 mol) EDOT and 0.5 g MagH previously dried at 100˚C overnight. The mixture was heated to 90˚C, under constant stirring using a magnetic stir bar. Upon the addition of the MagH a colour change was witnessed from clear over red to brown before finally becoming dark green. After 24 h of heating a back solid was formed, and the suspension was cooled to room temperature. Residual unreacted monomer and shorter solvable oligomeres were removed by washing with dichloromethane. The residual black solid (the hybrid material) was dried at 60˚C overnight to remove any solvent traces. (Calculate a real yield based on incorporated polymer relative to the initial amount). The amount of incorporated polymer was determined to 21 m/m-% based on the mass gain.
Infrared spectra (400 - 4000 cm−1) were collected from samples ground with dry KBr and pressed into pellets. Spectral peaks around 2350 cm−1 stem from residual CO2 in the beam path. 13C and 27Al Solid state NMR was preformed using a BRUKER ASX 400 CP-MAS. Thermogravometric analysis (TGA) was performed on a Standon Redcroft STA780 thermal analyser and in air at a heating rate of 5 deg/min within the temperature range of 25˚C - 1000˚C. The powder X-ray diffraction (XRD) patterns of the samples were recorded using Philips XRD X’PERT PRO II diffractometer (2 goniometers, Montpellier, French) using Cu-Kα radiation and (λ = 1.5404 Å) produced at 40 kV and 40 mA. Scanning electron microscopy micrographs where collected on a Hitachi S-2600N with a 25 kV working potential, a working distance of 7.0 - 7.4 mm and a SE detector.