Octyl-thiophene

A tetraruthenated porphyrin was electropolymerised onto glassy carbon and used to catalyse the oxidation of nitrite to nitrate, with the resultant current giving a selective measure of the concentration of nitrite ion [81]. As an alternative method, soluble poly(3-octyl thiophene) [82] was cast along with tridodecylmethylammonium chloride onto glassy carbon, to give electrodes with superior selectivity over PVC-based membranes to lipophilic ions such as bromide or nitrate. 

Figure 11. 200 MHz 1H NMR spectrum of 5-methyl-2-(l,-oxo-3,7 -dimethyl-octyl)thiophene.

Poly(2,7-(9,9 -di-n-octylfluorene)-3,6-benzothiadiazole). t Poly(3-octyl)thiophene regioreguiar but HT content not cited. 

Polymer photodetectors, on the other hand, are rapidly becoming feasible for commercial applications. Recently a full-color optical scanner was made from an array of 102 polymer photodiodes [315]. Poly(3-octyl thiophene), P30T, was chosen as the polymer for the scanner because its band gap is 1.9 eV (650 nm), which allows it to absorb light at all wavelengths in the visible spectrum. Red, green, or blue filters were placed in front of the photodiodes to make them sensitive to a particular color. This prototype scanner demonstrates the feasibility of making large two-dimensional full-color detector arrays on a wide variety of surfaces. 

FIGURE 5.2.3 Two-dimensional grazing incidence x-ray diffraction patterns of poly(3-octyl thiophene) thin films cast on SiOj/Si substrates with various solution processing techniques from different solvents (a) chloroform (CHCI3) (b) toluene (c) tetrahydrofuran (THF) (d) methylene chloride (CH2CI2). (From Yang, H., unpublished data, 2006. With permission.)... 

Poly-3-octyl thiophene with PP, PVC, PS, PE, EVAc, PVC/ABS, etc., and dopant, e.g., Ij PANI with dodecylbenzene sulfonic acid heat treated, then mixed with either PS, PE, PS, ABS or PP blends were formed into desired shapes, and used either as EMI or ESD materials Kokkonen et al., 1994... 

By contrast, the ECP must have conjugated rigid-rod macromolecules. Several such polymers show high electrical conductivity (usually after doping), viz. polyacetylene (PAc), polyaniline (PANI), polypyrrole (PPy), polyparaphenylenes (PPP), or poly-3-octyl thiophene (POT). The resins are expensive, difficult to process, brittle and affected by ambient moisture, thus blending is desirable. For uniaxially stretched fibers the percolation threshold is 1.8 vol%, hence low concentration of ECP (usually 5-6 vol%) provides sufficient phase co-continuity to ascertain conductivity similar to that of copper wires (see Table 1.79). 

Random co-polymers of methyl and octyl thiophenes were prepared electrochemically by Pei et al. [101] with the purpose of checking the thermal dedoping behaviour of such materials, based on the idea that long and short side chains simultaneously present should create additional space for the dopant molecules. It was found that the doping stability is intermediate between that of the parent polymers, and depends on the composition. Sfructural studies of the materials were not performed. 

Fell et al. [72] studied the correlation between the composition and the strucmre of co-polymers of hexyl and octyl thiophenes, obtained by chemical polymerization with FeCl3, and performed also a comparative study of the corresponding polymer mixtures [71 ]. The co-polymers, P[(HT) x(OT) ], of molar fractions x = 0, 0.3, 0.5 and 1.0, were cast from chloroform solutions into films that could be stretch oriented, and were also obtained in the form of stretched threads. Diffraction studies showed patterns very similar to those from the pure polymers, with well developed direction dependent Bragg diffraction peaks, and direction dependent diffuse features. Whereas the b-axis parameter stayed almost constant throughout the series, the a-axis parameter was found to vary linearly with the molar fraction x. 

Figure 8.15. M, M" as a function of frequency for three poly(octyl-3 thiophene) based samples of vanous conductivity, (a) Mixture of poly(3-octylthiophene) (20% ) in poly(ethyl-vinylacetate), <7dc = 6 x 10 S cm (b) Mixture of poly(3-octyl thiophene) (10% ) in poly(ethyl-vinylacctate), erdc = 5 x 10 " S cm (c) poly(3-octylthiophene), = 10 S cm...

The H and C NMR analysis of poly(3-octyl thiophene) give a good evaluation of the ratio between head-to-head and head-to-tail sequences [158], This estimation is important because the presence of a head-to-head sequence is going to induce a sterical hindrance, with a slight rotation of two neighbouring cycles as a consequence of this constraint. The effect of this rotation is a weaker overlap of n orbitals and therefore a weaker delocalisation of electrons along the chain, which leads to an uneasier conduction. 

Until today such polymers have been described as soluble [55]. In fact the term is not correct for most representatives of this category they are only soluble in neutral, non-conductive form (e.g. poly-3-octyl thiophene), i.e. not in a form converted by means of a redox... 

In typical work of Yu et al. [29], the arrays were fabricated on ITO glass substrates. The ITO glass layer was patterned by photolithography into perpendicular rows of electrode strips (width 450 pm, spacing 185 pm). The polymer film, a blend of poly(3-octyl thiophene) and fullerene PCBM[6,6] (see Section 6.3), was spin-cast onto the substrate. 

T. Taka, EMI Shielding Measurements on Poly(3-Octyl Thiophene) Blends. Synth. Met. 1991,41,1177-1180. 

Fig. 27. SAXS intensity patterns of poly(3-octyl thiophene) as a hmc-tion of temperature during heating at a rate of 2°cymin [164]. The inset (adapted from S.-A. Chen and J.-M. Ni, Macromolecules 25,6081 (1992)) shows the X-ray pattern at room temperature over a wider scattering vector q regime, where the second- and third-order peaks become resolvable.

---