Diffusion poly thiophene

Poly thiophene, PTP, and polypyrrole, PPR, blends with PS and PC were prepared by Wang et al. [1990] by thiophene or pyrrole electrochemical polymerization using electrodes coated with PS or PC hlms. The thiophene or pyrrole diffuses into the fihn and polymerizes in-situ in the film. Threshold conductivity occurs at 18 wt% for both conducting polymers in PS. Lower levels exist for PTP (12 wt%) and PPR (7 wt%) in PC. Miscibility of PPR/PC is attributed to the lower threshold limit as phase separated blends would be expected to have higher values. Previous studies with polyacetylene/PS blends reported threshold conductivity at 16 wt% polyacetylene [Aldissi and Bishop, 1985]. 

The host structure must provide an environment of restricted geometry, sometimes preventing the reticulation of the polymeric chains. Chains of poly(aniline), poly(pyrrole) and poly(thiophene) and others have been encapsulated by many forms of host [10-13] (see Table 8.1). Two routes are commonly used for this (i) the monomer is dissolved in an organic solvent (or in aqueous solution in its protonated form), and by diffusion and/or charge-exchange processes, the monomer is encapsulated in the cavities of a host, followed by oxidation with ammonium persulfate or another oxidant in situ polymerization), (ii) a host having oxidant ions, such as Cu(II) or Fe(III) is exposed to monomer vapors and then acid vapors [10-11]. 

One of the first CPs to be studied as a modified electrode was P(Py), at which the electrochemistry of ferrocene (FeCp2) was studied [55]. This FeCp2 system (E° +0.42 V vs. SCE) showed near ideal reversible electrochemical behavior, with proportional to indicating diffusion limited processes, cathodic/anodic peak current ratios of near unity, and cathodic/anodic peak separations close to 70 mV. More recently, poly (bithiophene) modified electrodes have been used to monitor the electrochemistry of FeCp2 as well as / -benzoquinone, and to probe the semiconducting behavior of this CP [56]. Ferrocene appears popular as a near-reversible probe material for CP-modified electrodes, having been studied with poly(thiophene) and other CP modified electrodes as well [57]. 

Encapsulated CPO in block copolymer polymersomes assembled from polystyrene-b-poly(L-isocyanoalanine-(2-thiophene-3-yl-ethyl)amide) The oxidation of two substrates by the encapsulated CPO was studied while the oxidation of pyrogallol was limited by diffusion into the polymersome, the rate-limiting step for the oxidation of thioansiole was the turnover by the enzyme [46]... 

Diffraction data for the alkoxy-substituted materials are scarce. For PMEEMT x-ray diffraction patterns were recorded [44] at two temperatures, room temperature and 150°C, showing in both cases three to four rather broad peaks on a diffuse background. The peaks correspond to interplanar distance d= 17.8 A, 7.0 A, 3.8 A and 2.4 A, the latter two being close to two values also found for PATs as the 6-axis parameter and a diffuse feature at 0 = 2.6 A related to the main chain periodicity. It is remarkable that the diffraction pattern survives heating to 150"C, which is above the thermochromic transition for PMEEMT. A recent diffraction study of poly methanol-thiophene) prepared electrochemically showed only broad amorphous scattering around 0= 1.4 A [94],... 

With the development of 3-(co-bromoalkyl)thiophenes, several crown ether functionalized PTs have been synthesized by Bauerle and coworkers. Electropolymerization was performed on mono-, bi-, and terthiophene monomers 65-67 substituted with pendant 12-crown-4 receptor tethered with alkyl chains [175-177]. While electropolymerization failed with 65, compounds 66, 67, and 68 were easily electro-polymerized and the chemosensing properties of the polymers were analyzed. Cyclic voltammetric analysis showed that addition of increasing amounts of Li, Na, or produces a positive shift of the oxidation potential of poly(66, n=5), while this effect is less pronounced for poly(67). On the other hand, whereas the CV of poly(68, n=5) is strongly affected by the presence of alkali ions, the lengthening of the alkyl spacer in poly(68, n = 10) produces a complete loss of ion sensitivity. Optical and spectroelectrochemical experiments revealed that the changes in electronic properties were due to hindered diffusion of the counteranions into the film during polymer oxidation [177]. 

Domain sizes and compositional heterogeneities in poly-3-hexyl-thiophene phenyl C61-butyric acid methyl ester bulk heterojunction thin films are studied by spin diffusion Solid-state Si, Al, C,... 

Polymerization can also be induced by the tip via an oxidation reaction. This woridng mode was demonstrated by Heinze and cowoikers (122). The monomer 2,5-bis (1-methyl-pyrrol-2yl)-thiophene (NSN) was first deposited on ITO by thermal evaporation. The micropatteming was performed in an aqueous solution containing bromide. The tip oxidizes bromide to bromine, which diffuses to the surface and reacts with the monomer to form patterns of poly-NSN. The remaining monomers were removed by organic solvents. This technique can also be applied to nonconducting substrates. 

In LiC104 supporting electrolyte In TBAF supporting electrolyte Poly(methyl thiophene) in CH3CN Polyphenylene in CH3OH + NaOH Organic species in the diffuse layer Reduction of tetracyanoethylene in CH3CN... 

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