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We introduce a novel method for fabricating nano- and microscale polyaniline particles containing an entrapped oxidoreductase enzyme for use in biosensing applications. This facile process utilizes...

Nanocomposites of conducting polyaniline (PAN) with inorganic Na+−montmorillonite (MMT) clay were synthesized by the emulsion polymerization method. The dodecylbenzenesulfonic acid (DBSA) was used for both dopant and emulsifier. Analyses of X-ray diffraction patterns demonstrated that conducting PAN-DBSA was intercalated between inorganic clay layers at the nanoscale level (

Temperature-dependent direct current (dc) and microwave (mw) conductivity, σdc and σmw, electron paramagnetic resonance (EPR), and mechanical properties of sulfonated polyaniline/poly(p-phenylene terephthalamide) (SPAN/PPD-T) composite fibers are presented. Tenacity and modulus are in the range of 15 and 270 g/denier (gpd), respectively, for 30 wt % (weight percent prior to sulfonation) SPAN composite fiber. Room-temperature dc conductivity σRT varies from 7.8 × 10-5 to 1.5 × 10-1 S/cm, increasing with increasing wt % polyaniline (PAn) and spin stretch factor (SSF). The temperature-dependent conductivity follows the quasi-one-dimensional variable range hopping (Q1D VRH) model: σdc(T) = σ0 exp [−(T0/T)γ], where γ ∼ 0.5 and σ0 is a constant. T0 is 4.3 × 104 to 2.9 × 104 K, respectively, for 10 and 30 wt % PAn. The σmw of the fiber with the same SSF 7.0 but a 30/70 PAn/PPD-T ratio shows a typical temperature dependence for materials for which the hopping conduction mechanism is dominant. There is a larger d...

The results of temperature-dependent dc conductivity, EPR magnetic susceptibility, and X-ray photoelectron spectroscopy (XPS) experiments are compared for electrochemically and chemically synthesized polypyrrole (PPy) samples. For chemically synthesized PPy samples soluble in organic solvent with large size dopants such as dodecylbenzenesulfonic acid (DBSA) or naphthalenesulfonic acid (NSA), dc conductivity (σdc) is ≤0.1 S/cm at room temperature, and its temperature dependence [σdc(T)] shows strong localization behavior, while σdc(T) of the electrochemically synthesized PPy samples doped with hexafluorophosphate (PF6) is in the critical or the metallic regime. The density of states of chemically prepared PPy−DBSA samples is less than one-fourth that of electrochemically synthesized PPy−PF6 samples. The g values and temperature dependence of the line width obtained from EPR experiments show that the paramagnetic signals in both electrochemically and chemically synthesized PPy samples are mainly due to the ...

Highly sulfonated polyaniline prepared via a synthetic scheme using leucoemeralding base (LEB−SPAN) has been studied using X-ray photoelectron spectroscopy (XPS). A sulfonation level (S/N ratio) as high as 0.80 ± 0.10 has been revealed in XPS analysis, agreeing well with the element chemical analysis results (∼0.78). This contrasts to an S/N ratio of 0.50 for SPAN made via the earlier reported synthetic method. The detailed S 2p and N 1s peak analyses both show that the oxidation level is ∼50%, implying a better thermal stability of emeraldine oxidation state over those of leucoemeraldine and pernigraniline oxidation states. These XPS analysis results are supported by UV−vis and FT-IR analysis results. The method of resolving 2p3/2 and 2p1/2 peaks in the S 2p spectrum is discussed.

The results of the temperature dependence of dc conductivity, microwave dielectric constant, X-ray diffraction, EPR, and NMR experiments are reported for chemically synthesized polypyrrole films soluble in organic solvents. The temperature dependence of dc conductivity of these systems follows the three-dimensional variable range hopping model. The slope of the temperature dependence of dc conductivity varies with dopants and solvents used. Room temperature dc conductivities are in the range of ∼0.2−0.01 S/cm, and the localization lengths are estimated as ≤10 A, which indicates a relatively strong localization of charge. The results of microwave dielectric constant experiments support the strong localization behavior. The X-ray diffraction studies show that soluble polypyrroles are amorphous. From electron paramagnetic resonance experiments, the density of states of polypyrrole doped with naphthalenesulfonic acid in m-cresol solvent is estimated as ∼0.107 states/(eV ring). We obtain the result that the sy...

It is shown that the degree of aggregation of emeraldine base polyaniline (EB) in NMP solution significantly increases as the polymer concentration increases. The solution properties of EB are found to have a dramatic impact on the crystallinity of the resulting cast films

We report the results of transport (temperature dependent dc conductivity, thermoelectric power, and microwave frequency conductivity, and dielectric constant) and structural studies for hydrochloric acid doped polyaniline (PAN-HCl) fibers 4-fold stretched at 300, 350, and 400 "C and the results of dc conductivity for its methyl ring-substituted derivative, poly(o-toluidine) (POT-HCl) fibers. For the PAN- HCl fibers, with increasing stretching temperatures, the system shows greater localization, as indicated by the decreasing conductivity with stronger temperature dependence and decreasing microwave dielectric constant with weaker temperature dependence. This is in accord with the observed decreasing crystallinity with increasing processing temperature. The interrupted metallic strands model is used to account for the microwave results assuming that the size of the metallic regions increases linearly with temperature. For the POT-HC1 fiber, the conductivity is similar to that for the POT-HCl powder. When the fiber is stretched 3-fold, the conductivity increases almost 1 order of magnitude while the temperature dependence changes only slightly, in agreement with the short localization length in the system.

The spectroscopic (UV-visible, IR, XPS, and Raman) characterization and morphological studies of 84 Kr + -implanted conducting rigid-rod poly(p-phenylenebenzobis(thiazole)) (PBZT) and poly(p-phenylenebenzobis(oxazole)) (PBO), pseudo-ladder poly(p-2,5-dihydroryphenylene)benzobis(thiazole)) (DPBT) and ladder poly(benzimidazobenzophenanthroline) (BBL) polymers at a dose of 4×10 16 ions/cm 2 and an energy of 200 keV. are reported. All showed similar optical properties after implantation, namely, broad metallic absorption

Many materials, especially polymers, have a substantial volume fraction without crystalline order. Though these regions are often termed amorphous, they frequently have specific local order. We describe and use here a method based on a non-energy-dispersive X-ray diffraction technique to obtain good quality interference functions and, by Fourier transform, radial distribution functions of the amorphous structures of polymers. We apply this approach to a family of electronic polymers of current interest, poly- aniline, comparing polyaniline emeraldine base (EB-11 prepared from NMP solution), polyaniline emeraldine salt (ES-I1 prepared by doping EB-I1 with HCl), and dedoped polyaniline ES-I1 salt. From these data, it is found that amorphous EB-I1 and ES-I1 show a local chain array resembling that exhibited by the recently determined EB-I1 and ES-I1 crystalline structures, respectively. Thus the order in "crystalline" and 'amorphous" regions is locally similar but differs by the spatial range of structural correlations, a feature likely due to the amount of conformational defects. Dedoped polyaniline ES-I1 salt has an increased in- terchain disorder through a local structural order intermediate between those of amorphous EB-I1 and ES-11. These studies demonstrate the importance of sample history in evaluating the physical properties of poly- aniline and provide a structural origin for memory effects previously reported.

We investigated the structural features of the polyaniline derivative-poly-ortho-toluidine (POT). In the base form POT is amorphous, with an x-ray diffraction pattern similar to that of emeraldine base EB-I. We estimate from the position of the broad peaks in the amorphous pattern that the interchain spacing is larger in POT-EB than in EB-I. POT hydrochloride is partially crystalline with a diffraction pattern resembling that of emeraldine hydrochloride ES-I. Analysis of the data shows that the crystalline part of POT hydrochloride adopts the ES-I like structure, with increased zig-zag angle of the polymer chain and larger interchain spacing, together with an increased disorder, possibly due to defects in the stacking of polymer chains caused by the bulky -CH3 groups. Structure and percent crystallinity evolve with doping level in the same way as in the EB-I - ES-I emeraldine system. These structural results correlate with difference in the electronic properties of the POT-ES as compared with ES-I. In particular, the 103 decrease in room temperature conductivity of POT-ES compared to ES-I and concomitant localization of conduction electrons in POT-ES as compared with PAN-ES is attributed to the increased separation and decreased coherence between polymer chains leading to quasi-dimensional localization of conduction electrons.

It is demonstrated that emeraldine base polymer films can be processed to form strong oriented materials by maintaining the polymer under stress while the temperature is raised toward the glass transition temperature. After the orientation process, the polymer chains are significantly oriented parallel to the stretching direction. These stretch-oriented materials can then be treated with protonic acids to form emeraldine salt. These salt polymers are oriented to a lesser degree than the starting emeraldine base form. The oriented emeraldine base and emeraldine salt polymers show enhanced optical and electrical properties

The structure and protonation level of sulfonated polyaniline as well as the chemically synthesized emeraldine base and its chloride salt have been investigated. The XPS results indicate that ∼ 50% of the phenyl rings of the sulfonated polyaniline have a hydrogen atom substituted by a -SO 3 H group. Approximately 50% of the nitrogen sites are protonated in this self-doped conducting polymer. The protonation level remains unchanged upon exposure to high vacuum at room temperature. In contrast, emeraldine hydrochloride undergoes partial deprotonation and probably reduction as well under high-vacuum conditions

Aggregation in the nondoped polyaniline, emeraldine base (EB), as observed by GPC in a N-methyl-2-pyrrolidinone (NMP) solution, was found to be closely related to the fraction of the imine nitrogen atoms in the nondoped polymer, i.e., to the oxidation state of the polymer. As EB was reduced to leucoemeraldine base (LEB), the degree of aggregation was significantly reduced. The results of gel permeation chromatography (GPC) and infrared studies suggest that the aggregation of the polymer is due to interchain hydrogen bonding between the imine and amine nitrogen sites on adjacent polymer molecules. The degree of hydrogen bonding and, thus, aggregation found in the polymer is greatly affected by solvents, LiCl, and the oxidation state of the polymer.

It is shown that thin films of camphorsulphonic acid-doped polyaniline spun from chloroform or NMP have a coil-like conformation and shorter conjugation length while those films spun from m-cresol have an expanded coil-like conformation and longer conjugation length. The coil-like conformation can be irreversibly converted to the expanded coil-like conformation by exposure to m-cresol vapor at room temperature