Naveed A. Zaidi

Emeraldine Base Polyaniline as an Alternative to Poly(3,4‐ethylenedioxythiophene) as a Hole‐Transporting Layer

The device physics of bilayer polymer light emitting diodes containing either poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] or ladder-type methyl-poly(p-phenylene) active layers have been determined. The active layer was consistent in thickness and general preparation whilst hole transporting layers spin cast from emeraldine base polyaniline protonated with camphorsulfonic acid, emeraldine base polyaniline protonated with 2-acrylamido-2-methyl-1-propanesulfonic acid, and emeraldine base polyaniline protonated with polystyrene sulfonated acid, in various ratios of polyaniline to counter ion, were used in order to determine how various spin-processible polyaniline layers performed relative to a commercially available polystyrene sulfonated acid doped poly(3,4-ethylenedioxythiophene layer. For poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] light-emitting diodes we observe an improvement in performance when using emeraldine base polyaniline protonated with polystyrene sulfonated acid relative to poly(3,4-ethylenedioxythiophene protonated with polystyrene sulfonated acid, with a maximum device external quantum efficiency of 0.6362 % at a current density of 20.18 mA/cm2.

The resolution of tertiary α-acetylene- acetate esters by the lipase from candida cylindracea

Abstract The resolution of tettiary alcohols using the Candida cylindracea lipase is explored. In particular strategies are deployed to limit nonenzmatic hydrolysis of the tertiary acetate substrates in buffer, such that a full range of the steric requirements and limitations for successful resolutions can be explored.

Enzyme-catalysed condensation polymerization of 11-hydroxyundecanoic acid with lipase from Candida cylindracea

Abstract The enzyme-catalysed condensation polymerization of 11-hydroxyundecanoic acid in hexane with the lipase from Candida cylindracea is reported. Molecular weights up to 35 000 are attained. A time course study of the polymerization process reveals that oligomers are formed relatively rapidly and that these oligomers then condense to generate higher molecular weight polyesters.

The synthesis of (R)-γ-phenyl-γ-(trifluoromethyl)-butyrolactone and (2R,3S)-1,1,1-trifluoro-2-methoxy-2-phenyl-3,4-epoxybutane in homochiral forms.

Abstract (R)-γ-Phenyl-γ-(trifluoromethyl)-butyrolactone (1) and (2R,3S)-1,1,1-trifluoro-2-methoxy-2-phenyl-3,4-epoxybutane (2) have been prepared in high optical purity from the tertiary (S)-(3)-acetate which was resolved using the lipase from Candida cylindracea .

Effect of thermal aging on electrical conductivity of the 2-acrylamido-2-methyl-1-propanesulfonic acid-doped polyaniline fiber

The thermal characteristics of inherently conductive polyaniline (PANi) fiber have been studied using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Fibers show five major weight losses at ∼100°C, 165°C, 215°C, 315°C, and 465°C, which are associated with the removal of moisture, residual solvent, decompositions of the sulfonic acid and degradation of PANi fiber, respectively. The 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA) that dopes the PANi (in fiber form) performs two-stage decompositions. The conductivity of the drawn fibers aged at 50°C, 100°C, 150°C, and 190°C under vacuum for various periods of time decreases, particularly at temperatures higher than 100°C. The reduction in conductivity of the fiber aged at temperatures lower than 100°C is mainly due to the evaporation of the residual solvent (15-20% in the as-spun fiber). Further decrease in conductivity of the fiber aged at temperatures higher than 100°C is caused by the decomposition of the dopant AMPSA. The temperature-dependent conductivity of the fiber was measured at 15 K (-258.5°C) to 295 K (21.5°C). The conductivity of both aged and un-aged fibers is all temperature activated, however, the conductivity of the un-aged fibers is higher than that of the aged fibers. Although a negative temperature coefficient was observed in the temperature range from 240 K (-24.5°C) to 270 K (-3.5°C) for the un-aged fibers, it was disappeared when the fibers were thermal aged at 100°C for 24 h in vacuum oven. These results indicate that the residual solvent trapped inside the fiber enhanced the electrical conductivity of the fibers and its metallic electrical conductivity at temperatures ∼263 K (-10°C).

Electrically conductive PANi multifilaments spun by a wet-spinning process

Electrically conductive polyaniline (PANi) filaments were successfully spun from a spinning solution prepared from the PANi protonated with 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA) in dichloroacedic acid (DCA) as a solvent by a wet-spinning process. The conductivity of the fibre is in a range of 145 (±35) Scm−1 to 1440 (±300) Scm−1, which depends on the orientation of polymer chains. The fibre has a Youngs modulus about 3.2 GPa, and a tensile strength about 0.23 GPa. Thermal analysis by TGA and DSC show that the fibre has five major weight losses at around 100 °C, 165 °C, 215 °C, 315 °C and 465 °C which are associated with the removal of moisture, residual solvent, the decompositions of the AMPSA, and the degradation of the PANi, respectively. The AMPSA in doped PANi performs two-stage thermal decompositions. The conductivity of the fibre was adversely affected by the thermal ageing due to the evaporation of the residual solvent at the temperatures lower than 100 °C and the decompositions of the dopant AMPSA at the temperatures above 100°C. The temperature dependent conductivity of both aged and unaged fibres is thermally activated at the temperatures between 15 K and 295 K. A negative temperature coefficient was observed in the temperature range of 240 K to 270 K for the unaged fibres. This disappeared when the fibres were thermally aged at 100 °C for 24 hours in vacuum. These results indicate that the residual solvent trapped inside the fibre enhances the electrical conductivity of the fibres, and possibly affects the negative temperature coefficient at the temperatures around 260 K.

Polymerisation of 10-hydroxydecanoic acid with the lipase from Candida cylindracea

A polyester of 10-hydroxydecanoic acid 1 has been efficiently prepared by the incubation of the monomer in hexane and 3 A molecular sieves at 55°C with the lipase from Candida cylindracea. The polymer is on average a 52-mer(Mn= 9346 and Mr= 12 065) and has a polydispersity of 1.29.

Hydrolytic resolution of tertiary acetylenic acetate esters with the lipase from Candida cylindracea

The kinetic resolution of a series of tertiary acetylenic acetate esters using the lipase from Candida cylindracea has been explored. Compounds 6c and the trifluoromethyl acetate 6e have been resolved with high enantiomeric enrichments. Several other tertiary acetate esters carrying a CF3 group have been investigated which proved inert to enzymatic hydrolysis. From these results and published data, we are able to propose a predictive model for identifying the preferred enantiomer of secondary and tertiary trifluoromethyl acetate esters for this lipase.

Synthesis and optical properties of new tricyano-p-quinodimethane dyes: molecular and polymeric systems

Abstract The reaction of N , N -bis(2-hydroxyethyl)aniline 1 with tetracyano- p- quinodimethane (TCNQ) 2 yields the photochromic red chromophore 3 [ λ max (acetone/dichloromethane) 497 nm] which upon UV irradiation is converted into the blue zwitterionic form 3 ′ ( λ max 680 nm) by a novel intramolecular charge transfer process involving a d -quinoid-aryl-A→ d + -aryl-quinoid-A − conversion. The analogous process occurs in the polyimide derived system 8 . Different products are isolated from reactions of 1 with the stronger electron acceptors TCNQBr 2 and TCNQF 4 .

Electronic effects in π-facially stereoselective epoxidation of phenyltrifluoromethylpropenol

AM1, PM3 and ab initio6-31G* calculations indicate that Stereoselective epoxidation of the alkene 3 arises from stereoelectronic control exerted via a CF3–C bond orientated antit the alkene plane for steric reasons in contrast to a previously proposed model for epoxidation of allylic fluorides in which the F–C and alkene bonds are orientedsyn.