Albert W. H. Mau

Controlled Synthesis and Modification of Carbon Nanotubes and C60: Carbon Nanostructures for Advanced Polymeric Composite Materials

Composites of C60 fullerene and carbon nanotubes with polymers are attractive for a wide range of applications. The combination of the unique physicochemical and optoelectronic properties of the carbon structures with the characteristics of some well-known polymers has proven to yield some interesting effects. Various synthetic approaches to making these advanced polymeric composites have been suggested along with novel methods for microstructuring the materials into aligned or patterned forms.

Structure and growth of aligned carbon nanotube films by pyrolysis

Transmission electron microscopic study on the aligned carbon nanotubes has demonstrated a growth mechanism which involves two sizes of iron nanoparticles. While the small particle is catalytically active for the nucleation of the nanotube, the large particle produces the carbon atomistic species required for the growth of the nanotubes. The aligned nanotubes are believed to be the result of a competition growth process along the normal direction of the substrate. The surface diffusion of carbon atoms on the large iron particle leads to the formation of the observed bamboo-like structure. q 2000 Elsevier Science B.V. All rights reserved.

Conjugated polymers for light-emitting applications

Processable conjugated polymers such as those shown in the Figure are highly desirable for applications in, for example, light emitting devices, especially electrochemical light-emitting cells. Here recent progress in Australia on the synthesis and device applications of such polymers is reviewed and the possibility of tuning the emitted color via an intercalation-induced conformational change of the polymer backbone is examined.

Effect of polyethyleneglycol (PEG) on gas permeabilities and permselectivities in its cellulose acetate (CA) blend membranes

Abstract The effect of polyethyleneglycol (PEG) on gas permeabilities and selectivities was investigated in a series of miscible cellulose acetate (CA) blend membranes. The permeabilities of CO 2 , H 2 , O 2 , CH 4 , N 2 were measured at temperatures from 30 to 80°C and pressures from 20 to 76 cmHg using a manometric permeation apparatus. It was determined that the blend membrane having 10 wt% PEG20000 exhibited higher permeability for CO 2 and higher permselectivity for CO 2 over N 2 and CH 4 than those of the membranes which contained 10% PEG of the molecular weight in the range 200–6000. The CA blend containing 60 wt% PEG20000 showed that its permeability coefficients of CO 2 and ideal separation factors for CO 2 over N 2 reached above 2 × 10 −8 [cm 3 (STP) cm/cm 2 s cmHg] and 22, respectively, at 70°C and 20 cmHg. Based on the data of gas permeability coefficients, time lags and characterization of the membranes, it is proposed that the apparent solubility coefficients of all CA and PEG blend membranes for CO 2 were lower than those of the CA membrane. However, almost all the blend membranes containing PEG20000 showed higher apparent diffusivity coefficients for CO 2 , resulting in higher permeability coefficients of CO 2 with relation to those of the CA membrane. It is attributed to the high diffusivity selectivities of CA and PEG20000 blend membranes that their ideal separation factors for CO 2 over N 2 were higher than those of the CA membrane in the range 50–80°C, even though the ideal separation factors of almost all PEG blend membranes for CO 2 over CH 4 became lower than those of the CA membrane over nearly the full range from 30° to 80°C.

Surface modification of poly(tetrafluoroethylene) by gas plasma treatment

Abstract Poly(tetrafluoroethylene) (PTFE) samples were surface modified in gas plasma atmospheres of air, oxygen, argon and water vapour in order to increase the surface energy. Its dispersive and polar components were determined by contact angle measurements after various treatment times. Plasma treatment times of only 15s were sufficient in all gases studied for substantial surface modification of PTFE. The chemical composition of the surfaces was studied by X-ray photoelectron spectroscopy (X.p.s.). The main results of all the plasma treatments were the abstraction of fluorine and the production of surface crosslinks, whereas only a low level of oxygen-containing groups was attached into the surface layer.

The use of catalytically active pervaporation membranes in esterification reactions to simultaneously increase product yield, membrane permselectivity and flux

Abstract Nafion tubes that function both as a reaction catalyst and a pervaporation membrane have been used to increase the yield in the esterification of acetic acid with methanol and n -butanol by selectively removing products, mainly water, from the reaction mixture. The experiments were performed at room temperature in a batchwise reactor using acidic protons in Nafion pellets and the Nafion membrane as the reaction catalyst. In some experiments the acidic protons in the membrane were partially or fully exchanged with caesium ions, which increased the intrinsic selectivity of the membrane for water but lowered its permeability. In the methanol reaction, the yield of methyl acetate was increased from the usual equilibrium value of 73% to a maximum of 77%. In the n -butanol reaction, the yield of n -butyl acetate increased from 70% to a maximum of 95%. The effect of the membranes catalytic activity on its permselectivity was investigated. The catalytically active membranes showed significantly higher permselectivities for water at the same or higher flux, compared to when no reaction was taking place within the membrane phase.

Plasma‐polymerized polyaniline films: Synthesis and characterization

The radio-frequency plasma polymerization technique was used to polymerize aniline onto polymer substrates including perfluorinated ethylene propylene copolymer. The plasma-polyaniline films were characterized by ultraviolet/visible absorption spectroscopy, Fourier transform infrared spectroscopy, electron spin resonance, X-ray photoelectron spectroscopy, scanning electron microscopy, and contact angle measurements. Preliminary conductivity measurements were also carried out. It was demonstrated that the chemical and physical characteristics of the plasma-polymerized poly-aniline films changed significantly with discharge conditions, indicating the possibility for tailoring the structure and properties of the polyaniline films by optimizing the discharge conditions. In particular, the contents of quinoid sequences and aliphatic crosslinking moieties were found to increase with increasing power input and/or discharge duration. By contrast, the number of free radicals trapped in the polyaniline films and their mobility were shown to increase with decreasing the power input and/or discharge duration within the plasma conditions covered in this study. Furthermore, a correlation was found between surface hydrophilicity of the resultant plasma-polyaniline films and the atomic ratio of C to N.

RAFT synthesis of linear and star-shaped light harvesting polymers using di- and hexafunctional ruthenium polypyridine reagents

The syntheses of linear and star-shaped light harvesting polymers with well defined structure and narrow molecular weight distribution are described. These polymers have ruthenium polybipyridine moieties as the energy trap cores and styrene functionalized coumarin monomers as the light absorbing antenna chromophores. The polymers have been made by reversible addition–fragmentation chain transfer (RAFT) polymerisation using di- or hexafunctional ruthenium-containing RAFT agents. The resulting ruthenium-containing polymers have narrow molecular weight distribution (polydispersity < 1.1) and exhibit energy transfer efficiencies of up to 60% between the coumarin donor dyes and the ruthenium acceptor chromophores.

Controlled Fabrication of Large‐Scale Aligned Carbon Nanofiber/Nanotube Patterns by Photolithography

Large-scale aligned carbon nanofiber/nano-tube patterns have been fabricated by a feasible and inexpensive direct photolithography technique using ordinary black-and-white film as a photomask. Using a calcination/reduction protocol, transition metal salts in the photoresist are transformed to metallic dots, which act as catalysts for the growth of aligned carbon nanotubes (see Figure) by acetylene pyrolysis.

Surface immobilization of poly(ethylene oxide): Structure and properties

We covalently immobilized poly(ethylene oxide) (PEO) chains onto a fluorinated ethylene propylene copolymer (FEP) surface. On the FEP surface, aldehyde groups were first deposited by plasma polymerization of acetaldehyde or acrolein. Then, amino-PEO chains were immobilized through Schiff base formation, which was followed by reduction stabilization with sodium cyanoborohydride. The PEO-grafted polymer surfaces thus prepared were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy, contact-angle measurements, and protein adsorption. The dramatic increase in the CO intensity of the high-resolution XPS C 1s spectrum, together with an overall increase in oxygen content, indicated the successful attachment of PEO chains onto the acetaldehyde plasma surfaces. The amount of grafted PEO chains depended on the superfacial density of the plasma-generated aldehyde groups. The grafted monoamino-PEO chains formed a brushlike structure on the polymer surface, whereas the bisamino-PEO chains predominately adopted a looplike conformation. The PEO surface had a regular morphology with greater roughness than the aldehyde surface underneath. Surface hydrophilicity increased with the grafting of PEO. Also, the bisamino-PEO-grafted surface had slightly higher surface hydrophilicity than its monoamino-PEO counterpart. These PEO coatings reduced fibrinogen adsorption by 43% compared with the substrate FEP surface.