Complexes of polyacids with poly(vinylbenzocrown ether)s and polyvinylbenzoglymes in water

Insoluble complexes are formed in acidic aqueous media when poly(acrylic acid) (PAA) and poly-(vinylbenzo-18-crown-6) (P18C6) or polyvinylbenzoglymes are mixed. Complex formation results from hydrogen bonding between carboxyl groups and crown ether- or glyme–oxygen atoms as well as from hydrophobic interactions. The precipitation is pH dependent and was determined as a function of the ratio PAA to P18C6 or to polyglyme at different HCl concentrations in 10^?4M solutions of polycrown or polyglyme. Precipitation is nearly quantitative in 0.01N HCl. The compositions of PAA/P18C6 precipitates were determined as a function of the initial PAA/P18C6 ratio in solution. The complexes with P18C6 can be solubilized in acidic media when crown-complexable cations (K⁺, Cs⁺, Ba²⁺) are added, but the charged P18C6 reprecipitates in basic solution as a polysalt complex with the PAA–polyanion. More stable PAA–P18C6 complexes in the form of fibers can be obtained by interfacial complex formation. Poly(methacrylic acid) is less effective as a complex former.     

Screening, Gene Sequencing and Characterising of Lipase for Methanolysis of Crude Palm Oil

Staphylococcus sp. WL1 lipase (LipFWS) was investigated for methanolysis of crude palm oil (CPO) at moderate temperatures. Experiments were conducted in the following order: searching for the suitable bacterium for producing lipase from activated sludge, sequencing lipase gene, identifying lipase activity, then synthesising CPO biodiesel using the enzyme. From bacterial screening, one isolated specimen which consistently showed the highest extracellular lipase activity was identified as Staphylococcus sp. WL1 possessing lipFWS (lipase gene of 2,244 bp). The LipFWS deduced was a protein of 747 amino acid residues containing an α/β hydrolase core domain with predicted triad catalytic residues to be Ser474, His704 and Asp665. Optimal conditions for the LipFWS activity were found to be at 55 °C and pH 7.0 (in phosphate buffer but not in Tris buffer). The lipase had a K _M of 0.75 mM and a V _max of 0.33 mM?min^?1 on p-nitrophenyl palmitate substrate. The lyophilised crude LipFWS performed as good as the commonly used catalyst potassium hydroxide for methanolysis of CPO. ESI-IT-MS spectra indicated that the CPO was converted into biodiesel, suggesting that free LipFWS is a worthy alternative for CPO biodiesel synthesis.     

Infrared spectral study of noncrystalline rodlike polymers

Oriented and unoriented films of noncrystalline, wholly-aromatic, rodlike polyamides, and polyesteramides were examined by infrared spectroscopy. The results indicate that orientation, accomplished by means of mechanical stretching, approaches 80% in both polymer classes. Examination of the NH and the CO stretching region revealed an increase in the population of nonhydrogen bonded species (plateauing at ～ 85%) as orientation increases. This unusual result may be caused by interchain steric interactions which may also be responsible for both the noncrystalline morphology and the non-lyotropic behavior exhibited by these polymers.     

Fluorine—an enabler in advanced photolithography

Fluorine—its chemical and physical properties—plays a critical role in the development of advanced photolithography. It is widely expected that, when in a few years the critical dimensions in microelectronic devices will be less than ∼70 nm, the patterning technology of choice will be based on 157 nm light generated from molecular fluorine laser medium. Lithography at 157 nm also requires major advances in areas of fluorine science, from the growth of near-perfect calcium fluoride crystals for lenses to fluorine doping of fused silica for masks to the synthesis of fluoropolymers that would serve as pellicles, photoresists, and immersion liquids. With the expected resolution of these issues, the prospects are excellent that photolithography will continue as the main semiconductor patterning technology for at least another decade.     

Molecular factors affecting solubility in rigid-rod polyamides

The solubility of a series of para-linked, substituted phenyl, biphenyl, terphenyl, and quaterphenyl polyamides is reported. Most of these polymers are soluble in amide solvents without lithium chloride, and several are soluble in ethers and/or ketones. The results indicate that solubility in this class of polymers is affected by the position, polarizability and size of the substituents, enantiomeric purity, and the number of non-coplanar biphenyl rings per repeat unit.