Diblock copolymer adsorption from the aqueous micellar phase to solid surfaces: real time monitoring by ATR spectroscopy in the mid-infrared

Attenuated Total Reflectance (ATR) in the mid-infrared is employed to monitor the adsorption of poly(tert-butyl styrene - b - styrene sulfonate), PtBS-PSS, copolymers with a small hydrophobic head as well as of an analogous poly(styrene sulfonate), PSS, homopolymer on germanium and Au-plated germanium surfaces from aqueous NaCl solutions. The surface density of the adsorbed polyelectrolyte is monitored via the growth of characteristic infrared absorptions of the sulfonated ring at 1036- and 1008 cm⁻¹ in the 2nd derivative mode. These probe bands do not exhibit shifts or changes in bandshape over very prolongued adsorption experiments. Pronounced differences in the kinetics of adsorption are observed between the PSS homopolymer and the PtBS-PSS copolymers in agreement to previous investigations by phase-modulated ellipsometry on similar systems. Adsorption of the diblocks above the critical micelle concentration is found to involve a sequence of diffusion, micellar relaxation and brush-limited processes.     

Use of FT-NIR spectroscopy for on-line monitoring of formaldehyde-based resin synthesis

A new method is being developed for the fast and reliable assessment of the pathway(s) followed during formaldehyde-based resin synthesis, both at laboratory and industrial scale. The method is based on Fourier transform Near Infrared (FT-NIR) chemometrics. No sample manipulation is necessary and the complete evaluation can be performed on- or off-line in less than 1 min. FT-NIR chemometrics were found to be valuable in providing a fast and consistent way of monitoring directly the effects of a change of resin formulation when evaluating new procedures at laboratory scale. Similarly, during industrial production, NIR will soon become a standard tool for ensuring reproducibility and improving overall quality. Measurements are performed on-line and deviations from the standard synthesis pathway can be detected early, allowing the necessary steps to be taken in order to return to the desired pathway. Furthermore, NIR methodologies have been developed to identify and check the conformity of raw materials and final products from urea and UFC solutions to laminated paper produced by impregnation with formaldehyde-based resins. This can prove particularly useful in applications (such as in laminated paper production) where the reproducibility of production and the effects of storage are both questionable and difficult to assess.     

A parallel multi-configuration self-consistent field algorithm

A scalable multi-configuration self-consistent field (MCSCF) algorithm is described. The method for optimizing the orbital and configurational parameters is based upon the two-step Newton–Raphson approach with an augmented orbital Hessian matrix. A single copy of the two-electron integrals in the molecular orbital basis is distributed over the memory of all processors. Storage of the augmented Hessian is avoided by re-computing its elements as needed. A replicated data approach is used to parallelize the configuration interaction step. Scalability to 1024 processors is demonstrated.     

Cation mass dependence of the nearly constant dielectric loss in alkali triborate glasses

Electrical ac conductivity measurements on alkali triborate glasses ( M2O x 3B2O3, M = Li, Na, K, and Rb) were performed at temperatures down to 8 K and frequencies up to 1 GHz. All samples show a nearly constant dielectric loss (NCL), at the limit of high frequencies and/or low temperatures. The magnitude of the NCL is found to decrease as m(-1/3) with increasing alkali ion mass m. This quantitative result for the NCL, closely related to the mean-square displacement of ions, indicates that the origin of the NCL might be related to vibrational relaxation of the ions in the anharmonic potentials that cage them, and the cage is decaying very slowly with time.