Combinatorial and high-throughput approaches in polymer and materials science: Hype or real paradigm shift?

No abstrac

Synthesis of novel associating water-soluble copolymers

Poly(N,N-dimethylacrylamide) (4 samples) and Poly(N-acryl-N- methylpiperazine) (10 samples) were prepared by anionic polymerization in THF at {minus}78{degrees} in the presence of Cs or coordinated Li counter cations. Molecular weights (SEC) range from 3800--250,000. The polymers are soluble in methanol, H{sub 2}O and chloroform and to a lesser extent, in THF and CH{sub 2}Cl{sub 2}. Molecular weight distributions were found to be fairly monodisperse (1.11 < D < 2.69). (See Proposed Research''). Static and dynamic light scattering experiments performed on solutions of hydrophobically associating polyacrylamide copolymers illuminate the underlying molecular basis for the previous observations. Aggregation effects for these polymers are observed at polymer concentrations as low as 10 ppm. These effects are manifest by large radii of multichain aggregates as well as radii attributed to collapsed chains. Fluorine-10 NMR studies were undertaken in order to determine the content of fluorine-containing comonomer in a series of acrylamide copolymers. These results indicated that comonomer conversion is essentially quantitative. Addition of water-soluble (HOCH{sub 2}CH{sub 2}SH) and water-insoluble (C{sub 12}H{sub 25}SH) radical scavengers indicates that the water-soluble scavenger is effective in reducing molecular weight. The water-soluble scavenger essentially has no effect. This appears to indicate that the polymerization occurs exclusively in the aqueous phase

Visualization of dendrimer molecules by transmission electron microscopy (TEM): staining methods and cryo-TEM of vitrified solutions

International audienc

Free-radical bulk polymerization of styrene: ESR and near-infrared spectroscopic study of the entire conversion range

The free radical polymerization of styrene in bulk was monitored by ESR and FT near-infrared spectroscopy at 70°C for a series of concentrations of the initiator, dimethyl 2,2′-azobis(isobutyrate). In order to obtain detailed kinetic information over the intire conversion range, and the gel effect range in particular, conversion and free radical concentration data points were accumulated with exceptionally short time intervals. The polystyrene radical concentration ([St•]) went through a sharp maximum at the gel effect, a feature that has hitherto escaped observation due to the rapid concentration changes in the gel effect range relative to the data point time intervals of previous studies. Temperature measurements throughout the polymerization were employed to calculate that a temperature increase was not the cause of the [St•] maximum, which thus appeares to be a genuine feature of the gel effect of this system under isothermal conditions. The propagation rate constant (kp) as a function of monomer conversion exhibited a marked dependence on initiator concentration at high monomer conversion; the sharp decrease in kp with increasing conversion was shifted to higher conversions with increasing initiator concentration

STUDY OF THE UNIAXIAL DEFORMATION OF RUBBER NETWORK CHAINS BY SMALL ANGLE NEUTRON SCATTERING

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