Summary: Self‐association behaviors of poly(γ‐benzyl L ‐glutamate)‐graft‐poly(ethylene glycol) (PBLG‐graft‐PEG) and its mixtures with PBLG homopolymer in aqueous media were investigated by fluorescence spectroscopy, transmission electron microscopy (TEM), and nuclear magnetic resonance (NMR) spectroscopy. It was revealed that PBLG‐graft‐PEG could self‐assemble to form polymeric micelles with a core‐shell structure in the shape of spindle. The introduction of PBLG homopolymer not only decreases the critical micelle concentration, but also changes the morphology of the micelles.
The excitation fluorescence spectra of pyrene as a function of concentrations for the mixture of PBLG‐graft‐PEG with PBLG and a TEM image of the formed micelles. 相似文献
The measurement of the 214Po concentration in air with Makrofol-DE detectors is useful to estimate the long-term averaged equilibrium factors indoors. To differentiate α-particles emitted by 214Po from those emitted by 218Po and 222Rn, the detector must register only α-particles with energies between 6.2 and 7.5 MeV. The required energy response is obtained only if a removed layer of about 43 μm is achieved in a chemical etching of the detector. The methodology used to determine the etching conditions is described in this paper. The optimum conditions found are: a) chemical etching for 6 h at a temperature of 40°C, using 7.5 M KOH mixed with 50% ethanol as an etchant, and b) electrochemical etching for 1 h at a frequency of 3 kHz and an electric field strength of 34 kV cm−1. Several dosimeters have exposed during 2 months in dwellings located in the Barcelona area, Spain. A 214Po averaged concentration of (13.6 ± 8.6) Bq m−3 was obtained. 相似文献
The attractive depletion interaction between a spherical particle and a planar wall in a dilute solution of long flexible
nonadsorbing free polymer chains is found to depend crucially on the particle to polymer size ratio . While the polymer-induced force between particle and wall decreases monotonically with increasing distance for large , for small it has a maximum at a distance of the order of the polymer size. For ideal chains we study the crossover from large to small behavior in full quantitative detail. Besides the free energy of interaction and the force, we also discuss the spatial variations
of the densities of chain-ends and chain-monomers near the wall and particle. Two independent procedures, (1) solving directly
the diffusion equation for the density of ends in terms of planar and spherical waves and (2) minimizing the Ginzburg-Landau
functional of the “magnetic analog” of the polymer problem, are used to obtain results numerically for a broad range of ratios of the three lengths particle size, polymer size and distance of particle from the wall. Besides
previously known cases, we find two more interesting limiting regions of the length ratios for which analytical results can be obtained. [2mm]
Received 11 December 1998 相似文献
We investigate the critical behavior of three-dimensional random-field Ising systems with both Gauss and bimodal distribution
of random fields and additional the three-dimensional diluted Ising antiferromagnet in an external field. These models are
expected to be in the same universality class. We use exact ground-state calculations with an integer optimization algorithm
and by a finite-size scaling analysis we calculate the critical exponents , , and . While the random-field model with Gauss distribution of random fields and the diluted antiferromagnet appear to be in same
universality class, the critical exponents of the random-field model with bimodal distribution of random fields seem to be
significantly different.
Received: 9 July 1998 / Received in final form: 15 July 1998 / Accepted: 20 July
1998 相似文献