This paper resumes light scattering investigations of saltfree aqueous solutions of two component mixtures of charged spheres
by extending those measurements to systems in which one component is replaced by essentially stiff rodlike particles. In a
second step of investigations these were replaced by linear flexible particles. Fd-virus particles (length l=883 nm) or macromolecules of NaPSS of four different contour lengths have been used as representatives. Mostly the concentration
of latex spheres was fixed at 0.02 Vol%. The concentration of the other component was varied over a wide range. Concerning
the scattering intensity, the contribution of the latex spheres dominates, in particular in the systems containing NaPSS particles.
This simplifies the interpretation of data considerably. A rearrangement of the spheres is observed, depending on the shape
of the other sort of particles. These conclusions can be drawn from the shift of measured static structure factor with concentration c. A power law is found for the q-value of the maximum. The exponent depends on the properties of the second component. For the lower molecular weight (MW)
samples of NaPSS below a critical concentration, the exponent is smaller than 1/3, decreasing the more the smaller the MW
of the samples is. A tentative explanation in terms of charge number of NaPSS particles is given. The short time dynamics
has been explored too. From the data a “dynamically determined structure factor” can be derived, that can be compared with
the measured static structure factor. Good (fd) and fair (NaPSS) agreement is obtained respectively. Only at small wavenumbers
below the maximum of deviations occur which increase with concentration; they are consistent with hydrodynamic interaction.
Received 30 July 1998 and Received in final form 14 December 1998 相似文献
Smart foams: Ultrastable foams with an optimal foamability are obtained using hydroxy fatty acids tubes. The stabilization results from the adsorption of monomers at the air-water interface and from the presence of tubes in the plateau borders. Upon heating, tubes transform to micelles, leading to foam destabilization and thus to the first foams to exhibit temperature-tuneable stability. 相似文献
This communication reports the design and fabrication of porous scaffolds of poly(ε‐caprolactone) (PCL) and PCL loaded with hydroxyapatite (HA) nanoparticles with bimodal pore size distributions by a two step depressurization solid‐state supercritical CO2 (scCO2) foaming process. Results show that the pore structure features of the scaffolds are strongly affected by the thermal history of the starting polymeric materials and by the depressurization profile. In particular, PCL and PCL‐HA nanocomposite scaffolds with bimodal and uniform pore size distributions are fabricated by quenching molten samples in liquid N2, solubilizing the scCO2 at 37 °C and 20 MPa, and further releasing the blowing agent in two steps: (1) from 20 to 10 MPa at a slow depressurization rate, and (2) from 10 MPa to the ambient pressure at a fast depressurization rate. The biocompatibility of the bimodal scaffolds is finally evaluated by the in vitro culture of human mesenchymal stem cells (MSCs), in order to assess their potential for tissue engineering applications.
