0000000000420117
AUTHOR
Xiaopeng Xiong
showing 3 related works from this author
Continuous spin fractionation and characterization by size-exclusion chromatography for styrene-butadiene block copolymers.
2005
Abstract Linear and star-shaped styrene–butadiene block copolymers synthesized by anionic polymerization of butadiene and styrene were fractionated by applying a newly developed large-scale fractionation technique, named continuous spin fractionation (CSF). Their molecular weight and polydispersity index ( d = M w / M n ) were measured with size-exclusion chromatography and static light scattering. For the linear triblock copolymer a fractionation via temperature variation turned out to be better suited than the usual isothermal procedure. The star-shaped polymer with the d value of 1.33 was fractionated in two CSF steps to get the targeted sample, which has a considerably more uniform st…
Intrinsic viscosities of polyelectrolytes: specific salt effects and viscometric master curves.
2013
Dilute solutions of the sodium salt of polystyrene sulfonic acid (PSS-Na) were measured viscometrically as a function of composition in aqueous solvents of different salinity, where the extra salt was either NaCl or CaCl2. Such experiments yield {η}, the generalized intrinsic viscosities (hydrodynamic specific volume) of the polyelectrolyte for arbitrary polymer concentrations, c. In the limit of infinite dilution {η} becomes identical to the intrinsic viscosity [η]. For NaCl {η} decreases monotonously with rising c, whereas maxima are passed in the case of CaCl2. Condensing c and the concentration of extra salt in the mixed solvent into a single variable enables the establishment of predic…
A versatile viscometric method for the study of dissolved proteins, exemplified for casein micelles in ammoniacal solutions
2017
Abstract Viscosities of casein solutions were measured within the dilute range in ammoniacal water and in saline solvents containing different amounts and different kinds of salt. All these data are modeled quantitatively by means of an approach accounting for the polyelectrolyte character of casein micelles. Two parameters are required: The intrinsic viscosity [ η ] and a viscometric interaction parameter β . The behavior of casein is compared with that of chain-like polyelectrolytes. For both polymers one observes a pronounced reduction of [ η ] with increasing salt concentration. However, for casein the decline of [ η ] is less pronounced by more than an order of magnitude and depends on…