Starch Fractions as Examples for Nonrandomly Branched Macromolecules. 4. Angular Dependence in Dynamic Light Scattering

Abstract

The angular dependence of dynamic light scattering from five degraded potato starch samples was studied. The study allowed the determination of internal modes of motion in branched structures that resemble hyperbranched polymers. The properties of the investigated starches are dominated by the large size of the amylopectin. Measurements were made at infinite dilution (c = 0) and at concentrations c > c* where c* is the overlap concentration. The time correlation function (TCF) at low concentration was analyzed by its first cumulant at low values of qR g and in the asymptotic region of qR g > 2. The first cumulant Γ describes the initial decay of the TCF, g 1 (q,t). A double logarithmic plot of Γ/q 2 ≡ D app (q) against qR g gave a curve that lies between those for hard spheres and flexible coils. In contrast to linear chains, it showed an asymptotic slope of 0.80−0.85 instead of the theoretically expected slope of 1.00. The reduced first cumulant Γ*(q) ≡ (Γ/q 3 )(η0/kT) did not approach a constant plateau at large q but decayed continuously below the experimentally observed plateau value for linear chains. The reason for this behavior is seen in the high branching density and a loss of internal flexibility. In a second part, the angular dependence of the first cumulant in the semidilute regime, up to c/c* = 5, was measured. The data from the different concentrations could be condensed to one common master curve when an empirical scaling parameter was used. A plot of the TCF's from the various concentrations as a function of Γ(q,c,)t resulted in q-independent shape functions g 1 (Γt), which gradually changed from Zimm to Rouse behavior when the concentration was increased beyond the overlap concentration c*. This change is interpreted as a result of hydrodynamic screening.

Size Fractionation by Slalom Chromatography and Hydrodynamic Chromatography

“…(3) was used by Dias [20] and Dias et al [38] to separate amylose and amylopectin -by PCHDC -present in different commercial starches (gifts from National Starch & Chemical). The large molecules of amylopectin [42][43][44][45][46][47][48][49][50] eluted first and the resolution was similar to that obtained with size exclusion chromatography.…”

Structural modification and characterisation of a sugary maize soluble starch particle after double enzyme treatment

“…Moreover, for measuring size distribution of a complex branched macromolecule, dynamic and static light scattering provide a useful tool for probing polymer microstructure at large angels, such as translational diffusion coefficients, dimensions properties, molecular parameters, dynamic and expansion behaviours in solution, whereas laser light scattering with back scattering model (e.g. Zetasizer Nano ZS) usually leads to artefacts and quiet misleading data (Chiou, Fellows, Gilbert, & Fitzgerald, 2005;Galinsky & Burchard, 1997;Gilbert, 2011;Yang et al, 2006). To overcome this problem, the size distribution of branched polymers applied MALLS method to provide the R z information in our study.…”

Theory of Multiple‐Detection Size‐Exclusion Chromatography of Complex Branched Polymers

“…They are different from regular branched polymers like regular stars or combs. Complex branched polymers are present in several important families of polymers: (i) dendritic polymers, both biopolymers (e.g., amylopectin [13,14] ) and synthetic polymers [15] and…”