Starch Fractions as Examples for Nonrandomly Branched Macromolecules. 2. Behavior in the Semidilute Region

Abstract

In a former paper, the dimensional properties of degraded starch fractions of different molar masses were reported. The behavior was found to be dominated by the highly branched amylopectin. The same samples are now investigated in semidilute solution by static−dynamic light scattering. The deviating values of the overlap concentrations calculated by four definitions ([η], R g, R h, and A 2) are discussed. The influence of polydispersity, excluded volume, and branching are checked. All starch fractions form one common master curve in the plot of the normalized osmotic modulus versus the reduced concentration (c/c*). The data are described in terms of the third and fourth virial coefficients A 3 and A 4. At concentrations higher than 9%, low-angle excess scattering starts to govern the behavior in static light scattering, and simultaneously slow motion becomes noticeable in the time correlations function (TCF) that grows as the concentration is increased. The TCFs are described by stretched exponentials (KWW functions). Three modes are observed: a fast one increasing with concentration and two other ones decreasing with concentration. The concentration dependencies of the first two motions are compared with the behavior of the cooperative and the reptation modes predicted by de Gennes for linear chains. The third (slow) motion is interpreted as being caused by associates.

Substituent Distribution in Cellulose Acetates: Its Control and the Effect on Structure Formation in Solution

“…Some associations have been reported for cellulose derivatives in semidilute solutions (4,(31)(32)(33). CA with TDS = 2.5 formed an association in acetone that could be detectable in a static light scattering way; i.e., it was a steady cluster and developed to a reversible gel at c = 13.8% (4).…”

“…CA with TDS = 2.5 formed an association in acetone that could be detectable in a static light scattering way; i.e., it was a steady cluster and developed to a reversible gel at c = 13.8% (4). On the other hands, a dynamic structure, not a steady one, was detected for cellulose tri-3-chlorophenylcarbamate (31), cellulose tricarbanilate (32), and starch fraction in NaOH (33). These three structures appeared as a slow-mode motion in semidilute regions, and the motion was explained not by the real motion of clusters but by an apparent motion resulting from the random forming and breaking of network junctions.…”

Structural and some nutritional characteristics of Velvet bean (Mucuna pruriens) and Lima bean (Phaseolus lunatus) starches

“…These properties are directly affected by AM and AP molar mass. Advances in instrumentation have led to techniques capable of characterizing starch component structure 5, 6. Both size‐exclusion high resolution chromatography with a refraction index indicator and anion exchange high resolution chromatography with amperometric pulse detection have been used to study these structures 7, 8.…”

Removal of Heavy Metals from Multicomponent Metal Mixtures by Polymer Enhanced Ultrafiltration: Effects of pH, Ionic Strength and Conformational Changes in Polymer Structure

“…Although an accurate model is still absent in light scattering from polymers (32), a combination of static and dynamic light scattering data give complementary pieces of information, and for this reason they are commonly used for the characterization of the polymer solutions (33,34). Different patterns of light scattered from a solvent=solute system can be measured by dynamic and static light scattering methods.…”