Influence of molecular structure imaged with atomic force microscopy on the rheological behavior of carrageenan aqueous systems in the presence or absence of cations

摘要: Abstract Influence of microscopic molecular structure imaged using atomic force microscopy (AFM) on macroscopic rheological behavior carrageenan was investigated in an aqueous system. Two types (iota and kappa) with equivalent average weights, purified by alcohol precipitation subsequently transformed to the sodium type, were subjected investigations at concentrations form assemblies; gel precursors or microgels (local networks aggregates) presence absence cations. AFM observations elucidated difference effect cations (super-) carrageenan. In case iota, addition K + increased stiffness strands (composed helices) aligned them a definite direction some degree branching, whereas that Ca 2+ mediated associations between into network-like structures (both which might be artifact during drying preparing specimens). Each structural change involved, however, no very low level side-by-side aggregation helices, good agreement data, showing hysteresis sol-to-gel gel-to-sol transitions. kappa, contrary, formed localized network through helices (more apparent ), consistent thermal transitions, but this interhelical not necessarily prerequisite for gelation. The structure-function relationship cation selectivity each discussed.