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Comparison of Critical Exponents Determined by Rheology and Dynamic Light Scattering on Irreversible and Reversible Gelling Systems
Author(s) -
Richter Sven
Publication year - 2007
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.200751010
Subject(s) - dynamic light scattering , rheology , locust bean gum , critical exponent , materials science , xanthan gum , methacrylate , light scattering , polymer chemistry , dynamic mechanical analysis , thermodynamics , scattering , phase transition , optics , physics , polymer , composite material , copolymer , nanotechnology , nanoparticle
Abstract Summary: The sol‐gel transition of a radical chain cross‐linking copoly‐merization system [ N ‐vinylcaprolactam/2‐hydroxylethyl methacrylate/allyl‐methacrylate] and various thermoreversible gelling systems (mixtures made of xanthan gum and locust bean gum as well as gelatin) have been studied using in‐situ time‐resolved dynamic light scattering (DLS) and in‐situ rheology. A critical dynamical behavior was observed near the sol‐gel transition, which is characterized by the presence of a power‐law spectra in the time‐intensity correlation function g 2 ( t )−1 ∝ t − µ and in the low‐amplitude oscillatory shear experiment G ′( ω ) ∝ G ″( ω ) ∝ ω n . A comparison of the obtained critical dynamical exponents µ and n were made according to the theory by Doi and Onuki. This theory predicts a relation between these exponents, but up to now no detailed experimental comparison was done in the past. It was found that for all investigated systems n > µ .