Gelation Studies on a Radical Chain Cross-Linking Copolymerization Process: Comparison of the Critical Exponents Obtained by Dynamic Light Scattering and Rheology

✍ Scribed by Sven Richter; Volodymyr Boyko; Klaus Schröter

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 134 KB
• Volume: 25
• Category: Article
• ISSN: 1022-1336
• DOI: 10.1002/marc.200300209

✦ Synopsis

Abstract

Summary: The sol–gel transition of a radical chain cross‐linking copolymerization system [N‐vinylcaprolactam/2‐hydroxylethyl methacrylate/allyl methacrylate] has been studied using in situ time‐resolved dynamic light scattering (DLS) and in situ rheology. A critical dynamic behavior was observed near the sol–gel transition, which was characterized by the presence of a power‐law spectra over three decades in the time–intensity correlation function g~2~(t) − 1 ∼ t^−μ^ and over two decades in the oscillatory shear experiment G′(ω) ∼ G″(ω) ∼ ω^n^. A comparison of the obtained critical exponents μ ≈ 0.62 and n ≈ 0.75 was made. The theory predicts a relationship between these exponents, but up to now no experimental comparison has been done. The experimental results favor the percolation model, with a fractal dimension d~f~ of the gel clusters of 1.67.

Double‐logarithmic plot of time–intensity correlation functions g~2~(t) − 1 versus the delay time t.

imageDouble‐logarithmic plot of time–intensity correlation functions g~2~(t) − 1 versus the delay time t.