Monitoring of the Gelation Process on a Radical Chain Cross-Linking Reaction Based on N-Vinylcaprolactam by Using Dynamic Light Scattering

✍ Scribed by Volodymyr Boyko; Sven Richter

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 127 KB
• Volume: 205
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/macp.200300154

✦ Synopsis

Abstract

Summary: The sol‐gel transition of radical chain cross‐linking copolymerization system [N‐vinylcaprolactam (monomer)/3,3′‐(ethane‐1,1‐diyl)bis(1‐vinyl‐2‐pyrrolidone) (cross‐linker)] has been studied using in situ by time‐resolved dynamic light scattering (DLS). A critical dynamical behavior was observed near the sol‐gel transition, which is characterized by the presence of power‐law spectra over three decades in the time‐intensity correlation function g~2~(t) − 1 ∼ t^−μ^. It was found, that the critical exponent μ is dependent on the amount of the cross‐linker: higher the amount of the cross‐linker, higher is the value of the exponent μ. The occurrence of speckle patterns in the scattered intensity profile and of a power law behavior in the time‐intensity correlation function appeared at the same time. At the lowest concentration of 0.25% cross‐linker, no power law was observed. The estimated values for μ were in the range of 0.39 ≤ μ ≤ 0.577. It can be concluded, that the amount of branching in the critical gel determines the value of μ.

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