Abstract
Diffusional heterogeneities of molecular and macromolecular probes were studied during the radical bulk polymerization of methyl methacrylate using fluorescence microscopy methods.
Highlights
Diffusion-controlled reactions play an essential role during polymerization processes, and influence polymerization kinetics and the properties of the synthesized polymeric materials.[1]
In order to investigate this behaviour on a nanoscopic scale, we directly visualized the mobility of molecules and macromolecules in polymerizing methyl methacrylate (MMA) solutions using a combination of highly sensitive fluorescence correlation spectroscopy and widefield fluorescence microscopy
Scheme 1 Structures of fluorescent probes used in this study: PDI0 represents a typical molecular probe, whereas the dendrimerised PDI3 is a compact molecular probe of large size
Summary
Diffusion-controlled reactions play an essential role during polymerization processes, and influence polymerization kinetics and the properties of the synthesized polymeric materials.[1] In particular, at medium to high monomer conversions during free radical chain polymerizations with strong viscosity increase, the kinetics is significantly influenced. Many bulk polymerizations exhibit an autoacceleration period, called the gel or Trommsdorff (-Norrish)[2,3] effect at medium monomer conversion. It can be explained by a significant drop in the termination rate constant kt as a result of the decreasing number of encounters of two radical ends in the reaction medium of increasing viscosity.[1] The magnitude of the Trommsdorff effect depends on. In contrast to bulk methods, single molecule tracking allows for a determination of the distributions of diffusion coefficients.[17,18,19,20,21] diffusional heterogeneities
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