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Dynamics of polystyrene probed by muon spin spectroscopy
Iain McKenzie1,2,3, Danaan Cordoni-Jordan4, Joseph Cannon5
1Centre for Molecular and Material Science, TRIUMF, Vancouver, BC V6T 2A3, Canada.
Muon spin spectroscopy reveals that the secondary gamma-relaxation process in polystyrene is linked to phenyl ring motion and the glass transition. This relaxation
Area of Science:
- Materials Science
- Chemical Physics
- Polymer Science
Background:
- Polystyrene is a widely used polymer whose dynamic properties are crucial for its applications.
- Understanding secondary relaxation processes, like the gamma-relaxation, is key to predicting polymer behavior, especially near the glass transition.
- Muon spin spectroscopy offers a sensitive probe for studying molecular dynamics in materials.
Purpose of the Study:
- To investigate the secondary gamma-relaxation process in atactic polystyrene using muon spin spectroscopy.
- To determine the influence of molecular weight on the dynamics of phenyl ring motion.
- To correlate the gamma-relaxation process with the glass transition behavior of polystyrene.
Main Methods:
- Muon spin spectroscopic measurements were performed on low-molecular-weight (LMW) and high-molecular-weight (HMW) polystyrene samples.
- Muoniated cyclohexadienyl radicals were utilized as local probes to monitor bulk dynamics.
- Muon spin relaxation was analyzed to characterize the dynamics of the phenyl side groups.
Main Results:
- Muon spin relaxation was found to be caused by the secondary gamma-relaxation process, involving phenyl ring motion.
- The gamma-relaxation process is sensitive to the glass transition temperature of polystyrene.
- The activation energy for the gamma-relaxation in the rubbery state was determined: 0.60(2) eV for HMW and 0.37(3) eV for LMW polystyrene.
Conclusions:
- The study successfully characterized the gamma-relaxation process in polystyrene using muon spin spectroscopy.
- Molecular weight significantly impacts the activation energy of the gamma-relaxation process.
- The findings provide insights into the relationship between polymer dynamics, molecular weight, and the glass transition.
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