Interaction between physical aging, deformation, and segmental mobility in poly(methyl methacrylate) glasses.

Area of Science:

• Polymer Science
• Materials Science
• Physical Chemistry

Background:

• Physical aging significantly influences polymer glass properties.
• Understanding molecular mobility under stress is crucial for predicting material behavior.
• Poly(methyl methacrylate) (PMMA) is a widely studied polymer glass model.

Purpose of the Study:

• To investigate the interplay between physical aging, segmental mobility, and mechanical properties in polymer glasses.
• To determine how stress influences the aging process in polymer glasses.
• To differentiate the effects of stress in the preflow and flow regimes.

Main Methods:

• Utilized optical photobleaching experiments to measure molecular mobility.
• Performed mechanical creep experiments on cross-linked PMMA glasses.
• Systematically varied the aging histories of the polymer samples.

Main Results:

• Observed distinct effects of stress on aging in the preflow and flow regimes.
• In the preflow regime, stress increased mobility but did not eliminate prior aging effects.
• In the flow regime, plastic deformation led to a high mobility state, independent of previous aging.

Conclusions:

• The influence of physical aging on polymer glass mobility is stress-dependent.
• Deformation-induced high mobility states can override previous aging histories in polymer glasses.
• Distinguishing between preflow and flow regimes is essential for understanding polymer glass aging dynamics.