Paper Number
PO107
Session
Poster Session
Title
Mechanical hole-burning spectroscopy of polymer glasses
Presentation Date and Time
October 17, 2018 (Wednesday) 6:30
Track / Room
Poster Session / Woodway II/III
Authors
- Mangalara, Satish Chandra Hari (Texas Tech University, Chemical Engineering)
- McKenna, Gregory B. (Texas Tech University, Department of Chemical Engineering)
Author and Affiliation Lines
Satish Chandra Hari Mangalara and Gregory B. McKenna
Department of Chemical Engineering, Texas Tech University, Lubbock, TX 79409
Speaker / Presenter
Mangalara, Satish Chandra Hari
Text of Abstract
Non-linear mechanics of soft materials like polymer melts or polymer solutions are frequently investigated by Large Amplitude Oscillatory Shear spectroscopy (LAOS) tests. Less work has been reported on the characterization of the non-linear viscoelastic properties of glassy polymers within a similar framework. In the present work we are using an extension of LAOS, i.e., mechanical spectral hole burning (MSHB) to investigate the nonlinear dynamics of polymers in the deep glassy state. MSHB has been developed as an analog to non-resonant spectral hole burning (NSHB) developed by Schiener et al. who attributed the presence of holes to dynamic heterogeneity. On other hand McKenna (and co-workers) in their works on polymer solution and melts, attributed the presence of holes to the type of dynamics rather than to a specific spatial heterogeneity. In MSHB, a small probe response is investigated after a large sinusoidal pump deformation. A series of three experiments are performed to investigate the presence of holes. In the first experiment, the sinusoidal pump is applied followed by a small positive probe deformation. In the second, the pump is followed by a negative probe deformation. The difference in these two probe responses divided by 2 gives a “modified response”. This modified response is compared with the simple “linear response” from a third experiment. The differences between these two responses can lead to the formation of holes. Similar experiments are being performed on polycarbonate and poly(methyl methacrylate) in the glassy state to investigate the presence and origin of holes, if any, and how they relate to the differences in the strengths of the ?-relaxation in the two polymers.