Studying the viscoleastic properties of glassy polymers in the
vicinity of glass transition temperature using time domain dielectric
spectroscopy (Kollengodu-Subramanian, Shankar)
Dielectric spectroscopy is a novel technique which can be used to probe
dynamics in the range of 10-6 to 106 in time or
frequency. It has been used with great success to explain the dynamic
heterogeneity in small molecules and polymers (1, 2, 3). However, there
is only limited work available in the literature to study responses such
as the memory effect in glassy polymers (4, 5) that has been widely
discussed in mechanical measurements. Here, we have set up a custom
built dielectric spectrometer for the purpose of studying these
properties of glassy polymers in the vicinity of the glass transition
temperature. This technique will also be used to explain the anomalous
differences observed in structural recovery and physical aging
experiments after plasticizer and temperature jumps to the same final
condition in polymeric glasses that has been previously observed using
mechanical and volumetric measurements in our lab (6, 7).
Preliminary results for Poly(Vinyl acetate) (PVAc) subjected to
isothermal scans are shown in figure 1. Modified KWW fit (solid lines)
has been used to capture the full range of the data including the Dc
conductivity. Figure 2 is the master curve of the data of figure 1. The
horizontal shift factors are shown in figure 3 are in reasonable
agreement with the literature. The memory effect observed using pulse
probe technique is shown in figure 4.
Figure1: Isothermal scan of PVAc Figure 2: Time temperature
superposition of Figure 1
Figure 3: Horizontal Shift factor of figure 1 Figure 4: Pulsed probe
data of PVAc at different time interval
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Ranko Richert, Journal of Chemical Physics, 118, 1356 (2003)
Lectures on dielectric theory and insulation, Edited by J.B.
Whitehead, 1st edition, McGraw-Hill Book Company (1927)
R. Bohmer, B.Schiener, J. Hemberger, R.V.Chamberlin, Z.Phys. B 99, 91
L.Banda, Alcoutlabi.M, G.B.McKenna, J.Polym.Sci. Part B:
Polym.Phys.,44, 801-814 (2006).
Zheng Y, G.B.McKenna, Macromolecules, 36, 2387-2396 (2003).
Funding: National Science Foundation
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