Department of Chemical Engineering, Texas Tech University, Lubbock, TexasWelcome to Greg McKenna's 'Polymers and Condensed Matter Physics Group'

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Development of a dielectric nonresonant spectral hole burning capability

   Shankar Kollengodu-Subramanian

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

References:

  1. B.schiener, R.Bohmer, A.Loidl, R.V.Chamberlin, Science, 274, 752 (1996).

  2. Susan Weinstein, Ranko Richert, Physical Rev. B, 75, 064302 (2007).

  3. Kalyan Duvvuri, Ranko Richert, Journal of Chemical Physics, 118, 1356 (2003)

  4. Lectures on dielectric theory and insulation, Edited by J.B. Whitehead, 1st edition, McGraw-Hill Book Company (1927)

  5. R. Bohmer, B.Schiener, J. Hemberger, R.V.Chamberlin, Z.Phys. B 99, 91 (1995).

  6. L.Banda, Alcoutlabi.M, G.B.McKenna, J.Polym.Sci. Part B: Polym.Phys.,44, 801-814 (2006).

  7. Zheng Y, G.B.McKenna, Macromolecules, 36, 2387-2396 (2003).

Funding: National Science Foundation

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This site has been developed by Shankar Kollengodu-Subramanian      
For problems or questions regarding this Web site contact [shankar.subramanian@ttu.edu].
Last updated: 06/09/09.