Dynamics of Glass-forming Materials Gregory B. McKenna, Texas Tech University, DMR Structural Recovery after CO 2 - jumps We have previously shown that the structural recovery of materials subjected to moisture-jumps (relative humidity) leads to different behavior in the glassy state than do simple temperature jumps. We have now demonstrated that this result is also observed when a carbon dioxide pressure-jump is used. The result is shown in Figure 1 where we compare the volume recovery after a temperature jump with that after a CO 2 – pressure jump. We note that, though the excess volume in the CO 2 – jump condition is greater, the glass seems to be more stable (structural recovery times are longer). Importantly, this response is more dramatic than what was observed in the RH-jump conditions and is being further investigated. Dielectric Spectroscopy Time-domain dielectric spectroscopy is being developed to investigate the dynamic response of polymers subsequent to CO 2 – pressure jumps. Figure 2a shows master curves of the time-domain response of a model system of poly(vinyl acetate). Figure 2b shows the time-temperature superposition of the data and agreement with literature values. Dielectric spectroscopy is new to the PI’s laboratories. The time-domain spectrometer is being adapted to perform dielectric hole burning experiments. Figure 1. Comparison of structural recovery after temperature jump and CO 2 – pressure jump to the same final state. Figure 2. a) Time-temperature superimposed time- domain dielectric responses for PVAc film. b) Time- Temperature shift factors from 2a compared with literature values showing agreement between dielectric and mechanical from literature and from present measurements. a) b)

Dynamics of Glass-forming Materials Gregory B. McKenna, Texas Tech University, DMR Education and Outreach-June 2006-July 2007 Project results presented at universities, companies and national and international meetings NIST, Gaithersburg, MD, July 2006 (invited talk by G.B. McKenna, PI) INSA, Lyon, France, June 2006 (invited seminar by G.B. McKenna, PI) Symposium honoring K..L. Ngai, Pisa, Italy, September 2006 (invited talk by G.B. McKenna, PI) Euromech Colloquium 487, Strasbourg France, October 2006 (invited talk by G.B. McKenna, PI) Dow Chemical Company, Freeport, TX, December 2006 (invited talk by G.B. McKenna, PI) APS March Meeting, Denver, CO, March 2007 (contributed talk by G.B. McKenna, PI) APS March Meeting, Denver, CO, March 2007 (contributed talk by Q. Qin, Ph.D. student) E.S.P.C.I., Paris, France, May, 2007 (invited lecture by G.B. McKenna, PI) University of Bayreuth, Bayreuth, Germany, June 2007 (invited talk by G.B. McKenna, PI) Project results presented at regional meetings Society of Plastics Engineers Polyolefins Conference, Houston, TX, February 2007 (poster by S. Kollengodu-Subramanian, graduate student) NATEX, Dallas, TX, April 2007 (poster presented by S. Kollengodu-Subramanian, graduate student) PhD students supported or partially supported- Duration of grant. Yong Zheng, Received Ph.D. in December 2003; Xiangfu Shi, received Ph.D. in December 2004; Anny Flory, received Ph.D. in December 2004; Lameck Banda, received Ph.D. in December Qian Qin, current student, expected to defend Ph.D. thesis in spring 2008; Shankar Kollengodu- Subramanian, current student, expected to defend Ph.D. thesis summer Publications-Duration of grant -7 manuscripts published (Polymer, 45, (2004); J. Phys.: Condensed Matter, 17, R461-R524 (2005); Phys. Rev. Lett., 94, (2005); J. Chem. Phys. 122, (2005)); J. Polymer Sci. Part B. Polymer Phys. Ed., 44, (2006); Phys. Rev. B., 73, (2006); J. Non-Crystalline Solids, 352, (2006); 1 manuscript accepted (J. Non-Crystalline Solids); 6 proceedings publications; 1 manuscript in review (J. Polym. Sci. Part B. Polymer Physics Ed..) Broad Accomplishments