Dynamics of Glass-forming Materials Gregory B. McKenna, Texas Tech University, DMR 0307084

1. Dynamics of Glass-forming MaterialsGregory B. McKenna, Texas Tech University, DMR 0307084 Structural Recovery after CO2 - 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 CO2 – pressure jump. We note that, though the excess volume in the CO2 – 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 CO2 – 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 CO2 – pressure jump to the same final state. b) a) 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.

2. Dynamics of Glass-forming MaterialsGregory B. McKenna, Texas Tech University, DMR 0307084 Broad Accomplishments • 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 2006. • 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 2008. • Publications-Duration of grant • -7 manuscripts published (Polymer, 45, 5629-5634 (2004);J. Phys.: Condensed Matter, 17, R461-R524 (2005); Phys. Rev. Lett., 94, 157801-1-157801-4 (2005);J. Chem. Phys. 122, 114501-1-114501-6 (2005)); J. Polymer Sci. Part B. Polymer Phys. Ed., 44, 801-814 (2006); Phys. Rev. B., 73, 014203-1-014203-10 (2006); J. Non-Crystalline Solids, 352, 2977-2985 (2006); 1 manuscript accepted (J. Non-Crystalline Solids); 6 proceedings publications; 1 manuscript in review (J. Polym. Sci. Part B. Polymer Physics Ed..)