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hhPP. 220K. 230K. 240K. 250K. 260K. 270K. 280K. PIB. blend. PIB: m=1.3. blend: m=1. hhPP: m=0.35. Polyolefin Blend Miscibility: An Experimental Molecular View Jeffery L. White, North Carolina State Univ., DMR-0137968.

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220K

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  1. hhPP 220K 230K 240K 250K 260K 270K 280K PIB blend PIB:m=1.3 blend:m=1 hhPP:m=0.35 Polyolefin Blend Miscibility: An Experimental Molecular ViewJeffery L. White, North Carolina State Univ., DMR-0137968 Following recently reported experimental progress, we have continued to pursue new experiments which clarify the anomalous mixing behavior exhibited by polyolefins, and the role of configurational entropy. Using relaxation techniques with the new CODEX solid-state NMR experiment (from Schmidt-Rohr), we have recent evidence from the blend of polyisobutylene (PIB)/head-to-head polypropylene (hhPP) demonstrating that the overall conformational exchange in the miscible blend of these two polymers exceeds that of the two polymers in the unmixed state. This result agrees with our previous results from the PIB/polyethylene-co-butene system, even though different experimental methods were used. Again, this result is in strong agreement with the Adams-Gibbs model of larger-sized configurational entropy “droplets” in the miscible polyolefins, and does not agree with enhanced enthalpy models. TOP: Pure CODEX spectra at the indicated temperatures for pure PIB, pure hhPP, and the blend showing slow chain reorientation. Quantitative examination of the total detectable exchange fraction over the entire temperature range (BOTTOM) reveals that the blend has greater total conformational reorientation relative to the average of the two components.

  2. Polyolefin Blend Miscibility: An Experimental Molecular ViewJeffery L. White, North Carolina State Univ., DMR-0137968 Education: Two Ph.D. students, directly funded by this grant, have recently graduated : Dr. Xin Jia (December 2004) is now a research scientist at Georgia-Pacific R&D in Milwaukee, WI, and Dr. Justyna Wolak (August 2005), now a postdoctoral researcher with Professor Jacob Schaefer at Washington University. Indeed, the Research Assistantship provided by this NSF grant during the last three years enabled Dr. Wolak to secure not one, but three very prestigious postdoc offers. Outreach: The PI has established an active recruiting program for both summer interns and graduate students in the University of Puerto Rico system. To date, two NSF-REU students (Rosimar Rovira and Leiddy Alvarado) have come to the PI’s group. In addition, the PI and graduate students have participated in high and middle school demonstrations, career fairs, and expos during the year. Finally, through this grant and additional support from the National Research Council, an active collaboration with the Polish research group of S. Jurga has been established. A recent polymer science graduate from Prof. Jurga’s group at Adam Mickiewicz University in Poznan, Dr. Marcin Wochiewicz, will join the PI’s group at OSU as a postdoc beginning 10/2005. * To date, there have been 7 top ACS-journal publications from this grant as principal contact.

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