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Multiscale Structures in Polymers and Nanocomposites Sanjeeva Murthy, Rutgers University, DMR 0513926 The influence of hierarchical structure in (a) (b) (c) polymers and composites on their performance was studied by investigating the failure characteristics in different types of materials: a semicrystalline fiber (ultrahigh modulus polyethylene, Spectra ), a liquid crystalline material (polyaramid,Kevlar), and a (d) (e) nanocomposite (PAN with carbon fibers). In the course of this research, a new and powerful method was developed for analyzing structural data at nanometer length scales obtained using small-angle scattering (SAS) Figure 1: Full pattern description of the SAS patterns in elliptical cylindrical coordinates: (a) Bar pattern; (b) Four-point tilted-in pattern; (c) Four-point with light, x-rays or neutrons. This method, butterf ly pattern; (d) Overlay of the data on the elliptical grid (by Eigen illustrated in Figure 1, shows that almost all Vector Research Inc.) (e) Double ellipse analysis of the butterf ly pattern classes of SAS patterns can be conveniently described in elliptical coordinates (Polymer, 2007, 48:3393-3399). Investigation of the failure at quasi-static and ballistic strain-rates in high modulus fibers shows that the some of the differences in performance of on strain rate can be related to vastly different morphology at micrometer length scales (Figure 2). Figure 2: Comparison of Spectra 900 f ibers damaged at ballistic (lef t) and quasi static (right) strain rates. The micrograph on the lef t displays crazing, while that on the right shows plate f ormation. Multiscale Structures in Polymers and Nanocomposites Sanjeeva Murthy, Rutgers University, DMR-0513926 Educational Activities Outreach ● The software developed in this program to fit A post doctoral student (Dr. Fahmi Bedoui), while the small-angle scattering data in elliptical being actively involved in this project over the past coordinate is being rendered user-friendly by year, is helping several undergraduates and graduate adding graphic-user interfaces for distribution students in their research. One of the student to others in the polymer community, especially working on this project, Wenjie Wang, was selected to the users of the beam-lines at the Argonne through a competitive process to attend a the Photon source. summer school on x-ray and neutron scattering at the ● PI’s lab hosted high school students (raising Argonne National Laboratory. He and another seniors) from NY city during one summer. student (Chuang Deng) spend two weeks getting They worked in the lab preparing nanoclay trained on the use of molecular dynamics simulation filled composites and correlating process, software at Dr. Goddard’s lab (Caltech) hand have structure and properties. since been using this software. An undergraduate, ● PI organized two polymer sessions and Paul Mark, who was involved in this projects is now a workshops (2003 and 2007) at the Denver X- going to be a graduate student in Materials Science. ray conference. Both were successful as A McNair Scholar, a Junior undergraduate, Desmond measured by the number of participants at the Nzi, worked one summer in the PI’s laboratory workshop and the special sessions. preparing solvent-spun fibers. The PI developed and ● PI has integrated his laboratory with a Green taught a graduate polymer course and a seminar Chemistry program, being spearheaded by course on polymers, both the first at the University of University of Massachusetts, by working on Vermont. microphase separated copolymers relevant to green polymers.
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