polymer

Prof. Peggy Cebe

The polymer physics group conducts research on thermal and electrical properties of macromolecules in relation to structure.  Macromolecules exhibit a wide variety of organizational structures, including disordered liquid phases, thermotropic liquid crystals, and true three-dimensional crystals. The liquid-to-solid state phase transformations in liquid crystalline polymers and polymer melts is investigated using dielectric relaxation spectroscopy, and wide and small angle X-ray scattering. Our research group travels to the Brookhaven National Laboratory several times a year to conduct scattering experiments using the high intensity X-radiation at the National Synchrotron Light Source.

In-house research facilities in the polymer physics group at Tufts include systems for measuring spatially resolved optical retardance, electric dipole relaxation, heat capacity and thermal properties. Wide angle X-ray diffraction and molecular modeling capabilties also exist in the polymer physics group. One fundamental problem we are studying is the kinetics of phase transformation in polymers, and the competition between ordering (eg., isotropic-to-nematic-to-crystal) and phase separation under the influence of external fields. In another project in the nano-technology area, we are investigating the effects of restricted dimensionality on the phase transformation kinetics in crystallizable thin films. The research in this group is interdisciplinary in nature, combining solid state physics with materials science.

The polymer physics group collaborates with researchers in the Biomedical Engineering Dept. at Tufts, and has shared facilities including the Biomaterials Characterization Laboratory.  We are studying silk and silk-inspired diblock copolymers. Our model system consists of protein sequences found in native spider dragline silk and we use genetic variants of these sequences to provide the copolymer building blocks in order to assess relationships between block sequence and morphological and structural features. Target applications included drug delivery and medical implants based on silks which are biocompatible.

Recent students graduating with the Ph. D. from our group have been employed at Exxon Research Center, Michelin Americas Research Center, Assumption College, and Cisco Systems.

Selected Publications:

1. Lei Yu and Peggy Cebe. “Crystal Polymorphism in Electrospun Composite Nanofibers of Poly(vinylidene fluoride) with Nanoclay.” Polymer, 50(9),2133-2141 (2009).
2. Huipeng Chen and Peggy Cebe.  “Vitrification and Devitrification of Rigid Amorphous Fraction of PET during Quasi-isothermal Cooling and Heating.”  Macromolecules,42(1), 288-292 (2009).
3. Xaio Hu, Qiang Lu, David Kaplan, and Peggy Cebe.  “Microphase Separation Controlled Beta Sheet Crystallization Kinetics in Fibrous Proteins.” Macromolecules,42(6), 2079-2087 (2009).
4. Marek Pyda, Xiao Hu, and Peggy Cebe.  “Heat Capacity of Silk Fibroin Based on Vibrational Motion of Poly(amino acid)s in the Presence and Absence of Water.” Macromolecules, 41(13), 4786-4793 (2008).