Polymer chain properties and thermodynamic stability in oriented-platelet nanocomposites.
We present a Monte Carlo study of the conformational properties of polymer chains in platelet nanocomposites. We find that high platelet orientation leads to an increase in chain confinement and to a substantial decrease in polymer entropy. The latter may be responsible for the observed aging of these systems in which the platelets gradually lose their orientation with time. As a test of our entropy-driven hypothesis, we suggest that aging could be substantially slowed down by the addition of small spherical nanoparticles. Using a generalized Stokes-Einstein relation, a calculation of the thermal random motion of the platelets predicts a fivefold increase in shear modulus during aging, in agreement with experimental observation on compatibilized layered silicate nanocomposites.
Central Research and Development, DuPont Nanocomposite Technologies, Building E304, Room C219, Experimental Station, E. I. DuPont de Nemours, Inc., Wilmington, Delaware 19880-0304, USA. yves.termonia@usa.dupont.com
Yves
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Termonia