Temperature coefficients for the chain dimensions of polystyrene and polymethylmethacrylate
1993; American Institute of Physics; Volume: 99; Issue: 11 Linguagem: Inglês
10.1063/1.465528
ISSN1520-9032
AutoresA. T. Boothroyd, Adrian R. Rennie, G. D. Wígnall,
Tópico(s)Phase Equilibria and Thermodynamics
ResumoWe have made precise measurements of the unperturbed radius of gyration 〈S2〉1/20 of polystyrene and polymethylmethacrylate molecules in the melt over the temperature range 120 °C–240 °C by small-angle neutron scattering. Contrary to most previous reports, based on dilute solution measurements, we find that neither polymer exhibits a significant change in dimensions with temperature, and we deduce temperature coefficients, κ=d ln〈S2〉0/dT, of (0.0±0.1)×10−3 K−1 for polystyrene and (0.1±0.1)×10−3 K−1 for polymethylmethacrylate. These κ values are close to those given by thermoelastic measurements, but are difficult to reconcile with predictions obtained from the rotational isomeric state model.
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