INVESTIGADORES
GALANTE Maria Jose
artículos
Título:
Comparison of optical properties of thermally reversible light scattering films consisting in dispersions of polystyrene/naphthalene domains or polystyrene/liquid crystal (EBBA) domains in epoxy matrices
Autor/es:
I.A. ZUCCHI; T. RESNIK; P. A. OYANGUREN; M. J. GALANTE; R. J. J. WILLIAMS
Revista:
POLYMER BULLETIN
Editorial:
Springer-Verlag
Referencias:
Año: 2007 vol. 58 p. 145 - 151
ISSN:
0170-0839
Resumen:
Thermally reversible light scattering (TRLS) films are materials that can be reversibly
switched from opaque to transparent states by varying temperature. TRLS films
containing different types of dispersed domains in an epoxy matrix: a) naphthalene/
polystyrene (NP/PS), and b) liquid crystal (EBBA/PS), were synthesized by
polymerization-induced phase separation. The intensity of transmitted light was
measured as a function of temperature in successive heating/cooling cycles.
Transparent states were observed during heating cycles at temperatures close to the
melting point of NP (81 ºC) or the nematic-isotropic transition of EBBA (at about
70 ºC). The NP crystallization from their polystyrene solutions in the course of
cooling cycles required large undercooling (about 30 ºC). In the temperature range
comprised between melting and crystallization, optical properties depend on the
cooling rate and the thermal history of the material. The situation was quite different
for TRLS films based on EBBA. In this case, the generation of a nematic phase from
the polystyrene solution required a small undercooling (about 2 - 3 ºC), leading to a
relatively sharp transition between opaque and transparent states, independent of the
thermal history. This constitutes a significant advantage of the use of liquid crystals
compared to organic crystals in the manufacture of TRLS films.