Reversible Nucleation, Growth, and Dissolution of
Poly(γ-benzyl l‑glutamate) Hexagonal Columnar
Liquid Crystals by Addition and Removal of a Nonsolvent
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Abstract
We
have investigated the process of nucleation and growth and its
reversal (i.e., dissolution) of ordered poly(γ-benzyl l-glutamate) (PBLG) objects in thin film solutions containing a few
percent of α-helical PBLG dissolved in chloroform. Nucleation,
growth, and dissolution rate were controlled by adding and removing,
respectively, defined amounts of a nonsolvent (methanol), introduced
through the vapor phase by regulating its flow rate and vapor pressure.
Adding methanol to the isotropic polymer solution allowed for the
induction of nucleation and growth, even with polymer solutions of
very low concentrations, which were significantly below the solubility
limit (equilibrium volume fraction). The variation of the number density
of nuclei with the supersaturation ratio was found to fit well the
predictions of the classical nucleation theory, for all equilibrium
concentrations. For a given supersaturation ratio, fewer objects were
nucleated for lower equilibrium concentrations