Phase Behavior in Self-Assembly of Inorganic/Poly(4-vinylpyridine)-b-poly(ε-caprolactone) Hybrid.

A series of poly(4-vinylpyridine)-b-poly(ε-caprolactone) (P4VP-PCL) diblock copolymers of different composition (namely, various nanostructured phases) were synthesized for hybridization with gold precursors. Interesting phase behavior of gold precursors/P4VP-PCL hybrids was found as evidenced by transmission electron microscopy and small-angle X-ray scattering (SAXS). Consistent with theoretical prediction, phase transformation in the hybrids with PCL-rich P4VP-PCL can be induced by the introduction of the gold precursors. In particular, the phase transformation can be achieved by introducing a very small amount of the gold precursors because of the significant increase in the effective excluded volume of hybridized P4VP microdomain as identified by SAXS experiments through the analysis of the 1D correlation function. This morphological evolution is referred to as the bridging mechanism, suggesting that the PCL block of the P4VP-PCL in the hybrids might play an important role in blocking the interconnection between hybridized P4VP microdomains. In contrast, disordered morphology was observed in the hybrids with P4VP-rich P4VP-PCL because of the strong association between the gold precursors and the P4VP block that might disrupt the ordered phase from microphase separation. [ABSTRACT FROM AUTHOR]