This thesis deals with the preferential self-assembly of
metallic nanoparticles (NPs) in an ordered block copolymer (BCP) matrix with
the objective to form a self-assembled photonic bandgap material (PBG). The
novel path we chose to sequester the metallic NPs in a specific domain of the
BCP, follows a "one-pot" process consisting of the in-situ
thermolysis of metal carbonyl precursors (MCPs), with the polymer acting both
as the matrix and as the capping agent for the NPs. Previous studies on this
type of reactions, when performed in a polymer melt above the glass transition
temperature (Tg), have shown the formation of NPs that retain the
characteristic monodisperse. Therefore, we first investigated the possibility
of synthesizing the NPs in a pre-ordered BCP film, inherently below its Tg. We
found that the morphology of the NPs formed below Tg is highly sensitive to the
system temperature, and differs significantly from their morphology above Tg.
The glassy state was found to have dramatic effect on PMMA kinetics while no
effect on PS. Since this path has produced broad polydispersity (PD) and
polymorphism of the NPs, it does not suite optical applications. Therefore,
synthesis was conducted in a BCP solution. The rates of reactions performed in
a BCP solution were found to be much faster than those performed in solutions
of either homopolymer (HP). Three MCPs, Cr(CO)6, Fe(CO)5
and Co2(CO)8, were used to show that this phenomenon is
not specific to the type of MCP, but rather, to the type of polymer in
solution. Furthermore, arrangement of the BCP in solution into core-shell
domains created self-assembled "nanoreactors" with PS acting as the
surrounding shell while the core PMMA domain contained a high precursor
concentration, resulting in faster kinetics. The arrangement of the BCP into
these ordered structures in solution does not occur spontaneously, but is
rather facilitated by a synergistic coupling effect with the MCP. Finally Cr2O3
NPs synthesized in a BCP solution were shown to form thin complex periodic
films that exhibit the preferential incorporation of the NPs into one BCP
domain (specifically PMMA). It is also very important to note that although the
addition of NPs to the BCP matrix essentially causes physical crosslinking
between the BCP chains, it does not hinder the ability of the BCP to self-assemble
into its thermodynamically driven dimensional structure.
