In this thesis, atomic force microscopy (AFM), transmission electron
microscopy (TEM) and optical microscopy techniques were used to investigate
systematically the self-assembled nanostructure behaviour of two different types of
spin-cast polymer thin films: poly(isoprene-b-ethylene oxide), PI-b-PEO diblock
copolymers and [poly(9,9-dioctylfluorene-co-benzothiadiazole)]:poly[9,9-
dioctyfluorene-co-N-(4-butylphenyl)-diphenylamine], F8BT:TFB conjugated
polymer blends. In the particular case of the polymer blend thin films, the
morphology of their composites with cadmium selenide (CdSe) quantum dot (QD)
nanoparticles was also investigated. For the diblock copolymer thin films, the
behaviour of the nanostructures formed and the wetting behaviour on mica, varying
the volume fraction of the PEO block (fPEO) and the average film thickness was
explored. For the polymer blend films, the effect of the F8BT/TFB blend ratio (per
weight), spin-coating parameters and solution concentration on the phase-separated
nanodomains was investigated. The influence of the quantum dots on the phase
separation when these were embedded in the F8BT:TFB thin films was also
examined.
It was found that in the case of PI-b-PEO copolymer thin films, robust
nanostructures, which remained unchanged after heating/annealing and/or ageing,
were obtained immediately after spin coating on hydrophilic mica substrates from
aqueous solutions. The competition and coupling of the PEO crystallisation and the
phase separation between the PEO and PI blocks determined the ultimate
morphology of the thin films. Due to the great biocompatible properties of the PEO
block (protein resistance), robust PEO-based nanostructures find important
applications in the development of micro/nano patterns for biological and biomedical
applications.
It was also found that sub-micrometre length-scale phase-separated domains
were formed in F8BT:TFB spin cast thin films. The nanophase-separated domains of
F8BT-rich and TFB-rich areas were close to one order of magnitude smaller (in the
lateral direction) than those reported in the literature. When the quantum dot
nanoparticles were added to the blend thin films, it was found that the QDs prefer to
lie in the F8BT areas alone. Furthermore, adding quantum dots to the system, purer
F8BT and TFB nano-phase separated domains were obtained. Conjugated polymer
blend thin films are excellent candidates for alternatives to the inorganic
semiconductor materials for use in applications such as light emitting diodes and
photovoltaic cells, mainly due to the ease of processing, low-cost fabrication and
mechanical flexibility. The rather limited optoelectronic efficiency of the organic
thin films can be significantly improved by adding inorganic semiconducting
nanoparticles