Page 558 - Polymer-based Nanocomposites for Energy and Environmental Applications

Hybrid materials based on polymer nanocomposites for environmental applications 511

solution containing mixed solvents of pyridine, chloroform, dichloromethane, and
chlorobenzene by spincoating [4]. TiO 2 nanoparticles were also mixed with a non-
conjugated polymer poly(N-vinylcarbazole) (PVK) in chloroform or tetrahydrofuran
(THF) as solvent under vigorous stirring [5]. The nanocomposite films were prepared
by a spin-coating process.
ZnO is also a well-known electron-transporting material that possesses higher car-
rier mobility than TiO 2 . ZnO nanoparticles were blended with P3HT, PVK, or
polyfluorenes (PFs) in solvents and cast into thin film via spin-coating process by dif-
ferent research groups [9–11]. Besides, a synthesized block copolymer P3HT-b-poly
(ethylene oxide) (PEO) was blended with ZnO nanoparticles to form hybrid
nanocomposites by spincoating from the solution mixture [12]. The PEO part pos-
sesses better compatibility with ZnO via the interaction between the oxygen atoms
of PEO chains and the polar surface of ZnO. More finely dispersed and self-assembled
ZnO in the polymer matrix was obtained. In order to improve dispersion of ZnO in
polymer matrix, chemically modified ZnO nanomaterials have also been proposed.
Dkhil et al. reported semiconducting molecular surfactant-modified ZnO nanorods
to prepare the P3HT/ZnO composite by spincoating from their blend solution in chlo-
roform, chlorobenzene, or ortho-dichlorobenzene (o-DCB) [13]. Shih et al. reported
that n-butylamine-modified ZnO nanoparticles and a hole-trapping polymer poly(9-
(4-vinylphenyl)carbazole) (PVPK) could be dissolved in a chloroform/methanol
mixed solvent, ensuring both components to be homogeneous and leading to uniform
composite films [14]. In addition, in situ formation of ZnO nanoparticles from their
precursor in polymer matrix was also reported. The precursor diethylzinc and a con-
jugated polymer poly(2-methoxy-5-(3 ,7 -dimethyloctyloxy)-1,4-phenylene vin-
0
0
ylene) (MDMO-PPV) were dissolved in a solvent mixture comprising toluene,
THF, and chlorobenzene, followed by deposition of thin films via spin-coating pro-
cess [15]. The as-spun films were aged for 15 min in nitrogen with relative humidity
of 40% for the formation of ZnO nanoparticles and then annealed at 110°C for 30 min
in the same circumstance to form MDMO-PPV/ZnO nanocomposites.
The usage of SiO 2 nanoparticles into conjugated polymers was investigated to
increase the electric conduction and luminescent stability of hybrid composites. Yang
et al. reported homogeneously dispersed SiO 2 nanoparticles in the poly(1,4-phenylene
vinylene) (PPV) precursor/methanol solution by ultrasonication [6,7]. After spin-
coating the blend solution on substrates, the as-spun films were annealed at high tem-
perature to form fully conjugated PPV/SiO 2 nanocomposite films. Besides, SiO 2
nanoparticles were mixed with a fully conjugated polymer MEH-PPV in p-xylene
and sonicated before spincoating into hybrid films [8]. Apart from the above conju-
gated polymers, nonconjugated polymers have also been blended with SiO 2 or alu-
mina (Al 2 O 3 ) nanoparticles to study confinement effect on glass transition
temperature (Tg) and suppression of physical aging of polymers [16]. The two kinds
of nanoparticles have been incorporated into polymer matrices such as polystyrene
(PS), poly(methyl methacrylate) (PMMA), and poly(2-vinyl pyridine). Inorganic
nanoparticles and organic polymers were mixed in methyl ethyl ketone or acetic acid
as solvent and sonicated for 40 min prior to spin-coating process. Nanocomposite
films were obtained by spincoating from their sonicated solutions.