Page 541 - Polymer-based Nanocomposites for Energy and Environmental Applications

494 Polymer-based Nanocomposites for Energy and Environmental Applications

(2) Method that uses the monomers of the polymeric hosts and the target nanofillers as the
starting materials [98–103]. Nanoparticles are first uniformly dispersed into the monomers
or precursors of the polymeric hosts, and the mixture is then polymerized under desirable
conditions including addition of appropriate catalyst. More attention is given to this method
because it allows one to synthesize nanocomposites with desired physical properties.
A direct and well dispersion of the nanoparticles into the liquid monomers or precursors
will avoid their agglomeration in the polymer matrix and afterward improve the interfacial
interactions between two phases. Tang et al. [98], as an example, synthesized nano-
ZnO/poly(methyl methacrylate) (PMMA) composite by in-site emulsion polymerization.
Nano-ZnO particles were treated with the methacryloxypropyltrimethoxysilane (MPTMS)
to prevent the aggregation in the polymerization and to ensure their effective encapsulation.
(3) PNCs could be synthesized simultaneously by blending the monomers of polymers and pre-
cursors of nanoparticles with an initiator in proper solvent [103a]. For example, Wan et al.
[104] synthesized UV curable, transparent acrylic resin/titanium nanocomposite films by
controlled hydrolysis of titanium tetrabutoxide in Span 85/Tween 80 reverse micelles
and in situ photopolymerization of the acrylic monomers.

18.2.1.3 Template synthesis
Template synthesis [105–108], as the name suggests, uses a nanoporous material as a
template to form nanoscale fillers of hollow (a tubule) or solid (a fibril) shape. The
most important feature of this method is that nanometer tubules and fibrils of various
types of raw materials such as electronically conducting polymers, semiconductors,
metals, and carbons can be fabricated.
Cepak et al. [108] synthesized a semiconductor-conductor tubular nanocomposite
in a 60 mm-thick alumina template membrane having pores of 200 nm diameter. TiO 2
tubules were synthesized within the pores of the alumina membrane using sol-gel pro-
cess before they were subjected to thermal treatment. Polypyrrole wires were then
grown inside the semiconductor tubules adopting the chemical polymerization
method. The conductive polymer enhanced the electric conductivity of the synthe-
sized material, which promised a higher photoefficiency of the TiO 2 -polypyrrole
nanocomposites as a photocatalyst.

18.2.1.4 Phase separation
The phase separation [109,110] consists of dissolution, gelation, and, extraction using
different solvents and freezing or drying process, which leads to the formation of
nanoscale porous foams.

18.2.1.5 Self assembly

Self-assembly [111–114] is a unique and selective process, in which individual
preexisting components organize themselves into required patterns and functions.
The well-known self-assembly method is the molecule-mediated one [112–114]
and commonly used for synthesis of various nanocomposite films with desirable char-
acteristics and thicknesses. Instead of strong chemical bonds, nanoparticles are often
linked by weak hydrogen bonds, van der Waal’s forces, and electric/magnetic dipole
interactions.