Page 35 - Polymer-based Nanocomposites for Energy and Environmental Applications

14 Polymer-based Nanocomposites for Energy and Environmental Applications

1.5 Nanoparticle dispersion strategies

Mainly, there are two effective techniques to improve the dispersion of nanoparticles
in PNCs including chemical and mechanical. In this field, the key issue in the design of
PNCs is maximizing the interaction or surface area available between polymer matri-
ces and NPs [99]. Among the several researches on surface modification, using the
surfactant is regarded as a helpful technique in order to improve the interaction of inor-
ganic phase of nanoparticle and organic phase of polymer matrix. Various investiga-
tions [100-104] represented the application of silane as surfactant for surface
modification of inorganic phase and improving their dispersion in polymer matrix.
Also, the silanization of nanodiamond (ND) was successfully carried out by
employing the esterification reaction of hydrolyzed vinyltrimethoxysilane (VTS) in
alcoholic solution [105].
Yang et al. [106] prepared surfactant-modified nickel zinc iron oxide
(NiZnFe 2 O 4 ) nanoparticles with ferrimagnetic behavior at room temperature by a
seed-mediated growth method. The surfactant prevented NiZnFe 2 O 4 aggregation
and provided compatibility with (styrene-b-ethylene/butylene-b-styrene) block
copolymer matrices. In another research [107], the dispersibility of nanodiamond
(ND) in solvents and polymer matrices was improved, by grafting of copolymers
containing vinyl ferrocene (Vf ) onto the surface via a ligand-exchange reaction with
both ferrocene moieties of the copolymer and polycondensed aromatic rings of ND
surface. Zhou et al. [108] studied the dispersion and alignment of carbon nanotubes
(CNTs) in polymer composites under equilibrated and shear flow conditions by
using dissipative particle dynamics (DPD). In this study, dispersion possibility
and average angle were supposed to quantitatively measure the degree of dispersion
and alignment of CNTs.
In the mechanical techniques as another method for nanoparticle dispersion, by agi-
tating, the nanoparticles are forced to be dispersed among the polymer matrices. In this
field, ultrasonic dispersion is also helpful due to providing more uniform dispersion
rather than agitating techniques [109].

1.6 Desirable characteristics for polymer nanocomposites

Apparently, the PNCs are devised to acquire some special properties that pristine
polymers are not strong enough such as mechanical, electric, and optical.

1.6.1 Mechanical properties

Generally, one of the main reasons in adding nanoparticle to polymer matrices is
improving their mechanical factors such as tensile strength, modulus, or stiffness
[110]. However, as mentioned before, the well dispersion of nanoparticles is crucial,
while the poor compatibility among the polymer matrices and the inorganic particles