Differential Scanning Calorimetry (DSC)
Glass transition temperature (T g ) is one of the most fundamental properties of the
polymer electrolytes that is directly linked to the electrochemical properties. It is
influenced by the polymer chain arrangement, crystallinity, viscosity, polymer
interactions or polarity, and molecular weight of the polymers as most of the polymers are crystalline in nature. The ionic conduction in case of the polymers is
supposed to occur via the amorphous phase and segmental motion of the polymer
chains which is further linked with the flexibility of chains. This flexibility criterion
is specified by the glass transition temperature (T g ) value. It is defined as a transition
temperature at which any system goes from rigid to rubbery–viscous phase. Below
T g, there is no ion migration or chain is not moving. While above the T g , there is a
drastic change in the intrinsic properties (density, specific heat, mechanical modulus,
mechanical energy absorption, their dielectric and acoustical equivalents) of the
polymer that supports the fast segmental motion or less viscosity (Zhang et al.
2016). The differential scanning calorimetry (DSC) measurement is performed to
measure the T g , and it also provides the melting and crystallinity of the used material.
The lower value of the T g indicates enhanced flexibility for the polymer matrix. This
increase in flexibility improved the ion swimming rate between electrodes with the
coordinating sites of the polymer chains. So, the main strategy for lowering the value
of the T g is to alter the polymer chain arrangement and disruption of the covalent
bonding between the polymer chains. This can be done by the addition of nanofiller,
plasticizer, nanoclay, etc. Generally, the addition of the above said particles
increases the free volume available for the ion migration, and this makes faster ion
migration.
Crystallinity
The ordering of the polymer chain (long range and short range) affects the ion
migration in a polymer electrolyte as long range order is associated with the
crystallinity which in case of the polymer electrolyte must be lower for faster ion
migration. So, the crystallinity of any system provides sufficient information regarding the material and how it will play its role during the ion transport. The crystallinity
of any polymer material is obtained by the X-ray diffraction (XRD) and the
differential scanning calorimetry (DSC). It needs to be mentioned here that the
amorphous content supports the fast ion migration in the case of the polymer
electrolytes. The amorphous content is achieved by disrupting the crystalline
arrangement of the polymer chains. The best approach is the addition of the
nanofiller, which alters the arrangement of the Lewis acid–base interaction with
polymer chains. The intercalation of the polymer chains in the clay gallery also
lowers the crystallinity. This increases the free volume available for the ion migration as now segmental motion of the polymer chains becomes faster and the ion
jumps faster from one coordinating site to another. The amorphous content can be
8 Polymer Nanocomposites: Synthesis and Characterization
279
Glass transition temperature (T g ) is one of the most fundamental properties of the
polymer electrolytes that is directly linked to the electrochemical properties. It is
influenced by the polymer chain arrangement, crystallinity, viscosity, polymer
interactions or polarity, and molecular weight of the polymers as most of the polymers are crystalline in nature. The ionic conduction in case of the polymers is
supposed to occur via the amorphous phase and segmental motion of the polymer
chains which is further linked with the flexibility of chains. This flexibility criterion
is specified by the glass transition temperature (T g ) value. It is defined as a transition
temperature at which any system goes from rigid to rubbery–viscous phase. Below
T g, there is no ion migration or chain is not moving. While above the T g , there is a
drastic change in the intrinsic properties (density, specific heat, mechanical modulus,
mechanical energy absorption, their dielectric and acoustical equivalents) of the
polymer that supports the fast segmental motion or less viscosity (Zhang et al.
2016). The differential scanning calorimetry (DSC) measurement is performed to
measure the T g , and it also provides the melting and crystallinity of the used material.
The lower value of the T g indicates enhanced flexibility for the polymer matrix. This
increase in flexibility improved the ion swimming rate between electrodes with the
coordinating sites of the polymer chains. So, the main strategy for lowering the value
of the T g is to alter the polymer chain arrangement and disruption of the covalent
bonding between the polymer chains. This can be done by the addition of nanofiller,
plasticizer, nanoclay, etc. Generally, the addition of the above said particles
increases the free volume available for the ion migration, and this makes faster ion
migration.
Crystallinity
The ordering of the polymer chain (long range and short range) affects the ion
migration in a polymer electrolyte as long range order is associated with the
crystallinity which in case of the polymer electrolyte must be lower for faster ion
migration. So, the crystallinity of any system provides sufficient information regarding the material and how it will play its role during the ion transport. The crystallinity
of any polymer material is obtained by the X-ray diffraction (XRD) and the
differential scanning calorimetry (DSC). It needs to be mentioned here that the
amorphous content supports the fast ion migration in the case of the polymer
electrolytes. The amorphous content is achieved by disrupting the crystalline
arrangement of the polymer chains. The best approach is the addition of the
nanofiller, which alters the arrangement of the Lewis acid–base interaction with
polymer chains. The intercalation of the polymer chains in the clay gallery also
lowers the crystallinity. This increases the free volume available for the ion migration as now segmental motion of the polymer chains becomes faster and the ion
jumps faster from one coordinating site to another. The amorphous content can be
8 Polymer Nanocomposites: Synthesis and Characterization
279