Keywords
Thermotropic liquid crystalline polymers · Nanocomposite · Organoclay ·
Montmorillonite · Intercalation method
Definition
TLCPs having an alkyl substituent with a base on a nematic liquid crystalline phase
were reviewed. We also examined the correlation between the thermal properties and
clay contents of TLCP nanocomposites and the dispersed morphology of the clay
particles. Morphological studies showed that the levels of nanosize dispersion can be
controlled by varying the organoclay content. The addition of only a small amount of
organoclay was found to be sufficient to improve the thermal behavior of the TLCP
hybrids.
Introduction
Thermotropic liquid crystalline polymers (TLCPs) have already been established as
high-performance commercial engineering polymers owing to their specific chemical structures, high strengths, high moduli, low viscosities, and other good mechanical properties. The structure–property relationships of TLCPs have been the subject
of much research. Despite their inferior physical strength when compared with
lyotropic liquid crystalline polyamides, TLCPs are attracting a great deal of interest
based on their melt processability (Baird and Sun 1990; Lusignea 2001).
Despite the increasing interest and numerous papers on composites with
TLCPs, most studies have treated only wholly aromatic rigid-rod-type polymers;
less attention has been paid to the processing and properties of TLCPs containing
substituents, side group structures, or a flexible alkyl group in the main chains.
Although wholly aromatic rigid-rod-type TLCPs exhibit very attractive mechanical properties, they generally have high melting points, which can give rise to
difficulties in processing. The presence of substituents or side groups in main
chain structures in otherwise aromatic polyesters lowers their melting points, thus
widening the processing window. Thus, despite the expected loss of thermomechanical properties that results from their use (compared to the properties of
wholly aromatic TLCPs), they may have considerable advantages in particular
applications (McArdle 1989).
The recent development of nanocomposites was stimulated by work with
nylon 6/clay by Toyota (Kojima et al. 1994; Usuki et al. 1995). Progress,
especially with respect to nanocomposite formation, has been reviewed by
many researchers (Giannelis 1996; Yang et al. 1998). Nanocomposites are one
of the most important classes of synthetic engineering materials. Their makeup is
such that they can be transformed into new materials possessing the advantages
of both organic materials, such as light weight, flexibility, and good moldability,
21 Characterizations of Nanocomposites of Liquid Crystalline Polymers
579
Thermotropic liquid crystalline polymers · Nanocomposite · Organoclay ·
Montmorillonite · Intercalation method
Definition
TLCPs having an alkyl substituent with a base on a nematic liquid crystalline phase
were reviewed. We also examined the correlation between the thermal properties and
clay contents of TLCP nanocomposites and the dispersed morphology of the clay
particles. Morphological studies showed that the levels of nanosize dispersion can be
controlled by varying the organoclay content. The addition of only a small amount of
organoclay was found to be sufficient to improve the thermal behavior of the TLCP
hybrids.
Introduction
Thermotropic liquid crystalline polymers (TLCPs) have already been established as
high-performance commercial engineering polymers owing to their specific chemical structures, high strengths, high moduli, low viscosities, and other good mechanical properties. The structure–property relationships of TLCPs have been the subject
of much research. Despite their inferior physical strength when compared with
lyotropic liquid crystalline polyamides, TLCPs are attracting a great deal of interest
based on their melt processability (Baird and Sun 1990; Lusignea 2001).
Despite the increasing interest and numerous papers on composites with
TLCPs, most studies have treated only wholly aromatic rigid-rod-type polymers;
less attention has been paid to the processing and properties of TLCPs containing
substituents, side group structures, or a flexible alkyl group in the main chains.
Although wholly aromatic rigid-rod-type TLCPs exhibit very attractive mechanical properties, they generally have high melting points, which can give rise to
difficulties in processing. The presence of substituents or side groups in main
chain structures in otherwise aromatic polyesters lowers their melting points, thus
widening the processing window. Thus, despite the expected loss of thermomechanical properties that results from their use (compared to the properties of
wholly aromatic TLCPs), they may have considerable advantages in particular
applications (McArdle 1989).
The recent development of nanocomposites was stimulated by work with
nylon 6/clay by Toyota (Kojima et al. 1994; Usuki et al. 1995). Progress,
especially with respect to nanocomposite formation, has been reviewed by
many researchers (Giannelis 1996; Yang et al. 1998). Nanocomposites are one
of the most important classes of synthetic engineering materials. Their makeup is
such that they can be transformed into new materials possessing the advantages
of both organic materials, such as light weight, flexibility, and good moldability,
21 Characterizations of Nanocomposites of Liquid Crystalline Polymers
579