Liquid-Crystalline Polymer Networks:  Effect of Cross-Linking on the Stability of Macroscopic Molecular Orientation

1999 ◽  
Vol 32 (9) ◽  
pp. 3150-3153 ◽  
Author(s):  
Seiji Kurihara ◽  
Akihisa Sakamoto ◽  
Takamasa Nonaka
Keyword(s):  
Molecular Orientation ◽  
Liquid Crystalline Polymer ◽  
Liquid Crystalline ◽  
Polymer Networks ◽  
Crystalline Polymer ◽  
Cross Linking ◽  
The Stability

Observing the relaxation of molecular orientation in sheared liquid crystalline polymer solutions

1990 ◽  
Vol 48 (4) ◽  
pp. 1092-1093
Author(s):  
Wendy Putnam ◽  
Christopher Viney
Keyword(s):  
Molecular Orientation ◽  
Liquid Crystalline Polymer ◽  
Liquid Crystalline ◽  
Crystalline Polymer ◽  
Polymer Processing ◽  
Molecular Alignment ◽  
Global Alignment ◽  
Shear Direction ◽  
Axial Strength ◽  
Strength And Stiffness

Liquid crystalline polymers (solutions or melts) can be spun into fibers and films that have a higher axial strength and stiffness than conventionally processed polymers. These superior properties are due to the spontaneous molecular extension and alignment that is characteristic of liquid crystalline phases. Much of the effort in processing conventional polymers goes into extending and aligning the chains, while, in liquid crystalline polymer processing, the primary microstructural rearrangement involves converting local molecular alignment into global molecular alignment. Unfortunately, the global alignment introduced by processing relaxes quickly upon cessation of shear, and the molecular orientation develops a periodic misalignment relative to the shear direction. The axial strength and stiffness are reduced by this relaxation.Clearly there is a need to solidify the liquid crystalline state (i.e. remove heat or solvent) before significant relaxation occurs. Several researchers have observed this relaxation, mainly in solutions of hydroxypropyl cellulose (HPC) because they are lyotropic under ambient conditions.

correlations of mechanical properties and microstructural parameters in annealed drawn film of liquid crystalline polymer in situ reinforced PP

e-Polymers ◽  
2011 ◽  
Vol 11 (1) ◽  
Author(s):  
Sayant Saengsuwan
Keyword(s):  
Mechanical Properties ◽  
Annealing Time ◽  
Crystalline Phase ◽  
Molecular Orientation ◽  
Liquid Crystalline Polymer ◽  
Liquid Crystalline ◽  
Crystalline Polymer ◽  
Relative Level ◽  
Microstructural Parameters

AbstractDrawn composite thin film based on thermotropic liquid crystalline polymer (TLCP) and polypropylene (PP) was annealed at 130 °C at different times. The influence of annealing time on microstructural and mechanical properties of the composite film has been studied. The correlation in mechanical properties and their microstructural parameters has also been investigated. X-Ray diffraction results reveal that the smectic mesophase transforms progressively into the monoclinic phase as annealing time is increased. Consequently, the true crystallinity (Xc), crystal thickness (L) as well as relative level of molecular orientation of PP crystalline phase in the annealed TLCP/PP films are increased significantly. Also, the TLCP fibrils have no influence on the microstructure of PP crystalline phase. The apparent crystallinity (Xc,a) of PP phase evaluated by DSC also increase significantly with annealing time. As a result, the increases of these microstructural parameters coupled with the reinforcement of TLCP fibrils could be contributed directly to the remarkable enhancement of mechanical properties of the annealed TLCP/PP film in both machine (MD) and transverse (TD) directions. The correlation of moduli with microstructural parameters (Xc, Xc,a and L) exhibits nonlinear relations. However, the relative level of molecular orientation is a more suitable parameter to correlate with the improvement of mechanical properties of the annealed TLCP/PP film. Finally, this work presents that the mechanical properties of the TLCP in situ reinforced thermoplastics can be significantly enhanced via a simple thermal treatment.

Torsional mechanical responses in azobenzene functionalized liquid crystalline polymer networks

Soft Matter ◽  
2013 ◽  
Vol 9 (39) ◽  
pp. 9303 ◽  
Author(s):  
Jeong Jae Wie ◽  
Kyung Min Lee ◽  
Matthew L. Smith ◽  
Richard A. Vaia ◽  
Timothy J. White
Keyword(s):  
Liquid Crystalline Polymer ◽  
Liquid Crystalline ◽  
Polymer Networks ◽  
Crystalline Polymer ◽  
Mechanical Responses

Twists and Turns in Glassy, Liquid Crystalline Polymer Networks

2015 ◽  
Vol 48 (4) ◽  
pp. 1087-1092 ◽  
Author(s):  
Jeong Jae Wie ◽  
Kyung Min Lee ◽  
Taylor H. Ware ◽  
Timothy J. White
Keyword(s):  
Liquid Crystalline Polymer ◽  
Liquid Crystalline ◽  
Polymer Networks ◽  
Crystalline Polymer
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