The Sensitivity of Small Molecule Sorption to Annealing in Glassy Liquid Crystalline Polymers
- PDF / 501,327 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 38 Downloads / 181 Views
behavior of small molecules in the original, disordered, isotropic polymer can, therefore, be compared directly and unequivocally with corresponding behavior in the ordered, frozen liquid crystalline state.
10
.0.
S•0.02 C
0"00 0.0
0.06
0.2 - 0-"-
NOV0.8
0.4
0.6
1.0
1.0-C Volume Fraction do of Amorphous Phase 3 Figure 1. The effect of three dimensional crystallinity on gas solubility in polyethylene
0.2 0.0 0 5o.6
-
o•.-• 0.
"•''°''"
T=35°C
0.
0.
0. I
-
1.0,
-0.40 0. 00.
20%
Amorphous
Figure 2. The effect of crystallinity on gas solubility in poly(4-methyl-l-pentene) 3 0.6 In a nematic phase of a liquid crystalline polymer, rod-like polymer segments are locally aligned, 4 somewhat imperfectly, in a common direction, described by a vector called the director. Nematic microdomains formed by regions where the director value is constant or changes smoothly and continuously with position are separated by defect or disclination regions, where the director and, therefore, molecular orientation change abruptly. The characteristic width of these disclination regions may be on the size scale of microns in HBA/HNA. 5 While the molecular structure in disclination regions is not well-understood, polymer molecular weight appears to !•lay an important role in the structure of disclinations and the related 6 dynamics of disclination fonmation. ', Disclination regions have been reported to contain relatively high 4 concentrations of chain ends. Small angle light scattering patterns and crossed polarized light microscopy suggest, moreover, that thermal annealing can cause nematic microdomains to grow in size by disclination annihilation. 6 ' 7 EXPERIMENTAL Sample Preparation HBA/HNA, which is insoluble in common solvents, was prepared for gravimetric sorption experiments by microtoming uniform microllakes of constant thickness (5 jitm) at ambient conditions from the core of an extruded flex bar kindly supplied by the Hoechst Celanese Corp. Additional polymer morpho1 logical characterization information and sample preparation details are available elsewhere. The nematic
liquid crystalline domains in the microflake samples, taken from the core of this thick extruded bar, are
82
presumed to be unoriented. 1 The glass transition temperature of HBA/HNA, determined by differential scanning calorimetry (DSC), was approximately 90*C.l HIQ-40 films of uniform thickness of approximately 4-5 jim were prepared at Hoechst Celanese Corp. by casting in a clean room from a ten weight percent polymer solution. The solvent was a 75:25 mixture by weight of trifluoroacetic acid (TFA) and methylene 8 chloride. Air drying and solvent extraction steps resulted in solvent-free, isotropic, non-crystalline films. To prepare HIQ-40 samples with varied morphology, amorphous films were heated, as described elsewhere, 8 to seven different temperatures between 100'C and 330'C. The annealing time was approximately one hour. The range of annealing temperatures provided samples annealed below Tg (approximately 130'C for the isotropic, u
Data Loading...
