In‐situ photopolymerization of oriented liquid‐crystalline acrylates, 4. Influence of a lateral methyl substituent on monomer and oriented polymer network properties of a mesogenic diacrylate

Broer, Dirk J.; Hikmet, R. A. M.; Challa, G.

doi:10.1002/macp.1989.021901218

Cited by 205 publications

(97 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In contrast, for nematic liquid-crystalline diacrylate 1 it has been reported that the order remains constant or even increases upon polymer formation, depending on the polymerization temperature. [21] The strong reduction (65 %) in the dichroic ratio can, in principle, be caused by photoisomerization of the azo dye upon irradiation with UV light. In a control experiment diacrylate 3, doped with 2 wt % dye 4 and 0.1 wt % inhibitor, is subjected to 365 nm UV irradiation in absence of the photoinitiator to prevent photopolymerization.…”

mentioning

confidence: 99%

High‐Contrast Thin‐Film Polarizers by Photo‐Crosslinking of Smectic Guest–Host Systems

et al. 2006

View full text Add to dashboard Cite

The most essential passive optical element in liquid-crystal displays (LCDs) is the polarizer. Polarizers are indispensable for the displaying of the information content and important front-of-screen performance parameters, such as brightness and contrast, are strongly influenced by the performance of the polarizer. Currently, the most widely used polarizers for LCD applications are derivatives of the H-sheet polarizer as invented by E. H. Land in 1938.[1] These dichroic polarizers are based on uniaxially stretched poly(vinyl alcohol) that is impregnated with iodine or doped with dichroic dyes. These sheet polarizers show excellent optical performances that can be expressed by the polarization efficiency (PE) in combination with the single-piece transmittance (T sp ; transmission of unpolarized light through a single polarizer) aswhere T p and T c are defined as the transmission of unpolarized light through two polarizers with their transmission axis parallel and perpendicular, respectively, and where A ʈ and A ⊥ are defined as the absorbance parallel and perpendicular to the average orientation of the long axis of the chromophores, respectively. The polarizer performance can also be expressed by a single parameter; the dichroic ratio (N)For high-end sheet polarizers such as those applied in LCD monitors or flat-panel televisions, the performance exceeds a polarization efficiency (PE) of 99.9 % at a single-piece transmission of 43.5 %, corresponding to N exceeding 50. Unfortunately, two triacetylcellulose (TAC) layers are needed in conventional polarizers to protect the stretched poly(vinyl alcohol) film on both sides against moisture and to obstruct relaxation effects under influence of heat and/or humidity by which the PE value would deteriorate. Further, an adhesive layer is needed in order to laminate the polarizer to the display. The necessary use of protective and adhesive layers adds unnecessary thickness to H-sheet polarizers. Finally, these polarizers show limited thermal stability and low resistivity against solvents. Numerous advantages are foreseen when the traditional sheet polarizers are replaced by ultrathin coatable polarizers situated on the inside of the cell (in-cell). Apart from a significant reduction in display thickness and weight, the positioning of the polarizers inside the cell eliminates all parallax-related issues and is beneficial to the robustness of the display. Furthermore, substrates that otherwise would be rejected because of their birefringence, e.g., thin, low-weight, and strong plastic foils or cheap, low-quality glass substrates, can be used when the polarizers are situated inside the LCD cell. The optimal position of the coatable polarizers inside the LCD cells can vary between display designs, however, it is beneficial to place the polarizers beneath the electrodes in order to prevent the need for increased driving voltages of the LCD panels.One possible approach to obtaining thin, coatable polarizers is based on the use of lyotropic liquid-crystalline dyes that form a crys...

show abstract

mentioning

confidence: 99%

High‐Contrast Thin‐Film Polarizers by Photo‐Crosslinking of Smectic Guest–Host Systems

et al. 2006

View full text Add to dashboard Cite

show abstract

“…This is expected since the N2 has fewer flexible carbons and is a stiffer molecule. Broer et al [7] measured Tg of the N1 using the loss tangent from dynamic mechanical analysis. They found that the transition region was very broad with a peak at approximately 90~ It is not completely clear where Tg should be assigned in the birefringence data of Figs 3 and 4, however the peak of the curve for N1 (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…The N1 has 6-carbon aliphatic spacers on each side of the core while the N2 has 3-carbon spacers. N 1 has been studied extensively by Broer et al [7].…”

Section: E X P E R I M E N Tmentioning

confidence: 99%

Birefringence thermal analysis of liquid crystalline monomers and their photopolymers

Schultz

Pogue

Chartoff

et al. 1997

Journal of Thermal Analysis

View full text Add to dashboard Cite

Birefringence analysis was used to measure thermal transitions in liquid crystal diacrylate monomers and their corresponding polymers. In this technique, linearly polarized light was used to probe the sample as the temperature increased via a linear ramp. Various phase transitions were observed in the liquid crystalline monomers. In addition, the monomers were isothermally photopolymerized in the liquid crystalline state and the resulting polymer networks retained their liquid crystalline order. Glass-to-rubber transitions as well as indications of further thermal polymerization and stress relaxation were detected. Results from birefringence experiments were compared to those of more traditional thermal analysis techniques including DSC and TMA.

show abstract

“…8 However the value of E is much lower than that measured for similar materials in bulk systems. 12 We attribute this to a number of factors: ͑1͒ polymerization was carried out on the pore surface of the Anopore membrane, resulting in the system that is very different from bulk, ͑2͒ lecithin used for alignment certainly acts as a plasticizer which reduces cross linking, and ͑3͒ swelling of the polymer by the solvent decreases the glass transition temperature which enables switching. In the absence of solvent switching does not occur which supports the swelling hypothesis.…”

Section: ͑4͒mentioning

confidence: 99%

Yarn ball polymer microstructures: A structural transition phenomenon induced by an electric field

Kossyrev

Crawford

2000

Applied Physics Letters

View full text Add to dashboard Cite

We report on an unusual polymer “yarn ball” microstructure that is created through a template-based synthetic process involving reactive mesogens. We present experimental results of a unique structural transition of the yarn ball when subjected to an electric field, and describe this transition with a modified elastic theory. We model the interactions of the mesogenic thread segments that comprise the yarn ball in terms of mean-field theory by introducing an intersegment potential.

show abstract

In‐situ photopolymerization of oriented liquid‐crystalline acrylates, 4. Influence of a lateral methyl substituent on monomer and oriented polymer network properties of a mesogenic diacrylate

Cited by 205 publications

References 27 publications

High‐Contrast Thin‐Film Polarizers by Photo‐Crosslinking of Smectic Guest–Host Systems

High‐Contrast Thin‐Film Polarizers by Photo‐Crosslinking of Smectic Guest–Host Systems

Birefringence thermal analysis of liquid crystalline monomers and their photopolymers

Yarn ball polymer microstructures: A structural transition phenomenon induced by an electric field

Contact Info

Product

Resources

About