Morphology of anisotropic polymer-dispersed liquid crystals and the effect of monomer functionality

✍ Scribed by T. J. Bunning; L. V. Natarajan; V. P. Tondiglia; G. Dougherty; R. L. Sutherland

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 420 KB
• Volume: 35
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/(sici)1099-0488(199712)35:17<2825::aid-polb7>3.0.co;2-p

✦ Synopsis

The morphology of transmission gratings with varying Bragg spacings formed using polymer-dispersed liquid crystals were examined using high-resolution scanning electron microscopy and image analysis techniques. The effect on the morphology of small changes in the overall functionality of the prepolymer syrup was observed. An increase in the amount of monofunctional compound resulted in small, nearly spherical domains ( õ100 nm in diameter) confined in well-defined lamellae for samples with a 0.49 mm Bragg spacing. A decrease in concentration (an effective increase in monomer functionality) at this Bragg spacing resulted in larger domains (100-200 nm) with much greater distribution of sizes and shapes. The local volume fractions of discrete liquid crystalline (LC) domains was considerably larger in the latter case. An increase in the Bragg spacing to 1.35 mm also resulted in well-defined lamellae of LC domains, although much more coalescence into irregularly shaped individual domains was observed. Surprisingly, the local volume fraction of LC increased in the larger Bragg spacing samples. The morphology results are discussed qualitatively in terms of liquidgel demixing where the inherent crosslink density and elasticity of the polymeric host must be considered in phase separation processes on the nanoscale.