We gratefully acknowledge funding from CWRU-ORA, NSF (grant DMR 0080013), DuPont (Young Investigator award to C.W.) and cordially thank Eric Cottington for his support. We are indebted to Teresa Bernal, Yu Hu, Akshay Kokil, Ben Poon, Aditya Ranade, Dr. Louis Somlai, and Dr. Huiwen Tai for technical assistance with the production of multilayer films and physical measurements. Supporting information is available online from WileyInterscience (www.WileyInterscience.com) or from the authors.
Photopatternable Reflective Films Produced by Nanolayer Extrusion†
Article first published online: 21 MAY 2004
Copyright © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Advanced Functional Materials
Volume 14, Issue 6, pages 595–604, June, 2004
How to Cite
Tangirala, R., Baer, E., Hiltner, A. and Weder, C. (2004), Photopatternable Reflective Films Produced by Nanolayer Extrusion. Adv. Funct. Mater., 14: 595–604. doi: 10.1002/adfm.200305446
- Issue published online: 17 JUN 2004
- Article first published online: 21 MAY 2004
- Manuscript Accepted: 13 NOV 2003
- Manuscript Received: 26 JUN 2003
- Optically active materials;
Novel patternable, light-reflecting multilayer polymer films are presented. The investigated elements comprise 1024 nanolayers of two different, transparent polymers in strictly alternating fashion. Polymers with different refractive indices were employed and the individual layer thickness was controlled between 50 and 200 nm; as a result the investigated films exhibit pronounced optical interference effects. Different photoreactive additives were integrated into the multilayer films, rendering the optical characteristics of these elements tunable. One approach relied on the use of photoreactive blends of poly(methyl methacrylate) (PMMA) and up to 25 wt.-% of trans-cinnamic acid (CA) or trans-methyl cinnamate (MC). Upon exposure to ultraviolet (UV) radiation, CA and MC undergo dimerization through 2+2 cycloaddition, leading to a significant decrease of the blend's refractive index. As a result, the reflectivity of the multilayer films based on these photoreactive blends changes considerably upon photoreaction. The second approach was based on the use of blends of PMMA and 2-(2′-benzoylphenyl)benzoxazole (BzPO), a ‘caged’ photoluminescent dye. This benzoyl ester of 2-(2′-hydroxyphenyl)benzoxazole (HPBO) is not photoluminescent, but upon exposure to appropriate UV radiation, the ester bond is cleaved, and the photoluminescent HPBO is quantitatively restored. Thus, using conventional photolithographic techniques, reflective multilayer films were patterned with photoluminescent designs.