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7554011 
Journal Article 
High Performance Graded Rainbow Holograms via Two-Stage Sequential Orthogonal Thiol-Click Chemistry 
Peng, H; Mcleod, RR; Bowman, CN; Nair, DP; Kowalski, BA; Xi, W; Gong, Tao; Wang, C; Cole, M; Cramer, NB; Xie, X; , 
2014 
1 
Macromolecules
ISSN: 0024-9297
EISSN: 1520-5835 
AMER CHEMICAL SOC 
WASHINGTON 
2306-2315 
WOS:000338807300014 
Orthogonal, sequential "click" reactions were implemented to yield novel polymeric substrates with the ability to record holographic data. The base-catalyzed thiol-acrylate Michael "click" reaction was implemented to yield a writable, stage 1 polymeric substrate with glass transition temperatures (T-g) ranging from 0 to -26 degrees C and rubbery storage moduli (E') from 11.1 to 0.3 MPa. The loosely cross-linked matrix also contained a novel high refractive index monomer 9-(2,3-bis(allyloxy)propyl)-9H-carbazole (BAPC) that did not participate in the thiol-Michael reaction but allowed for large index gradients to be developed within the network upon subsequent exposure to coherent laser beams and initiation of the radical-mediated thiol-ene reaction. The holographic gratings were recorded with 96% diffraction efficiency and ca. 2.4 cm/mJ of light sensitivity in 2 s under a 405 nm exposure with an intensity of 20 mW/cm(2). Subsequent to pattern formation, via a thiol-allyl radical "click" photopolymerization initiated by flood illumination of the sample, holographic materials with high T-g, high modulus, diffraction efficiency as high as 82%, and refractive index modulation of 0.004 were obtained. Graded rainbow holograms that displayed colors from blue to red at a single viewing angle were readily formed through this new technique.