Evaluation of the thermal stability of some nonlinear optical chromophores

Abstract

Optical data storage is poised to benefit from a new class of advanced polymeric materials engineered I~o exhibit photorefraetivity. Likewise, the transmission and processing of data will also benefit from a related class of materials with electro-optic activity. Organic chromophores are critical constituents of these materials which function due to a change of index of refraction in response to an electric field. However, a number of materials and processing problems remain to be solved before devices incorporating these optically nonlinear ehromophores are practical. For example, for eleetrooptieal applications the NLO waveguide should be able to withstand short duration processing temperatures in excess of 300~ and long duration use temperatures of at least 80~ The requirement for thermoehemical stability follows from the need to implement high T~ matrices to provide stability of the orientational or polar order required for long-term device performance and reliability. As a result, the thermal stability of ehromophores is now more closely evaluated in addition to their transparency and optical nonlinearity properties. Some ehromophore classes, such as the azo dyes studied here, have attractive properties for these applications but further enhancements in overall properties are needed. Identification of the fundamental chemical processes in thermal decomposition of these dyes should lead to introduction of structural changes which provide better stability. Here thermogravimetric analysis (TGA) coupled with mass spectrometry (TGA/MS) is used to provide an assay of thermoehemieal stability with an added benefit that insight into the mechanisms of thermal decomposition may by identified. In this initial study diaryl substitution of the amine in derivatives of 4-amino-4'-nitroazobenzene was observed to greatly enhance thermal stability relative to dialkyl substitution. Substitution of phenyl for alkyl eliminates structural features involved in the most facile degradation mechanism available to the alkyl derivative.

Synthesis and Nonlinear-Optical Properties of Vinyl-Addition Poly(norbornene)s

“…There are two reasons for this change: first, the ethyl-substituted materials are slightly more nonlinear and, second, the ethyl-substituted compounds are more thermally stable. 23 We attempted to synthesize 4-[(2-hydroxyethyl)(ethyl)amino]benzaldehyde by a reaction of 2-(ethylamino)ethanol with 4-fluorobenzaldehyde analogous to the synthesis of 3, but the desired product was obtained in poor yield due to the steric effect (ethyl vs methyl) in the aromatic nucleophilic substitution reaction. Therefore, the monomers M7 and M8 containing the N-ethyl group found in 16 were synthesized instead by a route involving first transesterification between 13 and 2 to give 15 followed by post-formylation reaction to give 16 and finally the Knoevenagel reaction with 4 and 9 producing M7 and M8 respectively (Figure 3c).…”

“…As a secondary structure modification, some chromophores with a diethylamine donor group instead of a dimethylamine donor were also prepared. There are two reasons for this change: first, the ethyl-substituted materials are slightly more nonlinear and, second, the ethyl-substituted compounds are more thermally stable …”

Ionomeric poly(urethane semicarbazides) with azobenzene groups in the main chain – studies on photoswitching behaviour and mechanical properties

“…Earlier work on the isolation and identification of the reaction products demonstrated clearly that the cleavage of C-N bonds in the C-N@N-C group occurred in two steps. Gas chromatographic analysis of the decomposition products indicated that evolution of carbon dioxide and molecular nitrogen was accompanied by the formation of numerous other compounds [19].…”

Preparation of polymer optical fibers doped with nonlinear optical active organic chromophores

“…First, it increases the solubility of the chromophore in organic solvents or solid media. Second, it improves the chemical and thermal stability of these dye molecules 13, 14. The synthetic strategies for the construction of NSP‐1 and NSP‐2 are depicted in Figure 1, and details of the synthesis are provided in the experimental section.…”