Molecule-Based Approaches to High-Performance Second-Order Polymeric Nonlinear Optical Materials. Properties of Ultra-hi
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X(2)
performance relationships. Condensation of bismaleimides with diallylamino-functionalized donor-acceptor chromophores yields polable matrices with Tg values as high as 325°C and X(2) responses as high as 0.7 x 10-7 esu (27 pm/V; Xo = 1064 nm; 1.17 eV). Likewise, condensation of o,o'-diallylbisphenol A with bismaleimides followed by chromophore functionalization yields an analogous series of polyimides with Tg values as high as 260'C and X(2) response as high as 1.0 x 10- 7 esu (42 pm/V at Xo = 1064 nm). Polymerization of a bis(4-aminophenyl)lophine chromophore with bismaleimides or diisocyanates yields polymers with Tg values as high as 350-C and )C(2) = 0.62 x 10-7 esu (25 pm/V at Xo = 1064 nm). All members of the above series exhibit minor to negligible decay in X(2) response on aging in air at 100'C for 1000 h. The lophine-based material exhibits only -10% X(2) decay on aging for 100 h at 200 'C under N2. INTRODUCTION Key goals in the pursuit of device-applicable second-order poled polymeric NLO materialsl, 2 include: a) optimizing chromophore number density, b) optimizing and understanding isolated and matrix-bound chromophore second-order response, c) optimizing the temporal stability of poling-imposed chromophore/matrix acentricity, d) optimizing chromophore/matrix thermal/oxidative/chemical stability. Substantial progress is being made in all of these areas, with a) best addressed by covalently linking chromophore substituents to the 3 polymer backbone 2 and b) by coupling exploratory synthesis with quantum chemical analysis. Issue c) presents a significant challenge to our current understanding of glassy polymer chain dynamics, and appears best addressed by immobilization strategies which elevate Tg via crosslinkingl, 2 and/or backbone design. Issue d) has only recently been emphasized. 4 Our strategy for goals c) and d) focuses on modular matrix + chromophore + crosslinker systems which offer fundamental probes of structure/processing relationships and employ interchangeable components which can individually evolve with the state-of-the-art. In this regard, the excellent dielectric properties, optical transparency, high glass transition 85 Mat. Res. Soc. Symp. Proc. Vol. 392 0 1995 Materials Research Society
temperatures, and high thermal/oxidative stability of aryl polyimides 5,6 offers potential attractions for the construction of poled, second-order NLO materials. This possibility was first realized in chromophore-doped polyimide "guest-host" materials 7 ,8 and more recently in chromophore-functionalized polyimides. 9 -11 Our goal in this area is to explore and to understand the materials consequences of new synthetic routes to such materials which are efficient (require a minimum of steps), flexible (employ easily modified, modular building blocks), and maximize field-aligned chromophore immobilization (as indexed by chain dynamic parameters such as Tg). We report here preliminary results on three complementary, ultra-highTg chromophore-functionalized polyimide systems: a) diallylamino crosslin
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