Influence of the polymer structure on the achievement of polar orientation in high glass transition temperature nonlinear optical polyimides by photo-assisted poling

New side-chain azo-polymers for optical applications: synthesis and characterization

“…to match as much as possible specific application requirements, such as hindrance of excessive chromophore-chromophore interactions, enhanced film-forming, thermal, optical and mechanical properties [4,5,8,14,16]. A wide range of backbones, used as scaffolds for azo-moieties, are reported in literature, like methacrylates [21,26], maleimides [28,29], imides [30,31], thiophenes [32,33], urethanes [34,35], and esters [36,37] to name a few. Different azo dyes have been tailored by aromatic ring substitution [4] to be used in function of their photochromism [1], photoluminescence [38], or nonlinear optical response [14].…”

Photoinduced Motions in Azo-Containing Polymers

“…173 If a more rigid bond between the polyimide main chain and the side chain azo chromophore is used (for example, an aromatic ring), then the photoassisted poling cannot even take place; the whole arrangement is too rigid. 174,175 A different procedure from the photoassisted poling is the all-optical poling, where the electric field that aligns the chromophore dipoles is actually generated by the laser light. This has been demonstrated as early as 1993.…”

“…Photoassisted poling has been reported on very high Tg materials, such as polyimides 101 and copolyimides . If a more rigid bond between the polyimide main chain and the side chain azo chromophore is used (for example, an aromatic ring), then the photoassisted poling cannot even take place; the whole arrangement is too rigid. , …”

Model for athermal enhancement of molecular mobility in solid polymers by light

“…Increasing f by 5% and 30% decreases τ by one and four decades, respectively. Orientational order in solid films of high-T g poled polymers takes tens of years to centuries to decay to 1/e from the original order [20][21][22][23] and it decays in minutes way below T g when the ordered molecules undergo cyclic isomerization [24][25][26]. Even though reorientation of the azo dye plays a major role in this depoling phenomenon [24], polymer chain motion occurs during light-induced depoling [25], which must create additional free volume in the polymers studied.…”