Département de chimie, Université de Montréal , Montréal, QC H3C 3J7, Canada.
Department of Physics, Royal Military College of Canada , Kingston, ON K7K 7B4, Canada.
ACS Appl Mater Interfaces. 2017 Jan 11;9(1):798-808. doi: 10.1021/acsami.6b11849. Epub 2016 Dec 29.
Irradiation of azomaterials causes various photophysical and photomechanical effects that can be exploited for the preparation of functional materials such as surface relief gratings (SRGs). Herein, we develop and apply an efficient strategy to optimize the SRG inscription process by decoupling, for the first time, the important effects of the azo content and glass transition temperature (T). We prepare blends of a photoactive molecular glass functionalized with the azo Disperse Red 1 (gDR1) with a series of analogous photopassive molecular glasses. Blends with 10 and 40 mol % of gDR1 are completely miscible, present very similar optical properties, and cover a wide range of T from below to well above ambient temperature. SRG inscription experiments show that the diffraction efficiency (DE), residual DE, and initial inscription rate reach a maximum when T is 25-40 °C above ambient temperature for low to high azo content, respectively. Indeed, for a fixed 40 mol % azo content, choosing the optimal T enables doubling the SRG inscription rate and increasing DE 6-fold. Moreover, a higher azo content enables higher DE for a similar T. Spectroscopy measurements indicate that the photo-orientation of DR1 and its thermal stability are maximal with T around 70 °C, independent of the azo content. We conclude that the SRG potential of azomaterials depends on their capability to photo-orient but that the matrix rigidity eventually limits the inscription kinetics, leading to an optimal T that depends on the azo content. This study exposes clear material design guidelines to optimize the SRG inscription process and the photoactivity of azomaterials.
受照含偶氮材料会产生各种光物理和光机械效应，可用于制备功能材料，如表面浮雕光栅 (SRG)。在此，我们首次开发并应用了一种有效的策略，通过解耦偶氮含量和玻璃化转变温度 (T) 的重要影响，来优化 SRG 记录过程。我们制备了一系列光活性分子玻璃与光惰性分子玻璃的混合物，其中光活性分子玻璃用偶氮分散红 1 (gDR1) 官能化。含 10 和 40 mol% gDR1 的混合物完全混溶，具有非常相似的光学性质，并覆盖了从低于环境温度到远高于环境温度的很宽 T 范围。SRG 记录实验表明，对于低至高偶氮含量，当 T 比环境温度高 25-40°C 时，衍射效率 (DE)、残余 DE 和初始记录速率分别达到最大值。实际上，对于固定的 40 mol%偶氮含量，选择最佳 T 可以使 SRG 记录速率提高一倍，并使 DE 提高 6 倍。此外，较高的偶氮含量对于类似的 T 可以实现更高的 DE。光谱测量表明，DR1 的光取向及其热稳定性在 T 约 70°C 时达到最大值，与偶氮含量无关。我们得出结论，偶氮材料的 SRG 潜力取决于其光取向能力，但基质刚性最终限制了记录动力学，导致最佳 T 取决于偶氮含量。这项研究揭示了明确的材料设计准则，以优化 SRG 记录过程和偶氮材料的光活性。
