title: Photoactive/Passive Molecular Glass Blends: An Efficient Strategy to Optimize Azomaterials for Surface Relief Grating Inscription.
abstract: 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 (Tg). 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 Tgfrom 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 Tgis 25-40 °C above ambient temperature for low to high azo content, respectively. Indeed, for a fixed 40 mol % azo content, choosing the optimal Tgenables doubling the SRG inscription rate and increasing DE 6-fold. Moreover, a higher azo content enables higher DE for a similar Tg. Spectroscopy measurements indicate that the photo-orientation of DR1 and its thermal stability are maximal with Tgaround 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 Tgthat depends on the azo content. This study exposes clear material design guidelines to optimize the SRG inscription process and the photoactivity of azomaterials.
authors.affiliation: Département de chimie, Université de Montréal , Montréal, QC H3C 3J7, Canada.
authors.forename: Audrey
authors.initials: A
authors.lastname: Laventure
authors.affiliation: Département de chimie, Université de Montréal , Montréal, QC H3C 3J7, Canada.
authors.forename: Jérémie
authors.initials: J
authors.lastname: Bourotte
authors.affiliation: Département de chimie, Université de Montréal , Montréal, QC H3C 3J7, Canada.
authors.forename: Jaana
authors.initials: J
authors.lastname: Vapaavuori
authors.affiliation: Department of Physics, Royal Military College of Canada , Kingston, ON K7K 7B4, Canada.
authors.forename: Lucas
authors.initials: L
authors.lastname: Karperien
authors.affiliation: Department of Physics, Royal Military College of Canada , Kingston, ON K7K 7B4, Canada.
authors.forename: Ribal Georges
authors.identifier: http://orcid.org/0000-0001-8346-4393
authors.initials: RG
authors.lastname: Sabat
authors.affiliation: Department of Chemistry and Chemical Engineering, Royal Military College of Canada , Kingston, ON K7K 7B4, Canada.
authors.forename: Olivier
authors.initials: O
authors.lastname: Lebel
authors.affiliation: Département de chimie, Université de Montréal , Montréal, QC H3C 3J7, Canada.
authors.forename: Christian
authors.identifier: http://orcid.org/0000-0001-6144-1318
authors.initials: C
authors.lastname: Pellerin
keywords: azobenzene; glass transition temperature; molecular glasses; photoactive materials; photoinduced orientation; surface relief grating