Enhanced Rates of Photoinduced Molecular Orientation in a Series of Molecular Glassy Thin Films

Characterization of Cells Interactions with Patterned Azopolymer-Based Materials using SEM, AFM and Video Microscopy

Introduction:

Artificial Extracellular Matrices (ECMs) are promising tools for the study of cell behaviors.

Methods:

Here, we report a protocol for the use of a reconfigurable biocompatible azopolymer thin film through a photoinduced reconfigurable structuration of its surface to study nerve growth, differentiation and cell guidance.

Results & Discussion:

We show that this protocol combined with a spontaneous self-photoinduced polymer is suitable for time-lapse fluorescence video microscopy and can be easily adapted to electron microscopy techniques (SEM) and near-field imaging techniques (AFM).

Photoactive/Passive Molecular Glass Blends: An Efficient Strategy to Optimize Azomaterials for Surface Relief Grating Inscription

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_g). 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_g 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_g 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_g enables doubling the SRG inscription rate and increasing DE 6-fold. Moreover, a higher azo content enables higher DE for a similar T_g. Spectroscopy measurements indicate that the photo-orientation of DR1 and its thermal stability are maximal with T_g 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_g that depends on the azo content. This study exposes clear material design guidelines to optimize the SRG inscription process and the photoactivity of azomaterials.