Fabrication of Diazocine-Based Photochromic Organic Thin Films via Initiated Chemical Vapor Deposition

Abstract

In this work, we demonstrate the first synthesis of photochromic polymer thin films via initiated chemical vapor deposition (iCVD) using bifunctional, crystalline styrenediazocine as a photochromic unit. Since it represents a solid compound, an innovative custom-made sublimation unit is introduced, which allows the sublimation of the chromophore as well as its transport inside the reactor chamber, maintaining the functionality of the photoswitch. Styrenediazocine was co-polymerized with 1,3,5trivinyl-1,3,5-trimethylcyclotrisiloxane (V 3 D 3 ), a heterocycle with triple vinyl functionality, in a radical polymerization reaction from the gas phase. The structural as well as functional properties of the resulting films were characterized by various methods, including X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FT-IR) spectroscopy, and UV−vis spectroscopy. It could be confirmed that, via iCVD, photoswitchable polymer thin films have been obtained. The polymer is based on a copolymer structure where all photoswitchable molecules are covalently bonded in the main polymer chain. Our approach could pave the way for a completely new class of high-quality, photochromic thin films that are basically applicable on almost every kind of substrate for novel, interdisciplinary application fields, where particularly classical wet chemistry methods cannot be applied.

Controlled Release Utilizing Initiated Chemical Vapor Deposited (iCVD) of Polymeric Nanolayers

“…Additional characteristics and compositions of iCVD polymers that have been demonstrated for other applications (Gleason, 2020b ), and in particular for the permselective layers of membranes (Zhao and Gleason, 2020 ), may find future utility for controlled release applications. For example, photoresponsive iCVD polymers have been produced through the incorporation of chromophores, such as azobenzene (Unger et al, 2017 ) and styrene diazocine (Burk et al, 2020 ). Additional examples are other types of surface functionalization, such as by zwitterionic moieties (Yang et al, 2011 ; Yang and Gleason, 2012 ), and the production of compositional gradients as a function film depth (Montero et al, 2009 ; Schroder et al, 2020 ).…”

Toward real-world applications: promoting fast and efficient photoswitching in the solid state

“…The crystalline styrenediazocine (photoresponsive monomers) together with 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane (another monomer) were sublimed into the reactor chamber, undergoing a radical polymerization in the gas phase and finally deposited on various substrates. 137 The isomerization between trans and cis occurred within 20 min under UV and visible light irradiations, reversibly switching the films between yellow and red. 137…”

“…137 The isomerization between trans and cis occurred within 20 min under UV and visible light irradiations, reversibly switching the films between yellow and red. 137…”

ARGET ATRP of Methyl Acrylate and Methyl Methacrylate with Diazocine-Derived Initiators

“…To date, there have been two reports on the use of diazocine as a comonomer: Li et al applied the 3,8-diaminosubstituted diazocine in a polyaddition reaction to synthesize a polyurea polymer that could be photopatterned and also reported the photomechanical bending of a film . Burk et al fabricated photochromic thin films via initiated chemical vapor deposition from the radical polymerization of divinylated diazocine in the gas phase . However, the incorporation of a single functional unit is often sufficient to accomplish an effective photocontrol of macromolecular systems.…”

“…10 Burk et al fabricated photochromic thin films via initiated chemical vapor deposition from the radical polymerization of divinylated diazocine in the gas phase. 11 However, the incorporation of a single functional unit is often sufficient to accomplish an effective photocontrol of macromolecular systems. Diazocines have been utilized in biomolecules such as peptides, 12 oligonucleotides, 13 and carbohydrates 14 to induce a conformational change for functional control.…”