Epoxy‐Based Azopolymers with Enhanced Photoresponsive Properties Obtained by Cationic Homopolymerization

Abstract

Azopolymers are highly versatile materials due to their unique photoresponsive properties. In this contribution, a novel azo‐modified epoxy network is synthesized by cationic homopolymerization with boron trifluoride monoethylamine (BF3.MEA) complex as initiator. The effect of the addition of a fixed content of amino‐functionalized azo chromophore, Disperse Orange 3, into the polymer matrix is studied in detail. First of all, the thermal curing cycle is optimized by means of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) measurements. Then, the resulting bulk azo‐modified epoxy networks are characterized by means of thermogravimetric analysis (TGA), FTIR, DSC, UV–vis spectroscopy, and rheological measurements. Finally, the optical response of thin films of these materials is determined. The results evidence that azo‐modified epoxy networks obtained by cationic polymerization with optimized curing cycle display high Tg values, high maximum photoinduced birefringence, fast writing speed, and exceptionally high remnant anisotropy. Therefore, this material is a promising candidate to be used for optical storage applications.

Control of Gelation and Network Properties of Cationically Copolymerized Mono- and Diglycidyl Ethers

“…In particular, the cationic ring-opening polymerization (ROP) exhibits fast kinetics and is not oxygen sensitive. 21−23 In recent years, these attractive features, combined to the continuous development of cationic initiators as curing agents of epoxy monomers, 6 have been used to design advanced materials including photoresponsive, 24,25 3Dprinted, 26 or nanostructured thermosets. 27 Interestingly, this polymerization mode undergoes transfers in the presence of protic additives (e.g., water, alcohols) that can be used to control the kinetics of the curing reaction.…”

“…Chain polymerization of epoxy monomers is also extensively used in the literature. In particular, the cationic ring-opening polymerization (ROP) exhibits fast kinetics and is not oxygen sensitive. − In recent years, these attractive features, combined to the continuous development of cationic initiators as curing agents of epoxy monomers, have been used to design advanced materials including photoresponsive, , 3D-printed, or nanostructured thermosets . Interestingly, this polymerization mode undergoes transfers in the presence of protic additives (e.g., water, alcohols) that can be used to control the kinetics of the curing reaction. − , Indeed, in aprotic conditions, the classical activated chain end (ACE) propagation mode operates and yields weakly branched polymer chains that percolates in the early stages of the curing reactions resulting in short t gel as well as small conversion at the gel point (α gel ) (Figure , left side).…”

Improving performance oftwo‐stagephotopolymers for volume holographic recording by fluorinatedepoxy‐amine cross‐linkedmatrices

“…[5][6][7][8] Many kinds of cross-linked host matrices have been reported, which are a mixture of at least two active substances, such as epoxy-amine, epoxy-thiol, isocyanate-alcohol, orthoester-anhydride, and thiol-allyl. [9][10][11][12][13][14] Compared with other cross-linked systems, epoxy-amine has excellent mechanical properties and low volume shrinkage, which is very important for millimeter-thick media in holographic data storage. However, high cross-linking density of epoxyamine matrices sacrificed the diffusivity of monomers, resulting in blurry grating fringes of allyl/epoxy-amine-based photopolymers, which limited their further applications.…”