Photocrosslinked surface relief gratings on azobenzene-containing copolymer films

Thermal, optical and photoinduced properties of a series of homo and co-polyimides with two kinds of covalently bonded azo-dyes and their supramolecular counterparts

“…UV-Vis absorption spectra of the investigated materials show two absorption bands that correspond to each of the chromophore. In the case of polymer matrixes containing merely DR13 chromophore, the absorption spectrum is determined by the low-energy p-p ⁄ transition band, which overlaps the high-energy n-p ⁄ one, thus giving a large and symmetric absorption maximum of the trans-isomer [47][48][49] at about 502 nm. The absorption spectrum for polymers containing solely AzPy-2 chromophore exhibits two absorption bands one at 360 nm, which corresponds to the strong p-p ⁄ transition of the trans-isomer, and second at 440 nm, that corresponds to the weak n-p ⁄ transition of the cis-form.…”

Easily crosslinkable side-chain azobenzene polymers for fast and persistent fixation of surface relief gratings

“…61 Although photo-crosslinking could be completed in 15 min, highintensity UV irradiation may induce some photo-degradation of the azo chromophore and damage the SRG structure. 62,63 Besides, 65 some other approaches for obtaining stable SRGs also have the disadvantages of damaging the SRG structures or obviously decreasing the depth of the grating profile. [64][65][66] Herein, we present a facile and highly efficient new postcrosslinking strategy for the fast and persistent fixation of the 70 formed SRGs on the azo polymer films.…”

“…To our knowledge, this is the first report on the use of side-chain azo polymers with easily crosslinkable azo groups for the fixation of the photoinduced SRGs. Such crosslinkable side-chain azo polymers have obvious advantages over the previously reported ones (which contained both the non- 15 crosslinkable azo groups and crosslinkable non-azo groups [59][60][61][62][63] because they could achieve much higher azo contents (e.g., a 100% azo content could be reached in case of azo homopolymers), which is highly useful for the more rapid and efficient formation of SRGs with large saturation modulation depth (as demonstrated 20 in the following studies).…”

Evidence for the applicability of a novel procedure (swelling–poling–deswelling) to produce a stable alignment of second order NLO-chromophores covalently attached to a cross-linked PMMA or polystyrene polymeric network

“…However, this poling technique suffers from various disadvantages [14,15]. For example, the mobility of the NLO chromophores is not completely inhibited even much below the Tg of the polymer, leading to an easy loss of alignment of NLO chromophores after removal of the poling [16,17]. Moreover, physically dispersed NLO chromophores may undergo phase separation, aggregation, crystallization, or leaching.…”

“…In the crosslinked system the chromophores are caged inside the polymeric network and severely restrict in the movement. There are various techniques to achieve such latticehardening under electric poling, for example by thermal crosslinking reaction [18][19][20] or with epoxy resins [21][22][23]. However this latter technique suffers from several shortcomings from a practical standpoint, [24a] being damaging for chromophores sensitive for example to free radicals.…”