“…As a kind of stimulus-sensitive materials, photodegradable polymers have gained considerable attention lately, because light can be spatiotemporally localized and controlled in a simple, green, and noncontact way. − Various photolabile chromophores have been introduced either into the polymer side-chain as pendants groups or along the polymer backbone that can exhibit phototriggered chain scission. − So far, there are three main classes of main-chain photodegradable polymers, that is, polyacrylates, polytriazines, and polyacetals, which have found important applications in broad fields from photolithography, biopatterning, to tissue engineering and drug delivery. ,, Besides, novel photodegradable polymers bearing o-nitrobenzyloxy unit have recently been developed as positive photoresists to generate reactive micropatterns. − Upon irradiation, main-chain photodegradable polymers can break down into low molecular weight molecules. This photofragmentation process usually creates a dramatic difference in the solubility between the exposed and unexposed regions.…”
Section: Introductionmentioning
confidence: 99%
“…6−9 So far, there are three main classes of main-chain photodegradable polymers, that is, polyacrylates, polytriazines, and polyacetals, which have found important applications in broad fields from photolithography, biopatterning, to tissue engineering and drug delivery. 1,10,11 Besides, novel photodegradable polymers bearing o-nitrobenzyloxy unit have recently been developed as positive photoresists to generate reactive micropatterns. 12−14 Upon irradiation, main-chain photodegradable polymers can break down into low molecular weight molecules.…”
Photodegradable polymers constitute an emerging class of materials that are expected to possess advances in the areas of micro/nano- and biotechnology. Herein, we report a green and effective strategy to fabricate light-responsive surface micropatterns by taking advantage of photodegradation chemistry. Thanks to the molecular chain breakage during the photolysis process, the stress field of photodegradable polymer-based wrinkling systems undergoes continuous disturbance, leading to the release/reorganization of the internal stress. Revealed by systematic experiments, the light-induced stress release mechanism enables the dynamic adaption of not only thermal-induced labyrinth wrinkles, but uniaxially oriented wrinkle microstructures induced by mechanical straining. This method paves the way for their diverse applications, for example, in optical information display and storage, and the smart fabrication of multifunctional surfaces as demonstrated here.
“…As a kind of stimulus-sensitive materials, photodegradable polymers have gained considerable attention lately, because light can be spatiotemporally localized and controlled in a simple, green, and noncontact way. − Various photolabile chromophores have been introduced either into the polymer side-chain as pendants groups or along the polymer backbone that can exhibit phototriggered chain scission. − So far, there are three main classes of main-chain photodegradable polymers, that is, polyacrylates, polytriazines, and polyacetals, which have found important applications in broad fields from photolithography, biopatterning, to tissue engineering and drug delivery. ,, Besides, novel photodegradable polymers bearing o-nitrobenzyloxy unit have recently been developed as positive photoresists to generate reactive micropatterns. − Upon irradiation, main-chain photodegradable polymers can break down into low molecular weight molecules. This photofragmentation process usually creates a dramatic difference in the solubility between the exposed and unexposed regions.…”
Section: Introductionmentioning
confidence: 99%
“…6−9 So far, there are three main classes of main-chain photodegradable polymers, that is, polyacrylates, polytriazines, and polyacetals, which have found important applications in broad fields from photolithography, biopatterning, to tissue engineering and drug delivery. 1,10,11 Besides, novel photodegradable polymers bearing o-nitrobenzyloxy unit have recently been developed as positive photoresists to generate reactive micropatterns. 12−14 Upon irradiation, main-chain photodegradable polymers can break down into low molecular weight molecules.…”
Photodegradable polymers constitute an emerging class of materials that are expected to possess advances in the areas of micro/nano- and biotechnology. Herein, we report a green and effective strategy to fabricate light-responsive surface micropatterns by taking advantage of photodegradation chemistry. Thanks to the molecular chain breakage during the photolysis process, the stress field of photodegradable polymer-based wrinkling systems undergoes continuous disturbance, leading to the release/reorganization of the internal stress. Revealed by systematic experiments, the light-induced stress release mechanism enables the dynamic adaption of not only thermal-induced labyrinth wrinkles, but uniaxially oriented wrinkle microstructures induced by mechanical straining. This method paves the way for their diverse applications, for example, in optical information display and storage, and the smart fabrication of multifunctional surfaces as demonstrated here.
“…Poly(vinyl ketones), photodegraded by UV irradiation, have been used not only as components for packing materials and agricultural films, but also as functional materials in applications such as imaging, microfabrication, and sensors [45][46][47][48]. Poly(methyl vinyl ketone) (PMVK) can be degraded to its low-molecular-weight fragments by photochemical reactions through either radical or non-radical reactions, which are known as Norrish Type I and II routes [45,48].…”
Biodegradable triblock copolymers based on poly(ε-caprolactone) (PCL) and poly(lactic acid) (PLA) were synthesized via ring-opening polymerization of L-lactide followed by reversible addition–fragmentation chain-transfer (RAFT) polymerization of poly(methyl vinyl ketone) (PMVK) as a photodegradable block, and characterized by FT-IR and 1H NMR spectroscopy for structural analyses, and by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) for their thermal properties. Porous, biodegradable PCL-b-PLA microspheres were fabricated via the oil/water (O/W) emulsion evaporation method, followed by photodegradation of PMVK blocks by UV irradiation. The macro-chain transfer agent (CTA) synthesized by reacting a carboxylic-acid-terminated CTA—S-1-dodecyl-S′-(a,a′-dimethyl-a′′-acetic acid)trithiocarbonate (DDMAT)—with a hydroxyl-terminated PCL-b-PLA block copolymer was used to synthesize well-defined triblock copolymers with methyl vinyl ketone via RAFT polymerization with controlled molecular weights and narrow polydispersity. Gel permeation chromatography traces indicated that the molecular weight of the triblock copolymer decreased with UV irradiation time because of the photodegradation of the PMVK blocks. The morphology of the microspheres before and after UV irradiation was investigated using SEM and videos of three-dimensional confocal laser microscopy, showing a change in their surface texture from smooth to rough, with high porosity owing to the photodegradation of the PMVK blocks to become porous templates.
“…Photochemically reactive polymers − are of considerable interest, because they are useful as photodegradable plastics, photoresists, and biomedical materials and as precursors to ceramic materials. − With regard to photodegradable plastics, it might seem strange to intentionally design a polymer material that falls apart when exposed to light, especially in view of the enormous efforts made by polymer chemists over the years to make their materials stable to light. , However, there are compelling economic and environmental reasons for using degradable plastics in certain applications, and therefore considerable research is now devoted to devising new photodegradable polymers with improved performance. In previous papers, we described the synthesis of a new class of photodegradable polymers that have metal−metal bonds along the polymer backbone. − These polymers are photochemically active, because metal−metal bonds can be cleaved with visible light: …”
A photochemically degradable polyurethane with Mo-Mo bonds along its backbone (I) was synthesized by reacting the isocyanate-capped poly(ethylene glycol) prepolymer Hypol 2000 with the Mo-Mo-bond-containing diol (η 5 -C 5 H 4 CH 2 CH 2 OH) 2 Mo 2 (CO) 6 . A copolymer (II) that contained poly(ethylene glycol) in addition to Hypol 2000 and (η 5 -C 5 H 4 CH 2 CH 2 OH) 2 Mo 2 -(CO) 6 was also synthesized. The backbones of both polymers can be photochemically cleaved, because the Mo-Mo bonds homolyze when irradiated with visible light. A net photochemical reaction only occurs in the presence of a radical trap, such as oxygen in the air; no net photochemical reaction occurs in the absence of radical trap. X-ray photoelectron spectroscopy shows that the Mo oxidizes during the photochemical reaction in air, initially to Mo(V) and then to Mo(VI). Both products are likely oxide species. Infrared spectroscopy confirms the release of CO when the polymers are irradiated. A polyurethane copolymer (III) that photochemically degrades in the absence of oxygen was synthesized by reacting (η 5 -C 5 H 4 -CH 2 CH 2 OH) 2 Mo 2 (CO) 6 and 1,4-butanediol with tolylene 2,4-diisocyanate terminated poly-(propylene glycol) and 1-(chloromethyl)-2,4-diisocyanatobenzene. The Cl atoms are readily abstracted by the photochemically generated Mo radicals, and this polymer readily degrades when irradiated in the absence of air. Despite the relatively low concentration of Cl in this polymer, the quantum yield for photodegradation is remarkably high (0.35). Other polymers with much higher concentrations of Cl trap are less reactive, and it is concluded that T g is an important parameter in determining the efficiency of photochemical degradation. It is proposed that because chain motion occurs above T g , the radical trapping reaction is more facile, resulting in more net reaction.
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