Photochemical changes in absorption and fluorescence of DDM-containing epoxies

Toivola, Ryan; Jang, Sei‐Hum; Mannikko, Donald; Stoll, Stefan; Jen, Alex K.‐Y.; Flinn, Brian D.

doi:10.1016/j.polymer.2018.03.015

Cited by 7 publications

(4 citation statements)

References 68 publications

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“…The pristine TGDDM-EDR-Rh-0% showed a green color with the absorption peak at ∼636 nm in the UV–vis spectra when compressed under 0–3 GPa (Figures a and S17). Similar green chromophores have been previously reported in DDM-containing epoxy under photooxidation, iodine oxidation, and uniaxial compression with a similar absorption band. While the conclusive identification of the structure and mechanism was difficult, the green chromophores are often proposed as quinoidal methine forms of the DDM core structure. − When the TGDDM-EDR-Rh-0% plates were soaked in acid buffer for several hours, a green color could also be observed with a strong absorbance peak at 620 nm (Figure a), suggesting that the quinoidal methine form was perhaps involved (Figure b).…”

Section: Results and Discussionsupporting

confidence: 87%

“…The pristine TGDDM-EDR-Rh-0% showed a green color with the absorption peak at ∼636 nm in the UV−vis spectra when compressed under 0−3 GPa (Figures 4a and S17). Similar green chromophores have been previously reported in DDMcontaining epoxy under photooxidation, 45 iodine oxidation, 46 and uniaxial compression 28 with a similar absorption band. While the conclusive identification of the structure and mechanism was difficult, the green chromophores are often proposed as quinoidal methine forms of the DDM core structure.…”

Section: ■ Results and Discussionsupporting

confidence: 86%

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Stress-Dependent Multicolor Mechanochromism in Epoxy Thermosets Based on Rhodamine and Diaminodiphenylmethane Mechanophores

Chen

Shao

et al. 2022

Macromolecules

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Mechanochromic polymers exhibit potential applications in damage reporting and stress sensing. Despite the rapid progress achieved in recent years, mechanochromic structural polymers, such as epoxy thermosets, remain difficult to develop, let alone structural materials that can distinguish different levels of stress by a visual color change. This work presents a new class of multicolor mechanochromic epoxy thermosets that can discriminate between low and high compressive stresses via the incorporation of two distinct mechanophores. Amino-functionalized rhodamine (Rh) moieties serve as efficient curing agents and ratiometric stress sensors for epoxy thermosets. The Rh mechanophore in the epoxy network can be activated either by scratch or uniaxial compression, showing a reversible color change and a red fluorescence turn-on response. A stress-dependent multicolor response under uniaxial compression and hydrostatic pressure is achieved by the combination of Rh mechanophores with a commercial epoxy resin containing a 4,4′-diaminodiphenylmethane (DDM) framework. The Rh zwitterion formed at a low compressive stress turns the sample red, while a high compressive stress turns the sample green via the formation of the quinoidal methine form of DDM. Differential activation under varying degrees of compressive stress is demonstrated by UV–vis spectroscopy. The facile preparation and ability to recognize stress intensity by the naked eye make this strategy suitable for practical applications.

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Section: Results and Discussionsupporting

confidence: 87%

Section: ■ Results and Discussionsupporting

confidence: 86%

Stress-Dependent Multicolor Mechanochromism in Epoxy Thermosets Based on Rhodamine and Diaminodiphenylmethane Mechanophores

Chen

Shao

et al. 2022

Macromolecules

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show abstract

“…The intensity of the emission peak decreased with time. The decrease in the PL intensity with temperature or time can be attributed to two factors: rst, the cluster structures of the vitrimers could not return completely to their initial state after high-temperature treatment above T g , which inhibited the throughspace communications arising from n-r*, n-p*, and p-p* orbital overlap, as well as hydrogen bonding and other weak interactions; second, the sample surfaces could gradually form ultraviolet (UV)-absorbing thermal-oxidation products 43 .…”

Section: Resultsmentioning

confidence: 99%

White Light Emissive Vitrimers for Phosphor-free Light Emitting Diode Encapsulations

Hong

Wang

Mao

et al. 2022

Preprint

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Current encapsulating materials for white light–emitting diodes (WLEDs) have some insurmountable problems of unrecyclable encapsulating materials and the toxicity of phosphors. The much more promising encapsulating materials should have two characteristics: 1) the chip can be directly encapsulated without phosphors via the luminescence of encapsulating materials, and 2) the encapsulating materials can be reprocessed for recycling. To this end, blue-light emissive vitrimers (BEVs) were first prepared from the reaction of epoxy resin with aliphatic amines, which exhibited strong blue-light emission at 365-nm excitation and fast stress relaxation without an external catalyst. To design the white-light emission, a well-designed yellow element of perylenetetracarboxylic dianhydride was grafted into the BEVs to generate white-light emissive vitrimers (WEVs). In the WEVs, a rare combination of blue- and yellow-light emissions was achieved for designing white light. When the WEV was used as an encapsulating adhesive for 365-nm LED chips without phosphors, stable white light with CIE coordination (0.30, 0.32) was successfully achieved, which provided a promising future for WLED encapsulations.

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“…Second, the sample surfaces could gradually form UV-absorbing thermal-oxidation products. [58] The effect of immersion in solvents with different polarities (ethanol, acetone, tetrahydrofuran, ethyl acetate, and ether) on the PL properties of the materials is shown in Figure 3d and Figure S16c, Supporting Information. The PL intensities of the DC-TEPA samples soaked in the solvents decreased the most, owing to an increase in the gap between the luminous clusters in the crosslinked network.…”

Section: Photoluminescence Of Intramolecular-catalyzed Vitrimersmentioning

confidence: 99%

Intramolecular‐Catalyzed Vitrimers with White‐Light Emission for Light‐Emitting Diode Encapsulation

et al. 2023

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Currently available encapsulating materials for white light-emitting diodes (WLEDs) have certain limitations, such as the toxicity of phosphors and the non-recyclable nature of the encapsulating materials. In this study, relatively promising encapsulating materials with two significant advantages are developed. First, the chips can be directly encapsulated without phosphors using luminescent encapsulating materials. Second, the encapsulating materials can be reprocessed for recycling via intramolecular catalysis. To this end, blue-light-emitting vitrimers (BEVs) are prepared by the reaction of epoxy resin with amines and are found to exhibit strong blue emission and fast stress relaxation via internal catalysis. To obtain white-light emission, a well-designed yellow component, perylenetetracarboxylic dianhydride, is grafted into the BEVs to generate white-light-emitting vitrimers (WEVs). A rare synergy of blue-and yellow-light emission affords white-light emission. When the WEV is used as an encapsulating adhesive for 365 nm LED chips without inorganic phosphors, stable white light with CIE coordinates (0.30, 0.32) is successfully achieved, indicating a promising future for WLED encapsulation.

show abstract

Photochemical changes in absorption and fluorescence of DDM-containing epoxies

Cited by 7 publications

References 68 publications

Stress-Dependent Multicolor Mechanochromism in Epoxy Thermosets Based on Rhodamine and Diaminodiphenylmethane Mechanophores

Stress-Dependent Multicolor Mechanochromism in Epoxy Thermosets Based on Rhodamine and Diaminodiphenylmethane Mechanophores

White Light Emissive Vitrimers for Phosphor-free Light Emitting Diode Encapsulations

Intramolecular‐Catalyzed Vitrimers with White‐Light Emission for Light‐Emitting Diode Encapsulation

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