Anthraquinone derivatives with N- and O-substitution are incorporated into waterborne polyacrylates as single-component polymers with both thermally activated delayed fluorescence and two-state phosphorescence.
The mechanical, degradation, and related thermal properties of segmented polyster-urethane elastomers which were aged under strain in three different environments (25°C in air, 85°C in air, and 85°C in water) were investigated by stress-strain measurements, DSC, and FTIR. From the stress-strain measurements, it showed that the polyester-urethane samples aged under a high prestrain, particularly at high temperature, resulted in decreases of the initial slope, and stress and elongation at break. The behavior of stress-strain curves also showed that aging the polyester-urethane at a higher prestrain and a higher temperature leaded the urethane elastomer to be more brittle. Morphological changes which were induced in the segmented elastomer by aging under strain were investigated by DSC in terms of the glass transition temperature of the soft segments, the melting temperature of the hard segments, and the heat of fusion of the crystalline hard segments. FTIR measurements indicated the degradation of the ester C-0-C bond during aging at high strain, especially in the water. Based on the DSC and FTIR studies, the behavior of the stress-strain measurements of the aged urethane elastomers was explained.
Fluorescent and room-temperature phosphorescent (RTP) materials are widely used in bioimaging, chemical sensing, optoelectronics and encryption. Here, a series of single-component dual-emissive waterborne polyurethanes (WPUs) with both fluorescence and room-temperature phosphorescence were synthesized. Dye without halogen atom incorporated into WPUs can only exhibit fluorescence due to poor spin-orbit coupling. When bromine atom is introduced into dye, we found that WPUs can emit both fluorescence and room-temperature phosphorescence with lifetimes up to milliseconds because of enhanced spin-orbit coupling. Moreover, with an increase in dye concentrations in WPUs, excimers are formed due to the aggregation effect, and may promote communication between singlet and triplet states. At different dye concentrations, structural, thermal, and luminescent properties serve as the main focus.
Isothermal and non-isothermal crystallization kinetics of long alkane chain segment nylon 1010, 1013 and 1014 were investigated by differential scanning calorimetry. The commonly used Avrami equation and that modified by Jeziorny were employed to fit the isothermal and non-isothermal crystallizations of nylon 1010, 1013 and 1014, respectively. It was found that the crystallization rate of nylon with a longer alkane chain segment was slower than that of nylon with a shorter one at a given cooling rate. The activation energies for the isothermal and non-isothermal crystallizations determined by the Arrhenius and the Kissinger methods, respectively, decreased with increase of the alkane chain segment length of nylon 1010, 1013 and 1014. Furthermore, the activation energy of the non-isothermal crystallization process of these nylons, determined by the isoconversional methods of Flynn and Wall and Ozawa, was found to be a decreasing function of the relative degree of crystallinity.
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