Polymer-based materials,from composites to hybrid ones,are part of our daily life,contribute to fundamental societal advancements,and showcase increasingly complex design,so that seizing their microscale properties po...Polymer-based materials,from composites to hybrid ones,are part of our daily life,contribute to fundamental societal advancements,and showcase increasingly complex design,so that seizing their microscale properties poses new and unmet challenges.Monitoring polymer chain mobility is a fundamental task to understand materials properties,but despite promises,luminescence methods are currently applicable only within narrow experimental conditions.We describe an aggregation-induced emission(AIE)-based fluorescent rotor showing unique temperature-independent photophysics that stands out as universal probe for polymer relaxation time and viscosity,correlated to macromolecular chain mobility:Its fluorescence lifetime is independent on the polymer chemical nature and on temperature,while being highly sensitive to the low mobility regime typical of cooperative segmental motions of rubbery polymers,close to the glass transition.The calibration curve obtained with five different polymers allows even nonexperts to assess local mobility in polymers with a single measurement.Fluorescence lifetime imaging microscopy(FLIM)yields quantitative mobility maps of complex and dynamic materials with sub-micrometric resolution.This robust and versatile tool allows access to polymer dynamics even in complex and responsive materials,in a broad temperature range,in real space and time.展开更多
Polymer field-effect transistors operated in the n-channel model with a top-gate/bottom-contact are processed using a solution method. The transistor performance depends on the gate dielectric layer. A high performanc...Polymer field-effect transistors operated in the n-channel model with a top-gate/bottom-contact are processed using a solution method. The transistor performance depends on the gate dielectric layer. A high performance polymer transistor is achieved, with the saturated electron mobility of about 0.46cm2/Vs, threshold voltage nearly 0 V and subthreshold sway of about 0.9 V/decade, employing a polystyrene （PS） dielectric layer. The transistor performances are further improved with increasing current and lower operation voltages by utilizing a bi-layer gate dielectric, comprising a thin PS dielectric layer adjacent to the semiconductor to minimize the density of the interface traps for obtaining a small VT, a large μ and a poly（methyl methacrylate） （PMMA） dielectric layer with a relatively high-k adjacent to the gate electrode for enlarging the capacitance, processed from the orthogonal solvents.展开更多
Dielectric relaxation spectroscopy（DRS） of poly（ε-caprolactone） with different draw ratios showed that the mobility of polymer chains in the amorphous part decreases as the draw ratio increases. The activation en...Dielectric relaxation spectroscopy（DRS） of poly（ε-caprolactone） with different draw ratios showed that the mobility of polymer chains in the amorphous part decreases as the draw ratio increases. The activation energy of the α process, which corresponds to the dynamic glass transition, increases upon drawing. The enlarged gap between the activation energies of the α process and the β process results in a change of continuity at the crossover between the high temperature a process and the α and β processes. At low drawing ratios the a process connects with the β process, while at the highest drawing ratio in our measurements, the a process is continuous with the αprocess. This is consistent with X-ray diffraction results that indicate that upon drawing the polymer chains in the amorphous part align and densify upon drawing. As the draw ratio increases, the α relaxation broadens and decreases its intensity, indicating an increasing heterogeneity. We observed slope changes in the α traces, when the temperature decreases below that at which τα≈ 1 s. This may indicate the glass transition from the ‘rubbery＇ state to the non-equilibrium glassy state.展开更多
基金supported by Italian Ministry of Education(MIUR),PRIN grant number 20179BJNA2.
文摘Polymer-based materials,from composites to hybrid ones,are part of our daily life,contribute to fundamental societal advancements,and showcase increasingly complex design,so that seizing their microscale properties poses new and unmet challenges.Monitoring polymer chain mobility is a fundamental task to understand materials properties,but despite promises,luminescence methods are currently applicable only within narrow experimental conditions.We describe an aggregation-induced emission(AIE)-based fluorescent rotor showing unique temperature-independent photophysics that stands out as universal probe for polymer relaxation time and viscosity,correlated to macromolecular chain mobility:Its fluorescence lifetime is independent on the polymer chemical nature and on temperature,while being highly sensitive to the low mobility regime typical of cooperative segmental motions of rubbery polymers,close to the glass transition.The calibration curve obtained with five different polymers allows even nonexperts to assess local mobility in polymers with a single measurement.Fluorescence lifetime imaging microscopy(FLIM)yields quantitative mobility maps of complex and dynamic materials with sub-micrometric resolution.This robust and versatile tool allows access to polymer dynamics even in complex and responsive materials,in a broad temperature range,in real space and time.
基金Supported by the National Natural Science Foundation of China under Grant No 61177028
文摘Polymer field-effect transistors operated in the n-channel model with a top-gate/bottom-contact are processed using a solution method. The transistor performance depends on the gate dielectric layer. A high performance polymer transistor is achieved, with the saturated electron mobility of about 0.46cm2/Vs, threshold voltage nearly 0 V and subthreshold sway of about 0.9 V/decade, employing a polystyrene （PS） dielectric layer. The transistor performances are further improved with increasing current and lower operation voltages by utilizing a bi-layer gate dielectric, comprising a thin PS dielectric layer adjacent to the semiconductor to minimize the density of the interface traps for obtaining a small VT, a large μ and a poly（methyl methacrylate） （PMMA） dielectric layer with a relatively high-k adjacent to the gate electrode for enlarging the capacitance, processed from the orthogonal solvents.
基金the research programme of the Dutch Polymer Institute (DPI),project#623
文摘Dielectric relaxation spectroscopy（DRS） of poly（ε-caprolactone） with different draw ratios showed that the mobility of polymer chains in the amorphous part decreases as the draw ratio increases. The activation energy of the α process, which corresponds to the dynamic glass transition, increases upon drawing. The enlarged gap between the activation energies of the α process and the β process results in a change of continuity at the crossover between the high temperature a process and the α and β processes. At low drawing ratios the a process connects with the β process, while at the highest drawing ratio in our measurements, the a process is continuous with the αprocess. This is consistent with X-ray diffraction results that indicate that upon drawing the polymer chains in the amorphous part align and densify upon drawing. As the draw ratio increases, the α relaxation broadens and decreases its intensity, indicating an increasing heterogeneity. We observed slope changes in the α traces, when the temperature decreases below that at which τα≈ 1 s. This may indicate the glass transition from the ‘rubbery＇ state to the non-equilibrium glassy state.
