As phase separation between the small-molecule semiconductor and the polymer binder is the key enabler of blend-based organic field-effect transistors(OFETs)fabricated by low-cost solution processing,it is crucial to ...As phase separation between the small-molecule semiconductor and the polymer binder is the key enabler of blend-based organic field-effect transistors(OFETs)fabricated by low-cost solution processing,it is crucial to understand the underlying phase separation mechanisms that determine the phase morphology,which significantly impacts device performance.Beyond the parameter space investigated in previous work,here we investigate the formation of blends by varying the branch architecture of the polymer binder and by shortening the solvent dry time using ultrasonic spray casting.The phase morphologies of the resulting blend films have been thoroughly characterized with a variety of techniques in three dimensions over multiple length scales,including AFM,energy-filtered transmission electron microscope,and neutron reflectivity,and have been correlated with electrical transport performance.From the results,we have inferred that the phase morphology is kinetically determined,limited by the inherent slow movement of polymer macromolecules.The kinetic picture,supported by molecular dynamics modeling,not only consistently explains our observations but also resolves inconsistencies in previous works.The achieved mechanistic understanding will guide further optimization of blend-based organic electronics,such as OFETs and organic photovoltaics.展开更多
In this paper the physical influences on the mechanical behavior of a Polyamide 6 (PA 6)/Mont- morillonit (MMT)-nanocomposite are examined by a selected structure modification in a numerical parameter study. Experimen...In this paper the physical influences on the mechanical behavior of a Polyamide 6 (PA 6)/Mont- morillonit (MMT)-nanocomposite are examined by a selected structure modification in a numerical parameter study. Experimental data of tensile tests of three different volume fractions at ambient temperature are used as reference. These were compared to homogenized stress-strain curves calculated with 3D representative volume elements (RVE) under periodic boundary conditions, in which the curve areas are considered until the tensile yield strength is reached. Besides the influence of filler orientation, exfoliation and its volume fraction, both adhesive interface behavior between the filler and matrix, and local partially crystalline interphases around the MMT-plates were also taken into account. A good approximation of the numerical representation of the experimental curves was achieved only after the introduction of the 30 - 40 nm thick partially crystalline interphases with higher stiffness and strength around the MMT-plates. The use of an exclusively isotropic matrix led to an underestimation of the mechanical values. The local modifications of the morphology were assumed to be transversely isotropic both in the elastic and in the plastic region. The transverse plane is defined by the lateral particle surface. Compared with the experimentally determined values of the corresponding Young’s Modulus, an excellent correlation was achieved. The yield strength for the largest volume fraction shows the best agreement with experimental values.展开更多
文摘As phase separation between the small-molecule semiconductor and the polymer binder is the key enabler of blend-based organic field-effect transistors(OFETs)fabricated by low-cost solution processing,it is crucial to understand the underlying phase separation mechanisms that determine the phase morphology,which significantly impacts device performance.Beyond the parameter space investigated in previous work,here we investigate the formation of blends by varying the branch architecture of the polymer binder and by shortening the solvent dry time using ultrasonic spray casting.The phase morphologies of the resulting blend films have been thoroughly characterized with a variety of techniques in three dimensions over multiple length scales,including AFM,energy-filtered transmission electron microscope,and neutron reflectivity,and have been correlated with electrical transport performance.From the results,we have inferred that the phase morphology is kinetically determined,limited by the inherent slow movement of polymer macromolecules.The kinetic picture,supported by molecular dynamics modeling,not only consistently explains our observations but also resolves inconsistencies in previous works.The achieved mechanistic understanding will guide further optimization of blend-based organic electronics,such as OFETs and organic photovoltaics.
文摘In this paper the physical influences on the mechanical behavior of a Polyamide 6 (PA 6)/Mont- morillonit (MMT)-nanocomposite are examined by a selected structure modification in a numerical parameter study. Experimental data of tensile tests of three different volume fractions at ambient temperature are used as reference. These were compared to homogenized stress-strain curves calculated with 3D representative volume elements (RVE) under periodic boundary conditions, in which the curve areas are considered until the tensile yield strength is reached. Besides the influence of filler orientation, exfoliation and its volume fraction, both adhesive interface behavior between the filler and matrix, and local partially crystalline interphases around the MMT-plates were also taken into account. A good approximation of the numerical representation of the experimental curves was achieved only after the introduction of the 30 - 40 nm thick partially crystalline interphases with higher stiffness and strength around the MMT-plates. The use of an exclusively isotropic matrix led to an underestimation of the mechanical values. The local modifications of the morphology were assumed to be transversely isotropic both in the elastic and in the plastic region. The transverse plane is defined by the lateral particle surface. Compared with the experimentally determined values of the corresponding Young’s Modulus, an excellent correlation was achieved. The yield strength for the largest volume fraction shows the best agreement with experimental values.
