ABSTRACT
A donor-acceptor polymer semiconductor, PDQT, comprising diketopyrrolopyrrole (DPP) and ß-unsubstituted quaterthiophene (QT) for organic thin film transistors (OTFTs) is reported. This polymer forms ordered layer-by-layer lamellar packing with an edge-on orientation in thin films even without thermal annealing. The strong intermolecular interactions arising from the fused aromatic DPP moiety and the DPP-QT donor-acceptor interaction facilitate the spontaneous self-assembly of the polymer chains into close proximity and form a large π-π overlap, which are favorable for intermolecular charge hopping. The well-interconnected crystalline grains form efficient intergranular charge transport pathways. The desirable chemical, electronic, and morphological structures of PDQT bring about high hole mobility of up to 0.97 cm(2)/(V·s) in OTFTs with polymer thin films annealed at a mild temperature of 100 °C and similarly high mobility of 0.89 cm(2)/(V·s) for polymer thin films even without thermal annealing.
ABSTRACT
A series of star-shaped organic semiconductors have been synthesized from 1,3,6,8-tetrabromopyrene. The materials are soluble in common organic solvents allowing for solution processing of devices such as light-emitting diodes (OLEDs). One of the materials, 1,3,6,8-tetrakis(4-butoxyphenyl)pyrene, has been used as the active emitting layer in simple solution-processed OLEDs with deep blue emission (CIE = 0.15, 0.18) and maximum efficiencies and brightness levels of 2.56 cd/A and >5000 cd/m(2), respectively.
ABSTRACT
The objective of this study was to evaluate the physicomechanical properties of a series of polyhedral silsesquioxane (SSQ) methacrylate monomers developed for dental applications. The effect of chain modifications on the properties of the SSQ-based monomers was also evaluated. Physicomechanical properties that are investigated include polymerization shrinkage, degree of conversion, hardness, and modulus. Results obtained were compared with unfilled 1:1 (control) bis-GMA/TEGDMA materials (typical monomers used in dental composites). All samples investigated were cured using 400-500 nm light at 500 mW/cm(2) for 40 s. Shrinkage associated with curing and post-gel reactions for all synthesized SSQ compounds were found to range from (0.04 +/- 0.01)% to (0.33 +/- 0.03)% with degree of conversion ranging from (56.68 +/- 2.81)% to (84.53 +/- 2.62)%. At all time intervals, post-gel shrinkage associated with control was found to be significantly greater than all SSQ compounds. No significant difference in degree of conversion was observed for control, and all SSQ compounds except for SSQ attached with eight equivalents of short-chain methacrylate. Mechanical properties associated with SSQ compounds were found to be significantly lower than control. However, through chain modifications, mechanical properties of SSQ compounds can be improved by approximately 50%.
