Ultrapure blue-fluorescent molecules based on thermally activated delayed fluorescence are developed. Organic light-emitting diode (OLED) devices employing the new emitters exhibit a deep blue emission at 467 nm with a full-width at half-maximum of 28 nm, CIE coordinates of (0.12, 0.13), and an internal quantum efficiency of ≈100%, which represent record-setting performance for blue OLED devices.

The development of a one-step borylation of 1,3-diaryloxybenzenes, yielding novel boron-containing polycyclic aromatic compounds, is reported. The resulting boron-containing compounds possess high singlet-triplet excitation energies as a result of localized frontier molecular orbitals induced by boron and oxygen. Using these compounds as a host material, we successfully prepared phosphorescent organic light-emitting diodes exhibiting high efficiency and adequate lifetimes. Moreover, using the present one-step borylation, we succeeded in the synthesis of an efficient, thermally activated delayed fluorescence emitter and boron-fused benzo[6]helicene.

Triphenylene-based electron transport materials (ETMs), designated Bpy-TP1-4, with a coplanar molecular structure and a large electron affinity were designed and synthesized for use in organic lightemitting diodes (OLEDs). Spectroscopic ellipsometry measurements clarified that the deposited thin films of these ETMs have optical anisotropy, indicating that the molecules in the deposited thin films tend to be mostly oriented parallel to the substrate. Green OLEDs containing these ETMs allowed a lower driving voltage than that for OLEDs containing tris(8-hydroxyquinolinato)aluminum (Alq 3 ) with a random orientation. In particular, the OLED containing Bpy-TP2 showed a significantly lower driving voltage, achieving lower power consumption when compared with conventional ETMs such as Alq 3 and 1,3,5-tris(2-phenyl-1H-benzo[d]imidazol-1-yl)benzene (TPBi). Also, the operational lifetime of a blue OLED containing Bpy-TP2 is equivalent to that of an OLED with TPBi. The increased driving voltage of the device containing Bpy-TP2 is significantly suppressed compared to that of the OLED containing TPBi.

Polyesters are biodegradable analogues of polypeptides, but their biochemical applications have been hampered by the lack of a method to analyze polyester conformation in a solution state. We have demonstrated that vibrational circular dichroism (VCD) spectroscopy can conveniently and accurately elucidate the conformation of polyesters through the studies on poly(l-lactic acid) (PLLA), PLLA-amylose complex, and oligo(l-lactic acid). The analysis of VCD exciton couplet of these molecules has clarified the stable left-handed helical structure of PLLA, while density functional theory calculations of oligo(l-lactic acid) have revealed its detailed structural nature.

In this study, we found that amylose-poly(glycolic acid-co-e-caprolactone) (P(GA-co-CL)) inclusion complexes were formed when phosphorylase-catalyzed enzymatic polymerization was performed in the presence of biodegradable P(GA-co-CL)s according to a vine-twining polymerization process. The X-ray diffraction patterns of the products showed the typical diffraction peaks due to inclusion complexes composed of amylose and guest compounds. In addition, the 1 H NMR spectra of the products showed the signals due to amylose and P(GA-co-CL), in spite of washing with good solvents for P(GA-co-CL), such as acetone and chloroform. These results suggested that the products were inclusion complexes composed of amylose and P(GA-co-CL). The compositional ratio of GA unit to CL unit in P(GA-co-CL)s did not affect the inclusion behavior of amylose. On the other hand, the results in the vine-twining polymerization using amorphous P(GA-co-CL)s and a crystalline poly(glycolic acid-block-ecaprolactone) (P(GA-b-CL)) as guest polymers indicated that the crystallinity of the guest copolymers strongly affected the formation of inclusion complexes with amylose. In addition, we found that lipase-catalyzed hydrolysis of P(GA-co-CL) in the inclusion complex was partly inhibited, probably because amylose, which surrounded P(GA-co-CL), prevented the approach of lipase.