Hidetoshi Tomita

Structural analysis of polyhydroxyurethane obtained by polyaddition of bifunctional five-membered cyclic carbonate and diamine based on the model reaction

This article focuses on the structural analysis of polyhydroxyurethane obtained by the reaction of 2,2-bis[p-(1,3-dioxolan-2-one-4-yl-methoxy)phenyl]]propane with a diamine based on the model reaction. The compounds obtained in the model reaction could be separated into hydroxyurethanes containing primary and secondary alcohol groups by preparative gel permeation chromatography with a recycling technique to determine the structures by 1 H NMR, 13 C NMR, distortionless enhancement by polarization transfer (DEPT) and C-H correlation spectroscopy to obtain hydroxyurethane carrying the primary alcohol structure moiety dominantly. The ratios were independent of the reaction temperature but somewhat dependent on the solvents and amines.

Polyaddition behavior of bis(five- and six-membered cyclic carbonate)s with diamine

Polyadditions of 1,2-bis[3-(1,3-dioxan-2-one-5-yl)-propylthio]ethane (B6CC) and 1,2-bis[4-(1,3-dioxolan-2-one-4-yl)-butylthio]ethane (B5CC) with 4,9-dioxadodecane-1,12-diamine were carried out. The reactivity of B6CC with the diamine was higher than that of B5CC. Additionally, B6CC gave a higher molecular weight polymer than B5CC. The reaction-rate constants of B6CC and B5CC at 30, 50, and 70 °C were evaluated as 0.70, 0.89, and 1.07 L/mol · h; and 0.03, 0.06, and 0.10 L/mol · h in N,N-dimethylacetamide (initial reagent concentration 0.5 M), respectively. The activation energies were estimated to be 9.2 and 24.9 kJ/mol in the reactions of B6CC and B5CC with the diamine, respectively.

Reactivity comparison of five- and six-membered cyclic carbonates with amines: Basic evaluation for synthesis of poly(hydroxyurethane)

The reaction of six- and five-membered cyclic carbonates, 5-(2-propenyl)-1,3-dioxan-2-one (1) and 4-(3-butenyl)-1,3-dioxolan-2-one (2) with hexylamine and benzylamine was carried out in N,N-dimethylacetamide at 30, 50, and 70 °C. The six-membered cyclic carbonate 1 proceeded quantitatively with hexylamine at 30 °C for 24 h, while the five-membered cyclic carbonate 2 converted in 34%. The reaction rate constants at 50 °C are evaluated as follows; 1.42 L/mol · h (1 with hexylamine) > 0.29 L/mol · h (1 with benzylamine) > 0.04 L/mol · h (2 with hexylamine) > 0.01 L/mol · h (2 with benzylamine). The activation energies in the reactions of 1 and 2 with hexylamine were estimated to be 10.1 and 24.6 kJ/mol, respectively. The ring-strain energy was calculated by the semi-empirical method using the PM3 Hamiltonian. The ring-strain energy of the six-membered cyclic carbonate was 2.86 kcal/mol larger than that of five-membered one.

Command surfaces 14 [1]. Photoregulation of in-plane alignment of a liquid crystal by the photoisomerization of stilbenes chemisorbed on a substrate silica surface

Abstract Stilbenes were attached to a quartz surface at their 2-position by silylation through a spacer to determine the capability to regulate an azimuthal alignment of a nematic liquid crystal by irradiation with linearly polarized light. Liquid crystal molecules aligned perpendicular to the direction of polarization plane of the actinic light, just as in the case of surface azobenzenes. The efficiency of the photoregulation was influenced by excitation wavelength and hence related with an E/Z isomeric ratio in a photostationary state. The irradiation with 260 nm polarized light resulting in the E-isomer as a major component in the photostationary state gave better optical quality of a photoaligned texture when compared with 330 nm irradiation, suggesting that the orientation of liquid crystals is induced by the rod-like E-isomer. Discussion was made on the possibility of the role of phenanthrenes, which were formed upon prolonged irradiation, in the liquid crystal photoalignment.

Command surfaces 15 [1]. Photoregulation of liquid crystal alignment by cinnamoyl residues on a silica surface

Abstract The surface of a silica substrate plate was modified with a cinnamate moiety having a triethoxysilyl group at the ortho-position through a spacer. The plate was employed to assemble a cell filled with a nematic liquid crystal and exposed to linearly polarized 259 nm light to obtain homogeneous alignment. The direction of the alignment was perpendicular to an electric vector of the actinic light. On the contrary, the exposure of the cell to polarized light at 330 nm did not result in homogeneous alignment while the actinic light caused the disappearance of the chromophore. This wavelength effect on the azimuthal photoalignment suggests that the surface-assisted liquid crystal orientation is triggered by the reorientation of the E-isomer of the cinnamate group. This is in marked contrast to a proposed mechanism of a photoalignment by a thin film of a poly(vinyl cinnamate) derivative (Schadt et al., 1993, Jpn J. appl. Phys., 31, 2155); homogeneous alignment is induced by the axially selective photod...

Photoregulation of Liquid Crystal Alignment by Photoisomerizable Molecular Layers

Abstract Linearly polarized UV light irradiation of a nematic liquid crystal cell assembled with a quartz plate surface-modified with a stilbene caused reversible reorientation of liqquid crystal molecules.