Kozo Oka

Study of the crystal structure of titanylphthalocyanine by Rietveld analysis and intermolecular energy minimization method

Rietveld analysis and intermolecular energy minimization were used to refine the crystal structure parameters of one of the polymorphs of titanylphthalocyanine (TiOPc), which is a highly photosensitive pigment used in electrophotography. The most probable crystal structure is proposed to be a monoclinic unit cell, space group P21/c. The unit cell parameters are a=1.385 nm, b=1.392 nm, c=1.514 nm and β=120.22°. There are four molecules per unit cell.

Low-Energy Electronic States Related to Contact Electrification of Pendant-Group Polymers: Photoemission and Contact Potential Difference Measurement

Low-energy electronic states, 3-6 eV below the vacuum level, relevant to contact electrification of pendant-group polymers were investigated by means of photoemission and contact potential difference (CPD) measurements under atmospheric conditions. As a result, it was shown that the thresholds of photoemission of the polymers are related to their highest occupied molecular orbital (HOMO) levels derived from modified neglect of diatomic overlap (MNDO) molecular orbital calculation, and that the thresholds exist near the energy corresponding to their work function inferred from CPD measurement. Furthermore, it was found that the contact electrification of the polymers is related to their threshold of photoemission. These results are interpreted in terms of a molecular ion model proposed by Duke et al. [Phys. Rev. B 18 (1978) 5717].

Study of the Crystal Structure of Titanylphthalocyanine by Rietveld Analysis. II

Rietveld analysis with the Monte Carlo method was used to estimate the crystal structure parameters of one of the polymorphs of titanylphthalocyanine (TiOPc). This polymorph is called TiOPc type C (C-TiOPc), and it is a low-photosensitive pigment used in electrophotograpy. In order to determine the relationship between crystal structure and photosensitivity, the crystal structure of C-TiOPc was estimated. The most probable crystal structure is a monoclinic unit cell, space group Cc: a=2.519 nm, b=0.385 nm, c=2.546 nm, β=90.3°, Z=4, dcalc.=1.54 g/cm3.

Molecular Dynamics Studies of Amorphous Poly(Tetrafluoroethylene)

Abstract Force field parameters for amorphous poly(tetrafiuoroethylene) (PTFE) and perfluoroalkanes for molecular simulations are developed using four perfluoroalkanes (C3F8, n-C4F10, n-C5F12 and n-C6F14) as reference molecules. Molecular dynamics calculations of the amorphous PTFE are performed under constant temperature and constant pressure conditions. Surprisingly, more than 6 ns calculations are needed to equilibrate the system. The calculated density and the structure factor are in good agreement with experiment. The concentration of the trans conformation of the backbone corresponds closely to that estimated from a Boltzmann distribution. The determined force field parameters are confirmed to reproduce the realistic amorphous structure of PTFE. The molecular motions of the backbones are investigated by tracing the time evolutions of the dihedral angles and several types of the conformational changes are observed.