Molecular dynamics simulation of dielectric polymers

2004 Fiscal Year Final Research Report Summary

• Project/Area Number: 15607009
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 計算科学
• Research Institution: KANAZAWA UNIVERSITY
• Principal Investigator: HIWATARI Yasuaki Kanazawa Univ., Natural Science & Technology, Professor, 自然科学研究科, 教授 (20019491)
• Project Period (FY): 2003 – 2004
• Keywords: molecular dynamics simulation / dielectric properties / polymers

Research Abstract

Application of molecular dynamics simulation to industry is another important role in addition to various basic researches in science and technology. Two examples have been studied here.
(1)A molecular dynamic study of a nanoparticle-composite polymer has been carried out to investigate key parameters which control fundamental properties of polymers such as glass transition temperature, thermal expansion coefficient, specific heat etc.
(2)The second study is one for the material design of dielectric polymers, such as a portable phone in near future which works in a much higher frequency domain than presently used one and consequently makes possible faster and more massive communication at once. For these purposes we study here complex dielectric properties of a polymer by molecular dynamics simulations. As far as the dielectric constant is concerned, the charge distribution of polymers is essential. However the introduction of charges into any molecular simulation systems must be a time consuming problem in comparison with the case without charges. Then to avoid this time consuming problem here we take a simple polymer model which do not incorporate charges, and instead assume inherent positive and negative charges in corresponding bases in polymers but do not take into consideration these charges positively in molecular dynamics simulation, which make it possible to define intra dipole moments in each polymer molecule. The summation of these intra dipole moments gives rise to define the total dipole of each polymer molecule. In this study we only consider the case in which such dipoles of each polymer are orientated along the molecular bonds irrespective the direction, which is often called type A. In the present model the bending motion of two successive dipole moments is taken into consideration. This mode is particularly important in the frequency region as high as an order of GHz, corresponding to the case of our main concerns. We note that neglecting such a freedom of bending motion is not a proper model.