|Budget Amount *help
¥3,900,000 (Direct Cost : ¥3,900,000)
Fiscal Year 1999 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1998 : ¥3,400,000 (Direct Cost : ¥3,400,000)
Macromolecules, such as synthetic polymers, proteins, and DNAs, have attracted great attention due to their novel properties that have never been studied for usual low molecular mass substances. Especially the macromolecular, ordering is of great interest since it is a fundamental process involved in polymer crystallization, protein folding, etc. We have here investigated the molecular processes of macromolecular ordering by experiments and computer simulations.
We have first investigated the molecular mechanism of secondary nucleation on a growth surface of the polymer crystal. We adopt a simplified model of polyethylene molecule made of 500 beads connected by springs, and consider the crystallization from a vapor phase neglecting surrounding molecules. A strongly collapsed chain in a vacuum was placed near the infinitely wide lateral-surface of the polymer crystal, and the molecular processes of adsorption and ordering were investigated by molecular dynamics simulation. It was found t
hat the polymer chain is quickly adsorbed, in a stepwise manner, to form a layer structure : a multilayered at lower temperature and a monolayered at higher temperature. The chain segments adsorbed to the surface align parallel with each other and gradually, within several ns, grow into a neat chain folded lamella with predominantly adjacent-reentry folds. The thickness of the lamella sensibly depends on the crystallization temperature and shows a rapid increase around the melting point.
The chain molecules, such as n- alkanes, are recently found to show monolayers or bilayers on free surface of the liquid. We have also investigated, by molecular dynamics simulation, the surface crystallization, monolayer formation, and chain diffusion within the monolayer and between the monolayer and the sustaining melt phase.
Beside these works on polymer ordering, we have made investigations on the structural phase transitions in polymer crystals both by experimental methods and by computer simulation.