| 초록 |
Hydrophobically end capped polyethylene oxide urethane resins, HEUR, with different number of hydrocarbon and different molecular weight of polyethylene oxide main chain form the micelle after the critical micellization concentration, CMC. The CMC values had transition point with alkyl carbon number 12 at molecular weight 2000 whereas CMC values decreased along alkyl carbon number at molecular weight 4000. To understand these phenomena, we performed molecular dynamics simulation with MM3 force field. We made HEUR molecular models which have different number of hyadrocarbons, 8, 12, and 18, and different polyethylene oxide chain lengths, 2000, 4000, and 10000. The values of radius of gyration presenting hydrophobic magnitude and micelle formation enthalpy is increased with alkyl carbon number whereas the values of end-to-end distance and characteristic ration presenting chain flexibility and entropy of HEUR is decreased with alkyl carbon number. These simulation results clearly explain the light scattering and neutron scattering experimental results. In that, the enthalpy factor is dominate at the molecular weight of 2000 but entropy factor is strong at the molecular weight of 4000. |
