| 초록 |
Hydrophobically end capped polyethylene oxide urethane resins, HEURs, with different number of hydrocarbons and different molecular weight of polyethylene oxide, PEO, main chains form the micelle after the critical micellization concentration, CMC. The HEURs were prepared by reaction between PEO and 8, 12, 18 isocynates. The substitution ratio between PEO main chains and hydrocarbon side chains was characterized with FT-IR method. In static fluorescence experiment, 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 hydrocarbons, 8, 12, and 18, and different polyethylene oxide chain lengths, 2000, 4000. The values of radius of gyration presenting hydrophobic magnitude and micelle formation enthalpy are increased with alkyl carbon numbers whereas the values of end-to-end distance and characteristic ration presenting chain flexibility, that is, entropy of HEUR are decreased with alkyl carbon number. From these results, micelle formation mechanism was seriously affected by molecular flexibility and molecular hydrophobicity. |
