| 초록 |
A polystyrene-block-poly(n-pentyl methacrylate)(PS-b-PnPMA) was fractionated sequentially into 5 fractions(F1,F2,F3,F4,andF5) by interaction chromatography,where the molecular weight distributions and compositions. The phase behavior for 5 fractions was investigated by depolarized light scattering measurement and optical microscopy. Within temperature range investigated from 110 to 250oC, even though the mother copolymer (Fm) showed the disordered state, ordered structure was obtained for F1,F2 due to the increased molecular weight and disordered structure for F4 ,F5 due to the decreased molecular weight, whereas F3 showed the closed-loop phase transition. It was found that the closed-loop phase transition of PS-b-PnPMA is quite sensitive to the molecular weight rather than composition, however, compared with Fm whose molecular weight and composition are close to F3, closed-loop phase transition observed for F3 is attributed to narrower distribution. |
