Closed-loop phase behavior of polystyrene-block-poly(n-pentyl methacrylate) copolymers with various block length ratios
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- Closed-loop phase behavior of polystyrene-block-poly(n-pentyl methacrylate) copolymers with various block length ratios
- Ryu, DY; Lee, DH; Jeong, U; Yun, SH; Park, Soojin; Kwon, K; Sohn, BH; Chang, T; Kim, JK; Russell, TP
- Block length; Closed-loop; Disorder-to-order transition; Phase behavior
- Issue Date
- AMER CHEMICAL SOC
- MACROMOLECULES, v.37, no.10, pp.3717 - 3724
- The phase behavior of polystyrene-block-poly(n-pentyl methacrylate) copolymers [PS-PnPMA] having various block length ratios was investigated by rheology, transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS). All of the PS-PnPMA exhibited two transitions: the lower disorder-to-order transition (LDOT) and upper order-to-disorder transition (UODT) occurring at a lower and higher temperature, respectively. Thus, PS-PnPMA is characterized by a closed-loop type of phase behavior. As the volume fraction of PS in PS-PnPMA was decreased from 0.5 to 0.23, the microdomains observed between the LDOT and UODT changed from lamellae (LAM) to hexagonally packed cylinders (HEX) and finally to body-centered-cubic spheres (BCC), similar to other block copolymers exhibiting only an order-to-disorder transition. The rheological properties depended strongly on the type of microdomains within the closed-loop. The storage and loss moduli (G′ and G″) within the closed loop are the highest for a PS-PnPMA having a BCC morphology, then HEX morphology, and the lowest for LAM morphology.
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