The phase diagram of the system poly(styrene-block-n-butyl methacrylate)

The morphological phase diagram of poly(styrene-block-n-butyl methacrylate), P(S-b-n-BMA), has been investigated in detail using thermal analysis, microscopy, rheology and scattering techniques. The system shows an upper critical order transition as well as a lower critical order transition (LCOT). For the first time, morphologies of the ordered system at higher temperatures (LCOT) as well as of a block copolymer system frozen-in during the phase separation process are reported. The Flory-Huggins interaction parameter, chi depends not only on temperature, but also on the composition and the molecular weight of the block copolymers, resulting in an asymmetrical phase diagram. Furthermore, the deuteration of the PS block seems to increase the II parameter of the P[(dg)S-b-n-BMA] system, reflecting the influence of small changes in architecture on phase behavior. The phase behavior and morphology of PS-b-PBMA are summarized in a phase diagram which is, however, quite complex and therefore needs further discussion. The equilibrium morphologies displayed are influenced by the temperature-dependent-conformation term as well as by the composition term.