Correlation between phase behavior and tensile properties of diblock copolymers

The phase behavior of poly(styrene-b-butyl methacrylate), PS-b-PBMA, dibloc k copolymers was investigated by small-angle neutron scattering (SANS), neu tron reflectometry (NR), and rheology. For a symmetrical P(dS-b-nBMA) diblo ck copolymer a lower critical order transition (LCOT) at 155 degrees C was found by SANS and rheology. Furthermore, the temperature-dependent interact ion parameter was determined in the temperature regime between 110 and 145 degrees C from fits to the scattering curves in the disordered region. The interaction parameter increases with increasing temperature and shows a wea k temperature dependence. The LCOT behavior thus is expected to be a large entropic contribution to chi. The interfacial width observed by NR is relat ively large compared to other diblock copolymers. Different block copolymer s were investigated with respect to the influence of miscibility on tensile properties. While poly(styrene-b-butyl methacrylate) diblock copolymers sh ow significant synergistic effects on tensile properties, for poly(methyl m ethacrylate-b-butyl methacrylate) diblock copolymers no significant synergi stic effects on tensile properties were observed due to the increased inter action parameter and the smaller interfacial width as compared to the care of PS-b-PBMA diblock copolymers.