Synthesis and Phase-Separation Behavior of a,x-Difunctionalized Diblock Copolymers

A series of diblock copolymers of n-pentyl methacrylate and methyl methacrylate (PPMA/PMMA BCP) with one or two terminal functional groups was prepared by sequential anionic polymerization of PMA and MMA using an allyl-functionalized initiator and/or and end-capping with allyl bromide. Allyl functional groups were successfully converted into OH groups by hydroboration. The morphology in bulk was examined by temperature-dependent small-angle X-ray measurements (T-SAXS) and transmission electron microscopy (TEM) showing that functional groups induced a weak change in d-spacings L-0 as well as in the thermal expansion behavior. T-SAXS proved that the lamellar morphologies were stable over multiple heating cooling cycles without order-disorder transition (ODT) until 300 degrees C. While non-functionalized BCP formed parallel lamellae morphologies, additional OH-termination at the PMMA block forced in very thin films (ratio between film thickness and lamellar d-spacing below 1) the generation of perpendicular lamellae morphology through the whole film thickness, as shown by Grazing-incidence small-angle X-ray scattering experiments (GISAXS) measurements. Functionalized BCP were successfully used in thin films as templates for silica nanoparticles in an in-situ sol-gel process.