Manipulating ordering transitions in interfacially modified block copolymers

Abstract

We report a synthetic strategy that allows us to manipulate the interfacial region between blocks and control ordering transitions in poly(isoprene-b-styrene) [P(I-S)] block copolymers. This interfacial modification is accomplished by combining a semi-batch feed with anionic polymerization techniques. Using this approach, we are able to control the segmental composition and molecular interactions in our phase-separated block copolymers, independent of molecular weight and block constituents. A library of copolymers is prepared with various interfacial modifications to examine the effect of interfacial composition on copolymer self-assembly. The morphological characteristics of the self-assembled structures are investigated using small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and dynamic mechanical analysis (DMA). Normal and inverse tapered block copolymers, containing approximately 15–35 vol% tapered material, show a measurable decrease in the order–disorder transition temperature (T_ODT) relative to the corresponding non-tapered diblock copolymers, with the inverse tapered materials showing the greatest deviation in T_ODT. Additionally, T_ODT was inversely related to the volume fraction of the tapered region in both normal and inverse tapered copolymer materials.