Investigation of the Assembly of Comb Block Copolymers in the Solid State

Comb block copolymers are a relatively new architecture of polymer whose assembly into ordered morphologies in the solid state is largely unexplored. Thirty-two comb block copolymers with molecular weights from 168 to 4200 kg mol⁻¹ were synthesized and assembled in the solid state into ordered morphologies with domain sizes as large as 138 nm. The individual structures of these polymers were studied by atomic force microscopy and scanning electron microscopy to identify their shapes. The solid-state morphologies of these polymers were imaged by scanning electron microscopy and small-angle X-ray scattering when permissible. Four phase maps were plotted from the 32 data points generated in this work to investigate how differences in polymer compositions affected the final morphologies. A clear relationship between the compositions of polymers and their morphologies was observed. The polymers were systematically altered to investigate the relationship between their compositions and the domain sizes of their morphologies. In one set of samples, the molecular weights of the arms were kept constant while the molecular weight of the backbone polymer was increased. In a second set of examples, the backbone polymer remained constant while the molecular weights of the arms were increased. While higher molecular weight polymers generally led to larger domain spacings in the microphase-separated structures, variations in the comb arm lengths resulted in dramatic changes in the observed solid-state morphologies. This paper is the first to provide a detailed study of a large series of comb block copolymers to relate their compositions to their assembled morphologies in the solid state.