Influence of Molecular Architecture and Chain Flexibility on the Phase Map of Polystyrene-block-poly(dimethylsiloxane) Brush Block Copolymers

• Published in: Macromolecules 2019-09, Vol.52 (17), p.6449-6457
• Main Authors: Fei, Hua-Feng, Yavitt, Benjamin M, Hu, Xiyu, Kopanati, Gayathri, Ribbe, Alexander, Watkins, James J
• Format: Article
• Language: English
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.9b00843

We report the microphase-separated morphologies of model bottlebrush block copolymers (BBCPs) over a wide range of architectural design parameters. Densely grafted polystyrene-block-poly­(dimethylsiloxane) (PS-b-PDMS) BBCPs rapidly self-assemble into ordered lamellar, cylindrical, and deformed spherical morphologies depending on the volume fraction (f), side chain length (N sc), and overall backbone length (N bb). The microstructure was characterized by using electron microscopy and X-ray scattering. An experimental phase map is constructed, describing the dependence of morphologies and order–order transitions with respect to the design parameters. A lamellar morphology is primarily observed at symmetric f, while ordered cylindrical and deformed spherical morphologies appear at asymmetric f. The relative flexibility of the PS-b-PDMS backbone facilitates the accessibility of morphologies with curved interfaces and exceptionally large domain spacing. We also find that the breadth of the lamellar window decreases with increasing backbone length and side-chain asymmetry. These findings provide a comprehensive experimental description of the PS-b-PDMS BBCPs and provide insight into the rich phase behavior of this class of macromolecules.