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Effect of side chain and backbone length on lamellar spacing in polystyrene-block-poly(dimethyl siloxane) brush block copolymers

Fei, Huafeng; Yavitt, Benjamin M.; Kopanati, Gayathri; Watkins, James J.

By 27 January 2020No Comments

Journal of Polymer Science Part B: Polymer Physics, 2019, vol 57, 11, pp. 691-699



We report the synthesis of polystyrene-block-poly(dimethyl siloxane) (PS-b-PDMS) brush block copolymers (BBCPs) through sequential ROMP of norbornene-modified macromonomers (-NB) and explore the effect of side chain length (Nsc) and total backbone degree of polymerization (Nbb) on the self-assembly of lamellar morphologies. Group I (PS-NB Mn = 2.9 kg/mol, PDMS-NB Mn = 4.8 kg/mol) exhibits asymmetric side chains, while Group II (PS-NB Mn = 4.7 kg/mol, PDMS-NB Mn = 4.8 kg/mol) possess a more symmetric arrangement. Both families rapidly self-assemble into well-ordered lamellar morphologies with domain spacings (d0) ranging from d0 = 54 to 140 nm. The scaling relationship between d0 and Nbb (d0 Nbb?) was determined as the measure of backbone flexibility. Exponents of ? = 0.71 and ? = 0.81 are observed for Groups I and II, respectively, indicating the BBCPs adopt an extended backbone conformation. The presence of a low Tg side chain such as PDMS increases apparent flexibility of the backbone. The interplay between contrasting characteristics of the side chains is discussed and reveals the importance of understanding the physical consequences of block architecture on controlling BBCP assembly. These findings provide necessary information for future investigations of complex phases and well-defined nanostructures fabricated using the brush architecture. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 691–699

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