Block copolymer (BCP) self-assembly has many promising applications, including nanolithography, nanotemplating, drug delivery, and membrane filtration. The material properties of BCPs are highly reliant on three parameters: degree of polymerization (N), Flory-Huggins parameter (χ), and volume fraction of different polymers (f). To improve the tunability of BCP self-assembly and the processability of BCP materials in such applications, it is desirable to introduce independent tuning parameters, enabling greater flexibility in the phase behaviors and material properties that can be achieved given a particular polymer combination. In this work, we demonstrate that Janus bottlebrush BCPs (BBCPs) synthesized via ring-opening metathesis polymerization (ROMP) of poly(lactic acid) (PLA) and polydimethylsiloxane (PDMS) containing branched macromonomers offer such tunability, with N of the side chains dictating the domain spacings achieved and N of the backbone independently controlling the fluidity of the bulk material, particularly important for nanotemplating applications. BBCPs of varying Nbackbone were synthesized with both disperse and discrete oligomer side chains. Small angle X-ray scattering measurements revealed domain spacings ranging from 7.73 nm in a BBCP of discrete-discrete oDMS15-branch-oLA16 to 5.68 nm in a BBCP of disperse-discrete PDMS1k-branch-oLA8. Bulk BBCPs ranged from sticky liquids for low Nbackbone (~10) to solids for high Nbackbone (~200). Further investigations with additional polymer combinations demonstrated the universality of utilizing Janus BBCP architecture for achieving independent tuning parameters.

Synthesis and assembly of (A-branch-B)n Janus bottlebrush polymers with ultra-small domain size

255th National Meeting (2018)

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