Morphological Behavior of Compositionally Gradient Polystyrene–Polylactide Bottlebrush Copolymers
Morphological behavior of PS–PLA bottlebrush copolymers with a compositional gradient along the backbone was investigated by small-angle X-ray scattering (SAXS) analysis and compared to that of their block copolymer analogs. Side chain-symmetric gradient copolymers with varying volume fractions were...
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Published in | Macromolecules Vol. 52; no. 21; pp. 8217 - 8226 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
United States
American Chemical Society
12.11.2019
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Subjects | |
Online Access | Get full text |
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Summary: | Morphological behavior of PS–PLA bottlebrush copolymers with a compositional gradient along the backbone was investigated by small-angle X-ray scattering (SAXS) analysis and compared to that of their block copolymer analogs. Side chain-symmetric gradient copolymers with varying volume fractions were prepared by one-step ring-opening metathesis polymerization of the corresponding exo- and endo-norbornene-functionalized macromonomers of similar lengths. The morphological map constructed using the SAXS data revealed a wide cylindrical morphology window, including for symmetric compositions, well-ordered lamella morphologies at very low PS volume fractions, and the formation of a rare bicontinuous gyroid morphology. In addition to the highly asymmetric nature of the morphology diagram, the domain spacings obtained for gradient bottlebrush copolymers were significantly smaller (by 30–40%) than the corresponding bottlebrush block copolymer analogs, which was attributed to a nonperpendicular orientation of the gradient bottlebrush backbone at the domain interface. Side chain-asymmetric gradient bottlebrush copolymers were synthesized from PS and PLA macromonomers of different lengths and were demonstrated to assemble into well-ordered cylindrical and lamella morphologies. The results of these studies demonstrate that the gradient interface plays an important role in determining molecular packing during bottlebrush copolymer self-assembly. A rich morphological behavior of the gradient bottlebrush copolymers combined with their “user-friendly” one-step synthesis provides a robust and versatile platform for nanostructured material-design and fabrication. |
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Bibliography: | USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities Division SC0012704; DMR-1709371; DMR-0520547; 654000 BNL-212415-2019-JAAM |
ISSN: | 0024-9297 1520-5835 |
DOI: | 10.1021/acs.macromol.9b01756 |