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Bottlebrush polymers are complex macromolecules with tunable physical properties dependent on the chemistry and architecture of both the side chains and the backbone. Prior work has demonstrated that bottlebrush polymer additives can be used to control the interfacial properties of blends with linear polymers but has not specifically addressed the effects of bottlebrush side chain microstructures. Here, using a combination of experiments and self-consistent field theory (SCFT) simulations, we investigated the effects of side chain microstructures by comparing the segregation of bottlebrush additives having random copolymer side chains with bottlebrush additives having a mixture of two different homopolymer side chain chemistries. Specifically, we synthesized bottlebrush polymers with either poly(styrene- ran -methyl methacrylate) side chains or with a mixture of polystyrene (PS) and poly(methyl methacrylate) (PMMA) side chains. The bottlebrush additives were matched in terms of PS and PMMA compositions, and they were blended with linear PS or PMMA chains that ranged in length from shorter to longer than the bottlebrush side chains. Experiments revealed similar behaviors of the two types of bottlebrushes, with a slight preference for mixed side-chain bottlebrushes at the film surface. SCFT simulations were qualitatively consistent with experimental observations, predicting only slight differences in the segregation of bottlebrush additives driven by side chain microstructures. Specifically, these slight differences were driven by the chemistries of the bottlebrush polymer joints and side chain end-groups, which were entropically repelled and attracted to interfaces, respectively. Using SCFT, we also demonstrated that the interfacial behaviors were dominated by entropic effects with high molecular weight linear polymers, leading to enrichment of bottlebrush near interfaces. Surprisingly, the SCFT simulations showed that the chemistry of the joints connecting the bottlebrush backbones and side chains played a more significant role compared with the side chain end groups in affecting differences in surface excess of bottlebrushes with random and mixed side chains. This work provides new insights into the effects of side chain microstructure on segregation of bottlebrush polymer additives.
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Forcing single-chain nanoparticle collapse through hydrophobic solvent interactions in comb copolymers
We introduce a novel synthetic strategy in which high molecular weight comb copolymers with aliphatic side chains can collapse into single-chain nanoparticles (SNCPs) via photodimerization of anthracene under ultraviolet (UV) irradiation. By deliberately selecting hydrophobic comonomers with disparate solvency, we demonstrated that we could control chain collapse. We attribute these results to the formation of pseudo-unimicellar structures, whereby polyisobutylene (PIB) side chains are preferentially solvated, thereby compressing anthracene moieties to form a denser crosslinked core. The control of hydrophobic interactions is a common occurrence in proteins and we believe that our approach can be further extended to achieve multi-compartment SCNPs whereby each section is responsible for a given function.
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- Award ID(s):
- 1757220
- PAR ID:
- 10166243
- Date Published:
- Journal Name:
- Polymer Chemistry
- Volume:
- 11
- Issue:
- 2
- ISSN:
- 1759-9954
- Page Range / eLocation ID:
- 292 to 297
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/C9PY01235D
