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Macromolecular architecture is a critical parameter when tuning polymer material properties. Although the implementation of non-linear polymers in different applications has grown over the years, polymer grafted surfaces such as nanoparticles have traditionally been composed of linear thermoplastic polymers, with a limited number of examples demonstrating a diversity in polymer architectures. In an effort to combine polymer architecturally dependent material properties with polymer grafted particles (PGPs), as opposed to conventional methods of tuning polymer grafting parameters such as the number of chains per surface area (i.e., polymer graft density), a series of bottlebrush grafted particles were synthesized using surface-initiated ring-opening metathesis polymerization (SI-ROMP). These bottlebrush PGPs are composed of glassy, semi-crystalline, and elastomeric polymer side chains with controlled backbone degrees of polymerization (Nbb) at relatively constant polymer graft density on the surface of silica particles with diameters equaling approximately 160 or 77 nm. Bottlebrush polymer chain conformations, evaluated by measuring the brush height of surface grafted polymer chains in solution and the melt, undergo drastic changes in macromolecular dimensions in different environments. In solution, brush heights increase linearly as a function of Nbb, consistent with fully stretched chains, which is confirmed using cryogenic transmission electron microscopy (Cryo-TEM). Meanwhile, brush heights are consistently at a minimum in the melt, indicative of chains collapsed on the particle surface. The conformational extremes for grafted bottlebrush polymers are unseen in any linear polymer chain systems, highlighting the effect of macromolecular architecture and surface grafting. Bottlebrush grafted particles are an exciting class of materials where diversifying polymer architectures will expand PGP material design rules that harness macromolecular architecture to dictate properties.
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Characterization of Surface Patterning on Polymer-Grafted Nanocubes Using Atomic Force Microscopy and Force Volume Mapping
Atomic force microscopy (AFM), in particular force spectroscopy, is a powerful tool for understanding the supramolecular structures associated with polymers grafted to surfaces, especially in regimes of low polymer density where different morphological structures are expected. In this study, we utilize force volume mapping to characterize the nanoscale surfaces of Ag nanocubes (AgNCs) grafted with a monolayer of polyethylene glycol (PEG) chains. Spatially resolved force−distance curves taken for a single AgNC were used to map surface properties, such as adhesion energy and deformation. We confirm the presence of surface octopus micelles that are localized on the corners of the AgNC, using force curves to resolve structural differences between the micelle “bodies” and “legs”. Furthermore, we observe unique features of this system including a polymer corona stemming from AgNC−substrate interactions and polymer bridging stemming from particle−particle interactions.
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- Award ID(s):
- 2011924
- PAR ID:
- 10589198
- Publisher / Repository:
- ACS
- Date Published:
- Journal Name:
- Langmuir
- Volume:
- 40
- Issue:
- 39
- ISSN:
- 0743-7463
- Page Range / eLocation ID:
- 20464 to 20473
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1021/acs.langmuir.4c01902
