When does a macromolecule transition from a polymer chain to a nanoparticle?

Journal Article · Tue Nov 22 00:00:00 EST 2022 · Nanoscale Advances

DOI:https://doi.org/10.1039/D2NA00617K· OSTI ID:1897238

Fischer, Jacob ^[1]; Han, Lu ^[2]; Saito, Tomonori  ^[2]; Dadmun, Mark  ^[3]

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1. Department of Chemistry, University of Tennessee, Knoxville, Tennessee, USA
2. Chemical Sciences Division, Oak Ridge National Lab, Oak Ridge, Tennessee, USA
3. Department of Chemistry, University of Tennessee, Knoxville, Tennessee, USA, Chemical Sciences Division, Oak Ridge National Lab, Oak Ridge, Tennessee, USA

Frequently, the defining characteristic of a nanoparticle is simply its size, where objects that are 1–100 nm are characterized as nanoparticles. However, synthetic and biological macromolecules, in particular high molecular weight chains, can satisfy this size requirement without providing the same phenomena as one would expect from a nanoparticle. At the same time, soft polymer nanoparticles are important in a broad range of fields, including understanding protein folding, drug delivery, vitrimers, catalysis and nanomedicine. Moreover, the recent flourish of all polymer nanocomposites has led to the synthesis of soft all-polymer nanoparticles, which emerge from internal crosslinking of a macromolecule. Thus, there exists a transition of an internally crosslinked macromolecule from a polymer chain to a nanoparticle as the amount of internal crosslinks increases, where the polymer chain exhibits different behavior than the nanoparticle. Yet, this transition is not well understood. In this work, we seek to address this knowledge gap and determine the transition of a macromolecule from a polymer chain to a nanoparticle as internal crosslinking increases. In this work, small angle neutron scattering (SANS) offers insight into the structure of polystyrene and poly(ethyl hexyl methacrylate) nanostructures in dilute solutions, with crosslinking densities that vary from 0.1 to 10.7%. Analyses of the SANS data provides structural characteristics to classify a nanostructure as chain-like or particle-like and identify a crosslinking dependent transition between the two morphologies. It was found that for both types of polymeric nanostructures, a crosslinking density of 0.81% (~ a crosslink for every 1 in 125 monomers) or higher exhibit clear particle-like behavior. Lower crosslinking density nanostructures showed amounts of collapse similar to that of a star polymer (0.1% XL) or a random walk polymer chain (0.4% XL). Thus, the transition of an internally crosslinked macromolecule from a polymer chain to a nanoparticle is not an abrupt transition but occurs via the gradual contraction of the chain with incorporated crosslinks.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE; USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division; National Science Foundation (NSF); European Union (EU)
• Grant/Contract Number: AC05-00OR22725; DMR-0520547; 654000
• OSTI ID: 1897238
• Alternate ID(s): OSTI ID: 1959577
• Journal Information: Nanoscale Advances, Journal Name: Nanoscale Advances Vol. 4 Journal Issue: 23; ISSN 2516-0230
• Publisher: Royal Society of Chemistry (RSC)
• Country of Publication: United Kingdom
• Language: English

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