Stars, combs and bottlebrushes of elastic single-chain nanoparticles

Hierarchical self-assembly of structural elements gives rise to superstructures often with outstanding properties when compared to individual elements, as first observed in nature. While folding of individual synthetic chains leads to discrete single-chain nanoparticles (SCNPs) of significant interest for a number of applications, its full potential utility through integration into well-defined superstructures is recently being recognized. Remarkably, SCNPs in good solvent resemble randomly branched polymers with ideal connectivity in a theta-solvent or percolating clusters with screened excluded-volume interactions. Herein we consider the integration of SCNPs into star, comb and bottlebrush topologies and investigate the dimensions of the resulting superstructures under different conditions (good solvent, ideal conformations, 1D-and 2D-confinement in nanopores and nanoslits, anchored to flat surfaces). A detailed comparison of the equilibrium conformational properties of star, comb and bottlebrush polymers composed of elastic SCNPs to those of equivalent topologies based on linear chains is provided. This analysis reveals the effect of hierarchical topology on superstructure dimensions in several relevant environments, as well as how the structural parameters of the SCNPs influence the location of the comb-to-bottlebrush transition as a function of grafting density. The degree of intra-chain cross-linking arises as an additional parameter for controlling the local and global dimensions of stars, combs and bottlebrushes of SCNPs.Financial support by MCIN/AEI/10.13039/501100011033 and “ERDF – A way of making Europe” (PID2021-123438NB-I00), Eusko Jaurlaritza –Basque Government (IT1566-22) and Gipuzkoako Foru Aldundia, Programa Red Gipuzkoana de Ciencia, Tecnología e Innovación (2021-CIEN-000010-01) is gratefully acknowledged

Advances in the Phototriggered Synthesis of Single-Chain Polymer Nanoparticles

Clean use of photons from light to activate chemical reactions offers many possibilities in different fields, from chemistry and biology to materials science and medicine. This review article describes the advances carried out in last decades toward the phototriggered synthesis of single-chain polymer nanoparticles (SCNPs) as soft nanomaterials with promising applications in enzyme-mimicking catalysis and nanomedicine, among other different uses. First, we summarize some different strategies developed to synthesize SCNPs based on photoactivated intrachain homocoupling, phototriggered intrachain heterocoupling and photogenerated collapse induced by an external cross-linker. Next, we comprehensively review the emergent topic of photoactivated multifolding applied to SCNP construction. Finally, we conclude by summarizing recent strategies towards phototriggered disassembly of SCNPsThis research was funded by Gipuzkoako Foru Aldundia -Programa Red Gipuzkoana de Ciencia, Tecnologia e Innovacion 2019-, grant number 2019-CIEN-000050-01; Basque Government, grant number IT-1175-19; and MCIU/AEI/FEDER, UE, grant number PGC2018-094548-B-I00

Homogenization of Mutually Immiscible Polymers Using Nanoscale Effects: A Theoretical Study

4 p.A theoretical study to investigate homogenization of mutually immiscible polymers using nanoscale effects has been performed. Specifically, the miscibility behavior of all-polymer nanocomposites composed of linear-polystyrene (PS) chains and individual cross-linked poly(methyl methacrylate)-nanoparticles (PMMA-NPs) has been predicted. By using a mean field theory accounting for combinatorial interaction energy and nanoparticle-driven effects, phase diagrams were constructed as a function of PMMA-NP size, PS molecular weight, and temperature. Interestingly, complete miscibility (i.e., homogeneity) was predicted from room temperature to 675 K for PMMA-nanoparticles with radius less than ~7 nm blended with PS chains (molecular weight 150 kDa, nanoparticle volume fraction 20%) in spite of the well-known immiscibility between PS and PMMA. Several nanoscale effects affecting miscibility in PMMA-NP/PS nanocomposites involving small PMMA-nanoparticles are discussed.Financial support by MEC (Grant no. CSD2006-53), Basque Government (Grupos Consolidados IT-274-07), and Diputación de Gipuzkoa through C. I. C. Nanogune—Consolider and Nanotron Project is gratefully acknowledged

Lanthanide-Based Single-Chain Nanoparticles as “Visual” Pass/Fail Sensors of Maximum Permissible Concentration of Cu2+ Ions in Drinking Water

The maximum permissible concentration (m.p.c.) of Cu2+ ions in drinking water, as set by the World Health Organization (WHO) is m.p.c. (Cu2+)WHO = 30 × 10−6 m, whereas the US Environmental Protection Agency (EPA) establishes a more restrictive value of m.p.c. (Cu2+)EPA = 20 × 10−6 m. Herein, for the first time ever, a family of m.p.c. (Cu2+) “visual” pass/fail sensors is developed based on water-soluble lanthanide-containing single-chain nanoparticles (SCNPs) exhibiting an average hydrodynamic diameter less than 10 nm. Both europium (Eu)- and terbium (Tb)-based SCNPs allow excessive Cu2+ to be readily detected in water, as indicated by the red-to-transparent and green-to-transparent changes, respectively, under UV light irradiation, occurring at 30 × 10−6 m Cu2+ in both cases. Complementary, dysprosium (Dy)-based SCNPs show a yellow color-to-transparent transition under UV light irradiation at ≈15 × 10−6 m Cu2+. Eu-, Tb-, and Dy-containing SCNPs prove to be selective for Cu2+ ions as they do not respond against other metal ions, such as Fe2+, Ag+, Co2+, Ba2+, Ni2+, Hg2+, Pb2+, Zn2+, Fe3+, Ca2+, Mn2+, Mg2+, or Cr3+. These new m.p.c. (Cu2+) “visual” pass/fail sensors are thoroughly characterized by a combination of techniques, including size exclusion chromatography, dynamic light scattering, inductively coupled plasma-mass spectrometry, as well as infrared, UV, and fluorescence spectroscopy.Ministerio de Ciencia e Innovación. Grant Numbers: TED2021-130107A-I00, PID2021-123438NB-I0

Advances in Single-Chain Nanoparticles for Catalysis Applications

Enzymes are the most efficient catalysts known for working in an aqueous environment near room temperature. The folding of individual polymer chains to functional single-chain nanoparticles (SCNPs) offers many opportunities for the development of artificial enzyme-mimic catalysts showing both high catalytic activity and specificity. In this review, we highlight recent results obtained in the use of SCNPs as bioinspired, highly-efficient nanoreactors (3–30 nm) for the synthesis of a variety of nanomaterials (inorganic nanoparticles, quantum dots, carbon nanodots), polymers, and chemical compounds, as well as nanocontainers for CO2 capture and release.Financial support by the Spanish Ministry "Ministerio de Economia y Competitividad", MAT2015-63704-P (MINECO/FEDER, UE), the Basque Government, IT-654-13, and the Gipuzkoako Foru Aldundia, Programa Red Gipuzkoana de Ciencia, Tecnologia e Innovacion 2017, is acknowledged. Jon Rubio-Cervilla is grateful to the Materials Physics Center-MPC for his predoctoral grant. Edurne Gonzalez received funding from the "Fellows Gipuzkoa" fellowship of the Gipuzkoako Foru Aldundia

Intra- vs Intermolecular Cross-Links in Poly(methyl methacrylate) Networks Containing Enamine Bonds

The molecular dynamics of a copolymer composed of methyl methacrylate (MMA) and (2-acetoacetoxy)ethyl methacrylate (AEMA) monomers and the influence on it of intra-to intermolecular cross-links of AEMA units with ethylenediamine (EDA) was studied by combining dielectric relaxation experiments and thermal investigations. The dielectric spectra of the non-cross-linked copolymer show three dynamical processes: a slow relaxation (alpha) and a faster (beta), both dominated by the MMA dynamics, and an even faster secondary relaxation (gamma) reflecting the AEMA dynamics. Already for low cross-linking densities, the gamma process is very much affected and eventually disappears, increasing the cross-linking density. The secondary beta relaxation however was nearly unaffected by cross-linking. The effect of cross-linking on the alpha relaxation was very pronounced with an important increasing of the glass transition temperature Tg. There was also an increase of the dynamic heterogeneity and the relaxation intensity when increasing the cross-linking density (up to the maximum explored, 9 mol % EDA). The quality of the average time scale and Tg value have similarities in behavior for intra-and intermolecular cross linking, but clear differences in the dynamic heterogeneities where observed. These differences can be interpreted in connection with the sparse internal structure of the collapsed single chains obtained by intramolecular cross-linking.We gratefully acknowledge Grant PGC2018-094548-B-I00 funded by MCIN/AEI/10.13039/501100011033 and by "ERDF A way of making Europe", the Grants IT-1175-19 and IT-1566-22 from Eusko Jaurlaritza (Basque Government) and the Open Access funding provided by University of Basque Country

Metamorphosis of a Commodity Plastic like PVC to Efficient Catalytic Single-Chain Nanoparticles

We perform the conversion of a commodity plastic of common use in pipes, window frames, medical devices, flexible hoses, etc. like polyvinyl chloride (PVC) to single-chain nanoparticles (SCNPs). SCNPs are versatile, protein-mimetic soft nano-objects of growing interest for catalysis, sensing, and nanomedicine, among other uses. We demonstrate that the metamorphosis process -as induced through metal-free click chemistry- leads to well-defined, uniform SCNPs that are stable during storage in the solid state for months. All the conversion process (from PVC isolation to PVC-SCNPs synthesis) can be run in a green, dipolar aprotic solvent and involving, when required, a simple mixture of ethanol and water (1/1 vol.) as non-solvent. The resulting PVC-SCNPs are investigated as recyclable, metalloenzyme-mimetic catalysts for several representative Cu(II)-catalyzed organic reactions. The method could be valid for the metamorphosis and valorization of other commodity plastics in which it is feasible to install azide functional groups in their linear polymer chains.We gratefully acknowledge Grant PID2021-123438NB-I00 funded by MCIN/AEI/10.13039/501100011033 and “ERDF A way of making Europe”, Grant TED2021-130107A-I00 funded by MCIN/AEI/10.13039/501100011033 and Unión Europea “NextGenerationEU/PRTR” and Grant IT-1566-22 from Eusko Jaurlaritza (Basque Government)

Glass-Transition Dynamics of Mixtures of Linear Poly(Vinyl Methyl Ether) with Single-Chain Polymer Nanoparticles: Evidence of a New Type of Nanocomposite Materials

Single-chain polymer nanoparticles (SCNPs) obtained through chain collapse by intramolecular cross-linking are attracting increasing interest as components of all-polymer nanocomposites, among other applications. We present a dielectric relaxation study on the dynamics of mixtures of poly(vinyl methyl ether) (PVME) and polystyrene (PS)-based SCNPs with various compositions. Analogous dielectric measurements on a miscible blend of PVME with the linear precursor chains of the SCNPs are taken as reference for this study. Both systems present completely different behaviors: While the blend with the linear precursor presents dynamics very similar to that reported for PVME/PS miscible blends, in the PVME/SCNP mixtures there are an appreciable amount of PVME segments that are barely affected by the presence of SCNPs, which nearly vanishes only for mixtures with high SCNP content. Interestingly, in the frame of a simple two-phase system, our findings point towards the existence of a SCNP-rich phase with a constant PVME fraction, regardless of the overall concentration of the mixture. Moreover, the dynamics of the PVME segments in this SCNP-rich phase display an extreme dynamic heterogeneity, a signature of constraint effects.This research was funded by Eusko Jaurlaritza project code: IT-654-13 and the Ministerio de Economia y Competitividad project code: MAT2015-63704-P (MINECO/FEDER, UE)

Advances in the Multi-Orthogonal Folding of Single Polymer Chains into Single-Chain Nanoparticles

The folding of certain proteins (e.g., enzymes) into perfectly defined 3D conformations via multi-orthogonal interactions is critical to their function. Concerning synthetic polymers chains, the “folding” of individual polymer chains at high dilution via intra-chain interactions leads to so-called single-chain nanoparticles (SCNPs). This review article describes the advances carried out in recent years in the folding of single polymer chains into discrete SCNPs via multi-orthogonal interactions using different reactive chemical species where intra-chain bonding only occurs between groups of the same species. First, we summarize results from computer simulations of multi-orthogonally folded SCNPs. Next, we comprehensively review multi-orthogonally folded SCNPs synthesized via either non-covalent bonds or covalent interactions. Finally, we conclude by summarizing recent research about multi-orthogonally folded SCNPs prepared through both reversible (dynamic) and permanent bonds.This research was funded by Gipuzkoako Foru Aldundia -Programa Red Gipuzkoana de Ciencia, Tecnología e Innovación 2019-, grant number 2019-CIEN-000050-01; Basque Government, grant number IT-1175-19; and MCIU/AEI/FEDER, UE, grant number PGC2018-094548-B-I00

Toward Long-Term-Dispersible, Metal-Free Single-Chain Nanoparticles

We report herein on a new platform for synthesizing stable, inert, and dispersible metal-free single-chain nanoparticles (SCNPs) via intramolecular metal-traceless azide–alkyne click chemistry. It is well known that SCNPs synthesized via Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) often experience metal-induced aggregation issues during storage. Moreover, the presence of metal traces limits its use in a number of potential applications. To address these problems, we selected a bifunctional cross-linker molecule, sym-dibenzo-1,5-cyclooctadiene-3,7-diyne (DIBOD). DIBOD has two highly strained alkyne bonds that allow for the synthesis of metal-free SCNPs. We demonstrate the utility of this new approach by synthesizing metal-free polystyrene (PS)-SCNPs without significant aggregation issues during storage, as demonstrated by small-angle X-ray scattering (SAXS) experiments. Notably, this method paves the way for the synthesis of long-term-dispersible, metal-free SCNPs from potentially any polymer precursor decorated with azide functional groups.We gratefully acknowledge Grant PID2021-123438NB-I00 funded by MCIN/AEI/10.13039/501100011033; “ERDF A way of making Europe”, Grant TED2021-130107A-I00 funded by MCIN/AEI/10.13039/501100011033; Unión Europea “NextGenerationEU/PRTR” and Grant IT-1566-22 from Eusko Jaurlaritza (Basque Government)