Probing the influence of composition and cross-linking degree on single-chain nanoparticles from poly(tetrahydrofuran-ran-epichlorohydrin) copolymers: Insights from neutron scattering, calorimetry, and dielectric spectroscopy.

The industrial sector has made significant strides in the development of multicomponent and multiphasic polymer materials, including polymer blends, composites (such as nanocomposites), and various copolymers. Random copolymers, characterized by their statistical arrangement of repeating units, are particularly noteworthy due to their tunability from amorphous to semicrystalline states. In this study, we focus on poly(tetrahydrofuran-ran-epichlorohydrin) (P(THF-ran-ECH)) copolymers, which serve as precursors for single-chain nanoparticles (SCNPs).

Why Single-Chain Nanoparticles from Weak Polyelectrolytes Can Be Synthesized at Large Scale in Concentrated Solution?

Here, the unresolved question of why single-chain nanoparticles (SCNPs) prepared from a weak polyelectrolyte (PE) precursor can be synthesized on a large scale in a concentrated solution is addressed, unlike SCNPs obtained from an equivalent neutral (nonamphiphilic) polymer precursor. The combination of the standard elastic single-chain nanoparticles (ESN) model -developed for neutral chains- with the classical scaling theory of PE solutions provides the key. Essentially, the long-range repulsion between electrostatic blobs in a weak PE precursor restricts the cross-linking process during SCNPs formation to the interior of each blob.

Amphiphilic Single-Chain Polymer Nanoparticles as Imaging and Far-Red Photokilling Agents for Photodynamic Therapy in Zebrafish Embryo Xenografts.

This work introduces rationally designed, improved amphiphilic single-chain polymer nanoparticles (SCNPs) for imaging and photodynamic therapy (PDT) in zebrafish embryo xenografts. SCNPs are ultrasmall polymeric nanoparticles with sizes similar to proteins, making them ideal for biomedical applications. Amphiphilic SCNPs result from the self-assembly in water of isolated synthetic polymeric chains through intrachain hydrophobic interactions, mimicking natural biomacromolecules and, specially, proteins (in size and when loaded with drugs, metal ions or fluorophores also in function).

Dynamics of Single-Chain Nanoparticles under Crowding: A Neutron Spin Echo Study.

We present a neutron spin echo (NSE) investigation to examine the impact of macromolecular crowding on the dynamics of single-chain nanoparticles (SCNPs), serving as synthetic models for biomacromolecules with flexibility and internal degrees of freedom, such as intrinsically disordered proteins (IDPs). In particular, we studied the dynamics of a medium-size poly(methyl methacrylate) (PMMA)-based SCNP (33 kDa) in solutions with low- (10 kDa) and high- (100 kDa) molecular weight analogous deuterated PMMA linear crowders. The dynamic structure factors of the SCNPs in dilute solution show certain degrees of freedom, yet the analysis in terms of the Zimm model reveals high internal friction that effectively stiffens the chain-a phenomenon also observed for IDPs.

Consecutive one-pot alkyne semihydrogenation/alkene dioxygenation reactions by Pt(II)/Cu(II) single-chain nanoparticles in green solvent.

Heterobimetallic Pt(II)/Cu(II) single-chain polymer nanoparticles (SCNPs) were sequentially synthesized from a polymeric precursor featuring both α-diazo-β-ketoester and naked β-ketoester functional groups. Photoactivated carbene generation at = 365 nm from α-diazo-β-ketoester moieities was triggered for bonding Pt(II) ions from dichloro(1,5-cyclooctadiene)Pt(II) to the polymeric precursor, whereas Cu(II) ions were subsequently incorporated Cu(II)-(β-ketoester) complex formation using Cu(II) acetate. Both intrachain Pt(II) bonding and Cu(II) complexation were found to contribute to the folding of the polymeric precursor generating Pt(II)/Cu(II)-SCNPs as evidenced by infrared spectroscopy, size exclusion chromatography and dynamic light scattering.

Artificial Photosynthases: Single-Chain Nanoparticles with Manifold Visible-Light Photocatalytic Activity for Challenging "in Water" Organic Reactions.

Photocatalyzed reactions of organic substances in aqueous media are challenging transformations, often because of scarce solubility of substrates and catalyst deactivation. Herein, we report single-chain nanoparticles, SCNPs, capable of efficiently catalyzing four different "in water" organic reactions by employing visible light as the only external energy source. Specifically, we decorated a high-molecular-weight copolymer, poly(OEGMA--AEMA), with iridium(III) cyclometalated complex pendants at varying content amounts.

Trimethylsilanol Cleaves Stable Azaylides As Revealed by Unfolding of Robust "Staudinger" Single-Chain Nanoparticles.

Herein, we disclose a unique and selective reagent for the cleavage of stable azaylides prepared by the nonhydrolysis Staudinger reaction, enabling the on-demand unfolding of robust single-chain nanoparticles (SCNPs). SCNPs with promising use in catalysis, nanomedicine, and sensing are obtained through intrachain folding of discrete synthetic polymer chains. The unfolding of SCNPs involving reversible interactions triggered by a variety of external stimuli (e.

Lanthanide-Based Single-Chain Nanoparticles as "Visual" Pass/Fail Sensors of Maximum Permissible Concentration of Cu Ions in Drinking Water.

The maximum permissible concentration (m.p.c.

Gold Nanoclusters Synthesized within Single-Chain Nanoparticles as Catalytic Nanoreactors in Water.

Metalloenzymes are able to catalyze complex biochemical reactions in cellular (aqueous) media with high efficiency. In recent years, a variety of metal-containing single-chain nanoparticles (SCNPs) have been synthesized as simplified metalloenzyme-mimetic nano-objects. However, most of the metal-containing SCNPs reported so far contained complexed metal ions but not metal nanoclusters (NCs) with diameter <5 nm, which could be used as powerful, emerging catalysts.

Structure of Single-Chain Nanoparticles under Crowding Conditions: A Random Phase Approximation Approach.

The conformation of poly(methyl methacrylate) (PMMA)-based single-chain nanoparticles (SCNPs) and their corresponding linear precursors in the presence of deuterated linear PMMA in deuterated dimethylformamide (DMF) solutions has been studied by small-angle neutron scattering (SANS). The SANS profiles were analyzed in terms of a three-component random phase approximation (RPA) model. The RPA approach described well the scattering profiles in dilute and crowded solutions.

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.

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.

Neat Protein Single-Chain Nanoparticles from Partially Denatured BSA.

The main challenge for the preparation of protein single-chain nanoparticles (SCNPs) is the natural complexity of these macromolecules. Herein, we report the suitable conditions to produce "neat" bovine serum albumin (BSA) single-chain nanoparticles (SCNPs) from partially denatured BSA, which involves denaturation in urea and intramolecular cross-linking below the overlap concentration. We use two disuccinimide ester linkers containing three and six methylene spacer groups: disuccinimidyl glutarate (DSG) and disuccinimidyl suberate (DSS), respectively.

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 (α) and a faster (β), both dominated by the MMA dynamics, and an even faster secondary relaxation (γ) reflecting the AEMA dynamics. Already for low cross-linking densities, the γ process is very much affected and eventually disappears, increasing the cross-linking density.

A method to estimate the size of single-chain nanoparticles under severe crowding conditions.

Single-chain nanoparticles (SCNPs) result from the folding of isolated polymer chains intramolecular interactions. Currently, there is no theory able to rationalize the astonishing conformational behaviour of SCNPs under severe crowding conditions (, highly concentrated solutions, all-polymer nanocomposites) and, specifically, the significant size reduction observed in highly crowded solutions of covalent-bonded SCNPs and all-polymer nanocomposites containing SCNPs. Herein, we propose a valuable method to estimate the size of SCNPs under crowding.

Disentangling Component Dynamics in an All-Polymer Nanocomposite Based on Single-Chain Nanoparticles by Quasielastic Neutron Scattering.

We have investigated an all-polymer nanocomposite (NC) consisting of single-chain nanoparticles (SCNPs) immersed in a matrix of linear chains of their precursors (25/75% composition in weight). The SCNPs were previously synthesized via "click" chemistry, which induces intramolecular cross-links in the individual macromolecules accompanied by a slight shift (5-8 K) of the glass transition temperature toward higher values and a broadening of the dynamic response with respect to the raw precursor material. The selective investigation of the dynamics of the NC components has been possible by using properly isotopically labeled materials and applying quasielastic neutron scattering techniques.

Dynamic Processes and Mechanisms Involved in Relaxations of Single-Chain Nano-Particle Melts.

We present a combined study by quasielastic neutron scattering (QENS), dielectric and mechanical spectroscopy, calorimetry and wide-angle X-ray diffraction on single-chain nano-particles (SCNPs), using the corresponding linear precursor chains as reference, to elucidate the impact of internal bonds involving bulky cross-links on the properties of polymer melts. Internal cross-links do not appreciably alter local properties and fast dynamics. This is the case of the average inter-molecular distances, the β-relaxation and the extent of the atomic displacements at timescales faster than some picoseconds.

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.

Collective Motions and Mechanical Response of a Bulk of Single-Chain Nano-Particles Synthesized by Click-Chemistry.

We investigate the effect of intra-molecular cross-links on the properties of polymer bulks. To do this, we apply a combination of thermal, rheological, diffraction, and neutron spin echo experiments covering the inter-molecular as well as the intermediate length scales to melts of single-chain nano-particles (SCNPs) obtained through 'click' chemistry. The comparison with the results obtained in a bulk of the corresponding linear precursor chains (prior to intra-molecular reaction) and in a bulk of SCNPs obtained through azide photodecomposition process shows that internal cross-links do not influence the average inter-molecular distances in the melt, but have a profound impact at intermediate length scales.

Triggering Forces at the Nanoscale: Technologies for Single-Chain Mechanical Activation and Manipulation.

Over the past decades, polymer mechanochemistry has focused on the development and application of advanced force application methods to better understand the mechanochemical response of mechanophores. In this regard, techniques such as ultrasonication and single-molecule force spectroscopy (SMFS) are used to activate and detect up to thousands of chemical events within a polymer single chain, allowing the researchers to probe the mechanochemical reactivity of these stress-responsive motifs. Here, the most recent contributions of the single-molecule force spectroscopy technique to this field are presented, putting emphasis on the fundamental parameters of the technique for triggering specific force responses and on the description of force-extension curves measured for single- and multi-mechanophore polymers.

Self-Reporting of Folding and Aggregation by Orthogonal Hantzsch Luminophores Within a Single Polymer Chain.

Self-reporting fluorescence methods for monitoring folding and aggregation of proteins have a long history in biochemistry. Placing orthogonal luminophores within individual synthetic polymer chains for self-reporting both folding (i.e.

Water dynamics and self-assembly of single-chain nanoparticles in concentrated solutions.

Single-chain polymer nanoparticles (SCNPs) are soft nano-objects consisting of uni-macromolecular chains collapsed to a certain degree by intramolecular crosslinking. The similarities between the behaviour of SCNPs and that of intrinsically disordered proteins suggest that SCNPs in concentrated solutions can be used as models to design artificial micro-environments, which mimic many of the general aspects of cellular environments. In this work, the self-assembly into SCNPs of an amphiphilic random copolymer, composed by oligo(ethylene glycol)methyl ether methacrylate (OEGMA) and 2-acetoacetoxy ethyl methacrylate (AEMA), has been investigated by means of the dielectric relaxation of water.

Steering alkyne homocoupling with on-surface synthesized metal-organic complexes.

We report a multi-step on-surface synthesis strategy. The first step consists in the surface-supported synthesis of metal-organic complexes, which are subsequently used to steer on-surface alkyne coupling reactions. In addition, we analyze and compare the electronic properties of the different coupling motifs obtained.

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.

Local Domain Size in Single-Chain Polymer Nanoparticles.

Single-chain polymer nanoparticles (SCNPs) obtained through chain collapse via intramolecular cross-linking are attracting significant interest for nanomedicine and biomimetic catalysis applications, among other fields. This interest arises from the possibility to bind active species (e.g.