The conformational studies of polymers confined at the nanoscale remain challenging and controversial due to the limitations of characterization techniques. In this study, we utilized the high sensitivity of time-resolved fluorescence resonance energy transfer (FRET) and a site-specific dye-labeling strategy to characterize the conformation of polymer chains confined in anodic aluminum oxide (AAO) nanopores. This strategy introduced a fluorescent donor (carbazole) and acceptor (anthracene) at the center of poly(butyl methacrylate) (PBMA) chains grown by atom transfer radical polymerization (ATRP). By quantitatively analyzing fluorescence decay through the Förster mechanism and the Drake-Klafter-Levitz (DKL) formalism, we can determine both the energy transfer efficiency and the spatial distribution of the dyes. This analysis revealed that the PBMA chains, with a molecular weight of 40 kDa, maintained their bulk-like conformation even when confined within nanopores as small as 10 nm in diameter. This study is the first to demonstrate the use of FRET for investigating chain conformation in confined polymer systems, which can be generalized to other polymer types and polymer topologies in different confined geometries.

Because 3D batteries comprise solid polymer electrolytes (SPEs) confined to porous scaffolds with high surface areas, the interplay between polymer confinement and interfacial interactions on SPE total ionic conductivity must be understood. This paper investigates contributions to the structure-conductivity relationship in poly(ethylene oxide) (PEO)-lithium bis(trifluorosulfonylimide) (LiTFSI) complexes confined to microporous nickel scaffolds. For bulk and confined conditions, PEO crystallinity decreases as the salt concentration (Li:EO () = 0.0125, 0.0167, 0.025, 0.05) increases. For pure PEO and all values except 0.05, PEO crystallinity under confinement is lower than in the bulk, whereas the glass transition temperature remains statistically invariant. At 298 K (semicrystalline), total ionic conductivity under confinement is higher than in the bulk at = 0.0167 but remains invariant at = 0.05; however, at 350 K (amorphous), total ionic conductivity in confinement is lower than in the bulk for both salt concentrations. Time-of-flight secondary ion mass spectrometry indicates selective migration of ions toward the polymer-scaffold interface. In summary, for the 3D structure studied, polymer crystallinity, interfacial segregation, and tortuosity play important roles in determining total ionic conductivity and, ultimately, the emergence of 3D SPEs as energy storage materials.

The synthesis and application of multifunctional diazirine-containing polymers for on-demand cross-linking of unfunctionalized commodity polymers through C-H bond insertion is demonstrated. While small-molecule diazirine cross-linkers have seen important applications such as plastic compatibilization and photopatterning, the high degree of functionalization of polymer-based diazirine cross-linkers offers promise for enhanced compatibility based on polymer blending and increased efficiency due to controllable multivalency. As a demonstrative example, unfunctionalized linear poly(-butyl acrylate) (PBA) can be cross-linked using various polymeric cross-linkers with diazirine contents as low as 0.8 wt % in 1 min under photochemical conditions. With gel fractions up to 95%, tunable rheological behavior is observed with increasing cross-linker loadings, consistent with a transition from entangled branched polymers to a cross-linked network. Moreover, the synthetic stability of the diazirine units can be exploited to prepare diazirine-containing polymers based on a variety of different backbones, from vinyl copolymers to poly(dimethylsiloxane) (PDMS), which allows successful photopatterning using a commercial 3D printer.

Parallel, homotetrameric coiled coils were computationally designed using 29 amino acid peptides. These parallel coiled coils, called "bundlemers", have symmetry, with all N-termini displayed from one end of the nanoparticle and all C-termini from the opposite end. This anisotropic display of the peptide termini allowed for the functionalization of two sets of nanoparticles with either maleimide or thiol functionality at the N-terminal region of the constituent peptides. The thiol-Michael conjugation reaction between the N-terminal end of complementary bundlemer nanoparticles formed monodisperse, rigid bundlemer dimer, called "dibundlemer", rods. The constituent, individual bundlemer nanoparticles were characterized with small-angle X-ray scattering (SAXS), Förster resonance energy transfer (FRET), and circular dichroism (CD) spectroscopy to confirm the parallel assembly of the coiled coils, consistent with the computational design. The dibundlemer rods were characterized with SAXS to reveal the uniform dibundlemer nature of the rods. Optical birefringence is observed in concentrated samples of the rods, with polarized optical microscopy (POM) revealing a nematic liquid crystalline behavior.

Incorporating dynamic covalent linkages into thermosets can endow previously unrecyclable materials with new functionality and reprocessing options. Recent work has shown that the properties of the resulting covalent adaptable networks (CANs) are highly dependent on network topology, specifically the phenomenon of percolation, when permanent linkages form a connected skeleton that spans the material. Here, we use a model glassy disulfide based CAN to assess the merits of mean-field percolation theory as a tool to describe the network topology of CANs. After challenging the theory with both experimental data and a coarse-grained molecular dynamics simulation, we find that the mean-field approach is surprisingly accurate, despite its simplifying assumptions. The theory is particularly well suited to the unique context of mixed-composition CANs and provides practical guidance on how to design for reprocessability.

In the field of polymer mechanochemistry, the activation of mechanophores within linear polymers in the bulk state is often limited by low activation rates. Herein, we demonstrate that the crystallization of polymers can significantly enhance the activation of mechanophores. Employing rhodamine-containing poly(lactic acid) (PLA) and polycaprolactone (PCL) as representative examples, our study reveals that the micromechanical force generated by crystallization is more effective in activating mechanophores than the macroscopic mechanical force induced by compression and ultrasonication, which is particularly pronounced for polymers with low molecular weights. Furthermore, the activation of the mechanophore is found to be positively correlated with the degree of crystallinity and polymer molecular weight, whereas the chirality of polymers does not influence the activation. This study offers new insights into mechanochemical reactions induced by polymer crystallization and provides a novel approach to enhancing mechanochemical reactivity.

Thiol-functionalized polymers have become a crucial class of materials due to their distinct chemical properties and versatile reactivity, leading to a broad spectrum of applications. Herein, we report the straightforward syntheses of a wide range of thiol-end-functionalized ring-opening metathesis polymerization (ROMP) polymers exploiting our previously reported catalytic ROMP mechanisms using suitable chain transfer agents. All the synthesized polymers were characterized via SEC, H NMR spectroscopy and MALDI-ToF mass spectrometry techniques. Furthermore, the existence of thiol groups on the polymer chains was verified through the well-established thiol coating reaction on gold nanoparticle surfaces. We believe this method of synthesizing thiol-end-functionalized ROMP polymers (using a reduced amount of ruthenium metal compared to conventional living ROMP) will be of great importance to materials science and biochemical research.

Organometallic oxidative addition complexes (OACs) have recently emerged as a powerful class of reagents for the rapid and chemoselective modification of biomolecules. Notably, the steric and electronic properties of the ligand and aryl group can be modified to tune the kinetic profile of the reaction and permit regioselective -arylation. Using the recently developed dicyclohexylphosphine-based bidentate ,-ligated Au(III) OACs, we computationally and experimentally examined the effects of sterically bulky and electron deficient aryl substrates to achieve selective -arylation. With this mechanistic insight, aryl substrates based on 4-iodoanisole and 3,5-dimethyl-4-iodoanisole were incorporated as end groups to generate a heterotelechelic bis-Au(III) poly(ethylene glycol) (PEG). This reagent performed rapid and regioselective -arylation with a model biomolecule, designed ankyrin repeat protein (DARPin), to form a protein-polymer OAC . This OAC mediated a second -arylation with biologically relevant thiolated small molecules (metal chelator, saccharide, and fluorophore) and macromolecules (polymer and therapeutic peptide). It is envisioned that this approach could be utilized for the rapid construction of biomacromolecular heteroconjugates with -aryl linkages.

Fluoropolymers of well-defined structures exhibit significant potential in a broad range of high-tech applications. However, the controlled synthesis of fluoropolymers from easily available monomers remains difficult. In this work, we report the development of an organocatalyzed controlled radical copolymerization of (perfluoroalkyl)ethylenes (PFAEs) and unconjugated vinyl monomers (UCMs) under light irradiation, which has enabled on-demand access toward side-chain fluorinated polymers under metal-free conditions. This method furnishes a large variety of polymers with diverse fluoroalkyl and ester/amide as pendent groups, tunable molar masses, and low dispersities (ca. = 1.1-1.3), and adjustable fractions of PFAE and UCM units. Obtained fluoropolymers exhibit good chain-end fidelity and activity, allowing chain-extension polymerizations to prepare block copolymers of complicated compositions. Furthermore, the PFAE copolymers exhibit outstanding light transmission and low refractive index.

Total internal reflection (TIR)-based structural coloration is a brilliant strategy to overcome the need for periodic nanostructures and complex fabrication processes. Light entering the microdome structure undergoes TIR, and owing to varying reflection paths, it exhibits a color that changes with the microdome size. Although solution-based printing techniques have been proposed to achieve this effect, they fall short of full-color realization owing to resolution limitations. Herein, we achieved 3628 dpi of full-color and high-resolution structural color images by printing transparent microdome structures with 1.2-9.9 μm diameter using electrohydrodynamic (EHD) jet printing. Additionally, high-resolution EHD jet-printed structural color images display complex encoded information, enhancing the anticounterfeiting effectiveness through their fabrication simplicity and precise control over the microdome size. Because of these advantages, this TIR-based structural coloration technique with EHD jet printing is highly suitable for anticounterfeiting applications.

The performances and properties of random copolyesters, including biodegradability, mechanical and thermal properties, transparency, etc., are highly influenced by their chain structures. However, obtaining detailed chain sequence information remains a significant challenge. This study introduces a mathematical model based on a probabilistic approach to determine the sequence length and distribution in random copolyesters. Two types of copolyesters, AABB-AABB, representing poly(butylene adipate--terephthalate) (PBAT), and AABB-AB, using poly(butylene succinate--glycolic acid) (PBT-PGA) as an example, are the focus. The predicted sequence lengths of various copolyesters derived from the model are in good agreement with the values reported in the literature. The chain sequence distribution obtained from the model provides better insights into the unique properties of the copolyesters. It is observed that the incorporation of hydroxyl acid units into copolyester chains effectively reduces the sequence length without altering the copolymer composition, offering a strategic approach for enhancing degradation performance while maintaining mechanical properties of random copolyesters. The influence of the number-average sequence length becomes particularly significant when the copolymer composition ranges between 0.7 and 0.9, with a higher copolymer composition required for copolyesters containing hydroxyl acid monomer units. This model represents a powerful tool for researchers, enabling a deeper understanding of the relationship between copolymer composition and its structural characteristics in random copolyesters and facilitating the development of high-performance random copolyesters.

Cross-linked polyethylenes (PEs) are widely employed, but the permanent links between the chains impede recycling. We show that via imine formation with diamines keto-functionalized polyethylenes from both free-radical (keto-low-density PE, keto-LDPE) and catalytic (keto-high-density PE, keto-HDPE) nonalternating ethylene-CO copolymerization can be cross-linked efficiently in the melt, resulting in gel fractions of the formed cross-linked PEs of up to 85% and improved tensile properties. The imine-based cross-links in the material can be hydrolyzed at 140 °C to recycle up to 97% of the initial thermoplastic keto-polyethylene. Low keto contents of ≤1.5 mol % are found ideal to retain PE-like thermal properties, achieve sufficient cross-link density, and maintain circular recyclability.

Polyacrylonitrile (PAN) is a key industrial polymer for the production of carbon fiber for high-strength, lightweight composite material applications, with an estimated 90% of the carbon fiber market relying on PAN-based polymers. Traditionally, PAN synthesis is achieved by conventional radical polymerization, resulting in broad molecular weight distributions and the use of toxic organic solvents or surfactants during the synthesis. Additionally, attempts to improve polymer and processing properties by controlled radical polymerization methods suffer from low monomer conversions and struggle to achieve molecular weights suitable for producing high-performance carbon fiber. In this study, we present an aqueous photoiniferter (aqPI) polymerization of acrylonitrile, achieving high monomer conversion and high PAN molecular weights with significantly faster kinetics and dispersity control when compared to traditional methods. This approach allows for the unprecedented control of polymer properties that are integral for downstream processing for enhanced carbon fiber production.

We investigate the combined effects of ionizable monomer fraction , pH, and monovalent salt concentration on the swelling of weak polyelectrolyte brushes (PEBs) by using in situ ellipsometry. Our system consists of random copolymers of basic (2-(dimethylamino)ethyl acrylate, DMAEA) and neutral (2-hydroxyethyl acrylate, HEA) monomers at varying fractions of ionizable monomer. Swelling of the brushes qualitatively follows the trends predicted by scaling laws for PEBs under different charge states but quantitatively deviates at specific ionic strengths and pH values. We posit these deviations stem from the lack of excluded volume effects and assumptions of strong chain stretching in current theoretical models. Most notably, we uncover a salt-dependent, nonmonotonic hysteretic behavior as weak PEB brushes are cycled from protonated to deprotonated and back. The nonmonotonic trend of hysteresis with salt can be explained by an interplay between the protonation facilitating effects of salt in the osmotic regime and the charge screening effects in the salted regime, which make charge distribution along weak PEBs more uniform. Our results provide insight into the mechanisms that determine whether polyelectrolytes exhibit weak versus strong polyelectrolyte behavior in various environmental conditions.

Generating teeth requires mimicking tooth developmental processes. Biomaterials are essential to support 3D tooth organoid formation, but their properties must be finely tuned to achieve the required biomimicry for tooth development. For the first time, we used bioorthogonally cross-linked hydrogels as defined 3D matrixes for tooth developmental engineering, and we highlighted how their properties play a pivotal role in enabling 3D tooth organoid formation . We prepared hydrogels by mixing gelatin precursors modified either with tetrazine (Tz) or norbornene (Nb) moieties. We tuned the hydrogel properties ( = 2-7 kPa; ' = 500-1500 Pa) by varying the gelatin concentration (8% vs 12% w/V) and stoichiometric ratio (Tz:Nb = 1 vs 0.5). We encapsulated dental epithelial-mesenchymal cell pellets in a library of hydrogels and identified a hydrogel formulation that enabled successful growth kinetics and morphogenesis of tooth germs, introducing a defined tunable platform for tooth organoid engineering and modeling.

Poly(arylene ether)s (PAEs) are a versatile class of thermoplastic materials with commercial importance. Currently their synthesis relies predominantly on either nucleophilic or electrophilic aromatic substitution reactions, severely limiting the scope of available PAEs. Herein, we report the copper(II)-catalyzed polycondensation of electronically unactivated aryl bromides with bisphenols to afford a wide range of new PAEs. These PAEs are characterized by their thermal and mechanical properties. Functional PAEs were produced that have reversible acid- and redox-triggered chromophores incorporated into the backbone, which illustrates the utility of these methods.

Self-consistent field theory (SCFT), the mean-field theory of polymer thermodynamics, is a powerful tool for understanding ordered state selection in block copolymer melts and blends. However, the nonlinear governing equations pose a significant challenge when SCFT is used for phase discovery because converging an SCFT solution typically requires an initial guess close to the self-consistent solution. This Viewpoint provides a concise overview of recent efforts where machine learning methods (particle swarm optimization, Bayesian optimization, and generative adversarial networks) have been used to make the first strides toward converting SCFT from a primarily explanatory tool into one that can be readily deployed for phase discovery.

Cellulose-based functional materials play a crucial role in sustainable social development. However, during the material synthesis process, there is typically significant reliance on various solvent systems for macroscopic- or molecular-scale functionalization modifications. In this study, an innovative hydrophobic eutectic solvent (HES) was developed using ethyl cellulose (EC) and thymol (Thy) without any external solvents. Utilizing this homogeneous system, it is convenient to chemically modify the components without any catalyst. Furthermore, a hydrophobic cellulosic cross-linked network (HCCN) can be successfully prepared through in situ photopolymerization. The HCCN film exhibits high transparency, excellent mechanical properties, chemical stability, and durability. The EC/Thy prepolymer system also demonstrates favorable processability for the preparation of various polymeric materials. Additionally, the applicability of other biomasses and derivatives based on the eutectic strategy has been verified. The methodology proposed in this study offers novel insights into the green and solvent-free preparation of biomass functional materials.

Pickering emulsion polymerization is a practical method to fabricate functional composite materials. However, most reported systems proceed homogeneously within the stabilized monomer phase and create nondegradable chemical bonds. Here, interfacial Pickering emulsion polycondensation between aromatic aldehydes and polymercaptans is developed using sustainable cellulose nanoparticles as the stabilizer. When sulfonated cellulose nanocrystals (S-CNCs) were utilized, they also catalyzed the polycondensation to produce the oxidatively degradable S,S-acetal groups on the polymer chains. The influence of monomer and cellulose structures on the polymerization behavior and composite properties were compared.

The density evolution of polystyrene (PS) adsorbed layers on phenyl-modified SiO-Si substrates was investigated. The thickness and density of flattened layer on substrates with above 75% phenyl content increased over annealing time and could approach 4.7 nm and 1.37 g/cm at equilibrium, respectively, which were much higher than those on SiO-Si. The annealing time for flattened chains to reach equilibrium increased with an increasing phenyl content on the substrate. The interface sensitive sum frequency generation vibrational spectroscopy (SFG) technique revealed that both the amount and the strength of the interfacial π-π interaction between the phenyl groups of substrates and in PS chains increased with annealing time. This resulted in more stretched chains perpendicularly, leading to a denser and thicker adsorbed layer with a closest-packing structure, driven by favorable enthalpy processes. Our work provides important insight into the densification mechanism of adsorbed flattened layers.

Complex coacervation is an associative phase separation process of oppositely charged polyelectrolyte solutions, resulting in a coacervate phase enriched with charged polymers and a polymer-lean phase. To date, studies on the phase behavior of complex coacervation have been largely restricted to aqueous systems with relatively high dielectric constants due to the limited solubility of most polyelectrolytes, hindering the exploration of the effects of electrostatic interactions from differences in solvent permittivity. Herein, we prepare two symmetric but oppositely charged polymerized ionic liquids (PILs), consisting of poly[1-[2-acryloyloxyethyl]-3-butylimidazolium bis(trifluoromethane)sulfonimide] (PAT) and poly[1-ethyl-3-methylimidazolium 3-[[[(trifluoromethyl)sulfonyl]amino]sulfonyl]propyl acrylate] (PEA). Due to the delocalized ionic charges and their chemical structure similarity, both PAT and PEA are soluble in various organic solvents with a wide range of dielectric constants, ranging from 16.7 (hexafluoro-2-propanol (HFIP)) to 66.1 (propylene carbonate (PC)). Notably, no significant correlation is observed between the solvent dielectric constant and the phase diagram of the complex coacervation of PILs. Most organic solvents lead to similar phase diagrams and salt resistances regardless of their dielectric constants, except two protic solvents (HFIP and 2,2,2-trifluoroethanol (TFE)) showing significantly low salt resistances compared to the others. The low salt resistance in these protic solvents primarily arises from strong hydrogen bonding between PILs and solvents as evidenced by H NMR and small-angle neutron scattering (SANS) experiments. Our finding suggests that for the coacervation of PILs, particularly those with delocalized and weak charge interactions, entropy from the counterion release and polymer-solvent interaction χ parameter play a more important role than the electrostatic interactions of charged molecules, rendered by the dielectric constant of the solvent medium.