Polymer Chains Research Articles

Phase transitions in chromatin: Mesoscopic and mean-field approaches.

By means of a minimal physical model, we investigate the interplay of two phase transitions at play in chromatin organization: (1) liquid-liquid phase separation within the fluid solvating chromatin, resulting in the formation of biocondensates; and (2) the coil-globule crossover of the chromatin fiber, which drives the condensation or extension of the chain. In our model, a species representing a domain of chromatin is embedded in a binary fluid. This fluid phase separates to form a droplet rich in a macromolecule (B). Chromatin particles are trapped in a harmonic potential to reproduce the coil and globular phases of an isolated polymer chain. We investigate the role of the droplet material B on the radius of gyration of this polymer and find that this radius varies nonmonotonically with respect to the volume fraction of B. This behavior is reminiscent of a phenomenon known as co-non-solvency: a polymer chain in a good solvent (S) may collapse when a second good solvent (here B) is added in low quantity and expands at higher B concentration. In addition, the presence of finite-size effects on the coil-globule transition results in a qualitatively different impact of the droplet material on polymers of various sizes. In the context of genetic regulation, our results suggest that the size of chromatin domains and the quantity of condensate proteins are key parameters to control whether chromatin may respond to an increase in the quantity of chromatin-binding proteins by condensing or expanding.

Highly Simplified FeCl3‐Assisted Copolymerization and Doping for Organic Thermoelectrics

ABSTRACTThe FeCl3 is a well‐known oxidizing agent for oxidative polymerization as well as a p‐type dopant for making conducting polymers, but no studies have yet explored the simultaneous use of FeCl3 for both polymerization and doping of organic soluble conjugated polymers (CPs) in organic thermoelectric (OTE) applications. In this study, soluble 4H‐cyclopenta[2,1‐b:3,4‐b′]dithiophene (CPDT)‐co‐3,4‐ethylenedioxythio‐phene (EDOT) polymers were successfully synthesized via a simple FeCl3‐assisted oxidative coupling reaction at room temperature. In addition, FeCl3 doping of the synthesized polymers enabled them to exhibit thermoelectric properties. The addition of 10% ~ 20% EDOT in a polymer chain gave a synergetic effect on the electrical conductivity and power factor (PF) in the OTE devices. In that ratio, the strong electron‐donating EDOT facilitates doping in the CPs, and the planar CPDT backbones stabilize the generated polaron/bipolaron species through efficient π‐electron delocalization, resulting in the highest electrical conductivity. At the optimal EDOT ratio of 20%, a more than 10‐fold enhancement in PFs was achieved reaching up to 0.182 ± 0.021 μW m−1 K−2. The EDOT moiety, except in PEDOT:PSS, is rarely found in conjugated copolymers, but its proper incorporation is expected to enhance thermoelectric properties of the organic soluble CPs.

Electrochemical Switching of Laser-Induced Graphene/Polymer Composites for Tunable Electronics

Laser reduction of graphene oxide (GO) is a promising approach for achieving flexible, robust, and electrically conductive graphene/polymer composites. Resulting composite materials show significant technological potential for energy storage, sensing, and bioelectronics. However, in the case of insulating polymers, the properties of electrodes show severely limited performance. To overcome these challenges, we report on a post-processing redox treatment that allows the tuning of the electrochemical properties of laser-induced rGO/polymer composite electrodes. We show that the polymer substrate plays a crucial role in the electrochemical modulation of the composites’ properties, such as the electrode impedance, charge transfer resistance, and areal capacitance. The mechanism behind the reversible control of electrochemical properties of the rGO/polymer composites is the cleavage of polymer chains in the vicinity of rGO flakes during redox cycling, which exposes rGO active sites to interact with the electrolyte. Sequential redox cycling improves composite performance, allowing the development of devices such as electrolyte-gated transistors, which are widely used in chemical sensing applications. Our strategy enables the engineering of the electrochemical properties of rGO/polymer composites by post-treatment with dynamic switching, opening up new possibilities for flexible electronics and electrochemical applications having tunable properties.

Extend Plastron Longevity on Superhydrophobic Surface Using Gas Soluble and Gas Permeable Polydimethylsiloxane (PDMS)

The gas (or plastron) trapped between micro/nano-scale surface textures, such as that on superhydrophobic surfaces, is crucial for many engineering applications, including drag reduction, heat and mass transfer enhancement, anti-biofouling, anti-icing, and self-cleaning. However, the longevity of the plastron is significantly affected by gas diffusion, a process where gas molecules slowly diffuse into the ambient liquid. In this work, we demonstrated that plastron longevity could be extended using a gas-soluble and gas-permeable polydimethylsiloxane (PDMS) surface. We performed experiments for PDMS surfaces consisting of micro-posts and micro-holes. We measured the plastron longevity in undersaturated liquids by an optical method. Our results showed that the plastron longevity increased with increasing the thickness of the PDMS surface, suggesting that gas initially dissolved between polymer chains was transferred to the liquid, delaying the wetting transition. Numerical simulations confirmed that a thicker PDMS material released more gas across the PDMS–liquid interface, resulting in a higher gas concentration near the plastron. Furthermore, we found that plastron longevity increased with increasing pressure differences across the PDMS material, indicating that the plastron was replenished by the gas injected through the PDMS. With increasing pressure, the mass flux caused by gas injection surpassed the mass flux caused by the diffusion of gas from plastron to liquid. Overall, our results provide new solutions for extending plastron longevity and will have significant impacts on engineering applications where a stable plastron is desired.

Near-Surface Concentration Profile of Sheared Semidilute Polymer Solutions.

Controlling the structure of polymer solutions near a solid surface is crucial for many industrial processes as it significantly impacts solution flow and influences slip at the interface. To date, only a few techniques have been developed to experimentally investigate this type of interface at the nanometric scale of solid/liquid interactions. In this study, we probe the interface between a smooth sapphire surface and a semidilute polystyrene solution, using neutron reflectivity. A special setup for flow measurements under shear has been designed and optimized. Our results show that, at rest, polymer chains are globally depleted from the solid surface. Contrary to common assumptions, some polystyrene chains do adsorb onto the wall. Under flow conditions, we experimentally demonstrate that the depletion layer remains stable, a finding that has been hypothesized but is only vaguely confirmed in the literature.

Passivation of Iodine Vacancies in Perovskite Photodetectors by Oxygen Functional Groups in the Main and Side Chains of Alcohol Polymers

Passivation of Iodine Vacancies in Perovskite Photodetectors by Oxygen Functional Groups in the Main and Side Chains of Alcohol Polymers

Rapid Na+ Transport Pathway and Stable Interface Design Enabling Ultralong Life Solid‐State Sodium Metal Batteries

AbstractSodium‐metal batteries (SMBs) using solid‐state polymer electrolytes (SPEs) show impressive superiority in energy density and safety. As promising candidates for SPEs, solid‐state plastic crystal electrolytes (SPCE) based on succinonitrile (SN) plastic crystal could achieve high ion conductivity and wide voltage window. Nonetheless, the notorious SN decomposition reaction on the electrode/electrolyte interface seriously challenges the stable operation of the battery. To address this drawback, we commence with the structural engineering of the polymer chain segments in SPCE and employ intermolecular interactions to optimize the composition of solid electrolyte interface (SEI). Moreover, this study emphasizes the importance of polymer network design in optimizing the migration behavior of sodium ions in SPCE. The assembled sodium symmetric cells display a high critical current density of up to 2.7 mA cm−2 and stable cycling performance for 700 hours at 0.5 mA cm−2. Furthermore, the Na/SPCE‐9/Na3V2(PO4)3 maintains a discharge specific capacity of up to 76.8 mAh g−1 at 10 C and shows impressive long‐cycle stability, retaining 86.2 % of initial capacity over 5000 cycles with an average coulombic efficiency of 99.9 %. Our work presents a high‐performance SPCE with intrinsic safety, providing valuable insights for the future design of solid‐state SMBs.

Recyclable Millable PolyureThane based on Enaminone Bonds With Upcycled Mechanical Performance.

Thermoplastic polyurethane (TPU) exhibits re-processable properties, but the properties of TPU is deteriorated during the reprocessing for the oxidation and degradation of polymer chains. Meanwhile, although thermoset polyurethane exhibits excellent mechanical properties, it cannot be recycled for permanent crosslinking. Hence, it's still a challenge to obtain PU which exhibits the balance between the recyclability and mechanical properties. In this work, a new dynamic bond obtained from the reaction between enaminone and isocyanate is used to prepare re-processable millable polyurethane, and the morphology of network can be tuned via the dissociation of the cross-linked sites of PU. Interestingly, the cross-linked network can transform into a linear polymer by adding the amine which can be used when reacted with isocyanate to generate new re-crosslinked PU. This process can be carried out in a Haake mixer without any solvents. The mechanical properties of the re-crosslinked polyurethane can be tuned via the controlling of the amine and isocyanate addition, and the maximum tensile strength increase by 178.4% after processing for four times, realizing mechanical reinforcement after recycling. This kind of recycling achieves through one-step melting method in solvent-free conditions provides a feasible way to prepare recyclable PU with good mechanical performance and customizable properties.

Rapid Na+ Transport Pathway and Stable Interface Design Enabling Ultralong Life Solid-State Sodium Metal Batteries.

Sodium-metal batteries (SMBs) using solid-state polymer electrolytes (SPEs) show impressive superiority in energy density and safety. As promising candidates for SPEs, solid-state plastic crystal electrolytes (SPCE) based on succinonitrile (SN) plastic crystal could achieve high ion conductivity and wide voltage window. Nonetheless, the notorious SN decomposition reaction on the electrode/electrolyte interface seriously challenges the stable operation of the battery. To address this drawback, we commence with the structural engineering of the polymer chain segments in SPCE and employ intermolecular interactions to optimize the composition of solid electrolyte interface (SEI). Moreover, this study emphasizes the importance of polymer network design in optimizing the migration behavior of sodium ions in SPCE. The assembled sodium symmetric cells display a high critical current density of up to 2.7 mA cm-2 and stable cycling performance for 700 hours at 0.5 mA cm-2. Furthermore, the Na/SPCE-9/Na3V2(PO4)3 maintains a discharge specific capacity of up to 76.8 mAh g-1 at 10 C and shows impressive long-cycle stability, retaining 86.2 % of initial capacity over 5000 cycles with an average coulombic efficiency of 99.9 %. Our work presents a high-performance SPCE with intrinsic safety, providing valuable insights for the future design of solid-state SMBs.

Histology Assessment of Chitosan–Polyvinyl Alcohol Scaffolds Incorporated with CaO Nanoparticles

Scaffolds for regenerative therapy can be made from natural or synthetic polymers, each offering distinct benefits. Natural biopolymers like chitosan (CS) are biocompatible and biodegradable, supporting cell interactions, but lack mechanical strength. Synthetic polymers like polyvinyl alcohol (PVA) provide superior mechanical strength and cost efficiency but are not biodegradable or supportive of cell adhesion. Combining these polymers optimizes their advantages while adding metal oxide nanoparticles like calcium oxide (CaO NPs) enhances antimicrobial properties by damaging bacterial membranes. In this study, we obtained the formation of CaO NPs by calcinating eggshells, which were mixed in a polymeric network of CS and PVA to obtain four different membrane formulations for subdermal tissue regeneration. The spherical nanoparticles measured 13.43 ± 0.46 nm in size. Their incorporation into the membranes broadened the hydroxyl bands in the Fourier transform infrared (FTIR) analysis at 3331 cm⁻1. X-ray diffraction (XRD) analysis showed changes in the crystalline structure, with new diffraction peaks at 2θ values of 7.2° for formulations F2, F3, and F4, likely due to the increased amorphous nature and concentration of CaO NPs. Additionally, higher CaO NPs concentrations led to a reduction in thermal properties and crystallinity. Scanning electron microscopy (SEM) revealed a heterogeneous morphology with needle-like structures on the surface, resulting from the uniform dispersion of CaO NPs among the polymer chains and the solvent evaporation process. A histological examination of the implanted membranes after 60 days indicated their biocompatibility and biodegradability, facilitated by incorporating CaO NPs. During the degradation process, the material fragmented and was absorbed by inflammatory cells, which promoted the proliferation of collagen fibers and blood vessels. These findings highlight the potential of incorporating CaO NPs in soft tissue regeneration scaffolds.

Temperature-Directed Morphology Transformation Method for Precision-Engineered Polymer Nanostructures.

With polymer nanoparticles now playing an influential role in biological applications, the synthesis of nanoparticles with precise control over size, shape, and chemical functionality, along with a responsive ability to environmental changes, remains a significant challenge. To address this challenge, innovative polymerization methods must be developed that can incorporate diverse functional groups and stimuli-responsive moieties into polymer nanostructures, which can then be tailored for specific biological applications. By combining the advantages of emulsion polymerization in an environmentally friendly reaction medium, high polymerization rates due to the compartmentalization effect, chemical functionality, and scalability, with the precise control over polymer chain growth achieved through reversible-deactivation radical polymerization, our group developed the temperature-directed morphology transformation (TDMT) method to produce polymer nanoparticles. This method utilized temperature or pH responsive nanoreactors for controlled particle growth and with the added advantages of controlled surface chemical functionality and the ability to produce well-defined asymmetric structures (e.g., tadpoles and kettlebells). This review summarizes the fundamental thermodynamic and kinetic principles that govern particle formation and control using the TDMT method, allowing precision-engineered polymer nanoparticles, offering a versatile and an efficient means to produce 3D nanostructures directly in water with diverse morphologies, high purity, high solids content, and controlled surface and internal functionality. With such control over the nanoparticle features, the TDMT-generated nanostructures could be designed for a wide variety of biological applications, including antiviral coatings effective against SARS-CoV-2 and other pathogens, reversible scaffolds for stem cell expansion and release, and vaccine and drug delivery systems.

Effect of Various Diamines on the Mechanical, Thermal, and High‐Frequency Dielectric Properties of Polyimide and Their Composites With Functionalized Hollow Silica Fiber

ABSTRACTIn this study, three different series of polyimides (PIs) and their composites fabricated using various chemical structure of diamines and functionalized hollow silica fiber (FHSF) were synthesized. The experimental results of three PIs indicate that the addition of fluorine atoms into the pending groups of PI can decrease the glass transition temperature (Tg) with increase in the chain flexibility and this can lower the dielectric constant of PI. The high‐frequency dielectric constants of the composite materials decrease with increase in the loadings of FHSF. These phenomena are possibly accredited to the steric hindrance effect caused by the presence of trifluoromethyl groups of PI polymer chain and FHSF, which can interrupt the PI chain packing and increase their free volumes, resulting in the decrease of Tg and the dielectric properties of PIs. The high‐frequency circuit transmission loss properties of fabricated composite materials measured using the Test Methods Manual IPC‐TM 650 2.5.5.14 are lower than those of pure polymer matrix, recommending that the prepared materials could be selected as interlayer dielectrics for nano‐level electronic.

Comparative Study of Polymer Globules and Liquid Droplets in Poor Solvents: Effects of Cosolvents and Solvent Quality.

We compare the structures of polymer globules, composed of flexible polymer chains, with liquid droplets made of nonbonded monomers of the same polymer in poor solvents. This comparison is performed in three different poor solvents, with and without the addition of cosolvents. Molecular dynamics simulations are used to analyze the properties of the polymer globules, while semigrand canonical Monte Carlo simulations are used to form metastable liquid droplets of nonbonded monomers through homogeneous nucleation in the same solvents. Our findings show that both globules and droplets are nearly spherical, although droplets display slightly more anisotropy. In the absence of cosolvents, the surrounding solvent structures are similar for both globules and droplets. However, in the presence of cosolvents, significant differences arise in the liquid structure, with the disparities increasing as the solvent quality worsens. Cosolvents tend to accumulate near the surface of globules due to the restricted movement of bonded monomers, which partially immobilizes the cosolvents. This effect becomes more pronounced as the solvent quality declines. Interfacial free energy calculations reveal that cosolvents act like surfactants, promoting larger interfacial areas for both globules and droplets. This effect is more significant for globules due to the greater accumulation of cosolvents at their surface. Therefore, modeling polymer globules as liquid droplets may underestimate the impact of cosolvents on the stability of the globule state. Additionally, the transition states involved in polymer collapse in the presence of cosolvents differ from those involved in the nucleation of liquid droplets in the same solution.

A Chain Entanglement Gelled SnO₂ Electron Transport Layer for Enhanced Perovskite Solar Cell Performance and Effective Lead Capture.

SnO₂ is a widely used electron transport layer (ETL) material in perovskite solar cells (PSCs), and its design and optimization are essential for achieving efficient and stable PSCs. In this study, the in situ formation of a chain entanglement gel polymer electrolyte is reported in an aqueous phase, integrated with SnO₂ as the ETL. Based on the self-polymerization of 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propane-1-sulfonic acid (DAES) in an aqueous environment, combining the catalytic effect of LiCl (as a Lewis acid) with the salting-out effect, and the introduction of polyvinylpyrrolidone (PVP) as the other polymer chain, a chain entanglement gelled SnO2 (G-SnO2) structure is successfully constructed with a wide range of functions. The PDEAS-PVP chain entanglement gel achieves passivation and Pb2⁺ capture through chemical chelation mechanisms is explored. The results demonstrated that the all-in-air prepared PSC based on G-SnO2 exhibited an excellent power conversion efficiency (PCE) of 24.77% and retained 83.3% of their initial efficiency after 2100 h of air exposure. Additionally, the PDEAS-PVP exposes more C═O and S═O active sites, significantly enhanced the lead absorption capability of the PSCs.

Synergistic oxidative modification and covalent cross-linking for the construction of sesbania gum-based high efficiency dust suppression foam sols.

To effectively utilize sesbania gum in coal dust control and address the limitations of excessive viscosity and mediocre strength, oxidation treatment was used to improve its fluidity. Polyvinyl alcohol (PVA) and sodium trimetaphosphite (STMP) were used to enhance oxidized sesbania gum OSG, and crosslinking technology was used to improve its mechanical stability. This study developed a novel foam dust suppressant OSG-PVA/SDBS by response surface design, and the optimized dust suppressant material exhibited excellent adhesion and curing properties. It was found that sulfonic acid groups (-SO3H) of SDBS gradually congregate to occupy the binding site on the OSG-PVA polymer chain, bolstering the water-locking capacity of the liquid film and the foam stability. Concurrently, the hydrophobic tail chains in SDBS adsorb onto the hydrophobic points on the coal surface, establishing a dual adsorption mechanism. Simulation revealed that the thickness of water molecule absorption layer increased by 11.3 Å under this dual adsorption, strengthening the interaction between coal and water. After repeated wind erosion and rain washing, the coal samples sprayed with OSG-PVA/SDBS exhibited low wind erosion rate (22.64 %) and rain erosion rate (23.22 %). Moreover, the dust suppression rate surpassed 95 % following outdoor application of the suppressant foam. These results offer innovative perspectives and strategies for the research and mitigation of coal dust pollution.

Tripodal Triptycenes as a Versatile Building Block for Highly Ordered Molecular Films and Self-Assembled Monolayers.

ConspectusThe design of properties and functions of molecular assemblies requires not only a proper choice of building blocks but also control over their packing arrangements. A highly versatile unit in this context is a particular type of triptycene with substituents at the 1,8,13-positions, called tripodal triptycene, which offers predictable molecular packing and multiple functionalization sites, both at the opposite 4,5,16- or 10 (bridgehead)-positions. These triptycene building blocks are capable of two-dimensional (2D) nested hexagonal packing, leading to the formation of 2D sheets, which undergo one-dimensional (1D) stacking into well-defined "2D+1D" structures. This ability makes it possible to form large-area molecular films having long-range structural integrity even on polymer substrates, which can be used to enhance the performance of organic devices. Importantly, the 2D assembly ability of tripodal triptycenes is robust and not impaired when chemically modified with functional molecular units and even with polymer chains. In addition, introducing suitable functionalities that act as anchoring groups results in reliable tripodal monomolecular assembly on application-relevant inorganic substrates, which is generally considered quite a challenging task. Self-assembled monolayers (SAMs) have been formed on Au(111), Ag(111), and indium tin oxide. On gold, these SAMs feature the nested hexagonal packing typical of 2D triptycene sheets, whereas, on silver, a distinct polymorphism with several different packing motifs occurs. Along with basic, nonsubstituted tripodal SAMs, specifically functionalized monolayers have been designed. A substitution pattern in which three nitrile tail groups build the outermost surface of a tripodal triptycene-based SAM has allowed for the study of femtosecond charge transfer dynamics across the triptycene framework, with a particular emphasis on the so-called matrix effects involving intramolecular pathways. The functionalization of the bridgehead position with a ferrocene tail group has enabled single-molecule observation of redox reactions and the creation of assemblies of unique molecular rectifiers, exhibiting highly effective rectification at a very low bias voltage. Complementary to the synthesis of these complex functional triptycenes, a strategy of on-surface click reactions has been designed. Indeed, a tripodal triptycene having an ethynyl tail group at the 10-position, capable of click reactions with azide functionalities, works well, allowing successive molecular layer deposition. The performance of tripodal triptycene-based SAMs has also been tested in the context of electron beam lithography (EBL) and nanofabrication, leading to the finding that these SAMs can serve as negative resists for EBL due to the efficient cross-linking, giving rise to triptycene-stemming carbon nanomembranes (CNM). These membranes feature the lowest lateral material densities used to date for CNM preparation, which makes them unique in this regard.

Water-responsive Contraction for Shape-adaptive Bioelectronics

Water-responsive adaptive contraction represents a pivotal advancement in bioelectronics, offering unparalleled advantages over traditional swollen hydrogels and actuator-based systems. This review explores mechanisms including phase transition, hydrogen bond disruption, and hierarchical hybridization to enable rapid and substantial shape adaptability upon moisture exposure without external control and highlights various component modulation and porous and heterostructure engineering strategies to provide directional control and multifunctionality. Additionally, recent advances in supercontractile films, achieved through cold-drawing processes that disrupt hydrogen bonds in aligned polymer chains are overviewed for wearable and implantable biomedical applications where seamless tissue interfacing is essential. These advances address long-standing challenges in device integration with biological tissues, such as rigidity and inflammation, by creating electrodes that naturally conform to tissue shapes. This review delves into water-responsive adaptive contraction in bioelectronics, emphasizing its potential to revolutionize medical implants, wearable health monitors, and soft robotics by naturally conforming to tissue shapes upon moisture exposure. They promise significant improvements in chronic electronic integration and patient care, paving the way for next-generation medical devices, soft robotics, and smart textiles that adapt dynamically to biological environments.

Chiral Nanostructures from Artificial Helical Polymers: Recent Advances in Synthesis, Regulation, and Functions.

Helical structures such as right-handed double helix for DNA and left-handed α-helix for proteins in biological systems are inherently chiral. Importantly, chirality at the nanoscopic level plays a vital role in their macroscopic chiral functionalities. In order to mimic the structures and functions of natural chiral nanoarchitectures, a variety of chiral nanostructures obtained from artificial helical polymers are prepared, which can be directly observed by atomic force microscopy (AFM), scanning tunneling microscopy (STM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). This review mainly focuses on the formation of chiral nanostructures and the morphology regulation triggered by polymer chain length, concentration, solvent, temperature, photoirradiation, and chemical additives. In addition, the distinct chiral functions including chiral recognition, circularly polarized luminescence, drug release, cell imaging, and antibiosis are also discussed.

Syntheses and structures of two coordination polymers formed by Ni(cyclam)2+ cations and sulfate anions

The asymmetric units of catena-poly[[(1,4,8,11-tetraazacyclotetradecane-κ4 N 1,N 4,N 8,N 11)nickel(II)]-μ2-sulfato-κ2 O 3:O 4], [Ni(SO4)(C10H24N4)] n (I), and catena-poly[[(1,4,8,11-tetraazacyclotetradecane-κ4 N 1,N 4,N 8,N 11)nickel(II)]-μ2-sulfato-κ2 O 3:O 4] hemi[4,4′,4′′,4′′′-(2,2′,4,4′,6,6′-hexamethyl-[1,1′-biphenyl]-3,3′,5,5′-tetrayl)tetrabenzoic acid] nonahydrate], {[Ni(SO4)(C10H24N4)]2·C46H38O8·18H2O} n (II), consist of two crystallographically unique centrosymmetric macrocyclic dications and a sulfate dianion. In II it includes additionally a molecule of the undissociated acid (2,2′,4,4′,6,6′-hexamethyl[1,1′-biphenyl]-3,3′,5,5′-tetrayl)tetra(benzoic acid) located on a crystallographic twofold axis and nine highly disordered water molecules of crystallization. In both compounds, the metal ions are coordinated in the equatorial plane by the four secondary N atoms of the macrocyclic ligand, which adopts the most energetically stable trans-III conformation. Two O atoms of the sulfate anions occupy the trans-axial positions resulting in a slightly tetragonally distorted trans-NiN4O2 octahedral coordination geometry. The crystals of both compounds are composed of parallel coordination polymeric chains running along the [101] and [100] directions in I and II, respectively. The distances between the neighboring metal ions in the chains are significantly different [6.5121 (6) Å in I and 6.0649 (3) Å in II] and this peculiarity is explained by the different spatial directivity of the Ni—O coordination bonds (different S—O—Ni angles). As a result of the C—H...O hydrogen bonds between the methylene groups of the macrocyclic ligands and the non-coordinated O atoms of the sulfate anion, the coordination-polymeric chains in I are arranged in the two-dimensional layers oriented parallel to the (010) and (101) planes, the intersection of which provides the three-dimensional coherence of the crystals. The three-dimensional supramolecular structure of the crystals II is determined by the network of strong hydrogen bonds formed by the carboxylic acid and the non-coordinated O atoms of the sulfate anions.

Photoinduced Energy/Electron Transfer within Single-Chain Nanoparticles.

We demonstrate that single-chain nanoparticles (SCNPs) - compact covalently folded single polymer chains - can increase photocatalytic performance of an embedded catalytic center, compared to the comparable catalytic system in free solution. In particular, we demonstrate that the degree of compaction allows to finely tailor the catalytic activity, thus evidencing that molecular confinement is a key factor in controlling photocatalysis. Specifically, we decorate a linear parent polymer with both photoreactive chalcone moieties as well as Ru(bpy)3 catalytic centers. We initially construct a SCNP via a photosensitized [2+2] cycloaddition at 510nm and demonstrate that the SCNP formation is substantially more efficient when the Ru(bpy)3 units are part of the polymer chain instead of as free molecules in solution. Subsequently, we employ the same Ru(bpy)3 units as photocatalysts in a model reaction employing pyrene units as charge transfer moieties. We establish that the photocatalytic activity increases as the polymer becomes more compact, reaching peak efficiency, followed by a subsequent decline as the SCNP becomes too compact. Thus, we identify a goldilocks regime of catalyst confinement via SCNP compaction for use in photocatalysis.