Despite the promise of vitrimeric materials applications, there are many aspects that remain poorly understood. To advance the fundamental knowledge of these materials, model systems of well-controlled composition are needed. Here we report the synthesis of polybutadiene-based model vitrimers, which are further investigated with respect to their structure and dynamic properties. Four vitrimers with different cross-linking concentrations were obtained by modifying the molecular weight of the precursor functionalized polybutadiene precursors. A tetrafunctional aromatic cross-linker was used in all cases. Due to the nature of the cross-linker, the resulting vitrimers exhibit fluorescence indicative of cross-linker association. The structural investigation by small-angle X-ray diffraction showed that the cross-linkers cluster together to form very stable cylindrical structures linked by polybutadiene chains. The dynamic behavior of the vitrimers, as studied by differential scanning calorimetry and broadband dielectric spectroscopy, can be interpreted by the presence of such a cluster structure, where already a few degrees above the glass transition there are significant fluctuations of the dynamic covalent bonds, which remain essentially limited to the intracluster level-i.e., confined in the interphase between the cross-linkers' clusters and the polymer. This results in rubber-like vitrimeric materials in which the mechanical stability is maintained by the cluster network as long as it is not perturbed by the application of high mechanical stresses, in stark contrast to recently investigated polyisoprene-based model vitrimers with flexible triamine cross-linkers, which also exhibit cluster structure.

Although the use of dynamic covalent bonding (DCB) is a promising method to obtain easily recyclable polymer networks, there are many aspects of the incorporation of dynamic covalent bonding into polymer systems that remain poorly understood. In order to gain insight into the fundamentals of these materials, well-controlled model systems are required. Here, we present the synthesis of polyisoprene (PI)-based 3-arm stars containing vinylogous urethane DCBs as linkers of the PI arms to the core of the star. The dynamics of these 3-arm stars, with three different arm sizes, is studied by broadband dielectric spectroscopy. A conventional (static) 3-arm PI star of intermediate size has also been synthesized and studied, and all results are directly compared with those of a linear PI chain. A prominent intermediate relaxation between those identified as the slower normal mode and the faster α-relaxation of PI is found in the stars containing DCBs. This relaxation, which becomes more significant as the molecular mass of the PI arms decreases, seems to originate from the dynamic bond exchange that occurs at the level of the star's core. On the other hand, the arm retraction dynamics responsible for the normal mode relaxation do not show significant differences with respect to that observed in the static star.

The scaling behavior of linear chains with reversible bonds and, in particular, its dependence on the concentration are fundamental problems of polymer physics that are not fully understood. By means of small-angle neutron scattering we investigate the conformations of reversibly bonding polymers from high dilution (where they form unimacromolecular nano-objects, usually known as single-chain nanoparticles) to crowded solutions and bulk state far above the overlap concentration (where they are expected to form a dynamic polymer network). Unlike the cases of simple linear chains with no bonds and of chains with strictly intramolecular irreversible bonds, no shrinkage is found, and the size and scaling exponent of the reversibly bonding polymers are essentially unperturbed by crowding. This is a relevant result that confirms the negligibility of many-body effects beyond the overlap concentration in crowded systems of reversibly bonding polymers and the validity of ultrasoft effective interactions for predicting their structural and phase behavior.

Two different amphiphilic copolymers, a random copolymer (RCP) and a block copolymer (BCP), have been used to encapsulate a far-red photosensitizing hydrophobic zinc phthalocyanine while forming self-assembled nanocarriers of different topology: self-folded single-chain nanoparticles (SCNPs) and star-like aggregates (SLAs), respectively. Different copolymer/phthalocyanine ratios have been tested to assess their effect on structural properties which were determined by small-angle X-ray scattering (SAXS) measurements. The relevance of these materials as photosensitizer nanocarriers for photodynamic therapy (PDT) has been studied against human breast cancer cells (MCF-7). A better PDT effect was found for the SCNP-Pc2x (100 mu g mL-1) excited at 800 nm with a pulsed laser than for the SLA-Pc2x under identical conditions. Conversely, irradiation at slightly lower wavelengths (740 nm) of MCF-7 cells incubated with SLA-Pc2x resulted in a notorious PDT effect when compared to that observed for MCF-7 cells incubated with the SCNP-Pc2x. These systems represent new strategies for the encapsulation of photosensitizers for photodynamic therapy.

Carbon dots (CDs) are highly versatile nanomaterials with promising applications across catalysis, sensing, biotechnology, and optoelectronics. Yet, despite the widespread interest, their internal structure and permeability to solvents remain poorly understood. In this study, novel insights are provided into the plasticizing effect of water on amorphous CDs, addressing a critical gap in the current knowledge. A new class of polyamide-based CDs is synthesized via a microwave-assisted reaction using an amino acid and a small polyamine in water, systematically varying reaction times (3 - 60 min) to tailor the compactness of the carbon core. These findings reveal that water can permeate the internal structure of CDs and act as a plasticizer, significantly lowering their glass transition temperature, as shown by calorimetric analyses. Less compact CDs absorbed more water, while denser ones showed lower permeability. These trends are further corroborated by X-ray scattering data. This report clearly demonstrates that the carbonaceous core of CDs is accessible to water, challenging the assumption that the nanoparticles are structurally impermeable. These results lay the groundwork for new structural models of CDs and open exciting opportunities for diffusion studies, functional design, and targeted applications in nanoscience.

Comparison of the non-conducting polymer binders for hybrids based on Li 3 InCl 6 . Ordered nanostructured SEBS block copolymer provides more tortuous pathways for Li ions in the inorganic electrolyte (Li 3 InCl 6 ) than disordered PIB homopolymer.

Neutron spin echo experiments on deuterated and protonated molecular liquids with different interactions have revealed their coherent and incoherent scattering functions at the mesoscale. The coherent one decays by a nondiffusive exponential relaxation process that can be related to stress fluctuations. For self-dynamics, we show that even though diffusion is, as expected, the predominant relaxation channel at the mesoscale, the process observed for collective dynamics also appears at short times, evidencing the influence of stress fluctuations on translational motions even at high temperatures.

Enhancing the dielectric performance of poly(vinylidene fluoride) (PVDF) for energy storage hinges on precise control of its crystalline phases. This study explores the integration of single-chain nanoparticles (SCNPs), synthesized from PMMA-based copolymers, into PVDF blends to tailor phase behavior and nanostructure. Through thermal, morphological, and structural analyses (DSC, SAXS/WAXS, FTIR), we demonstrate that SCNPs suppress alpha-phase crystallization, instead stabilizing the gamma-phase at low SCNP content (25 wt%) and the beta-phase at intermediate compositions (50 wt%). However, SCNPs induce microphase segregation, in contrast to the homogeneous mixing observed in linear precursor blends. PVDF-based blends retain significant crystallinity (up to similar to 57 %) even in SCNP-rich matrices, although high SCNP content (>75 wt%) yields near-amorphous structures. In contrast, the precursor samples remain crystalline across all compositions studied, even at low PVDF content. These results underscore SCNPs' dual role as crystallization modifiers and nanoscale heterogenizers, offering a strategic pathway to optimize PVDF's dielectric properties. By bridging macromolecular engineering with phase-structure control, this work advances PVDF-based composites for high-energy-density capacitors, highlighting SCNPs as versatile tools for polymer dielectric design.

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. Under crowding conditions, the internal dynamics remains essentially unchanged, but the center-of-mass diffusion slows down. The effective viscosity felt by the SCNPs at the timescales probed by NSE is lower than the macroscopic viscosity of the crowder solution, and it does not depend significantly on the molecular weight.

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). These ultrasmall, soft nanoparticles have various applications, including catalysis, sensing, and nanomedicine. Initial in vitro experiments with nonfunctionalized, amphiphilic SCNPs loaded with a photosensitizing Zn phthalocyanine with four nonperipheral isobutylthio substituents, ZnPc, showed promise for PDT. Herein, the preparation of improved, amphiphilic SCNPs containing ZnPc as highly efficient photosensitizer encapsulated within the nanoparticle and surrounded by anthracene units is disclosed. The amount of anthracene groups and ZnPc molecules within each single-chain nanoparticle controls the imaging and PDT properties of these nanocarriers. Critically, this work opens the way to improved PDT applications based on amphiphilic SCNPs as a first step toward ideal, long-term artificial photo-oxidases (APO).

Polymer vitrimers are a new class of materials that combine the advantages of thermoplastics and thermosets. This is due to the dynamic nature of the chemical bonds linking different chains. However, how this property affects the polymer dynamics at different length scales is still an open question. Here, we investigate the dynamics of model vitrimers based on well-defined polyisoprene (PI) chains using broadband dielectric spectroscopy. In this way, we study the polymer dynamics from the segmental to the whole chain scale, taking advantage of the fact that PI belongs to the class of molecules that exhibit a net dipole moment associated with the end-to-end vector. Three distinct relaxation phenomena are identified. The fastest relaxation is attributed to the segmental PI dynamics with a small influence of the cross-linking. An intermediate relaxation attributed to the dipolar character of the cross-linker is also observed. The slower identified relaxation component, corresponding to limited fluctuations of the end-to-end PI chains, is found to be determined by the dynamics of the clusters formed by the cross-linkers with an average time scale orders of magnitude faster than that of the terminal relaxation as inferred from the viscous flow.

The urban heat island effect has become a critical issue in urban areas, intensifying heat-related problems and increasing energy consumption. A sustainable cement formulation that combines ordinary Portland cement (OPC) with a carbonated aggregate derived from Periwinkle shell powder for the development of an efficient cool material is presented. Through a carbonation process, the aggregate undergoes a transformation, capturing carbon dioxide (CO2) and converting it into calcite. The resulting cement mixture exhibits high solar reflective properties, making it a potential candidate for cool pavement and roof applications. In this study, the raw materials, including the Periwinkle shell powder, were characterized, and the carbonation process was evaluated to quantify the CO2 capture efficiency. Additionally, a real test of the efficiency of this new cement on a roof demonstrated that the material achieved a significant cooling effect, being 6 °C cooler than that with standard OPC at the peak of solar radiation.

Geopolymers, a class of sustainable inorganic materials derived from natural and recycled resources, hold promise for various applications, including thermoelectric power generation. This study delves into the thermoelectric properties of Ikere white (IKW)-geopolymer, derived from kaolin clay, by employing rigorous measurements of thermal conductivity, electrical conductivity, and Seebeck coefficient. The investigation elucidates the pivotal role of temperature and ions in shaping the thermoelectric performance of IKW-geopolymer. Electrical conductivity analysis pinpoints ions within the geopolymer's channels as primary contributors. Beyond a critical temperature, the evaporation of bulk water triggers a transition of charge carriers from one- to three-dimensional motion, resulting in reduced conductivity. The Seebeck coefficient exhibits a range from -182 to 42 mu V/K, with its time-dependent profile suggesting that ions potentially drive thermoelectricity in cementitious materials. Notably, a unique transition from n-type to p-type behavior was observed in the geopolymer, opening new avenues for ionic thermoelectric capacitors. These insights advance our understanding of thermoelectric behavior in geopolymers and have the potential to propel the development of novel building materials for energy conversion applications.

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.g., pH, temperature, light, and redox potential) or substances (e.g., competitive reagents, solvents, and anions) is well known. Conversely, methods for the unfolding (i.e., intrachain disassembly) of SCNPs with stronger covalent interactions are scarce. We show that trimethylsilanol (Me3SiOH) triggers the efficient unfolding of robust "Staudinger" SCNPs with stable azaylide (-N=P-) moieties as intrachain cross-linking units showing exceptional stability toward water, air, and CS2, a standard reagent for azaylides. As a consequence, Me3SiOH arises as a rare, exceptional, and valuable reagent for the cleavage of stable azaylides prepared by the nonhydrolysis Staudinger reaction.

Temperature-modulated colloidal phase of plasmonic nanoparticles is a convenient playground for resettable soft-actuators or colorimetric sensors. To render reversible clustering under temperature change, bulky ligands are required, especially if anisotropic morphologies are of interest. This study showcases thermoresponsive gold nanorods by employing small surface ligands, bis (p-sulfonatophenyl) phenyl-phosphine dihydrate dipotassium salt (BSPP) and native cationic surfactant. Temperature-dependent analysis in real-time allowed to describe the structural features (interparticle distance and cluster size) as well as thermal parameters, melting and freezing temperatures. These findings suggest that neither covalent Au-S bonds nor bulky ligands are required to obtain a robust thermoresponsive system based on anisotropic gold nanoparticles, paving the way to stimuli-responsive nanoparticles with a wide range of sizes and geometries.

We have combined X-ray diffraction, neutron diffraction with polarization analysis, small-angle neutron scattering (SANS), neutron elastic fixed window scans (EFWS), and differential scanning calorimetry (DSC) to investigate polymeric blends of industrial interest composed by isotopically labeled styrene-butadiene rubber (SBR) and polystyrene (PS) oligomers of size smaller than the Kuhn length. The EFWS are sensitive to the onset of liquid-like motions across the calorimetric glass transition, allowing the selective determination of the "microscopic" effective glass transitions of the components. These are compared with the "macroscopic" counterparts disentangled by the analysis of the DSC results in terms of a model based on the effects of thermally driven concentration fluctuations and self-concentration. At the microscopic level, the mixtures are dynamically heterogeneous for blends with intermediate concentrations or rich in PS, while the sample with highest content of the fast SBR component looks as dynamically homogeneous. Moreover, the combination of SANS and DSC has allowed determining the relevant length scale for the α-relaxation through its loss of equilibrium to be ≈30 Å. This is compared with the different characteristic length scales that can be identified in these complex mixtures from structural, thermodynamical, and dynamical points of view because of the combined approach followed. We also discuss the sources of the non-Gaussian effects observed for the atomic displacements and the applicability of a Lindemann-like criterion in these materials.

By means of massive (more than 1.2 · 106 molecules) molecular dynamics simulations at 300 K we have disentangled self- and cross-dipolar contributions to the dielectric relaxation of liquid water that cannot be experimentally resolved. We have demonstrated that cross dipolar correlations are of paramount importance. They amount for almost a 60% of the total dielectric amplitude. The corresponding relaxation function is a one-step Debye-like function with a characteristic time, τcross, of the order of the phenomenological Debye time, τD. In contrast, the relaxation function corresponding to the self-contribution is rather complex and contains a fast decay related to dipolar librations and a second relaxation step that can be well described by two exponentials: a low-amplitude fast process (τ0 = 0.31 ps) and a main slow process (τself = 5.4 ps) that fully randomizes the dipolar orientation. In addition to dipolar relaxation functions, we have also calculated scattering-like magnitudes characterizing translation and rotation of water molecules. Although these processes can be considered as "jump" processes in the short time range, at the time scale of about τD-τcross, at which the cross-dipolar correlations decay to zero, the observed behavior cannot be distinguished from that corresponding to uncoupled Brownian translational and rotational diffusion. We propose that this is the reason why the Debye model, which does not consider intermolecular dipolar interactions, seems to work at time t ≳ τD.

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. Considering all the contributions of the RPA leads to an accurate estimation of the single chain form factor parameters and the Flory-Huggins interaction parameter between PMMA and DMF. The value of the latter in the dilute regime indicates that the precursors and the SCNPs are in good solvent conditions, while in crowding conditions, the polymer becomes less soluble.

Uncertainties associated with durability and sustainability of geopolymer due to formation of efflorescence, shrinkage and activator cost are setbacks for its real-life applications. Therefore, the aim of this study was to produce geopolymers with improved durability and sustainability using local kaolin clay as precursor, cocoapods-ash (CPA) as alternative alkali hydroxide activator, periwinkle-shells-ash (PSA) as hardener and quarrydust (QD) as filler. Local kaolin clay calcined at 700 degrees C (M7C), was replaced with some fractions of CPA and activated with only Na2SiO3 to produce binders (CPAG). The PSA was added to the best fit of M7C/CPA as fastsetting-agent, while QD was added to the best fit of M7C/CPA/PSA to produce mortars. 100% kaolin clay activated with 8MNaOH/Na2SiO3 was used as reference geopolymer. The geopolymers were cured at R.T for 7 and 28 days and characterised for physical, mechanical and durability properties. Clay, CPA, PSA, QD and geopolymers were characterised using XRF, ATR-FTIR and XRD. Reactivity was studied using isothermal conduction calorimetry. The ATR-FTIR and XRD results indicated transformation of kaolinite to metakaolinite in the clay, presence of K-C-O bond in CPA and O-C-O bond in PSA. Reference geopolymers set at 4 h while CPAG ranged from 14 to 19 h. With the addition of PSA, setting time reduced to values between 4 and 11 h. The compressive strength of reference geopolymer was 18.1 & PLUSMN; 0.3 MPa at 28 days, while CPAGs values ranged from 23.5 & PLUSMN; 0.3 to 35.6 & PLUSMN; 0.3 MPa. Best compressive strength was achieved with 2% PSA addition. No shrinkage in CPA-containing geopolymers while reference geopolymer had value of 0.03%. Efflorescence tendencies of the CPA-containing geopolymers reduced by 25-75% when compared with reference. Application of CPA as alternative activator improved the mechanical property, durability and sustainability of geopolymers.

By using time-of-flight neutron spectroscopy with polarization analysis, we have separated coherent and incoherent contributions to the scattering of deuterated tetrahydrofuran in a wide scattering vector (Q)-range from meso- to inter-molecular length scales. The results are compared with those recently reported for water to address the influence of the nature of inter-molecular interactions (van der Waals vs hydrogen bond) on the dynamics. The phenomenology found is qualitatively similar in both systems. Both collective and self-scattering functions are satisfactorily described in terms of a convolution model that considers vibrations, diffusion, and a Q-independent mode. We observe a crossover in the structural relaxation from being dominated by the Q-independent mode at the mesoscale to being dominated by diffusion at inter-molecular length scales. The characteristic time of the Q-independent mode is the same for collective and self-motions and, contrary to water, faster and with a lower activation energy (≈1.4 Kcal/mol) than the structural relaxation time at inter-molecular length scales. This follows the macroscopic viscosity behavior. The collective diffusive time is well described by the de Gennes narrowing relation proposed for simple monoatomic liquids in a wide Q-range entering the intermediate length scales, in contraposition to the case of water.