Designing thermo-sensitive metal nanoparticles involves capping the nanoparticle surface with thermoresponsive polymers that reversibly swell or collapse with temperature changes, making them promising for biomedical applications such as drug delivery and minimally invasive therapies. For this, programmable collapse transition temperatures are necessary which can be achieved by grafting the nanoparticle with diblock copolymers having varying hydrophobicity. In this study, we examine the conformational behaviour of generic diblock copolymer chains grafted on a generic nanoparticle in aqueous solutions with varying temperature, with systematic variation in hydrophobic content of the polymers. Using molecular dynamics simulations, a microscopic view of the effects of polymer hydrophobicity on the effective size of the nanoparticle, conformational preferences of the polymer chains and effects on the energetic interactions are examined. The results indicate that with 30 to 70% polymer hydrophobicity, the polymers have the highest conformational flexibility and show the most responsive behaviour. With increasing polymer hydrophobicity, the collapse temperature is seen to reduce. The effective size of the nanoparticle at high temperatures is seen to reduce via bending of polymers on the nanoparticle surface or via chains collapsing completely into each other. This is promoted by the favourable polymer-nanoparticle interaction energy and unfavourable polymer-water interaction energy. Therefore, the results provide a rational design for controllable interactions of the polymer grafted nanoparticle with the surrounding solvent, thus enabling responsiveness at different temperatures.
Chirality is a fundamental feature underpinning complexity within the natural world. Efforts aimed at replicating chiral emergence and propagation observed in Nature have led to significant advances in synthetic chemistry,...
This work builds interpolative models to predict surfactant interface behavior for firefighting foam formulations on ethanol and gasoline fuels by combining design of experiment methodologies with molecular dynamic simulations. Given the complex nature of surfactant interface performance, we chose to combine these two methods to map out the relationship between changing the molecular structure of the surfactant to the performance of the interface system. Specifically, we utilized a central composite response surface design to relate surfactant molecule surface area and amount of hydrophilicity/hydrophobicity to various interfacial properties at the molecular scale. These interfacial properties include linear interaction energies between combinations of surfactant molecules and solvent molecules, hydrogen bonding interactions, and interface density information. This study was performed for neat dilute (16 surfactants per interface layer) interfaces, neat concentrate (63 surfactants per interface layer) interfaces, and formulated (main surfactant plus two co-surfactants) interfaces. We then validated the statistically significant response models from this study with six experimental surfactants that fall within the design scope. This produced 13 models, of which 7 for the neat interface condition and 6 for the formulated interface condition. Demonstrating an enhanced theoretical framework for efficient identification and exploration of key relationships between molecular structure and interfacial properties, the potential impact of this work is accelerating the design of optimal surfactants for firefighting foams.
Active superparamagnetic colloids represent a promising platform for reconfigurable, field-guided self-assembly, since their magnetic attraction and self-propulsion can be adjusted independently. Here, we investigate the aggregation kinetics of dilute suspensions of active superparamagnetic colloids under a strong uniform magnetic field using Brownian dynamics (BD) simulations. In this regime, the induced dipoles remain aligned with the external field, while the particle bodies retain Brownian rotational diffusion, allowing the propulsion direction to evolve independently of the dipole orientation. This decoupling enables self-propulsion to compete directly with dipole-dipole attraction, thereby modifying the classical chaining dynamics of passive superparamagnetic particles. In the passive limit, the simulations recover the established power-law growth of magnetic chains, with kinetic exponents z approximate to 0.76-0.81. When activity is introduced, the dynamics are governed by the dimensionless ratio beta = Pe/lambda, where Pe is the P & eacute;clet number and lambda is the dipolar coupling strength. For beta < 0.2, chains exhibit sustained power-law growth. For 0.2 <= beta < 1, growth is arrested and the mean chain size decreases towards the singlet limit as beta approaches unity. Local doublet destabilization begins near beta approximate to 0.7; as beta approaches unity, aggregation is strongly suppressed, and for beta >= 1, no aggregation is observed. In the arrested regime, the long-time mean cluster size obeys the scaling law < N-c >(t ->infinity) similar to beta(-1.7). A complementary force-balance analysis further predicts doublet destabilization near beta approximate to 0.7, consistent with the crossover from finite-chain steady states to nearly singlet suspensions. These results show that activity disrupts the classical chain-growth law by establishing a nonequilibrium balance between aggregation and fragmentation, providing a quantitative framework for tuning the structure of magneto-active colloidal suspensions through the single control parameter beta.
Alkyl chain length is commonly regarded as a passive determinant of lipophilicity in bioactive molecules. Here, we demonstrate that it functions instead as a molecular switch that reprograms supramolecular organization and transport-related behavior in dialkyl 2-(((4-acetamidophenyl)amino)propan-2-yl)phosphonates. A combined experimental-theoretical investigation was performed on the diethyl derivative (compound I) and the dibutyl derivative (compound II) using single-crystal and powder X-ray diffraction, DFT (omega B97X-D/6-31G*), DLS, NMR, IR/ATR spectroscopy, UV-vis absorption, fluorescence spectroscopy, HRMS, thermal analysis, QSAR, ADMET, and in vitro cytotoxicity studies. Structural analyses revealed that compound I forms hydrogen-bonded dimers, whereas compound II assembles into cooperative tetramers through complementary P=O & ctdot;H-N (amine) and C=O & ctdot;H-N (amide) interactions. Excellent agreement between experimental and calculated structural parameters validated the proposed supramolecular models. DLS, QSAR, and frontier orbital analyses showed that tetramer formation substantially increases molecular size, anisotropy, accessible surface area, and polarizability. Although compound II exhibits a slightly smaller HOMO-LUMO gap, both compounds remain electronically stable, with the reduced gap reflecting enhanced electronic delocalization rather than increased chemical reactivity. Thermal and ATR studies demonstrated that alkyl chain elongation decreases crystal packing efficiency and promotes hydrogen-bond reorganization without compromising the stability of the phosphonate core. Both compounds exhibited low cytotoxicity (IC50 > 100 mu M), indicating good biological tolerance. While monomer-based ADMET predictions suggest a shift from absorption-favored behavior in compound I to permeability-limited characteristics in compound II, these models do not fully capture the persistence of the experimentally verified tetrameric assembly. Collectively, the results establish alkyl chain length as a supramolecular design parameter governing assembly state, intermolecular interactions, and potential delivery pathways in phosphonate-based systems.
