Shell with Striped, Helical, and Bipolar Lamellae Structures from Soft Confinement-Induced Self-Assembly of AB Diblock Copolymers on a Nanocylinder.

The soft confinement-induced self-assembly of AB diblock copolymers on a nanocylinder is studied via a simulated annealing method. The formation of multiple copolymer shells was predicted by varying the interfacial interaction, the size of confinement, and the height and diameter of the nanocylinder. The competition between solvent repulsion and nanocylinder attraction determined the degree of encapsulation of the copolymer shell. The formation of a helical copolymer shell was induced by the maximization of conformational entropy. The preferential distribution position of copolymers on anisotropic nanocylinder surfaces was induced by interfacial energy minimization. Our study contributes to the understanding of the formation mechanism of the helical structure in block copolymer aggregates and the fabrication of copolymer shells with predesigned morphologies.

The mechanism underlying the transitions between stripes, helices, and stacked toroids in the cylindrical shell formed by AB diblock copolymers on a long nanocylinder.

The self-assembly of block copolymers on nanocylinders has attracted a lot of interest due to its potential application in biomedicine and other fields. In this study, the self-assembly phase behavior of AB diblock copolymers on long nanocylinders in soft confinement has been studied by using a simulated annealing method. A square phase diagram of the morphology was constructed by increasing the number of chains of copolymers (cn) and the cylindrical diameter (D). As a result, morphological transitions from striped to helical and axially stacked toroids, as well as reversible transitions, started to appear. By analyzing the chain packing in a fan-shaped region and calculating the mean-square end-to-end distance (DEE2) of the copolymers and number of AB contacts, both types of transitions were found to be driven by the competition between conformational entropy and AB interfacial energy. The number of stripes increased and the helical angle decreased with the increase in cylinder diameter. The chirality of the helix was found to be random.

Inactivation kinetics and cell envelope damages of foodborne pathogens Listeria monocytogenes and Salmonella Enteritidis treated with cold plasma.

In recent years, more attention has been paid to the application of cold plasma (CP) in eliminating foodborne pathogenic bacteria. This work investigated CP effects on inactivation kinetics and cell envelopes of Listeria monocytogenes (L. monocytogenes) and Salmonella Enteritidis (S. Enteritidis). Bacterial suspensions were treated with dielectric barrier discharge atmospheric CP at 75 kV for different treatment time. Three regression models were tested for estimating inactivation kinetics. Reactive species generated in plasma, the appearance and integrity of bacterial cells, the activity and secondary structure of enzymes in the cell envelope, and molecular docking, were measured for evaluating the envelope damages. Results indicated that Log-linear model was suitable for L. monocytogenes and the Weibull model was suitable for S. Enteritidis. S. Enteritidis was more sensitive to short-lived reactive species (such as OH radicals) in plasma than L. monocytogenes, and the cell envelope of S. Enteritidis was more severely damaged (the increased membrane permeability and leakage of intracellular substances) after plasma treatment. Interestingly, compared with S. Enteritidis, the decrease in the activity of enzymes existing in the cell envelope of L. monocytogenes did not contribute significantly to the death of bacteria. Molecular docking further suggested that the decrease in the enzyme activity might be due to the modification of the enzyme, by the interaction between reactive species in plasma (H2O2) and amino acid residues of the enzyme through the hydrogen bond.

Core-shell particle formation via Co-assembly of AB diblock copolymers and nanoparticles in 3D soft confinement.

Core-shell particle formation via co-assembly of AB diblock copolymers and nanoparticles in 3D soft confinement was studied using a simulated annealing method. Several sequences of soft confinement-induced core-shell particles were predicted as functions of the volume fraction of the nanoparticle to core-shell particles, the incompatibility between blocks, the volume fractions of A-blocks, the chain length of AB diblocks, the eccentricity of the nanoparticle, and the initial concentration of copolymers. Simulation results demonstrate that those factors are able to tune the morphology of the core-shell particles precisely. Calculated data indicate that the copolymer chain was located between a hard confinement wall composed of the nanoparticle and a soft confinement wall composed of solvents, and the arrangement direction of the copolymer chains was in a competitive equilibrium between the two. We anticipate that this work will be helpful and instructive for the preparation of polymer shells with different structures and shapes, as well as the study of self-assembly morphology of copolymers in a complex confinement systems.