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To address the challenge from microbial resistance and biofilm, this work develops three gemini peptide amphiphiles with basic tetrapeptide spacers 12-(Arg)4-12, 12-(Lys)4-12, and 12-(His)4-12 and finds that they exhibit varied antimicrobial/antibiofilm activities. 12-(Arg)4-12 shows the best performance, possessing the broad-spectrum antimicrobial activity and excellent antibiofilm capacity. The antimicrobial and antibiofilm activities strongly depend on the membrane permeation and self-assembling structure of these peptide amphiphiles. Gemini peptide amphiphile with highly polar arginine as the spacer, 12-(Arg)4-12, self-assembles into short rods that are prone to dissociate into monomers for permeating and lysing membrane , leading to its broad-spectrum antimicrobial activity and high efficiency in eradicating biofilm. Long rods formed by relatively weaker polar 12-(Lys)4-12 are less prone to disassemble into monomers for further membrane permeation, which makes it selectively kill more negatively charged bacteria and endow it medium antibiofilm activity. Low polar 12-(His)4-12 aggregates into long fibers, which are very difficult to dissociate and they mainly electrostatically bind on the negative microbial surface, resulting in its weakest antimicrobial and antibiofilm activity. This study reveals the effect of the antimicrobial peptide structure and aggregation on the antimicrobial activities and would be helpful for developing high-efficient antimicrobial peptides with antibiofilm activity.

A coating with programmable multifunctionality based on application requirements is desirable. However, it is still a challenge to prepare a hard and flexible coating with a quick self-healing ability. Here, a hard but reversible Si–O–Si network enabled by aminopropyl-functionalized poly­(silsesquioxane) and triethylamine (TEA) was developed. On the basis of this Si–O–Si network, basic coatings with excellent transparency, hardness, flexibility, and quick self-healing properties can be prepared by filling soft polymeric micelles into hard poly­(silsesquioxane) networks. The highly cross-linked continuous network endows the coating with a hardness (H = 0.83 GPa) higher than those of most polymers (H < 0.3 GPa), while the uniformly dispersed micelles decrease the Young’s modulus (E = 5.89 GPa) to a value as low as that of common plastics, resulting in excellent hardness and flexibility, with an H/E of 14.1% and an elastic recovery rate (W e) of 86.3%. Scratches (∼50 μm) on the coating can be healed within 4 min. The hybrid composition of poly­(silsesquioxane) networks also shows great advantages in integration with other functional components to realize programmable multifunctionality without diminishing the basic properties. This nanocomposite design provides a route toward the preparation of materials with excellent comprehensive functions without trade-offs between these properties.

We studied the self-assembly of polydisperse diblock copolymers under various confined states by Monte Carlo simulation. When the copolymers were confined within two parallel walls, it was found that the ordered strip structures appeared alternately with the increase in wall width. Moreover, the wall width at which the ordered structure appeared tended to increase with an increase in the polydispersity index (PDI). On the other hand, the simulation results showed that the copolymers were likely to form ordered concentric strip structures when they were confined within a circle wall. An increase in the PDI led to a change in structure from an ordered concentric strip structure to a newly ordered concentric strip structure. It is interesting to note that one strip was lost while the center was replaced by the other component as the PDI increased. Similar results were obtained in the case of three dimensions. That is, the copolymers were confined in a spherical or cylindrical space. Further along, one layer was lost, and the core was occupied by the other component with the increase in the PDI. We illustrated these phenomena in terms of the frustration between the bulk lamellar repeat period and the confined spacing.

Vesicles formed by ABCA tetrablock copolymers in solvents that are selective for block A are studied using the Monte Carlo simulation. Simulation results show that the chain length ratio and hydrophobicity of blocks B and C are key factors determining the hydrophobic layer structure of the vesicles. If the B and C blocks are of the same hydrophobicity, the longer block C tends to form the closed hydrophobic layer, whereas the shorter block B is located on the outer surface of the closed hydrophobic layer. However, if the hydrophobicity difference between blocks B and C is high enough, the reverse will occur given that block B has a higher hydrophobicity and block C has a lower hydrophobicity. The kinetics of vesicle formation is also studied. Simulation results reveal that the hydrophobic layer structure is formed through the migration of the polymer chain within the vesicle membrane after the formation of the vesicle profile. This migration is independent of the differences in chain length ratio and the hydrophobicity between the blocks B and C. The packing mode and the migration of polymer chains within the vesicle membrane are also presented and discussed.

Using Monte Carlo simulation, we studied the vesicle formation and microphase behavior of ABC triblock copolymers in selective solvent for A and C blocks. Simulation results show that the hydrophilicity of Blocks A and C determines not only the vesicle formation but also the microphase behavior. If Blocks A and C are of equal length, then Block A (with lower hydrophilicity) is likely to aggregate on the inner surface, whereas Block C (with higher hydrophilicity) tends to move to the outer surface, forming the ABC (from inside to outside) three-layer vesicle. Simulation results reveal that if the hydrophilicity difference between the two blocks is sufficiently low, then the ABC three layers are formed after the membrane closes (i.e., after the formation of vesicle profile). Otherwise, the ABC three layers are formed before the membrane closes. Furthermore, the effect of chain length and incompatibility between the two amphiphilic blocks (i.e., A and C) is studied and discussed in this article. The shorter block A is much more likely to aggregate on the inner surface, and the incompatibility between A and C must be sufficiently strong to ensure that the ABC copolymer forms an ABC (from inside to outside) three-layer vesicle.

A systematic study is conducted to reveal how far the polymeric vesicle wall can embed gold nanoparticles (AuNPs) with different sizes by combining experiments and self-consistent field simulations. Both the experimental and simulative results indicate that the location of AuNPs in vesicle wall or in spherical micelle is heavily size dependent. Whether the AuNPs enter the vesicle wall or not is determined by a ratio of the diameter of AuNPs (D0) to the thickness of the vesicle wall (d(w0)). The 1-dodecanethiol-coated AuNPs (Au(x)R) with D0/d(w0) < 0.3 will stably disperse in the vesicle walls. For polystyrene-coated AuNPs (Au(x)S), a criterion of D0/d(w0) is proposed based on the phase diagram; i.e., the Au(x)S with D0/d(w0) < 0.5 can be located in the vesicle wall. Otherwise, the Au(x)R and the Au(x)S prefer to locate in spherical micelles. Moreover, the contributions of enthalpy and entropy to the total free energy of the system are respectively calculated to reveal the mechanism of the size selective distribution of AuNPs. The results demonstrate that the escape of AuNPs from vesicle walls and their selective distribution in spherical micelles is an entropy-driven process. Our study provides an important guideline for fabricating nanoparticle/block copolymer hybrid vesicles in dilute solution.

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