Silylation reactions using liquid and supercritical CO2 as the solvent were performed on both single surface (silicon wafers) and nanoporous (silica gel) silica samples. The alkylsilyl monolayers formed on single surfaces were characterized by wettability, ellipsometry, and X-ray photoelectron spectroscopy. Modified nanoporous silica samples were analyzed by chemical analysis. A range of different silanes including monochloro-, dichloro-, trichloro-, and dimethylamino-silanes was examined. The results indicate that dense carbon dioxide is a good solvent for silylation reactions, comparable or better than most solvents. Compared with the optimum conditions for silylation at solid-liquid interfaces, reactions in carbon dioxide are faster, although maximum bonding densities are slightly lower.

SYNOPSISSilicone rubber particles with core-shell structure were prepared by polymerization of vinyl monomers in the presence of crosslinked and linear poly(dimethy1 siloxane-methyl vinyl siloxane) latex. The monomers were added with either continuous or swelled-continuous addition mode. The core-shell morphology of silicone rubber/polystyrene [PST] and silicone rubber/poly(methyl methacrylate-divinyl benzene) [P(MMA-DVB)] composite particles were obtained. The effects of monomer addition mode, the compatibilities of the monomers or their homopolymer with silicone rubber, and the reactivity of polysiloxane with vinyl monomers on the formation of the core-shell structure were discussed. 0 1996 John Wiley & Sons, Inc. I NTRO DU CTI 0 NSince core-shell particles have plenty of applications, such as the toughening and strengthening of plastics,'-3 preparation of core-shell particles by seeded emulsion polymerization has been attracting great interest among researchers. Thus, a tremendous progress in this field has been achieved.The factors influencing the formation of coreshell particles have been extensively studied. The crucial factor is thermodynamics, which determines the formation of the core-shell or inverted coreshell s t r~c t u r e .~ Kinetic factors, such as diffusion re~triction,~ seeded emulsion polymerization rate6 and addition mode of monomers: are very important in the morphology formation of the obtained particles. However, most of the researches concentrated on the poly(meth)acrylate systems.In our previous work, we reported the preparation of the core-shell particles of silicone rubber/PMMA and silicone rubber/PGMA using one-stage method? The compatibility of vinyl monomer with silicone rubber and the reaction rate between vinyl monomers and Si-H of silicone oils affected greatly the morphology and the content of vinyl polymers in the surface layer of the obtained particles.

Drug-resistant bacterial infections have caused serious threats to human health and call for effective antibacterial agents that have low propensity to induce antimicrobial resistance. Host defense peptide–mimicking peptides are actively explored, among which poly-β- l -lysine displays potent antibacterial activity but high cytotoxicity due to the helical structure and strong membrane disruption effect. Here, we report an effective strategy to optimize antimicrobial peptides by switching membrane disrupting to membrane penetrating and intracellular targeting by breaking the helical structure using racemic residues. Introducing β-homo-glycine into poly-β-lysine effectively reduces the toxicity of resulting poly-β-peptides and affords the optimal poly-β-peptide, βLys 50 HG 50 , which shows potent antibacterial activity against clinically isolated methicillin-resistant Staphylococcus aureus (MRSA) and MRSA persister cells, excellent biosafety, no antimicrobial resistance, and strong therapeutic potential in both local and systemic MRSA infections. The optimal poly-β-peptide demonstrates strong therapeutic potential and implies the success of our approach as a generalizable strategy in designing promising antibacterial polypeptides.

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