Protecting patches in colloidal synthesis of Au semishells.

Protecting groups are commonly applied in multi-step molecular syntheses to protect one or multiple functional groups from reacting. After the reaction, they are removed from the molecule. In full analogy to this concept, we report the practical and scalable colloidal synthesis of Au semishells using polyphenylsiloxane protecting patches to prevent part of the surface of polystyrene nanoparticles from being covered with Au. After Au deposition, the patches are removed yielding Au semishells. We anticipate that this strategy can be extended to the synthesis of other types of non-centrosymmetric nanoparticles.

Synthesis of Polystyrene⁻Polyphenylsiloxane Janus Particles through Colloidal Assembly with Unexpected High Selectivity: Mechanistic Insights and Their Application in the Design of Polystyrene Particles with Multiple Polyphenylsiloxane Patches.

Janus particles are of great research interest because of their reduced symmetry, which provides them with unique physical and chemical properties. Such particles can be prepared from spherical structures through colloidal assembly. Whilst colloidal assembly has the potential to be a low cost and scalable process, it typically lacks selectivity. As a consequence, it results in a complex mixture of particles of different architectures, which is tedious to purify. Very recently, we reported the colloidal synthesis of Au semishells, making use of polystyrene⁻polyphenylsiloxane Janus particles as an intermediate product (Chem. Commun. 2017, 53, 3898⁻3901). Here, we demonstrate that these Janus particles are realized through colloidal assembly of spherical glucose-functionalized polystyrene particles and an emulsion of phenyltrimethoxysilane in aqueous ammonia, followed by interfacial polycondensation to form the polyphenylsiloxane patch. Both the polystyrene spheres and the emulsion of Ph-TMS in aqueous ammonia are stabilized by a surfmer-a reactive surfactant. The colloidal assembly reported in this manuscript proceeds with an unexpected high selectivity, which makes this process exceptionally interesting for the synthesis of Janus particles. Furthermore, we report insights into the details of the mechanism of formation of these Janus particles, and apply those to adapt the synthesis conditions to produce polystyrene particles selectively decorated with multiple polyphenylsiloxane patches, e.g., raspberry particles.

Synthesis and characterization of amphiphilic monodisperse compounds and poly(ethylene imine)s: influence of their microstructures on the antimicrobial properties.

Amphiphilic monodisperse compounds (series B-I and B-II) and poly(ethylene imine)s (PEI-I, PEI-II, and PEI-III) with different microstructures were prepared from primary amines or poly(ethylene imine) with functional carbonates bearing cationic, hydrophobic, or amphiphilic groups. Their inhibition potential against proliferation of E. coli , S. aureus , and B. subtilis was investigated and their hemolytic activities were determined. The influence of the microstructures, the alkyl chain length and the distribution of cationic and hydrophobic groups, on their antimicrobial efficacy was studied. Amphiphilic compounds with long alkyl chains (C14-C18) directly linked to the cationic groups (series B-I) are more effective against both Gram-positive and Gram-negative bacteria than amphiphilic compounds in which the hydrophobic and cationic groups (series B-II) are connected by a spacer. Poly(ethylene imine)s with amphiphilic grafts (B-I) called PEI-II are more effective than amphiphilic PEIs with the same alkyl chain but with randomly linked cationic and hydrophobic graft called PEI-I or with the amphiphilic grafts (B-II) called PEI-III. The influence of the inoculum size on the MIC value was investigated exemplarily with compounds of series B-I against S. aureus .

Poly(ether-ester) conjugates with enhanced degradation.

When a linear or a four arm star-shaped polyglycidol is used as macroinitiator, densely grafted poly(glycidol-graft-epsilon-caprolactone) and poly(glycidol-graft-L-lactide) and loosely grafted poly[(glycidol-graft-epsilon-caprolactone)-co-glycidol] copolymers have been synthesized by chemical or, in the latter case, by enzymatic catalyzed ring-opening polymerization of epsilon-caprolactone and L-lactide. The well-defined copolymers possess similar molecular weights, but differ in their architecture, microstructure and chemical composition. The hydrolytic degradation behavior was studied in a phosphate buffer solution at pH 7.4 and 37 degrees C for up to 90 days. After different time periods, the mass loss was determined and the degraded copolymers were analyzed by means of NMR, size exclusion chromatography, and scanning electron microscopy. Compared to linear poly(epsilon-caprolactone), poly[(glycidol-graft-epsilon-caprolactone)-co-glycidol] shows a change of the degradation mechanism and a tremendous enhancement of polymer degradation. As this effect is attributed to the high concentration of hydroxy groups at the polyglycidol backbone, this work points out a new possibility to tailor the degradation profiles of polyesters by the introduction of functionality into the polymeric material.

From multifunctionalized poly(ethylene imine)s toward antimicrobial coatings.

Primary amine groups of branched poly(ethylene imine) (PEI) were functionalized with quaternary ammonium groups, alkyl chains of different length, allylic and benzylic groups in a one-step reaction, using a carbonate coupler. The structure of the obtained amphiphilic polymers was determined by means of 1H and 13C NMR spectroscopy. Depending on their hydrophilic/hydrophobic balance, the obtained polymers can be used as water-soluble disinfectants and for antimicrobial coating materials. The bactericidal properties of some of the amphiphilic polymers against Gram-negative and Gram-positive bacteria were investigated. Minimal inhibitory concentrations (log 4 reduction of bacterial growth) against Escherichia coli and Bacillus subtilis were determined in the range of 0.3-0.4 mg/mL and 0.03-0.04 mg/mL for water-soluble polymers. Glass slides coated with functionalized PEIs showed a reduction of colony forming units of at least 95%, at best 99.9%, against E. coli and B. subtilis.