Search results for "Amphiphile"
showing 10 items of 270 documents
Novel Amphiphilic Styrene-Based Block Copolymers for Induced Surface Reconstruction
2008
This paper describes the synthesis of amphiphilic block copolymers by living radical polymerization (NMP) of new styrene-like monomers. The polar monomers (ethylene oxide side chains and free hydroxyl- or amino-groups after deprotection) were polymerized in a “protected form” to adjust the solubility of the monomers. In this way high molar mass polymers with a narrow polydispersity (around or below 1.2) were accessible. In the bulk state hydrophobic and hydrophilic domains demix. By exposing thin films of these polymers to vacuum (air) or alternatively to water or a hydrophilic surface it becomes possible to switch the surface polarity reversibly between contact angles of about 105° and 83°…
Amphiphilic poly(ether urethanes) carrying associative terpyridine side groups with controlled spacing
2021
The rational design of transiently crosslinked polymer gels requires a profound understanding of how molecular and topological factors determine the mechanical and dynamic material properties. To refine so-far established structure–property relations, complementary and versatile model sytems are still a crucial prerequisiste. In this study, the synthesis of a metallo-supramolecular associating terpyridine-diol (referred to as sticker) and its incorporation into poly(ethylene glycol) (pEG) based polyurethanes (PU) with strictly alternating vs. random sequences and variable sticker spacings is described. Synergetic effects resulting from the proximity of multiple neighboring urethane and stic…
Synthesis, Characterization and Preliminary Biological Evaluation of P(HPMA)-b-P(LLA) Copolymers: A New Type of Functional Biocompatible Block Copoly…
2010
We describe a synthetic pathway to functional P(HPMA)-b-P(LLA) block copolymers. The synthesis relies on a combination of ring-opening polymerization of L-lactide, conversion into a chain transfer agent (CTA) for the RAFT polymerization of pentafluorophenyl methacrylate. A series of block copolymers was prepared that exhibited molecular weights $\overline M _{\rm n}$ ranging from 7 600 to 34 300 g · mol(-1) , with moderate PDI between 1.3 and 1.45. These reactive precursor polymers have been transformed into biocompatible P(HPMA)-b-P(LLA) copolymers and their fluorescently labeled derivatives by facile replacement of the pentafluorophenyl groups. The fluorescence label attached to this new …
Industrial applications of the aggregation of block copolymers in supercritical CO 2 : a SANS study
2002
Industrial applications of supercritical carbon dioxide (scCO2) rely upon the rather selective and easily adjustable solvent ability of CO2. CO2 near the critical point is a poor solvent for high molecular weight (HMW) hydrocarbon polymers, while it is a very good solvent for amorphous fluorinated polymers. By increasing the pressure, CO2 becomes a good solvent even for HMW hydrogenated chains. Specially engineered amphiphilic di-block copolymers, with CO2-philic and CO2-phobic portions, are expected to undergo trough a monomer–aggregate transition when the solvent density of the scCO2 changes. Here small-angle neutron scattering (SANS) results are reported for a block copolymer dissolved i…
Self-assembly concepts for multicompartment nanostructures.
2015
Compartmentalization is ubiquitous to many biological and artificial systems, be it for the separate storage of incompatible matter or to isolate transport processes. Advancements in the synthesis of sequential block copolymers offer a variety of tools to replicate natural design principles with tailor-made soft matter for the precise spatial separation of functionalities on multiple length scales. Here, we review recent trends in the self-assembly of amphiphilic block copolymers to multicompartment nanostructures (MCNs) under (semi-)dilute conditions, with special emphasis on ABC triblock terpolymers. The intrinsic immiscibility of connected blocks induces short-range repulsion into discre…
Production of Dicarboxylic Acids and Flagrances by Yarrowia lipolytica
2013
Yeasts are excellent biocatalysts in the field of alkane and fatty acids transformation into dicarboxylic acids and lactones. Their ability to produce some diacids through simple, less expensive and more environment friendly routes than chemical pathways and to produce particular diacids (e.g. unsaturated ones) but also to transform natural substrates into lactones with a natural label has made them the subject of many researches. Although Candida species were often first studied, the development of genetic tools, the knowledge of the genome and some genomic and biotechnological particularities of Yarrowia lipolytica resulted to interesting developments with this species. This chapter aims …
Load-collapse-release cascades of amphiphilic guest molecules in charged dendronized polymers through spatial separation of noncovalent forces.
2012
The ability to pack guest molecules into charged dendronized polymers (denpols) and the possibility to release these guest molecules from subsequently densely aggregated denpols in a load-collapse-release cascade is described. Charged denpols, which constitute molecular objects with a persistent, well-defined envelope and interior, are capable of incorporating large amounts of amphiphilic guest molecules. Simultaneously, multivalent ions can coordinate to the surfaces of charged denpols, leading to counterion-induced aggregation of the already guest-loaded host structures. Thus, although the local guest concentration in denpol-based molecular transport might already be initially high due to…
Polymeric gegenions induced variability and mobility of amphiphilic supramolecular structures on solid substrates
1992
Abstract The micromorphological variations of amphiphilic L -glutamate derivatives at air-substrate interfaces due to an adjacent mobile polymer matrix have been investigated via fluorescence microscopy. Adjusted monolayers of the L -glutamate derivatives have been transferred by LB technique out of different aggregation states onto various substrates. The substrates have been prepared by successive polymer preadsorption to the solid support. The influence of the adjacent polymer layers on the domain morphology as a function of water content and temperature has been examined intensively. Moreover, reversible domain changes induced by temperature variation of the transferred films have been …
Linear-dendritic nonionic poly(propylene oxide)–polyglycerol surfactants
2003
Abstract A new type of linear-hyperbranched surfactant has been prepared by anionic ring-opening multibranching polymerization of glycidol onto an end-functional poly(propylene oxide) (PPO) macroinitiator. A hyperbranched, highly hydrophilic polyglycerol block is obtained as the polar segment of the structure. Molecular weights of the nonionic amphiphiles obtained were in the range of 390 to 8,600 g/mol. For comparison, initiators bearing a C16 alkyl chain have also been employed. Furthermore, hyperbranched polyglycerol homopolymers were investigated with respect to amphiphilic properties. All linear-dendritic amphiphiles have been characterized by SEC, DSC, 13 C and 1 H NMR spectroscopy. A…
Self-organization of substituted azacrowns based on their discoid and amphiphilic nature
1989
Abstract Cyclame and hexacyclene derivatives, bearing four and six long-chain substituents respectively, were synthesized. They are discussed as monolayer-forming amphiphiles as well as liquid-crystalline-phase-forming thermotropic mesogens. The compounds investigated form ordered monolayers at the gas/water interface. In the monolayer the hydrophilic cyclic head group lies flat on the water surface, whereas the hydrophobic substituents are oriented perpendicularly with respect to the interface. Most derivatives fitted with aromatic substituents exhibit a solid condensed state exclusively. In contrast with this, solid condensed as well as expanded phases can be found when spreading the alip…