Hydrophilic polymers, polymer brushes

Recently, core-shell type microgels, which contain a hydrophobic core and a hydrophilic thermosensitive shell, have become attractive for scientists because such systems can combine the properties characteristic of both the core and the shell [53], We have prepared core-shell microgel particles consisting of a poly(styrene) core onto which a shell of polyCA-isopropylacrylamide) (PS-PNIPA) has been affixed in a seeded emulsion polymerization [54-56], In this case, the ends of the crosslinked PNIPA chains are fixed to a solid core, which defines a solid boundary of the network. In this respect, these core-shell latex particles present crosslinked polymer brushes on defined spherical surfaces. The solvent quality can be changed from good solvent conditions at room temperature to poor solvent conditions at a temperature... 

Amphiphilic diblock copolymers act as a surfactant and stabilize free-standing films. They are assumed to adsorb at the interface by analogy with low-molecular-weight surfactants The hydrophobic part is collapsed at the interfaces and the hydrophilic part is directed towards the film core (Fig. 2a). Investigations of the structure at a single liquid interface (air/water) show that the amphiphilic diblock copolymers present polymer brushes which are anchored by the hydrophobic block at the interface [22, 23], This structure is also assumed at the film surfaces. Fig. 3 shows the disjoining pressure iso-... 

The impact of the chemical functionality of grafted polymer brushes on the wettability of the substrate was investigated for a number of neutral polymers as well as for weak and strong polyelectrolytes (Figure 4.2) [2]. It is evident that the wettability of the hydrophobic ETFE substrate can be tailored over a wide range with polymer brushes. As a general trend, surfaces with more hydrophilic brushes... 

A spiropyran derivative with an amine linker was synthesized and coupled to grafted brushes of PGMA and of PMAA activated with perfluorophenyl trifluoroacetate. Exposure of the modified brushes to UV light, which converts the attached moieties from the uncharged transparent spiropyran to the zwitterionic merocyanine form, rendered the brushes deep purple in color, fluorescent, and hydrophilic. The properties switched back by thermal or visible light-induced relaxation. The kinetics of the switching was found to be dependent on the chemical environment provided by the polymer brushes as well as on the polarity of added solvent. 

In the case of strongly asymmetric block copolymers Na Nb), the size of the micellar core, Rears, is much smaller than the radius / corona of the corona. In this case, starlike micelles with spherical cores are formed (Fig. la). In the opposite limit of short hydrophilic block, Na Nb, the size of micellar core. Rears, exceeds by far the thickness of the corona. The coronae of these crew-cut micelles can be viewed as quasi-planar polymer brushes [51, 52], see Fig. lb. 

Savina IN, Galaev lY, Mattiasson B (2006) Ion-exchange macroporous hydrophilic gel monolith with grafted polymer brushes. J Mol Recognit 19 315-321... 

In this work, we wiU discuss the characteristic size-exclusion effect and excellent protein repeUency of concentrated brushes on the basis of our experimental data previously reported with poly(2-hydroxyethyl methacrylate) (PHEMA) brushes. PHEMA is a hydrophilic, biocompatible polymer, but the biocompatibility of PHEMA cast film is reported to be not as good as e.g., poly(2-methacryloxyethyl-phosphorylcholine) and poly(2-metho-xyethylacrylate) cast films. Hence any favorable results on the PHEMA brushes could be ascribed more to the structural,... 

Other sensitive PEMs have been described which respond to different stimuli. Photosensitive multilayers were prepared using polyelectrolytes functionalized with photoisomerizable azobenzene chromophores. Barrett et al. have prepared sensors, the mechanical properties of which change under Hght irradiation [22]. Solvent-responsive polymer brushes have been prepared by anchoring two types of polymers (one hydrophobic and one hydrophilic) on a wafer surface. As a function... 

Lenk, Lee and Koberstein showed that even the surface active polydimethylsiloxane (PDMS) can be transformed into a polymer brush by attaching strongly hydrophilic head groups. Methyl terminated PDMS forms... 

The combination of brushes with soft surfaces is clearly a key aspect of biological lubrication. However, it is less clear whether carbohydrates possess any specific or unique properties that are absent in other, synthetic brush-forming hydrophilic polymer chains. Moreover, natural lubricant additives appear to form hierarchical bottlebrush structures, such as that shown in the figure, more readily than the synthetic water-soluble brushes that have been investigated to date (9, 12, 14). The role of both the composition and struc-... 

We have previously demonstrated that hydrophilic polymer brushes can effectively reduce the interfacial friction in an aqueous environment under low-sliding-speed conditions.In those studies, we employed grafting to approaches to generate polymer brushes on a variety of substrates. By applying the grafting from method described in this work, the formation of high-surface-density polyelectrolyte brushes became feasible. To date, only little experimental work has been dedicated to the macroscopic lubrication properties of polymer brushes prepared with a grafting from method. ... 

To date, no attempt has been made to understand the relationship between the adsorption of biomolecules from the complex synovial fluid and the friction between the surfaces of artificial joint materials on a molecular level. There have, however, been a number of studies on the mechanisms of aqueous lubrication in the presence of synthetic macromolecules. A particularly efficient mechanism of lubrication involves the formation of hydrophilic polymer brushes at the surface, which maintain a fluid film between the opposing surfaces [16,17], The low friction between the surfaces has been attributed to the fluidity of the hydration layers around the polymers and resistance to interpenetration between the polymer brushes [18]. 

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