Covalent Crosslinks (covalent + crosslink)

Distribution by Scientific Domains


Selected Abstracts


Dynamically Restructuring Hydrogel Networks Formed with Reversible Covalent Crosslinks,

ADVANCED MATERIALS, Issue 18 2007
C. Roberts
Dynamically restructuring hydrogel networks are formed from two water-soluble polymers by functionalization with phenylboronic acid (PBA) and salicylhydroxamic acid (SHA) moieties that interact through pH-sensitive and reversible covalent crosslinks (see figure). The networks can be tuned to display a wide range of pH-responsive properties, which can potentially be exploited for drug delivery systems in biological environments where similar acidic changes occur. [source]


Modulation of Viscoelasticity and HIV Transport as a Function of pH in a Reversibly Crosslinked Hydrogel

ADVANCED FUNCTIONAL MATERIALS, Issue 18 2009
Julie I. Jay
Abstract Materials that respond to physiological stimuli are important in developing advanced biomaterials for modern therapies. The reversibility of covalent crosslinks formed by phenylboronate (PBA) and salicylhydroxamate (SHA) has been exploited to provide a pH-responsive gel for application to the vaginal tract. Dynamic rheology reveals that the gel frequency-dependent viscoelastic properties are modulated by pH. At pH 4.8 the viscous component dominates throughout most of the frequency range. As the pH increases, the characteristic relaxation time continues to increase while the G,Plateau levels off above pH 6. At pH 7.5, the elastic component dominates throughout the frequency sweep and is predominately independent of frequency. Particle tracking assesses the transport of both fluorescently labeled HIV-1 and 100-nm latex particles in the PBA,SHA crosslinked gel as a function of pH. At pH 4.8 the ensemble-averaged mean squared displacement at lag times greater than three seconds reveals that transport of the HIV-1 and 100-nm particles becomes significantly impeded by the matrix, exhibiting diffusion coefficients less than 0.0002,Ám2 s,1. This pH-responsive gel thus displays properties that have the potential to significantly reduce the transport of HIV-1 to susceptible tissues and thus prevent the first stage of male-to-female transmission of HIV-1. [source]


One-Step Process for Creating Triple-Shape Capability of AB Polymer Networks

ADVANCED FUNCTIONAL MATERIALS, Issue 1 2009
Marc Behl
Abstract Triple-shape polymers can move from a first shape (A) to a second shape (B) and from there to a third shape (C), where both shape changes are induced by temperature increases. This triple-shape capability is obtained for multiphase polymer networks after application of a complex thermomechanical programming process, which consists of two steps; these steps create shapes (B) and (A), while shape (C) is defined by the covalent crosslinks of the polymer network. Here, the creation of the triple-shape capability for an AB polymer network system by a simple one-step process similar to a conventional dual-shape programming process is reported. The polymer networks are based on poly(, -caprolactone) (PCL) and poly(cyclohexyl methacrylate); favorable compositions for obtaining a triple shape effect have a PCL content between 35 and 60 wt%. This finding substantially facilitates handling of the triple-shape technology and is an important step toward the realization of potential applications in which more than one shape change is required. [source]


Dynamically Restructuring Hydrogel Networks Formed with Reversible Covalent Crosslinks,

ADVANCED MATERIALS, Issue 18 2007
C. Roberts
Dynamically restructuring hydrogel networks are formed from two water-soluble polymers by functionalization with phenylboronic acid (PBA) and salicylhydroxamic acid (SHA) moieties that interact through pH-sensitive and reversible covalent crosslinks (see figure). The networks can be tuned to display a wide range of pH-responsive properties, which can potentially be exploited for drug delivery systems in biological environments where similar acidic changes occur. [source]


Effects of Transglutaminase on SDS-PAGE Patterns of Wheat, Soy, and Barley Proteins and their Blends

JOURNAL OF FOOD SCIENCE, Issue 7 2002
A. Basman
ABSTRACT: Transglutaminase (TG) catalyzes the formation of nondisulfide covalent crosslinks between pep-tide-bound glutaminyl residues and ,-amino groups of lysine residues in proteins. TG can be used for polymerizing proteins from 1 or more sources through formation of intermolecular crosslinks. This study investigated, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, polymers created by the action of TG on proteins of wheat, soy, barley, wheat-soy, and wheat-barley blends. Electrophoretic results showed that with increasing incubation time, the crosslinking reaction is substantially increased, with progressive decrease or disappearance of some protein monomers. Densitometric results showed that soy proteins were the best substrates of TG while barley and wheat proteins were similar in reactivity. [source]


Surface Grafting of PEO-Based Star-Shaped Molecules for Bioanalytical and Biomedical Applications

MACROMOLECULAR BIOSCIENCE, Issue 8 2007
Peter Gasteier
Abstract This article reviews surface grafting of star-shaped PEO. The use of star-shaped polymers is compared to linear PEO chains regarding the layer preparation and the ability of the resulting surfaces to resist protein adsorption. We then focus on the use of end-functionalized, star-shaped, PEO-based prepolymers that are able to form covalent crosslinks and functional polymer networks on the substrate. Examples are given for specific protein adsorption as well as for cell adhesion on such layers by covalent embedding of biofunctional molecules. The possibility of coating biomedically relevant polymer substrates in three-dimensional geometries is discussed and examples are shown for poly(ethylene terephthalate) monofilament constructs. [source]