Graft polymer | EPFL Graph Search

In polymer chemistry, graft polymers are segmented copolymers with a linear backbone of one composite and randomly distributed branches of another composite. The picture labeled "graft polymer" shows how grafted chains of species B are covalently bonded to polymer species A. Although the side chains are structurally distinct from the main chain, the individual grafted chains may be homopolymers or copolymers. Graft polymers have been synthesized for many decades and are especially used as impact resistant materials, thermoplastic elastomers, compatibilizers, or emulsifiers for the preparation of stable blends or alloys. One of the better-known examples of a graft polymer is a component used in high impact polystyrene, consisting of a polystyrene backbone with polybutadiene grafted chains. General properties Graft copolymers are a branched copolymer where the components of the side chain are structurally different than that of the main chain. Graft copolymers containing

Surface modification of PES virus filtration membrane

Claire Roulin

Virus filtration by size exclusion is a robust means of eliminating viruses in blood or pharma products. Porous polymer membranes with a narrow size distribution are used to allow passage of the protein product but retain viruses. The chosen polymer must resist process-induced physical and chemical wear and is therefore generally inert and hydrophobic material. When filtrating potentially heterogeneous products such as IgG from pooled blood samples, protein adsorption on the polymer surface causes high fouling. This eventually blocks the filter and reduces total filtration volume. A solution to this adsorption problem is to graft a hydrophilic gel-like polymer layer on the membrane inner surface to reduce protein adsorption. The surface properties are thus changed while retaining the stability of the bulk polymer. The grafting was initiated with an electron beam, which creates free radicals by unspecific scission of the polymer backbone through electron irradiation. Two acrylate monomers were used for polymerization, a monofunctional monomer and a bifunctional one, used as a crosslinker to form the gel structure. Two different grafting method were tested. The first grafting method is simultaneous grafting, where the membrane is impregnated with the monomer solution then irradiated. Initiation and polymerization thus occur almost simultaneously. The grafted membrane properties were assessed using flow measurements, protein adsorption tests, FTIR absorbance measurements, virus retention tests and filter integrity tests. Comparing the various grafting approaches, it can be seen that simultaneous grafting lowers considerably protein adsorption, to the price of a highly reduced buffer flow. These filters therefore run slowly but can process more volume before fouling. The sequential grafting method using peroxides as initiators did not show significant filtration improvements compared to the reference membrane when the solution with monomer and crosslinker was used. However, when only monofunctional monomer was used for peroxidation grafting, the protein filtration capacity was increased with limited buffer flow loss. Generally, the sequential method is interesting for graft polymerization of porous membranes because it allows higher degree of grafting and the versatile grafting parameters involved give many development options depending on the application

2010

A toolbox of oligopeptide-modified polymers for tailored elastomers

Emmanuel Croisier, Joël Cugnoni, Holger Frauenrath, Su Liang, Véronique Michaud, Marijana Mionic Ebersold, Thomas Schweizer, Ruben Anton Snellings

Biomaterials are constructed from limited sets of building blocks but exhibit extraordinary and versatile properties, because hierarchical structure formation lets them employ identical supramolecular motifs for different purposes. Here we exert a similar degree of structural control in synthetic supramolecular elastomers and thus tailor them for a broad range of thermomechanical properties. We show that oligopeptide-terminated polymers selectively self-assemble into small aggregates or nanofibrils, depending on the length of the oligopeptides. This process is self-sorting if differently long oligopeptides are combined so that different nanostructures coexist in bulk mixtures. Blends of polymers with oligopeptides matching in length furnish reinforced elastomers that exhibit shear moduli one order of magnitude higher than the parent polymers. By contrast, novel interpenetrating supramolecular networks that display excellent vibration damping properties are obtained from blends comprising non-matching oligopeptides or unmodified polymers. Hence, blends of oligopeptide-modified polymers constitute a toolbox for tailored elastomers with versatile properties.

Nature Publishing Group2014

Surface modification of PES virus filtration membrane

Claire Roulin

2010