Tethered polymer phases

Highly branched polymers, polymer adsorption and the mesophases of block copolymers may seem weakly connected subjects. However, in this review we bring out some important common features related to the tethering experienced by the polymer chains in all of these structures. Tethered polymer chains, in our parlance, are chains attached to a point, a line, a surface or an interface by their ends. In this view, one may think of the arms of a star polymer as chains tethered to a point [1], or of polymerized macromonomers as chains tethered to a line [2-4]. Adsorption or grafting of end-functionalized polymers to a surface exemplifies a tethered surface layer [5] (a polymer brush ), whereas block copolymers straddling phase boundaries give rise to chains tethered to an interface [6],... 

Szleifer I, Carignano MA (2000) Tethered polymer layers phase transitions and reduction of protein adsorption. Rapid Commun 21 423 148... 

This method is a combination of the other two methods. In our opinion, it is the most gentle method to reconstitute membrane proteins into supported bilayers and to prepare supported bilayers with fragile coexisting liquid phases of lipids. A LB monolayer is prepared on a hydrophilic substrate as described above. To prepare tethered-polymer supported bilayers, a suitable lipopolymer may be included at a concentration of a few... 

The grafting-from technique involves the immobilization of initiators onto the substrate followed by in situ surface-initiated polymerization to generate a tethered polymeric phase. This approach has generally become the most attractive way to prepare thick, covalently tethered polymer brushes with a high grafting density. A variety of synthesis methods such as radical chain transfer reaction,reverse ATRP, living anionic surface-initiated polymerization, ATRP, " dispersion polymerization, and... 

Fig. 1 Schematic comparison of (a) monolayers of tethered polymers that are free of solvent, (b) monolayers of tethered polymers swollen with solvent, and (c) one lamella of phase separated blockcopol5miers...

A solid-phase synthesis of substituted benzopyranoisoxazoles 356 (I R = H, Me, Et, Pr, Ph, CHMe2 R1 =H, Me, decyl, Ph) has been described (414). The six-step synthesis includes a method of generating nitrile oxides on a polymer support, followed by an intramolecular 1,3-dipolar cycloaddition with a tethered alkyne, for assembly of the benzopyranoisoxazole scaffold. 

Polymer-supported reagents differ from polymer-supported substrates in that the former mediate a reaction rather than becoming an integral part of the product. A major attribute of tethered reagents is that both the reagent and the reagent byproduct can be directly filtered away from solution-phase products. 

Block copolymers consist of chemically distinct polymer chains that are tethered together to form a single macromolecule. If the individual blocks are immiscible when they are unattached, phase separation will also normally occur in the case of the copolymer, with morphologies that depend on the relative composition of the separate block species, and their manner of attachment (diblocks, triblocks, stars, etc.). This is a result of the physical connection of the blocks, which prevents them from separating over distances greater than the contour lengths of the respective blocks. The result is a microphase separation with adjacent domains that are richer in either of the chemical species. 

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