Tethering polymer

Szleifer I and Carignano M A 1996 Tethered polymer layers Adv. Chem. Phys. 94 165... 

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],... 

The rheological properties of insitu polymerized nanocomposites with end-tethered polymer chains were first described by Krisnamoorti and Giannelis [33]. The flow behavior of PCL- and Nylon 6-based nanocomposites differed extremely from that of the corresponding neat matrices, whereas the thermorheological properties of the nanocomposites were entirely determined by the behavior of the matrices [33]. The slope of G (co) and G"(co) versus flxco is much smaller than 2 and 1, respectively. Values of 2 and 1 are expected for linear mono-dispersed polymer melts, and the large deviation, especially in the presence of a very small amount of layered silicate loading, may be due to the formation of a network structure in the molten... 

Currie EPK, Norde W, Cohen Stuart MA (2003) Tethered polymer chains surface chemistry and their impact on colloidal and surface properties. Adv Colloid Interf Sci 100-102, 205-265... 

Salt effects in polyelectrolyte block copolymer micelles are particularly pronounced because the polyelectrolyte chains are closely assembled in the micellar shell [217]. The situation is quite reminiscent of tethered polymer brushes, to which polyelectrolyte block copolymer micelles have been compared, as summarized in the review of Forster [15]. The analogy to polyelectrolyte brushes was investigated by Guenoun in the study of the behavior of a free-standing film drawn from a PtBS-PSSNa-solution [218] and by Hari-haran et al., who studied the absorbed layer thickness of PtBS-PSSNa block copolymers onto latex particles [219,220]. When the salt concentration exceeded a certain limit, a weak decrease in the layer thickness with increasing salt concentration was observed. Similar results have been obtained by Tauer et al. on electrosterically stabilized latex particles [221]. 

The non-aqueous system of spherical micelles of poly(styrene)(PS)-poly-(isoprene)(PI) in decane has been investigated by Farago et al. and Kanaya et al. [298,299]. The data were interpreted in terms of corona brush fluctuations that are described by a differential equation formulated by de Gennes for the breathing mode of tethered polymer chains on a surface [300]. A fair description of S(Q,t) with a minimum number of parameters could be achieved. Kanaya et al. [299] extended the investigation to a concentrated (30%, PI volume fraction) PS-PI micelle system and found a significant slowing down of the relaxation. The latter is explained by a reduction of osmotic compressibihty in the corona due to chain overlap. 

An alternative containment scheme is immobilization of active species on a surface" " or within a tethered polymer brush or network. ° Surface immobilization can achieve high surface utilization by locating mediators and biocatalysts within nanometers of conducting surfaces. Immobilization on polymer networks allows for dense packing of enzymes within electrode volumes at the expense of long-distance electron mediation between the enzyme active center and a conductive surface. Such mediation often represents the rate-limiting step in the overall electrode reaction. 

Fig. 2 Schematic representation of surface-anchored polymers in brush (left) and mushroom (middle) conformations in good solvents. Also shown is the conformation of a surface-tethered polymer under poor solvent conditions (right)...

In many respects gold is more convenient than sihcon for characterizing polymer brush films. For instance, the RAIR spectra from planar gold are usually superior to that from sihcon wafers, especially for the SAM characterization. In addition, the S - Au bond is easily cleaved by treatment in a dilute solution of iodine. This allows for the isolation of the tethered polymer and the determination of Mn and PDI. The SAMs are easily deposited from dilute solutions of thiol or disulfide precursors. The only major disadvantage to gold is the instability of the weak S - Au bond, which is unstable above 60 °C, and imder UV irradiation in air. 

A variety of surface-sensitive spectroscopic and microscopic methods were critical in the investigation of these systems. In the work by Advincula et al, the composition, thickness, physical and thermal properties, and morphology of the tethered polymer brushes were carefully analyzed [72]. A variety of surface-sensitive techniques such as ellipsometry, contact angle measurements, AFM, quartz crystal microbalance (QCM), FT-IR grazing incidence... 

Krishnamoorti R, Giannelis EP (1997) Rheology of end-tethered polymer layered silicate nanocomposites. Macromolecules 30 4097-4102... 

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

Figure 10 Stable (repulsive) versus unstable (attractive) dispersion of tethered chains as a function of the ratio of the polymer chain length to tethered polymer chain length (a).

Willner I, Willner B. Electrical communication of redox proteins by means of electron relay-tethered polymers in photochemical, electrochemical and photoelectrochemical systems. React Polym 1994 22 267-79. 

SURFACE-TETHERED POLYMERS OR OLIGOMERS TO INFLUENCE THE CONFORMATION AND ORIENTATION OF ADSORBED PROTEIN MOLECULES... 

Most of the existing studies focus on brushes exposed to a low molecular weight solvent and less is known of the behavior of surface-tethered polymers in polymeric matrices [6,46-56]. On the experimental side, nuclear reaction analysis [57,58], neutron scattering [59-61], neutron reflectivity [62] and secondary-ion... 

Wagner ML, Tamm LK (2000) Tethered polymer-supported planar lipid bilayers for reconstitution of integral membrane proteins Silane-polyethyleneglycol-lipid as a cushion and covalent linker. Biophys J 79 1400-1414... 

FIG. 1b A magnified view of the spot where the laser beam intercepts the interface in Fig. la. The evanescent wave propagates in the y direction with an amplitude that is attenuated in the /. direction. A tethered polymer chain scatters the evanescent wave. From the properties of the scattered light it is possible to obtain a measure of the spatial distribution of the polymer material at the interface as well as a measure of the dynamical properties of the polymer chains. (From Ref. 9.)... 

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