Modification of Surfaces

The dynamics of polymers at surfaces can be studied via dynamic light scattering (DLS), as described in Section IV-3C. A modification of surface DLS using an evanescent wave to probe the solution in a region near the interface has... 

Speciali2ed copolymer latices, which are inherently and permanently tacky, are available as pressure-sensitive emulsions. They are mechanically stable and have excellent machinabiUty. They are compatible with many other PVAc latices and, therefore, can be easily blended with other resins for modification of surface tack, peel strength, and creep. 

Ion Bombardment Modification of Surfaces (O. Auciello and R. Kelly, eds.) Elsevier, Amsterdam, 1984. 

Broadening of the optimal pH range for reactive dye biosorption by chemical modification of surface functional groups of Corynebacterium glutamicum biomass... 

Tari, G., Bobos, I., Gomes, C. and Ferreira, J. (1999) Modification of surface charge properties during kaolinate to halloysite-7A transformation. Journal of Colloid and Interface Science, 210, 360. 

S. Lefrant, I. Baltog, M. Baibarac, J. Schreiber, and O. Chauver, Modification of surface-enhanced Raman scattering spectra of single-walled carbon nanotubes as a function of nanotube film thickness. Phys. Rev. B 65, 235401.1- 235401.9 (2002). 

Although the mechanism by which modification of surfaces in UHV occurs is not clear for all cases, local heating effects appear to have effected the observed modification of glassy materials such as Pd81Si19 (81) and Rl Zr- j (82). The fluence of electrons from an STM tip has been used to accomplish nanometer scale electron beam lithography of CaF2 coated substrates (83). A somewhat different... 

Modifications of Surface Reactivity by Structured Overlayers on Metals... 

The properties of the hybrid diblock structures can be altered drastically by simply taking advantage of the high terminal functionality of the dendritic block. For example unusual diblock structures useful for the modification of surfaces have been prepared by ATRP of polystyrene (PS) initiated from the benzylic halide focal point of Frechet-type dendrons with terminal isophthalate ester groups [9b], Well-defined copolymers with narrow molecular weight distributions were obtained and excellent agreement was observed between calculated... 

Modifications of surface layers due to lattice substitution or adsorption of other ions present in solution may change the course of the reactions taking place at the solid/liquid interface even though the uptake may be undetectable by normal solution analytical techniques. Thus it has been shown by electrophoretic mobility measurements, (f>,7) that suspension of synthetic HAP in a solution saturated with respect to calcite displaces the isoelectric point almost 3 pH units to the value (pH = 10) found for calcite crystallites. In practice, therefore, the presence of "inert" ions may markedly influence the behavior of precipitated minerals with respect to their rates of crystallization, adsorption of foreign ions, and electrokinetic properties. 

Solid surfaces nature of the surface of colloidal silica, clays, zeolites, silica gels, porous Vycor glasses, alumina rigidity, polarity and modification of surfaces... 

In addition to modification of surfaces by non-metals, the catalytic properties of metals can also be altered greatly by the addition of a second transition metaP ". Interest in bimetallic catalysts has arisen steadily over the years because of the commercial success of these systems. This success results from an enhanced ability to control the catalytic activity and selectivity by tailoring the catalyst composition . A long-standing question regarding such bimetallic systems is the nature of the properties of the mixed-metal system which give rise to its enhanced catalytic performance relative to either of its individual metal components. These enhanced properties (improved stability, selectivity and/or activity) can be accounted for by one or more of several possibilities. First, the addition of one metal to a second may lead to an electronic modification of either or both of the metal constituents. This... 

The reader may notice many cross-references between the five contributions, which support the view that chemical modification of surfaces, particularly the nanostructuring, is not only interesting for its own sake, but also relevant to a wide range of practice applications. Their seminal role in bioelectrochemistry, bio-sensing, electrocatalysis and electroanalysis among others is clearly evident in this volume. 

Chemical modification of surface residues of HRP is one method which may offer some improvement in thermal or long-term stability of the enzyme. The -amino groups of the six surface Lys residues can be modified by reaction with carboxylic anhydrides and picryl sulfonic acid (296). In this example the number of sites modified was found to be more significant than the chemical nature of the modification, at least as a criterion for improved stability. Other methods explored include the use of bifunctional crosslinking reagents to couple surface sites on the enzyme (297). Future developments are likely to be concerned with the selection of site-directed mutants of HRP C that show enhanced thermal stability. Dramatic increases in thermal stability of up to 190-fold have been reported recently for mutants of Coprinus cinereus peroxidase (CIP) generated using a directed evolution approach (298). 

The concentration of a small molecule reactant inside the polymer coils can be lower than outside when one uses a poor solvent for the polymer. This results in lower local and overall reaction rates. In the extreme, a poor solvent results in reaction occurring only on the surfaces of a polymer. Surface reactions are advantageous for applications requiring modification of surface properties without affecting the bulk physical properties of a polymer, such as modification of surface dyeability, biocompatibility, adhesive and frictional behavior, and coatability [Ward and McCarthy, 1989]. 

Norsten TB, Jeoung E, Thibault RJ, Rotello VM. Specific hydrogen-bond-mediated recognition and modification of surfaces using complementary functionalized polymers. Langmuir 2003 19 7089-7093. 

Peng Y, Liu HW, Zhang XY, Li YS, Liu SY (2009) CNT templated regioselective enzymatic polymerization of phenol in water and modification of surface of MWNT thereby. J Polym Sci A Polym Chem 47(6) 1627-1635... 

Amylose brushes (a layer consisting of polymer chains dangling in a solvent with one end attached to a surface is frequently referred to as a polymer brush) on spherical and planar surfaces can have several advantageous uses, such as detoxification of surfaces etc. The modification of surfaces with thin polymer films is widely used to tailor surface properties such as wettability, biocompatibility, corrosion resistance, and friction [142-144]. The advantage of polymer brushes over other surface modification methods like self-assembled monolayers is their mechanical and chemical robustness, coupled with a high degree of synthetic flexibility towards the introduction of a variety of functional groups. 

In most practical uses of polymeric particles, their surfaces play a very important role by taking part in interfacial interactions such as recognition, adsorption, catalytic reactions, etc. When we want to use polymer particles, we first check whether the chemical and physical structures of the surfaces meet the purpose. If some of them do not satisfy the criteria, we may seek other particles or try to modify the existing particles. This chapter mainly deals with the modification of surface of existing particles. In addition to chemical modification of particle surfaces, modification of the morphology of particles is also described. 

The surface of polymer particles obtained by emulsion polymerization is occupied by emulsifier molecules, initiator fragments, and hydrophilic comonomer units. Therefore, desirable design of the surface ought to be done by choosing the emulsifier, initiator, and comonomer. Some of them are employed in aiming for postreaction at the surface to convert it into a functional one. When any change is necessary on the particle surface, modification of surface can be done by the following means ... 

Modifications of surface of materials adapted for contact with human or animal tissues to impart biofunctional properties. These apply typically to ocular implants, surgical instruments, medical devices, or contact lenses. ... 

---