Bulk modification

The ultimate goal of bulk modification endows with the polymer-specific surface composition or a specific property for a given application. The bulk modification can be classified into blending, copolymerization, interpenetrating polymer networks (IPNs), etc. 

The treatment with sulfuric acid produces a noticeable decrease in contact angle (i.e., improved wettability) due to the removal of zinc stearate and the formation of polar moieties on the mbber, mainly the creation of highly conjugated C=C bonds and the sulfonation of the butadiene units (Figure 27.1), i.e., the hydrogen of C—H bond is removed and replaced by a SO3 molecule, which is then hydrogenated to form a sulfonic acid at the site of attachment. The treatment is not restricted to the surface but also produces a bulk modification of the mbber. 

The absorbances at 1730, 1630, 1460, 1379, 1260, 1120, and 1019 cm follow an upward trend with concentration in the case of the bulk-modified samples also (Figure 31.4a through g) in line with the gel content, due to the reasons, pointed out above. Since the surface concentration of TMPTA per unit volume of EPDM is lower in the case of bulk modification as compared to surface modification, the optimum value of the concentration of TMPTA is not observed in these plots. 

As an example, bulk modification by the organic reaction of unsaturated PHA with sodium permanganate resulted in the incorporation of dihydroxyl or carboxyl functional groups [106]. Due to the steric hindrance of the isotactic pendant chains, complete conversion could not be obtained. However, the solubility of the modified polymers was altered in such a way that they were now completely soluble in acetone/water and water/bicarbonate mixtures, respectively [106]. Solubility can play an important role in certain applications, for instance in hydrogels. Considering the biosynthetic pathways, the dihydroxyl or carboxyl functional groups are very difficult to incorporate by microbial synthesis and therefore organic chemistry actually has an added value to biochemistry. 

Beat wave, 169 Betatron emission, 178 Betatron radiation, 168 Bismuth (Bi), 48, 58, 59 Bond-softening, 7 Bragg crystals, 125 Bragg peak, 175 Bremsstrahlung, 139, 168, 173 Bremsstrahlung photons, 159 Brunei effect, 201 Bubble regime, 171 Bulk modifications, 82, 103... 

Other polymer modifications involve surface or bulk modifications, and a majority of them are used in medical technology. Examples of these processes are ... 

The adsorption of the reagent is not quite effective on the catalyst or/and ii) the water formed during the reaction could lead to a superficial (or a bulk) modification of the catalyst and of the adsorption properties of some of the reagents. 

Treatment in H2 at 673 K as above affects only the surface, but higher temperatures induce bulk modifications. A Mo2N-B sample reduced at 673 K, 773 K and 823 K had a cubic yMo2N pattern with lattice parameters of 0.420, 0.417 and 0.414 nm, respectively. Heating the sample to 873 K left the lattice parameter at 0.414 nm, but resulted in the formation of some Mo metal. 

Compared to genosensors based on GEC, the novelty of this approach is in part attributed to the simplicity of its design, combining the hybridization and the immobilization of DNA in one analytical step. The optimum time for the one-step immobilization/hybridization procedure was found to be 60 min [66]. The proposed DNA biosensor design has proven to be successful in using a simple bulk modification step, hence, overcoming the complicated pre-treatment steps associated with other DNA biosensor designs. Additionally, the use of a one-step immobilization and hybridization procedure reduces the experimental time. Stability studies conducted demonstrate the capability of the same electrode to be used for a 12-week period [66]. 

The last decade has seen an explosion of activity in the field as electrochemists have wrestled with unfamiliar, and often intractable, problems generated by the very wide range of materials investigated, difficulties often compounded by the use of polycrystalline samples whose bulk and surface properties have proved resistant to control. In addition to the elemental semiconductors and the III/V materials, a huge range of n- and p-type oxides, sulphides, selenides, and tellurides have been described and surface and bulk modifications carried out in the hope of enhancing photoelectrochemical efficiency. New theoretical and experimental tools have developed apace and our fundamental understanding of the semiconductor-electrolyte interface has deepened substantially. 

Surface modification of wood is a noteworthy new technique of wood improvement in which only surfaces are treated. The inner parts of the wood are unmodified and as a result retain their inherent properties. Of course, less chemical is needed to modify only the surfaces of wood compared to bulk modification. Vapor phase reactions are particularly suitable for surface treatments. This could reduce the amount of reagents required for modification and make the removal of unreacted reagent easier, thereby reducing treatment costs. 

Fig. 6 Functionalization of polymer fibers for nerve regeneration, (a) Functionalization with adsorption or covalent binding of ECM molecules to electrospun polymer fibers [169]. (b) Functionalization by blending of ECM molecules with synthetic polymers before electrospinning [93]. (c) Functionalization by chemical bulk modification of the electrospinnuig solution [158]...

The same problems occur on bulk modification of membrane polymers. The introduction of hydrophilic functionalities to the initially hydrophobic polymer may alter the film-forming properties to such an extent, that membrane formation is restricted to materials with a low degree of modification. 

Therefore, the surface and bulk modifications of microstructure of the SE in any particular case can change the metrological characteristics of the YSZ-based gas sensor. This fact has been proven by various publications, where the same material of the SE has been sintered at the different conditions, and subsequently, such characteristics of the gas sensor as sensitivity and response/recovery time at the same temperature differ significantly from one publication to another. The efficiency of such modifications can be determined by changing the value for ctoPo in nonequilibrium conditions from its equilibrium condition Oo 3o. hi case of ctoPo = cto 3o, the surface modifications cannot change the permeability of the thick electrodes because the value of Oo 3o = (Xg 35 exp (-2c0g) can only be determined by the concentration of the measuring gas within the SE and does not connect to the state of the interphase boundaries. 

The required network rigidity results from the three-dimensional cross-linking of the [SiC>4]4 tetrahedrons. Bulk modification by introduction of organic units through =Si-C- bonds leads to a change of network connectivity and should also affect porosity or surface area. On the other hand, in this case the modification becomes an intrinsic property that should not be affected by surface corrosion (Scheme II), because after removal of the surface layer by hydrolytic processes, the following layer exhibits the corresponding structure and properties. The properties to be developed determine whether a surface or a bulk modification is more appropriate. 

The organic bulk modification of silica can be used for tailoring specific surface properties. One advantage of this reaction route is the possibility to use a one-step process, but the reaction must be controlled very carefully. Multifunctional materials can be synthesized, too. 

Estimates of the effect on strength characteristics of inhibited films of combining Cl with the polymer binder show that surface modification of film materials is preferable to bulk modification. 

The inclusion of additives in the aqueous phase has several objectives. These additives can be used to control the pore and interconnect sizes but, most importantly, they can be used to chemically modify the polymer after polymerization. Surface as well as bulk modification of PHP cannot be achieved through post-polymerization impregnation especially when the pore/interconnect sizes are small and when the sample is thick. Since the additives are uniformly distributed in the aqueous phase droplets, at the postpolymerization modification stage, the additives are uniformly distributed within the pores. As the aqueous phase is the major emulsion phase, large quantities of desired substances can be incorporated within PHP at levels comparable to that of the polymer phase. 

The graft modifications by y-irradiation, electron beams, or plasma are some of such methods that provide covalent modification of materials with the creation of interesting architecture. These three methods provide materials with a high level of purity they are surface-selective or may lead to the bulk modification of the matrix, although y-rays are preferred for their high... 

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