Polymers bulk modifications

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. 

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. 

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

Polymer surfaces are modified to obtain the desired surface properties without altering the bulk properties (J ). One of the most desired properties is adhesion between polymers and other materials such as polymers, metals or ceramics (2). There are many techniques for polymer surface modification, but they can be divided into two major categories. One is a dry process in which the polymers are modified with vapor-phase reactive species that are... 

Polymer surface modifications are omnipresent in applications where the surface properties of materials with favorable bulk properties are insufficient. By altering the surface characteristics using physical or chemical modification the desired surface properties may be achieved. Such treatments are required e.g. to enhance printability of films, the adhesion of paints, metal or other coatings, biocompatibility, protein resistances/reduced biofouling, etc. The diverse approaches met in practice include, among others, wet chemical and gas phase chemistry, plasma or corona, UV/ozone and flame treatments. In most cases surface chemical modification reactions take place that alter the surface energy in a desired way. For example,... 

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. 

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. 

Surface or bulk modification depending on the Bulk material modification possible beam polymer film... 

The modifications of the polymers bulk properties via functional groups, such as amines, thiols, and carboxylic groups, offer a wide range of opportunities to allow for specific interactions of materials with cells. In the following section, some of these chemical modifications are outlined and their respective biontimetic prindples are also described. The modification of polymers with certain functional groups such as amines change... 

Hydrogels experience recoverable elasticity if the applied strain is modest (<20% in most instances). Since gel networks are often amorphous and homogeneous, strain recovery is expected whether stresses are isotropic, anisotropic, or bulk, as in the case of solvent swelling. Therefore, mbber elastic theory can be used to determine critical hydrogel parameters, originally developed for vulcanized mbber, and later modified for polymers. Further modifications for gels... 

Surface modification is a valuable tool for the design of appropriate membrane, as the interfacial characteristics required can rarely be achieved by bulk modification of the membrane-forming polymer without complications during membrane fabrication (He et al. 2009). Surface modification methods have been employed by the membrane manufacturers to produce hydrophilic, low-binding membranes (Peinemann and Nunes 2008) with improved membrane performances and properties (Pandey and Chauhan 2001 Robeson 1999). These methods include UV... 

Grafting with RIG can be initiated in a wide range of temperatures including subambient temperature, in monomers of various states such as bulk solution, emulsion, vapor, and even at solid state. Thus, RIG has been widely investigated for the preparation of PEMs and ion exchange membranes as bulk modification of polymer films can be achieved (Nasef and Hegazy 2004) unlike plasma-induced and UV-induced grafting, which produces surface modification in polymers (Finsterwalder and Hambitzer 2001). 

Because the first deviation from linearity of retention diagrams is hard to detect, T, may be determined by using any parameter related to the width or asymmetry of the peak, penetration in polymer bulk causing tailing before any modification of retention volume is noticeable [218]. For example the ratio of peak half width and retention time exhibits a pronounced increase at T, [220]. 

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