Polymer modification approaches

In our research, three chemical modification approaches were investigated bromination, sulfonylation, and acylation on the aromatic ring. The specific objective of this paper is to present the chemical modification on the PPO backbone by a variety of electrophilic substitution reactions and to examine the features that distinguish modified PPO from unmodified PPO with respect to gas permeation properties, polymer solubility and thermal behavior. 

Polymer modifications represent a valuable synthetic approach to unique polymer compositions, structure, and properties not readily available by the direct polymerization of monomers. Modified polymeric products already exist in the commercial world (modified celluloses, for example) so the approach is not new. However, it is an interesting and challenging opportunity to develop new materials for a variety of specialty applications using the "chemistry on polymers" approach. 

A number of nanotube surface modification approaches have been reported in the recent years. Non-covalent surface modifications aim to physically wrap polymer chains around the nanotubes or adsorb various surfactant molecules on the surface of nanotubes. Thus,... 

The first report of a polymer-supported approach to this reaction appeared in 1987 [48]. Enantiopure amino alcohols such as ephedrine, prolinol, and 3-exo-amino-isoborneol were attached to Merrifield polymer. The use of polymer-supported 3-exo-aminoisoborneol 40 resulted in quite high enantioselectivity ( 95 % ee) in the ethylation of aldehydes with diethylzinc (Eq. 15), a result comparable with those obtained from the corresponding low-molecular-weight catalyst system (Eq. 16). A similar system was also reported in 1989, this time using ephedrine derivatives (41,42) and prolinol derivative (43) [49]. A methylene spacer was introduced between the polymer and the amino alcohol to improve activity [50]. Despite this the selectivity was always somewhat lower than that obtained from the low-molecular-weight catalyst (44). These chiral polymers were all prepared by the chemical modification method using Merrifield polymer. 

Another approach was recently developed by Smeenk et al. [90]. They used the combination of protein engineering and polymer modification for the creation of a series of silk-based block copolymers. Spider silk consists of two major domains, a j0-sheet crystalline domain, which gives strength to the protein, and a less well-defined amorphous domain, which introduces elasticity and toughness. Smeenk and co-workers produced a j0-sheet forming protein... 

Another approach makes use of polymer-modified NAD [modification with polyethylene glycol (PEG MW = 20 000)], thus retaining it on account of its drastically increased size (Fig. 16.2-58) l239 241l. The polymer modification usually leads to a drastically increased Km value, whereas the Vmax value is generally over 50% of that of low molecular weight NAD(P) (Table 16.2-17). 

In addition, Mylar (and PET in general) is a widely used biocompatible material. For this reason many approaches to the modification and functionalization of the polymer surface by wet chemistry, plasma processes, or UV treatment have been reported in the literature [19-22]. These surface modification approaches demonstrate that it is possible to improve the reactivity of the PET surface in order to generate specific groups on the surface, or to immobilize biomolecules. Therefore, possibilities for (bio)chemosensing on a fully flexible mechanical support can be envisioned and are very interesting for innovative applications such as smart packaging and biotechnology. 

For a polymer to be useful, it must be able to function properly in a given application. The performance of a polymer is determined primarily by the composition and structure of the polymer molecule. These control the physical, chemical, and other characteristics of the polymer material. Therefore modification of the composition of the structural units represents one of the main approaches to the modification of polymer behavior. In addition to the chemical nature and composition of the structural units that constitute the polymer backbone, molecular architecture also contributes to the ultimate properties of polymeric products. Thus polymer modification can be accomplished by employing one or more of the following techniques ... 

Since there are several chapters in this book that are devoted to the medical applications of polyesters, which the readership is encouraged to read, the emphasis of this chapter therefore is on reviewing the strategies and chemistries that have been employed to derivatize polyester backbones. In order to ensure the relevance of these backbone modification approaches to current topics in medicine and the green technologies, the chapter focuses on paradigms that have generality to either a polymer family or a routine synthesis route. 

In another work, Nogueira et al presented a covalent modification approach with thiophene groups located at the edges and defects of SWCNTs in order to modify the interaction with the polymer matrix with the aim of its application in solar cells. Raman spectra of the pristine SWCNTs, purified material (SWCNT-COOH) and the modified material (SWCNT-THIOP) were obtained. For the non-purified SWCNT, at least four distinct tube radii were observed in the Raman spectrum excited with a wavelength of 632.8 nm. The main peak for the RBMs occurs at 162 cm (1.4 nm diameter), whereas... 

The modification of polymer surfaces both in terms of structure and functionality is a subject that has been evidenced to be of theoretical and practical interest [ 1,2]. In this sense, a large amount of literature has been published describing a wide variety of surface chemical modification approaches such as flame or corona treatments, chemical reactions (in solution), plasma or UV treatments or the application of polymer coatings among others [3-11],... 

The two foregoing modification approaches produce devices in response to impedance in two different ways, capacitive and resistive, as described above. Both are label-free approaches with the potential directly to detect antigens and haptens in sandwich or competitive immunoassay formats. However, they are both somewhat limiting in their overall sensitivity. Non-label-free impedimetric approaches that offer enhancements in sensitivity are the use of electroactive polymer layers and the use of redox-active and/or nanoparticle labels. 

Typically, the native sequence GAG synthases will only transfer the authentic UDP-sugars to produce the natural polymer. However, we have now created new enzymes that can make novel polymers that are not known to exist in Nature. We used a chimeric genetic modification approach to map out the Gal/Glc specificity for UDP-hexosamines of the Pasteurella pmHAS [HA... 

---