Poly chemical structure modification

This article surveys the research work on the synthesis and modification reactions of poly(ethyleneimine) as well as its applications to metal complexation processes. Poly-(ethyleneimine), one of the most simple heterochain polymers exists in the form of two different chemical structures one of them is branched, which is a commercially available and the other one linear which is synthesized by cationic polymerization of oxazoline monomers and subsequent hydrolysis of polyf(/V acylimino)cthylcne]. The most salient feature of poly(ethyleneimine) is the simultaneous presence of primary, secondary, and tertiary amino groups in the polymer chain which explains its basic properties and gives access to various modification reactions. A great number of synthetic routes to branched and linear poly(ethyleneimine)s and polymer-analogous reactions are described. In addition, the complexation of polyfethyleneimine) and its derivatives with metal ions is investigated. Homogeneous and heterogeneous metal separation and enrichment processes are reviewed. 

The chemical structure of poly(ADP-ribose) su ests not only that its modification of acceptor proteins should modify the struaure and function of the acceptor proteins, but also that the poly(ADP-ribose) molecule itself should possess an intrinsic structural information that can alter cellular fimction(s). 

Dendrimers such as poly(amidoamine) (PAMAM) and poly(propylenimine) (PPI) have also been studied for gene delivery in vitro and in vivo due to their high transfection efficiency. However, the toxicity of the dendrimers is of major concern for their medical use. Generally, in vivo toxicity of dendrimers is related to various factors, including their chemical structure, surface charge, generation and the dose of dendrimer used. Surface modification with PEG or replacement with low generation dendrimers have been reported to be able to improve the biocompatibility of these biomaterials. ... 

In conclusion, the phase behavior of symmetrically di-n-alkyl-substituted poly(silane)s and poly(silylenemethylene)s is similar both classes of polymers form the same type of mesophase, although it cannot be obtained in pure form for the poly(silylenemethylene) studied. The mobility in the mesophase, characterized by the quadmpole splitting, appears to depend strongly on the chemical structure of the backbone. For different poly(silane)s, the mobility in the crystalline phase is obviously influenced by the conformation of the backbone zW-trans vs. 73-helical) and therefore depends on the length of the side-chains. Application of pressure to poly(silane)s with 73-helical backbones leads to the formation of high-pressure crystalline modifications with dA -trans backbone conformation. The pVT studies made it possible to define the precise conditions for the pressure-induced phase transitions. 

To improve performance, many PEDT derivatives used either alone or in combination have been proposed. While the electro-optical properties of WO3 are fixed, the colors and hue of conducting polymers may be altered by modification of the monomers. For example, Reynolds has studied the electrochromic properties of a multitude of EDT derivatives [100,109], and recently reported an all-polymer electrochromic device based on two different PEDT derivatives [110]. Depending on their chemical structure, the various PEDT derivatives exhibit different colors upon switching from the oxidized to the reduced state. For example, poly(tetradecylethylenedioxythiophene) (C14-EDT) is similar in switching to PEDT from transparent to blue, but it has an enhanced optical contrast. 

The chemical structures of representative modified cationic polymers are shown in Fig. 4. Representative polymers are aminomethylated acrylamide homopolymer (Mannich modification) with formaldehyde and dimethyl-amine, and Hoffman-decomposed poly(acrylamide) made from the reaction of an acrylamide homopolymer with sodium perchlorate at relatively low temperature. Because the former polymer (Mannich-modified type) does not show molecular weight reduction during modification, high molecular weight modified polymers result. However, the latter example (Hoffman-decomposed type) has a shortcoming molecular weight is... 

Other modifications of the chemical structure of the repeating units of poly(aryl ether ketone)s also show potential for significant improvement. For example, the introduction of fluorinated aromatic rings and bulky groups re-... 

Poly(ether-ester) (PEE) copolymers obtained by modification of poly(ethyl-ene terephthalate) with up to 20 wt% of poly(ethylene ether) glycol was first described by Coleman [8]. Subsequently, the DuPont Co. developed poly(ether-ester) elastomers, which were commercially introduced in 1972 under the trade name Hytrel [4,9]. The polyester thermoplastic elastomers are nowadays produced by several companies. Apart from DuPont, these are DSM, The Netherlands (Arnitel ), General Electric, USA (homed ), Hoechst Celanese, USA (Retiflex ), Toyobo, Japan (Pelprene ), Elana, Poland (Elitel ) [2,10]. The synthesis, chemical structure, physical properties, and some new applications of polyester TPE are discussed in this chapter (about the development of TPE, see also Chapter 1, while details on some commercial TPE products can be found in Chapter 17). 

The commercial polyester elastomers are mostly based on poly(tetrameth-ylene oxide) (PTMO) as flexible segment and poly(butylene terephthalate) (PBT) as rigid segment. Yet, many chemical modifications of some particular segments and also segments of totally different chemical structure have been examined and applied. Thus, in addition to PTMO [1,2,11-16], poly(ethylene oxide) (PEO) [17-22], poly(aliphatic oxide) (C2-C4) copolymers [23-30], poly (butylene succinate), and other aliphatic polyesters [31-35], polycaprolac-tone (PCL), polypivalolactone (PVL) [36,37], aliphatic polycarbonates (PC) [38-41], dimerized fatty acid (DFA)-based polyesters [42-50], polyamide 66 and derivatives [47-57], polyolefins [58-60], rubbers [61-63], and polydimethyl-siloxane [64,65] are used as flexible segments of polyester elastomers. 

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