Linear polyethylene imine

Fig. 10. High-loading ULTRA resins 15 based on the reductive cross-linking of linear polyethylene imines.

Branched and linear polyethylene imine), and poly(vinylimidazole), were similarly cross-linked in the presence of template Cu2+ or Co2+ ion, but no enhancement of selectivity towards the same metal ions was achieved 37>. 

Purely linear polyethylene imine) may be obtained, however, by cationic polymerization of oxazolines (discussed in the next section), followed by the hydrolysis of the resulting polymeric amide. 

Oxazolines are much less toxic than aziridines and therefore these monomers are preferred for the fabrication, for example, of linear polyethylene imines. 

Bannerjee, P., Weissleder, R., Bogdanov, A., Jr. Linear polyethylene-imine grafted to a hyperbranched polyfethylene glycol)-like core a copolymer for gene delivery. Bioconjug. Chem. 2006, 77(1), 125-131. 

A titration curve determined in 0.03 M NaCl at room temperature has been reported in the case of cro s-linked PVA 62). The shape of the curve is similar to that of the linear polymer. Cr< >< s-linked resins of polyethylene imine structure have been used to complex heavy m, tal ions from dilute solutions. The complex formation of these resins with metal ions was not thoroughly studied on a thermodynamic basis however, the authors 63) demonstrated that, from a practical point of view, at least one of these resins in column operations was able to concentrate Cu2+, Co2+ and Ni2+ from aqueous solutions, even in the presence of high concentrations of alkali- and alkaline earth metals. 

As mentioned above, the preparation of nanogels by addition reactions of functional macromolecular precursors is mainly used for biomedical applications. Thus, the choice of synthetic precursors for microgel formation is restricted to biocompatible materials. Moreover, as most applications are in drug delivery, the molecular weight of the gel precursors should be below the threshold for renal clearance, a value that depends on the molecular architecture and chemical nature of the polymer but that is usually smaller than 30kDa, which is set as the limit for linear PEG [97], Polymers that are mostly used and thus presented in more detail here are PEG, poly(glycidol) (PG), and polyethylene imine) (PEI). 

For polymer chemists it is interesting to know how well-known linear polymers can be linked with dendritic architectures and what the supramolecular consequences of this approach might be. Combination of dendrimers with linear polymers in hybrid linear-dendritic block copolymers has been employed to achieve particular self-assembly effects. Block copolymers with a linear polyethylene oxide block and dendritic polybenzylether block form large micellar structures in solution that depend on the size (i.e., the generation) of the dendritic block [10]. Amphiphilic block copolymers have been prepared by the combination of a linear, apolar polystyrene chain with a polar, hydrophilic poly(propylene imine) dendrimer [11] as well as PEO with Boc-substituted poly-a, -L-lysine dendrimers, respectively [12]. Such block copolymers form large spherical and cylindrical micelles in solution and have been described as superamphi-philes and hydra-amphiphiles , respectively. 

Fig. 1). These include linear polyethylene and polypropylene imines of varying degree of polymerization (Pn = 10 to 20) in non-methylated (PEI and PPI) and methylated (PMEI and PMPI) forms, which were specifically synthesized. Hexaazadocosane, which may be regarded as a model for a PPI with Pn = 6, was prepared by Michael addition of acrylonitrile to spermidine [12]. In addition, a commercially available PEI with high molecular mass and with a branched polymer architecture was employed. 

There are two different ways of preparing the simplest polyamine, polyethylen-imine. The first method leads to a commercial polymer. The parent monomer (aziri-dine) is used and the resulting polymer is highly branched due to pronounced chain transfer. The second method, leading to linear polyethylenimine, requires the preparation of polyoxazoline intermediate and is discussed in the next section. 

The structure-reactivity relationship for polyamine derivatives in activated ester hydrolysis was previously established [46]. Polyvinylamine (PVA), linear (LPEI) and branched (41% branching) polyethylene imine (BPEI) as well as their dodecyl- and imidazole-substituted derivatives with an approximate and equal degree of substitution (16-20%) were applied as catalysts. The compoundsp-NPA and 4-acetoxy-3-ni-trobenzoic acid (ANBA) as well as some of their homologues were used as substrates. At an excessive catalyst concentration relative to the substrate concentration, reactions proceeded at pseudo first order. In each series of polymers, the reaction rate constant was increased considerably by substitution of dodecyl (hydrophobic site) by imidazolyl (catalytic center) and when a charged substrate (electrostatic effect) was employed. At an equal degree of substitution, the catalytic activity increased in the following order LPEK PVA < BPEI. 

Linear 2. See Sodium metaphosphate Linear alcohol C13-15. See C13-15 alcohols Linear CIO alpha olefin. See Decene-1 Linear Cl6 alpha olefin. See Hexadecene-1 Linear CIS alpha olefin. See Octadecene-1 Linear C20 alpha olefin. See Eicosene-1 Linear (C12 and C14) alkyl alcohols, ethoxylated. SeeC12-14 pareth Linear polyethyleneimine. See Polyethylene imine... 

Figure 4.18.. Flocculation of silica particles Bridging by (1), cationic surfactant micelles (for example, cetyltrimethylammonium ions) (2) cationic three-dimensional polymer molecules (for example, cationic starch) (3) cationic linear polymers (for example, polyethylene imine.)...

Late transition metal catalysts that are highly active and produce high molecular weight polyolefins were recently reported [198,199]. For example, nickel and palladium-diimine catalysts 67 produce highly branched polyethylene that is totally different from those produced by conventional or homogeneous Ziegler-Natta catalysts [200]. On the other hand, iron and cobalt 2,6-pyridine bis(imine) complexes 68 give linear polyethylene [201,202]. These catalysts are used with co-catalysts such as MAO, and the active species are cationic. Neu-... 

Poly(ethylene oxide) is a linear polymer containing the donor oxygen atoms in the main backbone. Some other similar systems known to function as polymer electrolytes include simple poly ethylene glycol (PEG) [145], end acetylated PEG [146], poly propylene oxide (PPO) [ 147-148], poly(/ -propiolactone) [149], polyethylene succinate) [150-151],poly (ethylene adipate) [152],poly (ethylene imine) [153] and poly (alkylene sulfide) [154], Many of these form metal salt complexes. However, conductivities of the order of 10 s S cm are observed only at high temperatures. Table 5 summarizes this data. 

The sheer size and value of the polyethylene industry ensure that there is continued research, progress, and development in catalysis, for their potential commercial impact. Although this whole subject is not within the scope of this chapter, we mention a couple of aspects of the progress, which offer the potential to impact this industry. In 1995, DuPont introduced work, carried out with them at the University of North Carolina—via the largest patent applicafion ever in the USA. They disclosed what are described as post-metallocene catalysts. These are transition and late transition metal complexes with di-imine ligands, which form part of the DuPont Versipol technology. Such catalysts create highly branched to exceptionally linear ethylene homopolymers and linear alpha-olefins. Late transition metals offer not only the potential for the incorporation of polar comonomers, which until now has only been possible in LDPE reactors, but also their controlled sequence distribution, compared to the random composition of free radical LDPE copolymers. Such copolymers account for over 1 million tons per annum [20]. Versipol has so far only been cross-licensed and used commercially by DuPont Dow Elastomers (a former joint venture, now dissolved) in an EPDM plant. 

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