Polyethylene imines

Water-soluble polymers and polyelectrolytes (e.g., polyethylene glycol, polyethylene imine polyacrylic acid) have been used success-hilly in protein precipitations, and there has been some success in affinity precipitations wherein appropriate ligands attached to polymers can couple with the target proteins to enhance their aggregation. Protein precipitation can also be achieved using pH adjustment, since proteins generally exhibit their lowest solubility at their isoelectric point. Temperature variations at constant salt concentration allow for frac tional precipitation of proteins. 

Alkoxylated polyethyleneimines are obtained by reacting polyethylene-imine with a molecular weight of 2500 to 35,000 with an excess of propylene oxide and ethylene oxide with respect to the ethyleneimine unit in the... 

The earliest polymeric cationic aftertreatments stemmed from the development of crease-resist finishes for cellulosic fibres. One such, promoted specifically for its colour fastness improvements when applied as an aftertreatment to direct dyeings, was a condensation product of formaldehyde with dicyandiamide (Scheme 10.82). Many similar compounds followed, such as condensation products of formaldehyde with melamine (10.212), polyethylene imine) with cyanuric chloride (10.213) and alkyl chlorides with polyethylene imine) (10.214 R = alkyl). 

Scheme 2. Tomalia s divergent synthesis of dendronized polyethylene imine (PEI)...

Symmetric triblock copolymers of the ABA type, where B was PTHF and A poly(2-methyl-2-oxazoline), PMeOx, were prepared by cationic polymerization with trifluoromethanesulfonic anhydride as a difunctional initiator [58]. Subsequent hydrolysis of the PMeOx blocks with HC1 in a methanol/ water mixture resulted in the formation of the corresponding polyethylen-imine blocks (Scheme 20). Samples with relatively low molecular weight distributions were obtained. 

Scheme 9. (A) Different dendrimers as macromolecular scaffolds for MRI contrast agents ethylenediamine cored polyamido amine, generation 4 (PAMAM G4), top hyperbranched, ethylenediamine cored polyethylene imine (HB-PEI), bottom left hyperbranched, amino functionalized polyglycerol (HB-PG), bottom right. (B) Different moieties attached to the respective dendrimers via amide or thiourea bonds.

PEI (polyethylene imine) is often used as an additive when crosslinking enzymes with glutaraldehyde. Explain why. 

As published by Ferguson and Shah and independently by Bamford and Shiiki, polyethylene imine can be used as template for polymerization of acrylic acid. It was found that polyethylene imine forms water insoluble complex with polyacrylic acid. Polymerization was carried out at 31 C, using potassium persulphate as an initiator. The polymerization was followed by turbimetry and bromometric titration. During polymerization, the precipitation takes place, however, at GO C, degradation of the com-... 

Several other investigators have reported microencapsulation methods based upon polyelectrolyte complexes [289, 343]. For example, oppositely-charged polyelectrolytes (Amberlite IR120-P (cationic) and Amberlite IR-400 (anionic)) were recently used along with acacia and albumin to form complex coacervates for controlled release microcapsule formations [343]. Tsai and Levy [344,345] produced submicron microcapsules by interfacial crosslinking of aqueous polyethylene imine) and an organic solution of poly(2,6 dimethyl... 

Polyelectrolytes have recently found application in the development of pH sensitive liposomal controlled release systems. This application arises from the fact that polyelectrolytes may be used both to stabilize liposomes, and to disrupt liposomes in a pH dependent manner. Although the use of liposomes in oral pharmaceutical compositions has been discussed [424], liposomes generally suffer from poor stability and are therefore prone to leakage of the entrapped active agents. To overcome this problem, several authors have stabilized the liposomes using polyelectrolytes. For example, Tirrell and coworkers have employed ionene [425], and polyethylene imine) [426] to stabilize liposomes. Similarly, Sato and coworkers have studied maleic acid copolymers [427], and Sumamoto and coworkers have studied liposomes [428] coated with polysaccharides. In related work, Kondo and coworkers have emphasized the use of carboxymethyl chitin to produce artificial red blood cells [429-435]. 

Densmore, C.L., Orson, F.M., Xu, B., et al. (2000). Aerosol delivery of robust polyethylene-imine-DNA complexes for gene therapy and genetic immunization. Mol. Then, 1, 180-188. 

A further approach to electrically wire redox enzymes by means of supramolecular structures that include CNTs as conductive elements involved the wrapping of CNTs with water-soluble polymers, for example, polyethylene imine or polyacrylic acid.54 The polymer coating enhanced the solubility of the CNTs in aqueous media, and facilitated the covalent linkage of the enzymes to the functionalized CNTs (Fig. 12.9c). The polyethylene imine-coated CNTs were covalently modified with electroactive ferrocene units, and the enzyme glucose oxidase (GOx) was covalently linked to the polymer coating. The ferrocene relay units were electrically contacted with the electrode by means of the CNTs, and the oxidized relay mediated the electron transfer from the enzyme-active center to the electrode, a process that activated the bioelectrocatalytic functions of GOx. Similar results were observed upon tethering the ferrocene units to polyacrylic acid-coated CNTs, and the covalent attachment of GOx to the modifying polymer. 

The PEO salt complexes are generally prepared by direct interaction in solution for soluble systems or by immersion method, soaking the network cross-linked PEO in the appropriate salt solution [52-57]. Besides PEO, poly(propylene)oxide, poly(ethylene)suceinate, poly(epichlorohydrin), and polyethylene imine) have also been explored as base polymers for solid electrolytes [58]. Polyethylene imine) (PEI) is prepared by the ring-opening polymerization of 2-methyloxazoline. Solid solutions of PEI and Nal are obtained by dissolving both in acetonitrile (80 °C) followed by cooling to room temperature and solvent evaporation in vacuo. Polyethyleneimine-NaCF3S03 complexes have also been explored [59],... 

Let us finally mention polymers such as polyethylenoxide (PEO) or polyethylen-imine (PEI), in which NH4HS04 is dissolved (see also Section 15.5). Proton conducting films can be prepared with these materials. Although their conductivity is again relatively low, it is higher than that of pure PEO or PEI salts. 

The authors first mentioned investigated an anion-exchange membrane consisting of polyethylene imine crosslinked with epichlorohydrin in equilibrium with KC1 solutions. The concentration of Cl- ions and K+ ions in the membrane were determined analytically. The mobility of the Cl- ions in the membrane was determined according to the principle of the moving boundary. Thus in a membrane strip a sharp boundary is formed between the OH- and Cl- ions. This boundary will move under the influence of an electric field. This may be made visible with the aid of an indicator. The speed of the boundary is determined by the slowest ion, by consequence the Cl- ion in this instance. 

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

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