Structure, polyethyleneimine

Polyethyleneimine is also extensively cyclized as a result of intramolecular nucleophilic attack of primary and secondary amines on the iminium group. This results in cyclic oligomer as well as polymer molecules containing large-sized rings as part of their structure. 

The poly(ether/amide) thin film composite membrane (PA-100) was developed by Riley et al., and is similar to the NS-101 membranes in structure and fabrication method 101 102). The membrane was prepared by depositing a thin layer of an aqueous solution of the adduct of polyepichlorohydrin with ethylenediamine, in place of an aqueous polyethyleneimine solution on the finely porous surface of a polysulfone support membrane and subsequently contacting the poly(ether/amide) layer with a water immiscible solution of isophthaloyl chloride. Water fluxes of 1400 16001/m2 xday and salt rejection greater than 98% have been attained with a 0.5% sodium chloride feed at an applied pressure of 28 kg/cm2. Limitations of this membrane include its poor chemical stability, temperature limitations, and associated flux decline due to compaction. 

Figure 10.8 Chemical structures of positively charged polyethyleneimine (PEI), polyallyl-aminhydrochlorid (PAH), polylysine hydrobromide (PL) and negatively charged polystyrene-sulfonate (PSS). M+ denotes a metal ion such as Na+.

Figure 3.21 Idealized structure of polyethyleneimine crosslinked with toluene 2,4-diiso-cyanate. This was called the NS-100 membrane. The chemistry was first developed by Cadotte to make interfacial reverse osmosis membranes with almost twice the water flux and one-fifth the salt leakage of the best reverse osmosis membranes then available. Even better membranes have since been developed by Cadotte and others [47]...

DNA has been embedded in LbL films by assembling with polycations like PLL, polyethyleneimine (PEI), and poly(dimethyldiallylammonium chloride) (PDAD) [38-42]. Zhang showed that the DNA released from the film with synthetic degradable polyamine is transcriptionally viable [41]. DNA molecules can keep their structure when incorporated in the film with synthetic polymers [39], making films with DNA suitable candidates for gene delivery. 

The nitrene obtained by photolysis may under certain conditions be highly radicalar, and this method of preparation, likely to cause cross-linking, was avoided. When prepared by a-elimination, carbethoxynitrene reacts with cyclohexene to give a mixture consisting of 85% addition product and 15% various substitution products (13). This reaction was used in attempts to prepare macromolecules with a polyethyleneimine structure. A preliminary investigation showed that the polyisoprenes react to a greater extent than the polybutadienes, and the reaction was first studied on model polyisoprenes. 

Figure 8.10. TEM images of Au55 monolayers showing a hexagonal (a) and a cubic (b) structure. The monolayers were prepared on a polyethyleneimine functionalized carbon grid. The magnified inset in (a) shows single clusters in the hexagonal form (reproduced with permission from reference [29]).

Because of this structural characteristics vdiich are much different from those of vinyl polymers, polyethyleneimine (PEI) is eicpected to provide interesting microenvironments for catalysis. Femandez-Prini and Turyn studied the deconq>osition of p-nitrophenyl fhosphate 2 in the presence of polyetih>ieneimine (114). 

Interactions between macromolecules can occur in formulations, for example when preparations are mixed. They can be put to good advantage in the synthesis of novel compounds. Polyethyleneimine and poly(acrylic acid) form a polyelectrolyte complex with saltlike bonds as shown in (V). If the complex is heated as a film, interchain amide bonds are formed between the groups which formed electrostatic links. The nonionised -COOH and -NH groups in the chain are the points of structural defects in the film. 

Polyethyleneimine (PEI) is one of the most extensively examined polymers because it has a relatively high transfection efficiency. PEI is believed to enter the cell via an endocytotic route and to possess a buffering capacity and the ability to swell when protonated.52,53 Therefore, at low pH values, it is believed that PEI prevents acidification of the endosome and induces a large inflow of ions and water, subsequently leading to rupture of the endosomal or lysosomal membrane so that the PEI-plasmid DNA complex is delivered to the cytoplasmic space.54,55 PEI is also reported to undergo nuclear localization while retaining an ordered structure once endocytosed.53 However, the transfection efficiency of PEI depends on its molecular weight and structure.56-58... 

Commercial polyethyleneimine 1 is prepared by ring-opening polymerization of ethyleneimine [Eq. (6—1)]. This polymer is a highly branched, relatively compact, water-soluble macromolecule, and approximately contains 25% primary, 50% secondary, and 25% tertiary nitrogen atoms 112). The averse structure is therefore represented as i ven below. Recently, Saegusa et al. succeeded in preparing linear, crystalline polyethyleneimine by polymerization of 2-oxazoline and subsequent hydrolysis [Eq. (6-2)] (ii5). 

Polyethyleneimine (PEI) was used commercially in the 1960s and shortly thereafter removed from hair products. However, because of new and improved synthetic techniques, it may be making a comeback. Furthermore, several interesting scientific studies have been conducted with this polymer. They illustrate some useful principles relevant to the adsorption of cationic polymers to keratin fibers. There are two signihcant structural differences between PEI and polymer JR ... 

Polyethyleneimine low molecular weight but structured cationic products available as liquids, generally these are more effective as drainage aids... 

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