| Polyethylenimine | |
|---|---|
|
Poly(iminoethylene) |
|
|
Other names
Polyaziridine, Poly[imino(1,2-ethanediyl)] |
|
| Identifiers | |
| CAS number | 9002-98-6 |
| Properties | |
| Molecular formula | (C2H5N)n, linear form |
| Molar mass | variable |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
|
| Infobox references | |
Linear polyethyleneimines (PEIs) contain all secondary amines, in contrast to branched PEIs which contain primary, secondary and tertiary amino groups. The linear PEIs are solids at room temperature where branched PEIs are liquids at all molecular weights. Linear polyethyleneimines are soluble in hot water, at low pH, in methanol, ethanol, or chloroform. They are insoluble in cold water, benzene, ethyl ether, and acetone. They have a melting point of 73-75°C. They can be stored at room temperature.
Contents |
Polyethyleneimines are used in the cell culture of weakly anchoring cells to increase attachment. PEI is a cationic polymer; the negatively charged outer surfaces of cells are attracted to dishes coated in PEI, facilitating stronger attachments between the cells and the plate. However, polyethylenimine has very strong toxicity.[1]
Poly(ethylenimine) was the second polymeric transfection agent discovered[2], after poly-l-lysine. PEI condenses DNA into positively charged particles, which bind to anionic cell surface residues and are brought into the cell via endocytosis. Once inside the cell protonation of the amines results in an influx of counter-ions and a lowering of the osmotic potential. Osmotic swelling results and bursts the vesicle releasing the polymer-DNA complex (polyplex) into the cytoplasm. If the polyplex unpacks then the DNA is free to diffuse to the nucleus[3][4]. PEI is extremely cytotoxic[5] by two different mechanisms[6], the disruption of the cell membrane leading to necrotic cell death (immediate) and disruption of the mitochondrial membrane after internalisation leading to apoptosis (delayed).
Branched PEI can be synthesized by polymerization of aziridine[7]. Linear PEI was synthesised by the hydrolysis of poly(2-ethyl-2-oxazoline)[8] and sold as jetPEI[9]. The current generation in-vivo-jetPEI uses bespoke poly(2-ethyl-2-oxazoline) polymers as precursors[10].
Both linear and branched polyethylenimine has been used for CO2 capture, frequently impregnated over porous materials. First use of PEI polymer in CO2 capture was devoted to improve the CO2 removal in space aircraft applications, impregnated over a polymeric matrix[11]. After that, the support was changed to MCM-41, an hexagonal mesostructured silica, and large amounts of PEI were retained in the so called "molecular basket" [12]. MCM-41-PEI adsorbent materials led to higher CO2 adsorption capacities than bulk PEI or MCM-41 material individually considered. The authors claim that, in this case, a synergic effect takes place due to the high PEI dispersion inside the pore structure of the material. As a result of this improvement, further works were developed to study more in depth the behaviour of these materials. Exhaustive works have been focused on the CO2 adsorption capacity as well as the CO2/O2 and CO2/N2 adsorption selectivity of several MCM-41-PEI materials with PEI polymers [13][14]. Also, PEI impregnation has been tested over different supports such as a glass fiber matrix [15] and monoliths [16]. However, for an appropriate performance under real conditions in post-combustion capture (mild temperatures between 45-75ºC and the presence of moisture) it is necessary the usage of thermally and hydrothermally stable silica materials, such as SBA-15 [17], which also presents an hexagonal mesostructure.