chemistry

Polyethylenimine

Polyethylenimine is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Polyethylenimine rather than just read about it. In short: Polyethylenimine (PEI) or polyaziridine is a polymer with repeating units composed of the amine group and two carbon aliphatic CH2CH2 spacers. Linear polyethyleneimines contain all secondary amines, in contrast to branched PEIs which contain primary, secondary and tertiary amino groups.

Key takeaways

Polyethylenimine belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Polyethylenimine to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Polyethylenimine from memory before moving on to harder problems.

Reference excerpt

Polyethylenimine (PEI) or polyaziridine is a polymer with repeating units composed of the amine group and two carbon aliphatic CH2CH2 spacers. Linear polyethyleneimines contain all secondary amines, in contrast to branched PEIs which contain primary, secondary and tertiary amino groups. Totally branched, dendrimeric forms were also reported. PEI is produced on an industrial scale and finds many applications usually derived from its polycationic character.

Properties The linear PEI is a semi-crystalline solid at room temperature while branched PEI is a fully amorphous polymer existing as a liquid at all molecular weights. Linear polyethylenimine is soluble in hot water, at low pH, in methanol, ethanol, or chloroform. It is insoluble in cold water, benzene, ethyl ether, and acetone. Linear polyethylenimine has a melting point of around 67 °C. Both linear and branched polyethylenimine can be stored at room temperature. Linear polyethylenimine is able to form cryogels upon freezing and subsequent thawing of its aqueous solutions.

Synthesis Branched PEI can be synthesized by the ring opening polymerization of aziridine. Depending on the reaction conditions different degree of branching can be achieved. Linear PEI is available by post-modification of other polymers like poly(2-oxazolines) or N-substituted polyaziridines. Linear PEI was synthesised by the hydrolysis of poly(2-ethyl-2-oxazoline) and sold as jetPEI. The current generation in-vivo-jetPEI uses bespoke poly(2-ethyl-2-oxazoline) polymers as precursors.

Applications Polyethyleneimine finds many applications in products like: detergents, adhesives, water treatment agents and cosmetics. Owing to its ability to modify the surface of cellulose fibres, PEI is employed as a wet-strength agent in the paper-making process. It is also used as flocculating agent with silica sols and as a chelating agent with the ability to complex metal ions such as zinc and zirconium. There are also other highly specialized PEI applications:

Biology PEI has a number of uses in laboratory biology, especially tissue culture, but is also toxic to cells if used in excess. Toxicity is by two different mechanisms, the disruption of the cell membrane leading to necrotic cell death (immediate) and disruption of the mitochondrial membrane after internalisation leading to apoptosis (delayed).

Attachment promoter 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.

Transfection reagent Poly(ethylenimine) was the second polymeric transfection agent discovered, 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.

Permeabilization of gram negative bacteria Poly(ethylenimine) is also an effective permeabilizer of the outer membrane of Gram-negative bacteria.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Polyethylenimine

Start with the simplest possible case. Write down what Polyethylenimine claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Polyethylenimine before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Polyethylenimine ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Polyethylenimine

In research: Polyethylenimine appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Polyethylenimine in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Polyethylenimine is common in secondary-school and first-year university syllabi. It links to neighbouring topics Amines, Polyelectrolytes, Polymers, so understanding it makes those chapters shorter.
In everyday life: Look for Polyethylenimine outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Polyethylenimine in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Polyethylenimine means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Polyethylenimine out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Polyethylenimine in simple terms?

Why does Polyethylenimine matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Polyethylenimine?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Polyethylenimine.