Question

Electrostatic interaction between a positively charged polymer and a negatively charged polymer in an aqueous medium most likely results in the formation of a .

• A. chemical-crosslinked hydrogel
• B. complex coacervate
• C. photo-crosslinked hydrogel
• D. liposome

Hint:

Two oppositely charged polymers attracting through ionic forces alone, with no covalent crosslinking step, is the classic setup for complex coacervation.

Answer 1

The Correct Option is B

Step 1: Identify what kind of interaction is described.
The question describes two oppositely charged polymers, a polycation and a polyanion, mixed together in water. The forces holding them together are purely electrostatic, ionic attraction between opposite charges, with no chemical bond-forming step and no light exposure involved.

Step 2: Recall what electrostatic complexation between polyelectrolytes produces.
When oppositely charged polyelectrolytes are mixed in an aqueous medium, their charges neutralise each other's counter-ions and the polymer chains associate through ionic pairing. This process is called complex coacervation, and it produces a complex coacervate, a dense, polymer-rich liquid phase that separates out from the surrounding dilute aqueous phase. This is purely a physical, electrostatic self-assembly process.

Step 3: Check the chemical-crosslinked hydrogel option.
A chemical-crosslinked hydrogel forms when polymer chains are joined by covalent bonds, usually added through a chemical crosslinking agent or reaction. The scenario here has no crosslinking chemistry mentioned, only electrostatic attraction, so this option does not fit.

Step 4: Check the photo-crosslinked hydrogel option.
A photo-crosslinked hydrogel needs light, usually UV, exposure with a photoinitiator to trigger covalent bond formation between polymer chains. There is no light source involved in simple electrostatic mixing, so this option is also incorrect.

Step 5: Check the liposome option.
A liposome is a spherical vesicle formed by lipid molecules self-assembling into a bilayer in water, driven mainly by the hydrophobic effect on the lipid tails, not by polymer-polymer electrostatic attraction. Since the question specifically involves two charged polymers, not lipids, this option does not match either.

Step 6: Confirm the correct match.
Only complex coacervation directly describes what happens when a polycation and a polyanion interact through pure electrostatic attraction in water, a liquid-liquid phase separation into a dense coacervate phase, with no covalent bonds and no lipid bilayer involved.

Final Answer:
The electrostatic interaction between the two oppositely charged polymers most likely forms a complex coacervate.