PDADMAC stands for Poly(diallyldimethylammonium chloride), a synthetic cationic polyelectrolyte widely used in water treatment, papermaking, cosmetics, and biomedical applications due to its strong positive charge and water solubility.

Chemical Structure

• Monomer unit: Diallyldimethylammonium chloride (DADMAC)

• Chemical formula of repeating unit:
  [−CH2−CH(CH2−N+(CH3)2−CH=CH2)Cl−−]n
  

• However, this is often simplified to reflect the actual polymerized structure after vinyl polymerization.

After polymerization via free-radical mechanism, the repeating unit of PDADMAC is typically represented as:

[−CH2−CH2−CH2−N+(CH3)2−CH2−CH2−]nCl−

But more accurately (and commonly accepted):

[−CH2−CH(CH2N+(CH3)2)−]nCl−

Or even more standard notation:

[−CH2−CH(CH2−N+(CH3)2)−]nCl−

Where:

• The backbone is a carbon chain from vinyl polymerization of the allyl groups.

• Each repeat unit carries a quaternary ammonium group (( \text{-N}^+(\text{CH}_3)_2-\text{CH}_2-\text{CH}=\text{CH}_2 ) before polymerization).

• Chloride (Cl⁻) acts as the counterion to balance the positive charge on nitrogen.

Key Features:

• Cationic: Permanent positive charge on quaternary nitrogen (independent of pH).

• Water-soluble: Due to ionic nature.

• High charge density: Makes it effective for flocculation, antimicrobial activity, and binding to negatively charged surfaces (e.g., cell walls, clay, cellulose).

Simplified Structural Diagram (repeating unit):

      CH3
       |
...–CH2–CH–...
       |
    CH2–N⁺(CH3)2  Cl⁻

(Note: The side chain is –CH₂–N⁺(CH₃)₂, with Cl⁻ as counterion.)

Applications:

• Flocculant in wastewater treatment

• Retention aid in paper manufacturing

• Antistatic agent

• Gene/drug delivery vector (in modified forms)

• Antimicrobial coatings

Let me know if you'd like the synthesis route or molecular weight details!