DADMAC stands for Diallyldimethylammonium chloride. It is the monomer (the single, small molecule building block) used to create the polymer PolyDADMAC (Polydiallyldimethylammonium chloride).
Here's a detailed look at the DADMAC monomer:
Chemical Name: Diallyldimethylammonium chloride
Chemical Formula: C₈H₁₆ClN
Structure:
It features a central quaternary ammonium nitrogen atom (N⁺).
This nitrogen is bonded to two methyl groups (-CH₃).
It is also bonded to two allyl groups (-CH₂-CH=CH₂). The presence of these two carbon-carbon double bonds (C=C) is crucial.
The positive charge on the nitrogen is balanced by a chloride ion (Cl⁻).
Its structure is often written as [CH₂=CH-CH₂-N⁺(CH₃)₂-CH₂-CH=CH₂] Cl⁻.
Key Properties:
Reactive Sites: The two allyl groups (containing C=C double bonds) are highly reactive. This allows DADMAC molecules to undergo a chemical reaction called polymerization.
Cationic: Like its polymer counterpart, the monomer carries a permanent positive charge on the quaternary ammonium group, making it water-soluble and cationic.
State: Typically a colorless to pale yellow liquid.
Function: DADMAC itself is not typically used as a final product in large-scale applications like water treatment. Its primary role is as the raw material or precursor.
Through a polymerization process (often free-radical initiated), the double bonds in many DADMAC monomers open up and link together, forming long chains.
This creates the high molecular weight polymer PolyDADMAC, where the quaternary ammonium groups (and their positive charges) are now part of a long chain, resulting in an extremely high density of positive charges along the polymer backbone.
In simple terms: Think of DADMAC as a single "bead" with two sticky ends (the double bonds) and a positive charge. PolyDADMAC is the long "string" or "necklace" made by linking hundreds or thousands of these DADMAC beads together. The string has a very strong overall positive charge, which is what makes it effective as a coagulant.
