PolyDADMAC (polydiallyldimethylammonium chloride, CAS 26062-79-3) is one of the most widely used cationic polymers in water treatment, papermaking and personal care. Its unusual ring-forming polymerization chemistry, very high charge density and regulatory acceptance for drinking water make it a unique product in the flocculant family. This article covers the manufacturing process, the properties that matter, the applications, and what buyers should verify.
1. What Is PolyDADMAC?
PolyDADMAC is the polymer of the quaternary ammonium monomer diallyldimethylammonium chloride (DADMAC). Its defining feature is that the polymer chain is built from five-membered pyrrolidinium rings: during polymerization, each pair of allyl groups closes into a ring, so every repeat unit carries a permanent positive charge on the ring nitrogen. This gives PolyDADMAC an extremely high and pH-independent cationic charge density — higher than most cationic polyacrylamides — while the molecular weight stays in the low-to-medium range.
It is supplied as a clear, viscous aqueous solution, typically 20-40% active content.
2. Monomer Production: DADMAC
The monomer diallyldimethylammonium chloride is produced from dimethylamine and allyl chloride:
(CH3)2NH + 2 CH2=CH-CH2Cl → [CH2=CH-CH2-N+(CH3)2-CH2-CH=CH2] Cl-
Key points of the monomer step:
- The reaction is carried out under controlled pH and temperature to favor the tertiary amine intermediate and the final quaternization.
- Allyl chloride is the main impurity carrier: residual allyl chloride must be stripped because it is hazardous and interferes with polymerization.
- The monomer is produced as an aqueous solution and used directly in polymerization, minimizing handling of the reactive intermediate.
3. Polymerization: The Cyclopolymerization Step
DADMAC polymerizes by free-radical cyclopolymerization in aqueous solution. The mechanism is unusual: the growing radical adds across one allyl group, then the second allyl group of the same monomer closes intramolecularly to form a pyrrolidinium ring, and the chain propagates. The practical consequences:
- Nearly every monomer unit ends up in a ring — hence the very high, permanent cationic charge.
- Molecular weight is controlled by the initiator system (typically persulfate, or redox initiators), monomer concentration and temperature, reaching tens of thousands to several hundred thousand Daltons.
- The reaction is run to high conversion, and residual monomer is reduced by extended reaction and stripping.
The product is then adjusted to the target solids content (typically 20-40%), filtered, and packaged as a viscous liquid. Some grades are offered as higher-solids products or in modified (crosslinked or branched) forms for specific applications.
4. Properties and Specifications
| Parameter | Typical range | Why it matters |
|---|---|---|
| Solid content | 20-40% | Sets the effective dose per liter |
| Charge density | Very high (one cationic site per repeat unit) | Core performance parameter |
| Molecular weight | Low to medium (tens of thousands to hundreds of thousands) | Correlates with bridging ability |
| Viscosity | Grade-dependent | Indicates MW and consistency |
| pH | Typically 3-7 | Handling and compatibility |
| Residual monomer | Low (e.g. <0.5% DADMAC; allyl chloride and epichlorohydrin-type impurities must be minimal) | Safety and drinking-water approval |
For drinking-water grades, the product must meet the relevant standards (e.g. NSF/ANSI 60 in North America) with certified limits on residual monomers and impurities — the COA should show these values, not just solids and viscosity.
5. Applications
5.1 Drinking water and municipal treatment
PolyDADMAC is approved for drinking-water clarification in many countries because it is an effective primary coagulant at low dose, works over a wide pH range, and forms minimal sludge compared with inorganic coagulants. It is often used alone or as a coagulation aid before anionic PAM.
5.2 Industrial wastewater
In textile, paper, food and chemical effluents, PolyDADMAC neutralizes anionic charge and forms micro-flocs; combined with PAM it gives fast settling. Its performance is robust across pH, which suits variable industrial streams.
5.3 Papermaking
PolyDADMAC is a standard anionic trash catcher (ATC) and retention aid in paper mills: it neutralizes dissolved anionic substances and helps retain fines and fillers.
5.4 Personal care
Low-molecular-weight PolyDADMAC is used in hair conditioners and skin care as a conditioning and anti-static polymer.
6. PolyDADMAC vs Other Cationic Polymers
| Aspect | PolyDADMAC | Cationic PAM | Polyamine |
|---|---|---|---|
| Charge density | Very high, pH-independent | Medium | High |
| Molecular weight | Low to medium | High to very high | Low to medium |
| Primary mechanism | Charge neutralization | Bridging | Charge neutralization |
| Drinking-water acceptance | Widely approved | Grade-dependent | Less common |
| Typical role | Primary coagulant / ATC | Flocculant aid | Conditioner / coagulant |
In practice PolyDADMAC and polyamine are frequently interchangeable as primary coagulants; the better performer depends on the water chemistry. See our comparison of polyamine vs PAM vs PolyDADMAC for selection guidance.
7. Industry Benchmarks
The global leaders in PolyDADMAC production include SNF, Kemira, Solenis and SNF-acquired brands; their product lines define the reference points for charge density, molecular weight and purity. When comparing any PolyDADMAC (including Chinese-manufactured grades), the meaningful checks are: solids content, viscosity grade, residual monomer/impurity values, and jar-test performance on the same water.
8. How to Use PolyDADMAC
- Dilution: dilute the liquid to a workable concentration (e.g. 1-10%) for accurate metering; avoid excessive dilution tanks that promote viscosity drift.
- Dosage: typically 1-50 ppm as a primary coagulant; optimize by jar test.
- Combination: dose PolyDADMAC first, then anionic PAM as the bridging flocculant — this is the standard high-performance train.
- Compatibility: do not mix concentrated PolyDADMAC directly with anionic polymers or strong oxidizers.
9. Safety and Handling
- PolyDADMAC is low in toxicity and is approved for drinking-water use in many regions (verify the specific certification).
- Residual monomer (DADMAC, allyl chloride) is the safety-critical parameter; check the COA.
- Spills are slippery; use drip trays and spill kits. Store sealed, cool, and above the product freeze point.
10. FAQ
Is PolyDADMAC safe for drinking water?
Yes, when produced to drinking-water grade and approved under standards such as NSF/ANSI 60. Verify the certification and the residual monomer limits on the COA.
What is the difference between PolyDADMAC and cationic PAM?
PolyDADMAC has very high, permanent charge density and low-to-medium molecular weight — it neutralizes charge. Cationic PAM has higher molecular weight and bridges particles. They are complementary, not substitutes.
Why is PolyDADMAC called a “ring” polymer?
Because diallyl monomers polymerize by cyclopolymerization: each pair of allyl groups closes into a five-membered pyrrolidinium ring, giving every repeat unit a permanent positive charge.
Can PolyDADMAC replace PAC or alum?
In many clarification applications yes, alone or with PAM — usually at lower dose and with less sludge. Jar-test both on your water to compare.
11. References and Further Reading
- Peer-reviewed literature on diallyldimethylammonium chloride cyclopolymerization and PolyDADMAC applications
- NSF/ANSI 60 standard for drinking-water treatment chemicals
- Industrial technical literature from SNF, Kemira and Solenis
This article is published for industrial and technical reference by PolyblueChem. Specifications are typical industry values; always verify against the supplier’s COA and applicable standards.
PolyblueChem supplies PolyDADMAC (CAS 26062-79-3) in drinking-water and industrial grades with COA and MSDS. See also our PAM manufacturing guide and polyamine guide. Contact us for specifications and quotations.