What is the pH range of polyamine products?
The pH range of polyamine products varies depending on their type, concentration, and application. Below is an analysis of the pH characteristics and influencing factors for common polyamine products:

1. Typical pH ranges of polyamine products

   • Polyethyleneimine (PEI): Aqueous solutions (1% concentration) typically have a pH of 8–11, exhibiting weak alkalinity due to the abundance of amino groups in the molecular chain, which readily bind protons to form ammonium salts.

   • Polydimethyldiallylammonium chloride (PDADMAC): As a cationic polyelectrolyte, its aqueous solution (10% concentration) usually has a pH of 5–7, close to neutral, though slight fluctuations may occur due to residual monomers or solvents.

   • Epichlorohydrin polyamine (e.g., FQJA21, etc.): The pH can range from 3 to 12, with acidity or alkalinity varying depending on the application environment. It is commonly used in water treatment flocculation, water sterilization, and petroleum additives, demonstrating good compatibility.

2. Key factors influencing pH

   • Concentration effect: Dilution may shift the pH closer to neutral. For example, a concentrated polyamine solution (pH 10) diluted tenfold may drop to pH 8.5.

   • Temperature and ionic strength: High temperatures or high-salt environments may weaken the protonation of amino groups, causing a slight increase in pH. For instance, PDADMAC may exhibit a 0.5-unit pH increase at 60°C.

   • Modified functional groups: Carboxylated polyamines (e.g., amphoteric polymers) can be adjusted to pH 4–6 by introducing acidic groups to achieve acid-base balance.

3. pH adaptation in application scenarios

   • Water treatment: Anionic polyamines (e.g., polyacrylamide derivatives) require a pH of 6–8 to ensure flocculation efficiency and avoid charge neutralization failure.

   • Biomedicine: Polyamines used for gene transfection are often adjusted to pH 7.4 to simulate physiological conditions and reduce cytotoxicity.

   • Paper additives: Cationic polyamines exhibit optimal fiber binding at pH 4–5, as acidic conditions enhance positive charge adsorption.

4. Measurement and adjustment recommendations

   • Precise measurement: Use a calibrated pH meter to avoid deviations caused by the viscosity of polymer solutions when using pH test strips.

   • Buffer systems: For pH-sensitive applications (e.g., drug carriers), phosphate or Tris buffers can be added to stabilize the pH within the target range.

In summary, the optimal dosage and application range should be determined through small-scale testing to establish the best formulation.