Molecular and colloid chemical characterization

Analyte

• Suitable for the method are polymers or nanoparticles that are soluble or dispersible in aqueous media or organic solvents. The required sample quantity is 100-500 mg. The method covers approximately the molar mass range from 10⁴ to 10⁵.

Equipment

• GONOTEC OSMOMAT 090 membrane osmometer
  
• Membranes: cellulose triacetate (cut-off 5000, 10000 and 20000 g/mol), regenerated cellulose (cut-off 20000 g/mol)
• Solvents: water and aqueous salt solutions as well as organic solvents like tetrahydrofuran, toluene, chloroform etc.

Target

• Measurement of the osmotic pressure p as a function of the polymer concentration and extrapolation of the reduced osmotic pressure to the concentration zero
  • Numerical average molar mass M_n and 2^nd virial coefficient A_2,o

Application

• Example: Poly-DADMAC standard materials (see PDF)

Methods of comparison and supplementation

• Aqueous size exclusion chromatography (M_n; M_W; D)
• Organic size exclusion chromatography
  
• Static light scattering (M_W; R_Z; A₂) 
• Analytical ultracentrifugation (M_Z; D)
  
• Differential refractometry (dn/dc)
• Dynamic light scattering (dH)
• Vapor pressure osmometry (M_n)