Effects of inner polarity and viscosity of amphiphilic phospholipid polymer aggregates on the solubility enhancement of poorly water-soluble drugs.

•Water-soluble amphiphilic polymers with various hydrophobic units were synthesized.•Viscosity and polarity inside the polymer aggregate were quantitatively evaluated.•Solubility of water-insoluble drugs improved in the polymer solution.•High viscosity inside of aggregate influenced maintaining of drug molecules.