Polyelectrolyte complex nanoparticles from N‐carboxyethylchitosan and polycationic double hydrophilic diblock copolymers

For the first time, the polyelectrolyte complex (PEC) formation tool was used for preparation of core‐shell nanoparticles form the natural polyampholyte N ‐carboxyethylchitosan (CECh) and weak polycationic (protonated) polyoxyethylene‐ b ‐poly[2‐(dimethyl‐amino)ethyl methacrylate] (POE‐ b ‐PDMAEMA) diblock copolymers. The performed dynamic light scattering analyses revealed that nanoparticles with a PEC core and a POE shell could be formed at mixing ratio between the oppositely charged groups equal to 1/1 depending on CECh molar mass, polymerization degree of PDMAEMA block and ionic strength. The results were confirmed by the performed AFM and cryo‐TEM analyses. When high molar mass CECh was used, core‐shell nanoparticles were obtained with the diblock copolymer of the shortest PDMAEMA block at ionic strength ( I ) of 0.01. At ionic strength value close to the physiological one ( I = 0.1) secondary aggregation occurred. Spherical nanoparticles at I = 0.1 were obtained upon lowering the CECh molar mass. Depending on the polymer partners and medium parameters the size of the obtained particles varied from 60 to 600 nm. The X‐ray photoelectron spectra evidenced the hydrophilic POE‐block shell—coacervate CECh/PDMAEMA‐block core structure. The nanoparticles are stable in a rather narrow pH range around 7.0, thus revealing the high pH‐sensitivity of the obtained core‐shell particles.