Stable polymeric nanoparticles were prepared by self-assembly of poly(ethylacrylic acid) homopolymers. The mechanism of the self-assembly is based on heating a solution of thermoresponsive partially charged PEA with subsequent stabilization of particles by hydrogen bonds between polymer chains. Thermoresponsivity is tuned by the polymer degree of ionization. A deeper insight into the mechanism of the self-assembly is brought by a combination of static, dynamic, and electrophoretic light scattering with calorimetry and FTIR spectroscopy. The Full irreversibility and the width of the transition as seen by scattering methods are confirmed also by differential scanning calorimetry. As revealed by FTIR measurements. the irreversibility of the nanoparticle formation is achieved by their stabilization via hydrogen bonds, mainly COOH center dot center dot center dot COO-. The mechanism of the stabilization of PEA nanoparticles comprised of charged chains by a concerted action of hydrophobic and hydrogen bond interactions reminds of the situation in globular proteins. Similarly to globular proteins. PEA nanoparticles can be denatured by urea.