Chitosan and polyacrylic acid (PAA) both have weak, short-lasting bioadhesive properties; therefore, a hybrid particle composed of a chitosan derivative and PAA could be used as a new bioadhesive agent. Using simultaneous in-situ monitoring with a multidetection system, N-carboxymethyl chitosan was ionically bonded to acrylic acid and then polymerized using potassium persulphate as the initiator (N-CMCA-Dh of 165 nm). The PAA on N-CMCA was crosslinked using N,N-methylene-bisacrylamide (N-CMCAC-Dh of 141 nm). During polymerization, the solution developed a milky white appearance, and polymerization kinetics was determined to be 3.2 × 10?3 ± 4.0 × 10?6 mmol/min. The reaction for PAA alone was 1.7 times faster than that of the hybrid system. The particles showed an increase in thermal stability and reduction of thermal-mass loss compared with the N-CMC alone. The N-CMCAC particles showed the highest bioadhesion onto the stomach. The gastroprotection index of N-CMChAC particles against ethanol/HCl-induced ulcers in mice was 68.2 ± 6.4%. Similar results were observed for omeprazole (74.2 ± 5.3%). The particles obtained in this work have potential for use in drug delivery to the stomach, perhaps to aid in treating ulceration and inflammation, and can be used as a system for the prevention of ethanol-induced ulcers.