Synthesis and characterization of pH‐responsive water‐dispersed nanohydrogels of cross‐linked polyacrylamide‐co‐polyacrylic acid

• Published in: Polymer engineering and science Vol. 62; no. 6; pp. 1797 - 1810
• Main Authors: Corona Rivera, Miguel Angel, Cisneros Covarrubias, Cándida Anahy, Fernández Escamilla, Víctor Vladimir Amílcar, Mendizábal Mijares, Eduardo, Pérez López, José Elías
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.06.2022; Blackwell Publishing Ltd
• Subjects: Acids; Acrylamide; Acrylics; copolymer; crosslinked; Crosslinking; Dibenzoyl peroxide; Ethylene glycol; Glycol dimethacrylates; Initiators; Methylene bisacrylamide; microemulsion; nanohydrogels; Photon correlation spectroscopy; pH‐responsive; Polyacrylamide; Polyacrylic acid; Polymerization; Potassium persulfate; Sodium salts; water‐dispersible
• ISSN: 0032-3888; 1548-2634
• DOI: 10.1002/pen.25965

In the following article, stable nanohydrogels (NHGs) of poly (acrylamide‐co‐acrylic acid) (PAAm‐co‐PAA) were synthesized by batch polymerization (BP) and semicontinuous (SP) polymerization processes. As crosslinking agents, N,N′‐methylenebisacrylamide (NMBAM) and ethylene glycol dimethacrylate (EGDMA) were used; docusate sodium salt (AOT) was used as a surfactant. The initiators employed in this work were 2,2′‐Azobis(2‐methylpropionamidine) dihydrochloride (V‐50), potassium peroxydisulfate (KPS), peroxydisulfuric acid diammonium salt (APS), and dibenzoyl peroxide (BPO). The compositions of acrylamide/acrylic acid (AAm/AA) (90/10, 70/30, 50/50, w/w), the type of a crosslinking agent, and the type of initiator on pH response of water‐dispersed NHGs were investigated. The NHGs were characterized by dynamic light scattering (DLS). Latexes with average particle size (Dpz) from 53 to 125 nm were obtained using NMBAM and EGDMA by BP polymerization processes. In contrast, NHGs synthesized by SP polymerization processes showed a Dpz ranging from 73 to 125 nm using NMBAM and EGDMA. On the other hand, the Dpz of the NHGs dispersed in water was found to be from 126 to 302 nm with NMBAM and EGDMA, respectively. Furthermore, the Dpz of the NHGs depended on the pH; higher pH values produced high Dpz values. The spherical morphology was maintained at the studied pH. pH‐responsive water‐dispersed nanohydrogels of cross‐linked polyacrylamide‐co‐polyacrylic acid. Water‐dispersed nanohydrogels maintained their stability and spherical morphology only with magnetic stirring. The average particle size of the nanohydrogels depended on the pH; higher pH values produced high average particle size values.