title: Swelling kinetics of microgels embedded in a polyacrylamide hydrogel matrix.
abstract: Composite hydrogels--macroscopic hydrogels with embedded microgel particles--are expected to respond to external stimuli quickly because microgels swell much faster than bulky gels. In this work, the kinetics of the pH-induced swelling of a composite hydrogel are studied using turbidity measurements. The embedded microgel is a pH- and thermosensitive poly(N-isopropylacrylamide-co-acrylic acid) microgel and the hydrogel matrix is polyacrylamide. A rapid pH-induced swelling of the embedded microgel particles is observed, confirming that composite hydrogels respond faster than ordinary hydrogels. However, compared with the free microgels, the swelling of the embedded microgel is much slower. Diffusion of OH(-) into the composite hydrogel film is identified as the main reason for the slow swelling of the embedded microgel particles, as the time of the pH-induced swelling of this film is comparable to that of OH(-) diffusion into the film. The composition of the hydrogel matrix does not significantly change the characteristic swelling time of the composite hydrogel film. However, the swelling pattern of the film changes with composition of the hydrogel matrix.
authors.affiliation: State Key Laboratory of Medicinal Chemical Biology and Key Laboratory of Functional Polymer Materials, Institute of Polymer Chemistry, College of Chemistry, Nankai University; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300071 (P. R. China).
authors.forename: Na
authors.initials: N
authors.lastname: Huang
authors.forename: Ying
authors.initials: Y
authors.lastname: Guan
authors.forename: X X
authors.initials: XX
authors.lastname: Zhu
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000178:Acrylamides / Q000737:chemistry; D000180:Acrylic Resins / Q000737:chemistry*; D004058:Diffusion; D020100:Hydrogels / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D011108:Polymers / Q000737:chemistry
chemical_list: D000178:Acrylamides; D000180:Acrylic Resins; D020100:Hydrogels; C090629:N-isopropylacrylamide-acrylic acid copolymer; D011108:Polymers; C016680:polyacrylamide gels
keywords: hydrogel; kinetics; microgel; stimuli-responsive gels; swelling