Thermosensitive phase transition kinetics of poly(N‐isopropylacryl amide‐co‐acrylamide) microgel aqueous dispersions

Abstract

Thermosensitive poly(N-isopropylacrylamide-co-acrylamide) microgel particles were prepared through precipitation polymerization. The diameters of the microgel particles were in the range of 220-270 nm and showed a monodispersion. The lower critical solution temperatures (LCST) of the microgel dispersions were measured by dynamic light scattering and turbidimetric analysis. The results indicated that the LCST increased with an increase of acrylamide (AAm) content in the copolymer composition. The kinetics of the thermosensitive phase transitions of the microgel particles were investigated by time-course UV-vis spectroscopy. The results indicated that the higher the content of AAm in copolymer composition, the more time is required for equilibrium deswelling and the less time required for equilibrium swelling. In addition, the time required for equilibrium deswelling decreased with an increase of the content of the microgel particles in dispersions. By contrast, the time required for equilibrium swelling increased slightly. Thus, a suitable LCST and time required for equilibrium of phase transition can be achieved by adjusting the molar ratio of the comonomers in the microgels and the content of the microgel particles in dispersions.

Catalytic reduction of 4‐nitrophenol using silver nanoparticles‐engineered poly(N‐isopropylacrylamide‐co‐acrylamide) hybrid microgels

“…The P(NIPAM‐ co ‐AAm) polymer microgels were prepared by the precipitation polymerization method as reported previously . This method is useful to obtain microgel particles of required size.…”

“…P(NIPAM‐ co ‐AAm) microgel particles were synthesized by precipitation polymerization using SDS as emulsifier and APS as initiator in aqueous medium as reported previously . For this purpose, 1.063 g of NIPAM, 0.021 g of AAm, 0.046 g of BIS and 0.05 g of SDS were dissolved in 105 ml of deionized water in a 250 mL three‐necked round‐bottom flask equipped with a condenser, a stirrer and a nitrogen gas inlet.…”

“…Khan et al used poly( N ‐isopropylacrylamide‐ co ‐methacrylic acid) microgels as microreactors for the fabrication of silver nanoparticles for catalytic applications . Synthesis and characterization of poly( N ‐isopropylacrylamide‐ co ‐acrylamide) (P(NIPAM‐ co ‐AAm)) copolymer microgels have been reported by various authors, but there is no report on the fabrication of silver nanoparticles in this system and use of this hybrid system as a catalyst. The amide groups in NIPAM and acrylamide units of P(NIPAM‐ co ‐AAm) microgels may act as ligand to stabilize the silver nanoparticles inside the network and the hybrid system can be used as a catalyst for various reactions in aqueous medium.…”

Multi‐Stimuli‐Responsive Microcapsules for Adjustable Controlled‐Release

“…Temperature‐responsive sub‐microspheres are prepared by precipitation polymerization . First, NIPAM (1.92 g), AAm (0.21 g), MBA (0.154 g), and a small amount of fluorescence dye (Polyfluor 570) are dissolved in pure water (320 mL).…”

Rheological characterization of pH‐responsive carboxymethyl starch/β‐cyclodextrin microgels

“…Microgels consist of cross‐linked polymer particles that can swell/shrink in response to changes in the local environmental conditions, such as pH , temperature , ionic strength , light , quality of solvent , or through the action of the external fields . Stimulus‐responsive microgels have received increasing attention because of their potential applications in various fields, such as drug delivery , sensors , dynamically tunable microlenses , and as templates for inorganic nanoparticle synthesis .…”