Cross-Linked Poly(acrylic acid) Microgels from Precipitation Polymerization

Abstract

Cross-linked poly(acrylic acid) microgels were prepared via thermally initiated free-radical precipitation polymerization in a binary organic solvent. N,N 0 -Methylenebisacrylamide (MBA) and 2,2 0 -azobisisobutyronitrile were used as cross-linker and initiator, respectively. The effect of (MAB) concentration on different features of sample (i.e., spectral characteristics, glass transition temperature, equilibrium swelling, gel content and rheological properties) was investigated. The Flory-Rehner equation and rubber elasticity theory were used to discuss the network structure of polymer. Apparent and rotational viscosities were used to determine the optimal cross-linker concentration. The sample maximum with value of viscosity was obtained using 1.6 mmol/L of the cross-linker. In addition the m and n parameter of Ostwald equation were investigated as well.

Superabsorbent polymer: application in natural rubber for making rubber roofing sheets

“…The viscosity of NaPA decreased with the increasing content of the cross-linker agent. Upon increasing the crosslinking, the spaces of the cells in the network structure of the hydrogel decrease and become limited, therefore, viscosity decreases (Es-haghi et al , 2010). So, the amounts of water absorbed by each cell become limited.…”

Synthesis of cross-linked poly(acrylic acid) nanogels in an aqueous environment using precipitation polymerization: unusually high volume change

“…So, the nanogel swelled more than 4000 times when the environment was changed from acidic to basic. This number can be compared with the swelling/shrinking ratio of the nanogels obtained in the traditional organic medium, where it was limited to the range of 7–25 [30,31,49,50]. The reason for this difference could be the presence of organic impurities in the gels.…”

Large-scale synthesis and characterization of magnetic poly(acrylic acid) nanogels via miniemulsion polymerization

“…1 Stimuli-responsive nanogels undergo abrupt changes in volume in response to external stimuli, such as temperature, 2 pH, 3 ionic strength, 4 and changes in solvent composition, 5 which have promising applications in drug delivery, tissue engineering, biosensors, catalytic carriers, optical and chemical separation. 8 However, this will introduce a large quantity of organic solvent as the continuous phase. Because acrylic acid is a water-soluble monomer with high reaction activity and PAA is soluble in polar solvents, it is hard to prepare PAA nanogels directly by conventional emulsion polymerization and solution polymerization methods.…”

“…6,7 Polyacrylic acid (PAA) nanogels have good biocompatibility, fast responsive properties, and a large specic surface area, and remain one of the most ideal candidates in the above applications. 8 Therefore, the large-scale and facile preparation of PAA nanogels still remains to be solved. An alternative methodology is involved using inverse emulsion polymerization or inverse suspension polymerization.…”

“…An alternative methodology is involved using inverse emulsion polymerization or inverse suspension polymerization. 8 However, this will introduce a large quantity of organic solvent as the continuous phase. El-Rehim 9 fabricated PAA nanogels by gamma radiation-induced polymerization of acrylic acid (AA) in an aqueous solution of polyvinylpyrrolidone (PVP) as a template polymer, but this method required g-rays generated from a 60 Co source and was conducted at a low concentration in the dilute solution (total concentration of 1.5%), resulting in very low yields of nanogels.…”