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Effect of Phosphate Salt Concentration and Solution pH on the Aqueous‐Phase Homo and Copolymerization of N ‐Vinyl Pyrrolidone
Author(s) -
Borges Fernando T. P.,
Papavasiliou Georgia,
Murad Sohail,
Teymour Fouad
Publication year - 2018
Publication title -
macromolecular reaction engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.37
H-Index - 32
eISSN - 1862-8338
pISSN - 1862-832X
DOI - 10.1002/mren.201800012
Subject(s) - comonomer , monomer , chemistry , polymer chemistry , aqueous solution , copolymer , polymerization , potassium persulfate , ethylene glycol , 2 pyrrolidone , degree of polymerization , salt (chemistry) , inorganic chemistry , organic chemistry , polymer
Abstract N ‐vinyl pyrrolidone (NVP) aqueous‐phase polymerization is known to depend on the degree of hydration of the NVP molecules, resulting in an increase in the rate of propagation with decreasing monomer concentration. When potassium monophosphate and sodium hexametaphosphate are added to the monomer solution the reaction kinetics slow down, with the degree of retardation being dependent on salt‐to‐monomer concentration ratio. Using polymerization reaction models in combination with ion coordination theory, this effect can be associated with an active interaction of the ions in solution with the NVP molecules. When varying the solution pH, an optimum operating zone ranging approximately from pH 4 to pH 7 for the NVP–V‐50 2,2′‐Azobis(2‐methylpropionamidine) dihydrochloride (AAPH) system is found. Potassium persulfate is unable to initiate NVP homopolymerization. The addition of poly(ethylene glycol) diacrylate as a comonomer reduces the kinetic slow‐down caused by the addition of salts or by extreme pH and significantly increases the overall conversion rate.