Preparation and properties of amphoteric polyacrylamide by seeded dispersion polymerization in ammonium sulfate solution

Preparation of novel amphoteric polyacrylamide and its synergistic retention with cationic polymers

A novel amphoteric polyacrylamide (PDAA) was prepared by inverse emulsion polymerization. The influence of its cationic degree and molecular weight on retention property was discussed. Then, the chemical structure and micromorphology of the obtained PDAA were characterized by Fourier infrared spectrum (FTIR), NMR hydrogen spectrum (1H NMR), gel permeation chromatography (GPC), and scanning electron microscope (SEM). Finally, the synergistic retention effects of polydimethyldiallylammonium chloride (PDADMAC), cationic starch (CS), cationic guar gum (CHPG), cationic chitosan (CTS), and polyamine (PA) on the novel PDAA were investigated. The results showed that the optimum cationic degree and molecular weight of PDAA were 25% and 4 million, respectively. The chemical structure of PDAA was confirmed by FTIR, 1H NMR, and GPC. SEM showed that the particle size of PDAA was between 150 and 600 nm, and the particles were very stable because no broken particles were found. In addition, most of the five cationic polymers have good synergistic retention effect on PDAA, and the order of synergistic effect was PDAA/PDADMAC > PDAA/CTS > PDAA/CS > PDAA/CHPG > PDAA/PA.

Zwitterionic Cellulose Nanofibrils with High Salt Sensitivity and Tolerance

To improve the salt tolerance/sensitivity of cellulose nanofibrils (CNFs), zwitterionic cellulose nanofibrils (ZCNFs) were prepared from softwood bleached kraft pulp fibers via a sequential process of anionic modification with 2,2,6,6-tetramethylepiperidin-1-oxyl (TEMPO)-mediated oxidation, cationic modification with (2,3-epoxypropyl) trimethylammonium chloride (EPTMAC), and high-pressure homogenization. To produce ZCNFs with different contents of cation group, EPTMAC loadings of 0.15 to 1.15 g/g fiber were explored during cationization. The obtained ZCNFs were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectra (XPS), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and rheological measurements. The salt tolerance of the ZCNFs was investigated by adding mixed salts into the ZCNF dispersions. The results demonstrated that the ZCNFs with both anionic and cationic charges were produced. Compared with the TEMPO-mediated oxidized cellulose nanofibrils (TOCNFs), the ZCNFs exhibited an excellent "salt-thickening" behavior under the studied salt concentrations (2-24% w/w). Moreover, increasing the content of the cation group increased the salt tolerance/sensitivity of ZCNFs. This work demonstrated that introducing cationic charges to the anionic charged TOCNFs imparts the produced ZCNFs with excellent salt sensitivity and tolerance, which could expand the application of nanocellulose in oil recovery or wastewater treatment.

A novel and controllable route for preparing high solid-content and low-viscosity poly(acrylamide-co-acrylic acid) aqueous latex dispersions

High solid-content and low-viscosity poly(acrylamide-co-acrylic acid) aqueous latex dispersions were obtained through a novel strategy, which involves swelling followed by diffusion and redox initialized polymerization inside the seed particle.