Swelling properties of particles in amphoteric polyacrylamide dispersion

Swelling properties of amphoteric polyacrylamide (AmPAM) dispersions were investigated by measurements of apparent viscosity and particle morphology. AmPAM dispersion was prepared by dispersion polymerization in aqueous solution of ammonium sulphate. Changes of particles during dispersion polymerisation of AmPAM were simulated and compared with anionic and cationic polyacrylamide (APAM and CPAM, respectively). Sample viscosity and particle morphology were obtained using a rotational viscometer and optical microscope. It was found that small molecules or ions enter and swell particles in the AmPAM dispersion when (NH4)2SO4 concentration decreases. Similarly, monomers, including acrylamide, acrylic acid, and methacrylatoethyl trimethyl ammonium chloride, have the same effects on the AmPAM dispersion but the effect degree is different. Swelling properties of the AmPAM dispersion were different from those of the APAM and CPAM dispersions due to their different ionic nature, type of stabiliser, media, etc. Particles in the APAM or CPAM dispersions were swelled less than those in the AmPAM dispersion.

Gel Formation in Natural Rubber Latex: 2. Effect of Magnesium Ion

The effect of Mg2+ ions on the gel formation in fresh and commercial high ammonia natural rubber latices (FL-latex and commercial HA-latex) was analyzed from the gel content and 2+ content after treatment with (NH4)2SO4. The gel content of rubber from commercial HA-latex decreased significantly after (NH4)2SO4 treatment comparable to that of FL-latex. Long-storage commercial HA-latex containing 50% gel fraction showed no decrease in 2+ content after (NH4)2SO4 treatment. This gel fraction was not solubilized in toluene by the treatment of a proteolytic enzyme in latex or ethanol/toluene mixed solvent extraction of rubber. The 2+ content of rubber in long-storage commercial HA-latex, 0.005% (w/w rubber), decreased after treatment with (NH4)2SO4, while the same treatment showed little change on FL-latex, 0.035%. The toluene soluble fraction of these latices showed a decrease in the Mn value with an increase in the (NH4)2SO4 concentration. The gel content of FL- and HA-lattices increased with an increasing storage period in the presence and absence of (NH4)2SO4. The initial rate of increase in the gel content was slow in the case of FL-latex. These findings indicate that the gel fraction in HA-latex is partly formed by ionic crosslinks caused by 2+ ions. Whereas, the gel phase in long-storage commercial HA-latex is presumed to be a hard gel predominantly formed by covalent bonding.

A novel preparative method for the isolation of avidin and riboflavin-binding glycoprotein from chicken egg-white by the use of high-performance liquid chromatography

A method for the rapid preparative isolation of highly purified avidin using h.p.l.c. on a powerful cation-exchanger TSK SP-5PW column has been developed. The method is based on the following properties of avidin: solubility at a high (NH4)2SO4 concentration, stability and relatively low solubility in organic solvents, as well as the strongly cationic nature of the molecule. Riboflavin-binding glycoprotein may be isolated as by-product.