Dependence of Particle Size on pH, Electrolyte, and Time for Expandable Copolymer Latexes by Hydrodynamic Fingerprinting

Abstract

A new technique, hydrodynamic fingerprinting, is presented for the characterization and study of expandable latex dispersions on the basis of their hydrodynamic behavior. In the hydrodynamic fingerprint the hydrodynamic size as measured by photon correlation spectroscopy is presented as a function of two colloidal state variables simultaneously, pH and pλ, where pλ is the logarithm of the conductivity. Hydrodynamic fingerprinting is applied to two methyl methacrylate-ethyl acrylate latexes, one of which contains 2% acrylic acid. It is shown that hydrodynamic fingerprinting can be used to measure expansion properties of colloids, time effects in colloidal solutions, colloidal stability, and the differences in chemistry of the colloid-solution interface. Experimental SectionMaterials. The copolymer latexes were prepared at Union Carbide. The acidic latex, designated latex A170, is an ethyl acrylate, methyl methacrylate, acrylic acid copolymer latex. The composition of the monomer feed in the latex polymerization was 40 parts methyl methacrylate, 58 parts ethyl acrylate, and 2 parts acrylic acid, which was fed over the last half of the feed. Monomer was fed continuously into the reaction vessel at 80 °C in the presence of ammonium persulfate initiator and Aerosol OT. 17 The mean particle diameter for latex A170, determined with the Microtrac UPA particle sizer, was 170 nm, with a standard deviation in the particle size distribution of 23 nm. The Microtrac measurements were made on the concentrated form of the latex, for which the solids weight fraction was 0.37 and the pH was approximately 3.Latex NA143 is the acid-free counterpart of latex A170. The polymerization procedure was the same as that used for latex A170, except that the composition of the monomer feed was 40 parts methyl methacrylate and 60 parts ethyl acrylate. No acrylic acid was present. Latex NA143 was found by the Microtrac UPA to be 143 nm in diameter with a standard deviation of 19 nm. The measurement was made at a pH of 3 and a solids weight fraction of 0.36. Latex NA143 was prepared as a control and was expected to be of constant size.All supporting solutions used for sample preparations were aqueous. The water to be used for solution preparations was distilled twice, the second time in an all glass apparatus. All of the salts were recrystallized from filtered aqueous solutions. The salts were KCl, LiCl, and NaCl, the acid was HCl, and the bases used were KOH, NaOH, and LiOH.

Carboxylated core–shell particles: I. A system showing hindered swelling behavior

“…The term brush denotes that the grafting density r (number of grafted chains per unit area) is high enough so that the chains are enforced to take a stretched conformation [1]. These systems have received a great deal of attention in recent years [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Polyelectrolyte brushes are interesting from the point of view of fundamental as well as of applied research.…”

“…On the other hand, the complex experimental behavior of these spherical polyelectrolyte brushes is usually showed as a fingerprint for each system in particular [15]. This fingerprint is a 3D plot of the hydrodynamic size vs. solution pH and pk (k is the electrical conductivity of the medium).…”

Carboxylated Polysaccharides Decorated with Ultrasmall Magnetic Nanoparticles with Antibacterial and MRI Properties

“…The hydrodynamic size values for a certain sample, obtained by dynamic light scattering, are larger than those obtained from transmission electron microscopy technique; the hydrodynamic size can change with the suspension condition . In the case of our samples, the size determined by DLS for the CoxNP1 has been found to be 129 nm, whereas the size of the PoxNP1 nanoparticles was larger, that is, 290 nm.…”

Adsorption of Sodium Dodecyl Sulfate to Colloidal Titanium Dioxide: An Electrophoretic Fingerprinting Investigation

“…Fingerprinting (6)(7)(8), a means of representing colloidal variables as a function of pH and the log of the conductivity, pλ, was conceived at the University of Massachusetts in 1986. The conductivity is expressed in units of microsiemens per centimeter, which is convenient as it places the zero close to the conductivity of pure distilled water.…”

“…The conductivity is expressed in units of microsiemens per centimeter, which is convenient as it places the zero close to the conductivity of pure distilled water. Rowell and co-workers (6)(7)(8) have suggested that the solution conductivity is the experimental analogue to the ionic strength. It has the advantage of being a measured quantity that does not depend on a knowledge of the ions present in solution.…”