CelebratingSoft Matter's 10th Anniversary: Influencing the charge of poly(methyl methacrylate) latexes in nonpolar solvents

Abstract

Sterically-stabilized poly(methyl methacrylate) (PMMA) latexes dispersed in nonpolar solvents are a classic, well-studied system in colloid science. This is because they can easily be synthesized with a narrow size distribution and because they interact essentially as hard spheres. These PMMA latexes can be charged using several methods (by adding surfactants, incorporating ionizable groups, or dispersing in autoionizable solvents), and due to the low relative permittivity of the solvents (εr ≈ 2 for alkanes to εr ≈ 8 for halogenated solvents), the charges have long-range interactions. The number of studies of these PMMA particles as charged species has increased over the past ten years, after few studies immediately following their discovery. A large number of variations in both the physical and chemical properties of the system (size, concentration, surfactant type, or solvent, as a few examples) have been studied by many groups. By considering the literature on these particles as a whole, it is possible to determine the variables that have an effect on the charge of particles. An understanding of the process of charge formation will add to understanding how to control charge in nonaqueous solvents as well as make it possible to develop improved technologically relevant applications for charged polymer nanoparticles.

The internal structure of poly(methyl methacrylate) latexes in nonpolar solvents

“…As an example, when using these particles to study charged sphere interactions or the depletion potential, autoionizable solvents [42,43], charging agents [10,[46][47][48]50], or non-adsorbing polymers [45] are added. Introducing additional solutes to the dispersions further complicates an already complex system.…”

“…This has enabled many enlightening studies into phenomena such as hard-sphere colloidal crystallization [29-33, 40, 41], ionic crystallization [34,42,43], depletion-induced gelation and glass formation [44,45], and the interaction of charges in low dielectric media [10,[46][47][48][49][50].…”

“…Dispersions of colloids in nonpolar solvents are prevalent in soft matter nanoscience [1][2][3][4][5][6][7][8][9][10][11][12]. The significance of such dispersions can be appreciated by considering the many various industrial sectors that make use of them, which include petrochemicals [13], lubricants [7,14,15], reprography [4,5], inkjet printing [5], magnetic recording media [4], rheological fluids [16,17], and electronic displays [18][19][20][21].…”

Soluto-inertial phenomena: Designing long-range, long-lasting, surface-specific interactions in suspensions

“…Of colloidal interactions, electrostatics have the longest range, yet they are fundamentally limited by the (Debye) length scale over which the surface charge is screened by electrolyte ions (10,24,27): The largest possible Debye screening length in room temperature aqueous suspensions is ≤1 μm, and more typically between 1 nm and 100 nm. Longer screening lengths are possible in nonpolar solvents, but control and stabilization of nonaqueous charges and suspensions remains challenging (29)(30)(31)(32). Magnetic and hydrodynamic interactions are unscreened and can extend to longer ranges (10,27) but are essentially indiscriminate and less easily controlled, designed, or tuned.…”

Sulfosuccinate and Sulfocarballylate Surfactants As Charge Control Additives in Nonpolar Solvents

“…1 The surfactants studied so far are completely different molecules, and there have been few attempts in the literature at making systematic variations. 2 Given the importance of charging in nonaqueous solvents, 3 for applications as diverse as petroleum safety, 4 printer and photocopier toners, 5 and electrophoretic electronic paper displays, 6,7 there is a need for understanding how the structure of surfactant charging agents can be related to their effectiveness. In this paper, changes to the hydrophobic (or solvophilic) portion of the surfactant molecule will be considered.…”