Release of Phospholipids from Colloidal Particles to Polymeric Surfaces

Abstract

This study presents a small-scale polymerization of high molecular weight methyl methacrylate/n-butyl acrylate (MMA/n-BA) colloidal particles that are synthesized in an aqueous environment in the presence of phospholipid hydrogenated soybean phosphatidylcholine (HSPC) molecules that also serve as the particle stabilizing agents. When such particles coalesce to form polymeric films, they release phospholipids, which, in turn, form organized structures near the film-air (F-A) interface. Diffusion and mobility of phospholipid molecules are affected not only by their compatibility with colloidal particles but also by electrolyte environments of colloidal dispersions. When Na(+), K(+), and Ca(2+) counterions are added to MMA/n-BA aqueous colloidal dispersions stabilized with HSPC, and such films are coalesced, different degrees of diffusion of HSPC to the F-A interface exist, depending on the counterion, and conformational changes of HSPC result. For example, in the presence of Ca(2+), HSPC molecules collapse entropically to form random surface layers, as opposed to smaller Na(+) and K(+), which force amphiphilic HSPC ends to align preferentially parallel to the film surface. These studies show that it is possible to design stimuli-response colloidal systems triggered by chemical environments of active molecules on colloidal polymer particles.

Stimuli-Responsive Surfactant/Phospholipid Stabilized Colloidal Dispersions and Their Film Formation

“…13,14,36,37 For example, phospholipids may function as surfactants and stabilize colloidal particles while providing a self-assembled bilayer scaffold in which hydrophobic polymers may localize. Since the DLPC phospholipid may play such a role, we synthesized colloidal dispersions of MMA/nBA in the presence of SDOSS and DLPC in an aqueous phase, and their chemical structures are shown below.…”

“…Although previous studies [21][22][23][24][25][26][27] have attempted polymerization within liposome bilayers or incorporation of liposomes in colloidal dispersion synthesis and their film formation, 13 stimuli-responsive behaviors of pMMA/nBA were not addressed. For that reason, coalesced colloidal films synthesized with DLPC were analyzed, and Figure 4, traces A-D′, illustrates ATR-FTIR spectra recorded at the F-A interface using TE and TM polarizations ( Table 2).…”

“…Although the effects of elevated temperatures have been addressed above, of particular importance is the ionic strength of a colloidal dispersion. For that reason, a series of CaCl 2 solutions were prepared and added to p-MMA/nBA colloidal dispersions and the choice of Ca 2+ as a counterion was dictated by its ability to collapse or extend polymeric chains, 13 bind multiple low mol. wt.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12] Thus, continuous quests for advancing our knowledge continue by exploring new avenues. For example, it has not been realized until recently that their synthesis may be facilitated by amphiphilic bioactive molecules, such as phospholipids, 13,14 and this approach opened up new scientific and application avenues of polymeric colloidal dispersions. Although one function of these species is to serve as dispersion stabilizing agents, they may also be deliberately mobilized to designated areas within polymer matrixes during or after coalescence.…”

Effect of the Temperature of Polyurethane Wet-Casting Membrane Formation on the Physico-Mechanical Properties

“…Understanding the film formation mechanisms, in particular for thermosetting polymeric systems, has attracted considerable interests of experimentalists [11,12] as well as theoreticians [13] in recent years. Laboratory measurements provide the opportunity to examine the effect of external and internal stimuli (temperature, molecular weight, reactivity of individual components, solubility, and others) on the film formation, [14][15][16]. One example of such complexity is represented by the two-component waterborne polyurethane polymers [17], which appear to be quite sensitive to numerous external and internal stimuli such as relative humidity, miscibility of individual components, reactivity, evaporation rates, as well as rheological characteristics.…”