Polystyrene nanoparticles in the presence of (ethylene oxide)₁₃(propylene oxide)₃₀(ethylene oxide)₁₃, N,N-dimethyloctylamine-N-oxide and their mixtures. A calorimetric and dynamic light scattering study

Abstract

Polystyrene nanoparticles were synthesized by emulsion polymerization of styrene. They were functionalized using the conventional surfactant N,N-dimethyloctylamine-N-oxide (ODAO), the tri-block copolymer (ethylene oxide)(13)(propylene oxide)(30)(ethylene oxide)(13) (L64) and their mixtures. To this purpose, dynamic light scattering and calorimetric experiments were carried out and provided information consistent to each other. The L64 adsorption is Langmuir-type in the copolymer dilute regime and generates complex structures at larger concentrations. In the region where ODAO is in the unimeric state, the adsorption process is cooperative leading to hemi-micelle formation at the polystyrene nanoparticle/water interface. In the concentrated region (above the critical micellar concentration), ODAO forms micelles which interact with the solid substrate most likely through ion-dipole forces. The ODAO addition to the dispersion containing polystyrene particles already wrapped by L64 creates an ODAO thickness around the dispersed particles the size of which is equal to that in the absence of the copolymer, but is built at much lower concentrations. A plausible interpretation of this behavior is that the adsorbed L64 confers to the nanoparticles surface novel properties which enhance the attractive forces with the ODAO molecules.

Aqueous Laponite Clay Dispersions in the Presence of Poly(ethylene oxide) or Poly(propylene oxide) Oligomers and their Triblock Copolymers

“…The same conclusion can be drawn for both L35 and 10R5 which, in turn, possess the same ∆R values (1 nm). This result is opposite to the finding 31 for the adsorption of L64 on polystyrene nanoparticles for which the experimental ∆R (10 nm) is larger than that calculated according to the random coil configuration (4.4 nm). In this case, the number of sites of interactions is low and the copolymer is extended into the aqueous phase.…”

Aqueous phase/nanoparticles interface: hydroxypropyl cellulose adsorption and desorption triggered by temperature and inorganic salts

“…27,39 Differently, spherical nanoparticles lead to a hairy adsorbed polymer layer and in this case the adsorption was entropy driven. 40 Temperature change affects the energetics of the adsorption process but the entropy-enthalpy compensation generates little changes in the DG ads with temperature. Concerning this aspect it is noteworthy to highlight the importance of direct measurements of thermodynamic properties.…”

Temperature-controlled poly(propylene) glycol hydrophobicity on the formation of inclusion complexes with modified cyclodextrins. A DSC and ITC study

“…It is well established that calorimetry is a powerful technique to characterize intermolecular interactions and to determine the complete energetics (standard free energy, enthalpy and entropy) of associative processes in solution (adsorption on solids, [23][24][25] inclusion processes, 26,27 self-assembling, 28-30 etc.). We are now assisting to the replacement of the microcalorimetry on behalf of the ITC, which appears rather versatile because it evidences weak as well as strong interactions quickly and accurately and, furthermore, needs very small amounts of materials.…”