Surface Activity at the Air-Water Interface and Self-Stratification of Silica Nanoparticles Functionalized with Tri-Methoxy Poly(ethylene glycol) Silane

<p>Aggregated silica nanoparticles (SNPs) have been functionalized with tri-methoxy poly(ethylene glycol) silane (mPEG silane), end-capped with a methyl group. This functionalization imparts surface activity at the air-water interface due to the hydrophobic nature of the end-capped methyl group. To determine the surface coverage of silane on the particle surface, solution-state ¹H-NMR spectroscopy was utilized for characterization, and surface tension measurements were conducted to assess their tension-lowering ability. Solutions containing 10 wt% of the functionalized SNPs reduced the quasi-static surface tension to approximately 53 mN/m, regardless of the amount of reacted mPEG silane. However, the quantification of mPEG silane influenced the kinetics of surface tension reduction. The degree of aggregation between unmodified and functionalized SNPs was examined using dynamic light scattering (DLS) and transmission electron microscopy (TEM). TEM revealed fractally shaped aggregates 80-100 nm in size, consistent with DLS results. Interfacial dilatational rheology at the air-water interface with adsorbed particles was characterized using pendant drop tensiometry. A surrogate latex formulation was prepared to test the self-stratification of functionalized SNPs, consisting of 500 nm polystyrene spheres in aqueous suspension without surfactant. Films were formed on mica substrates and imaged in ScanAsyst mode using atomic force microscopy (AFM). The images showed a hexagonal array of polystyrene particles in the absence of the functionalized SNPs. However, when the functionalized SNPs were added, the surface was dominated by these nanoparticles, with the polystyrene particles recessed deeper into the interfacial layer. These results provide evidence that hydrophobic silica nanoparticles in a latex suspension can preferentially adsorb to the surface of the drying coat, leaving a nanotextured hydrophobic surface with potentially enhanced dirt resistance and self-cleaning ability.</p>

Name thesis:degree_name

Master of Engineering (M.E.)

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Chemical Engineering

Year dc:date.available

2024

Author dc:creator

• Jung, Hyeongoo

Contributors dc:contributor

• Charles Maldarelli

• Nanoparticle
• Surface tension
• Interfacial phenomena
• Self-Stratification
• Chemical Engineering

Repository record dc:identifier

https://academicworks.cuny.edu/cc_etds_theses/1300

OAI identifier oai:identifier

oai:academicworks.cuny.edu:cc_etds_theses-2243