DEVELOPMENT OF A STIMULI-RESPONSIVE, HYDROLYSABLE POLY(VINYL LAURATE-co-VINYL ACETATE) NANOPARTICLE PLATFORM FOR THE SLOW AND CONTROLLED IN-SITU RELEASE OF SURFACTANTS
Efficient surfactant delivery with controlled release is of great practical interest in various fields including oil spill remediation and oil recovery.1–3 Premature adsorption of surfactants at various surfaces and interfaces reduces their efficiency and limits practical applications. To alleviate this challenge, nanoencapsulation methods have been proposed and, in most systems, the immobilization relies on relatively weak, noncovalent interactions between the surfactant molecules and the host, which leads to premature release.4–6 In this study, a stimuli-responsive, sub-100nm nanoparticle platform with a hydrolysable ester side chain for in-situ generation of surfactants is demonstrated. The nanoparticles serve as a delivery vehicle as well as a precursor for the surfactant derived from the pendant ester groups. The nanoparticles, ~ 55 nm in diameter with a zeta potential of -54 mV, were synthesized via copolymerization of vinyl-laurate and vinyl-acetate (p-(VL-co-VA), 3:1 molar ratio) as the core and stabilized with a protective poly(ethylene-glycol) (PEG) shell. Hydrolysis kinetics in an accelerated, base-catalysed reaction show release of about 11 and 31% of available surfactant in DI water at 25 and 80C, respectively. The corresponding values in saline water are 22 and 76%. The efficiency of the released surfactant in reducing the interfacial tension (IFT), altering wettability, stabilizing an oil-water emulsion, and generation of foam was investigated through spinning drop tensiometer (SDT) analysis, contact angle measurements, laser confocal scanning microscopy (LCSM) imaging and dynamic foamability assessment, respectively. The performance was benchmarked to sodium laurate (SL), a commercially available surfactant. The system was further investigated for targeted delivery of surfactants to the oil phase by grafting poly(glycidyl methacrylate), PGMA, brush on the surface. The collective findings of the study demonstrate both the efficacy of the NP system to produce surfactants in-situ and the ability to manipulate and control various interfacial phenomena including wettability, emulsions, and foams.
Emulsions; Foam; Nanoparticles; Polymers; Surfactants; Wettability
Giannelis, Emmanuel P.
Estroff, Lara A.
Materials Science and Engineering
M.S., Materials Science and Engineering
Master of Science
dissertation or thesis