(80b) A Stimuli-Responsive, Hydrolysable Poly(Vinyl Laurate-co-Vinyl Acetate) Nanoparticle Platform for in Situ Release of Surfactants

Efficient surfactant delivery with controlled release is of great practical interest in a number of fields including oil spill remediation and oil recovery.¹ However, premature adsorption of the surfactant at various surfaces and interfaces reduces their efficiency and limits practical applications. One proposed approach to address this challenge is to encapsulate the surfactant into an appropriate host. In most systems, the immobilization relies on relatively weak interactions between the surfactant molecules and the host, which leads to premature release of the surfactant.^2,3A stimuli-responsive, sub-100nm nanoparticle platform with a hydrolysable ester side chain for in-situ generation of surfactants is demonstrated (Scheme. 1). The nanoparticles serve as a delivery vehicle as well as a precursor for the surfactant, where the slow and controlled hydrolysis of the ester groups generates carboxylic acid, which subsequently reacts with the cations in the medium to produce the surfactant. The nanoparticles were synthesized via copolymerization of vinyl-laurate and vinyl-acetate (P(VL-co-VA), 3:1 molar ratio) and stabilized with a protective poly(ethylene-glycol) (PEG) shell. The NPs are ~ 55 nm in diameter with a zeta potential of -54 mV. Hydrolysis kinetics in an accelerated, base-catalysed reaction show release of about 11 and 31% of available surfactant at 25 and 80°C, 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, and stabilizing an oil-water emulsion was investigated through contact angle measurements and laser confocal scanning microscopy (LCSM) and benchmarked to sodium laurate (SL), a commercially available surfactant representing the product derived upon hydrolysis of the nanoparticles. All these measurements demonstrate both the efficacy of the NP system for surfactant delivery and the ability of the released surfactant to alter wettability and stabilize an oil-water emulsion.

^References:

(1)Farinmade, A. et al. ACS Appl. Mater. Interfaces 2020.

(2)de Freitas, F. et al. Fuel 2019, 241.

(3)De Avila, J. et al. J. Appl. Polym. Sci. 2016.