Interfacial properties of cellulose nanocrystals (CNC) and surfactants were studied in high ionic strength (I) brines and correlated to the stability of dodecane/brine Pickering emulsions. Bis-(2-hydroxyethyl) cocoalkylamine (CAA), dodecyltrimethylammonium bromide (DTAB), and octyl-β-d-glucopyranoside (OGP) were adsorbed onto CNC in American Petroleum Institute (API) brine (I = 1.9 M) and synthetic seawater (SSW), with I = 0.65 M. Raman spectroscopy indicated that hydroxyl groups on the CNC surface interact with all three surfactants in high ionic strength media. Ionic interactions still play a role at the very large ionic strengths studied herein. Despite all surfactants adsorbing onto CNC, only the surface tension of CAA solutions in both brines was increased by the addition of 0.5 wt % CNC. The effect was much more prominent in API than in SSW. Contact angle measurements indicated that CAA increased the wettability of CNC by both brines in dodecane; DTAB, on the other hand, decreased wettability. Emulsion stability studies revealed that ionic strength, wettability, adsorption energy, and oil content strongly affect emulsion stability, more so than surfactant adsorption. In API, CNC aggregates alone stabilized the emulsions better compared to samples with additional emulsifiers; the same was true in SSW for oil contents below 50% v/v. For oil contents above 50% v/v in SSW, CAA was either detrimental or failed to improve emulsion stability. On the other hand, DTAB increased the stability of dodecane in SSW emulsions. Emulsions stable for over 21 months were prepared with oil contents of 75% v/v. The adsorption of CAA onto CNC limits the migration of both CNC and CAA to the dodecane/brine interface, while DTAB adsorption has the opposite effect.

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Light‐sensitive drug delivery systems are considered ideal for applications in the biomedical fields for their ability to release the payload in an on‐demand spatiotemporal controlled manner through the manipulation of the light source. Among the broad radiation spectrum, near infrared (NIR) light is considered advantageous compared to UV and visible light, due to its inherently lower photodamage to normal tissues and deeper penetration to lesion areas. In this study, we report a successful synthesis of a polymer capable of undergoing partial degradation upon irradiation with NIR light by conjugating 10‐N‐carbamoyl linkage methylene blue (MB) moiety, a NIR photocleavable ligand, with polyethylene glycol (PEG). Through effective coupling of MB, a hydrophobic moiety, to the hydrophilic PEG molecule, an amphiphilic polymer was synthesized, as demonstrated by a lowered surface tension (55 mN/m at 0.1% wt/vol). Subsequently, photo‐induced reversal of surface activity associated with self‐assembled structure disruption, was displayed by surface tension measurements, size distribution analysis, and burst release profile of paclitaxel (PTX) from polymeric micelles upon the exposure to NIR irradiation.