The
escalation in industrial demand and environmental concerns
has necessitated the development of high-performance nanoadditivesthe
driving force behind advanced lubricating oil used in engineered systems.
Herein, dialkyl dithiophosphate (DDP)-functionalized gallium-based
liquid-metal (GLM) nanodropletsDDP@GLMs, were prepared with
an average size of about 178 nm and used as effective lubricant additives
for tribological properties such as friction and wear reduction. Polydopamine-coated
GLM nanodroplets (PDA@GLMs) can simply be prepared by means of sonication
of liquid metal in bulk in Tris aqueous solution of dopamine, followed
by modification by a commercial lubricating additive (DDP) via Michael
addition. The DDP@GLMs exhibited exceptional stability in poly(alphaolefin)
(PAO) base oil and remained stable for more than 5 days. The tribological
properties of DDP@GLM additives were evaluated under varied conditions.
It can be seen that the as-obtained DDP@GLMs demonstrated remarkable
friction reduction and wear resistance abilities while operating as
lubricating additives. The high load-carrying property is seen reaching
a value as high as 1050 N with the frictional coefficient befalling
less than 0.1 and the corresponding wear volume loss being decreased
by 96%. The tribological properties seem attributable to the formation
of a protective film (oxides of Ga, In, Fe, ferrous sulfide, and iron
phosphate) on the interfaces of friction pairs. This study establishes
a reliable basis for simple preparation of functional GLM nanodroplets
and the manner of their implementation as lubrication additives.
In the present work, high-thickness zwitterionic polymer brushes based on imidazolium salts were successfully grafted via a novel subsurface-initiated ringopening metathesis polymerization (subsurface-initiated ROMP) from polydimethylsiloxane (PDMS), and their antifouling performance was evaluated in detail. First, an initiator-embedded PDMS was prepared via copolymerization of PDMS prepolymer and ROMP initiator, and then zwitterionic polymer brushes were grafted via subsurfaceinitiated ROMP from surface to subsurface of the PDMS due to the implanted ROMP initiator. Results from a series of characterization methods such as infrared spectroscopy, X-ray photoelectron spectroscopy, contact angle, and atomic force microscopy proved the zwitterionic polymer brushes' successful grafting. The grafting thickness of zwitterionic polymer brushes via subsurface-initiated ROMP can reach the micron scale, and the as-prepared zwitterionic polymer based surfaces showed good lubricating properties compared to traditional surfaceinitiated ROMP, which hints that polymer brushes can be grafted not only on the surface but also on the subsurface of PDMS. The protein adhesion test and biofouling assay of zwitterionic polymer brushes were tested in the laboratory, and the results indicated that the zwitterionic polymer-functionalized PDMS can effectively resist the adhesion of bovine serum albumin and algae (Porphyridium and Dunaliella) and has good anti-bacterial activity against both Escherichia coli and Staphylococcus aureus.
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