Dual functional star polymers for lubricants

Cosimbescu, Lelia; Robinson, Joshua W.; Zhou, Yan; Qu, Jun

doi:10.1039/c6ra17461b

Cited by 26 publications

(33 citation statements)

References 24 publications

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“…Interestingly, although analog 7 has a higher molecular weight than analog 5, its VI is in fact lower, indicative of the significant effect of polymer topology on viscosity behavior. Based on our previous studies with other classes of VMs, [17] introduction of polar units lower VI values.…”

Section: Resultsmentioning

confidence: 86%

Highly branched polyethylenes as lubricant viscosity and friction modifiers

Robinson

Zhou

et al. 2016

Reactive and Functional Polymers

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A series of highly branched polyethylenes (BPE) were prepared and evaluated in a Group I base oil as potential viscosity and friction modifiers. The performance of these BPEs supports the expected dual functionality. Changes in polarity, topology, and molecular weight of the BPEs showed significant effects on the lubricants' performance with respect to viscosity index and friction reduction. This study provides scientific insights into polymer design for future lubricant development activities.

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Section: Resultsmentioning

confidence: 86%

Highly branched polyethylenes as lubricant viscosity and friction modifiers

Robinson

Zhou

et al. 2016

Reactive and Functional Polymers

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“…However, while VMs typically complement the function of other additives, they can also adversely affect the performance of some dispersants or corrosion inhibitors, possibly because these additives compete for surface adsorption sites [102]. Current ongoing research is focused on the design of novel VMs that can either complement or potentially replace traditional friction modifiers in lubricant formulations [99,103].…”

Section: Vms As Multi-functional Additivesmentioning

confidence: 99%

Review of Viscosity Modifier Lubricant Additives

2018

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This article reviews viscosity modifiers, additives that increase the viscosity of lubricating oils. Viscosity modifiers are high molecular weight polymers whose functionality is derived from their thickening efficiency, viscosity-temperature relationship, and shear stability. There are now many different additive chemistries and architectures available, all of which have advantages and disadvantages, and affect solution viscosity through different mechanisms. Understanding these mechanisms and how they impart additive function is critical to the development of new viscosity modifiers that enable lubricants to function more efficiently over a wide range of temperatures.

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“…These results indicate that addition of specifically designed surface binding groups in the polymer architecture is not a necessity for boundary film formation, greatly simplifying the molecular design and synthesis of these additives. 20,26 The thin absorbed layers observed for the linear and randomly branched additives (Figure 4a, gray and black) suggest that these polymer chains adopt a flat conformation on the surface, indicative of strong adsorption (Figure 4b, left). This flat orientation is further emphasized when realizing that the coil dimensions of the polymers in bulk solution, quantified by the radii of gyration (R g ), are significantly larger than the adsorbed layer thickness (Table 1, entries 1 and 2).…”

Section: Acs Applied Materials and Interfacesmentioning

confidence: 99%

Triple Function Lubricant Additives Based on Organic–Inorganic Hybrid Star Polymers: Friction Reduction, Wear Protection, and Viscosity Modification

Ravensteijn¹,

Zerdan²,

Seo³

et al. 2018

ACS Appl. Mater. Interfaces

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Polymer-based lubricant additives for friction reduction, wear protection, or viscosity improvement have been widely studied. However, single additives achieving all three functions are rare. To address this need, we have explored the combination of polymer topology with organic–inorganic hybrid chemistry to simultaneously vary the temperature- and shear-dependent properties of polymer additives in solution and at solid surfaces. A topological library of lubricant additives, based on statistical copolymers of stearyl methacrylate and methyl methacrylate, ranging from linear to branched star architectures, was prepared using ruthenium-catalyzed controlled radical polymerization. Control over the polymerization yielded additives with low dispersity and comparable molecular weights, allowing evaluation of the influence of polymer architecture on friction reduction, wear protection, and bulk viscosity improvement in a commercial base oil (Yubase 4). Structure–performance relationships for these functions were assessed by a combination of a high-speed surface force apparatus (HS-SFA) experiments, wear track profilometry, quartz crystal microbalance analysis, and solution viscometry. The custom-built HS-SFA provides a unique experimental environment to measure the boundary lubrication performance under extreme shear rates (≈107 s–1) for prolonged times (24 h), mimicking the extreme conditions of automotive applications. These experiments revealed that the performance of the additives as boundary lubricants and wear protectants scales with the degree of branching. The branched architectures prohibit ordering of the additives in thin films under high-load conditions, leading to a thicker absorbed polymer brush boundary layer and therefore enhanced film fluidity and lubricity. Additionally, star polymers with increasing arm number lead to bulk viscosity modification, reflected by a significant increase in the viscosity index compared to the commercial base oil. Although outperformed by linear polymers for bulk viscosity improvement, the (hybrid) star polymers successfully combine the three distinct lubricant additive functions: friction reduction, wear protection, and bulk viscosity improvementin a single polymeric structure. It should also be noted that, judging from HS-SFA experiments, hybrid stars carrying a silicate-based core outperform their fully organic analogues as boundary lubricants. The enhanced performance is most likely driven by attractive forces between the silicate cores and the employed metallic surfaces. Combining three function in one minimizes formulation complexity and thus opens a route to fundamentally understand and formulate key design parameters for the development of novel multifunction lubricant additives.

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Dual functional star polymers for lubricants

Abstract: Star-shaped poly(alkyl methacrylate)s (PAMAs) with a 3-arm architecture were designed, prepared and their performance as a dual additive (viscosity index improver and friction modifier) for engine oils was evaluated.

Cited by 26 publications

References 24 publications

Highly branched polyethylenes as lubricant viscosity and friction modifiers

Highly branched polyethylenes as lubricant viscosity and friction modifiers

Review of Viscosity Modifier Lubricant Additives

Triple Function Lubricant Additives Based on Organic–Inorganic Hybrid Star Polymers: Friction Reduction, Wear Protection, and Viscosity Modification

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