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Application of the Self-Assembled Monolayer (SAM) Model to Dithiophosphate and Dithiocarbamate Engine Wear Inhibitors

Zhou, Yanhua and Jiang, Shaoyi and Çağin, Tahir and Yamaguchi, Elaine S. and Frazier, Rawls and Ho, Andrew and Tang, Yongchun and Goddard, William A., III (2000) Application of the Self-Assembled Monolayer (SAM) Model to Dithiophosphate and Dithiocarbamate Engine Wear Inhibitors. Journal of Physical Chemistry A, 104 (11). pp. 2508-2524. ISSN 1089-5639. doi:10.1021/jp9908146.

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In previous studies of dithiophosphate [DTP = S_2P(OR)_2] wear inhibitors bound to an oxidized iron surface, we found that the cohesive energy of the self-assembled monolayers (SAM) for DTP molecules with various organic R groups correlates with the wear inhibition observed in full engine experiments. In this paper we expand these calculations to consider dynamics at 500 K and then use the SAM model to predict new candidates for wear inhibitors. Using molecular dynamics (MD) simulations at 500 K, we show that the SAM has one DTP per two surface Fe sites of iron oxide. At this coverage we find that the cohesive energy of the SAM at 500 K is in the sequence 2-alkyl > 1-alkyl > aryl (e.g., iPr > iBu > Ph) which again correlates with wear inhibitor performance observed in engine tests. We then considered 7 novel DTPs and predict that R = cyclo-hexyl, nPr, and benzyl may perform as well as iPr. We then used the SAM wear inhibitor model to assess the likely performance of 11 novel classes of potential wear inhibitors. On the basis of this model we selected dithiocarbamates (DTC) as the best candidate to supplement DTP. We then considered a number of possible alkyl substitutions for DTC. The SAM model suggests that iC_5 and nC_3 are the best candidates, followed closely by iC_3.

Item Type:Article
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URLURL TypeDescription
Çağin, Tahir0000-0002-3665-0932
Goddard, William A., III0000-0003-0097-5716
Additional Information:© 2000 American Chemical Society. Received 8 March 1999. Published online 16 March 2000. Published in print 1 March 2000. This research was supported by the Chevron Chemical Company (Oronite Technology group). It was also supported by grants from the DOE-BCTR and NSF (CHE 95-12279). The facilities of the MSC are also supported by grants from DOE-ASCI, BP Chemical, ARO-MURI (Kiserow), Beckman Institute, Seiko-Epson, Exxon, Avery-Dennison Corp., NASA/Ames, Chevron Petroleum Technology Co., Asahi Chemical, NASA/JPL, Owens-Corning, and Chevron Research Technology Co. We thank Larry Smarr for access to the NCSA system for some calculations.
Funding AgencyGrant Number
Chevron Chemical CompanyUNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
Army Research Office (ARO)UNSPECIFIED
Caltech Beckman InstituteUNSPECIFIED
Avery–Dennison Corp.UNSPECIFIED
Chevron Petroleum Technology Co.UNSPECIFIED
Chevron Research Technology Co.UNSPECIFIED
Issue or Number:11
Record Number:CaltechAUTHORS:20170720-070312192
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Official Citation:Application of the Self-Assembled Monolayer (SAM) Model to Dithiophosphate and Dithiocarbamate Engine Wear Inhibitors Yanhua Zhou, Shaoyi Jiang, Tahir Çaǧın, Elaine S. Yamaguchi, Rawls Frazier, Andrew Ho, Yongchun Tang, and William A. Goddard, III The Journal of Physical Chemistry A 2000 104 (11), 2508-2524 DOI: 10.1021/jp9908146
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:79227
Deposited By: Ruth Sustaita
Deposited On:20 Jul 2017 18:49
Last Modified:15 Nov 2021 17:46

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