Prediction of the Interaction between Crude Oil Wax-Crystal Fractions and Acrylate Polymers by Monte Carlo Simulation

The interaction between n-alkanes and pour point depressants with different structures was investigated. Using n-hexadecane as the representative component of crude oil n-alkanes, molecular simulation was employed to study the interaction between polyacrylate pour point depressants with different side chain length and n-hexadecane, and the interaction between polyacrylate pour point depressants with different polar building blocks and n-hexadecane. It was shown that during wax precipitation process, the mixed energy is low when the side chain length of acrylate is compatible with n-hexadecane. It is easier for polyacrylate to go into wax-crystal lattice, thus lowering crude oil pour point. The simulation for pour point depressants consisting of acrylate and other different polar building blocks demonstrated that the stronger the polarity of polar building block, the lower the interaction energy between polymer pour point depressant and n-hexadecane. At the same time, it is easier for polymers with polar building blocks to interact with n-alkanes. The polar building block can effectively inhibit wax-crystal growth and thus improve crude oil low-temperature fluidity.

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New 6-Bromotryptamine Derivatives from Marine Bacterium Pseudoalteromonas rubra QD1 - 2 and the Impact of Side Chain Length on Their Cytotoxicity

Planta Medica ◽

10.1055/s-0033-1348634 ◽

2013 ◽

Vol 79 (10) ◽

Author(s):

S He ◽

L Ding ◽

X Yan

Keyword(s):

Chain Length ◽

Marine Bacterium ◽

Side Chain ◽

Side Chain Length ◽

The Impact ◽

Pseudoalteromonas Rubra

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Effects of Amino Acid Side-Chain Length and Chemical Structure on Anionic Polyglutamic and Polyaspartic Acid Cellulose-Based Polyelectrolyte Brushes

Polymers ◽

10.3390/polym13111789 ◽

2021 ◽

Vol 13 (11) ◽

pp. 1789

Author(s):

Dmitry Tolmachev ◽

George Mamistvalov ◽

Natalia Lukasheva ◽

Sergey Larin ◽

Mikko Karttunen

Keyword(s):

Glutamic Acid ◽

Chain Length ◽

Chemical Structure ◽

Side Chain ◽

Side Chains ◽

Side Chain Length ◽

Polyelectrolyte Brushes ◽

Grafting Density ◽

The Difference ◽

Cellulose Surface

We used atomistic molecular dynamics (MD) simulations to study polyelectrolyte brushes based on anionic α,L-glutamic acid and α,L-aspartic acid grafted on cellulose in the presence of divalent CaCl2 salt at different concentrations. The motivation is to search for ways to control properties such as sorption capacity and the structural response of the brush to multivalent salts. For this detailed understanding of the role of side-chain length, the chemical structure and their interplay are required. It was found that in the case of glutamic acid oligomers, the longer side chains facilitate attractive interactions with the cellulose surface, which forces the grafted chains to lie down on the surface. The additional methylene group in the side chain enables side-chain rotation, enhancing this effect. On the other hand, the shorter and more restricted side chains of aspartic acid oligomers prevent attractive interactions to a large degree and push the grafted chains away from the surface. The difference in side-chain length also leads to differences in other properties of the brush in divalent salt solutions. At a low grafting density, the longer side chains of glutamic acid allow the adsorbed cations to be spatially distributed inside the brush resulting in a charge inversion. With an increase in grafting density, the difference in the total charge of the aspartic and glutamine brushes disappears, but new structural features appear. The longer sides allow for ion bridging between the grafted chains and the cellulose surface without a significant change in main-chain conformation. This leads to the brush structure being less sensitive to changes in salt concentration.

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