scholarly journals Molecular structure of bottlebrush polymers in melts

2016 ◽  
Vol 2 (11) ◽  
pp. e1601478 ◽  
Author(s):  
Jarosław Paturej ◽  
Sergei S. Sheiko ◽  
Sergey Panyukov ◽  
Michael Rubinstein
Keyword(s):  
Molecular Structure ◽  
Chemical Composition ◽  
Numerical Simulations ◽  
Chain Length ◽  
Polymer Melts ◽  
Side Chain ◽  
Molecular Architecture ◽  
Practical Applications ◽  
Grafting Density ◽  
Theoretical Predictions

Bottlebrushes are fascinating macromolecules that display an intriguing combination of molecular and particulate features having vital implications in both living and synthetic systems, such as cartilage and ultrasoft elastomers. However, the progress in practical applications is impeded by the lack of knowledge about the hierarchic organization of both individual bottlebrushes and their assemblies. We delineate fundamental correlations between molecular architecture, mesoscopic conformation, and macroscopic properties of polymer melts. Numerical simulations corroborate theoretical predictions for the effect of grafting density and side-chain length on the dimensions and rigidity of bottlebrushes, which effectively behave as a melt of flexible filaments. These findings provide quantitative guidelines for the design of novel materials that allow architectural tuning of their properties in a broad range without changing chemical composition.

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

Polymers ◽  
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.

scholarly journals Impact of molecular structure on secondary organic aerosol formation from aromatic hydrocarbon photooxidation under low NO<sub><i>x</i></sub> conditions

2016 ◽  
Author(s):  
L. Li ◽  
P. Tang ◽  
S. Nakao ◽  
D. R. Cocker III
Keyword(s):  
Molecular Structure ◽  
Chemical Composition ◽  
Aromatic Hydrocarbon ◽  
Chain Length ◽  
Aromatic Hydrocarbons ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Ortho Position ◽  
Aerosol Formation ◽  
The Impact

Abstract. The molecular structure of volatile organic compounds (VOC) determines their oxidation pathway, directly impacting secondary organic aerosol (SOA) formation. This study comprehensively investigates the impact of molecular structure on SOA formation from the photooxidation of twelve different eight to nine carbon aromatic hydrocarbons under low NOx conditions. The effects of the alkyl substitute number, location, carbon chain length and branching structure on the photooxidation of aromatic hydrocarbons are demonstrated by analyzing SOA yield, chemical composition and physical properties. Aromatic hydrocarbons, categorized into five groups, show a yield order of ortho (o-xylene and o-ethyltoluene) > one substitute (ethylbenzene, propylbenzene and isopropylbenzene) > meta (m-xylene and m-ethyltoluene) > three substitute (trimethylbenzenes) > para (p-xylene and p-ethyltoluene). SOA yields of aromatic hydrocarbon photooxidation do not monotonically decrease when increasing alkyl substitute number. The ortho position promotes SOA formation while the para position suppresses aromatic oxidation and SOA formation. Observed SOA chemical composition and volatility confirm that higher yield is associated with further oxidation. SOA chemical composition also suggests that aromatic oxidation increases with increasing alkyl substitute chain length and branching structure. Further, carbon dilution theory developed by Li et al. (2015a) is extended in this study to serve as a standard method to determine the extent of oxidation of an alkyl substituted aromatic hydrocarbon.

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

2021 ◽  
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 &alpha;-L-glutamic acid and &alpha;-L-aspartic acid grafted on cellulose in the presence of divalent CaCl2 salt at different concentrations. The motivation is the search of the 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, chemical structure and their interplay is 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.

scholarly journals Impact of molecular structure on secondary organic aerosol formation from aromatic hydrocarbon photooxidation under low-NO<sub><i>x</i></sub> conditions

2016 ◽  
Vol 16 (17) ◽  
pp. 10793-10808 ◽  
Author(s):  
Lijie Li ◽  
Ping Tang ◽  
Shunsuke Nakao ◽  
David R. Cocker III
Keyword(s):  
Molecular Structure ◽  
Chemical Composition ◽  
Aromatic Hydrocarbon ◽  
Chain Length ◽  
Aromatic Hydrocarbons ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Ortho Position ◽  
Aerosol Formation ◽  
The Impact

Abstract. The molecular structure of volatile organic compounds determines their oxidation pathway, directly impacting secondary organic aerosol (SOA) formation. This study comprehensively investigates the impact of molecular structure on SOA formation from the photooxidation of 12 different eight- to nine-carbon aromatic hydrocarbons under low-NOx conditions. The effects of the alkyl substitute number, location, carbon chain length and branching structure on the photooxidation of aromatic hydrocarbons are demonstrated by analyzing SOA yield, chemical composition and physical properties. Aromatic hydrocarbons, categorized into five groups, show a yield order of ortho (o-xylene and o-ethyltoluene) > one substitute (ethylbenzene, propylbenzene and isopropylbenzene) > meta (m-xylene and m-ethyltoluene) > three substitute (trimethylbenzenes) > para (p-xylene and p-ethyltoluene). SOA yields of aromatic hydrocarbon photooxidation do not monotonically decrease when increasing alkyl substitute number. The ortho position promotes SOA formation while the para position suppresses aromatic oxidation and SOA formation. Observed SOA chemical composition and volatility confirm that higher yield is associated with further oxidation. SOA chemical composition also suggests that aromatic oxidation increases with increasing alkyl substitute chain length and branching structure. Further, carbon dilution conjecture developed by Li et al. (2016) is extended in this study to serve as a standard method to determine the extent of oxidation of an alkyl-substituted aromatic hydrocarbon.

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