Surface Properties of N,N-Dimethylformamide–Water Mixtures, As Seen from Computer Simulations

Abstract

The liquid–vapor interface of N,N-dimethylformamide (DMF)–water mixtures, spanning the entire composition range, is investigated in detail at 298 K by molecular dynamics simulation and intrinsic surface analysis. DMF molecules are found to adsorb strongly at the liquid surface, but this adsorption extends only to the first molecular layer. Water and DMF molecules mix with each other on the molecular scale even in the surface layer; thus, no marked self-association of any of the components is seen at the liquid surface. The major surface component prefers such orientation in which the molecular dipole vector lays parallel with the macroscopic plane of the surface. On the other hand, the preferred orientation of the minor component is determined, at both ends of the composition range, by the possibility of H-bond formation with the major component. The lack of H-donating ability of DMF leads to a rapid breakup of the percolating H-bond network at the surface; due to the strong adsorption of DMF, this breakup occurs below the bulk phase DMF mole fraction of 0.03. The disruption of the surface H-bond network also accelerates the exchange of both species between the liquid surface and bulk liquid phase, although, for water, this effect becomes apparent only above a bulk phase DMF mole fraction of 0.4. H-bonds formed by a DMF and a water molecule live, on average, 25–60% longer than those formed by two water molecules at the liquid surface. A similar, but smaller (i.e., about 10–20%) difference is seen in the bulk liquid phase. The enhanced surface mobility of the molecules results in 2–6 times larger diffusion coefficient and 2–5 times shorter H-bond lifetime values at the liquid surface than in the bulk liquid phase. The diffusion of both molecules is slowed down in the presence of the other species; in the case of DMF, this effect is caused by the formation of water–DMF H-bonds, whereas for water, steric hindrances imposed by the bulky DMF neighbors are responsible for this slowing down.

Electrospun protein nanofibers with nanoscale morphological control for dopamine biosensing

“…In this case, the addition of DMF to the water was used to improve the electrospinning process, considering that it has lower surface tension than water, enabling easier jet formation at lower electric fields. 14 Moreover, DMF can partially disrupt the BSA tertiary structure 15 and generate partly unfolded conformations, which facilitate the process of continuous fiber formation. 9 The use of DMF in the minority to water gives the desired results of producing a stable cone during the process and, consequently, the possible formation of thick electrospun fabrics (Fig.…”

Electrospun protein nanofibers with nanoscale morphological control for dopamine biosensing

“…In this case, the addition of DMF to the water was used to improve the electrospinning process, considering that it has lower surface tension than water, enabling easier jet formation at lower electric fields. 14 Moreover, DMF can partially disrupt the BSA tertiary structure 15 and generate partly unfolded conformations, which facilitate the process of continuous fiber formation. 9 The use of DMF in the minority to water gives the desired results of producing a stable cone during the process and, consequently, the possible formation of thick electrospun fabrics (Fig.…”

Single Particle Dynamics at the Free Surface of Imidazolium-Based Ionic Liquids

“…This notion further stresses the need for identifying and analyzing the real, capillary wave corrugated intrinsic liquid surface in such studies and, hence, application of intrinsic analysis to investigate the surface dynamics of RTIL is also expected to yield new insight into this problem. Indeed, both single particle 72−83 and collective dynamics 84,85 of the particles at the intrinsic liquid surface of various atomic 72,73,84,85 and molecular liquids, [74][75][76][77][78]80 as well as liquid mixtures 79,82,83 and salt solutions, 81 have been studied in the past few years. However, we are only aware of a handful of studies of surface dynamics of RTILs where the interface was clearly defined using intrinsic analysis methods.…”

Liquid–Vapor Interface of Aqueous Ethylene Glycol Solutions: A Molecular Dynamics Study

“…15,27−29 The combined application of MD simulations and surface spectroscopic techniques has facilitated the comprehensive understanding of interfacial structure at the atomic level. 13,14,30−33 The l−v interface of aqueous solutions of many organic solvents, such as acetonitrile, 34−36 dimethylformamide 37 (DMF), dimethyl sulfoxide 13,38−41 (DMSO), formic acid, 14,26,42 ethanol, 14,43−45 methanol (MeOH), 14,35,46−51 etc., has been extensively investigated in the literature. These organic molecules are preferentially adsorbed at the interface due to their amphiphilic nature.…”

“…EG enriches the l–v interface; the enrichment is at its maximum at bulk x EG = 0.3. Similar findings were reported for aqueous DMSO and aqueous DMF solutions by Jedlovszky’s group in that DMSO and DMF were seen to enrich the l–v interface, with a maximum enrichment at a particular mixing composition. The current study investigates the EG excess at the interface as a function of the bulk mole fraction through the calculation of the adsorption and solvation-free energies of EG.…”

“…The low density of interfacial molecules poses a challenge to probe them. In this regard, molecular dynamics (MD) simulations have proven to be very useful in understanding the arrangement of molecules therein. ,− The combined application of MD simulations and surface spectroscopic techniques has facilitated the comprehensive understanding of interfacial structure at the atomic level. ,,− The l–v interface of aqueous solutions of many organic solvents, such as acetonitrile, − dimethylformamide (DMF), dimethyl sulfoxide ,− (DMSO), formic acid, ,, ethanol, ,− methanol (MeOH), ,,− etc., has been extensively investigated in the literature. These organic molecules are preferentially adsorbed at the interface due to their amphiphilic nature.…”

Electrospun protein nanofibers with nanoscale morphological control for dopamine biosensing

“…In this case, the addition of DMF to the water was used to improve the electrospinning process, considering that it has lower surface tension than water, enabling easier jet formation at lower electric fields. 14 Moreover, DMF can partially disrupt the BSA tertiary structure 15 and generate partly unfolded conformations, which facilitate the process of continuous fiber formation. 9 The use of DMF in the minority to water gives the desired results of producing a stable cone during the process and, consequently, the possible formation of thick electrospun fabrics (Fig.…”

Single Particle Dynamics at the Free Surface of Imidazolium-Based Ionic Liquids

“…This notion further stresses the need for identifying and analyzing the real, capillary wave corrugated intrinsic liquid surface in such studies and, hence, application of intrinsic analysis to investigate the surface dynamics of RTIL is also expected to yield new insight into this problem. Indeed, both single particle 72−83 and collective dynamics 84,85 of the particles at the intrinsic liquid surface of various atomic 72,73,84,85 and molecular liquids, [74][75][76][77][78]80 as well as liquid mixtures 79,82,83 and salt solutions, 81 have been studied in the past few years. However, we are only aware of a handful of studies of surface dynamics of RTILs where the interface was clearly defined using intrinsic analysis methods.…”

Liquid–Vapor Interface of Aqueous Ethylene Glycol Solutions: A Molecular Dynamics Study

“…15,27−29 The combined application of MD simulations and surface spectroscopic techniques has facilitated the comprehensive understanding of interfacial structure at the atomic level. 13,14,30−33 The l−v interface of aqueous solutions of many organic solvents, such as acetonitrile, 34−36 dimethylformamide 37 (DMF), dimethyl sulfoxide 13,38−41 (DMSO), formic acid, 14,26,42 ethanol, 14,43−45 methanol (MeOH), 14,35,46−51 etc., has been extensively investigated in the literature. These organic molecules are preferentially adsorbed at the interface due to their amphiphilic nature.…”

“…EG enriches the l–v interface; the enrichment is at its maximum at bulk x EG = 0.3. Similar findings were reported for aqueous DMSO and aqueous DMF solutions by Jedlovszky’s group in that DMSO and DMF were seen to enrich the l–v interface, with a maximum enrichment at a particular mixing composition. The current study investigates the EG excess at the interface as a function of the bulk mole fraction through the calculation of the adsorption and solvation-free energies of EG.…”

“…The low density of interfacial molecules poses a challenge to probe them. In this regard, molecular dynamics (MD) simulations have proven to be very useful in understanding the arrangement of molecules therein. ,− The combined application of MD simulations and surface spectroscopic techniques has facilitated the comprehensive understanding of interfacial structure at the atomic level. ,,− The l–v interface of aqueous solutions of many organic solvents, such as acetonitrile, − dimethylformamide (DMF), dimethyl sulfoxide ,− (DMSO), formic acid, ,, ethanol, ,− methanol (MeOH), ,,− etc., has been extensively investigated in the literature. These organic molecules are preferentially adsorbed at the interface due to their amphiphilic nature.…”

Electrospun protein nanofibers with nanoscale morphological control for dopamine biosensing

“…In this case, the addition of DMF to the water was used to improve the electrospinning process, considering that it has lower surface tension than water, enabling easier jet formation at lower electric fields. 14 Moreover, DMF can partially disrupt the BSA tertiary structure 15 and generate partly unfolded conformations, which facilitate the process of continuous fiber formation. 9 The use of DMF in the minority to water gives the desired results of producing a stable cone during the process and, consequently, the possible formation of thick electrospun fabrics (Fig.…”

Single Particle Dynamics at the Free Surface of Imidazolium-Based Ionic Liquids

“…This notion further stresses the need for identifying and analyzing the real, capillary wave corrugated intrinsic liquid surface in such studies and, hence, application of intrinsic analysis to investigate the surface dynamics of RTIL is also expected to yield new insight into this problem. Indeed, both single particle 72−83 and collective dynamics 84,85 of the particles at the intrinsic liquid surface of various atomic 72,73,84,85 and molecular liquids, [74][75][76][77][78]80 as well as liquid mixtures 79,82,83 and salt solutions, 81 have been studied in the past few years. However, we are only aware of a handful of studies of surface dynamics of RTILs where the interface was clearly defined using intrinsic analysis methods.…”

Liquid–Vapor Interface of Aqueous Ethylene Glycol Solutions: A Molecular Dynamics Study

“…15,27−29 The combined application of MD simulations and surface spectroscopic techniques has facilitated the comprehensive understanding of interfacial structure at the atomic level. 13,14,30−33 The l−v interface of aqueous solutions of many organic solvents, such as acetonitrile, 34−36 dimethylformamide 37 (DMF), dimethyl sulfoxide 13,38−41 (DMSO), formic acid, 14,26,42 ethanol, 14,43−45 methanol (MeOH), 14,35,46−51 etc., has been extensively investigated in the literature. These organic molecules are preferentially adsorbed at the interface due to their amphiphilic nature.…”

“…EG enriches the l–v interface; the enrichment is at its maximum at bulk x EG = 0.3. Similar findings were reported for aqueous DMSO and aqueous DMF solutions by Jedlovszky’s group in that DMSO and DMF were seen to enrich the l–v interface, with a maximum enrichment at a particular mixing composition. The current study investigates the EG excess at the interface as a function of the bulk mole fraction through the calculation of the adsorption and solvation-free energies of EG.…”

“…The low density of interfacial molecules poses a challenge to probe them. In this regard, molecular dynamics (MD) simulations have proven to be very useful in understanding the arrangement of molecules therein. ,− The combined application of MD simulations and surface spectroscopic techniques has facilitated the comprehensive understanding of interfacial structure at the atomic level. ,,− The l–v interface of aqueous solutions of many organic solvents, such as acetonitrile, − dimethylformamide (DMF), dimethyl sulfoxide ,− (DMSO), formic acid, ,, ethanol, ,− methanol (MeOH), ,,− etc., has been extensively investigated in the literature. These organic molecules are preferentially adsorbed at the interface due to their amphiphilic nature.…”