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Structural flexibility of 4,4'-methylene diphenyl diisocyanate (4,4'-MDI): evidence from first principles calculations.

Rodziewicz P, Goclon J - J Mol Model (2014)

Bottom Line: Global and local minima structures were found and confirmed by vibrational analysis.The energy barriers related to rotation of the aromatic rings were estimated by DFT calculations.The stability of global and local minima was verified by Car-Parrinello (MD) runs at finite temperature.

View Article: PubMed Central - PubMed

Affiliation: Institute of Chemistry, University of Bialystok, Hurtowa 1, 15-399, Bialystok, Poland, pawel.rodziewicz@fau.de.

ABSTRACT
A reactant used globally in the production of polyurethane is the molecule 4,4'-methylene diphenyl diisocyanate (4,4'-MDI). The structural flexibility of 4,4'-MDI is one of the most important molecular properties influencing the polymerization process and this property was therefore modeled using density functional theory (DFT) calculations and Car-Parrinello molecular dynamics (MD) simulations. Global and local minima structures were found and confirmed by vibrational analysis. The energy barriers related to rotation of the aromatic rings were estimated by DFT calculations. The stability of global and local minima was verified by Car-Parrinello (MD) runs at finite temperature. The presence of weak C-H⋯π hydrogen bonds was confirmed by atoms in molecules analysis and found to be responsible for the low energy barriers.

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Time evolution of the structure of the 4,4′-MDI molecule from Car-Parrinello molecular dynamics (CP-MD) simulation. Each snapshot is presented with its time-stamp. The first four snapshots show one full simultaneous counter-rotation of both phenyl rings. Black and orange arrows around the C–C bonds show the direction of motion for the top and the bottom phenyl ring, respectively. Snapshots 5 and 7 show the intermediate structures in further rotations, whereas 6 and 8 refer to the equilibrium state. The presence of the C–H⋯π H-bond is marked by a dashed line where applicable
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Fig3: Time evolution of the structure of the 4,4′-MDI molecule from Car-Parrinello molecular dynamics (CP-MD) simulation. Each snapshot is presented with its time-stamp. The first four snapshots show one full simultaneous counter-rotation of both phenyl rings. Black and orange arrows around the C–C bonds show the direction of motion for the top and the bottom phenyl ring, respectively. Snapshots 5 and 7 show the intermediate structures in further rotations, whereas 6 and 8 refer to the equilibrium state. The presence of the C–H⋯π H-bond is marked by a dashed line where applicable

Mentions: Figure 3 shows the most important steps in the CP-MD trajectory depicted as two rows of snapshots with the time stamps indicated. Successive snapshots were taken from the same perspective to observe, in the more transparent way possible, the motion of the phenyl rings. The first snapshot refers to the beginning of the phenyl ring rotation process and shows the structure of the 4,4′-MDI molecule at the time of 2.8 ps. Analysis of the structural rearrangements is based mainly on phenyl ring rotation so it is important to introduce some useful on-going definitions to describe this process. We consider clockwise and counter clockwise rotation of the phenyl ring, if looking at the N atom aligned in one axis with two C atoms, namely one C atom from the phenyl ring and the second C atom from the –CH2 group. The second snapshot was recorded at 4.2 ps; mutual rotation of both phenyl rings was observed. The phenyl ring at the top part of the second snapshot rotates clockwise whereas the bottom one rotates counter clockwise. Successive snapshots recorded at 4.6 and 5.1 ps show one full rotation of both phenyl rings.Fig. 3


Structural flexibility of 4,4'-methylene diphenyl diisocyanate (4,4'-MDI): evidence from first principles calculations.

Rodziewicz P, Goclon J - J Mol Model (2014)

Time evolution of the structure of the 4,4′-MDI molecule from Car-Parrinello molecular dynamics (CP-MD) simulation. Each snapshot is presented with its time-stamp. The first four snapshots show one full simultaneous counter-rotation of both phenyl rings. Black and orange arrows around the C–C bonds show the direction of motion for the top and the bottom phenyl ring, respectively. Snapshots 5 and 7 show the intermediate structures in further rotations, whereas 6 and 8 refer to the equilibrium state. The presence of the C–H⋯π H-bond is marked by a dashed line where applicable
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3936137&req=5

Fig3: Time evolution of the structure of the 4,4′-MDI molecule from Car-Parrinello molecular dynamics (CP-MD) simulation. Each snapshot is presented with its time-stamp. The first four snapshots show one full simultaneous counter-rotation of both phenyl rings. Black and orange arrows around the C–C bonds show the direction of motion for the top and the bottom phenyl ring, respectively. Snapshots 5 and 7 show the intermediate structures in further rotations, whereas 6 and 8 refer to the equilibrium state. The presence of the C–H⋯π H-bond is marked by a dashed line where applicable
Mentions: Figure 3 shows the most important steps in the CP-MD trajectory depicted as two rows of snapshots with the time stamps indicated. Successive snapshots were taken from the same perspective to observe, in the more transparent way possible, the motion of the phenyl rings. The first snapshot refers to the beginning of the phenyl ring rotation process and shows the structure of the 4,4′-MDI molecule at the time of 2.8 ps. Analysis of the structural rearrangements is based mainly on phenyl ring rotation so it is important to introduce some useful on-going definitions to describe this process. We consider clockwise and counter clockwise rotation of the phenyl ring, if looking at the N atom aligned in one axis with two C atoms, namely one C atom from the phenyl ring and the second C atom from the –CH2 group. The second snapshot was recorded at 4.2 ps; mutual rotation of both phenyl rings was observed. The phenyl ring at the top part of the second snapshot rotates clockwise whereas the bottom one rotates counter clockwise. Successive snapshots recorded at 4.6 and 5.1 ps show one full rotation of both phenyl rings.Fig. 3

Bottom Line: Global and local minima structures were found and confirmed by vibrational analysis.The energy barriers related to rotation of the aromatic rings were estimated by DFT calculations.The stability of global and local minima was verified by Car-Parrinello (MD) runs at finite temperature.

View Article: PubMed Central - PubMed

Affiliation: Institute of Chemistry, University of Bialystok, Hurtowa 1, 15-399, Bialystok, Poland, pawel.rodziewicz@fau.de.

ABSTRACT
A reactant used globally in the production of polyurethane is the molecule 4,4'-methylene diphenyl diisocyanate (4,4'-MDI). The structural flexibility of 4,4'-MDI is one of the most important molecular properties influencing the polymerization process and this property was therefore modeled using density functional theory (DFT) calculations and Car-Parrinello molecular dynamics (MD) simulations. Global and local minima structures were found and confirmed by vibrational analysis. The energy barriers related to rotation of the aromatic rings were estimated by DFT calculations. The stability of global and local minima was verified by Car-Parrinello (MD) runs at finite temperature. The presence of weak C-H⋯π hydrogen bonds was confirmed by atoms in molecules analysis and found to be responsible for the low energy barriers.

Show MeSH
Related in: MedlinePlus