Regular Article

Polymer Journal (2009) 41, 880–887; doi:10.1295/polymj.PJ2009115

Conformational Analysis for Hydrated Ethylene Imine Oligomer Models by Quantum Chemical Calculations

Conformational Analysis for Hydrated Ethylene Imine Oligomer

Minoru Kobayashi1, Makoto Takahashi1 and Hisaya Sato2

  1. 1Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Naka-cho, Koganei 184-8588, Japan
  2. 2Graduate School of Technical Management, Tokyo University of Agriculture and Technology, Naka-cho, Koganei 184-8588, Japan

Correspondence: Minoru Kobayashi, Fax: +81-72-689-1918, E-mail: mikoba3@aol.com

Received 12 May 2009; Accepted 5 July 2009; Published online 19 August 2009.

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Abstract

Hydrate effects on the conformations of ethylene imine oligomers (EI-x, x = 1–8 mers) were examined using quantum chemical calculations. Models were constructed by locating a water molecule to each nitrogen atom in the structures optimized for non-hydrate oligomers. Hydrate ratio, h (h = H2Omol/Nmol), was set from 0 to 1. Six type conformations with repeated units of N-C, C-C and C-N bonds were examined. Conformational energies (Ec) were calculated as differences between energies of oligomers with water molecules and those of non-hydrogen and/or hydrogen bonding water molecules. Hydrate energies for each conformer (Deltamuh, based on Ec in non-hydrate state) were negative and linearly decreased with increase of h, and all conformers were stabilized by electrostatic effect with hydration. All (tg+t)x conformers with h < 1, and the (ttt)x conformers over 3 mers with h = 1, were the most stable. Each result corresponded to results observed for non-hydrated and hydrated linear PEI crystals, respectively, and seemed to be related with hydrogen bonding between water molecules. Lengths of conformers having gauche structure significantly decreased with increasing h. Such contractions by hydrations, however, were independent of gauche preference energy (DeltaEc(g)) of each conformer.

Keywords:

Conformation, Poly(ethylene imine), Oligomer, Hydrate Effect, Quantum Chemical Calculation

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