Conformational Analysis of Poly(ethylene imine) and Its Model Compounds:  Rotational and Inversional Isomerizations and Intramolecular and Intermolecular Hydrogen Bonds

Sasanuma, Yuji; Hattori, Satoshi; Imazu, Shinichi; Ikeda, Shigerô; Kaizuka, Tomoyoshi; Iijima, T.; Sawanobori, Misa; Azam, Muhammad Awais; Law, Robert V.; Steinke, Joachim H. G.

doi:10.1021/ma0401222

Cited by 30 publications

(78 citation statements)

References 47 publications

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“…Meanwhile, studies using quantum chemical calculations, which differ from RIS, MM and MD in that the experimentally obtained force field constants are not used, have been reported. [14][15][16][17][18][19][20] It is considered that this method is in a position to obtain accurate information of a single chain eliminating intermolecular interactions. Regarding PEO, Tsuzuki et al, 14 Smith et al 15,16 and Sasanuma et al 17 reported results using a monomer (dimethoxyethane) as a model of PEO.…”

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confidence: 99%

Conformational Analysis of Ethylene Oxide and Ethylene Imine Oligomers by Quantum Chemical Calculation

Kobayashi

Sato

2008

Polym J

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Conformational analyses have been carried out for ethylene oxide (EO) and ethylene imine (EI) oligomer models (single chain) by quantum chemical calculations (RHF/6-31+G(d,p)). The conformations repeated for a unit of X-C, CC and C-X bonds (X: O or N) were examined. For optimizations of the EI oligomers, some designation systems with trans values were used, taking account of pseudoasymmetry. For the EO oligomers (EO-x, x = 2-to 8-mers), (ttt) x and (tg þ t) x conformers were first and second stable (ÁE = 1.17-1.26 kcal/m.u.), respectively. On the contrary, for the EI oligomers (EI-x, x = 2-to 11mers), (tg þ t) x and (ttt) x were first and second stable (ÁE = 1.32-1.42 kcal/m.u.), respectively. Therefore, the gauche preference of CC bond in EI-x is stronger than that in EO-x. The calculated structures of (ttt) x and (tg þ t) x in EO-x agreed with those observed by XRD analysis for PEO crystals in stretched (planar zigzag) and original (7/2 helix) states, respectively. The calculated structures of (tg þ t) x and (ttt) x in EI-x also agreed with those observed for PEI crystals in dehydrate (7/2 helix) and hydrate (planar zigzag) states, respectively. However, the dihedral angles (EO-8) and the 5 mol length (EI-11) in both helices did not agree with each of the observed values for the polymers. Each difference between the oligomers (single chain) and polymers was estimated by the effect of intermolecular interactions in PEO or PEI. For (tg þ t) x of EI-11, the existence of metastable skewed helical structures (reversed and/or kinked) were estimated in addition to the helix.

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confidence: 99%

Conformational Analysis of Ethylene Oxide and Ethylene Imine Oligomers by Quantum Chemical Calculation

Kobayashi

Sato

2008

Polym J

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“…Sasanuma et al 7 has reported that the characteristic ratios (P meso /P racemo ) of PEI chaines, which were evaluated from energy parameters, changed from 0.63/0.37 in gaseous state to 0.52/0.48 in the state that intra-molecular interaction (NHÁÁÁH) was neglected. The results estimated in present study support these evaluated results.…”

Section: Hydrate Effects On Trans/gauche Preferencesmentioning

confidence: 99%

“…Unlike the PEO solutions, the trans-fractions of the C-C bonds of the PEI solutions increase with increase of permittivity (") of solvents, based on NMR analyses of N,N 0 -dimethylethylenediamine (di-MEDA) as a model of PEI. 7 The conformation of PEI, in this manner, specifically depends on environmental factors. Unfortunately, detailed understandings of these environmental effects have yet to be clarified because of the complexity in these effects.…”

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confidence: 99%

“…[10][11][12] Furthermore, in contrast to the RIS, MM, and MD methods, recent studies involve quantum chemical calculations method (QCC). Although conformational analysis in the gaseous phase using QCC has been reported for dimethoxyethane (DME) [13][14][15][16] and its oligomers 13,17 (as models of PEO) and for di-MEDA 7,18 (as a model of PEI), comparable studies in the liquid phase, however, are little. Smith et al 19 have reported the potential study of DME in aqueous solution (hydrate model) using QCC.…”

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confidence: 99%

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

2009

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Hydrate effects on the conformations of ethylene imine oligomers (EI-x, x ¼ 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 = H 2 O mol /N mol ), 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 (E c ) 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 (Á h , based on E c 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 þ t) x conformers with h < 1, and the (ttt) x conformers over 3 mers with h ¼ 1, were the most stable. Each result corresponded to results observed for nonhydrated 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 (ÁE c(g) ) of each conformer.KEY WORDS: Conformation / Poly(ethylene imine) / Oligomer / Hydrate Effect / Quantum Chemical Calculation / Poly(ethylene imine) (PEI) has unique properties because it possesses electron-releasing heteroatom (N) in the skeletal chain, similar to heteroatom (O) in poly(ethylene oxide) (PEO). Such properties, including specific affinity to substrate and solubility of inorganic salt, have been employed in the advancement of solid polymer electrolytes, 1 gene delivery polymers, 2 etc. These properties are often affected by conformational characteristics such as trans/gauche preferences, which depend on environmental factors such as temperature, solvent, etc. The conformational analyses of these polymers, therefore, are essential in the molecular design towards various applications.X-Ray diffraction (XRD) 3-5 and other analyses 6 have confirmed that the structure of a linear non-hydrated PEI crystal is a 5/1 double stranded helix, with a repeating tgt conformation for the N-C, C-C, and C-N bonds. In the hydrate state, the structure transforms to the planar zigzag ttt conformation. Unlike the PEO solutions, the trans-fractions of the C-C bonds of the PEI solutions increase with increase of permittivity (") of solvents, based on NMR analyses of N,N 0 -dimethylethylenediamine (di-MEDA) as a model of PEI. 7 The conformation of PEI, in this manner, specifically depends on environmental factors. Unfortunately, detailed understandings of these environmental effects have yet to be clarified because of the complexity in these effects.To complement the experimental observations in the conformational analyses of PEO or PEI, computational chemistry is employed. Pioneering works on PEO, involving a rotational isomeric state model (RIS), was reported by M...

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“…Analyses for anhydrate models using molecular mechanics (MM) and molecular dynamics (MD) have been reported [5,6]. Furthermore, recent studies involve quantum chemical calculations method (QCC) [7][8][9]. The reports concerning an analysis using hydrate model of PEI, however, seem to be little [10].…”

Section: Introductionmentioning

confidence: 99%

Structure Analysis for Hydrate Models of Ethyleneimine Oligomer by Quantum Chemical Calculation

Kobayashi¹,

Sato²

2010

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Structure analyses for hydrate models of ethyleneimine oligomer (5-mer as model of PEI) were investigated by quantum chemical calculations. Conformation energies and structures optimized for hydrate models of (ttt)5 and (tgt)5 conformers were examined. Hydrate ratio, h [h = H2O/N (mol)], was set from 0.5 to 2. In anhydrates, (tg+t)5 conformer was more stable (?1.8 kcal/m.u.) than (ttt)5. In hydrates, (ttt)5 conformers were more stable (?0.7 - ?4.3) than (tg+t)5. These results corresponded to experimental results that anhydrous linear PEI crystal changes from double helical to single planar chain in hydration process. Structures calculated for (ttt)5 agreed in those observed for hydrates of PEI. In all (tg+t)5 conformers, O???H bonds between waters were found with the decreases of N???H bonds between imino group and water. The O???H bonds in (tg+t)5 conformer resulted in its high chain torsion, and strongly related with instability and structure change (large swelling)

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Conformational Analysis of Poly(ethylene imine) and Its Model Compounds: Rotational and Inversional Isomerizations and Intramolecular and Intermolecular Hydrogen Bonds

Cited by 30 publications

References 47 publications

Conformational Analysis of Ethylene Oxide and Ethylene Imine Oligomers by Quantum Chemical Calculation

Conformational Analysis of Ethylene Oxide and Ethylene Imine Oligomers by Quantum Chemical Calculation

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

Structure Analysis for Hydrate Models of Ethyleneimine Oligomer by Quantum Chemical Calculation

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