Ab initio characterizations of molecular structures, conformation energies, and hydrogen-bonding properties for polyurethane hard segments

Sun, Hongyan

doi:10.1021/ma00074a014

Cited by 129 publications

(62 citation statements)

References 10 publications

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“…Traditionally, the N-H· · · O=C hydrogen bond between two urea groups has been considered the strongest, with hydrogen bond between two urethane groups being the second strongest. However, recent studies have shown that N-H· · · O (ether) bond is slightly stronger than N-H· · · O=C urethane bond [16]. Conversely, it is known that the primary hydrogen bond acceptor depends on the length the soft segments and the concentration of the hard segments in a chain [17].…”

Section: Resultsmentioning

confidence: 99%

“…The HS and SS are thermodynamically incompatible at low temperatures, resulting in the microphase separated structure of PU [14,15]. The grade of the microphase separation can be determined from IR spectra using the part of free and hydrogen bonded carbonyl groups in urethane and urea bonds [16]. The FTIR spectra of the pristine and nanofilled PU foams and are shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

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Synthesis and mechanical characterization of nanoparticle-infused polyurethane foams. Statistical analysis of foam morphology

Pikhurov¹,

Zuev²

2016

Nanosystems: Phys. Chem. Math.

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Nanocomposite polyurethane (PU) foams filled with different loadings (0.1 -0.7 wt.%) of nanosized silica (average grain size of ∼ 7 and 12 nm) and organonanoclay were prepared by the prepolymer method, and their mechanical properties were investigated. A statistical analysis of the size distribution for foam cells was successfully applied in order to characterize their morphology. The developed approach was shown to provide a detailed analysis of the morphology development in PU foams, including the primary cell formation and their subsequent break-up and coalescence. The degree of phase separation in nanocomposite polyurethane foams, which is dependent on the nanofiller, was calculated from the IR spectra. The presence of silica nanoparticles and organoclays gives rise to significant differences in the mechanical (stress-strain) properties of the nanocomposite polyurethane foams relative to the pure polymer.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Synthesis and mechanical characterization of nanoparticle-infused polyurethane foams. Statistical analysis of foam morphology

Pikhurov¹,

Zuev²

2016

Nanosystems: Phys. Chem. Math.

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“…Clearly the carbamate is severely impeding attack by MAH, most likely because of the greater rigidity of 21 than 3. The carbamate moiety is planar with a rotational barrier of around 12 kcal/mole for rotation about the O-(C=O) bond [18]. Molecular mechanics models suggest a rotation of 90 -100 o around this bond, thus costing close to the maximal energy, would be needed to adjust phenyl carbamate to the ground state phenylacetamide geometry.…”

Section: Inhibition By O-acyl Hydroxamic Acidsmentioning

confidence: 99%

Specificity and mechanism of mandelamide hydrolase catalysis

Adediran

Wang

Shilabin

et al. 2017

Archives of Biochemistry and Biophysics

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The best-studied amidase signature (AS) enzyme is probably fatty acid amide hydrolase (FAAH). Closely related to FAAH is mandelamide hydrolase (MAH), whose substrate specificity and mechanism of catalysis are described in this paper. First, we developed a convenient chromogenic substrate, 4-nitrophenylacetamide, for MAH. The lack of reactivity of MAH with the corresponding ethyl ester confirmed the very limited size of the MAH leaving group site. The reactivity of MAH with 4-nitrophenyl acetate and methyl 4-nitrophenyl carbonate, therefore, suggested formation of an "inverse" acyl-enzyme where the small acylgroup occupies the normal leaving group site. We have interpreted the specificity of MAH for phenylacetamide substrates and small leaving groups in terms of its active site structure, using a homology model based on a FAAH crystal structure. The relevant structural elements were compared with those of FAAH. Phenylmethylboronic acid is a potent inhibitor of MAH (K i = 27 nM), presumably because it forms a transition state analogue structure with the enzyme. O-Acyl hydroxamates were not irreversible inactivators of MAH but some were found to be transient inhibitors.3

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“…All parameters are listed in Tables 1-4. Parameters for the PHR-XYR bond, XYR-PHR-XYR angle, PHR-XYR-BER angle, BER-PHR-XYR angle, BER-XYR-PHR-BER dihedral, XYR-PHR-BER-XYR dihedral, and PHR-BER-XYR-PHR dihedral are calculated according to the structural information provided by the atomistic force field PCFF [44][45][46][47][48][49][50][51][52][53][54], since they are not available in DeVane's work. Considering the difference between the PPE polymer and its DMP monomer, we make several adjustments to other parameters in order to make the parameters suitable for PPE in this study, especially to the PHR bead, because most of the PHR beads here represent a BER bead with an ether oxygen rather than a hydroxyl oxygen.…”

Section: Scheme 1 the Cg Mapping Of A Ppe Unitmentioning

confidence: 99%

“…The polymer consistent force field (PCFF) [44][45][46][47][48][49][50][51][52][53][54] was employed throughout the atomistic simulations. The simulations employ periodic boundary condition in all directions and all PS chains in the atomistic simulations are isotactic.…”

Section: 2 Simulation Detailsmentioning

confidence: 99%

Refinement of a coarse-grained model of poly(2,6-dimethyl-1,4-phenylene ether) and its application to blends of PPE and PS

Wang

Shentu

Faller

2015

Molecular Simulation

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Abstract:A coarse-grained (CG) molecular simulation model has been refined for poly (2,6-dimethyl-1,4-phenylene ether) (PPE). This was successfully validated against atomistic simulation and experimental data. Particularly, the glass transition temperature (T g ) of PPE was studied using both atomistic and CG models and compared favorably to experimental data. In addition, we used the CG model together with an existing Martini CG model of polystyrene (PS) to study the blending behavior of these two polymers. We solved the problem to mix the different potentials and molecular dynamics of high-molecular-weight blends of PPE/PS was performed in detail.

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Ab initio characterizations of molecular structures, conformation energies, and hydrogen-bonding properties for polyurethane hard segments

Cited by 129 publications

References 10 publications

Synthesis and mechanical characterization of nanoparticle-infused polyurethane foams. Statistical analysis of foam morphology

Synthesis and mechanical characterization of nanoparticle-infused polyurethane foams. Statistical analysis of foam morphology

Specificity and mechanism of mandelamide hydrolase catalysis

Refinement of a coarse-grained model of poly(2,6-dimethyl-1,4-phenylene ether) and its application to blends of PPE and PS

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