Energy Surface Properties Research Articles

Enhancing the low surface energy properties of polymer films with a dangling shell of fluorinated block-copolymer

Stabilizing long-term, low energy surface properties is a key issue in designing fluorinated polymer network, because the fluorinated surface could reorganize or hydrolyze upon contact with water. Here we report an exploring to enhance the low energy surface performance by bonding a dangling shell of fluorinated block copolymer, poly((1H,1H,2H,2H-perfluorodecyl acrylate)-b-poly(caprolactone) (PFDA-b-PCL)), to the polyurethane network. The PFDA and PCL block are the fluorinated shell and the dangling chain, respectively. The fluorinated shell protects the surface from rearrangements and hydrolysis when in contact with water, while the soft polyester block provides the required flexibility for fluorinated components to segregate to the surface. Surfaces with water contact angle up to 120° and surface energy down to 18mN/m were obtained. We then evaluated the effects of fluorinated species on the surface properties of the polyurethane network both with and without the fluorinated shell or polyester spacer. The surfaces functionalized with the fluorinated dangling shell are highly hydrophobic and exhibited better hydrophobic stability. The oligoester spacer connecting the fluorinated shell to the polymer network is critical for the segregation and rebuilding of low energy surfaces.

A combined chemico-mineralogical and tensiometric approach for evaluation of Euganean Thermal Mud (ETM) quality

The tensiometric vs. skin approach (TVS modelling®) is a non-invasive method based on the permutability principle of tensiometry. TVS modelling® is a technologic model that can evaluate the reproducibility of the matrix of thermal mud, its degree of maturation and consequently its skin affinity, in a non-destructive way. This is an essential pre-condition for defining the objective scientific protocols. The surface energy profile of the matrixes is created by a Tenskinmeter®, a tensiometer modified by us for tensiometric measurements on skin. The development of a chemico-mineralogical index (I chmi) based on X-ray fluorescence analysis allows the typical chemico-mineralogical constituents of thermal muds to be determined. The combined TVS-I chmi approach developed here demonstrates the interconnections between the typical chemico-mineralogical components of a Euganean Thermal Mud (ETM) and its energy surface properties. The combined approach also demonstrates the interconnections at the interface between I chmi and the skin affinity of the mud matrix, revealing their typical functional and therapeutic effects.

ChemInform Abstract: A Model Analytic Potential Energy Function for Formyl Radical Decomposition

An analytic function for the ground-electronic-state HCO {yields} H + CO potential energy surface is presented. Both experimental and ab initio data are used to derive parameters for the potential energy surface. Bound-state eigenvalues are obtained, and the results show good agreement with reported experimental and theoretical values. The analytic function is quite flexible and can be easily adjusted to determine how specific potential energy surface properties affect state-specific unimolecular decomposition.

Further explorations of Skyrme-Hartree-Fock-Bogoliubov mass formulas. V. Extension to fission barriers

Large-scale fission barrier calculations have been performed in the framework of the Skyrme-Hartree-Fock model. Our Hartree-Fock-Bogoliubov calculations restore broken symmetries such as translational invariance, particle-number conservation, parity, and, in a more approximate way, rotational invariance. Axial symmetry is imposed, but reflection asymmetry is allowed. The energy surface properties are analyzed with the flooding method. A large set of Skyrme interactions, which were fitted to all known masses under different specific constraints, is used to study the main effects influencing the energy surface and the barrier heights. The principal interaction used in the comparison with experimental barriers is BSk8, the force on which the HFB-8 mass table is based. We found that for nuclei with $92\ensuremath{\le}Z\ensuremath{\le}98$ the agreement of our calculations with experimental data is excellent; the rms deviation on the primary barriers is 0.722 MeV. For lighter nuclei, however, the calculated primary barriers are always too high because of the existence of a third barrier at very high deformations. However, our calculated superheavy barriers appear to be too low, although they are consistent with previous calculations.

Spectroscopic Calibration of Modern Density Functional Methods Using [CuCl4]2-

Density functional theory has become a popular method for studying the electronic structure and potential energy surface properties of large molecules. Its accuracy has been extensively validated for organic and organometallic systems. However, this is not yet the case for classical inorganic compounds with biological importance. This study presents a systematic evaluation of modern DFT calculations using the spectroscopically well understood molecule [CuCl4]2-. The BP86 and B3LYP functionals with saturated basis sets give a ground-state bonding description that is too covalent, and the calculated ligand-field and ligand-to-metal charge transitions are shifted to higher and lower energies, respectively, relative to experiment. A spectroscopically adjusted hybrid DFT functional (B(38HF)P86) was optimized to match the ground-state experimental Cu spin density (0.62 ± 0.02e). This adjusted hybrid functional also gives an improved excited-state description with a rms error in transition energies of 1000 cm-1....

Thermodynamic and structural aspects of the potential energy surface of simulated water.

Relations between the thermodynamics and dynamics of supercooled liquids approaching a glass transition is a topic of considerable interest. The potential energy surface of model liquids has been increasingly studied, since it provides a connection between the configurational component of the partition function on the one hand, and the system dynamics on the other. This connection is most obvious at low temperatures, where the motion of the system can be partitioned into vibrations within a basin of attraction and infrequent interbasin transitions. In this work, we present a description of the potential energy surface properties of supercooled liquid water. The dynamics of this model have been studied in great detail in recent years. We locate the minima sampled by the liquid by "quenches" from equilibrium configurations generated via molecular dynamics simulations, and then calculate the temperature and density dependence of the basin energy, degeneracy, and shape. The temperature dependence of the energy of the minima is qualitatively similar to simple liquids, but has anomalous density dependence. The unusual density dependence is also reflected in the configurational entropy, the thermodynamic measure of degeneracy. Finally, we study the structure of simulated water at the minima, which provides insight on the progressive tetrahedral ordering of the liquid on cooling.

Semiempirical MNDO, AM1, and PM3 direct dynamics trajectory studies of formaldehyde unimolecular dissociation

Direct dynamics calculations are performed, using the semiempirical neglect of diatomic differential overlap (NDDO) molecular orbital theory, to explore the level of electronic structure theory required to accurately describe the product energy partitioning when formaldehyde dissociates into hydrogen and carbon monoxide. Trajectories are initiated at the saddlepoint and are propagated for the short time needed to form products, by obtaining the energy and gradient directly from the NDDO theory. The resulting product energy partitioning is compared to available experimental data and the findings of two previous trajectory studies, including one ab initio trajectory study at the HF/6-31G** level of theory [Chem. Phys. Lett. 228, 436 (1994)]. The MNDO, AM1, and PM3 semiempirical Hamiltonians are studied, as well as Hamiltonians based on specific reaction parameters (SRP). For the latter, the original PM3 and AM1 parameters are adjusted to reproduce some ab initio potential energy surface properties, such as stationary points and part of the reaction path. A series of NDDO-SRP Hamiltonians are chosen by fitting different features of a HF/6-31G** potential energy surface. Only qualitative agreement is found between the product energy distributions of the NDDO-SRP Hamiltonians and that of the HF/6-31G** Hamiltonian. This result is consistent with the well known difficulty of reproducing a HF/6-31G** Hamiltonian with a NDDO-SRP model, since dynamic correlation is not treated in ab initio SCF, but is incorporated into semiempirical methods. Trajectory results with NDDO-SRP Hamiltonians, which reproduce a few experimental and/or high-level ab initio stationary points, are in poor agreement with the experimental product energy partitioning. Reparameterizing the NDDO Hamiltonian is laborious, and only a few properties of the potential energy surface can be reproduced at the same time. This indicates the limitations of the NDDO-SRP approach, which might be well suited for locally interpolating ab initio data, but not for quantitatively describing global potential energy surfaces.

Trajectory Studies of SN2 Nucleophilic Substitution. 5. Semiempirical Direct Dynamics of Cl-- - -CH3Br Unimolecular Decomposition

Direct dynamics simulations of the dynamics of the Cl-- - -CH3Br complex are performed for 25 ps or until either Cl- + CH3Br or ClCH3 + Br- are formed. Two different potential energy surfaces, AM1-SRP1 and AM1-SRP2, are investigated in the simulations by using the AM1 semiempirical model with two different sets of specific reaction parameters (SRPs). The AM1-SRP surfaces give non-RRKM unimolecular dynamics for Cl-- - -CH3Br as found in a previous simulation based on an analytic potential energy surface, PES1(Br), derived by fitting HF/SV4PP/6-31G* ab initio calculations and experimental data. However, detailed aspects of the Cl-- - -CH3Br intramolecular and unimolecular dynamics are different for the two AM1-SRP surfaces and in some cases strikingly different from those found for the PES1(Br) surface. Global potential energy surface properties, not only those of stationary points and along the reaction path, are expected to influence the Cl-- - -CH3Br nonstatistical dynamics. Of the three surfaces, only PES1(Br) gives a relative translation energy distribution for the ClCH3 + Br- dissociation products which agrees with experiment. The average product translational energy is approximately a factor of 3 too large for each of the AM1-SRP surfaces. A definitive determination of all the dynamics and kinetics for Cl- + CH3Br → ClCH3 + Br- SN2 nucleophilic substitution may require dynamical calculations based on a potential energy surface derived from high-level ab initio calculations.

A Model Multidimensional Analytic Potential Energy Function for the Cl- + CH3Br .fwdarw. ClCH3 + Br- Reaction

Hartree-Fock calculations, utilizing the SV4PP split valence contracted Gaussian basis set for Cl and Br and the 6-31G * basis set for CH 3 , are used to determine potential energy surface properties for the Cl - +CH 3 Br→ClCH 3 +Br - S N 2 nucleophilic substitution reaction. This ab initio information is used in concert with experimental data to develop a multidimensional analytic potential energy function for the Cl - +CH 3 Br reaction system, by modifying the analytic potential energy function developed previously for Cl a - +CH 3 Cl b →Cl a CH 3 +Cl b -

A model analytic potential energy function for formyl radical decomposition

An analytic function for the ground-electronic-state HCO {yields} H + CO potential energy surface is presented. Both experimental and ab initio data are used to derive parameters for the potential energy surface. Bound-state eigenvalues are obtained, and the results show good agreement with reported experimental and theoretical values. The analytic function is quite flexible and can be easily adjusted to determine how specific potential energy surface properties affect state-specific unimolecular decomposition.

A semi-empirical canonical variational transition state theory model for association reactions without potential energy barriers

A simple semi-empirical model is found to explain numerous trends observed in canonical variational transition state theory calculations for association reactions. The trends include the relationship of canonical transition state structures to potential energy surface properties, temperature, and rotational angular momentum. The model gives near quantitative results for H + CH 3→CH 4 association.

Some excited-state properties of 4-(9-anthryl)-N,N,2,3,5,6-hexamethylaniline

an interesting approach to the potential function of the hydroperoxyl radical that appeared after this work was completed. Lemon and Ha~e~~ suggest a switching function formalism and extensions of BEB056 concepts in a manner that may enable one to relate potential energy surface properties to dynamical and kinetic attributes of the

Properties of variational transition states for association reactions

The relationships between the structures of microcanonical variational transition states for association reactions and potential energy surface properties are analyzed. The analysis is facilitated by the recent finding that in many cases the vibrational frequencies for the transitional modes in the association reaction vary exponentially with the reaction coordinate. An increase in the attenuation of the transitional mode frequencies results in a tighter transition state. Long-range minimum energy path potentials of the form − c/ r″ have only one transition state at each energy. Certain types of association reactions may not have transition states.

Unimolecular and intramolecular dynamics. Relationship to potential energy surface properties

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTUnimolecular and intramolecular dynamics. Relationship to potential energy surface propertiesWilliam L. HaseCite this: J. Phys. Chem. 1986, 90, 3, 365–374Publication Date (Print):January 1, 1986Publication History Published online1 May 2002Published inissue 1 January 1986https://doi.org/10.1021/j100275a003RIGHTS & PERMISSIONSArticle Views174Altmetric-Citations68LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (3 MB) Get e-Alerts

ChemInform Abstract: EVALUATION OF THE RATE COEFFICIENTS AND ARRHENIUS PARAMETERS OF HYDROGEN ATOM TRANSFER REACTIONS. II. APPLICATION OF THE METHOD

The bond-strength–bond-length (BSBL) method was used to estimate Arrhenius parameters and rate coefficients for various hydrogen atom transfer reactions of the type A + BC AB + C. In most cases predicted activation energies agreed within 1.2 kcal/mol with the experimental values (average error = 1.12 and standard deviation = 1.42), and the calculated log A agreed within 0.55 log units with the literature data (average error = 0.47 and standard deviation = 0.57). Predicted activated complex properties were shown to agree very well with potential energy surface properties obtained from ab initio quantum mechanical calculations. Detailed comparison of the BSBL results and the results of bond-energy–bond-order (BEBO)-type calculations are presented.

Evaluation of the rate coefficients and arrhenius parameters of hydrogen atom transfer reactions. II. Application of the method

AbstractThe bond‐strength–bond‐length (BSBL) method was used to estimate Arrhenius parameters and rate coefficients for various hydrogen atom transfer reactions of the type A + BC → AB + C. In most cases predicted activation energies agreed within 1.2 kcal/mol with the experimental values (average error = 1.12 and standard deviation = 1.42), and the calculated log A agreed within 0.55 log units with the literature data (average error = 0.47 and standard deviation = 0.57). Predicted activated complex properties were shown to agree very well with potential energy surface properties obtained from ab initio quantum mechanical calculations. Detailed comparison of the BSBL results and the results of bond‐energy–bond‐order (BEBO)‐type calculations are presented.