Alternating copolymerization of bis(hexafluoroisopropyl) fumarate with styrene and vinyl pentafluorobenzoate: Transparent and low refractive index polymers

Bis(hexafluoroisopropyl) fumarate (BHFIPF) did not homopolymerize with free radical initiators. However, BHFIPF yielded alternating copolymers with styrene in bulk with Azobisisobutyronitrile (AIBN) as a radical initiator. The monomer reactivity ratios of BHFIPF (M₁) and styrene (M₂) were calculated as r₁ = 0.00 and r₂ = 0.02. BHFIPF also copolymerized with vinyl pentafluorobenzoate (VPFB) in bulk and in pentafluoroisopropanol solution to produce an alternating copolymer. The reactivity ratios of BHFIPF (M₁) with VPFB (M₂) were r₁ = 0.00 and r₂ = 0.05 in bulk and r₁ = 0.01 and r₂ = 0.11 in pentafluoroisopropanol, respectively. The glass transition temperatures (T_g) of the BHFIPF‐styrene and BHFIPF‐VPFB copolymers were 107 and 86 °C, respectively. The BHFIPF‐styrene copolymer was thermally stable, and the thermal degradation temperature (T_d) was 400 °C, whereas the T_d of BHFIPF‐VPFB copolymer was 240 °C. The films obtained by casting from tetrahydrofuran (THF) solutions of these copolymers were flexible and transparent. Their refractive indices were 1.4048 for the BHFIPF‐styrene copolymer, and 1.3980 for the BHFIPF‐VPFB copolymer at 633 nm, respectively. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Theoretical Auger electron spectra of polymers by density functional theory calculations using model dimers

We propose a new approach for analysis of Auger electron spectra (AES) of polymers by density functional theory (DFT) calculations with the Slater's transition-state concept. Simulated AES and X-ray photoelectron spectra (XPS) of four polymers [(CH2CH2)n (PE), (CH2CH(CH3))n (PP), (CH2CH(OCH3))n (PVME), and (CH2CH(COCH3))n (PVMK)] by DFT calculations using model dimers are in a good accordance with the experimental ones. The experimental AES of the polymers can be classified in each range of 1s-2p2p, 1s-2s2p, and 1s-2s2s transitions for C KVV and O KVV spectra, and in individual contributions of the functional groups from the theoretical analysis.     

UV‐induced refractive index modulation of photoreactive polymers bearing N‐acylcarbazole groups

In this study, we report on the synthesis and characterization of photoreactive polymers bearing N‐acetylcarbazole and N‐formylcarbazole groups, respectively. These polymers were easily accessible by polymer analogous acylation of commercially available poly‐(2‐vinylcarbazole). While poly(1‐(2‐vinyl‐9H‐carbazol‐9‐yl)ethanone) (poly‐ 1 ) undergoes a partial photochemical Fries rearrangement, poly(2‐vinyl‐9H‐carbazole‐9‐carbaldehyde) (poly‐ 2 ) decarbonylates smoothly when exposed to UV irradiation. The difference in reactivity between the two acylated polymers is because of the lower stability of the formyl radical, which is formed in the first stage of this photoreaction. Ellipsometric measurements of thin films showed that the photo‐Fries rearrangement in poly‐ 1 causes a change in refractive index by Δn = +0.01 at 650 nm. UV illumination of poly‐ 2 results in a change of the refractive index by Δn = +0.03 at 650 nm, which can be explained by the high yield of the photodecarbonylation of the N‐formylcarbazole groups. Refractive index patterns can be easily realized using lithographic techniques as demonstrated by optical microscopy using a phase contrast set‐up for visualization. Patterned films of poly‐ 1 and poly‐ 2 with feature sizes of about 5 μm were obtained with a mask aligner. Photoreactive polymers bearing N‐acylcarbazole groups are of potential interest for optical applications such as waveguides, optical switches, and data storage devices. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Viscosity and refractive index adjustment of poly(methyl methacrylate‐co‐ethyleneglycol dimethacrylate) for application in microoptics

Polymer optical components like waveguides or lenses are gaining more and importance as passive or active devices enabling the formation of a sensor and detector platform, e.g. for monitoring the health of large area functional surfaces, which are difficult to access like the wings of an off‐shore wind energy plant. With respect to low‐loss waveguiding and the use of chemical and mechanical stable polymers there is a need to tailor the optical as well as the thermomechanical properties. The given approach describes the addition of electron‐rich small organic molecules like phenanthrene to a poly(methyl methacrylate)‐based polymer matrix enabling a significant refractive index increase from 1.49 up to almost 1.55 (@589 nm). As undesirable side effects the optical transmittance in the visible range at higher guest molecule content is reduced, and a pronounced plasticizing occurs. Both hamper the application of the mixture, e.g. as optical waveguide material. The plasticizing and the accompanied drop of the glass transition temperature, determining the maximum operation temperature, can be partially compensated by the copolymerization of the methyl methacrylate monomer (MMA) with the difunctional monomer ethyleneglycol dimethacrylate (EGDMA) at certain crosslinker content. The resulting new developed guest–host mixtures enable the realization of optical devices with adjusted rheological behavior prior to curing and tailored optical properties after polymerization. Copyright © 2015 John Wiley & Sons, Ltd.     

用密度泛函理论预测酚类化合物的正辛醇/水分配系数

利用密度泛函理论(DFT),基于B3LYP/6-31G(d,p)和B3LYP/6-311G(d,p)两种水平计算了36种酚类化合物的分子结构参数和热力学参数,建立了两种水平的正辛醇/水分配系数(Kow)的定量结构-性质关系模型;确定相关系数(R)分别为0.988和0.988,交叉验证系数(q2)分别为0.94和0.96...     

Novel silylphenol antioxidants by density functional theory

We have scrutinized five novel silylphenol antioxidants, including 2-silylphenol ( 1 ), 4-silylphenol ( 2 ), 2,6-disilylphenol ( 3 ), 2,4-disilylphenol ( 4 ), and 2,4,6-trisilylphenol ( 5 ), at M06/6–311++G** level of theory. To evaluate the antioxidant efficiency, the electronic effects on O─H bond dissociation energy (BDE) and vertical ionization potential (IP_v) of 1 – 5 are investigated, which are mainly governed by electronic effects. The conductor-like polarized continuum model (CPCM) is applied to measure the antioxidant capacity in the solution phase. The results show that antioxidants with the lowest BDE and IP_v values can efficiently act via hydrogen atom transfer (HAT) and single electron transfer (SET) mechanisms, respectively. The stability of resulting radicals is measured by nucleus independent chemical shift (NICS) index, natural bond orbital (NBO) analysis, and nucleophilicity (N) index. The BDE shows lower values in the gas phase with respect to water, while water exhibits lower IP_v values than gas. Structure 5 turns out as the most efficient antioxidant. The overall order of antioxidant efficiency in both gas and water phases is 5 > 2 > 3 > 4 > 1 .     

eQE: An open‐source density functional embedding theory code for the condensed phase

In this work, we present the main features and algorithmic details of a novel implementation of the frozen density embedding (FDE) formulation of subsystem density functional theory (DFT) that is specifically designed to enable ab initio molecular dynamics (AIMD) simulations of large‐scale condensed‐phase systems containing 1000s of atoms. This code (available at http://eqe.rutgers.edu ) has been given the moniker of embedded Quantum ESPRESSO (eQE) as it is a generalization of the open‐source Quantum ESPRESSO (QE) suite of programs. The strengths of eQE reside in a hierarchical parallelization scheme that allows for an efficient and fully self‐consistent treatment of the electronic structure (via the addition of an additional DIIS extrapolation layer) while simultaneously exploiting the inherent symmetries and periodicities in the system (via sampling of subsystem‐specific first Brillouin zones and utilization of subsystem‐specific basis sets). While bulk liquids and molecular crystals are two classes of systems that exemplify the utility of the FDE approach (as these systems can be partitioned into weakly interacting subunits), we show that eQE has significantly extended this regime of applicability by outperforming standard semilocal Kohn–Sham DFT (KS‐DFT) for large‐scale heterogeneous catalysts with quite different layer‐specific electronic structure and intrinsic periodicities. eQE features very favorable strong parallel scaling for a model system of bulk liquid water composed of 256 water molecules, which allows for a significant decrease in the overall time to solution when compared to KS‐DFT. We show that eQE achieves speedups greater than one order of magnitude ( ) when performing AIMD simulations of such large‐scale condensed‐phase systems as: (1) molecular liquids via bulk liquid water represented by 1024 independent water molecules (3072 atoms with a 25.3× speedup over KS‐DFT), (2) polypeptide/biomolecule solvation via (gly )₆ solvated in (H₂O)₃₉₅ (1230 atoms with a 38.6× speedup over KS‐DFT), and (3) molecular crystals via a 3 × 3 × 3 periodic supercell of pentacene (1940 atoms with a 12.0× speedup over KS‐DFT). These results represent a significant improvement over the current state‐of‐the‐art and now enable subsystem DFT‐based AIMD simulations of realistically sized condensed‐phase systems of interest throughout chemistry, physics, and materials science.     

Control of refractive index of sol-gel tungsten oxide films

Tungsten oxide films were prepared by a complexing agent-assisted sol-gel process. All the films were at 500°C were crystalline and transparent. The refractive index n and extinction coefficient k of the films were calculated from the transmittance and reflectance spectra in the visible and infrared regions. The values of n were lowered to depend on the organic ligands used in the preparation of the sols. The use of such ligands may be a mean to control the refractive index of coatings.     

Applying the concepts of density functional theory to simple systems

Equations are derived for the chemical potential and local hardness of the ground states of helium and the related two electron ions. With these properties it is possible to correct the energies of the simple single‐zeta wave functions to the nearly exact values. The calculations are simple for these simple systems. In principle, it is possible to extend this method to all atoms and molecules. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Synthesis and characterization of functionalized carbon black/poly(vinyl alcohol) high refractive index nanocomposites

Carbon black(CB)/polymer composites with high refractive index(RI) were fabricated from poly(vinyl alcohol) (PVA) and covalently functionalized nano-CB(PVA-es-CB) by simple esterification reaction.Transmission electron microscopy showed that uniform aggregates of PVA-es-CB nanoparticles with a size smaller than 100 nm formed in the nanocomposite films.EUipsometric measurements indicated that the PVA-es-CB/PVA composite films had a RI in the range 1.520-1.598 linearly increased with the PVA-es-CB volume content.Theoretical equation based on Lorentz-Lorenz theory provided reasonably close estimation of the refractive indices to the experimentally observed values.The hybrid films also revealed relatively good surface planarity,thermal stability and optical transparency.     

Electrophilicity kernel and its hierarchy through softness in conceptual density functional theory

In the context of long‐range density functional theory of softness kernel, the concepts of local and kernel electrophilicity are developed to obtain the local to global hierarchical criteria such as bilocal symmetry, asymptotic behavior, and integral local to global relationships. Further development into potential‐density dependence is also provided while considering the local plus nonlocal specification of softness kernel and the associated atomic scales for the derived kernel; local and global electrophilicity are provided whose reliability is judged through the periodical features along the periodic table especially for the alkali metal atoms and the halogen atoms. © 2013 Wiley Periodicals, Inc.