Dehydrocoupling and Diels–Alder reactions on siloxane polymers

Dehydrocoupling reactions between linear poly(methylhydrosiloxane) {Me₃SiO–[MeSi(H)O]_n–SiMe₃} and alcohols such as cholesterol, anthracene‐9‐carbinol, (12‐crown‐4)‐2‐carbinol, pyrene‐1‐carbinol, 4‐methyl‐5‐thiazoleethanol, and 4‐pyridilpropanol were introduced under catalytically mild conditions. The degrees of conversion of Si? H bonds in polysiloxane were monitored with ¹H NMR spectra. The reaction of the 9‐methoxyanthracene adduct on siloxane polymers and maleimide derivatives (maleimide, N‐ethylmaleimide, and maleic acid anhydride) produced [2+4]‐cycloadducts in very high yields. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4013–4019, 2002     

Analytical TDHF second derivatives of dynamic electronic polarizability with respect to nuclear coordinates. Application to the dynamic ZPVA correction

Analytical calculation of second derivatives of the dynamic electronic polarizability with respect to vibrational normal coordinates has been implemented at the TDHF level of approximation. Important simplifications are obtained by using the 2n+1 rule and interchange relations. In application to small molecules the first‐order ZPVA correction is found to have greater frequency dispersion than the electronic polarizability, but the former remains small in comparison. For the linear polyenes, C_2nH_2n+2 (n=1–3), the percentage ZPVA correction decreases with chain length for all ?ω<0.10 a.u. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1920–1932, 2001     

Tayloring standard TDDFT approaches for computing UV/Vis transitions in thiocarbonyl chromophores

We report the development of an accurate computational procedure for the calculation of the n → π* (λ_max?1) and π → π* (λ_max?2) transitions of a set of thiocarbonyl derivatives. To ensure converged results, all calculations are carried out using the 6‐311+G(2df,p) basis set for time‐dependent calculations, and the 6‐311G(2df,p) for the ground‐state geometrical optimization. Starting with two hybrids, PBE0 and B3LYP, the Hartree–Fock exchange percentage (α) used is optimized in order to reach excitation energies that fit experimental data. It turns out that BLYP(α) is the more adequate functional for calibration. For the n → π* excitation, the optimal α value lies in the 0.10–0.20 interval, whereas for the π → π* process setting α equal to 0.10 provides the most accurate results. The corresponding mean absolute errors (MAE) are limited to 17 nm for λ_max?1, and to 10 nm for λ_max?2, allowing a consistent and accurate prediction of both transitions. We also assess the merits of the ZINDO//AM1 scheme and it turns out that the semi‐empirical method only provides a poor prediction of the λ_max of thiocarbonyl derivatives, especially for the n → π* transition. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Synthesis of end‐functionalized poly(methyl methacrylate) by ruthenium‐catalyzed living radical polymerization with functionalized initiators

A series of functionalized 2‐bromoisobutyrates and 2‐chloro‐2‐phenylacetates led to α‐end‐functionalized poly(methyl methacrylate)s in Ru(II)‐catalyzed living radical polymerization; the terminal functions included amine, hydroxyl, and amide. These initiators were effective in the presence of additives such as Al(Oi‐Pr)₃ and n‐Bu₃N. The chlorophenylacetate initiators especially coupled with the amine additive gave polymers with well‐controlled molecular weights (M_w/M_n = 1.2–1.3) and high end functionality (F_n ～ 1.0). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1937–1944, 2002     

Synthesis and characterization of fluorine‐containing polyesters by the polyaddition of bis(epoxide)s with active diesters

The synthesis and optical properties of polyesters with pendant fluorinated phenoxy groups were examined. The polyaddition of bisphenol AF diglycidyl ether ( 1 ) with fluorine‐containing terephtalates ( 2a–f ) was carried out with tetrabutylphosphonium chloride (TBPC) as the catalyst in chlorobenzene to afford the corresponding polyesters with number‐average molecular weights (M_n's) ranging from 15,200 to 30,000 in 88–96% yields. Furthermore, the polyaddition of 1 with isophthalate 2g and phthalate 2h also produced high‐molecular‐weight polyesters with M_n's = 22,700 and 22,600 in 88 and 84% yields, respectively. The linear relationship was observed between the fluorine contents and refractive indices of the obtained polyesters. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 213–222, 2003     

Photophysics of Schiff Bases: Theoretical Study of Salicylidene Methylamine

The proton‐transfer reaction in a model aromatic Schiff base, salicylidene methylamine (SMA), in the ground and in the lowest electronically‐excited singlet states, is theoretically analyzed with the aid of second‐order approximate coupled‐cluster model CC2, time‐dependent density functional theory (TD‐DFT) using the Becke, three‐parameter Lee–Yang–Parr (B3LYP) functional, and complete active space perturbation theory CASPT2 electronic structure methods. Computed vertical‐absorption spectra for the stable ground‐state isomers of SMA fully confirm the photochromism of SMA. The potential‐energy profiles of the ground and the lowest excited singlet state are calculated and four photophysically relevant isomeric forms of SMA; α, β, γ, and δ are discussed. The calculations indicate two S₁/S₀ conical intersections which provide non‐adiabatic gates for a radiationless decay to the ground state. The photophysical scheme which emerges from the theoretical study is related to recent experimental results obtained for SMA and its derivatives in the low‐temperature argon matrices (J. Grzegorzek, A. Filarowski, Z. Mielke, Phys. Chem. Chem. Phys. 2011 , 13, 16596–16605). Our results suggest that aromatic Schiff bases are potential candidates for optically driven molecular switches.     

Atom transfer radical copolymerization of n‐hexylmaleimide and styrene in an ionic liquid

Dendritic polyarylether 2‐bromoisobutyrates of different generations (Gn‐Br, n = 1–3) as macroinitiators for the atom transfer radical copolymerization of N‐hexylmaleimide and styrene in an ionic liquid, 1‐butyl‐3‐methylimidazolium hexafluorophosphate, were investigated. The copolymerization carried out in the ionic liquid with CuBr/pentamethyldiethylenetriamine as a catalyst at room temperature afforded polymers with well‐defined molecular weights and low polydispersities (1.18 < M_w/M_n < 1.36, where M_w is the weight‐average molecular weight and M_n is the number‐average molecular weight), and the resultant copolymers possessed an alternating structure over a wide range of monomer feeds (f₁ = 0.3–0.8). Meanwhile, the copolymerization was also conducted in anisole at 110 °C under similar conditions so that the effect of the reaction media on the polymerization could be evaluated. The monomer reactivity ratios showed that the tendency to form alternating copolymers for the two monomers was stronger in ionic liquids than in anisole. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3360–3366, 2002     

C?H bond dissociation enthalpies of fluorinated formates and estimation of their rate constants for the reactions with OH radicals: A DFT study

Density functional theory was used to estimate the lifetime of fluorinated formates, which are primary products from the oxidation of hydrofluoroethers. First, the C? H bond dissociation enthalpies (BDEs) of 10 fluorinated formates, C_nF_{2n + 1}OC(O)H (n = 1–4) and C_nHF_2nOC(O)H (n = 1–3) have been calculated by using the density functional theory with (RO)B3LYP/6‐311G(d,p). Secondly, from these computed BDEs, the rate constants k_OH of the hydrogen abstraction reaction between the fluorinated formates and OH radicals have been estimated using the formulation proposed by Heicklen (Int. J. Chem. Kinet. 13 , 651, 1981). We modified the formulation proposed by Heicklen in order to relate BDEs to k_OH for formates based on the results of the ab initio studies using standard transition state theory with the G2(MP2) level. Consequently, the k_OH of all the formates considered here are estimated to be around 1.5–4.7 × 10^?14 cm³ molecule^?1 s^?1 at 298 K. Their lifetimes concerning with the decomposition by OH radicals (τ_OH) in atmosphere have been evaluated as 0.4–4.5 years from the estimated k_OH. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 524–530, 2002     

Curing kinetics of boron‐containing phenol–formaldehyde resin formed from paraformaldehyde

A boron‐containing phenol–formaldehyde resin (BPFR) was synthesized from boric acid, phenol, and paraformaldehyde. The curing reaction of BPFR was studied by Fourier‐transform infrared spectrometry and differential scanning calorimetry. According to the heat evolution behavior during the curing process, several influencing factors on isothermal curing reaction were evaluated. The results show that the isothermal kinetic reaction of BPFR follows autocatalytic kinetics mechanism, and kinetic parameters m, n, k₁, and k₂, were derived, respectively. In the latter reaction stage, the curing reaction becomes controlled mainly by diffusion. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 638–644, 2002     

Supersymmetry approaches to the radial bound states of the hydrogen‐like atoms

Various structural possibilities for Al_nN and Al_nN₂ (n = 1–7) neutral and cationic isomers are investigated, using the density functional method of Becke's three‐parameter hybrid exchange functional with the Lee–Yang–Parr nonlocal correlation. Structural optimization and frequency analyses are performed with the basis of 6‐311+G(d) for both the neutrals and cations. The calculations predicted the existence of a number of previously unknown isomers (i.e., Al₅N₂ and Al₆N₂). The resulting geometries show that the nitrogen atom prefers to be trapped and not to be on the periphery. Frequency analyses indicate that the 3‐D Al₅N, which was previous proposed as the ground‐state structure, is in fact a first‐order stationary point with an imaginary frequency at 45i (a₂). The optimized ground‐state structure of Al₅N obtained in this work is a planar configuration with the symmetry of C_2v. The calculated adiabatic ionization potentials in their ground states showed that AlN, Al₂N, Al₃N, and Al₄N₂ clusters are more stable than any others in Al_nN and Al_nN₂ (n = 1–7) species, being consistent with the observed time‐of‐flight (TOF) signal intensities. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Polymerization of phenylacetylene by iridium catalysts

Polymerization of phenylacetylene (PA) with [(cod)IrCl]₂‐based catalysts (cod: 1,5‐cyclooctadiene) was examined. The [(cod)IrCl]₂/n‐BuLi and [(cod)IrCl]₂/Ph₂C?C(Ph)Li systems induced the polymerization of PA to produce polymers with a number‐average molecular weight (M_n) of around several thousand in rather low yields. On the other hand, the catalyst composed of [(cod)IrCl]₂, norbornadiene (nbd), Ph₃P, and Ph₂C?C(Ph)Li (molar ratio of 1:1:1.1:2) produced polymer in a high yield (ca. 80%) in toluene at 0 °C. The resulting polymer showed a bimodal gel permeation chromatographic profile (M_n = 209,000 and 4300; ratio: 81/19). On the basis of these findings, the presence of two active species, that is, Ir complexes with nbd and cod, are discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1075–1080, 2002     

Energy spectrum of extended Hubbard model with spin‐dependent hopping and related spin ladder model

We studied the energy spectrum of the 1‐D extended Hubbard model with spin‐dependent hopping and related spin ladder system formed by two coupled XXZ spin 1/2 chains with the interchain interaction of Ising type. It was proved that the model excitation spectrum has no gap excepting some special values of z‐projection of the ground‐state total spin. The thorough analytic consideration of two‐magnon states was given. The existence up to five bound states at specified value of quasimomentum of the pair of inverted spins was shown. We also present the results of density matrix renormalization group calculations that showed nonadequacy of the pair approximation for n‐magnon bound states of the extended model with the strong electron–electron interactions. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

Synthesis and characterization of well‐defined ABC‐type triblock copolymers via atom transfer radical polymerization and stable free‐radical polymerization

An asymmetric difunctional initiator 2‐phenyl‐2‐[(2,2,6,6 tetramethylpiperidino)oxy] ethyl 2‐bromo propanoate ( 1 ) was used for the synthesis of ABC‐type methyl methacrylate (MMA)‐tert‐butylacrylate (tBA)‐styrene (St) triblock copolymers via a combination of atom transfer radical polymerization (ATRP) and stable free‐radical polymerization (SFRP). The ATRP‐ATRP‐SFRP or SFRP‐ATRP‐ATRP route led to ABC‐type triblock copolymers with controlled molecular weight and moderate polydispersity (M_w/M_n < 1.35). The block copolymers were characterized by gel permeation chromatography and ¹H NMR. The retaining chain‐end functionality and the applying halide exchange afforded high blocking efficiency as well as maintained control over entire routes. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2025–2032, 2002     

Kinetic study of the reactions of oxoiron(IV) with aromatic substrates in aqueous solutions

The kinetics of the reactions of oxoiron(IV) (FeO²⁺) with phenol, nitrobenzene, m‐, o‐, and p‐nitrophenol in 1 M HClO₄ was investigated by the stopped‐flow technique. The rate constants of these reactions decrease with increasing the one‐electron reduction potentials of the corresponding radical cations of the substrates and with the Hammett parameter of the NO₂ group in the phenol ring. A reaction mechanism is proposed, which accounts for the observed trends and for the nature of the reaction products. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 488–494, 2002     

Synthesis of star‐shaped copolymers with methyl methacrylate and n‐butyl methacrylate by metal‐catalyzed living radical polymerization: Block and random copolymer arms and microgel cores

Various star‐shaped copolymers of methyl methacrylate (MMA) and n‐butyl methacrylate (nBMA) were synthesized in one pot with RuCl₂(PPh₃)₃‐catalyzed living radical polymerization and subsequent polymer linking reactions with divinyl compounds. Sequential living radical polymerization of nBMA and MMA in that order and vice versa, followed by linking reactions of the living block copolymers with appropriate divinyl compounds, afforded star block copolymers consisting of AB‐ or BA‐type block copolymer arms with controlled lengths and comonomer compositions in high yields (≥90%). The lengths and compositions of each unit varied with the amount of each monomer feed. Star copolymers with random copolymer arms were prepared by the living radical random copolymerization of MMA and nBMA followed by linking reactions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 633–641, 2002; DOI 10.1002/pola.10145     

Theoretical studies of structural and electronic properties of AlnAsn clusters

We present theoretical results of size dependent structural, electronic, and optical properties of ligand‐free stoichiometric Al_nAs_n clusters of zinc‐blende modification. The investigation is done using a simplified parametrized linear combination of atomic orbital–density functional theory‐local density approximation–tight‐binding (LCAO–DFT–LDA–TB) method and consider clusters with n up to around 100. Initial structures have assumed as spherical parts of infinite zinc‐blende structure and then allowed to relax to the closest local‐energy‐minimum structure. We analyze the radial distributions of atoms, Mulliken populations, electronic energy levels (in particular, HOMO and LUMO), bandgap, and stability as a function of size and composition. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Cationic copolymerization of indene with styrene derivatives: Synthesis of random copolymers of indene with high molecular weight

Random copolymers with high molecular weights of indene and p‐methylstyrene (pMeSt) were synthesized by cationic polymerization with trichloroacetic acid/tin tetrachloride in CH₂Cl₂ at low temperatures. When indene and pMeSt (1:1 v/v), for example, were polymerized at ?40 °C, both monomers were consumed at very similar rates to give a copolymer with high molecular weight [number‐average molecular weight (M_n): 8–9 × 10⁴]. This is indeed quite unexpected behavior for the combination of these two monomers because pMeSt polymerized over 1000 times faster than indene in the homopolymerization under the reaction conditions previously described. The product copolymer of indene and pMeSt had a random monomer sequence in it that was confirmed by NMR analyses and thermal‐property measurements. In sharp contrast with pMeSt, styrene and p‐chlorostyrene, which have no electron‐donating groups on the phenyl ring, led to low molecular weight polymers (M_n < 10,000) in the copolymerization with indene (1:1 v/v). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2449–2457, 2002     

Iron‐catalyzed living radical polymerization of acrylates: Iodide‐based initiating systems and block and random copolymerizations

A half‐metallocene iron iodide complex [Fe(Cp)I(CO)₂] induced living radical polymerization of methyl acrylate (MA) in conjunction with an iodide initiator [(CH₃)₂C(CO₂Et)I, 1 ] and Al(Oi‐Pr)₃ to give polymers of controlled molecular weights and narrow molecular weight distributions (MWDs) (M_w/M_n < 1.2). With the use of chloride and bromide initiators, the MWDs were broader, whereas the molecular weights were similarly controlled. Other acrylates such as n‐butyl acrylate (nBA) and tert‐butyl acrylate (tBA) can be polymerized with 1 /Fe(Cp)I(CO)₂ in the presence of Ti(Oi‐Pr)₄ and Al(Oi‐Pr)₃, respectively, to give living polymers. The 1 /Fe(Cp)I(CO)₂ initiating system is applicable for the synthesis of block and random copolymers of acrylates (MA, nBA, and tBA) and styrene of controlled molecular weights and narrow MWDs (M_w/M_n = 1.2–1.3). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2033–2043, 2002     

Radical copolymerization of alkyl cyclobutenecarboxylates fused with cycloaliphatic framework with alkyl (meth)acrylates

Radical copolymerization behavior of alkyl cyclobutenecarboxylate‐derivatives 4‐6 and related norbornene‐derived compounds 7–9 is described. A variety of alkyl cyclobutenecarboxylates fused with cycloaliphatic framework ( 4–6 ) were prepared by [2 + 2] cycloaddition of five, six, and eight‐membered cycloolefins with alkyl propiolates [alkyl = Me, 2‐hydroxyethyl, and 3‐γ‐butyrolactonyl (γ‐BL)]. The fused cyclobutenecarboxylates 4–6 were radically copolymerized with n‐butyl acrylate (nBA) to afford random copolymers, and terpolymerized with alkyl methacrylates with bulky ester groups [alkyl = γ‐BL and 3‐(3‐methyladamantyl)]. The cyclobutane‐containing bicyclic framework incorporated in the resulting polymer backbone contributes to raising T_g of resulting copolymers. Similar results were obtained when a mixture of related norbornene‐derived compounds were used as monomers with an apparently enhanced T_g‐raising effect in the copolymerization with nBA. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2716–2724     

GRECP/5e‐MRD‐CI calculation of the electronic structure of PbH

The correlation calculation of the electronic structure of PbH is carried out with the generalized relativistic effective core potential (GRECP) and multireference single‐ and double‐excitation configuration interaction (MRD‐CI) methods. The 22‐electron GRECP for Pb is used and the outer core 5s, 5p, and 5d pseudospinors are frozen using the level‐shift technique, so only five external electrons of PbH are correlated. A new configuration selection scheme with respect to the relativistic multireference states is employed in the framework of the MRD‐CI method. The [6, 4, 3, 2] correlation spin–orbit basis set is optimized in the coupled cluster calculations on the Pb atom using a recently proposed procedure, in which functions in the spin–orbital basis set are generated from calculations of different ionic states of the Pb atom and those functions are considered optimal that provide the stationary point for some energy functional. Spectroscopic constants for the two lowest‐lying electronic states of PbH (²Π_1/2, ²Π_3/2) are found to be in good agreement with the experimental data. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002