Ultrasonic Solution Degradations of Polystyrene and Substituted Polystyrenes in Tetrahydrofuran as Solvent

Abstract

Ultrasonic (70 W, 20 kHz) solution (2% THF) degradations of polystyrene (PS), poly(α-methylstyrene) (PαMeS), poly(p-isopropyl α-methylstyrene) (PpiPrαMeS), poly(p-chlorostyrene) (PpCIS), poly(p-bromostyrene) (PpBrS), and poly(p-methoxystyrene) (PpOMeS) have been carried out in tetrahydrofuran at 27° C. The average number of chain scissions S (where S = [(M _n)₀/(M _n)_t] - 1), computed from the overall values of [(M _n)₀ and (M _n)_t, were found to be different from those of S' (where S' = α([(M _n)₀/(M _n)_t] - 1)) based on the component (only that part of the polymer which is involved in degradation) data of the weight fraction (α), (M _n)₀, and (M _n)_t), S' for polystyrene and substituted polystyrene follows the order PS gt; PpCIS gt; PpiPrαMeS gt; PpBrS gt; PpOMeS gt; PαMeS. In the case of PS where degradations were also carried out at -20°C, lowering of the temperature increased the weight fraction of polymer degraded as well as S. Based on the viscosity and GPC data, it is concluded that the ultrasonic solution degradation of PS does not lead to branched polymers.     

Study of the Lipophilic Character of Xanthine and Adenosine Derivatives: II. Relationships Between Log K', RM and Log P Values

Abstract

The log k' values of a series of xanthine and adenosine derivatives were measured by means of a reversed-phase HPLC. The HPLC data were shown to be well correlated with previously reported R_M and R_MC18 values. The equations describing the relationships log k'/R_M and log k'/R_MC18 allowed the calculation of the log k' values of some compounds, which were not tested in the HPLC system. Since the relationship log k'/log P is very close to the previously described relationships R_M/log P and R_MC18/log P one can conclude that reversed-phase TLC and HPLC are very similar in describing the lipophilicity of the compounds.     

EINIGE NEUE THIOPHOSPHINSÄUREAMIDE R2P(S)NHR': SYNTHESE UND KERNRESONANZSPEKTROSKOPISCHE UNTERSUCHUNGEN

Abstract

P.P-Dialkylthiophosphinsäureamide R₂P(S)NHR' (R=Me, 'Pr, 'Bu; R'=Me, Et, ⁱPr. ^cHex. ^tBu. Ph. etc.) wurden erhalten durch Umsetzung von R₂PNHR' mit Schwefel oder durch Reaktion von Me₂P(S)CI mit primaren Aminen. Ihre ³¹P- und ¹³C-NMR-Spektren werden diskutiert. Insbesondere die Di-t-butylthiophosphinsäureamide sind auszilg;ergewöhnlich stabil gegen Hydrolyse und Luftsauerstoff. P,P-Dialkylthiophosphinic acid amides R₂P(S)NHR' (R=Me. ⁱPr. ^tBu; R'=Me, Et, ⁱPr, ^cHex. ^tBu, Ph. etc.) have been obtained by reaction of the corresponding aminophosphines with sulfur or by reaction of dimethylthiophosphorylhalides with primary amines. Their ³¹P- and ¹³C-NMR spectra are discussed. The di-t-butylthiophosphinic compounds proved to be remarkably stable against moisture and oxygen.     

Comparison of Methods for Determination of the RM Values of Substances in Thin - Layer Chromatography by Using Binary Mobile Phase

Abstract

Methods of calculating the function R_M= f(?₁) of some aromatic substances from the data of experimental and theoretically calculated parameters have been compared. It has been shown that there is a possibility to calculate this function with high accuracy on the basis of the measured partition coefficients of the substances chromatographed in partition systems consisting of components of the mobile phase as well as parameters obtained theoretically. Thus obtained results were also compared with the functions R_{M 1.2} = f (?₁) obtained experimentally and a high agreement was reached. This in turn contributes to optimization of systems of thin-layer chromatography.     

Well‐defined amphiphilic polymethylene‐b‐poly(acrylic acid) diblock copolymers: New synthetic strategy and their self‐assembly

Well‐defined amphiphilic polymethylene‐b‐poly (acrylicacid) diblock copolymers have been synthesized via a new strategy combining polyhomologation and atom transfer radical polymerization (ATRP). Hydroxyl‐terminated polymethylenes (PM‐OH) with different molecular weights and narrow molecular weight distribution are obtained through the polyhomologation of dimethylsulfoxonium methylides following quantitative oxidation via trimethylamine‐N‐oxide dihydrate. Subsequently, polymethylene‐based macroinitiators (PM‐MIs M_n = 1,300 g mol^?1 [M_w/M_n = 1.11] and M_n = 3,300 g mol^?1 [M_w/M_n = 1.04]) are synthesized by transformation of terminal hydroxyl group of PM‐OH to α‐haloester in ～100% conversion. ATRPs of tert‐butyl acrylate (t‐BuA) are then carried out using PM‐MIs as initiator to construct PM‐b‐P(t‐BuA) diblock copolymers with controllable molecular weight (M_n = 8,800–15,800 g mol^?1 M_w/M_n = 1.04–1.09) and different weight ratio of PM/P(t‐BuA) segment (1:1.7–1:11.2). The amphiphilic PM‐b‐PAA diblock copolymers are finally prepared by hydrolysis of PM‐b‐P(t‐BuA) copolymers and their self‐assembly behavior in water is preliminarily investigated via the determination of critical micelle concentrations, dynamic light scattering, and transmission electron microscope (TEM). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Salicylaldiminato-based cobalt(III)-, iron(III)-, and chromium(III)/methyl aluminoxane catalyst systems for polymerization of <Emphasis Type="Italic">t</Emphasis>-butyl acrylate

A new series of penta-coordinated Co(III)-, Fe(III)-, and Cr(III)- complexes (6–10) bearing N-salicylidineisopropylaniline and sodium N-(4-sulfonitsalicylidineisopropyl-aniline) ligands has been synthesized and utilized, after activation with methyl aluminoxane, as catalysts for the polymerization of tert-butylacrylate (t-BA). High molar mass P(t-BA) polymers with very low molecular weight distributions were produced (M _w/M _n = 1.06–1.09). Cobalt- and chromium-based precatalysts showed higher activity towards the polymerization reaction than those of the iron complexes. The presence of sulfonated groups on the para position of the aryl group in the backbone of the ligand decreases the catalytic activity of the complexes. The ortho alkyl substituents on the aryl groups of the ligand have a favorable influence on the polymerization activity compared to the alkyl-free analogue (11).     

Facile preparation of a three-coordinate copper(I) complex: Steric hindrance,supramolecular structure,optical property and TD-DFT study

The solution reaction of Cu(CH₃CN)₄(PF₆) with a NN ligand 2-(2′-quinolyl)benzimidazole and a sterically bulky P ligand tris(2-methylphenyl)phosphine facilely yielded the three-coordinate copper(I) complex [Cu(2-QBI)(o-Tol₃P)](PF₆) (1). The complex has been characterized by single-crystal X-ray diffraction, Fourier Transform infrared spectroscopy and elemental analysis, UV–Vis (ultraviolet–visible) and photoluminescent spectroscopy studies. Time-dependent density functional theory has been used for calculating the electronic origin of the low-lying excited states, which were unexpectedly assigned mainly as a ligand-to-ligand or an intra-ligand charge transfer state instead of the metal-to-ligand charge transfer transition. Interestingly, 1 exhibits a concentration-dependent absorption in solution. This absorption behavior is interpreted as some excimer's formation based on the study of supramolecular structure, spectroscopy and calculations.     

Evaluation of Dead Time Calculation in Reversed-Phase Liquid Chromatography Using a Multiparametric Mathematical Method

In reversed phase liquid chromatography (RP-HPLC), the validity of a multiparametric non-linear least-squares regression iterative method for the determination of the column dead time t_M and the regression parameter (slope b), based on the use of alkan-2-ones, alkyl aryl ketones, and 1-nitroalkanes has been evaluated. The determination of t_M and b has been extensively studied for two mobile phase systems acetonitrile-water and methanol-water on seven octadecyl-C₁₈ and one octyl C₈ analytical columns. The calculated t_M and b values were compared with those obtained by Guardino's and Grobler's methods. The influence exerted thereon by the nature of the homologous series, the mobile phase composition, and the packing materials were investigated.     

Preparation and Surface Properties of Fluorine‐Containing Diblock Copolymers PLMA‐Block‐PFAEA

A series of fluorine‐containing diblock copolymers based on lauryl methacrylate and 1H,1H,2H,2H‐perfluoroalkyl acrylate have been prepared by atom transfer radical polymerization (ATRP). The preparation process of PLMA‐Br macroinitiators was controlled within a reasonable time corresponding to the ln [M₀]/[M_t]～time plot of the reaction. FTIR, ¹H‐NMR, GPC and fluorine‐element analysis (FEA) were used to characterize the synthesized block copolymers. The solid surface activity of these polymers was demonstrated by contact angle measurement. The polymer films prepared by block copolymers with more than three fluorinated units showed low dispersion force contributions to the surface energy indicating the presence of the fluorinated block at the surface. The surface activity in solutions was measured by drop‐weight method. Ii is interesting to find, when the fluorine weight percentage is controlled constant, that PLMA‐b‐PFAEA with larger molecular size is more prominent in exploiting the fluorinated structure to reduce the surface tension of solutions. The block copolymer's ability in reducing surface tension of solutions also depends on the type of solvent.     

Diagnosis of magnetoresponsive aromatic and antiaromatic zones in three‐membered rings of d‐ and f‐block elements

Magnetoresponsive three‐membered rings of d‐ and f‐block elements have been thoroughly investigated with the help of electronic structure calculation methods. The magnetic response of the clusters was evaluated by the Nucleus Independent Chemical Shifts (NICS)_zz‐scan curves, which in conjunction with symmetry‐based selection rules for the most significant translationally and rotationally allowed transitions helped rationalize and predict the orbital‐type of aromaticity/antiaromaticity of the clusters. The magnetoresponsive early (Groups 3, 4, and 5) transition metal M₃ rings exhibit successive aromatic and antiaromatic zones separated by a nodal plane. The magnetoresponsive late (Groups 11 and 12) transition metal M₃ rings exhibit long‐range aromatic zone with the NICS_zz(R) values decaying rapidly and monotonically with respect to R. The magnetic response of Group 10 transition metal M₃ rings is similar to that of the early transition metal M₃ rings, but it is long‐range antiaromatic only for the [c‐Ni₃] cluster. The NICS_zz‐scan curve of the [(H_tLa)₃(μ₂‐H)₆] cluster is indicative of weak pure σ‐aromaticity due to the induced diatropic ring current from the translationally allowed a → e′ and e′ → a transitions. The aromatic–antiaromatic behavior of the [(H_tCe)₃(μ₂‐H)₆]⁺ and [(H_tTm)₃(μ₂‐H)₆]²⁻ clusters is similar to that of the early d‐block elements. The magnetic response of [(H_tYb)₃(μ₂‐H)₆]³⁻ is similar to that of [c‐Hg₃]²⁻. The [(H_tLu)₃(μ₂‐H)₆] cluster can be considered as a doubly (σ + π) aromatic system, with the σ‐aromatic component being much stronger than the π‐aromatic one. Finally, the [(X_tRe)₃(μ₂‐X)₆] and [(X_tRu)₃(μ₂‐X)₆]⁺ (X = Cl, Br, I) clusters exhibit significant aromatic character with the greatest contribution to the induced diatropic ring currents coming from π‐type transitions. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010     

Ionothermal syntheses and characterization of 2-D coordination polymers with 4-(1H-imidazol-1-yl) benzoic acid

4-(1H-imidazol-1-yl) benzoic acid and its coordination polymers [M(IBA)Cl] _n (M?=?Zn (1) and Co (2)) have been synthesized. Compounds 1 and 2 were obtained under ionothermal conditions and possess a 2-D laminar [M(IBA)] _n layer based on M₂(CO₂)₂ building blocks with coordinated chloride completing tetrahedral coordination of the metal. Compound 1 exhibits two photoluminescence emission peaks at 410 and 510?nm. The low-energy emission can be attributed to ligand-centered transition and the high-energy band can be assigned to ligand-to-metal charge transfer between the aromatic systems of the organic ligands and the 4s orbitals of Zn(II). The role of the ionic liquid in ionothermal synthesis and crystallization of 1 and 2 are briefly discussed.     

Volumetric behavior and micelle formation of aqueous surfactant mixtures

A thermodynamic treatment of the volumetric behavior of surfactant mixtures in water have been developed on the basis of the thermodynamic treatment of mixed micelle by Motomura et al. Densities of aqueous solutions of mixtures of decyltrimethylammonium bromide (DeTAB) and dodecyltrimethylammonium bromide (DTAB) have been measured as a function of total molality at constant compositions. The apparent molar volumes of the mixtures have been derived from the density data and the mean partial molar volume of monomeric surfactant mixture V _t ^w , the molar volume of mixed micelle V^M/N _t ^M , the voluem of formation of mixed micelle _W ^M V, and the composition of surfactant in the mixed micelle have been evaluated. The V _t ^W , V^M/N _t ^M , and _W ^M V have been observed to depend on the composition. The linear dependence of V _t ^W and V^M/N _t ^M on the composition indicates that the mixing of DeTAB and DTAB is ideal both in the monomeric and micellar states. This has been confirmed further by the shape of the critical micelle concentration vs. composition curves.     

MIXED ANHYDRIDES OF DIALKYLPHOSPHINOUS ACIDS AND DIALKYL HYDROGEN PHOSPHITES,AND THE ISOMERIC MONOXIDES

Abstract

The three isomers possible for oxidized 1,1-dialkyl-2,2-dialkoxydiphosphines, R₂(O)P–P(OR')₂ 1, R₂P–O–P(OR')₂ 2, and R₂P–P(O)(OR')₂ 3, have been synthesized. Irreversible transformations of 1 to 2 and 2 to 3 have been found and the rearrangement patterns, the role of electrophilic and nucleophilic catalysts are discussed. The fact that 3 is more stable than 1 is attributed to higher donor activity of the ligands attached to the four-coordinate phosphorus in 3. Acid chlorides have been shown to attack the phosphorus atom of ambident anions of trivalent phosphorus acids (the products are 1 and 3) whereas the acids proper react with the acid halides at the oxygen atom, to give 2.     

Thermal stability of some new complexes bearing ligands with polymerizable groups

A series of new complexes with mixed ligands of the type M(4,4’-dipy)(C₃H₃O₂)₂(H₂O)_y ((1) M=Mn, y=2; (2) M=Ni, y=2; 4,4’-dipy: 4,4’-dipyridyl and C₃H₃O₂ is acrylate anion) and respectively M₂(4,4’-dipy)(C₃H₃O₂)₄(H₂O)_y ((3) M=Cu, y=0; (4) M=Zn, y=1). The modification evidenced in IR spectra was correlated with the presence of acrylate ion as unidentate in the case of complex (1) and as bidentate for others complexes. The electronic reflectance spectra showed the d–d transition for complex (1) and (2) characteristic for the octahedral surrounding while the spectrum for complex (3) have the characteristic pattern for square-pyramidal stereochemistry. The thermal behaviour steps were investigated. The thermal transformations are complex processes according to TG and DTG curves including dehydration, acrylate ion oxidative degradation and thermolysis process of aromatic amine. The final products of decomposition are the most stable metal oxides.     

Ionic solvation in water + co-solvent mixtures. Part 8. Total free energies of transfer and free energies of transfer with the “neutral” component removed of single ions from water into water + acetone

The acid dissociation constants of a wide range of acids in water+acetone mixtures have been combined with values for the free energy of transfer of the proton. ΔG⁰_t(H⁺ to calculate values for the free energy of transfer of ions which derive only from the charge on the ion. ΔG⁰_t(i)_c. As the values of ΔG⁰_t(H⁺) have been revised, revised values for the total free energies of transfer of cations and anions, ΔG⁰_t(M⁺) and ΔG^o_t(X^-), are given. New data for ΔG^o_t(MX_n) is also split into values for ΔG⁰_t(Mⁿ⁺) (where n=1 and 2) and ΔG⁰_t(X^?). These free energies of transfer, both total and those deriving from the charge alone, are compared with similar free energies in other mixtures water+co-solvent. Values for ΔG^o_t(i)_c do not conform to a Born-type relationship and show the importance of structural effects in the solvent even when only the transfer of the charge is involved.     

Free energies and entropies of transfer from water to methanol of cations complexed by 18-crown-6

Free energies and entropies of transfer from water to methanol have been obtained for [M⁺18C6] complexes, where M⁺ = Na⁺, K⁺, Rb⁺, Cs⁺, and Ag⁺. The variation of ΔG_t° and ΔS_t° with the central metal cation is smaller than with the [M⁺222] complexes and it is concluded that 18-crown-6 shields the metal cation from the solvent more effectively than crystal structure determinations would suggest.     

Synthesis of Polyfunctional Drimanes from Drim-7,9(11)-diene and Drim-8-en-7-one

A series of 15 new polyfunctional drimanic compounds have been obtained by synthesis via dye-sensitized photooxygenation, bromination with N-bromosuccinimide, and electrochemical transformation of drim-7,9(11)-diene 1 and drim-8-en-7-one 2. Three alternative syntheses of 12-acetoxy-drim-7,9(11)-diene 8 and two of 11-bromo-drim-8(9)-en-7-one 10 have been accomplished. For the first time a drimanic compound 12 with an aromatic ring B has been synthesized and the experimental conditions for the selective bromination at C₁₁ and C₁₂ methyl groups of drim-8-en-7-one 2 have been optimized. The synthesized compounds are suitable intermediates for the preparation of natural drimane-type compounds and some of them have shown good antimicrobial and antifungal activities.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource: Full experimental and spectral details.]     

Analysis of Polycyclic Aromatics

Abstract

Polycyclic aromatic hydrocarbons (PAH), among them carcinogenic compounds, have been found to be widely distributed in the human environment. The formation of PAH in processes relevant to environmental pollution will be described (pyrolysis or incomplete combustion of aliphatic and aromatic material, formation in higher plants). The application of the following methods to the analysis of PAH mixtures will be discussed: gas chromatography (capillary columns, use. of liquid crystals and inorganic salts such as LiCl or Cacl₂, as stationary phases in packed columns, selective detectors); luminescence spectroscopy (use of phosphorescence in paper and thin-layer chromatography, Shpol'skii spectra, quenchofluorimetry; mass spectroscopy.     

Synthesis of poly(tert‐butyl methacrylate)‐graft‐poly(dimethylsiloxane) graft copolymers via reversible addition‐fragmentation chain transfer polymerization

Well‐defined poly(tert‐butyl methacrylate)‐graft‐poly (dimethylsiloxane) (PtBuMA‐g‐PDMS) graft copolymers were synthesized via reversible addition‐fragmentation chain transfer (RAFT) copolymerization of methacryloyl‐terminated poly (dimethylsiloxane) (PDMS‐MA) with tert‐butyl methacrylate (tBuMA) in ethyl acetate, using 2,2′‐azobis(isobutyronitrile) (AIBN) as the initiator and 2‐cyanoprop‐2‐yl dithiobenzoate as the RAFT agent. The RAFT statistical copolymerization of PDMS‐MA with tBuMA is shown to be azeotropic and the obtained PtBuMA‐g‐PDMS graft copolymers have homogeneously distributed branches because of the similar reactivity of monomers (r_tBuMA ≈ r_PDMS‐MA ≈ 1). By the RAFT block copolymerization of PDMS‐MA with tBuMA, moreover, narrow molecular weight distribution (M_w/M_n < 1.3) PtBuMA‐g‐PDMS graft copolymers with gradient or blocky branch spacing were synthesized. The graft copolymers exhibit the glass transitions corresponding to the PDMS and PtBuMA phase, respectively. However, the arrangement of monomer units in copolymer chains and the length of PtBuMA moieties have important effects on the thermal behavior of PtBuMA‐g‐PDMS graft copolymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Investigation of the effect of reaction conditions on the synthesis of multiarm-star polyisobutylene-polystyrene block copolymers

New multi-arm star block copolymers comprising of rubbery polyisobutylene (PIB) midsegment and glassy polystyrene (PS) end blocks have been synthesized by carbocationic polymerization using a new multifunctional initiator, hexaepoxy squalene (HES), with TiCl₄ coinitiator, di-t-butylpyridine (DtBP) as a proton trap and N,N-dimethylacetamide (DMA) as an electron pair donor in methylcyclohexane (MeCHx)/methyl chloride (MeCl) solvent mixtures at −80 °C. It was found that reaction conditions, such as solvent composition, HES/isobutylene (IB) ratio and TiCl₄ concentration, have profound influence on initiator efficiency and functionality. Living conditions were achieved in the presence of DMA in MeCHx/MeCl 60/40 v/v, while in the absence of DMA, the M_n-conversion plot showed a considerable intercept. Depending on the reaction conditions, the PIB midblocks had 3-10 arms. Reaction rates increased with increasing solvent polarity and TiCl₄ concentration. Living narrow molecular weight distribution PIBs (M_w/M_n=1.1-1.2) were reacted with styrene (St) solution containing DtBP and DMA to yield multiarm-star PIB-PS block copolymers. Blocking was evidenced by SEC analysis and copolymers with 8.9-28.6 wt.% PS, M_n∼164,000-609,000 g/mol and M_w/M_n=1.32-1.88 were successfully synthesized.