Synthesis of Poly(arylene vinylene)s with Different End Groups by Combining Acyclic Diene Metathesis Polymerization with Wittig‐type Couplings

A series of end‐functionalized poly(9,9′‐di‐n ‐octylfluorene vinylene)s (EF‐PFVs) with different end groups were obtained by 1) synthesizing EF‐PFV with vinyl end groups by acyclic diene metathesis (ADMET) polymerization with a molybdenum catalyst and termination with an aldehyde and 2) subsequent olefin metathesis of the vinyl group with the molybdenum catalyst followed by Wittig‐type coupling with another aldehyde. The exclusive formation of EF‐PFVs containing a vinyl end group by the ADMET polymerization was confirmed by grafting PEG, and by the synthesis of amphiphilic triblock copolymers by combining atom transfer radical polymerization from the PFV chain end with PEG grafting through a click reaction. Various EF‐PFVs with different end groups, such as C₆F₅, pyridyl, ferrocenyl, and terthiophene, have thus been prepared. Their fluorescence spectra (e.g., intensities, emission wavelengths) were influenced by the end groups and the length of the conjugation.     

Preparation of High‐capacity,Monodisperse Polymeric Weak Cation Exchange Packings Using Surface‐initiated Atom Transfer Radical Polymerization and Its Chromatographic Properties

A novel stationary phase for weak cation exchange (WCX) chromatography was prepared by "grafting from" strategy. Surface initiated atom transfer radical polymerization (ATRP) of acrylic acid (AA) was conducted in toluene medium, starting from the macromolecule initiators of poly(4‐vinylbenzyl chloride‐co‐divinylbenzene) (P_CMS/DVB) beads. The amounts of poly(acrylic acid) grafted chains with different ATRP formulations were calculated based on the elemental analyses. The poly(acrylic acid) grafted beads obtained with different ATRP formulations were tried as chromatographic packings in the separation of proteins by ion‐exchange chromatography. The effect of the poly(acrylic acid) grafted chain lengths on P_CMS/DVB beads for the separation of proteins was investigated in details. Simultaneously, characterization of the column was investigated as ion chromatographic stationary phase for the separation of inorganic cations. The results show that poly(acrylic acid) grafted columns had excellent performance for separation of proteins and inorganic cations. The highest of the dynamic capacity of the column was 35.55 mg/mL. The columns were provided with high column efficiency.     

Drug–Membrane Interaction on Immobilized Liposome Chromatography Compared to Immobilized Artificial Membrane (IAM), Liposome/Water,and Octan‐1‐ol/Water Systems

The objective of this study was to investigate drug–membrane interaction by immobilized liposome chromatography (ILC; expressed as lipophilicity index log K_s) and the comparison with lipophilicity indices obtained by liposome/H₂O, octan‐1‐ol/H₂O, and immobilized artificial membrane (IAM) systems. A set of structurally diverse monofunctional compounds and drugs (nonsteroidal anti‐inflammatory drugs and β‐blockers) were selected in this study. This set of solutes consists of basic or acidic functionalities which are positively or negatively charged at physiological pH 7.4. No correlation was found between log K_s from ILC and lipophilicity indices from any of the other membrane model systems for the whole set of compounds. For structurally related compounds, significant correlations could be established between log K_s from ILC and lipophilicity indices from IAM chromatography and octan‐1‐ol/H₂O. However, ILC and liposome/H₂O systems only yield parallel partitioning information for structurally related large molecules. For hydrophilic compounds, the balance between electrostatic and hydrophobic interactions dominating drug partitioning is different in these two systems.     

Preparation of macroporous functionalized polymer beads by a multistep polymerization and their application in zirconocene catalysts for ethylene polymerization

Macroporous functionalized polymer beads of poly(4‐vinylpyridine‐co‐1,4‐divinylbenzene) [P(VPy‐co‐DVB)] were prepared by a multistep polymerization, including a polystyrene (PS) shape template by emulsifier‐free emulsion polymerization, linear PS seeds by staged template suspension polymerization, and macroporous functionalized polymer beads of P(VPy‐co‐DVB) by multistep seeded polymerization. The polymer beads, having a cellular texture, were made of many small, spherical particles. The bead size was 10–50 μm, and the pore size was 0.1–1.5 μm. The polymer beads were used as supports for zirconocene catalysts in ethylene polymerization. They were very different from traditional polymer supports. The polymer beads could be exfoliated to yield many spherical particles dispersed in the resulting polyethylene particles during ethylene polymerization. The influence of the polymer beads on the catalytic behavior of the supported catalyst and morphology of the resulting polyethylene was investigated. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 873–880, 2003     

Enantioselective Synthesis and Physicochemical Properties of Libraries of 3‐Amino‐ and 3‐Amidofluoropiperidines

The enantioselective syntheses of 3‐amino‐5‐fluoropiperidines and 3‐amino‐5,5‐difluoropiperidines were developed using the ring enlargement of prolinols to access libraries of 3‐amino‐ and 3‐amidofluoropiperidines. The study of the physicochemical properties revealed that fluorine atom(s) decrease(s) the pK_a and modulate(s) the lipophilicity of 3‐aminopiperidines. The relative stereochemistry of the fluorine atoms with the amino groups at C3 on the piperidine core has a small effect on the pK_a due to conformationnal modifications induced by fluorine atom(s). In the protonated forms, the C?F bond is in an axial position due to a dipole–dipole interaction between the N?H⁺ and C?F bonds. Predictions of the physicochemical properties using common software appeared to be limited to determine correct values of pK_a and/or differences of pK_a between cis‐ and trans‐3‐amino‐5‐fluoropiperidines.     

中性芳香族溶质在脂质体电动色谱中的热力学分配行为

脂质体电动色谱是一种理想的评价药物与生物膜相互作用的模型. 在288～323 K范围内测定了中性芳香族溶质在脂质体电动色谱中的分配系数, 通过三项式拟合Van't Hoff图获得了一系列的热力学参数, 研究了溶质在脂质体电动色谱中的热力学分配行为. 结果表明, 分配系数随体系温度的升高和苯环所带亚甲基数目的增加而增大. 从288到323 K, ΔH＞0, －TΔS＜0, ΔG＜0, 溶质在脂质体电动色谱中的分配过程为熵驱动过程. 从288到298 K, 脂质体电动色谱分配系统的ΔC_p为负值, 其表现行为与经典疏水作用一致. 从303到323 K, 脂质体电动色谱分配系统的ΔC_p为正值, 其表现行为与经典疏水作用不完全吻合. ΔH和ΔS呈线性关系, 该分配系统存在焓熵补偿.     

Kinetics and mechanism of the cationic polymerization of trioxane. I. Crystallization during polymerization

Cationic polymerizations of trioxane in 1,2‐ethylene dichloride and benzene were heterogeneous and reversible. Phase separation accompanying with crystallization occurred during the polymerization. Three morphological changes were found in the course of the polymerization as were investigated by dilatometry and precipitation method. Based on the findings of morphological changes and three reversible processes for the polymerization, a rate equation was proposed to describe the polymerization. The proposed rate equation was fairly good in describing the experimental data, and kinetics constants including K_p, K_d, K_p′, K_d′, M, M, and K_dis/K_cr for the polymerization at 30, 40, and 50°C in 1,2‐ethylene dichloride and benzene were obtained. Factors that affected the kinetics constants were discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 483–492, 1999     

Ring‐opening metathesis polymerization‐derived,lectin‐functionalized monolithic supports for affinity separation of glycoproteins

Lectin‐functionalized monolithic columns were prepared within polyether ether ketone (PEEK) columns (150 × 4.6 mm id) via transition metal‐catalyzed ring‐opening metathesis polymerization of norborn‐2‐ene (NBE) and trimethylolpropane‐tris(5‐norbornene‐2‐carboxylate) (CL) using the first‐generation Grubbs initiator RuCl₂(PCy₃)₂(CHPh) (1, Cy = cyclohexyl) in the presence of a macro‐ and microporogen, i.e. of 2‐propanol and toluene. Postsynthesis functionalization was accomplished via in situ grafting of 2,5‐dioxopyrrolidin‐1‐yl‐bicyclo[2.2.1]hept‐5‐ene‐2‐carboxylate to the surface of the monoliths followed by reaction with α,ω‐diamino‐poly(ethyleneglycol). The pore structure of the poly(ethyleneglycol)‐ derivatized monoliths was investigated by electron microscopy and inverse‐size exclusion chromatography, respectively. The amino‐poly(ethyleneglycol) functionalized monolithic columns were then successfully used for the immobilization of lectin from Lens culinaris hemagglutinin. The thus prepared lectin‐functionalized monoliths were applied to the affinity chromatography‐based purification of glucose oxidase. The binding capacity of Lens culinaris hemagglutinin‐immobilized monolithic column for glucose oxidase was found to be 2.2 mg / column.     

Phenomenon of dual‐ and single‐retention behaviors of solutes and its validation by computational simulation in linear programmed temperature gas chromatography

The current theory of programmed temperature gas chromatography considers that solutes are focused by the stationary phase at the column head completely and does not explicitly recognize the different effects of initial temperature (T_o) and heating rate (r_T) on the retention time or temperature of a homologue series. In the present study, n‐alkanes, 1‐alkenes, 1‐alkyl alcohols, alkyl benzenes, and fatty acid methyl esters standards were used as model chemicals and were separated on two nonpolar columns, one moderately polar column and one polar column. Effects of T_o and r_T on the retention of nonstationary phase focusing solutes can be explicitly described with isothermal and cubic equation models, respectively. When the solutes were in the stationary phase focusing status, the single‐retention behavior of solutes was observed. It is simple, dependent upon r_T only and can be well described by the cubic equation model that was visualized through four sequential slope analyses. These observed dual‐ and single‐retention behaviors of solutes were validated by various experimental data, physical properties, and computational simulation.     

Dicationic imidazolium ionic liquid modified silica as a novel reversed‐phase/anion‐exchange mixed‐mode stationary phase for high‐performance liquid chromatography

A dicationic imidazolium ionic liquid modified silica stationary phase was prepared and evaluated by reversed‐phase/anion‐exchange mixed‐mode chromatography. Model compounds (polycyclic aromatic hydrocarbons and anilines) were separated well on the column by reversed‐phase chromatography; inorganic anions (bromate, bromide, nitrate, iodide, and thiocyanate), and organic anions (p‐aminobenzoic acid, p‐anilinesulfonic acid, sodium benzoate, pathalic acid, and salicylic acid) were also separated individually by anion‐exchange chromatography. Based on the multiple sites of the stationary phase, the column could separate 14 solutes containing the above series of analytes in one run. The dicationic imidazolium ionic liquid modified silica can interact with hydrophobic analytes by the hydrophobic C₆ chain; it can enhance selectivity to aromatic compounds by imidazolium groups; and it also provided anion‐exchange and electrostatic interactions with ionic solutes. Compared with a monocationic ionic liquid functionalized stationary phase, the new stationary phase represented enhanced selectivity owing to more interaction sites.     

Incorporation of metal‐organic framework amino‐modified MIL‐101 into glycidyl methacrylate monoliths for nano LC separation

Metal‐organic frameworks consisting of amino‐modified MIL‐101(M: Cr, Al, and Fe) crystals have been synthesized and subsequently incorporated to glycidyl methacrylate monoliths to develop novel stationary phases for nano‐liquid chromatography. Two incorporation approaches of these materials in monoliths were explored. The metal‐organic framework materials were firstly attached to the pore surface through reaction of epoxy groups present in the parent glycidyl methacrylate‐based monolith. Alternatively, NH₂‐MIL‐101(M) were admixed in the polymerization mixture. Using short time UV‐initiated polymerization, monolithic beds with homogenously dispersed metal‐organic frameworks were obtained. The chromatographic performance of embedded UV‐initiated composites was demonstrated with separations of polycyclic aromatic hydrocarbons and non‐steroidal anti‐inflammatory drugs as test solutes. In particular, the incorporation of the NH₂‐MIL‐101(Al) into the organic polymer monoliths led to an increase in the retention of all the analytes compared to the parent monolith. The hybrid monolithic columns also exhibited satisfactory run‐to‐run and column‐to‐column reproducibility.     

Graft polymerization of vinyl monomers inside macroporous polyacrylamide gel,cryogel, in aqueous and aqueous‐organic media initiated by diperiodatocuprate(III) complexes

Graft polymerization initiated by diperiodatocuprate(III) complex (Cu(III)) initiator was found to be an effective and convenient method for graft polymerization of vinyl monomers onto macroporous polyacrylamide gels, the so‐called cryogels (pAAm‐cryogels). The effect of time, temperature, monomer and initiator concentration during the graft polymerization in aqueous and aqueous‐organic media was studied. The graft polymerization of water‐soluble monomers as [2‐(methacryloyloxy)ethyl]‐trimethylammonium chloride, 2‐hydroxyethyl methacrylate, N‐isopropylacrylamide, and N,N‐dimethylacrylamide proceeds with higher grafting yield in aqueous medium, as compared with that in aqueous‐organic media. Graft polymerization in aqueous‐organic media such as water–DMSO solutions allows grafting of water‐insoluble monomers such as glycidyl methacrylate and N‐tert‐butylacrylamide with high grafting degrees of 100 and 410%, respectively. It was found that the deposition of initiator on the pore surface of cryogels promoted graft polymerization by facilitating the formation of the redox couple Cu(III)‐acrylamide group. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1952–1963, 2006     

Nucleophilicities of Para‐Substituted Phenoxide Ions in Water and Correlation Analysis

Second‐order rate constants for the reactions of 2‐aryl‐4,6‐dinitrobenzotriazole 1‐oxides 1a‐d with some 4‐X‐substituted phenoxide ions 2a‐d (X = OCH₃, H, Cl, and CN) have been measured in aqueous solution at 20°C. The pK_a values for the σ‐complexation processes of a series of benzotriazole 1a‐d measured in water have been used to determine their electrophilicity parameters E according to the correlation E = –3.20 – 0.662 pK_a (F. Terrier, S. Lakhdar, T. Boubaker, and R. Goumont, J Org Chem, 2005 , 70, 6242–6253). For these reactions, plots of log k versus the electrophilicity parameters E of the benzotriazoles 1a‐d were linear, allowing to derive the nucleophilicity parameters N and s for phenoxide ions as defined by the Mayr equation log k₁ (20°C) = s (E + N) (H. Mayr, M. Patz. Angew Chem, Int Ed Engl 1994 , 33, 938–957). The N values are found to cover a range of nucleophilicity from 6.85 to 10.22, going from 4‐cyanophenoxide 2d for the least reactive ion to 4‐methoxyphenoxide 2a for the most reactive nucleophile. Good linear correlations were found between the nucleophilicity parameters N of phenoxide ions 2a‐d and the pK_a values of their conjugate acids (N = –3.05 + 1.25 pK_a) and the constants of the substituents X (N = 9.21 – 2.51).     

Living radical graft polymerization of methyl methacrylate to polyethylene film with typical and reverse atom transfer radical polymerization

Nickel‐mediated atom transfer radical polymerization (ATRP) and iron‐mediated reverse ATRP were applied to the living radical graft polymerization of methyl methacrylate onto solid high‐density polyethylene (HDPE) films modified with 2,2,2‐tribromoethanol and benzophenone, respectively. The number‐average molecular weight (M_n) of the free poly(methyl methacrylate) (PMMA) produced simultaneously during grafting grew with the monomer conversion. The weight‐average molecular weight/number‐average molecular weight ratio (M_w/M_n) was small (<1.4), indicating a controlled polymerization. The grafting ratio showed a linear relation with M_n of the free PMMA for both reaction systems. With the same characteristics assumed for both free and graft PMMA, the grafting was controlled, and the increase in grafting ratio was ascribed to the growing chain length of the graft PMMA. In fact, M_n and M_w/M_n of the grafted PMMA chains cleaved from the polyethylene substrate were only slightly larger than those of the free PMMA chains, and this was confirmed in the system of nickel‐mediated ATRP. An appropriate period of UV preirradiation controlled the amount of initiation groups introduced to the HDPE film modified with benzophenone. The grafting ratio increased linearly with the preirradiation time. The graft polymerizations for both reaction systems proceeded in a controlled fashion. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3350–3359, 2002     

Determination of weak (2.0–2.5) dissociation constants of non-UV absorbing solutes by capillary electrophoresis

Summary Capillary electrophoresis (CE) has proved to be a fast and convenient method for the determination of the dissociation constants of non-UV absorbing solutes in the acidic pK _A range (2.0–2.5). The electroosmotic flow was reversed by washing the capillary with 0.2% polybren aqueous solution. A series of background electrolytes was prepared with phenylphosphonic acid (pK _A=1.29) and β-alanine (pK _A=3.55) with the same ionic strength and a high buffer capacity in order to improve the repeatability (0.1–0.2 %) of the electrophoretic mobility and to determine the values of pK _A accurately. This procedure was applied to the determination of the dissociation constants of several alkyl-alkylphosphonic acids whose pK _A values have not yet been published in the literature. In this work, their dissociation constants have been found to vary between 1.91 and 2.34 for alkyl-methylphosphonic acids and between 2.10 and 2.38 for alkyl-ethylphosphonic acids.     

Role of grafting in the emulsion polymerization of vinyl acetate with poly(vinyl alcohol) as an emulsifier. I. Effect of the degree of blockiness on the kinetics and mechanism of grafting

The role of grafting in particle nucleation during the emulsion polymerization of vinyl acetate with partially hydrolyzed poly(vinyl alcohol) (PVA) as an emulsifier and potassium persulfate as an initiator was investigated. The polymerizations were carried out in batch with a low solids (10%) recipe. An automated reaction calorimeter (Mettler RC1) was used for the direct monitoring of the kinetics of emulsion polymerizations with three medium molecular weight PVAs differing in their degrees of blockiness (Poval 217EE > 217E > 217). Smith–Ewart case 1 kinetics (average number of free radicals per particle < 0.5) were followed in all cases, and no constant rate in interval II was observed. Contrary to what was expected, a nonlinear relationship was observed between the rate of polymerization (R_p) and the number of particles (N_p). At R_{p max,} N_p (217E) > N_p (217EE) > N_p (217), and the final N_p was independent of the degree of blockiness of PVA. The particle size distributions were broad (particle diameter = 20–100 nm) and bimodal. On the basis of these data, we concluded that particle nucleation was continuous and was accompanied by extensive limited aggregation during the particle growth stages. The evolution of the amounts of grafted PVA and poly(vinyl acetate) (PVAc) were determined in polymerizations employing the two PVAs differing the most in blockiness (Poval 217EE and 217). The grafted PVAc followed similar profiles, increasing with conversion, particularly near the end of the two reactions. The amounts of grafted PVAc were about the same in the final latexes (37–39%). In contrast, the grafting of PVA was nearly complete by the time monomer droplets had disappeared in each reaction (25% conversion). However, the extent of grafting differed significantly, with the blockier PVA having about one‐third the grafting of the more random PVA (～10% vs ～30%). In these low solids recipes, grafting appeared to be primarily a solution event, occurring predominantly in the aqueous phase and not at the particle/water interface, as was previously speculated. The PVAc grafts grew until the molecules became water‐insoluble and precipitated, forming polymer particles. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3633–3654, 2001     

Potentiometric and Voltammetric Study of 6‐Benzylaminopurine and Its Derivatives

The protonation‐deprotonation equilibrium of 6‐benzylaminopurine (6‐BAP) and its derivatives was studied by potentiometry and voltammetry. The effect of Cl‐ or OCH₃‐group in position 2′, 3′ and 4′ of the benzene ring of 6‐BAP on both pK_a values was investigated. To determine the enthalpy and entropy, the temperature dependence of pK_a was employed. It was found that with increasing temperature the pK_a decreased. In comparison with 6‐BAP the chloro‐ or methoxy‐ group resulted in pK_a increase. The first pK_a values were also determined by linear sweep (LSV) and elimination voltammetry with linear scan (EVLS). New approaches were shown not only for the determination of pK_a from voltammetric titration curves but also for the evaluation of the reduction processes of benzylaminopurines.     

Determination of pKa values of nonsteroidal antiinflammatory drug‐oxicams by RP–HPLC and their analysis in pharmaceutical dosage forms

In this study, pK_a values were determined by using the dependence of the capacity factor on the pH of the mobile phase for four ionizable substances, namely, tenoxicam, piroxicam, meloxicam, and naproxen (I.S.). The effect of the mobile phase composition on the ionization constant was studied by measuring the pK_a at different ACN concentrations, ranging from 30 to 40%. The adequate condition for the chromatographic determination of these compounds in pharmaceutical dosage forms was established based on the different retention behaviors of the species. An octadecylsilica Nucleosil C18 column (150×4.6 mm, 5 μm) was used for all the determinations. The chromatographic separation of oxicams was carried out using acetonitrile (ACN)/water at 35% v/v, containing 65 mM phosphoric acid and UV detection at a wavelength of 355 nm. The method developed was successfully applied to the simultaneous determination of these drug compounds in laboratory‐prepared mixtures and their commercial pharmaceutical dosage forms. Each analysis requires no longer than 12 min.     

Hydrolyzed Vinyl Acetate–Divinylbenzene Copolymer Microspheres Containing L -Proline for Chiral Separation of Amino Acids

A new packing material for ligand-exchange chromatography, L -proline-modified hydrolyzed vinyl acetate-divinylbenzene copolymer microspheres, has been prepared and evaluated. The microspheres, prepared by a one-step swelling and polymerization method, have a narrow bead size (as determined by scanning electron microscopy, SEM), a broad pore-size distribution (by nitrogen adsorption) and, especially, inhomogeneous structural composition (by differential scanning calorimetry). The support, which has an L -proline content of 0.35 mmol g^–1 (nitrogen analysis), provides good enantioselectivity and column efficiency. Twenty-three of the twenty-four common D ,L -amino acids tested were resolved on a 250 mm × 4.6 mm i.d. column and mixtures of up to seven racemic amino acids were easily separated into their enantiomers. Two average pore diameters, volume-average (d_v) and surface-average (d_s) pore diameters, are defined. The ratio d_v/d_s is used to characterize the broadness of the pore-size distribution. It is shown that the widely used formula d=4V_p/S for cylindrical pores, where V_p is pore volume and S the specific surface area, gives the surface-average pore diameter.     

Synthesis of arborescent styrene homopolymers and copolymers from epoxidized substrates

The synthesis of arborescent styrenic homopolymers and copolymers was achieved by anionic polymerization and grafting. Styrene and p‐(3‐butenyl)styrene were first copolymerized using sec‐butyllithium in toluene, to generate a linear copolymer with a weight‐average molecular weight M_w = 4000 and M_w/M_n = 1.05. The pendant double bonds of the copolymer were then epoxidized with m‐chloroperbenzoic acid. A comb‐branched (or arborescent generation G0) copolymer was obtained by coupling the epoxidized substrate with living styrene‐p‐(3‐butenyl)styrene copolymer chains with M_w ≈ 5000 in a toluene/tetrahydrofuran mixture. Further cycles of epoxidation and coupling reactions while maintaining M_w ≈ 5000 for the side chains yielded arborescent copolymers of generations G1–G3. A series of arborescent styrene homopolymers was also obtained by grafting M_w ≈ 5000 polystyrene side chains onto the linear and G0–G2 copolymer substrates. Size exclusion chromatography measurements showed that the graft polymers have low polydispersity indices (M_w/M_n = 1.02–1.15) and molecular weights increasing geometrically over successive generations. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012