Architecture of rod–brush block copolymers synthesized by a combination of coordination polymerization and atom transfer radical polymerization

A combination of coordination polymerization and atom transfer radical polymerization (ATRP) was applied to a novel synthesis of rod–brush block copolymers. The procedure included the following steps: (1) the monoesterification reaction of ethylene glycol with 2-bromoisobutyryl bromide (BIBB) yielded the bifunctional initiator monobromobutyryloxy ethylene glycol and (2) a trichlorocyclopentadienyl titanium (CpTiCl₃; bifunctional initiator) catalyst was prepared from a mixture of CpTiCl₃ and bifunctional initiator. The coordination polymerization of n-butyl isocyanate initiated by such a catalyst provided a well-defined macroinitiator, poly(n-butyl isocyanate)–bromine (PBIC–Br). (3) The ATRP method of 2-hydroxyethyl methacrylate initiated by PBIC–Br provided rod [poly(n-butyl isocyanate) (PBIC)]–coil [poly(2-hydroxyethyl methacrylate) (PHEMA)] block copolymers with a CuCl/CuCl₂/2,2′-bipyridyl catalyst. (4) The esterfication of PBIC-block-PHEMA with BIBB yielded a block-type macroinitiator, and (5) ATRP of methyl methacrylate with a block-type macroinitiator provided rod–brush block copolymers. We found from the solution properties that such rod–brush block copolymers formed nanostructured macromolecules in solution. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Enantioselective Hydrogenation of Aromatic Ketones Catalyzed by a Mesoporous Silica‐Supported Iridium Catalyst

A mesoporous, silica‐supported, chiral iridium catalyst with a highly ordered dimensional‐hexagonal mesostructure was prepared by postgrafting the organometallic complex (1‐diphenylphosphino‐2‐triethylsilylethane)[(R,R)‐1,2‐diphenylethylenediamine]iridium chloride {IrCl[PPh₂(CH₂)₂Si(OEt)₃]₂[(R,R)‐DPEN] (DPEN=1,2‐diphenylethylenediamine)} on SBA‐15 silica. During the asymmetric hydrogenation of various aromatic ketones under 40 atm of hydrogen, the mesoporous, silica‐supported, chiral iridium catalyst exhibited high catalytic activity (more than 95% conversions) and excellent enantioselectivity (up to more than 99% ee). The catalyst could be recovered easily and used repetitively seven times without significantly affecting the catalytic activity and the enantioselectivity.     

Polymerization of n-Hexyl Isocyanate with Rare Earth Catalyst Composed of Nd(P204)3/Al(i-Bu)3

Summary Rare earth catalyst system: lanthanide phosphonate/tri-i-butyl aluminum (Nd(P₂₀₄)₃/Al(i-Bu)₃) has been found for the first time as a novel catalyst for the polymerization of n-hexyl isocyanate (HNCO). Nd(P₂₀₄)₃ and Nd(P₅₀₇)₃ are the commercial names of neodymium 2-ethylhexyl phosphonates, their formulas are shown in table 1. The catalyst can be prepared easily by mixing Nd(P₂₀₄)₃ and Al(i-Bu)₃. The effects of catalyst, solvent, reaction temperature and time on the polymerization of HNCO were studied. The obtained poly (n-hexyl isocyanate) (PHNCO) was characterized by GPC, FT-IR, ¹H-NMR and TGA. The resulting PHNCO had molecular weight (Mn=39.6×10⁴, Mv=67.2×10⁴), molecular weight distribution (MWD=2.44) and yield (82.7%) under the moderate reaction conditions: catalyst concentration [Nd]=6.65×10^-2mol/L, Al/Nd=10 molar ratio, [HNCO]/[Nd]=100 molar ratio, at -10^oC for 10h in bulk. Relatively high reaction temperature (-10^oC) is the most distinct virtue. The IR and NMR analyses show that the polymer obtained is not polyether but polyisocyanate.     

Rheo‐kinetic evaluation on the formation of urethane networks based on hydroxyl‐terminated polybutadiene

Rheo‐kinetic studies on bulk polymerization reaction between hydroxyl‐terminated polybutadiene (HTPB) and di‐isocyanates such as toluene‐di‐isocyanate (TDI), hexamethylene‐di‐isocyanate (HMDI), and isophorone‐di‐isocyanate (IPDI) were undertaken by following the buildup of viscosity of the reaction mixture during the cure reaction. Rheo‐kinetic plots were obtained by plotting ln (viscosity) vs. time. The cure reaction was found to proceed in two stages with TDI and IPDI, and in a single stage with HMDI. The rate constants for the two stages k₁ and k₂ were determined from the rheo‐kinetic plots. The rate constants in both the stages were found to increase with catalyst concentration and decrease with NCO/OH equivalent ratio (r‐value). The ratio between the rate constants, k₁/k₂ also increased with catalyst concentration and r‐value. The extent of cure reaction at the point of stage separation (x_i) increased with catalyst concentration and r‐value. Increase in temperature caused merger of stages. Arrhenus parameters for the uncatalyzed HTPB‐isocyanate reactions were evaluated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1869–1876, 2001     

Copolymerization of norbornene and <Emphasis Type="Italic">n</Emphasis>-butyl methacrylate catalyzed by bis-(β-ketoamino)nickel(II)/B(C<Subscript>6</Subscript>F<Subscript>5</Subscript>)<Subscript>3</Subscript> catalytic system

Abstract  

Copolymerization of norbornene with n-butyl methacrylate (n-BMA) was carried out with catalytic systems of bis-(β-ketoamino)nickel(II) complexes Ni{RC(O)CHC[N(naphthyl)]CH₃}₂ (R = CH₃, CF₃) and B(C₆F₅)₃ in toluene and exhibited high activity for both catalytic systems. Influence of the catalyst structure and comonomer feed content on the polymerization activity as well as on the incorporation rates were investigated. The catalysis was proposed to involve the insertion mechanism of norbornene and n-BMA catalyzed by bis-(β-ketoamino)nickel(II)/B(C₆F₅)₃ catalytic systems, and the decreasing polymerization activity with an increasing content of n-BMA in the feedstock composition could be attributed to the competition of carbonyl group coordination onto the Ni(II) active center instead of the olefin double bond. The reactivity ratios were determined to be r _n-BMA = 0.095 and r _norbornene = 12.626 by the Kelen–Tüd?s method. The copolymer films prepared show good transparency in the visible region.     

Study on ketalization reaction of poly(vinyl alcohol) by ketones. IV. Reaction between poly(vinyl alcohol) and aliphatic ketones and behavior of polyvinylketal in water

Ketalization reaction of poly(vinyl alcohol) (PVA) by aliphatic ketones, dimethylsulfoxide (DMSO) as solvent, under the presence of acidic catalyst, in homogeneous system was carried out and the synthesis of polyvinylketals were successfully performed. The equilibrium constant at 40°C is ca. 0.07 in the case of methyl n-propyl ketone (nPK) and methyl n-butyl ketone (nBK), but is ca. 0.05 in the case of methyl i-propyl ketone (iPK) and ca. 0.01 in the case of methyl i-butyl ketone (iBK) and methyl t-butyl ketone (tBK), respectively. Moreover, the ketalization degree of polyvinylketal by iBK and tBK reached to only ca. 35 mol % as the maximum. It seems that these were due to steric hindrance of bulky side chain of ketones. But the heat of reaction is 7.5 kcal/mol in all aliphatic ketones, it seems to proceed the same ketalization reaction mechanism. Films prepared from the polyvinylketals were soaked in water and degree of swelling, solubility, and hydrolysis of films were measured. The reaction of film with water, in acidic side, at first the film swells, and then, as the deketalization reaction proceeds, the film dissolves in water. The dissolution time is controlled by the kind of ketones, ketalization degree, and pH of water which reveals that deketalization reaction proceeds proportional to proton concentration. It is more difficult to dissolve highly ketalized polyvinylketals obtained by propyl ketones and butyl ketones than that by acetone. The hydrolysis of polyvinylketal film proceeds in the order as follows: acetone > MEK > nPK > iPK ≒ nBK > iBK > tBK. This phenomenon seems to be affected by hydrophobicity of the film surface which depends upon the kind of the original ketones.     

Uranium Permeation from Nitrate Medium Across Supported Liquid Membrane Containing Acidic Organophosphorous Extractants and their Mixtures with Neutral Oxodonors

Permeation of U(VI) from nitric acid solution has been studied across supported liquid membrane (SLM) using bis[2,4,4 trimethyl pentyl] phosphinic acid (Cyanex 272) either alone or in combination with neutral donors like Cyanex 923 (a mixture of four trialkyl phosphine oxides viz. R₃PO, R₂R′PO, RR′₂PO, and R′₃PO where R: n-octyl and R′: n-hexyl chain), TBP (tri-n-butyl phosphate), and TEHP (tris-2-ethylhexyl phosphate) dissolved in n-paraffin as carriers. Effect of various other parameters such as nature and concentration of receiver phase, feed acidity, uranium concentration, pore size, and membrane thickness on U(VI) transport across SLM were investigated. Transport behavior of U(VI) was also compared with other derivatives of phosphoric acids like 2-ethylhexyl phosphonic acid-mono-2-ethylhexyl ester (PC88A), dinonyl phenyl phosphoric acid (DNPPA) under identical conditions and it followed the order: Cyanex 272 > PC88A > DNPPA. 2 M H₂SO₄ was suitable for effective U(VI) transport across SLM. Presence of neutral donors in carrier showed significant enhancement in U(VI) permeation in the order: Cyanex 923 > TBP > TEHP. U(VI) transport decreased with increased membrane thickness as well as decrease in pore size. The optimized conditions were tested for recovery of U(VI) from uranyl nitrate raffinate (UNR) waste generated during purification of uranium.     

Grafting onto wool. XVI. Graft copolymerization of vinyl monomers by use of TBHP–FAS as redox initiator

Methyl acrylate (MA), methyl methacrylate (MMA), and n-butyl vinyl ether (n-BVE) have been graft-copolymerized onto Himachali wool in an aqueous medium by using tertiary butyl hydroperoxide ferrous ammonium sulfate (TBHP-FAS) redox system at 40°C, 50°C, 60°C, and 70°C for various reaction periods. Percentage of grafting and percent efficiency have been determined as functions of concentration of monomers, molar ratios of [TBHP]/[FAS], time and temperture. Molar ratios of [TBHP]/[FAS] were found to influence grafting of different monomers studied. Chemical evidence indicates that a covalent bond formation occurs between grafted polymeric chain and backbone polymer. The rate of grafting (R_p) and induction period (I_p) of different monomers towards graft copolymerization were determined as function of total initial monomer concentrations. R_p and I_p of n-BVE are independent of total initial monomer concentrations while R_p and I_p of both MA and MMA were found to depend on the total initial monomer concentrations. MA, MMA, and n-BVE were found to differ in reactivity towards grafting onto wool in the presence of (TBHP-FAS) redox system; the following reactivity order was observed: MMA > MA > n-BVE.     

On the Mechanism of n-Butyl Vinyl Sulfide Formation with [K(18-crown-6)SBu] as catalyst

n-Butyl mercaptane reacts with acetylene in the presence of [K(18-cr-6)SBu] as catalyst to give n-butyl vinyl sulfide. In toluene the reaction is of zero^th order with respect to BuSH and first order with respect to [K(18-cr-6)SBu]. The reaction rate depends on the solvent in the following order: toluene > triglyme ≈ BuSH ≈ dioxane ≫ BuOH. In toluene, BuOH added in equimolar amounts accelerates the reaction indicating a complex formation [K(18-cr-6) (BuOH)SBu] with a higher catalytic activity. [K(18-cr-6)SBu] is monomeric in the solid state with d(K–S) = 3.051(2) Å. Potassium is displaced out of the mean plane defined by the six oxygen atoms of the crown ether by 0.626(3) Å. [K(18-cr-6)SBu] is a strong electrolyte in alcohols but practically no electrolytic dissociation takes place in solvents with low dielectric constants such as toluene and n-butyl mercaptane. From the results a reaction mechanism is derived with the addition of non-dissociated [K(18-cr-6)SBu] to acetylene as the rate-determining step.     

Structural and Catalytic Studies of a Trimethyltin Vanadate Coordination Polymer

The organotin vanadate [Me₃SnVO₃] (1) has been prepared and characterised in the solid state by powder X-ray diffraction (XRD), thermogravimetric analysis, multinuclear magic-angle spinning (MAS) NMR, IR and Raman spectroscopy. The phase purity and structure of microcrystalline 1 were confirmed by carrying out a full Rietveld structural refinement at ambient temperature and from conventional powder XRD. ⁵¹V and ¹¹⁹Sn MAS NMR data for compound 1 were in agreement with the predicted structure, showing two equally-abundant, nonequivalent Me₃Sn groups and two equally-abundant, nonequivalent vanadium atoms. The compound was applied as a catalyst for the liquid-phase epoxidation of olefins at 55 °C using tert-butyl hydroperoxide (tBuOOH) as the oxidant. The reaction rate for the different substrates followed the order cis-cyclooctene > (R)-(+)-limonene ≅ trans-2-octene > cyclododecene > styrene > 1-octene; the corresponding epoxides were the only observed products. Leaching tests indicated that the catalytic epoxidation of cyclooctene was mainly heterogeneous in nature. This paper is dedicated to Professor Ian Manners and his scientific accomplishments.     

The mechanism of stabilization of poly(vinyl chloride). II. Cleavage of organotin sulfur compounds by anhydrous hydrogen chloride

A number of organotin compounds of the type R_nSn Y_4–n, where R = alkyl or aryl; Y = alkylthio, arylthio or carbothiolate; and n = 1, 2, 3 have been prepared and treated with hydrogen chloride at 180°C in o-dichlorobenzene solution. The organotin compounds were also tested at 190°C as thermal stabilizers for PVC. Cleavage of tin–carbon bonds by hydrogen chloride was demonstrated in some cases by analysis of the organotin–hydrogen chloride reaction products. The formation of monoalkyl(aryl)tin chlorides or stannic chloride, or both, in the model system was shown to correspond to a catastrophic mode of degradation in the polymer. The use of stabilizers with fewer than two alkyl or aryl groups on tin also gave this mode of degradation.     

Synergetic Effect of Tetrabutylammonium Bromide and Polyethylene Glycol as Phase Transfer Catalysts in Third Liquid Phase for Benzyl-n-Butyl Ether Synthesis

This study intends to clarify the forming characteristics of third liquid phase in phase transfer catalytic system in the presence of n-butanol and potassium hydroxide when tetrabutylammonium bromide, polyethylene glycol and their mixture serve as phase transfer catalyst, respectively. At 323 K, the three catalytic systems were applied to yield benzyl-n-butyl ether from benzyl chloride and n-butanol, and they performed distinct reaction activity. Among them, a combination of two kinds of catalyst results in a synergetic effect in reaction activity.     

A pronounced catalytic activity of heteropoly compounds supported on dealuminated USY for liquid-phase esterification of acetic acid with n-butanol

12-Phosphotungstic acid and its cesium salts supported on a dealuminated ultra-stable Y zeolite were prepared, and showed the high catalytic activity in the liquid-phase esterification of acetic acid with n-butanol. The supported Cs_2.5H_0.5PW₁₂O₄₀ catalyst gave a high conversion of n-butanol of 94.6% and a selectivity for n-butyl acetate of 100%, accompanying the high water-tolerance and catalytic reusability without regeneration.     

An environmentally friendly FeTiSOx catalyst with a broad operation-temperature window for the NH3-SCR of NOx

A novel FeTiSO_x catalyst prepared by a simple hydrolysis coprecipitation method was used for the selective catalytic reduction (SCR) of NO_x with NH₃, which exhibited high catalytic activity (NO_x conversion of >97% and N₂ selectivity of >95%) and tolerance for both H₂O and SO₂ at a broad temperature window of ~325–475°C. The characterization results showed that the formation of Fe–O–Ti and Fe–O–S species could significantly enhance the acidic sites of the catalyst, which play an important role in NH₃ absorption and their catalytic activity. The Fe³⁺ ions in the bulk anatase TiO₂ could significantly enhance the redox properties for the SCR reaction and suppress the side reaction of NH₃ oxidation to NO or N₂O. In addition, the reaction mechanism was discussed based on in situ diffuse reflectance infrared Fourier transform spectroscopy measurements and kinetic investigation, indicating that the reaction was dominated by the Eley–Rideal mechanism over the FeTiSO_x catalyst.     

Thiosemicarbazone Salicylaldiminato‐Palladium(II)‐Catalyzed Mizoroki–Heck Reactions

Four tridentate thiosemicarbazone salicylaldiminato‐palladium(II) complexes of the general formula [Pd(saltsc‐R)PPh₃] [saltsc=salicylaldehyde thiosemicarbazone; R=H ( 1 ), 3‐tert‐butyl ( 2 ), 3‐methoxy ( 3 ), 5‐chloro ( 4 )], have been evaluated as catalyst precursors for the Mizoroki–Heck coupling reaction between a variety of electron‐rich and electron‐poor aryl halides and olefins. The palladium complexes (0.1–1 mol% loading) were found to effectively catalyze these reactions with high yields being obtained when aryl iodides and aryl bromides were utilized. The effects of base, catalyst loading, reaction temperature and reaction time on the catalytic activity of the most active complex were also investigated.     

Surface-tension properties of some polydispersed alkyl-substituted polyoxyethylated phenylsulfonamides

Twenty-nine laboratory-prepared polydisperse nonionic surfactants, derived from polyoxyethylatedN-alkylphenylsulfonamides [RϕSO₂ N(R′) (EO)_nH], have been characterized. EO is ethyoxylation;R is hydrogen,n-butyl ort-butyl;R′ is hexyl, octyl, or decyl; and (EO)_n is varied from (EO)₄ to (EO)₂₀. Surface tension in aqueous solution was studied. The critical micelle concentration, surface excess, minimum area per molecule, effectiveness of surface-tension reduction, and free energy of micelle formation were calculated from the surface-tension measurements. The critical micelle concentrations for the derivatives in whichR′-hexyl were considerably higher than the corresponding derivatives whereR′ is octyl or decyl. The greatest surface-tension reduction was found in theR′=n-octyl derivatives whereR ist-butyl with (EO)₉ orn-butyl with (EO)₁₁. Deceased.     

Pd(0)-<Emphasis Type="Italic">S</Emphasis>-methylisothiourea grafted onto mesoporous MCM-41 and its application as heterogeneous and reusable nanocatalyst for the Suzuki,Stille and Heck cross coupling reactions

In this project palladium (0) S-methylisothiourea was grafted into MCM-41 mesoporous silica. Palladium (0) S-methylisothiourea complex supported on MCM-41 (Pd(0)-SMT-MCM-41), as heterogeneous and reusable catalyst, was used in C–C bond formation between various aryl halides with sodium tetraphenylborate or phenylboronic acid (Suzuki reaction), aryl halides with triphenyltin chloride (Stille reaction), and aryl halides with styrene or n-butyl acrylate (Heck reaction). This catalyst was characterized by various physico-chemical techniques such as X-ray diffraction, transmission electron microscopy, scanning electron microscopy (SEM/EDX), thermal gravimetric analysis (TGA/DTA), fourier transform infrared spectroscopy and inductively coupled plasma. The results indicated that Pd(0)-SMT-MCM-41 catalyst could be easily recovered from reaction mixture for several consequence runs without significant loss of its catalytic activities.     

Infrared study of catalytic reduction of lean NOx with alcohols over alumina-supported silver catalyst

Two intense IR absorption bands due to surface isocyanate (-NCO) species have been observed at 2262 and 2232 cm^–1 when an alumina-supported silver catalyst is exposed to a mixture of NO, O₂ and ethanol at 150°C and subsequently heated to > 300°C in vacuum. The intensity of the isocyanate band is hardly affected by the water existing in the mixture. Methanol is less reactive than ethanol for the formation of isocyanate species. The reaction mechanism of catalytic reduction of lean NOx with alcohols is discussed based on these IR spectroscopic findings.     

Suzuki–Miyaura Reactions of Aryl Chloride Derivatives with Arylboronic Acids using Mesoporous Silica‐Supported Aryldicyclohexylphosphine

The Suzuki–Miyaura reactions using mesoporous‐supported aryldicyclohexylphosphine as ligand have been investigated. The catalysts were based on SBA‐15 type mesoporous silica which was transformed in a four‐step synthesis leading to a phosphine‐containing hybrid material The most productive catalytic system studied was generated in situ from this material and the homogeneous palladium complex, Pd(OAc)₂. Other catalytic systems were studied for comparison [homogeneous cataysts, a “preformed” catalyst obtained by reaction of PdCl₂(PhCN)₂ and the phosphine‐containing material]. Variations involving the solvent system, the substrate aryl chloride and the arylboronic acid reactant were also studied. For both in situ and preformed catalyst systems, high conversions and yields are obtained for activated aryl chlorides. Success of the reaction for unactivated aryl chlorides was limited to the catalyst formed in situ. The catalyst formed in situ was also shown to be reactive under aqueous reaction conditions in the cross‐coupling of 1‐(4‐chlorophenyl)ethanone with phenylboronic acid.     

Reactions of phenolic ester alcohol with aliphatic isocyanates—transcarbamoylation of phenolic to aliphatic urethane: A 13C‐NMR study

Reactions of aliphatic isocyanates with a phenolic ester alcohol (PHEA) were investigated using ¹³C‐NMR spectroscopy. PHEA has two reactive sites: a phenolic  OH group and a secondary aliphatic  OH group. Both  OH groups react with the isocyanate groups. With an organotin catalyst, dibutyltin dilaurate (DBTDL), the aliphatic  OH group reacts first. With a tertiary amine catalyst, 1,4‐diazabicyclo[2.2.2]octane (DABCO), or triphenylphosphine (Ph₃P) or even in the absence of a catalyst at room temperature (RT) the phenolic  OH group reacts first. With the organotin catalyst, the reactions are generally complete in a day at RT. With DABCO or triphenylphosphine or DNNDSA catalysts, the reactions are almost complete only in 3–4 days at RT in ethyl acetate or acetonitrile. Uncatalyzed reactions are slower. With an acid catalyst such as dinonylnaphthalenedisulfonic acid (DNNDSA), both  OH groups react with the isocyanate. When equimolar quantities of PHEA and hexamethylenediisocyanate (HDI) polymerize at RT or reflux in the presence of a catalyst, both  OH groups react, with the phenol reacting slowly. Upon refluxing, the phenolic  OH‐based urethane slowly rearranges (transcarbamoylation) to the aliphatic  OH‐based urethane. DABCO and Ph₃P catalysts effect this rearrangement at a much slower rate than does the acid catalyst. In the presence of a catalytic amount of DBDTL in a refluxing solvent, this rearrangement is complete in 2 h. By refluxing the phenolic–OH‐based urethane in isopropanol, the mechanism of transcarbamoylation was found to be intermolecular. The mechanism is likely to involve deblocking of the phenolic urethane and subsequent reaction of the isocyanate generated, with the aliphatic  OH group. This conclusion was confirmed by differential scanning calorimetry (DSC) experiments. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2212–2228, 2000