Polymer catalyst soluble

Polymerization of triphenylmethyl methacrylate in the presence of a chiral anion catalyst results in a polymer with a helical structure that can be coated onto macroporous silica [742,804). Enantioselectivity in this case results from insertion and fitting of the analyte into the helical cavity. Aromatic compounds and molecules with a rigid nonplanar structure are often well resolved on this phase. The triphenylmethyl methacrylate polymers are normally used with eluents containing methanol or mixtures of hexane and 2-propanol. The polymers are soluble in aromatic hydrocarbons, chlorinated hydrocarbons and tetrahydrofuran which, therefore, are not suitable eluents. 

The formation of relatively ill-defined catalysts for epoxide/C02 copolymerization catalysts, arising from the treatment of ZnO with acid anhydrides or monoesters of dicarboxylic acids, has been described in a patent disclosure.968 Employing the perfluoroalkyl ester acid (342) renders the catalyst soluble in supercritical C02.969 At 110°C and 2,000 psi this catalyst mixture performs similarly to the zinc bisphenolates, producing a 96 4 ratio of polycarbonate polyether linkages, with a turnover of 440 g polymer/g [Zn] and a broad polydispersity (Mw/Mn>4). Related aluminum complexes have also been studied and (343) was found to be particularly active. However, selectivity is poor, with a ratio of 1 3.6 polycarbonate polyether.970... 

New approaches to catalyst recovery and reuse have considered the use of membrane systems permeable to reactants and products but not to catalysts (370). In an attempt to overcome the problem of inaccessibility of certain catalytic sites in supported polymers, some soluble rho-dium(I), platinum(II), and palladium(II) complexes with noncross-linked phosphinated polystyrene have been used for olefin hydrogenation. The catalysts were quantitatively recovered by membrane filtration or by precipitation with hexane, but they were no more active than supported... 

Polymers containing pendant carbamate functional groups can be prepared by the reaction of phenyl isocyanate with poly(vinyl alcohol) in homogeneous dimethylsulfoxide solutions using a tri-ethylamine catalyst. These modified polymers are soluble in dimethyl sulfoxide, dimethylacetamide, dimethylformamide and formic acid but are insoluble in water, methanol and xylene. Above about 50% degree of substitution, the polymers are also soluble in acetic acid and butyrolactone. The modified polymers contain aromatic, C = 0, NH and CN bands in the infrared and show a diminished OH absorption. Similar results were noted in the NMR spectroscopy. These modified polymers show a lower specific and intrinsic viscosity in DMSO solutions than does the unmodified poly(vinyl alcohol) and this viscosity decreases as the degree of substitution increases. 

The hydrogenation of unsaturated polymers like polyisoprene is based on the mobility of a soluble catalyst in the reaction medium. In the hydrogenation of such unsaturated polymers the soluble catalyst brings its active site to the C=C bonds in the polymer chain. In contrast, a heterogeneous catalyst requires that the polymer chain unfold to gain access to a catalytically active site on the surface of a metal particle. 

Ewen was the first to report the synthesis of stereoregular propene polymers with soluble Group 4 metal complexes and alumoxane as the co-catalyst [13], He found that Cp2TiPh2 with alumoxane and propene gives isotactic polypropene. This catalyst does not contain an asymmetric site that would be able to control the stereoregularity. A stereo-block-polymer is obtained, see Figure 10.6. Formation of this sequence of regular blocks is taken as a proof for the chain-end control mechanism. 

Molecular catalysts, often in the form of metal ions complexed to a suitable ligand, can also be attached to dendrimer surfaces [3,9,10,93,94,96,148,149]. Such materials are generally structurally better defined than catalysts bounded to linear polymers, but like random-polymer catalysts they can be easily separated from reaction products. Note, however, that this approach results in a synthetic dead-end as far as further manipulation of the terminal groups is concerned, and thus some of the advantages of using dendrimers, such as solubility modulation, are lost. 

More recently, the scope of using hyperbranched polymers as soluble supports in catalysis has been extended by the synthesis of amphiphilic star polymers bearing a hyperbranched core and amphiphilic diblock graft arms. This approach is based on previous work, where the authors reported the synthesis of a hyperbranched macroinitiator and its successful application in a cationic grafting-from reaction of 2-methyl-2-oxazoline to obtain water-soluble, amphiphilic star polymers [73]. Based on this approach, Nuyken et al. prepared catalyticaUy active star polymers where the transition metal catalysts are located at the core-shell interface. The synthesis is outlined in Scheme 6.10. 

Recently, Mecking et al. reported the synthesis of inverse micelles based on a hy-perbranched polyglycerol polymer. Terminal -OH groups were modified with palmi-toyl chloride and gave a polymeric catalyst soluble in organic solvents with hydrophilic core to immobilize water-soluble guest molecules such as PdCl2 or Pd(OAc)2. 

Related work was done with variously substituted acrylates in an ionic liquid 87). It was found that the solubility of both monomers and polymers depends on the chain length of the alkyl group linked to the ester. Methyl acrylate and its polymer are soluble in [BMIMJPF. However, butyl acrylate (BA) is only partially soluble, and the corresponding polymer is insoluble in the ionic liquid. The ATRP of BA in the ionic liquid proceeded under biphasic conditions with the catalyst, CuBr/pentamethyldiethylenetriamine, dissolved in the ionic liquid phase. Relatively low-molecular-weight polymer was formed. In this case, as the polymer was insoluble in the ionic liquid, it was spontaneously separated from the ionic liquid phase free of copper contamination. Furthermore, an undesirable side-reaction was significantly reduced in the ionic-liquid-phase ATRP 87). 

In 2001, soluble polymer catalysts 111, poly-(Z,)-leucine bound to polyethylene glycol, were introduced by Roberts group (Scheme 51). In this catalyst a short peptide chain... 

Price and McAndrew (105) have copolymerized trioxane with THF using Ph3C+SbClg as catalyst. The polymer was soluble in acetone and melted at 36-37° C. 

The reaction is exothermic and proceeds rapidly at room temperature. The polymerization is generally performed by passing oxygen or air through a stirred solution of the catalyst and monomer in an appropriate solvent. When the desired molecular weight is attained, the polymer is isolated by dilution of the reaction mixture with a nonsolvent for the polymer. The precipitated polymer is then removed by filtration, washed thoroughly and dried. The polymer is soluble in most aromatic hydrocarbons and chlorinated hydrocarbons and insoluble in alcohols, ketones and aliphatic hydrocarbons. 

Dihydrogen can be rather easily evolved with Systems 10-15 of Table 1, where, with PET across the membrane, the water-soluble radical cation MV+ is produced outside the vesicle. This radical cation can evolve dihydrogen from water in the presence of various catalysts. This was demonstrated by Tsvetkov et al. [262] for System 12 of Table 1. As a catalyst, the c water soluble hydrogenase from Thiocapsa roseopersicina was used or a heterogeneous rhodium-polymer catalyst [263]. The quantum yield of H2 production was comparable with the quantum yield of MV+ generation. 

The use of borane-containing monomers clearly presents an effective and general approach in the functionalisation of polyolefins, which has the following advantages stability of the borane moiety to coordination catalysts, solubility of borane compounds in hydrocarbon solvents (such as hexane and toluene) used as the polymerisation medium, and versatility of borane groups, which can be transformed to a remarkable variety of functionalities as well as to free radicals for graft-form polymerisations. The functionalised polymers are very effective interfacial modifiers in improving the adhesion between polyolefin and substrates and the compatibility in polyolefin blends and composites [518],... 

The catalytic performance of the fluoropolymer ligands 1 and 2 was first tested in the fluorous biphase hydroformylation of 1-alkenes, styrene and n-butyl acrylate. The reaction was conducted in a batch reactor in a 40/20/40 vol% hexane/toluene/perfluoromethylcyclohexane solvent mixture (10 mL). The catalyst was formed in situ by adding [Rh(CO)2(acac)] (5 rmol, P/Rh = 6) to the polymer-containing solvent mixture followed by introduction of syngas (30 bar, CO/H2 = 1/1). Table 2 summarises the results obtained. The salient features of the results are Firstly, the activity of the fluorous soluble polymer catalysts are significantly higher than that reported for solid polymer- and aqueous soluble polymer-supported rhodium catalysts.18-22 For example, the average turnover frequency (TOF) for the fluorous biphase hydroformylation of 1-decene is 136 mole aldehyde h-1 per mol of rhodium catalyst with an aldehyde selectivity of 99%. In comparison, a rhodium catalyst supported on the... 

Table 2 Fluorous Biphase Hydroformylation of Olefins by Soluble Polymer Catalysts ...

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