André Revillon

Functional polymers supported on porous silica. II : Radical polymerization of vinylbenzyl chloride from grafted precursors

Abstract Vinylbenzyl chloride was chosen as a model monomer for grafting a functional polymer onto silica carrying radical active precursors, such as monomer, transfer agent or initiator, previously grafted onto silica via a suitable coupling agent. The grafting efficiency was studied as a function of the texture of the initial silica, the nature of the active precursor and the polymerization conditions. Evidence for grafting was obtained from FTIR and 29Si CP-MAS NMR spectra, and the thickness of the grafted layer was estimated from surface area and porosimetry measurements. From molecular weight measurements of nongrafted polymer it can be deduced that there is a trend toward the elongated conformation of the grafted polymer. Attempts to separate the grafted polymer through digestion of the silica with HF, failed to give a soluble linear polymer except when the active precursor was a transfer agent; in the two other cases a crosslinked polymer with a low crosslink density was obtained, which kept the morphology of the initial silica.

Reagents on styrene-divinylbenzene supports with improved accessibility

Abstract Macroporous styrene-divinylbenzene copolymers have been prepared using a solution of polystyrene in toluene as a porogenic diluent. Pore volume and pore size distribution are critically dependent on both the amount and the concentration of the diluent solution. Attempts to graft first a radical azo generator and then to use it for grafting a functional polymer are described but were not fully successful. A second approach was the post-polymerization of vinylbenzyl chloride through the residual double bonds of the initial resin, after swelling in a concentrated solution of the monomer. The chloromethylated porous resin was further derivatized to a sulfoxide containing one. A two-step process was employed involving first a phase transfer sulfuration and then an oxidation. The first reaction was limited to an extent depending mostly on the initial chlorine content of the resin. The final product was used as a catalyst for the alkylation of benzyl cyanide with butyl bromide. The catalytic activity, although lower than that of a soluble copolymer of the same composition as the graft, was definitely higher in terms of rate and upper limit than that of conventional macroporous or gel-type catalysts.

Cationic benzyl nickel complexes as homogeneous catalysts for styrene oligomerization. X-ray crystal structure of [Ni(η3-CH2C6H5)(PPh3)2]PF6 · CH2CI2 *

Abstract New cationic complexes [Ni(η3-CH2C6H5)(PPh3)2]PF6 (3) and [Ni(η3-CH2C6H5)((+)-DIOP)]PF6 (4) were synthesized from the corresponding neutral compounds [Ni(η3-CH2C6H5)X(PR3)2] (X = Cl, Br), by metathetical halide abstraction with TIPF6. Complex 3 was characterized by X-ray crystallography and shown to have a distorted square-planar geometry with the benzylic group coordinated in a quasi-allylic fashion. Crystals are monoclinic, space group P21/n, a = 11.798(5), b = 19.251(2), c = 18.561(3) A, β = 93.03°, V = 4208.6 A3. Solution NMR studies showed benzyl fluxionality and phosphine lability in compound 3, but not in 4. The latter one is catalytically inactive towards styrene oligomerization, whereas 3 produces styrene oligomers ( M ¯ n ≈ 1000 ) with 67% isotactic content. Although [Ni(η3-CH2C6H5)CI(PCy3)] and trans[Ni(Cl)(H)(PCy3)2] are inactive, addition of TlPF6 induced catalytic activity with formation of highly isotactic (90%) styrene oligomers with similar M ¯ n and a different terminal group.

Functional polymers supported on porous silica. I : Grafting active precursors onto porous silica

Abstract A set of porous silica has been grafted with trialkoxysilane coupling agents carrying either a γ-propyl methacryloyl group, a γ-propyl thiol or a γ-propyl amine group. The grafts have been characterized by diffuse reflectance Fourier transform infrared spectroscopy and 29Si and 13C cross-polarization magic-angle-spinning nuclear magnetic resonance; the grafting yields were estimated from elemental analysis. The grafted amine was further reacted with azobiscyanovaleric acid. The grafted materials are to be used as co-monomer, transfer agent or initiator for a further grafting of a functional polymer via a radical polymerization.

Macroporous gel-type styrene-divinylbenzene materials

SummaryThe title materials are produced from macroporous styrene (St)-divinylbenzene (DVB) resins prepared in the presence of a polymer solution as a porogen; the resulting beads are functionalized upon grafting St-Vinylbenzylchloride (VBC) copolymers through post-copolymerization with residual double bonds. The resulting material has been quaternized by trimethylamine at 35° C. The rate constant of that reaction is then about 6 times higher than that observed for a similar resin (same Cl content and same porous morphology) prepared by direct terpolymerization of St, DVB and VBC.

Analogous reaction for maximum sulfonation of polysulfones

SummaryThe sulfonation of the model compounds of the structural units of the polysulfones and bis phenol A polyethersulfones has been conducted up to completion using SO3 in a dichloroethane solution at room temperature. Whatever the initial structure may be, only one sulfonic group per aromatic ring can be attached. Water soluble polymers with the same degree of sulfonation can be prepared, without chain scission.

Alternatives to Size Exclusion Chromatography

Abstract Size Exclusion Chromatography (SEC) is a convenient and powerful method for polymer characterization, but alternatives have appeared to overcome its limitations or improve its responses. These methods are examined, comparing their advantages and disadvantages, with a special attention to Hydrodynamic Chromatography (HDC).

Macromer copolymerization reactivity ratio determined by GPC analysis

SummaryIn this paper is decribed a new method for determining copolymerization reactivity ratios r by using high resolution gel permation chromatography. The system of monomers is a new one involving a macromer. Separation of each monomer, copolymer and solvent allows calculation of concentration of reactants and products, so as the copolymer molecular weight distribution.Three different methods were used to interprete copolymerization experiments, at various feed compositions, and in function of conversion, in minimizing errors on peak surface area. The conventional methods were used to calculate r and evaluate their accuracies.

Interpretation of the Gel Permeation Chromatography Behaviour of Three Types of Copolymers

Abstract The chromatographic elution of a series of random, block and graft PVC copolymers (with styrene, butadiene, methylmethacrylate, vinylacetate, vinylidene chloride in a large range of composition) is studied. With the help of three consecutive detectors, the composition, molecular weight and intrinsic viscosity of these products are determined and related to the conditions of the synthesis. Results are compared to those obtained by direct measurements. The elution is different for each type of copolymer, varying with the composition but some viscosity-molecular weight relations have been obtained.

Functional silica supported polymer V ‘Onto’ versus ‘from’ grafting processes

Abstract Silanes are versatile coupling agents. They represent an easy way of chemically bonding polymers to silica. Two processes have been considered: polymerization from a coupling agent grafted on the surface; and reaction of a prefunctionalized polymer by condensation of its alkoxy head with silanols of the surface. Each of them has advantages and limitations. We focus here on the ‘onto’ grafting mechanism. The main advantages are the control of polymerization degree in the first step of polymer synthesis which occurs in a homogeneous medium and the easy polymer characterization of the soluble precursor. The semi-batch procedure avoids molecular weight shift and broadening with conversion. Grafting efficiency is measured in function of polymer chain length, which indicates a steric limitation by the silica pore size. Trialkoxy silanes are more reactive than monoalkoxy for silica coverage and exhibit a better chemical resistance.