J. Hradil

Mechanism of phase-transfer catalysis using glycidyl methacrylate-ethylene dimethacrylate copolymers modified with tributylammonium groups in nucleophilic displacement reactions

Abstract The kinetics of phase-transfer catalysis using glycidyl methacrylate-ethylene dimethacrylate resins modified with pendant quaternary butylammonium groups have been studied. In contrast to expectations based on currently proposed mechanisms, the activity of polymeric catalysts is not improved through modifications that balance the hydrophilic and hydrophobic properties of the material. It is believed that much of the activity of the polymeric catalysts derives from the swelling of the polymer in both aqueous and organic phases. This enhances not only the rate of diffusion of both reagents to the vicinity of the catalytically active groups but also the ability of reactive groups to oscillate between the two phases. Both swelling and diffusion are restricted severely as the percentage of crosslinking is increased. This restriction is of particular importance with macroporous resins. Comparison of kinetic data obtained with various polymers suggests that gel polymers with very small bead sizes and therefore high external surface areas provide much higher reactivities than their macroporous counterparts.

Investigation of the surface structure of polymers by chromatographic methods. VI: Determination of glass transition temperature of macroporous copolymers by gas chromatography

Abstract By employing the method of inverse gas chromatography and using the retention diagrams of methanol and heptane in the temperature range between −55 and + 180°C, the glass transition temperatures, T g , were determined for glycidyl methacrylate—ethylene dimethacrylate ( T g = 40°C) and styrene—divinylbenzene ( T g = 100°C) macroporous copolymers. The standard method (differential thermal analysis) failed in these instances. For macroporous copolymers, a disturbance is observed in the dependence on reciprocal of temperature, not only for the retention volume, but also for the peak asymmetry, width and area, which is proportional to the response. Using the dependence log V MeOH / V C 7 H 16 , not only T g , but also a change in the polarity of the individual types of copolymers can be determined. At low temperatures (−55°C), the polarities of macroporous copolymers approach each other owing to the “freezing” of polymer chains. Constant properties are assumed by the polymer surface only above T g where the polarity decreases in the order macroporous glycidyl methacrylate—ethylene dimethacrylate copolymer, the above methacrylate copolymer with chemically bonded PEG and styrene—divinylbenzene copolymer (Synachrom E5). A similar picture of the polarity of these polymers is also provided by the enthalpy of solution (Δ H s ) and enthalpy of adsorption (Δ H a ) of methanol and heptane determined for the copolymers investigated.

Sorption of phenols on macroporous methacrylate copolymers containing ethyleneamine groups

Abstract The sorption of several phenols on macroporous methacrylate copolymers containing ethyleneamine groups was investigated. The phenols are more strongly sorbed on the more polar methacrylate copolymers than on styrene-divinylbenzene copolymers. The sorption is positively affected by the presence of ethyleneamine groups. The suggested mechanism of sorption can be successfully documented by linear dependences of free energy according to equations of the Hammett type.

Phase-transfer catalysis. IV. Localization of reaction sites in supported catalysts☆

Abstract Assuming that there is no basic difference between the two-phase (PTC) and three-phase (TC L-S-L) catalysis, as in both cases the active anion must be transferred from the aqueous phase into the organic phase and the displaced anion must be transferred back into the aqueous phase, possible routes of the transfer are demonstrated. It was found that the activities of catalysts immobilized on a polymer or inorganic carrier did not differ much from each other. The dependence of reaction rate on particle size and its independence of pore size are used to demonstrate that the reaction may proceed predominantly in the surface zone of the catalyst. Experimental data seem to prove that the cause of the surface reaction does not consist of a considerably higher reaction rate compared with the diffusion of the substrates to reaction sites. An analysis of the results of controlled sorption of the Cu(II) ion and of the reaction between the polymer and an agent soluble only in the organic phase, the course of which can be followed by observing the cross-section of the particle, seems to favour a view that pores of the catalyst are filled with one phase only (usually, the continuous aqueous phase), which effectively prevents diffusion of the other phase into the particles.

Reactive polymers XLVIII synthesis of polymeric sorbents with carboxylic groups by chemical reactions of the copolymer dihydroxypropyl methacrylate-ethylene dimethacrylate☆

Two routes starting from the copolymer of dihydroxypropyl methacrylate with ethylene dimethacrylate and leading to a product containing carboxylic groups were investigated. Carboxymethylation of hydroxylic groups of the copolymer with chloroacetic acid gives a product with a maximum content of groups not exceeding 3 mmol/g COO−, even after repeated treatment. Hydrolysis of ester groups of methacrylate units sometimes gives products with a considerably higher content of carboxylic groups, but at the expense of changes in the internal structure of the polymeric sorbent. Effects of temperature, reaction time, alkali and solvent concentrations, which allow the course of hydrolysis and content of carboxylic groups in the polymer to be controlled, were investigated.

Gas chromatographic and sorption properties of macroporous metahcrylate copolymers

Abstract The chromatographic properties of copolymers of 2,3-epoxypropyl methacrylate and 2,3-epithiopropyl methacrylate with ethylene dimethacrylate and of their derivatives modified with amines were investigated by means of gas chromatography and by the sorption of sulphur and carbon dioxides. The relative retention volumes and the changes in the free energy of adsorption of various compounds depend on the extent of the specific surface area of copolymers and on the content of functional groups. A study of the sorption of different compounds revealed that with increasing specific surface area the non-specific interactions increase while specific interactions decrease. This suggests that the accessibility of functional groups decreases with increasing extent of cross-linking of the sorbent.

The amine modified acrylic copolymers as catalysts in the reaction of octylbromide with sodium cyanide

SummaryAmine-modified and alkylated (with butyl bromide or hexyl bromide) acrylonitrile-butyl acrylate-divinylbenzene terpolymers and alkyl acrylate-divinylbenzene copolymers (where alkyl=methyl, ethyl or butyl) were used as catalysts in the reaction of octyl bromide with cyanide anions. The dependence of catalytic activity as a function of the acrylate content and swelling properties was investigated. The most effective catalyst was butyl acrylate-divinylbenzene copolymer. This sample showed maximum toluene uptake from the toluene/water mixture.

Solute-solvent interactions of macroporous methacrylate ion exchangers in salt form studied by gas chromatography

Abstract Interaction of macroporous methyl methacrylate copolymers carrying strongly acidic sulphopropyl groups exchanged with metal ions of the IIb, VIb, VIIIb and rare earth groups of the Periodic Table with solutes—homologous alkanes, aromatic hydrocarbons, ketones, alcohols and organic acids— were studied by gas chromatography. The results show that the sorbents belong to class 3 according to Kiselev since, in addition to interactions due to dispersion forces, they also exhibit strong specific interactions. In comparison with the original copolymers, the ion exchangers carrying sulphopropyl groups exhibit stronger specific interactions, in particular with alcohols, due to hydrogen bonding. The methacrylate-based ion exchangers in salt form exhibit weaker specific interactions than the same sorbents in H + form. Non-specific interactions involving dispersion forces generally predominate.

Reactive polymers XLIV Sorption of gases on macroporous 2,3-epoxypropyl methacrylate co-polymers modified with amino groups of various structure

Abstract The macroporous co-polymer of 2,3-epoxypropyl methacrylate with ethylene dimethacrylate was modified by using amines containing primary, secondary and tertiary amino groups. Fe 3+ , Co 3+ , Co 2+ and Ni 2+ salts were equilibrium sorbed on the co-polymer modified with diethylenetriamine. An investigation of the sorption and desorption of acidic gases (sulphur and carbon dioxides) on these polymers containing hydroxyl and amino groups showed that both the sorption and desorption capacity towards these acidic gases can be regulated. Co-polymers subsequently modified with cations readily sorbed not only sulphur dioxide, but also ammonia.