Maria Wojaczyńska

Structure and sorption properties of porous copolymers of acrylonitrile and divinylbenzene

Abstract The effect of the chemical structure of porous copolymers formed from actrylonitrile (AN) and divinylbenzene (DVB) containing various weight fractions of polar units (12, 19, 26, 40 and 58% AN) on their physicochemical and sorption properties has been examined. With increasing content of the polar units in the copolymers, their Kovats indices increase, suggesting the presence of stronger interactions of the polar sorbates with the copolymer surface. The sorption degrees of phenols and anilines have been found to depend more on the surface polarity than on its total area. The Hammett equation describes the sorption process well, thus suggesting that physical interactions are dominant. The selectivity of sorption, expressed in terms of the process constant in the Hammett equation, decreases as the content of AN units increases.

Synthesis and properties of acrylic carriers from acrylonitrile, vinyl acetate and divinylbenzene terpolymers

Abstract Two series of carriers based on acrylonitrile (AN)-vinyl acetate (VA)-divinylbenzene (DVB) terpolymers were obtained by aminolysis of nitrile groups to N-alkylamino ones. In the first series, the terpolymers differed in the content of VA units (7.5, 10, 20, and 30 mol.%). The modifying diluents used in the polymerization stage were: hexadecane (HD) and toluene (T). In the second series, the modifying diluents were: cyclohexanol (C), octanol (O), decanol (D), 2-ethylhexanol (E), and benzyl alcohol (B). The content of VA units was constant (20 mol.%). The IR spectra revealed that the aminolysis of nitrile groups of the terpolymers to N-ethylamino ones was accompanied by hydrolysis of the ester groups. The carriers with hydroxy groups, however, did not swell more than those obtained from AN-DVB copolymers. The concentration of amino groups was ∼ 1.8 mmol/g and the porosity was in the range 0.1–0.5, depending on the kind of diluent used in polymerization. The structural parameters of the carriers were characterized by the inverse GPC method with dextran solutions. The pore size (mean pore diameter) and its distribution width decreased with increasing VA unit content for the series HDT-7.5-HDT-30. In the second series, the porosity characteristics depended on the molecular shape of the thermodynamically bad diluent used. Acylase immobilized on those carriers had smaller activity than that immobilized on previously described carriers, whereas for glucoamylase and peroxydase the results of immobilization were very promising.

Porous terpolymers: poly(acrylonitrile-co-ethyl/butyl/acrylate-co-divinylbenzene)

Abstract A series of terpolymers was prepared from acrylonitrile, ethyl or butyl acrylate and divinylbenzene (10 wt%). The terpolymers were obtained by suspension polymerization with inert diluents. They had a porous structure unless the amount of acrylate exceeded 50 mol%. The porous structure, however, was not permanent. By heating the copolymers above T g or treating with solvents, a porosity as high as 40% could be made to disappear. The inverse gas chromatography (i.g.c.) measurements revealed that the segmental motion of terpolymer chains appeared in the temperature ranges where the segmental mobility of poly(acrylonitrile) is observed (∼95, 120–160°C). It may be concluded from the values of Kovats indices that the hydrophilicity of the surface area of terpolymers is higher than that of acrylonitrile-divinylbenzene copolymers.

Pentaerythritol triacrylate-homopolymer and its copolymers with butyl acrylate

Abstract The swelling and porosity change of the pentaerythritol triacrylate (PENTA) homopolymer and PENTA-butyl acrylate (BA) copolymers were investigated as a function of PENTA content (80, 60, 40 and 20 wt%). Polymers were synthesized by the suspension polymerization method using cyclohexanol and 2-ethylhexanol as inert diluents. The solubility parameter of poly(PENTA) ( 18.2 MPa 1 2 ) was estimated by swelling in the heptane and tetraline mixture. From the swelling of copolymers in the solvents toluene, THF, benzene and dioxane, one may conclude that the swelling of copolymers is not only a function of the solubility parameter of the solvent. The presence of hydroxyl groups in PENTA results in the highest sorption of dioxane. The porosity of copolymers in the swollen state is similar in all solvents. The porosity in the swollen state was characterized by inverse size exclusion chromatography (ISEC) using THF (polystyrene standards) and water (dextrane standards). Swelling in good solvents proceeds with an enlargement of the bead volume, hence the pore volume after swelling in THF is greater than in water in which the influence of hydroxyl groups leads to swelling of triacrylate segments at the cost of the pore volume. Copolymers synthesized with the higher diluents:monomer ratio are hydrogels with the ability to change their porosity, pore diameter and volume of beads. During drying, their pores collapse.

Comparison between structure and some properties of methacrylonitrile and acrylonitrile macroporous copolymers

Abstract The structure and properties of macroporous methacrylonitrile (MAN) copolymers are compared with those of acrylonitrile (AN) copolymers. These copolymers are crosslinked with divinylbenzene (DVB) or trimethylolpropane triacrylate (TMPA). All these copolymers were obtained by suspension polymerization from the monomer mixtures containing a good solvent — cyclohexanol and hexadecane. The copolymers are porous and their porosity in the dry state is much higher than in the swollen one. The swelling of these copolymers causes the average pore size to decrease. The kind of crosslinking agent is the most significant factor influencing the porous structure of the copolymers. MAN and TMPA copolymers (MAN-T) have the smallest average pore size and the narrowest pore distribution. Methacrylonitrile copolymers are better sorbents than acrylonitrile copolymers. Their aminolysis by ethylenediamine is much more difficult than that of the latter, but they are both suitable for lipase immobilization.

Transition metal complexes bound to macroporous resins carrying nitrile groups. Effect of matrix structure on the activity of supported catalysts

Abstract Two groups of resins bearing nitrile (CN) groups based on macroporous copolymers of acrylonitrile and divinylbenzene (AN/DVB) and terpolymers of styrene, acrylonitrile and divinylbenzene (S/AN/DVB) have been used as polymer matrices for the immobilization of Rh(I), Pt(II) and Pd(II) complexes. A group of four S/DVB resins functionalized with the CN ligands have been prepared and used for comparison. The resins differ in their chemical and physical structure, local concentration of the CN groups and their availability. Characterization of the heterogeneous complexes by IR spectroscopy confirmed the coordination of the metal ions to the polymer-CN ligands. The catalytic behaviour of the immobilized complex catalysts was tested in the hydrosilylation of 1-hexene. The activity of the polymer-bound catalysts strongly depends on the structure of the support used. The largest effect of the chemical structure of the polymer was found for the catalysts immobilized on the AN/DVB resins, while the polymer morphology played the major role in the high activity of the catalysts attached to the S/N/DVB resins. Lower activity was found for the systems bound to the functionalized S/DVB resins. Both polymer-supported Pt and Rh systems appeared to be highly effective for the hydrosilylation of the CC double bonds, but the platinum catalysts proved to be considerably more active. The rhodium catalysts were found efficient in the hydrosilylation of ketones. The immobilized Pd(II) complex was reduced to the metallic Pd by hydrosilanes. The supported Pt catalyst remained active when recycled 5 times, while the activity of the rhodium systems gradually decreased. The results offer the possibility of choosing the most suitable polymer matrix for the immobilization of metal complex catalysts for use in hydrosilylation and other catalytic reactions.

Polyacrylamide sorbents. Synthesis and sorption properties

Abstract A series of hydrophilic sorbents having amino groups was prepared by aminolysis of acrylonitrile-divinylbenzene copolymers with ethylenediamine and diethylenetriamine. The degree of transformation of nitrile groups was up to ca. 0.35. Sorption properties of the sorbents towards p -nitrophenol and methyl orange were compared. In both cases, the overall sorption capacity was found to be higher than for the parent acrylonitrile sorbents. The degree of sorption depended on both chemical and supermolecular structure and increased with specific surface area. The sorption of methyl orange was found to be related to the ion-exchange capacity of the sorbents, i.e., to their degree of chemical modification. In fact, the degree of sorption of the dye per ionic group was similar for all sorbents. For sorbents derived from the same parent copolymers, the effect of amino group basicity on degree of sorption was insignificant. The sorption of methyl orange was found to be controlled by internal diffusion with a diffusion coefficient lower by two to three orders of magnitude than those for porous ion exchangers.

Carriers from triacrylate for penicillin acylase immobilization

Abstract The properties of carriers made of acrylonitrile (AN) or butyl acrylate (BA) and crosslinked by trimethylolpropane trimethacrylate monomer (TMPMA) or trimethylolpropane triacrylate monomer (TMPA) are discussed. The extent of aminolysis of triacrylate copolymers depends on the comonomer composition. The carriers crosslinked with TMPMA have greater porosity and larger mean pore size than carriers that were crosslinked by TMPA. The enzyme activity on carriers that were obtained by ester group aminolysis in BA copolymers is higher than on carriers made of AN. It is found that TMPMA/BA carriers are the best for immobilization of peniccilin acylase.

Sorption of phenols on macroporous methacrylate copolymers containing epithio groups

Abstract The sorption of phenol and its derivatives from aqueous solutions (0.12 g l −1 ) on macroporous 2,3-epithiopropyl methacrylate (ETPMA)-ethylene dimethacrylate (EDMA) copolymers has been investigated using a dynamic method. In comparison with other EDMA and divinylbenzene copolymers having an even higher specific surface area, the ETPMA-EDMA copolymers exhibit a significant ability to sorb phenol and its hydrophobic derivatives. The specific sorption ability is connected with the presence of epithio groups on the polymer chain. This assumption is supported also by the fact that the splitting of thiorane rings in the ETPMA-EDMA copolymer by the reaction with ethylenediamine produces a serious decrease in its sorption capacity towards phenol. With an increasing content of ETPMA in the copolymer, its specific surface area decreases. The opposing effects of specific surface area and epithio group concentration are responsible for the constant value of ρ (which provides a measure of selectivity of the sorption process) for all the copolymers tested.