Pore memory of macroporous styrene–divinylbenzene copolymers

The variation of the pore structure of styrene–divinylbenzene (S–DVB) copolymer beads with the drying conditions was investigated. Macroporous S–DVB copolymer beads with various DVB contents were prepared in the presence of toluene‐cyclohexanol mixtures as a diluent. It was found that the pores of 10¹‐nm radius, corresponding to the interstices between the microspheres, collapse upon drying of the copolymers from toluene. The collapsed pores reexpand if the copolymers were dried from methanol. The collapse–reexpansion process of the pores was found to be reversible, indicating that the actual pore structure formed during the crosslinking copolymerization is memorized by the copolymer network. The magnitude of the pore structure variation increased on worsening the polymer–diluent interactions during the gel formation process due to the simultaneous increase in crosslink density distribution. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1055–1062, 1999     

Swelling of porous styrene–divinylbenzene copolymers in water

The swelling capacity of porous styrene–divinylbenzene (DVB) copolymers in water was studied by displacing methanol from the swollen polymer. The copolymers with different amounts of DVB were prepared in the presence of solvents with different solvating powers as inert diluents. Using a solvating solvent or its mixture with a nonsolvent as diluent, most of the obtained copolymers increase their volume in water, and the increase in volume becomes more significant with increasing the degree of crosslinking in some range of the DVB contents. The swelling capacity in water for the same copolymers with a high degree of crosslinking is linearly dependent on the dilution degree in the initial reaction mixture, to some extent. The unusual swelling behaviors in water were explained by the inner strain, which existed mainly in the less crosslinked domains between the highly crosslinked microgel particles, which are released in the course of swelling of the copolymers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 536–544, 2000     

The formation and structure of suspension-polymerized styrene–divinylbenzene copolymers

Porous polymers were prepared by suspension copolymerization of styrene/divinylbenzene in various ratios together with various quantities of diluents, both solvating and nonsolvating. Parallel bulk polymerizations were made to detect the onset of gelation and phase separation. The dry polymeric beads were examined by a range of techniques: apparent densities; mercury porosimetry; nitrogen sorption/desorption isotherms, vapor sorption, equilibrium swelling, and electron microscopy. The properties of the porous polymers are discussed in terms of phase separation during polymerization consequent on either an unfavorable polymer–solvent interaction or a microsyneresis.     

Heterogeneous styrene–divinylbenzene copolymers in collapsed and reexpanded states

The pore structure of styrene–divinylbenzene (DVB) copolymers formed by phase separation before or after gelation was compared using apparent densities and mercury porosimetry. The copolymers were prepared with di-2-ethylhexyl phthalate (DOP) as diluent. The pore structure of copolymers formed in homogeneous gelation can collapse upon drying in the rubbery state. The collapsed pores have a mean diameter of about 100–200 Å corresponding to the interstices between the microspheres. The collapsed microspheres reexpand again during the sulfonation or chloromethylation reactions, or during the solvent exchange. The pore structure of styrene–DVB networks formed in heterogeneous gelation do not collapse on drying in the swollen state, this being a stable and permanent porosity. The critical crosslink density for transition from homogeneous to the heterogeneous gelation represents a borderline between stable and unstable porosity. The drastical change of swelling and porosity values at the critical crosslink density is due to the collapse of unstable pores.     

Composition analysis of crosslinked styrene–ethylene dimethacrylate and styrene–divinylbenzene copolymers by Raman spectroscopy

A method for the determination of composition and content of pendent double bonds in untreated samples of styrene–ethylene dimethacrylate and styrene–divinylbenzene copolymers from Raman spectra has been developed. By computer treatment of spectra it was shown that Raman spectra are sensitive to the distribution of components in the studied copolymers.     

Heterogeneous styrene–divinylbenzene copolymers. Stability conditions of the porous structures

The change in the porosity of styrene–divinylbenzene (S–DVB) copolymers during drying as a function of the quality of the diluent and of the divinylbenzene (DVB) concentration was investigated after drying the networks from water (maximum porosity) and from toluene (stable porosity). Two different diluents, namely toluene and cyclohexanol, were used in the polymerization system at a fixed volume fraction of the organic phase (0.50). The phase separation in toluene is accompanied by a slight deswelling of the network phase, whereas that in cyclohexanol leads to largely unswollen network phase. The stable porosity increases abruptly over a narrow range of the DVB concentration, i.e., between 40 and 50% DVB in toluene and between 15 and 25% DVE in cyclohexanol. The maximum porosity increases almost linearly with increasing DVB concentration up to a certain value, and then remains constant. The results indicate that the two main factors which determine the physical state of the swollen heterogeneous S–DVB copolymers, as well as the stability of the porous structures, are (1) the critical conversion at the incipient phase separation and (2) the degree of the inhomogeneity in crosslink distribution.     

New soybean oil–styrene–divinylbenzene thermosetting copolymers. I. Synthesis and characterization

The cationic copolymerization of regular soybean oil, low‐saturation soybean oil (LoSatSoy oil), or conjugated LoSatSoy oil with styrene and divinylbenzene initiated by boron trifluoride diethyl etherate (BF₃·OEt₂) or related modified initiators provides viable polymers ranging from soft rubbers to hard, tough, or brittle plastics. The gelation time of the reaction varies from 1 × 10² to 2 × 10⁵ s at room temperature. The yields of bulk polymers are essentially quantitative. The amount of crosslinked polymer remaining after Soxhlet extraction ranges from 80 to 92%, depending on the stoichiometry and the type of oil used. Proton nuclear magnetic resonance spectroscopy and Soxhlet extraction data indicate that the structure of the resulting bulk polymer is a crosslinked polymer network interpenetrated with some linear or less‐crosslinked triglyceride oil–styrene–divinylbenzene copolymers, a small amount of low molecular weight free oil, and minor amounts of initiator fragments. The bulk polymers possess glass‐transition temperatures ranging from approximately 0 to 105°C, which are comparable to those of commercially available rubbery materials and conventional plastics. Thermogravimetric analysis (TGA) indicates that these copolymers are thermally stable under 200°C, with temperatures at 10% weight loss in air (T₁₀) ranging from 312 to 434°C, and temperatures at 50% weight loss in air (T₅₀) ranging from 445 to 480°C. Of the various polymeric materials, the conjugated LoSatSoy oil polymers have the highest glass‐transition temperatures (T_g) and thermal stabilities (T₁₀). The preceding properties that suggest that these soybean oil polymers may prove useful where petroleum‐based polymeric materials have found widespread utility. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 658–670, 2001     

New soybean oil–styrene–divinylbenzene thermosetting copolymers. v. shape memory effect

A series of new shape memory polymers are synthesized by the cationic copolymerization of regular soybean oil, low saturation soybean oil (LoSatSoy oil), and/or conjugated LoSatSoy oil with styrene and divinylbenzene, norbornadiene, or dicyclopentadiene initiated by boron trifluoride diethyl etherate or related modified initiators. The shape memory properties of the soybean oil polymers are characterized by the deformability (D) of the materials at temperatures higher than their glass‐transition temperatures (T_g), the degree to which the deformation is subsequently fixed at ambient temperature (FD), and the final shape recovery (R) upon being reheated. It is found that a T_g well above ambient temperature and a stable crosslinked network are two prerequisites for these soybean oil polymers to exhibit shape memory effects. Good shape memory materials with high D, FD, and R values are prepared by controlling the crosslink densities and the rigidity of the polymer backbones. The advantage of the soybean oil polymers lies in the high degree of chemical control over the shape memory characteristics. This makes these materials particularly promising in applications where shape memory properties are desirable. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1533–1543, 2002; DOI 10.1002/app.10493     

Styrene–divinylbenzene copolymers. II. The conservation of porosity in styrene–divinylbenzene copolymer matrices and derived ion-exchange resins

The collapse of pores in styrene–divinylbenzene copolymers and corresponding ion-exchange resins was studied during the removal of solvating liquids. The process can be followed in a most simple way by measuring the volume of the bead-shaped copolymers upon drying. Other parameters observed during drying were the apparent density and incidently the internal surface. The collapse of pores is considered to be a result of cohesional forces when solvated polymer chains are approaching each other by loss of solvent. The effect will thus be more pronounced in gel-type networks than in porous ones. In porous networks, the effect will be stronger in smaller pores than in larger ones. It is shown that crosslinks, increasing the rigidity of the structures, will favor the conservation of porosity. In ion-exchange resins the pore stability is best when the material is in its lowest state of hydration. Generally, the collapse of pores is a reversible process. The collapsed material can in most cases be reswollen by the proper choice of solvent.     

Porous structure and swelling properties of styrene–divinylbenzene copolymers for size exclusion chromatography

Small spherical particles of styrene–divinylbenzene copolymers have been synthesized by modified suspension polymerization. The effects of divinylbenzene (DVB) contents, dilution degree of the monomers and diluent composition on the porous structure and swelling properties of the copolymers were investigated. Toluene uptakes of macroporous copolymers were considered as a result of three contributions: filling of the fixed pores, expansion of the fixed or collapsed pores, and nuclei swelling and heptane uptakes as a result of the two first contributions. The increase of DVB content in the copolymers synthesized in presence of a solvating diluent (toluene) provoked a decrease on the nuclei swelling. The increase of dilution degree with solvating diluents changed the toluene and heptane uptakes, and when the diluent–copolymer affinity was reduced, the fixed pore volume increased. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1257–1262, 1997     

Porous maleic anhydride–styrene–divinylbenzene copolymer beads

The formation of the porosity and the pore stability in maleic anhydride–styrene–divinylbenzene (MAn–St–DVB) copolymer beads were investigated using the apparent density measurements of the samples dried from methanol (maximum porosity) and from dioxane (stable porosity). The copolymer beads were prepared by the suspension polymerization method in glycerol instead of water as the dispersing medium. A toluene–dioxane (1:1) mixture was used as the diluent at a fixed volume fraction of the organic phase (0.47). Compared to St–DVB copolymers prepared in the presence of nonsolvating diluents, porous MAn–St–DVB copolymers are obtained at relatively low DVB concentration, i.e., at 1–3% DVB. The porosity of the copolymers increases with decreasing MAn concentration in the feed due to the decrease in the copolymer yield. The results of the elemental analyses and titrimetric methods indicate that approximately only half of the MAn units in the copolymer are able to react with amine or with water. A possible rearrangement of the MAn units into the cyclopentanone structures was suggested.     

Mechanical behavior and structure of single beads of homogeneous and macroporous styrene–divinylbenzene copolymers

The stress–stain and ultimate behavior in compression of homogeneous and macroporous beads of styrene–divinylbenzene copolymers has been investigated in the dry state or in equilibrium with toluene, acetone, methanol, and water. The penetration modulus A indicates sensitively the transition from the glassy into the rubbery state induced by an increase in temperature or swelling. For macroporous copolymers, A of the glassy polymers is mainly determined by the porosity P, while in the rubbery region it primarily depends on the matrix structure (degree of crosslinking and concentration and composition of the diluent). The high value of the slope s of the A vs. P dependence (s ～ ?3) for macroporous copolymers is evidence of the complex deformation mechanism (bucking of pore walls). The relative compression at break, ε_b=0.3–0.4, is independent of the composition, and the compressive strength is roughly proportional to the penetration modulus.     

A facile and efficient method for preparation of chiral supported poly(styrene–divinylbenzene) copolymers

A new and efficient method for preparation of optically active poly(styrene–divinylbenzene) copolymers (PS-DVB) is presented here. This is carried out by Friedel–Crafts acylation reaction of chiral N-phthaloyl -leucine acid chloride with PS-DVB beads in the presence of aluminum chloride as Lewis acid catalyst and 1,2-dichloroethane as the solvent at ambient temperature. Reagents’ amounts and reaction conditions are mentioned and four samples with different amounts of functionality have been prepared. Final products were characterized by FT-IR and elemental analysis. The results obtained confirm that the above modification in preparation of chiral supported PS-DVB has been achieved well and in moderate yield.     

Phase separation in the synthesis of styrene–divinylbenzene copolymers with di-2-ethylhexyl phthalate as diluent

Phase separation by suspension copolymerization of styrene–divinylbenzene (DVB) with di-2-ethylhexyl phthalate (DOP) as diluent was investigated using equilibrium swelling, swelling rate, apparent densities, and mercury porosimetry. The copolymer prepared in the absence of DOP is heterogeneous, showing that a phase separation exists in the polymerization system, and, in the presence of DOP, the propagating copolymer separates earlier. Furthermore, with increasing amounts of DVB, phase separation occurs earlier than gelation, which causes a sudden increase in the amount of pores about 200–500 Å in diameter corresponding to the interstices between the microspheres.     

Modification of styrene–divinylbenzene copolymer by anchoring ferric–dipyridylamine complex

Polystyrene–divinylbenzene (PS–DVB) copolymer was modified by anchoring dipyridylamine (DPA) on it followed by complexation with Fe(III). Under the experimental conditions followed, 9% incorporation of Fe(III) was achieved. PS–DVB–DPA and PS–DVB–DPA–Fe(III) were characterized by IR spectra. Diffuse reflectance spectra for PS–DVB–DPA–Fe(III) and DPA–Fe(III) revealed λ_max at ～ 360 and ～ 310, respectively. This difference could be due to a difference in the nature of the coordinating moieties complexing with Fe(III) in these two systems. Scanning electron micrographs of PS–DVB, PS–DVB–DPA–Fe(III), and heat-treated PS–DVB–DPA–Fe(III) revealed some typical surface features. Thermal stability varied in the order PS–DVB–DPA–Fe(III) > PS–DVB–DPA ?PS–DVB, and DTA showed characteristic exotherms. © 1992 John Wiley & Sons, Inc.     

Styrene–divinylbenzene copolymers. Construction of porosity in styrene divinylbenzene matrices

Experimental data are presented describing the formation of porosity in styrene–divinylbenzene copolymers as a function of the organic components present during the suspension polymerization. The reaction system contains a mixture of diluents such as toluene and hexane, which results in matrices that differ significantly in pore structure from the porous resins so far known. From these data a model of the physical structure is proposed.     

Kinetic studies on styrene–divinylbenzene copolymerization by suspension technique

Kinetic studies on styrene and divinylbenzene (DVB) copolymerization by the suspension technique in a toluene diluent initiated by benzoyl peroxide are reported. Evaluation of the important reaction parameters is carried out. The crosslinked styrene–DVB copolymers can absorb toluene to a maximum swelling ratio of 17. The absorption/desorption took place instantaneously and reached the maximum value within 10 min, and it could be repeated many times, yet gave the consistent result. Rate equations evaluated by both integral and differential methods are investigated. High monomer orders of 1.5–2.3 were obtained. The activation energy for the polymerization was about 40 kcal/mol^?1. Autoacceleration was found even at low conversions. The acceleration was influenced by both monomer, crosslinker, and initiator concentrations. The integral and differential methods for the rate evaluation were compared, and the relationship between the rate equation and polymerization behavior was elucidated. The kinetic orders determined for this copolymerization show considerable deviation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1521–1540, 2001     

Morphological study on the reactivity of styrene‐divinylbenzene copolymers in a chloromethylation reaction

Styrene‐divinylbenzene (S‐DVB) copolymers with different kinds of porous structures were synthesized by aqueous suspension polymerization using n‐heptane as the pore forming agent. The amount of this solvent (monomer dilution degree) and the DVB content in the organic phase were varied. The combination of three different dilution degree values and three DVB contents yielded three series of copolymers with a variety of porous structures. The three series were composed by copolymers with pore diameters (D) in the following ranges: D < 500 Å, 500 < D < 1000 Å, and D > 1000 Å, respectively. The effect of synthesis conditions on the pore size distribution and on the copolymer matrix rigidity was evaluated. These copolymers were submitted to a chloromethylation reaction with a paraformaldehyde/gaseous HCl mixture in the presence of zinc chloride as a Lewis acid catalyst and 1,2‐dichloroethane as solvent. The effect of the copolymer porosity on the chloromethylation reaction extension was evaluated. It was possible to observe that a gel copolymer with a high swelling capacity in the reaction medium achieved the same chloromethylation yield observed for a high porous copolymer. This result thus indicates that, in the case of the chloromethylation reaction studied here, the high swelling capacity of the gel copolymer can counterbalance its limited surface area, turning this type of polymer structure as reactive as a macroporous one. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Cut growth properties of styrene–butadiene copolymers

The cut growth properties of styrene–butadiene block and random copolymers are considered in terms of the tearing energy theory. It is found that the value of T₀ (the minimum value of tearing energy below which no cut growth takes place in the absence of chemical effects) is far higher for a styrene–butadiene resin copolymer system with a high amount of bound styrene resin than for a conventionally vulcanized SBR elastomer. Similarly, it is shown that the value of T₀ for a butadiene–styrene block copolymer (thermoplastic rubber) is considerably reduced when the material is crosslinked. It is proposed that the value of T₀ is influenced by the hystersial properties of the rubber.