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     

Sulfonation and characterization of poly(styrene-isobutylene-styrene) triblock copolymers at high ion-exchange capacities

In this study, a triblock copolymer, poly(styrene-isobutylene-styrene), was sulfonated to eight different levels ranging from 0.36 to 2.04 mequiv./g (13 to 82 mol% of styrene; styrene is 19 mol% of the unsulfonated block copolymer). These sulfonated polymers were characterized with elemental analysis and infrared spectroscopy to confirm sulfonation and determine accurate sulfonation levels. Infrared analysis revealed four additional stretching vibrations as a result of sulfonation. Also, a linear relationship between absorbance at 1006 cm⁻¹ (stretching of the aromatic ring in styrene caused by the para-substituted sulfonic acid) and sulfonation level (measured by elemental analysis) was found. The density and water solubility of all the sulfonated polymers were measured and increased with increasing sulfonation level, as high as 1.31 g/cm³ and 351 wt%, respectively. In addition, a sulfonated triblock copolymer at 79 mol% sulfonation was neutralized with a cesium cation and revealed an increase in density, but a reduction in water solubility. This study demonstrates the resulting unique properties of sulfonated styrene-based block copolymers at higher ion-exchange capacities than previously reported.     

Sulfonation studies of copolymers,graft copolymers,and polymeric gels using phase transfer catalysts

A new sulfonation method using phase transfer catalysts was applied to sulfonate a number of polymer matrices in an aqueous two-phase system. The polymer matrices included in this study are (1) styrene (Sty) and acrylonitrile (AN) copolymers with glycidyl methacrylate (GMA), (2) graft copolymers of cellulose with GMA, and (3) polystyrene and polyacrylate gels containing GMA as comonomer. The presence of polar groups such as AN in the polymer matrix makes the sulfonation easier. For cellulose graft copolymers, the extent of sulfonation was not much affected by the phase transfer catalysts, presumably due to the high polarity and high water uptake capacity of the cellulose base. For other polymer gels, the following factors influence the extent of sulfonation: (1) the method of gel synthesis, i.e., gels synthesized by delayed addition of GMA give a higher degree of sulfonation; (2) the nature of the crosslinking agent, i.e., gels with ethylene glycol diacrylate (EGDA) gives a higher degree of sulfonation than gels with divinylbenzene (DVB); (3) the pore size of the gels, i.e., gels with larger pore sizes gave higher degree of sulfonation; (4) increasing polarity of the backbone structure of gels favors increased sulfonation, e.g., MMA–GMA–EGDA gels give 54% sulfonation, whereas Sty–GME–EGDA gives only 38%.     

Swelling and network parameters of high oil‐absorptive network based on 1‐octene and isodecyl acrylate copolymers

Crosslinked 1‐octene‐isodecyl acrylate copolymers were synthesized and evaluated for oil‐absorbency applications. The copolymer was crosslinked at different concentrations of ethylene glycol diacrylate (EGDA) and EG dimethacrylate (EGDMA) crosslinkers via catalytic initiation or by electron‐beam irradiation at a dose rate 80 kGy. The concentration of both crosslinkers was varied from 0.5 to 2%. The effects of the crosslinking conditions such as crosslinker concentration, method of polymerization and monomer concentrations on the conversion and gel fraction were examined through oil‐ absorption tests using petroleum crude oil. It was found that the oil absorbency was influenced mainly by the degree of crosslinking and the hydrophobicity of the copolymer units. The final equilibrium oil content, volume fraction of the polymer, and swelling capacity were determined at 298 K. The effective crosslinking density, average molecular weight between the crosslinks, and polymer–toluene interaction parameter were determined from stress–strain measurements. The crosslinking efficiencies of EGDA and EGDMA toward copolymers were determined. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 80–91, 2005     

Preparation and application of sulfonated poly(1‐octene‐co‐styrene)

In this article, 1‐octene and styrene was copolymerized by the supported catalyst (TiCl₄/ID/MgCl₂). Subsequently, by sulfonation reaction, sulfonated poly(1‐octene‐co‐styrene)s which were amphiphilic copolymers were prepared. The copolymerization behavior between 1‐octene and styrene is moderate ideal behavior. Copolymers prepared by this catalyst contain appreciable amounts of both 1‐octene and styrene. Increase in the feed ratio of styrene/1‐octene leads to increase in styrene content in copolymer and decrease in molecular weight. As the polymerization temperature increases, the styrene content in the copolymers increases, however, the molecular weight decreases. Hydrogen is an efficient regulator to lower the molecular weights of poly(1‐octene‐co‐styrene)s. The sulfonation degree of the sulfonated poly(1‐octene‐co‐styrene)s increased as the styrene content in copolymer increased or the molecular weight decreased. Thirty‐six hour is long enough for sulfonation reaction. The sulfonated poly(1‐octene‐co‐styrene)s can be used as effective and durable modifying agent to improve the wettability of polyethylene film and have potential application in emulsified fuels and for the stabilization of dispersions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Radiation synthesis of hydrogels to enhance sandy soils water retention and increase plant performance

Preparation and characterization of superabsorbent hydrogels obtained by radiation induced crosslinking of polyacrylamide (PAAm), poly(acrylic acid) (PAAc), poly(vinyl alcohol) (PVA), and potassium polyacrylate (PAAcK) were investigated individually and in (PAAm)–binary systems for possible uses in agricultural fields. The swelling of the investigated hydrogels was mainly related to the type of their hydrophilic functional groups and/or the presence of polarized charges. The preparation conditions, such as irradiation dose and hydrogel blend compositions, that influence the water absorbency of PAAm/PAAcK copolymers and alter their gel content and crosslinking density were investigated. The higher the irradiation dose, the higher the gel content, and the lower the water absorbency. PAAm/PAAcK copolymer, possessing pore structure and fast swelling, was prepared by mixing the hydrogel components with a gas‐forming agent, namely, ammonium carbonate. Studies were also made on the applications of such hydrogels to improve the physical and water retention properties of sandy soil for agricultural purposes. The effect of different types and amounts of hydrogels added to sandy soil on the emergence, vegetative growth, and wilting time of corn (Zea mays) plants was investigated. As the hydrogel level increased, the average of plant height, leaf width, total dry weight, corncob production, and time to wilt increased. The obtained results suggested that the PAAm/PAAcK hydrogels can improve sandy soil properties for cultivation, because they often absorb and keep water one thousand times more than their own weight, reduce watering frequency of the plants, and enhance water retention of soil matrix that results in an increase in plant growth and performance. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1360–1371, 2004     

Internal stresses in hypercrosslinked polystyrene: Polarized optical studies

Polarized optical microscopy is used for studying the hypercrosslinked PS network prepared by the crosslinking of DC swollen spherical beads of styrene copolymer containing 0.5% of divinylbenzene by monochlorodimethyl ether up to 100% crosslinking. The removal of the solvent decreases the volume of the sample and leads to the development of internal stresses, which manifest themselves as strong optical anisotropy of dry beads. On the contrary, upon swelling in toluene, the network is expanded and shows anisotropy. When the network swells in any thermodynamically good solvent, existing stresses invert their sign and this network appears to be free of any internal stresses. This state of the network should be treated as the ϑ state, in which beads are optically isotropic. This state can also be achieved by swelling of a hypercrosslinked polymer in methanol, which eliminates compressive stresses in the hypercrosslinked network via increase in volume but cannot extend it like toluene. Conventional gel copolymers of styrene with divinylbenzene prepared without any toluene or in the presence of minor amounts of toluene are fully isotropic only in their dry state. These copolymers are inert to methanol but swell in hexane and cyclohexane, and their swelling is accompanied by the development of internal stresses.     

Swelling of High Oil-Absorptive Network Based on 1-Octene and Isodecyl Acrylate Copolymers

Crosslinked 1-octene-isodecyl acrylate copolymers were synthesized and evaluated for oil-absorbency application. The copolymer was crosslinked at different concentrations of ethylene glycol diacrylate (EGDA) and ethylene glycol dimethacrylate (EGDMA) crosslinkers via catalytic initiation or by electron-beam irradiation at dose rate 80 kGy. The concentration of both crosslinkers was varied from 0.5% to 2%. The effect of crosslinking conditions, such as crosslinker concentration, method of polymerization and monomers concentration on conversion and gel fraction was examined through an oil-absorption test using petroleum crude oil. It was found that, the oil absorbency was influenced mainly by the degree of crosslinking and the hydrophobicity of the copolymer units. The final equilibrium oil content, volume fraction of polymer and swelling capacity were determined at 298 K. The effective crosslinking density V_e, the average molecular weight between the crosslinks M_c and the polymer-toluene interaction parameter were determined from stress–strain measurements. The crosslinking efficiencies of EGDA and EGDMA towards copolymers were determined.     

Preparation of copoly(vinyl alcohol–styrenesulfonic acid) resin and its catalytic activity on hydrolysis of carbohydrates. II. Two-step polymerization using tetraethylthiuram disulfide as an initiator

Copoly(vinyl alcohol–styrenesulfonic acid) resin was prepared by a two-step polymerization, consisting of a suspension polymerization of styrene containing divinylbenzene using tetraethylthiuram disulfide as an initiator and a subsequent block copolymerization of vinyl acetate to the crosslinked polystyrene obtained, followed by sulfonation and saponification. Some reaction conditions in the polymerization of styrene were investigated to obtain copolymer containing more vinyl alcohol units. The catalytic activity of the copolymer on the hydrolysis of dextrin was investigated and found to be increased with increasing amount of vinyl alcohol units and with a lowering degree of crosslinking of the copolymer. The maximum acceleration of rate obtained in the presence of the copolymer was about six times that in the presence of Amberlite 120B. Catalytic activity of the copolymer on hydrolysis of sucrose and methyl acetate were also investigated and found to be comparable each other and lower than that for dextrin. The difference between the activities for dextrin and for sucrose and methyl acetate increased with an increasing amount of vinyl alcohol units in the copolymer.     

Photocrosslinking of styrene–isoprene–styrene; effect of benzoin and ethylene glycol dimethacrylate on physical properties

Crosslinking reaction of polymer by ultraviolet (UV) irradiation has been important in industries. In this work, photocrosslinking of styrene–isoprene–styrene (SIS) triblock copolymer in the presence of benzoin photoinitiator and a dimethacrylate monomer as crosslinking agent was investigated. Curing of samples was initiated under UV irradiation. Benzoin was used as photoinitiator because it contains chromophore group that could absorb UV irradiation. Ethylene glycol dimethacrylate (EGDMA) was used as crosslinking agent, since it has alkene functional groups that could react with the alkene group of SIS. ATR-FTIR spectra of samples show that absorption band of double bond at 1500–1600?cm^?1 decreases after UV exposure. Increasing the concentration of benzoin (0.1–1?phr) and EGDMA (1–10?phr) leads to an increase in gel content and hardness, while swelling ratio decreases. After 5?min heating at 150?°C, about 20%wt of the unirradiated compound became insoluble, because heating of compound at 150?°C causes crosslinking reaction without any irradiation.     

Crosslinked Sulfonated Polysulfone-Based Polymer Electrolyte Membranes Induced by Gamma Ray Irradiation

Sulfonated aromatic polymers generally show high swelling at high proton conductivity. This disadvantage makes many of them unfit for proton exchange membrane applications. Crosslinking of the polymer is one way to overcome this problem. In this study, radiation-induced crosslinking was performed on a sulfonated polysulfone membrane, with doses ranging from 2.5 to 25.0 kGy (dose rate: 45 Gy/min) using gamma rays from a ⁶⁰Co source. The pristine sulfonated polysulfones was obtained by mild sulfonation of bisphenol-A-polysulfone with trimethylsilyl chlorosulfonate as sulfonating agent. The proton conductivity of the membranes was characterized by means of electrical impedance spectroscopy techniques. Ion-exchange capacity, degree of sulfonation, water content and chemical stability membrane properties were characterized before and after irradiation. The results show that the mechanical, chemical and thermal stability of the membrane improve after irradiation. The degree of sulfonation and the proton conductivity exhibit a tendency to decrease with increasing irradiation total dose.     

Preparation of superabsorbent polymers by crosslinking acrylic acid and acrylamide copolymers

High water-absorbent copolymers comprising acrylic acid (AA) and acrylamide (AM) were prepared in the presence of a crosslinking agent, monofunctional aldehyde, by a solution polymerization technique using a redox initiation system. Such copolymers have very high water absorbency and absorbing kinetics to the distilled water. The copolymer formed which absorbed about 900 g water/g dry copolymer was used to study the influence of sodium chloride on the absorption capacity at 24°C. The swelling of this copolymer was studied in alcohol/water mixtures of increasing alcohol content at 294, 304, and 314 K. The main transition for ethanol/water and methanol/water mixtures is a rapid decrease of the retention capacity of the copolymer at 50–60 vol % ethanol and 55–65 vol % methanol, respectively. Swelling in distilled water at different temperatures (T) and the effect of solvent composition were also studied. Among the variables examined were initiator concentration, polymerization temperature, and amount of AM in the copolymer. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1345–1353, 1997     

Formulation design,optimization, characterization and swelling behaviour of a cationic superabsorbent based on a copolymer of [3‐(methacryloylamino)propyl]trimethylammonium chloride and acrylamide

A series of crosslinked copolymers with cationic nature have been prepared based on acrylamide (AAm) and [3‐(methacryloylamino)propyl]trimethyl ammonium chloride (MAPTAC) using N,N′ methylene‐bis‐acrylamide (MBA) as crosslinking agent. Taguchi's method has been employed for the purpose of formulation design and optimization as well as investigating the effects of various compositional parameters, such as total monomer concentration, cationic monomer and crosslinking agent concentration. The swelling behaviour of the synthesized gels in electrolyte solutions composed of ions with different valency has been studied and compared with an anionic‐based superabsorbent. The swelling capacity and absorbency were found to be enhanced with increase of the MAPTAC moieties of the copolymer chains, and therefore increase of their cationic character. All the cationic hydrogels prepared had greater swelling capacity, with less change in their swelling behaviour, when immersed into aqueous solutions containing multivalent cations. The anionic‐based hydrogels collapsed in similar ionic solutions with moderate‐to‐high ionic strength and did not show any tendency to re‐swell. The complex modulus (G*) of the crosslinked copolymers in the equilibrium swollen state was measured by rheomechanical spectroscopy and was correlated with the chemical composition of the network. Thermogravimetric analysis of the dry cationic superabsorbent showed more bound water but similar thermal behaviour to crosslinked polyacrylamide Copyright © 2003 Society of Chemical Industry     

Utilization of wastes of foam polystyrene as sorbents

Wastes of foam polystyrene were dissolved in styrene and copolymerized with DVB and the final product was sulfonated with H₂SO₄ (group B). Group A of cross-linked polystyrene was synthesized using styrene and divinylbenzene (DVB) in the presence of n-heptane (macroporous ion exchangers) and then was sulfonated with H₂SO₄. The chemical structure of the cross-linked polymers before and after sulfonation was determined by infrared spectroscopy. The ion-exchange capacity was higher for the polymers of group A. The poresize distribution for polymers of group A was determined and the average pore diameter (4V/A) of 39.9 nm for a representative polymer resulted. The degree of swelling of the polymers and their adsorption for methylene blue and alizarin yellow were also determined. The degree of swelling in toluene is decreased by increasing the ratio of DVB in the initial mixture and by sulfonation. The adsorption of methylene blue and alizarin yellow is strongly increased by the sulfonated polymers in comparison with the unsulfonated. As far as group B is concerned, the adsorption of alizarin yellow on the sulfonated polymers, which have higher cross-linking and lower sulfonation, increased more, especially at the initial time. The networks of both groups examined are different. The polystyrene wastes were incorporated into the whole network to an extent of 15–35%. Such investigations could contribute to the utilization of wastes of polystyrene in the direction of sorbents and especially if the polystrene wastes are contaminated with other polymers. © 1995 John Wiley & Sons, Inc.     

Synthesis and swelling properties of grafting‐type and crosslinking‐type water‐swellable elastomers

A grafting water‐swellable elastomer (WSE) that is, chlorinated polyethylene (CPE)‐graft‐poly(ethylene glycol) (PEG), was synthesized by a grafting reaction. The synthesis was based on the reaction between chlorine in CPE and sodium salt of PEG. PEG with molecular weights of 600 and 1000 were used. The maximum grafting percentage of the resulted copolymers after purification was 9.79%. The structure of the copolymer was confirmed by an IR spectrum. The grafting degree and PEG content increased with increasing reaction time and reaction temperature. The equilibrium swelling degree of the grafting copolymer was very small, only 16.94%. However, for the crosslinking WSE, the swelling degree was influenced by the absorbency temperature and absorbency time. The absorbency rate was faster than that of the grafting WSE, and the swelling degree in the equilibrium state was higher than that of the grafting WSE, too. The maximum swelling degree of the crosslinking WSE was 70%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2637–2642, 2007     

Synthesis of strong acid resins from macroporous styrene–divinylbenzene copolymers: Is diluent extraction step necessary?

Strong acidic cation‐exchange resins derived from the same batch of styrene–divinylbenzene copolymers with and without acetone washing are compared with respect to ion‐exchange capacity and leachable organics. The capacity was the same throughout 10 cycles of resin exhaustion and regeneration. Ultraviolet spectra showed the same level of leachable organics in the two cases compared. Fourier transform infrared spectra were also similar. The results are explained on the basis of the fact that n‐heptane and toluene used as diluents were removed through a steam distillation phenomenon during the copolymer curing step. Residual homopolymers were washed away with water after the sulfonation of the copolymers just like acetone washing of them from the copolymer. Acetone washing, which accounts for about 80% of the cost of the chemicals in the copolymer synthesis, can be eliminated in the case of diluents such as n‐heptane and toluene, making the process simple, economical, and environment friendly. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Network characterization and swelling behavior of chemical hydrogels based on acid‐containing poly(vinyl alcohol)

Poly(vinyl alcohol) (PVA) was modified with phthalic and succinic anhydrides to give vinyl alcohol–vinyl ester copolymers that contain carboxylate groups. These half‐esters were then crosslinked by using the poly‐ (ethylene glycol) (PEG) 400 diglycidylether. Low crosslinker/carboxylate ratios were used to obtain low degrees of crosslinking, so the capacity of the resulting hydrogel to absorb water was high. Water absorption was determined gravimetrically as a function of time at room temperature. The equilibrium swelling ratio and compressive modulus were characterized for all the resulting PVA hydrogels and related to the network structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3026–3031, 2003     

On factors determining the swelling ability of crosslinked polymers

Macronet isoporous styrene polymers were obtained by a cross-linking process (using monochlorodimethyl ether as the cross-linking agent) applied to both dissolved linear polystyrene and swollen styrene copolymers with 0.3–1.0% divinylbenzene at the same polymer-solvent weight ratio for all the systems. The lower equilibrium swelling capacity of copolymer-based three-dimensional structures as compared to that of linear polystyrene cross-linked to an equal extent is explained by the presence in the initial swollen styrenedivinylbenzene copolymers of internal strains inhibiting an increase in the volume of the final polymer network. Cross-linking of the linear polystyrene by means of a partially chloromethylated polystyrene shows that irregularity in the distribution of cross-linking bridges enhances the equilibrium swelling capacity of the final gels.     

Proton conductive reinforced poly(ethylene‐co‐styrene) membranes

Polymers with ionic conductivity are useful materials for ion exchange membranes, separators, and electrolytes in electrochemical cells. New ionomers are currently being sought to replace the ionomers, which contain fluorine and are harmful to environment and expensive. A new and promising ionomer is a sulfonated ethylene/styrene copolymer. A nearby alternating copolymer with styrene content of 47 mol % was polymerized with metallocene/MAO catalyst. Membranes were prepared by hot‐pressing copolymer films with a glassfiber tissue. Phenyl rings in the copolymers were sulfonated with chlorosulfonic acid as a sulfonating agent. As the alternating structure of the copolymer, sulfonic groups were evenly distributed along the membranes. The membranes were characterized by determining water uptake, ion exchange capacity, proton conductivity, and mechanical properties. The studies revealed that the sulfonated copolymers have promising properties for proton‐conducting applications. All membranes had good ion exchange capacity, ～ 3.5 meq/g, and proton conductivity, over 50 mS/cm. Due to the high water uptake of the sulfonated copolymer, mechanical properties of the membranes were improved by using the glassfiber tissue as reinforcement. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Thermal stability of proton exchange membranes prepared by grafting of styrene into pre-irradiated FEP films and the effect of crosslinking

The thermal stability of crosslinked ion exchange membranes, prepared by pre-irradiation grafting of styrene into FEP films in the presence of divinylbenzene (DVB) as a crosslinker and subsequent sulfonation of the grafted films, was investigated by thermogravimetry. The formation of different fragments with increasing temperature was monitored by FTIR. Pre-irradiation leads to destabilization of the FEP backbone, showing both earlier depolymerization and substantial redistribution of monomer formation between the two main degradation steps. The presence of DVB had clear effects on the thermal degradation pattern of the sulfonated graft copolymer membrane. Desulfonation occurred at a lower temperature whereas dearomatization was observed to shift to higher temperatures.