Synthesis and swelling behavior of crosslinked copolymers of neutralized maleic anhydride with other monomers

A series of novel copolymer superabsorbents based on maleic anhydride (MLN), acrylamide (AAM), hydroxyethyl methacrylate (HEMA), and N,N′‐methylenebisacrylamide (NMBA) were prepared by inverse‐suspension polymerization. The influence of the reaction parameters on the water absorption was investigated to improve the understanding and to identify the optimum reaction conditions. The water absorbences or swelling behaviors for these absorbents in various salt solutions and various alcohol solutions were studied. The tendency of the absorbency for these absorbents in salt and alcohol solutions is in the order Na⁺ > Ca²⁺ > Al³⁺ for NaCl, CaCl₂, and AlCl₃ aqueous solutions and a glycerol > glycol > methanol > ethanol solution, respectively. This article also explains the IR and SEM characterization of the water‐absorbing copolymers and their practical use in soil for water retention. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 12: 2725–2731, 2003     

Porosity variation and swelling of styrene-divinylbenzene copolymers

Summary The porosity measured for two series of diluent-modified styrene (S) — divinylbenzene (DVB) copolymers (10 and 20 wt.-% of DVB) was found to depend on sample pre-treatment. A correlation between the volume fraction of the polymer in the swollen gel and the volume fraction of octane used as diluent has been established assuming the isotropic swelling of the sample pretreated with water before porosity determination.     

Elastic and swelling behavior of 2-hydroxyethyl methacrylate,diethylene glycol methacrylate,and methacrylic acid copolymers

The elastic and swelling behavior of copolymers of 2-hydroxyethyl methacrylate, diethylene glycol methacrylate, and methacrylic acid crosslinked with ethylene glycol dimethacrylate has been studied. In the range of copolymer composition studied, Young's modulus of the swollen networks increases with the content of methacrylic acid, and its dependence on the content of diethylene glycol methacrylate passes through a maximum. The concentrations of the elastic network chains and determined from Young's moduli of swollen networks are much higher than those calculated from stoichiometry. This effect is attributed to the presence of additional physical crosslinks due to water-induced ordering of the hydrophobic backbone chains. Both the elastic and swelling behavior of the polymers mentioned above are decisive for their application in the preparation of soft contact lenses. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2141–2148, 1997     

Effects of gamma radiation on the dynamic mechanical and swelling behavior of styrene butadiene block and random copolymers

The physical structure of a number of styrene-butadiene copolymers were investigated via dynamic mechanical and swelling studies on uncrosslinked and gamma-radiation cross-linked films that had initially been solvent cast from toluene or methyl ethyl ketone. The mechanical behavior of these films before and after crosslinking was found to depend on the material history as well as the chemical structure of the copolymer, in agreement with observations made by other experimental techniques. A simple morphological interpretation was given to the dynamic mechanical spectra as a function of radiation dosage and a limited discussion of the swelling behavior is included.     

EQCM研究邻氨基苯甲酸/苯胺的共聚膜的溶胀/溶解行为

本文采用电化学石英微天平（EQCM）研究了现场监测了摩尔比不同的邻氨基苯甲酸／苯胺混合溶液的共聚膜在不同pH值B—R缓冲溶液中的不同性质和过程。发现溶液中邻氨基苯甲酸的含量和溶液的PH值对苯胺／邻氨基苯甲酸的共聚膜的溶胀／溶解行为均具有很大的影响。     

Effect of triblock copolymers on homogeneity,mechanical properties and swelling behavior of IIR/SBR rubber blends

The present research concerns with the preparation and characterization of isobutylene isoprene/butadiene–styrene rubber (IIR/SBR) blends with different blend ratios, in the presence and absence of styrene–isoprene–styrene (SIS) and styrene–isobutylene–styrene (SiBS) triblock copolymers to be tested as compatibilizers. Effect of the triblock copolymers on the blend homogeneity was investigated with the aid of scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) measurements. Characterization of the rubber blends was conducted by measuring the physico-mechanical properties after and before thermal aging, in presence and absence of the triblock copolymers. In addition, weight swell % in toluene, motor oil and brake fluid of the rubber blend vulcanizates was assessed. The incorporation of SIS and SiBS triblock copolymers improved the homogeneity of IIR/SBR blends as well as increased both tensile strength and elongation at break of the rubber blend vulcanizates. Of the entire blend ratios examined, IIR/SBR (25/75) blend containing SIS compatibilizer possessed the best physico-mechanical properties (12.6 MPa tensile strength and 425 % elongation at break) and (14 MPa tensile strength and 555 % elongation at break) after and before thermal aging, respectively. Utilization of SIS and SiBS triblock copolymers enhanced the thermal stability of IIR/SBR blend vulcanizates. Moreover, IIR/SBR blends of different blend ratios showed superior swelling resistance in the brake fluid. IIR/SBR (25/75) blend containing SIS compatibilizer and cured with CBS/ZDEC/S vulcanizing system possessed the best physico-mechanical properties (14.4 MPa tensile strength and 440 % elongation at break) and (16.5 MPa tensile strength and 610 % elongation at break) after and before thermal aging, respectively.     

Block copolymers by combinations of cationic and radical routes

Summary A new method is described for the production of macroporous beads by copolymerization of styrene and divinylbenzene initiated by azo linked polytetrahydrofuran, which was obtained by silver salt-diacid chloride technique. Swelling properties of the beads in various solvents were studied.     

Deformational,swelling, and potentiometric behavior of ionized gels of 2-hydroxyethyl methacrylate–methacrylic acid copolymers

The deformational, swelling, and potentiometric behavior of ionized water-swollen gels of 2-hydroxyethyl methacrylate (HEMA)–methacrylic acid (MA) copolymers used in biomedical and separation applications was investigated. With increasing degrees of neutralization α, the swelling degree strongly increases and the modulus G_s decreases. For the copolymers with MA content ? 30 mole-%, the dependence of G_s on α passes through a minimum. Comparison of the results with the modified theory of rubber elasticity shows that the decrease in G_s at low concentrations of charges on the chain is controlled mainly by the degree of swelling. At higher α, both the finite extensibility of network chains, caused by a high degree of swelling, and electrostatic interactions contribute to G_s. The dependence of the interaction parameter χ on the volume fraction of polymer in the gel, v₂, is independent of α and closely resembles the dependence obtained for other hydrophilic polymers.     

Chemical modification of acrylonitrile copolymers: Reaction of cationic copolymers with ethylene oxide

Copolymers of tertiary amines have been reacted with ethylene oxides gas. The reaction induces low temperature cyclization and increases polymer hydrophilicity. When the co-polymer is in film form, water permeability is dependent on ethylene oxide processing time and temperature. The behavior of the copolymer films when treated with ethylene oxide is contrasted with the effects due to thermal treatment of acrylonitrile copolymers.     

Swelling characteristics of NR/PU block copolymers and the effect of NCO/OH ratio on swelling behaviour

A series of (NR/PU) block copolymers (BCs) was prepared from toluene diisocyanate (TDI), 1,3-butane diol (1,3-BDO), and hydroxyl-terminated liquid natural rubber (HTNR), by solution polymerisation. The swelling characteristics of the BCs were investigated. Diffusion profile in various solvents and the sorption kinetics were studied. Arrhenius and thermodynamic parameters were evaluated from the diffusion data. Finally, the influence of NCO/OH ratio on the swelling behaviour was also studied. The equilibrium sorption value (Q_∞) decreased with increasing NCO/OH ratio for all the BCs. The samples have higher uptake of solvents with solubility parameter within a small range centred about 9 (cal/cm³)^1/2. Highly polar and non-polar solvents show minimum uptake. It was observed that polarity factor predominates in the solvent transport through the present block copolymer systems. The sorption behavior is also found to vary with the NCO/OH ratio employed in the preparation of polyurethane (PU) oligomers.     

13C NMR spectroscopy of cationic copolymers of acrylamide

Summary Random copolymers of acrylamide and a quaternary ammonium acrylate monomer have been investigated by¹³C NMR spectroscopy in aqueous solution. Cleavage of the ester function has been shown to occur in mild alkaline media with a simultaneous intrachain reaction giving imide group formation. Sequential length distribution of the comonomers has been analyzed from triads composition and the experimental results lead to a nearly Bernouillian statistics although a more alternating distribution would be predicted from the reactivity ratios. This fact has been attribtued to the compositional heterogeneity of our copolymers which have been prepared at high degree of conversion.     

Melting behavior of polyacrylonitrile copolymers

Summary The melting behavior of acrylonitrile copolymers, ter- and tetrapolymers was studied in the dry state and in the presence of water. The melting point depression caused by the incorporation of a specific comonomer into the polyacrylonitrile chain was shown to be dependent on the molecular structure of the comonomer. Not all comonomers gave equivalent melting point depressions on a molar basis. The Eby theory of comonomer melting was used to model the melting behavior. This theory assumes that the non-crystallizing (non-AN) comonomers enter the crystal lattice as point defects rather than being relegated to the amorphous phase. An equation was developed for predicting the melting point of copolymers, terpolymers and higher order polymers as a function of the polymer composition and the specific melting point depression constant for each comonomer. The latter constants are derived from the copolymer melting point curves. The equation is applicable to both dry and wet polymers and excellent agreement between the observed and calculated melting points for wet terpolymers and tetrapolymers was observed.     

Synthesis of hybrid liquid crystalline block copolymers by combination of cationic or promoted cationic and free-radical polymerizations

Summary The synthesis of two new classes of liquid crystalline block copolymers (1–5) by a two-step combination of cationic and free-radical polymerizations is described. An azomacroinitiator was prepared first by cationic polymerization of tetrahydrofuran or promoted cationic polymerization of cyclohexene oxide, which was then used to initiate the free-radical polymerization of an acrylate monomer containing a variously substituted biphenyl mesogenic group. The semicrystalline and liquid crystalline blocks were essentially microphase-separated and gave rise to different thermotropic mesophases.     

Surface characteristics of water‐soluble cationic fluoro copolymers containing perfluoroalkyl,quaternized amino,and hydroxyl groups

Various water‐soluble cationic fluoro copolymers in quaternized form with perfluoroalkyl, amino, and hydroxyl groups were prepared by varying the contents of perfluoroalkyl ethyl acrylate (FA), 2‐(dimethylamino) ethyl methacrylate (DAMA), and 2‐hydroxyethyl methacrylate (HEMA). The solvent polymerization was carried out in acetone, with the subsequent addition of acetic acid to form a quaternized polymer. Polyurethanes films were prepared by curing aqueous solutions containing water‐soluble cationic fluoro copolymers and a blocked isocyanate at 190°C. The surface characteristics of the water‐soluble cationic fluoro copolymers and the polyurethanes were investigated on the basis of FA and DAMA contents. The contact angles for both water and methylene iodide (MI) on the cationic fluoro copolymer and the polyurethane increase steadily as FA content increases, and decrease gradually with increasing DAMA content. The contact angles on the polyurethane are slightly higher than those on the cationic fluoro copolymer. The cationic fluoro copolymer and the polyurethane with FA content of 40 wt % and DAMA content of <30 wt % show extremely low surface free energies of 13–15 dynes/cm. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3702–3707, 2002     

Solute and penetrant diffusion in swellable polymers. XI. The dynamic swelling behavior of hydrophilic copolymers containing multiethylene glycol dimethacrylates

Copolymers of 2-hydroxyethyl methacrylate with a number of multiethylene glycol dimethacrylates were prepared by bulk copolymerization in the presence of AIBN s an initiator. The content of the dimethacrylate varied between 30 and 50 mol %. Additional copolymers were prepared by solution polymerization in the presence of water or ethanol. All samples were swollen in water up to thermodynamic equilibrium, and their dynamic swelling behavior was studied as a function of time. It was concluded that the mechanism of water transport in these moderately and highly crosslinked polymers was a coupled relaxation and diffusion and that the relaxational contribution to the overall transport depended on the chain length of the multiethylene glycol dimethacrylate.     

Investigation of the swelling behavior of cationic exchange resins saturated with Na+ ions in a C3S paste

Ion exchange resins (IERs) are widely used by the nuclear industry to decontaminate radioactive effluents. Spent products are usually encapsulated in cementitious materials. However, the solidified waste form can exhibit strong expansion, possibly leading to cracking, if the appropriate binder is not used. In this work, the interactions between cationic resins in the Na⁺ form and tricalcium silicate are investigated during the early stages of hydration in order to gain a better understanding of the expansion process. It is shown that the IERs exhibit a transient swelling of small magnitude due to the decrease in the osmotic pressure of the external solution. This expansion, which occurs just after setting, is sufficient to damage the material which is poorly consolidated for several reasons: low degree of hydration, precipitation of poorly cohesive sodium-bearing C–S–H, and very heterogeneous microstructure with zones of high porosity.     

Cs-AA-HEMA复合水凝胶的合成及溶胀性能

以壳聚糖、丙烯酸、甲基丙烯酸羟乙酯为原料,硝酸铈铵、过氧化二苯甲酰为引发剂,戊二醛为交联剂,制备了壳聚糖-丙烯酸-甲基丙烯酸羟乙酯复合水凝胶,探讨了凝胶溶胀过程和理论,研究了凝胶合成条件及溶剂性质对凝胶平衡溶胀度的影响.结果表明：随着丙烯酸浓度、甲基丙烯酸羟乙酯添加量的增加,凝胶平衡溶胀度先增大再减小,凝胶溶胀度随着戊二醛浓度增加而减小.壳聚糖-丙烯酸-甲基丙烯酸羟乙酯复合水凝胶是pH/离子/温度敏感型凝胶.     

Dyeing behavior of swollen cotton fibers and swelling mechanisms of intra- and intercrystalline swelling agents

Dyeability was used to study the swelling mechanisms of intra- and intermicellar swelling agents on cotton cellulose. Reactive and direct dyes were used for dyeing, and zinc chloride, ethylenediamine (EDA), and morpholine were used for swelling reactions. Changes taking place in the accessible regions as a result of swelling were determined by moisture regain, acid hydrolysis, formylation, and the lateral order distribution in the fiber structure. The results indicate that the intracrystalline swelling agents, viz., zinc chloride and EDA, induce specific changes in the accessible portions of the fiber. The accessible portion produced by the inorganic swelling agent has a more open structure than the disordered region produced by the EDA treatment. The distinctive nature of the accessible portions in swollen cotton fibers treated with the two reagents was reflected in all the properties studied. This was attributed to the different mechanisms of swelling and decrystallization of cotton fibers by zinc chloride and EDA. Morpholine was shown to bring about considerable changes in the accessible portions of the cotton fiber which were responsible for increased dyeability with reactive dyes, and was also shown to increase the amount of “truly” accessible regions by breaking the “imperfect crystals” in the disordered regions as well as on the surface of crystallites.     

Synthesis and association properties of thermoresponsive and permanently cationic charged block copolymers

Atom transfer radical polymerization (ATRP) was used to prepare thermosensitive cationic block copolymers of (3-acrylamidopropyl)-trimethylammonium chloride (AMPTMA) and N-isopropylacrylamide (NIPAAM) with different block lengths. By using ethyl-2-chloropropionate (ECP) as initiator and CuCl/CuCl₂/tris(2-dimethylaminoethyl)amine (Me₆TREN) catalytic system in DMF:water 50:50 (v/v) mixtures at 20 °C the polymerization was controlled. The association properties in NaCl aqueous solution were studied as a function of temperature and polymer concentration by dynamic light scattering, NMR spectroscopy, fluorescence spectroscopy and energy filtered-transmission electron microscopy. The block copolymers formed micellar aggregates above the lower critical solution temperature (LCST) of pNIPAAM. The LCST is strongly influenced by the relative length of the two blocks and is significantly higher than that of pure pNIPAAM. The size of core and shell of the micelles is discussed in terms of block copolymer composition.