Polymer Gels and Networks最新文献

{"title":"Gel formation of polyacrylamide in the presence of glyoxal for water control application","authors":"Ming Han ,&nbsp;Guy Muller ,&nbsp;Alain Zaitoun","doi":"10.1016/S0966-7822(97)00017-8","DOIUrl":"https://doi.org/10.1016/S0966-7822(97)00017-8","url":null,"abstract":"<div><p><span><span>A gel system based on non-hydrolysed polyacrylamide<span> and glyoxal was developed for water control application in petroleum industry. The phase diagram at 40°C was established, which showed a stable gel region. The boundary polymer concentration for </span></span>gelation was around the overlap concentration </span><span><math><mtext>C</mtext><msup><mi></mi><mn>∗</mn></msup></math></span>. The kinetics of gelation were investigated by means of viscoelasticity measurement (storage modulus <em>G</em><span>′). The gelation was more rapid with increasing temperature. The apparent activation energy Δ</span><em>E</em>_a was about 70<!--> <!-->kJ/mol. Also, the gelation was accelerated by OH^- and the mechanism of two-step reaction was proposed.</p></div>","PeriodicalId":20331,"journal":{"name":"Polymer Gels and Networks","volume":"5 6","pages":"Pages 471-480"},"PeriodicalIF":0.0,"publicationDate":"1998-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0966-7822(97)00017-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72252192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A method for studying swelling kinetics based on measurement of electrical conductivity","authors":"Matthew J. Lesho ,&nbsp;Norman F. Sheppard Jr","doi":"10.1016/S0966-7822(97)00024-5","DOIUrl":"https://doi.org/10.1016/S0966-7822(97)00024-5","url":null,"abstract":"<div><p>A novel method was applied to the study of swelling kinetics of pH-responsive hydrogels. This technique is based on the pH-dependent electrical conductivity of these materials, which is measured by coating planar interdigitated electrode arrays with thin hydrogel membranes. To demonstrate the utility of the method, the swelling kinetics of a well-characterized pH-responsive hydrogel were studied. Cross–linked copolymers of 2-hydroxyethyl methacrylate (HEMA) with up to 20 mol% dimethylaminoethyl methacrylate (DMA) were studied as a function of copolymer composition in phosphate or triethanolamine buffer at buffer concentrations from 1 to 100 mM. The experiments consisted of measuring the change in electrical resistance of a hydrogel-coated electrode array following a small pH change in the external buffer medium. The characteristic response time to reach a new equilibrium following a pH change was proportional to the concentration of DMA within the polymer and was inversely proportional to the buffer concentration. The characteristic response times for devices tested in phosphate buffer were a function of the magnitude of the pH step, increasing from 2.6 to 5.6 min as the step size increased from 0.2 to 0.57 pH units. However, the response times for devices tested in triethanolamine were independent of step size. The observed dependences upon the values of the dissociation constant (p<em>K</em>_a) of the buffering ion, the apparent p<em>K</em>_a of DMA, and the pH of the external bath agreed with buffer-mediated diffusion–reaction theory, and as such this conductimetric method represents a powerful tool for the study of swelling kinetics of responsive hydrogels.</p></div>","PeriodicalId":20331,"journal":{"name":"Polymer Gels and Networks","volume":"5 6","pages":"Pages 503-523"},"PeriodicalIF":0.0,"publicationDate":"1998-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0966-7822(97)00024-5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72252193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Force relaxation of single spherical gel beads under compression","authors":"A. Knaebel ,&nbsp;F. Lequeux","doi":"10.1016/S0966-7822(97)00025-7","DOIUrl":"10.1016/S0966-7822(97)00025-7","url":null,"abstract":"<div><p>A spherical bead, when submitted to an uniaxial compression between two parallel pistons, exhibits solvent migration effects both inside and outside the gel. We describe here some experiments of force relaxation on a strained bead, at different swelling ratio. We present a theoretical description that allows to determine the shear and the compression modulus, and the critical force one has to apply in order to deswell a bead which is swollen below its equilibrium ratio. We also show that mechanical tests do not allow for a direct observation of the deswelling force.</p></div>","PeriodicalId":20331,"journal":{"name":"Polymer Gels and Networks","volume":"5 6","pages":"Pages 577-584"},"PeriodicalIF":0.0,"publicationDate":"1998-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0966-7822(97)00025-7","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77358467","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Swelling equilibria and volume phase transition of polyelectrolyte gel with strongly dissociated groups","authors":"Jadranka Travas-Sejdic ,&nbsp;Allan Easteal","doi":"10.1016/S0966-7822(97)00019-1","DOIUrl":"https://doi.org/10.1016/S0966-7822(97)00019-1","url":null,"abstract":"<div><p>The peculiarities of the swelling equilibrium and volume phase transition of polyelectrolyte<span><span> copolymer gels consisting of acrylamide and 2-acrylamido-2-methyl-1-propane </span>sulphonic acid<span> (AAm/AMPS) have been studied as a function of copolymer composition and gel structure. Equilibrium swelling for AAm/AMPS gels in buffer solutions, pure water and aqueous salt (NaCl) solutions were investigated. The swelling curves were calculated using the Hasa–Ilavský–Dušek theory and obtained experimentally. The agreement is reasonably good, and the HID theory can be used to estimate the swelling and structural parameter of AAm/AMPS gels. The volume phase transition has been generated by changing the solvent composition by progressive substitution of water by acetone. The critical interaction parameter corresponding to collapse depends strongly on the composition of the gel, since the extent of collapse is determined by composition and cross-link density of the gel.</span></span></p></div>","PeriodicalId":20331,"journal":{"name":"Polymer Gels and Networks","volume":"5 6","pages":"Pages 481-502"},"PeriodicalIF":0.0,"publicationDate":"1998-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0966-7822(97)00019-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72252191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Networks based on chitosan and oxidized cyclodextrin—II. Structural and catalytic features of a copper (II)-loaded network","authors":"Gaio Paradossi ,&nbsp;Ester Chiessi ,&nbsp;Francesca Cavalieri ,&nbsp;Danila Moscone ,&nbsp;Vittorio Crescenzi","doi":"10.1016/S0966-7822(97)00026-9","DOIUrl":"https://doi.org/10.1016/S0966-7822(97)00026-9","url":null,"abstract":"<div><p>Chitosan is well known for its binding properties toward transition metal ions. We prepared a chemical hydrogel based on chitosan using as cross-linking agent a polyfunctionalized <em>β</em><span><span><span>-cyclodextrin and studied the structural and catalytic features of this hydrogel loaded with copper(II) ions in aqueous medium. Stability of the complex and its structural characteristics were determined by </span>isothermal </span>microcalorimetry and EPR spectroscopy, respectively. Kinetics of the oxidation of (</span><span>d</span>, <span>l</span>)-adrenaline and of <span>l</span>-adrenaline catalyzed by copper (II) bound to the matrix was monitored with a Clark-type <em>O</em>^-₂<span> sensitive electrode. The advantages of working with a heterogeneous system are coupled with the preservation of both structural and catalytic features of copper(II) site in the matrix with respect to copper(II) ions bound to chitosan derivatives in solution.</span></p></div>","PeriodicalId":20331,"journal":{"name":"Polymer Gels and Networks","volume":"5 6","pages":"Pages 525-540"},"PeriodicalIF":0.0,"publicationDate":"1998-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0966-7822(97)00026-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72252194","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Kinetics of polyelectrolyte network swelling and collapse: Effect of ion association–dissociation","authors":"V. Vasilevskaya, L. V. Men'shikova","doi":"10.1016/S0966-7822(98)00008-2","DOIUrl":"https://doi.org/10.1016/S0966-7822(98)00008-2","url":null,"abstract":"","PeriodicalId":20331,"journal":{"name":"Polymer Gels and Networks","volume":"37 1","pages":"149-161"},"PeriodicalIF":0.0,"publicationDate":"1998-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76210284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gelation kinetics of scleraldehyde–chitosan co-gels","authors":"Bo Guo ,&nbsp;Arnljot Elgsaeter ,&nbsp;Bjørn T. Stokke","doi":"10.1016/S0966-7822(98)00005-7","DOIUrl":"10.1016/S0966-7822(98)00005-7","url":null,"abstract":"<div><p><span>The gelation<span> kinetics of modified scleroglucan carrying various fractions of reactive aldehyde groups in the side-chains, scleraldehyde, and chitosan was determined using oscillatory shear rheometry<span> to study the dynamic viscoelastic properties as a function of reaction time. The experimentally determined initial increase in the storage modulus per unit time, Δ</span></span></span><em>G</em>′/Δ<em>t</em>, for various scleraldehyde concentrations, <em>C</em>_Sc, degree of aldehyde substitution of scleraldehyde, <em>D</em>_Ald, and chitosan concentrations, <em>C</em>_Chi<span>, revealed the existence of a lower critical concentration for gelation for both the two polysaccharides, </span><em>C</em>_Sc,0 and <em>C</em>_Chi,0. The obs erved power law coefficients <em>m</em> and <em>n</em>, Δ<em>G</em>′/Δ<em>t</em>∼(<em>D</em>_Ald<em>C</em>_Sc)^<em>m</em><em>C</em>^<em>n</em>_Chi, were both significantly larger than one in the employed relative concentrations ranges <em>C</em>_Sc/<em>C</em>_Sc,0∈(1–20) and <em>C</em>_Chi/<em>C</em>_Chi,0∈(1–10), which was accounted for by the total wastage reactions and network statistics. The rate of gel formation showed a maximum near pH 7 due to a delicate balance among several competing effects: (1) The free-amine concentration of the chitosan increases in the pH range 4.5–6.5 (p<em>K</em>_a<span> of the amino group), (2) the Schiff-base junction formation is acid catalyzed, and (3) the solubility of chitosan decreases when the pH exceeds 7. The increased aggregation resulting from increasing the pH from 7 to 7.6 yielded an increasing fraction of reactive groups involved in wastage reactions, yielding an increase both in </span><em>C</em>_Chi,0 and the power law coefficient <em>n</em> from 1.7 to 2.6. The temperature dependence of Δ<em>G</em>′/Δ<em>t</em><span> could be accounted for by incorporating an apparent activation energy </span><em>E</em>_a=43<!--> <!-->kJ<!--> <!-->mol^-1. The temperature dependence of <em>G</em>′ of the fully cured scleraldehyde–chitosan co-gels was found to give rise to a shift from Δ<em>G</em>′/Δ<em>T</em>&gt;0<!--> <!-->Pa/min to Δ<em>G</em>′/Δ<em>T</em>&lt;0<!--> <!-->Pa/min, when the crosslink density increased. This suggests a change from entropy dominated elasticity at low crosslink density, to an enthalpy dominated elasticity when this density increases, possibly due to decreasing length of the elastically active chains.</p></div>","PeriodicalId":20331,"journal":{"name":"Polymer Gels and Networks","volume":"6 2","pages":"Pages 113-135"},"PeriodicalIF":0.0,"publicationDate":"1998-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0966-7822(98)00005-7","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76512798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Phase transition in swollen gels 24","authors":"Z. Sedláková ,&nbsp;K Bouchal ,&nbsp;M. Ilavský","doi":"10.1016/S0966-7822(98)00009-4","DOIUrl":"10.1016/S0966-7822(98)00009-4","url":null,"abstract":"<div><p><span>The swelling and mechanical behaviour of ionized networks of copolymers<span> of acrylamide (AAm), methylenebisacrylamide and sodium 2-[(3-carboxypyridine-4-carbonyl)oxy]ethyl methacrylate (PyNa, molar fraction of salt </span></span><em>x</em>_S=0–0.20) was investigated in water–acetone (w/a) mixtures and in aqueous NaCl solutions. In the range <span><math><mtext>x</mtext><msub><mi></mi><mn><mtext>S</mtext></mn></msub><mspace></mspace><mtext>⩾0.01</mtext></math></span>, a first-order phase transition (collapse) was found in w/a mixtures; with increasing <em>x</em>_S, both the critical acetone concentration <em>a</em>_c in the mixture at which collapse takes place and the extent of collapse (jump in the swelling ratio <em>X</em>), <span><math><mtext>Δ</mtext><mtext>log</mtext><mspace></mspace><mtext>X</mtext></math></span>, increases. A comparison of these results with the results obtained for charged PAAm networks with sodium 2-[(2-carboxybenzoyl)oxy]ethyl methacrylate (BeNa) as ionic comonomer led to a conclusion that substituting benzoyl for pyridyl groups in the side chain slightly decreases <span><math><mtext>Δ</mtext><mtext>log</mtext><mspace></mspace><mtext>X</mtext></math></span> and the swelling degree in water, and does not change critical <em>a</em>_c values. On the other hand, a comparison with charged PAAm networks with sodium methacrylate (MNa) as ionic comonomer showed that at constant <em>x</em>_S, the swelling degree in water, the extent of collapse <span><math><mtext>Δ</mtext><mtext>log</mtext><mspace></mspace><mtext>X</mtext></math></span> and the concentration of elastically active network chains strongly decreased with the increased distance of the bound charge from the main chain (length of the side chain of the ionic comonomer). The expected decrease in the swelling degree of ionized networks with increasing NaCl concentration was found. The experimental swelling data in w/a mixtures and in aqueous NaCl solutions could be described by a theory proposed previously if an effective degree of ionization <em>i</em> is introduced (<em>i</em>&lt;<em>x</em>_S<span>). The mechanical behaviour of gels in w/a mixtures is predominantly determined by the degree of swelling. On the other hand, different dependencies of the reduced modulus on the swelling ratio </span><em>X</em> found in w/a mixtures and in aqueous NaCl solutions in the high swelling region suggests that contracted gels with different microstructure were formed during gel deswelling in bad solvents or salt in water.</p></div>","PeriodicalId":20331,"journal":{"name":"Polymer Gels and Networks","volume":"6 2","pages":"Pages 163-178"},"PeriodicalIF":0.0,"publicationDate":"1998-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0966-7822(98)00009-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87695506","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Kinetics of polyelectrolyte network swelling and collapse","authors":"Valentina V. Vasilevskaya ,&nbsp;Larisa V. Men’shikova","doi":"10.1016/S0966-7822(98)00008-2","DOIUrl":"https://doi.org/10.1016/S0966-7822(98)00008-2","url":null,"abstract":"<div><p><span>A theory of kinetics of swelling and collapse of a polyelectrolyte network is proposed. In addition to the conventional </span>kinetic equation<span><span> for polyelectrolyte network swelling, the variation of the concentration of freely moving counter ions in the course of network swelling due to the dissociation–association reaction is taken into account. The three regimes of collapse of a polyelectrolyte network are distinguished. The first regime is slow deswelling which proceeds at an almost constant rate. The second is the short-term regime of fast deswelling at an extremely high rate. In the third regime, the collapse of the polymer network occurs at an almost constant rate, which is even lower than the rate of initial deswelling. Under some conditions the swelling/deswelling of a polyelectrolyte network exhibits </span>hysteresis, when the collapse of a polymer network to the globule state occurs at a better solvent quality than the globule–coil transition.</span></p></div>","PeriodicalId":20331,"journal":{"name":"Polymer Gels and Networks","volume":"6 2","pages":"Pages 149-161"},"PeriodicalIF":0.0,"publicationDate":"1998-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0966-7822(98)00008-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92002861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sorption behaviour of interpenetrating polymer networks based on polyurethane and unsaturated polyester","authors":"S. Ajithkumar ,&nbsp;N.K Patel ,&nbsp;S.S. Kansara","doi":"10.1016/S0966-7822(98)00006-9","DOIUrl":"10.1016/S0966-7822(98)00006-9","url":null,"abstract":"<div><p><span><span><span><span>Kinetics of swelling and sorption behaviour of </span>interpenetrating polymer networks (IPNs) based on castor-oil-based </span>polyurethanes (PU) and unsaturated polyester (UPE) in chlorobenzene has been studied at 25°C. IPNs having different weight composition of PU and UPE and also having various crosslink density (NCO/OH ratio) were employed. Effect of hydroxyl number (molecular weight) of polyols on the sorption behaviour has also been investigated. All the results obtained were compared with that of the </span>homopolymer<span> networks. Studies revealed that the sorption is anomalous in nature in all the samples. Diffusion coefficient is found to increase with both increase in NCO/OH ratio and PE content in the IPNs, whereas sorption coefficient shows a reverse trend. The swelling results have been used to calculate the molecular weight between two crosslinks (</span></span><span><math><mtext>M</mtext><mtext>̄</mtext><msub><mi></mi><mn><mtext>c</mtext></mn></msub></math></span>) and hence the number of chains per unit volume (<em>N</em>) and degree of crosslinking (<em>ν</em>) in all the samples studied.</p></div>","PeriodicalId":20331,"journal":{"name":"Polymer Gels and Networks","volume":"6 2","pages":"Pages 137-147"},"PeriodicalIF":0.0,"publicationDate":"1998-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0966-7822(98)00006-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89380777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}