Copolymer Gels Research Articles

Karaya gum-graft-poly(2-(dimethylamino)ethyl methacrylate) gel: An efficient adsorbent for removal of ionic dyes from water

In the present study, a novel hydrogel based on the polysaccharide, ‘Karaya gum’ has been synthesised by graft copolymerization and evaluated as an adsorbent for the removal of ionic dyes from aqueous solution. The hydrogel was made by simultaneous grafting and cross linking of Karaya gum using 2-(dimethylamino)ethyl methacrylate (DMAEMA) and N,N′-methylene-bis-acrylamide via microwave irradiation. The graft copolymer gel was characterized by FTIR, TGA, SEM techniques. The swelling of the gel studied in buffer media of varying pH revealed a pH responsive behaviour with a maximum swelling in neutral pH and a minimum swelling at pH 1.2. The temperature dependent swelling study indicated 40 °C as the lowest critical solution temperature. Kinetic studies indicated the swelling to be a second order process with Fickian diffusion as the water transport mechanism. The adsorption studies indicated maximum adsorption capacity of 89.28 and 101.42 mg/g towards methylene blue and indigo carmine respectively. The dye adsorption data is found to fit well with pseudo- second order kinetic model and the Freundlich adsorption isotherm model. The adsorption was found to be a multistep process with surface adsorption followed by intraparticle diffusion. Thermodynamic studies revealed the adsorption of dyes to be spontaneous.

Effect of far-field compliance on local failure dynamics of soft solids

The resistive forces and failure of a soft gel upon large strain indentation with small, spherically-tipped indenters (or puncture mechanics) has been studied previously by Fakhouri et al., (2015). The above work is extended to include the effect of far-field compliance on the critical crack initiation event via puncture in soft acrylic triblock copolymer gels. It is found that critical puncture force, Pc, reduces with increasing far-field compliance, Cs, due to the change in local probe velocity, vg. A power-law relation between Pc and Cs is established and is shown to be valid across a range of global probe velocity, vc, varied over three orders of magnitude. Small-strain mechanical response of the gels characterized via oscillatory shear rheology and large strain response measured from puncture mechanics show rate-independent behavior. Our experiments and analysis provide insight into local rate-dependent failure processes in elastic triblock copolymer gels.

High-power lithium-ion microbatteries from imprinted 3D electrodes of sub-10 nm LiMn2O4/Li4Ti5O12 nanocrystals and a copolymer gel electrolyte

Miniaturized energy-storage components are important to self-powered microelectronics. Microbatteries based on 3D electrode architectures hold great potential to meet the demands of high-power and high energy densities. Despite the progress in microelectrode fabrication, reports of high-performance, fully integrated 3D microbatteries are still limited due to strict material requirements and more importantly, significant hierarchical processing complexities. Here, a 3D lithium-ion microbattery made from solvothermally synthesized sub-10 nm LiMn2O4/Li4Ti5O12 nanocrystals and a novel copolymer gel electrolyte is presented and is shown to possess superior capacity retention (40% at 300 C) and high-power density (855.5 μWcm−2μm−1) comparable to some of the best microsupercapacitors. The customized microelectrodes are fabricated by solvent-assisted imprint lithography of well-dispersed nanoparticle ink and the battery cell is integrated vertically through layer-by-layer (LBL) assembly. The fabrication strategy proposed here can be applied to a variety of electroactive materials. This work provides a combinatorial approach and highlights the synergetic effects of material synthesis, processing and device design for achieving high-performance micropower sources.

Communication: Molecular-level description of constrained chain topologies in multiblock copolymer gel networks.

Network characteristics in physical gels composed of solvated block copolymers varying in molecular design are examined here by dynamic rheology and computer simulations. In two triblock copolymer series, one with chain length (N) varied at constant copolymer composition (f) and the other with f varied at constant N, we discern the dependence of equilibrium network metrics on both N and f. Increasing the block number in a linear multiblock series at constant N and f escalates conformational complexity, which dominates network connectivity classified according to a midblock conformation index.

Dielectric Behavior and Phase Behavior of Block Copolymer PEO13-PPO30-PEO13 Aqueous Solution.

Dielectric spectroscopy can be applied to study the structure and dynamics of block polymer. In this work, dielectric measurements of block copolymer Pluronic L64 solution are carried out in the frequency range between 40 Hz and 110 MHz with variable temperatures and concentrations. We analyze the phase behavior of the PEO13-PPO30-PEO13 (Pluronic L64) aqueous system according to the concentration/temperature-dependence of direct current conductivity. The result indicates the sensitivity of the phase behavior and conductivity of the Pluronic L64 solution to temperature. Besides, two relaxations were observed: relaxation 1 (0.5 MHz) is related to the gelation process, while relaxation 2 (5 MHz) is caused by the interface polarization. On the basis of relaxation 2, the volume fraction and permittivity of the particle were calculated. The formations of the block copolymer micelle and gel are monitored successfully by the temperature/concentration-dependence of the dielectric parameters and the volume fraction.

Controllable Photoluminescent and Nonlinear Optical Properties of Polymerizable Carbon Dots and Their Arbitrary Copolymerized Gel Glasses

AbstractIn this work, an efficient method is developed to prepare silane‐functionalized red‐emissive carbon dots and carbon dots gel glasses with arbitrary loading fraction (0–100%). The as‐prepared materials possess strong photoluminescence and significant third‐order nonlinear optical performances. The optical properties can be tuned by either changing solvents and pH of the solution or adjusting the loading fractions of carbon dots in gel glasses. In particular, the photoluminescence of the carbon dots and their polymerized glasses can be linearly modulated from yellow to red emission by increasing the loading fraction of carbon dots or the polarity of solvent. It is also found that the chemical copolymerization leads to superior optical properties of gel glasses to that of the carbon dots solution, because the copolymerization endows stable immobilization of carbon dots in a rigid matrix. This study provides a feasible method to prepare optoelectronic hybrid materials and devices.

Pectin graft copolymer-montmorillonite composite: Synthesis, swelling and divalent metal ion adsorption

ABSTRACTA novel graft copolymer gel made up of pectin (Pec), 2-(methacryloyloxyethyl)trimethylammonium chloride (METAC), 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) and its composite with montmorillonite (MMT) were prepared using methylenebisacrylamide (MBA) as cross-linker via microwave irradiation and characterized using Fourier transform infrared (FTIR), Thermogravimetric Analysis (TGA) and Scanning electron microscopy (SEM) techniques. Swelling studies were carried out under different pH conditions. The graft copolymer gel and its composite showed maximum swelling in neural medium (pH 7.1) and the swelling process followed second order kinetics. The mechanism of water transport is found to be a Less Fickian diffusion process. The adsorption capacities of the graft copolymer gel and the composite towards divalent metal ions (Cu2+, Pb2+ and Hg2+) were evaluated. The adsorption capacity of the representative samples, Pec-g-poly(METAC-co-AMPS)-A5 and Pec-g-poly(METAC-co-AMPS)/MMT-C2 respectively for Cu2+ are 30.71 and 39.18 mg/g; for Pb2+ are 58.06 and 79.78 mg/g and for Hg2+ are 12.16 and 19.58 mg/g. The re-usability of the materials was also evaluated. The % recovery for the above two systems towards metals ion are 87.91 and 63.46 for Cu2+, 32.13 and 58.30 for Pb2+ and 78.53 and 51.92 for Hg2+. respectively. The adsorption isotherm studies indicated the adsorption of Pb2+, Cu2+ and Hg2+ in both samples is explained best by the Freundlich model except of Hg2+ by Pec-g-poly(METAC-co-AMPS)-A5, which is best explained by the Langmuir model.

Features of the Interaction of Alcian Blue with Gels Based on Copolymer of N-Vinylcaprolactam and Methacrylic Acid

The interaction of N-vinylcaprolactam–methacrylic acid copolymer hydrogel and N-vinylcaprolactam homopolymer hydrogel with alcian blue in aqueous solutions is studied. It is shown that copolymer gel are thermo- and pH-sensitive. Dye sorption by the copolymer gel and gel swelling degree depends on the pH of the solution. The features of the system behavior resulting from the pH sensitivity of both the gel and the dye are shown. The thermocollapse of gels incubated in aqueous solutions of alcian blue is studied. It is shown that the transition temperature of N-vinylcaprolactam–sodium methacrylate copolymer gel to the collapsed state decreases with the dye absorption. The temperature-induced collapse of homopolymer gels in dye solutions is reversible, while the copolymer gel mass restores incompletely during the return temperature decrease. The dye absorption by the copolymer gel leads to decreased hysteresis.

Thermal and electrochemical characterization of a new poly (ethylene oxide) copolymer—gel electrolyte containing polyvalent ion pair of cobalt (CoII/III) or iron (FeII/III)

In this work, gel polymer electrolytes based on the PEO copolymer—poly(ethylene oxide-co-2-(2-methoxyethoxy)ethyl glycidyl ether)), (P(EO-EM))—with a fixed P(EO-EM):GBL (γ-butyrolactone) weight ratio of 30–70% and different concentrations of redox mediators CoII:CoIII or FeII:FeIII were prepared as a possible substitute to the redox couple I−/I3 in dye-sensitized solar cell. The gel polymer electrolytes showed an increase in thermal stability with the addition of iron or cobalt salts. Maximum conductivity of 10−6 and 10−5 S cm−1, at room temperature, was observed for the system containing Co and Fe, respectively. Conductivity variation as a function of temperature showed Arrhenius type thermal activated process. Photoinduced absorption spectroscopy (PAS) tests showed the successful regeneration of the L0 dye by Gel+2 wt% FeII/III and Gel+5 wt% CoII/III. The Gel+2 wt% FeII/III electrolyte was also able to reduce the N719, D35, and Z907 dyes.

Experimental study on a combined profile modification system for EOR by starch graft copolymer gel and N<SUB align="right">2 foam

A combined profile modified system of starch graft copolymer (SGC) gel and N2 foam was investigated to solve the problem of severe fluid channelling in multilayer heterogeneous reservoirs. The investigation was performed from three perspectives: formulas optimisation, blocking performance and oil displacement experiments to demonstrate synergetic blocking effect of the two plugging agents. The results show that this combined profile modified system could plug the higher permeability layers to force the subsequent injected water to mobilise the remaining oil in the lower permeability layer and create synergetic effect to improve oil recovery. [Received: March 8, 2016; Accepted: April 21, 2017]

Experimental study on a combined profile modification system for EOR by starch graft copolymer gel and N<SUB align="right">2 foam

Experimental study on a combined profile modification system for EOR by starch graft copolymer gel and N<SUB align="right">2 foam

A Study on a Copolymer Gelant With High Temperature Resistance for Conformance Control

Due to the limited temperature resistance, the deep conformance control technology of using the conventional hydrolyzed polyacrylamide (HPAM) gel failed to enhance oil recovery in high-temperature heterogeneous oil reservoirs. Therefore, it is necessary to develop a gelant with high temperature resistance to meet the demands of increasing oil production and decreasing water cut in high-temperature heterogeneous oil reservoirs. In this paper, a copolymer is first synthesized by the method of inverse emulsion polymerization using 2-acrylamide-2-tetradecyl ethyl sulfonic acid (AMC16S), acrylamide (AM), and acrylic acid (AA). The developed copolymer has a highly branching skeleton and can resist temperature up to 100 °C. And then, a gelant with high temperature resistance and good shear resistance can be formed by mixing a certain proportion of the developed copolymer and polyethyleneimine (PEI). After the controllable gelation, a copolymer gel is formed and the formed gel can maintain the stable performance for a long time in the high-temperature environment. Experimental results show that the developed gelant can be applied in the conformance control of high-temperature heterogeneous oil reservoir.

New copolymer gels based on N,N-dimethylacrylamide and crown-containing allyl derivative of 1,8-naphthalimide as optical sensors for metal cations in an organic medium

New copolymer gels bases on N,N-dimethylacrylamide and a crown-containing allyl derivative of 1,8-naphthalimide showing intense visible fluorescence have been prepared. The effect of metal cations on the optical properties of the fluorescent monomer and its copolymer gels has been studied. These gels have been found to exhibit optical response selectivity with respect to binding of alkaline-earth metals in an acetonitrile medium.

Dynamical modeling and experimental aspects of multi-responsive hydroxy-functional methacrylate-based gels with tunable swelling induced by multivalent ions

Novel materials displaying multi-responsive property were developed by forming crosslinked copolymer systems that exhibit distinct temperature, pH and salt-sensitivity independently. An investigation of the mechanical properties of a novel multi-responsive poly(hydroxypropyl methacrylate) (PHPMA)-based hydrogel system was carried out with two major objectives. First was to study the effect of various preparation conditions; reaction temperature, comonomer content on the elasticity as well as on the absorbency of resulting hydroxy-functional methacrylate-based gels and the second was to interpret their water uptake data by various kinetic models. Experiments were conducted to characterize the equilibrium swelling and temperature/pH-dependent phase transitions of PHPMA-based copolymeric gels prepared by radical crosslinking copolymerization in aqueous solution with tetraethyleneglycol dimethacrylate (TEGDMA) as crosslinker. The aqueous equilibrium swelling properties of PHPMA hydrogels and cryogels containing methacrylate-based comonomer were described using N,N-dimethylaminopropyl methacrylate (DMAEMA) having weakly basic cationic groups. For PHPMA-based copolymeric hydrogels, the scaling laws relating the optimum preparation conditions with the crosslinking density N and the swelling degree qv were derived. Dynamic kinetics profiles were evaluated to outline the swelling/deswelling response of the resulting hydrogels and cryogels which presents useful information when designing specific applications that pursue or require the absorption of pH-sensitive or ionic-strength-sensitive molecules.

Testing of the effect of parameters on the cononsolvency of random copolymer gels of N-isopropylacrylamide and N-ethylacrylamide in methanol-water mixed solvents by simple gravimetric method

Random copolymer gels of N-isopropylacrylamide (NIPAM) and N-ethylacrylamide (NEAM) were synthesized in using different monomer compositions in 1:1 methanol-water mixtures and in pure water. The samples were characterized by cononsolvency study in methanol-water mixtures at various temperatures by swelling ratio measurements. It is observed that with the variation of the temperature and monomer compositions in the synthesis reaction mixture, the cononsolvency properties varied significantly. But the variation in the solvents compositions by keeping monomer compositions fixed does not affect the cononsolvency much. All results can be explained on the basis of the differences in thermoresponsive character or difference in the hydrophilicity of PNIPAM and PNEAM in water, preferential adsorption of the solvents by polymer networks, solvent-solvent interactions, heterogeneity of the polymer networks synthesized at different solvent compositions and at different temperatures, difference in their morphological properties, etc.

Role of Solvent Water in the Temperature-Induced Self-Assembly of a Triblock Copolymer.

Water-soluble triblock copolymers have received much attention in industrial applications and scientific fields. We here show that femtosecond mid-IR pump-probe spectroscopy is useful to study the role of water in the temperature-induced self-assembly of triblock copolymers. Our experimental results suggest two distinct subpopulations of water molecules: those that interact with other water molecules and those involved in the hydration of a triblock copolymer surface. We find that the vibrational dynamics of bulk-like water is not affected by either micellation or gelation of triblock copolymers. The increased population of water interacting with ether oxygen atoms of the copolymer during the unimer to micelle phase transition is important evidence for the entropic role of water in temperature-induced micelle formation at a low copolymer concentration. In contrast, at the critical gelation temperature and beyond, the population of surface-associated water molecules interacting with ether oxygen atoms decreases, which indicates important enthalpic control by water. The present study on the roles of water in the two different phase transitions of triblock copolymers sheds new light on the underlying mechanisms of temperature-induced self-aggregation behaviors of amphiphiles that are ubiquitous in nature.

Gelation of Triblock Copolymers in Aqueous Solution through CO2 -Triggered Electrostatic Interaction

Polymer systems displaying CO2-triggered rheology alteration are widely investigated in recent years, which can change from nonviscous liquid to high-viscosity solution or even gel by passing CO2 through. Among those polymer systems, a previous study of the group shows that a rationally designed ABA-type triblock copolymer with a hydrophilic middle block and two CO2-responsive end blocks can undergo either gel–sol or sol–gel transition triggered by CO2 as a result of increase or decrease in lower critical solution temperature of A blocks, respectively. This paper describes a new and more flexible approach to achieving CO2-induced gelation of polymer aqueous solution at much lower polymer concentrations. It consists in mixing two water-soluble ABA triblock copolymers that have the same B block but different A blocks: for one polymer, the A blocks are a negatively charged polyelectrolyte, and for the other polymer, the A blocks can be turned positively charged under CO2 stimulation. In this way, CO2 bubbling through an aqueous solution of the two constituent triblock copolymers can induce complexation of the oppositely charged A blocks and, as a result, gelation of the solution of mixed triblock copolymers.

Sorption and desorption properties of random copolymer hydrogels of N‐isopropylacrylamide and N‐ethylacrylamide: Effect of monomer composition

ABSTRACTRandom copolymer hydrogels of N‐isopropylacrylamide and N‐ethylacrylamide (NEAM) were prepared using different monomer compositions in 1:1 methanol–water mixtures. The samples were characterized by cononsolvency study in methanol‐water mixtures at various temperatures, swelling properties measurements, scanning electron microscopy. With changing ratio of the monomers in the reaction mixture, the thermal, morphological and swelling properties, varied significantly. The change in the properties with monomer composition variation are interpreted based on the different thermoresponsive characteristics and interactions of gels of N‐isopropylacrylamide and NEAM (homo‐ and copolymer gels) in water and different methanol‐water mixtures, their variable compositions in the synthesis mixtures, and their morphologies. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45176.

Nanostructured DPA-MPC-DPA triblock copolymer gel for controlled drug release of ketoprofen and spironolactone.

Uncontrolled rapid release of drugs can reduce their therapeutic efficacy and cause undesirable toxicity; however, controlled release from reservoir materials helps overcome this issue. The aims of this study were to determine the release profiles of ketoprofen and spironolactone from a pH-responsive self-assembling DPA-MPC-DPA triblock copolymer gel and elucidate underlying physiochemical properties. Drug release profiles from DPA50 -MPC250 -DPA50 gel (pH 7.5), over 32 h (37 °C), were determined using UV-Vis spectroscopy. Nanoparticle size was measured by dynamic light scattering (DLS) and critical micelle concentration (CMC) by pyrene fluorescence. Polymer gel viscosity was examined via rheology, nanoparticle morphology investigated using scanning transmission electron microscopy (STEM) and the gel matrix observed using cryo-scanning electron microscopy (Cryo-SEM). DPA50 -MPC250 -DPA50 copolymer (15% w/v) formed a free-standing gel (pH 7.5) that controlled drug release relative to free drugs. The copolymer possessed a low CMC, nanoparticle size increased with copolymer concentration, and DLS data were consistent with STEM. The gel displayed thermostable viscosity at physiological temperatures, and the gel matrix was a nanostructured aggregation of smaller nanoparticles. The DPA50 -MPC250 -DPA50 copolymer gel could be used as a drug delivery system to provide the controlled drug release of ketoprofen and spironolactone.

Presence of NaI in PEO/PVdF-HFP blend based gel polymer electrolytes for fabrication of dye-sensitized solar cells

Poly(vinylidene fluoride-co-hexafluoro propylene) copolymer (PVdF-HFP) and polyethylene oxide (PEO) blend gel polymer electrolytes (GPEs) containing ethylene carbonate (EC) and propylene carbonate (PC) as solvent with different concentrations of sodium iodide (NaI) salt are prepared. Effect of sodium iodide (NaI) on the gel polymer electrolyte system is investigated by using electrochemical impedance spectroscopy (EIS), temperature-dependence ionic conductivity, X-ray diffraction (XRD) and FTIR studies. The highest ionic conductivity value for the gel polymer electrolytes are 6.38mScm−1 in the presence of 100wt% of sodium iodide (NaI) salt with respect to weight of PEO/PVdF-HFP polymer blend. The temperature-dependent ionic conductivity study indicates that the gel polymer electrolyte system follows the Arrhenius model. Dye-sensitized solar cells (DSSCs) are fabricated using gel polymer electrolytes and tested under Sun simulator. The highest energy conversion efficiency value of 5.67% is obtained after the addition of 100wt% of sodium iodide (NaI) salt.