Electrical/pH responsive properties of poly(2‐acrylamido‐2‐methylpropane sulfonic acid)/hyaluronic acid hydrogels

Poly(2‐acrylamido‐2‐methylpropane sulfonic acid) (PAMPS)/hyaluronic acid (HA) interpenetrating polymer network (IPN) hydrogels have been prepared by using the sequential‐IPN method. The IPN hydrogels exhibited swelling behavior in solutions at various pHs, in NaCl solutions, and under electrical DC stimulation. The IPN hydrogels were highly swollen in water, but lost much of their water capacity when transferred to solutions having a high ionic strength. The IPN hydrogels showed a significant responsive deswelling in an applied electric field. This behavior indicates the potential application of IPN hydrogels as biomaterials. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1731–1736, 2004     

Study of poly(acrylamide‐co‐2‐acrylamido‐2‐methylpropane sulfonic acid) hydrogels made using gamma radiation initiation

Poly(acrylamide‐co‐2‐acrylamido‐2‐methylpropane sulfonic acid) hydrogels were synthesized using gamma‐radiation‐initiated polymerization. The progress of copolymerization and crosslinking was observed by viscosity measurement on reaction mixtures subjected to varying radiation doses. The copolymer gels were characterized by differential scanning calorimetry, X‐ray diffraction, scanning electron microscopy, infrared spectroscopy, and elemental analysis. The swelling behavior and other properties of the gels were found to be very similar to those of poly(acrylamide‐co‐2‐acrylamido‐2‐methylpropane sulfonic acid) hydrogels synthesized using conventional free‐radical initiation in the presence of crosslinkers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1322–1330, 2003     

Swelling properties of CMC‐g‐poly (AAm‐co‐AMPS) superabsorbent hydrogel

A series of biopolymer‐based superabsorbent hydrogels based on carboxymethyl cellulose has been prepared by free‐radical graft copolymerization of acrylamide and 2‐acrylamido‐2‐methylpropan sulfonic acid (AMPS) in aqueous solution using methylenebisacrylamide as a crosslinking agent and ammonium persulfate as an initiator. The effect of variables on the swelling capacity such as: acrylamide/AMPS weight ratio, reaction temperature, and concentration of the initiator and crosslinker were systematically optimized. The results indicated that with increasing the amount of AMPS, the swelling capacity is increased. FT‐IR spectroscopy and scanning electron microscope analysis were used to confirm the hydrogel structure. Swelling measurements of the synthesized hydrogels in different salt solutions indicated considerable swelling capacity. The absorbency under load of the superabsorbent hydrogels was determined by using an absorbency under load tester at various applied pressures. A preliminary swelling and deswelling behaviors of the hydrogels were also studied. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Acrylonitrile/acrylamidoxime/2‐acrylamido‐2‐ methylpropane sulfonic acid‐based hydrogels: Synthesis,characterization and their application in the removal of heavy metals

Crosslinked acrylonitrile/acrylamidoxime/2‐acrylamido‐2‐methylpropane sulfonic acid (AN/AAx/AMPS)‐based hydrogels were prepared by free radical crosslinking solution polymerization technique. The chemical structures of the hydrogels were characterized by FT‐IR analysis. The morphology of the dry hydrogel sample was examined by scanning electron microscope (SEM). These hydrogels were used for the removal of Cd(II), Cu(II), and Fe(III) ions from their aqueous solutions. The influence of the uptake conditions such as pH, time and initial feed concentration on the metal ion binding capacity of hydrogel was also tested. The selectivity of the hydrogel towards the different metal ions tested was arranged in the order of Cd(II) > Fe(III) > Cu(II). It was observed that the specific interaction between metal ions and ionic comonomer in the hydrogel affected the metal binding capacity of the hydrogel. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of novel core‐shell magnetic nanogels based on 2‐acrylamido‐2‐methylpropane sulfonic acid in aqueous media

Ultrafine well‐dispersed Fe₃O₄ magnetic nanoparticles were directly prepared in aqueous solution using controlled coprecipitation method. The synthesis of Fe₃O₄/poly (2‐acrylamido‐2‐methylpropane sulfonic acid) (PAMPS), Fe₃O₄/poly (acrylamide‐co‐2‐acrylamido‐2‐methylpropane sulfonic acid) poly(AM‐co‐AMPS) and Fe₃O₄/poly (acrylic acid‐co‐2‐acrylamido‐2‐methylpropane sulfonic acid) poly(AA‐co‐AMPS) ‐core/shell nanogels are reported. The nanogels were prepared via crosslinking copolymerization of 2‐acrylamido‐2‐methylpropane sulfonic acid, acrylamide and acrylic acid monomers in the presence of Fe₃O₄ nanoparticles, N,N′‐methylenebisacrylamide (MBA) as a crosslinker, N,N,N′,N′‐tetramethylethylenediamine (TEMED) and potassium peroxydisulfate (KPS) as redox initiator system. The results of FTIR and ¹H‐NMR spectra indicated that the compositions of the prepared nanogels are consistent with the designed structure. X‐ray powder diffraction (XRD) and transmission electron microscope (TEM) measurements were used to determine the size of both magnetite and stabilized polymer coated magnetite nanoparticles. The data showed that the mean particle size of synthesized magnetite (Fe₃O₄) nanoparticles was about 10 nm. The diameter of the stabilized polymer coated Fe₃O₄ nanogels ranged from 50 to 250 nm based on polymer type. TEM micrographs proved that nanogels possess the spherical morphology before and after swelling. These nanogels exhibited pH‐induced phase transition due to protonation of AMPS copolymer chains. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Chitosan‐modified nanoclay–poly(AMPS) nanocomposite hydrogels with improved gel strength

BACKGROUND: Making (nano)composite structures is one of the efficient approaches for strengthening hydrogels extended in recent years. The present paper deals with the synthesis and properties of novel nanocomposite hydrogels based on 2‐acrylamido‐2‐methylpropane‐1‐sulfonic acid (AMPS). Initially, a bio‐modified clay, chitosan‐intercalated montmorillonite (chitoMMT), was prepared. Then, this was incorporated into the polymerization of AMPS in the presence of a macro‐crosslinker, i.e. poly(ethylene glycol) dimethacrylate, to yield super‐swelling nanocomposite hydrogels. The swelling capacity as well as some structural, rheological and thermomechanical properties of the hydrogels were studied and compared with those of the clay‐free counterpart. RESULTS: ChitoMMT exhibited no toxicity, which was confirmed using cell‐culture testing. A chitoMMT content of ca 6% was found to be the most favourable content of the bio‐modified clay for achieving a product with improved properties (i.e. the highest gel content, the highest gel strength and optimal thermal stability). Based on a dynamic mechanical thermal analysis study, an increased glass transition temperature (98.2 °C) and improved rubbery modulus (up to 238% higher than that of the clay‐free counterpart) were recorded. Thermogravimetric analysis verified that the thermal stability of nanocomposite samples was higher than that of clay‐free samples. CONCLUSION: Owing to the non‐toxicity of the incorporated chitoMMT, the strengthened hydrogels may be considered as potential candidates for bio‐applications. Copyright © 2009 Society of Chemical Industry     

Application of anionic acrylamide‐based hydrogels in the removal of heavy metals from waste water

Crosslinked acrylamide (AM) and 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) homopolymers and copolymers were prepared by free radical solution polymerization using N,N′‐methylenebisacrylamide as the crosslinker. The chemical structures of hydrogels were characterized by FTIR analysis and the results were consistent with the expected structures. These hydrogels were used for the separation of Cd(II), Cu(II), and Fe(III) ions from their aqueous solutions. The influence of the uptake conditions such as pH, time and initial feed concentration on the metal ion binding capacity of hydrogel was also tested. The selectivity of the hydrogel towards the different metal ions tested was Cd(II) > Cu(II) > Fe(III). It was observed that the specific interaction between metal ions and ionic comonomers in the hydrogel affected the metal binding capacity of the hydrogel. The recovery of metal ions was also investigated in acid media. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effects of synthesis‐solvent composition and initiator concentration on the swelling behaviour of poly(N‐isopropylacrylamide) P(NIPAAM), poly(NIPAAM‐co‐dimethyl itaconate), and poly(NIPAAM‐co itaconic acid) gels

The effects of synthesis‐solvent composition, initiator concentration, comonomer type and monomer purity on the volume swelling ratios, and polymer‐solvent interaction parameter χ have been investigated as a function of temperature. Non‐ionic N‐isopropylacrylamide (NIPAAM) homopolymer gels, poly[NIPAAM‐co‐(dimethyl itaconate)] (P(NIPAAM‐co‐DMI)) and poly[NIPAAM‐co‐(itaconic acid)] (P(NIPAAM‐co‐IA)) gels containing hydrophobic (DMI) and hydrophilic (IA) comonomers were prepared by free radical polymerization using potassium persulfate (KPS) –N, N, N′, N′‐tetramethyl ethylene diamine (TEMED) (redox initiator) in the presence of an N, N′‐methylene bis(acrylamide) (MBAAM) cross‐linking agent. The synthesis‐solvent composition (40/60 mixture of water/methanol and water) and initiator concentration employed significantly affected the properties of the NIPAAM gels. The transition temperatures of P(NIPAAM‐co‐IA) gels synthesized in water/methanol mixture were higher than that of the gel obtained in water. Furthermore, χ values of the NIPAAM homopolymer gel prepared with higher KPS content was an increasing function of temperature, while χ values of the sample obtained with lower initiator concentration changed around a critical solubility value 0.50. The results obtained also show that the interactions between monomer and solvent molecules in the reaction media (ie composition of the pregel solution) have an important effect on the formation and properties of the network structure (ie pore sizes of the gels). © 2000 Society of Chemical Industry     

Effects of mixed solvent on gelation of poly(vinyl alcohol) solutions

The relationship between the polymer–solvent interaction and gelation behavior of poly(vinyl alcohol) (PVA) solutions prepared from ethylene glycol/water (EG/water) mixed solvents was investigated using a viscometer, light scattering, FTIR, X‐ray, and pulsed NMR analyses. The viscometric result showed that the affinity to PVA for water is higher than that for EG. The light scattering result showed that the spinodal decomposition rate of the PVA solution decreases rapidly as the water content in the EG/water mixed solvent is increased. On the other hand, the FTIR and X‐ray results both indicated that the crystallinity of the PVA gel decreases with water content. These results imply that the water molecules must improve the affinity of the solvent to PVA to inhibit the aggregation or crystallization of PVA chains. The pulsed NMR measurement results showed that the spin–spin relaxation times related to the polymer‐rich and polymer‐poor phases of the PVA gel increase, and the fractional amount of the polymer‐poor phase increases while that of the polymer‐rich phase decreases with increasing water content. These facts indicated that the increase in the mobility of PVA chains must give rise to the difficulty in chain aggregation of PVA solutions with increasing water content. Two transition temperatures were found in the phase transition of the polymer‐rich phase. The lower transition temperature was attributed to the destruction of the denser chain entanglements in the polymer‐rich phase and the higher transition temperature was mainly concerned with the melting of the crystallites. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1113–1120, 2001     

Effect of polycarbonate–poly(methyl methacrylate) graft copolymer as a modifier improving the surface hardness of polycarbonate

In this study, poly(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid) (PAMPS) was synthesized using potassium persulfate (K₂S₂O₈) as initiator. PAMPS (M _n = 36,000 g/mol) was partially converted to a lithium salt (PAMPS–Li), and particle size was determined to be 40 μm. Suspensions of PAMPS–Li at various concentrations were prepared in silicone oil, mineral oil, dioctylphthalate (DOP), and trioctyltrimellitate (TOTM) insulating oils. Colloidal stabilities of these suspensions were determined at 20 and 80°C. The PAMPS–Li suspensions were observed to provide an electrorheological (ER) response upon the application of an external dc electric field. ER properties of these suspensions were investigated at various shear rates (γ˙) and electric field strengths (E). Further, effects of polar promoters and high temperature on ER activity were determined, and excess shear stresses (Δτ) were calculated. A shear‐thinning non‐Newtonian viscoelastic behavior was observed for the PAMPS–Li suspensions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1106–1112, 2002     

Novel shrinking–swelling hysteresis in DMSO/THF mixtures of copolymer gels containing sulphonate groups

The swelling volume of copolymer gels made from 2-(acrylamido)-2-methylpropanesulphonic acid (AMPS; electrolyte monomer), N,N-dimethylacrylamide (DMAA; comonomer) and N,N′-methylenebis(acrylamide) (BIS; crosslinker) was measured in mixtures of two organic solvents, dimethyl sulphoxide (DMSO) and tetrahydrofuran (THF) at 25°C. A volume phase transition was observed in the gels having 43·18mol% AMPS with different counterions K⁺, Na⁺ and H⁺, when the THF concentration in the mixture increased beyond a certain value. We observed a swelling-hysteresis between the shrinking and swelling curves, i.e. more DMSO was required to make a shrunk gel start to swell again than to cause the volume shrinking. This hysteresis stems from the formation of ion pairs and/or multiplets in the ionizable gels when the medium polarity is decreased. An excess of DMSO is required to reduce the ionization energy for making the shrunk gel swell again in the DMSO/THF mixture. These aggregates and multiplets do not seem to be entirely removed by the swelling process and act as additional physical crosslinks, so that the DMSO concentration required to induce the shrunk gel to swell becomes higher in the next swelling process, showing another hysteresis. The release of bound water from the solvating layer after shrinkage may be another possible reason for this hysteresis. © 1998 Society of Chemical Industry     

P(AM/AMPS/NVP)降失水剂合成与耐温性能研究

采用自由基水溶液聚合法成功制备了丙烯酰胺(AM)/2-甲基-2-丙烯酰胺基丙磺酸(AMPS)/N-乙烯基吡咯烷酮(NVP)三元共聚耐温型降滤失剂,通过红外(FTIR)光谱和核磁C谱表征了共聚物的结构,通过元素分析考察了共聚物组成。热失重(TGA)表明,P(AM/AMPS/NVP)耐温性优于P(AM/AMPS)和P(AM),通过对三元共聚物的抗高温性和降失水性的研究,表明P(AM/AMPS/NVP)具有良好的耐温降滤失性能。     

Mixed poly(methyl methacrylate)/poly(ethylene glycol) brushes: Study of switching behavior in selective solvent

The mixed polymer brushes composed of two incompatible polymers, poly(methyl methacrylate) and poly(ethylene glycol), were successfully synthesized via a sequential grafting to method, which was confirmed by water‐contact angle and ellipsometric measurements. The resulted mixed polymer brushes could undergo conformational rearrangements upon exposure to different selective solvents, and then the lateral segregation in nonselective solvent and perpendicular segregation in selective solvent happened. As a result, the mixed polymer brushes exhibited the ripple morphology and dimple morphology in corresponding solvent, respectively, and which led to changes in water‐contact angle and surface composition as a function of bulk composition of the mixed polymer brushes. Moreover, the switching properties as the surface composition, wettability and topographical images could occur in a controlled and reversible fashion. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

聚L-乳酸在大分子体积溶剂中的结晶性能

聚L-乳酸(PLLA)的结晶性能影响着其生物降解速度和机械强度。采用广角X射线衍射(XRD)和差示扫描量热(DSC)方法研究溶剂分子体积对PLLA结晶性能的影响。以分子摩尔体积较大的聚乙二醇(PEG)为溶剂,PLLA在较高质量分数溶液(10%)中仍具有高的结晶度(73%)、高的非等温结晶温度和快的结晶速度,结晶速度系数CRC为0.659,高于从质量分数10%小分子溶剂中结晶的结晶速度。溶剂分子的摩尔体积对聚合物分子的构象有明显的影响,从而直接影响着PLLA的结晶速度和结晶度。     

Preparation and characterization of poly(2‐acrylamido‐2‐methylpropane‐sulfonic acid) grafted chitosan using potassium persulfate as redox initiator

A grafted material based on chitosan and 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) has been successfully prepared in homogenous solution using potassium persulfate as a redox initiator. The grafted copolymer was precipitated during the reaction polymerization. The effects of the reaction temperature and chitosan–potassium persulfate contact time as well as concentrations of AMPS, potassium persulfate, and acetic acid on grafting yield were investigated. The percentage of grafting is gradually increased with the increasing of the AMPS concentration. The extent of grafting can be controlled by setting the appropriate reaction conditions. The maximum percentage of grafting was about 180% under the optimum conditions (1% v/v acetic acid, 50°C reaction temperature, 10 min chitosan–potassium persulfate mixing period, 0.37 mmol of potassium persulfate, and 28.96 mmol AMPS). The grafted chitosan was insoluble in the acid of the grafting. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2314–2318, 2000     

Pre‐thermal treatment in binary solvent systems promoting β crystalline phase of electrospun poly(vinylidene fluoride) nanofibers

Poly(vinylidene fluoride) (PVDF) nanofibers were fabricated via electrospinning with an investigation of various ratios of binary solvents at different temperatures. The amount of acetone influenced the morphology. Scanning electron microscopy showed a PVDF membrane composed of smooth and unblemished fibers without beads and dark spots with small diameters of 201 ± 54 nm at a dimethylformamide‐to‐acetone ratio of 4:6. The temperature of pre‐thermal treatment from room temperature to 120 °C was investigated to promote the β crystalline phase in electrospun PVDF nanofibers. The result was characterized using Fourier transform infrared (FTIR) spectroscopy and X‐ray diffraction (XRD). PVDF solution prepared at 80 °C was used to increase the β crystalline phase of the electrospun PVDF nanofibers due to the transformation of α to β phase occurring during the spinning process and also bead‐free PVDF nanofibers were obtained. Differential scanning calorimetry revealed crystallization behavior corresponding with that determined using FTIR spectroscopy and XRD. Therefore, the solvent proportion and pretreatment temperature were observed to affect ultrafine nanofiber and crystalline structure of PVDF, respectively. © 2020 Society of Chemical Industry     

Phase equilibrium characteristics of supercritical CO2/poly(ethylene terephthalate) binary system

The solubility of carbon dioxide in poly (ethylene terephthalate) (PET) at high pressure and elevated temperature conditions was investigated for a better understanding of the phase equilibrium characteristics of supercritical CO₂/PET binary system and useful data for the process development of the supercritical fluid dyeing. Based on the principle of pressure decaying, a novel experimental apparatus suitable to high pressure and high temperature measurement was established. The solubilities of CO₂ in PET were measured with the apparatus at temperatures of 110, 120, and 130°C and pressures up to 30.0 MPa. The results show that the solubility of CO₂ in PET increases with the increase of pressure and CO₂ density, respectively, at a constant temperature, whereas it decreases with the increase of temperature at a constant pressure. The Sanchez‐Lacombe equation of state (S‐L EOS) was used to correlate the experimental data. The calculated results are in good agreement with the experimental ones. The average absolute relative derivation (AARD) is less than 3.91%. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Phase study of nylon 6/poly (acrylic acid) blends cast from solutions in aqueous formic acid

Blends of nylon 6 (Ny6) with poly(acrylic acid) (PAA) were prepared in film form from solutions in a mixture of formic acid and water by evaporating the solvent. The miscibility and phase constitution of the binary blends obtained over a wide composition range (5/95–95/5) were examined by wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and dynamic mechanical measurements. A Ny6 homopolymer film and Ny6/PAA blends with PAA concentrations ≥ 50 wt% exhibited a WAXD profile stemmed from the coexistence of two different crystalline modifications of Ny6, i.e. the α and γ forms. Above 50 wt% PAA content, the solution-cast blends showed no definite crystallinity. It was found by DSC thermal analysis that the polymer pair is substantially miscible in the non-crystalline state, since a single glass transition temperature (T_g) was situated between the T_gs of the two homopolymers at every composition; however, the T_g versus composition plots did not follow a monotonic function but yielded a peak maximum at a PAA concentration of c. 25 wt%. In order to interpret this phenomenon, attention was given to the following point revealed by dynamic mechanical measurements: at the compositions of Ny6/PAA = 100/0–50/50, a phase of low regularity such as a nematic structure is formed in the cast films.     

Coiling/uncoiling behaviour of sodium polystyrenesulfonate in 2‐ethoxyethanol–water mixed solvent media as probed using viscometry

Precise measurements of the viscosities of solutions of sodium polystyrenesulfonate in water and in 2‐ethoxyethanol–water mixtures containing varying amounts of 2‐ethoxyethanol have been performed at 308.15, 313.15, 318.15 and 323.15 K. The intramolecular contributions to the reduced viscosities of the polyelectrolyte solutions were obtained through isoionic dilution maintaining the total ionic strengths of the solutions at polyelectrolyte concentrations of 0.0033, 0.0054 and 0.0080 eq L^?1 with sodium chloride. The Huggins constants were also obtained from the experimental data. The influences of the medium and the temperature on the intramolecular contributions to the reduced viscosities as well as on the Huggins constants have been interpreted from the points of view of the conformational characteristics and polyelectrolyte–solvent and polyelectrolyte–polyelectrolyte interactions prevailing in the polyelectrolyte solutions under investigation. Polyion chains were found to coil upon addition of 2‐ethoxyethanol to water or upon an increase of temperature. Thermodynamic affinities for polyelectrolyte–solvent and polyelectrolyte–polyelectrolyte interactions were found to depend greatly on the medium. © 2014 Society of Chemical Industry     

Influence of ethyl methacrylate content on the volume‐phase transition of temperature‐sensitive poly[(N‐isopropylacrylamide)‐co‐(ethyl methacrylate)] microgels

A novel series of temperature‐sensitive poly[(N‐isopropylacrylamide)‐co‐(ethyl methacrylate)] (p(NIPAM‐co‐EMA)) microgels was prepared by the surfactant‐free radical polymerization of N‐isopropylacrylamide (NIPAM) with ethyl methacrylate (EMA). The shape, size dispersity and volume‐phase transition behavior of the microgels were investigated by transmission electron microscopy (TEM), ultraviolet–visible (UV–Vis) spectroscopy, dynamic light scattering (DLS) and differential scanning calorimetry (DSC). The transmission electron micrographs and DLS results showed that microgels with narrow distributions were prepared. It was shown from UV–Vis, DLS and DSC measurements that the volume‐phase transition temperature (VPTT) of the p(NIPAM‐co‐EMA) microgels decreased with increasing incorporation of EMA, but the temperature‐sensitivity was impaired when more EMA was incorporated, causing the volume‐phase transition of the microgels to become more continuous. It is noteworthy that incorporation of moderate amounts of EMA could not only lower the VPTT but also enhance the temperature‐sensitivity of the microgels. The reason for this phenomenon could be attributed to changes in the complicated interactions between the various molecules. Copyright © 2004 Society of Chemical Industry