Retracted: Drug release properties of poly(vinyl pyrrolidone)/acrylic acid copolymer hydrogels

The following article from the Journal of Applied Polymer Science, “Drug release properties of poly(vinyl pyrrolidone)/acrylic acid copolymer hydrogels,” by Abdullah S. Alarifi, published online on 14 February 2011 in Wiley Online Library (wileyonlinelibrary.com), and in Volume 120, pp. 3484‐3489, has been retracted by agreement between the journal's editors and Wiley Periodicals, Inc. The retraction has been agreed because of unacknowledged overlap with work previously published in the Arab Journal of Nuclear Sciences and Applications ( 2010 , 43, 366), as well as in Proceeding, 2nd International Conference on Radiation Sciences and Applications (Egyptian Society of Radiation Sciences and Applications: Marsa Alam, Egypt, 2010 ; p 362).     

Swelling and mechanical properties of superporous hydrogels of poly(acrylamide-co-acrylic acid)/polyethylenimine interpenetrating polymer networks

Swelling and mechanical properties were investigated for superporous hydrogels (SPHs) of poly(acrylamide-co-acrylic acid)/polyethylenimine (P(AM-co-AA)/PEI) interpenetrating polymer networks (IPNs). Gelation kinetics of SPHs changed significantly according to the acidic condition of reactant. The compressive strength of neutralized SPHs decreased monotonically with AA concentration, while the maximum swelling was observed around the AA weight fraction of 0.4 for all PEI concentrations. The SPH samples composed of high concentrations of AA and PEI were easily cracked in water due to the swelling stress developed during water uptake. The swelling kinetics decreased with increasing PEI and PAA concentrations because of the high molecular entanglement and network density associated with ionic interaction between PAA and PEI molecules. For non-neutralized SPHs, the equilibrium water uptake decreased but the compressive strength increased with PEI and PAA concentrations by simple plasticization effect.     

Poly(amino acid)/ZnO nanoparticles nanocomposites with enhanced thermal,mechanical, and antibacterial properties

Polymer Bulletin - Poly(amino acid) (PAA)-based nanocomposites were synthesized by in situ melting polycondensation with addition of different contents of ZnO nanoparticles (ZnO NPs); the...     

Synthesis and properties of a poly(acrylic acid)/montmorillonite superabsorbent nanocomposite

A novel superabsorbent nanocomposite was synthesized through the intercalation polymerization of partially neutralized acrylic acid and a sodium‐type montmorillonite powder with N,N′‐methylenebisacrylamide as a crosslinker and ammonium persulfate and sodium sulfite as a type of mixed redox initiator. The effects of such factors as the amounts of the sodium‐type montmorillonite, crosslinker, and initiator and neutralization degree on the water absorbency of the nanocomposite were investigated. The structure and micrographs of the superabsorbent were characterized with Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy. The results showed that the acrylic acid monomer was successfully intercalated into the montmorillonite layers and banded together with them. The montmorillonite layers were exfoliated and basically dispersed in the composite on a nanoscale after the polymerization. The water absorbency of the nanocomposite was much higher than that of pure poly(acrylic acid). The optimum absorbency of the nanocomposite in distilled water and saline water (NaCl concentration = 0.9%) was 1201 and 83 g/g, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5725–5730, 2006     

Morphology,mechanical, and rheological properties of poly(lactic acid)/ethylene acrylic acid copolymer blends processing via vane extruder

This work aimed to study, for the first time, the melt blending of poly(lactic acid) (PLA) and ethylene acrylic acid (EAA) copolymer by a novel vane extruder to toughen PLA. The phase morphologies, mechanical, and rheological properties of the PLA/EAA blends of three weight ratios (90/10, 80/20, and 70/30) were investigated. The results showed that the addition of EAA improves the toughness of PLA at the expense of the tensile strength to a certain degree and leads the transition from brittle fracture of PLA into ductile fracture. The 80/20 (w/w) PLA/EAA blend presents the maximum elongation at break (13.93%) and impact strength (3.18 kJ/m²), which is 2.2 and 1.2 times as large as those of PLA, respectively. The 90/10 and 80/20 PLA/EAA blends exhibit droplet‐matrix morphologies with number average radii of 0.30–0.73 μm, whereas the 70/30 PLA/EAA blend presents an elongated co‐continuous structure with large radius (2.61 μm) of EAA phase and there exists PLA droplets in EAA phase. These three blends with different phase morphologies display different characteristic linear viscoelastic properties in the low frequency region, which were investigated in terms of their complex viscosity, storage modulus, loss tangent, and Cole‐Cole plots. Specially, the 80/20 PLA/EAA blend presents two circular arcs on its Cole‐Cole plot. So, the longest relaxation time of the 80/20 blend was obtained from its complex viscosity imaginary part plot, and the interfacial tension between PLA and EAA, which is 4.4 mN/m, was calculated using the Palierne model. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40146.     

Effect of compatibilizer and organoclay content on structure,thermal, and mechanical properties of poly(butylene succinate)/(Ethylene acrylic acid)/Organoclay nanocomposites

Poly(butylene succinate) (PBS)/(ethylene acrylic acid) (EAA)/organoclay nanocomposites were prepared by using the melt intercalation technique. EAA was used as compatibilizer and organoclay was used as inorganic filler. X‐ray diffraction and transmission electron microscopy results indicated the addition of compatibilizer led to a large increase in basal spacing of nanocomposites and better overall dispersion of organoclay in the PBS matrix. However, the basal spacing was found to be invariant as the organoclay content increased. The differential scanning calorimetry analyses revealed that the incorporation of the organoclay and EAA and the variation of organoclay content altered the melting behavior and crystallization properties of PBS. Storage and loss modulus of virgin matrix increased with the incorporation of organoclay and EAA, and a maximum for the nanocomposite with 9 wt% organoclay. Moreover, the glass transition temperatures also increased for the various organoclay‐containing samples. Mechanical properties showed an increase with the incorporation of organoclay and EAA. The 5 wt% organoclay‐filled PBS gave the highest tensile strength and notched Izod impact strength among all the composites. Further increments in organoclay loading reduced the tensile strength and notched impact strength of nanocomposites, which was thought to be the result of agglomeration. However, increments in clay loading enhanced the flexural strength and flexural modulus of nanocomposites, with a maximum at 9 wt% organoclay. J. VINYL ADDIT. TECHNOL., 23:219–227, 2017. © 2015 Society of Plastics Engineers     

Preparation and swelling properties of a starch-g-poly(acrylic acid)/organo-mordenite hydrogel composite

A novel hydrogel composite was prepared via inverse suspension polymerization using starch, acrylic acid and organo-mordenite micropowder with the crosslinker, N,N′-methylenebisacrylamide and the initiator, potassium persulfate. Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy confirmed that the acrylic acid was grafted onto the backbone of the corn starch, that the organo-mordenite participated in the polymerization, and that the addition of organo-mordenite improved the surface morphology of the hydrogel composite. The swelling capacity of the hydrogel composite was evaluated in distilled water, and solutions with different pH values, and various salt solutions. It was found that the incorporation of 10 wt-% organo-mordenite enhanced the water absorbency by 144% (from 268 to 655 g·g⁻¹) and swelling was extremely sensitive to the pH values, the concentration of the salt solution and cation type. Swelling kinetics and water diffusion mechanism of the hydrogel composite in distilled water were also discussed. Moreover, the hydrogel composite showed excellent reversibility of water absorption even after five repetitive cycles and the hydrogel composite exhibited significant environmental-responsiveness by changing the swelling medium from distilled water to 0.1 mol·L⁻¹ NaCl solution. In addition, the loading and release of urea by the hydrogel composite were tested and the nutrient-slow-release capability of this material was found to be suitable for many potential applications.     

壳聚糖接枝聚丙烯酸钠/高岭土复合树脂的吸水性能

利用溶液聚合法制备了壳聚糖接枝聚丙烯酸钠/高岭土复合树脂,研究了复合树脂在蒸馏水中的吸水速率、重复吸水性能和人工尿液中的吸水倍率,以及在不同温度、不同电解质溶液离子强度和不同pH值的环境下复合树脂的吸水性能。结果表明,复合树脂的吸水速率较慢,在多次重复吸水后吸水性能也逐渐降低,在人工尿液中的吸水倍率高于聚丙烯酸钠树脂,低于壳聚糖接枝丙烯酸钠树脂;随着温度的升高,复合树脂的吸水能力增强,超过50℃后变化较小;树脂的吸液倍率随着电解质溶液浓度和价态的增大而下降;随着pH值的增大而出现驼峰,在pH=3.5和pH=8.5处分别出现吸液倍率最大值。     

Properties of electroresponsive poly(vinyl alcohol)/poly(acrylic acid) IPN hydrogels under an electric stimulus

Interpenetrating polymer networks (IPNs) composed of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAAc) exhibited electrical-sensitive behavior. PAAc as an initial network was prepared inside a PVA solution using UV irradiation; then, PVA networks as a secondary network were formed by a repetitive freeze–thawing process. Their mechanical properties were influenced by the swelling ratio, crosslinking by UV radiation and a freeze–thawing process, and intermolecular force by hydrogen bonding. When a swollen PVA/PAAc IPN was placed between a pair of electrodes, the IPN exhibited bending behavior upon the applied electric field. The equilibrium bending angle (EBA) and the bending speed of the PVA/PAAc IPN increased with the applied voltage and the content of the PAAc network having negatively charged ionic groups within the IPN. The electroresponsive behavior of the present IPN was also affected by the electrolyte concentration of the external solution. Particularly, IPN37 showed a maximum EBA when the critical ionic strength was 0.1. Anisotropic deswelling of the IPN was observed in a direct contact with a pair of electrodes under aerobic conditions. The PVA/PAAc IPN also showed stepwise bending behavior depending on the electric stimulus. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1675–1683, 1999     

The molecular origin of enhanced toughness in double-network hydrogels: A neutron scattering study

Double-network hydrogels (DN-gels) are a new class of crosslinked polymer networks with extraordinary mechanical properties while containing 80–90 vol.% water. Small-angle neutron scattering (SANS) was applied to investigate the molecular origin of the mechanical properties observed in DN-gels. We present SANS results in both deformed and undeformed conditions for a tough DN-gel made of poly(2-acrylamido-2-methyl-1-propane sulfonic acid) (PAMPS) and polyacrylamide (PAAm). The SANS measurements indicate that deformation of DN-gels results in periodic and mesoscale (1.5 μm) compositional fluctuations in both PAMPS and PAAm. In addition, SANS measurements also indicate that the DN-gel constituents interact favorably with each other while in water. This favorable interaction between PAMPS and PAAm is consistent with the rheological results on solution mixtures of these two polymers. The implications of the above observations to toughening mechanisms are discussed.     

Spatial inhomogeneity in poly(acrylic acid) hydrogels

The crosslink density distribution in gels known as the spatial gel inhomogeneity has been investigated in poly(acrylic acid) (PAAc) gels with the static light scattering measurements. PAAc gels were prepared at a fixed chemical crosslink density but at various initial monomer concentrations. The gels were characterized by swelling and elasticity tests as well as by light scattering measurements. PAAc gels exhibit a maximum degree of spatial inhomogeneity at a critical monomer concentration . shifts toward higher concentrations as the gel swells beyond its dilution degree after preparation. Depending on the polymer concentration in gels, swelling reduces or enhances the extent of the spatial inhomogeneities. It was shown that the apparent degree of the spatial gel inhomogeneity is determined by the combination of three effects, namely the effects of the effective crosslink density, charge density and segment density. The relative magnitudes of these effects vary depending on the polymer concentration and lead to the appearance of a maximum degree of spatial inhomogeneity at a critical concentration.     

Preparation and enhanced mechanical properties of hydroxyapatite hybrid hydrogels via novel photocatalytic polymerization

Hydroxyapatite (HA) hybridized poly(N-isopropylacrylamide)-co-acrylic acid (PNIPAM-co-AAc) hydrogel on thermoplastic polyurethane (TPU) were successfully prepared via photocatalytic polymerization technique. Low temperature plasma processing of HMDSZ and O₂ plasma were deposition on substrate. The HA/hydrogel were stabilized by HA of which the wettability was modified by calcium nitrate and ammonium phosphate dibasic. The HA gradually increases with the increase of time cycles. The deposition of organic silicone group by the HMDSZ on the TPU substrate is hydrophobic surface. When deposition of O₂, the water contact angles (WCA) was changed to <10° and surface hydrophilicity. The materials were characterized by OM, SEM, FT-IR, XPS and XRD. The results showed that the NIPAM: AAc (1:1 mol) polymers possess macropores ranging from 2 to 20 μm, and their large numbers of carboxyl groups and hydroxyl groups result in a favorable adsorption capacity for HA. Swelling studies indicated that NIPAM: AAc (1:1 mol) was 446 ± 0.3%. This work provided a promising alternative method for the fabrication of polymer materials with tunable and interconnected pores structures for the HA.     

Rheological and mechanical properties of poly(lactic acid)/polystyrene polymer blend

Properties modification by blending polymers has been an area of immense interest. In this work, rheological and mechanical properties of poly(lactic acid)/polystyrene (PLA/PS) blends were investigated. PLA/PS blends in different ratios were prepared using a laboratory scale single screw extruder to obtain (3 mm) granules. Rheological properties were studied using a capillary rheometer and the Bagley’s correction was performed. True shear rate (γ _r ), true shear stress (τ _r ), and true viscosity (η _r ) were determined, the relationship between true viscosity and (1/T) was studied for PLA70 blend and the flow activation energy at a constant shear stress (E _τ ) and a constant shear rate (E _γ ) was determined. The mechanical property measurements were performed at room temperature. Stress at break and strain at break were determined. The results showed that PLA/PS blend exhibited a typical shear-thinning behavior over the range of the studied shear rates, and the viscosity of the blend decreased with increasing PLA content. Also it was found that no equal-viscosity temperature exists between PLA and PS. The mechanical results showed immiscibility between PLA and PS in the blend.     

Rapid swelling and deswelling of semi‐interpenetrating network poly(acrylic acid)/poly(aspartic acid) hydrogels prepared by freezing polymerization

Hydrogels with semi‐interpenetrating networks composed of poly(acrylic acid) (PAAc) and poly(aspartic acid) (PASP) have great potential for pharmaceutical and biomedical applications. In this study, we aimed to synthesize semi‐interpenetrating PAAc/PASP hydrogels with improved swelling–deswelling properties via two‐step polymerization, in which the first step of polymerization was performed at 37 °C for 15 min and the second step, the freezing polymerization, was performed at ?20 °C for 24 h. The synthesized hydrogels were characterized with field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The swelling and deswelling behaviors of the hydrogels in response to the ionic strength of the buffer solution were investigated. The Schott's swelling kinetic model was used to elucidate the swelling behavior of the hydrogels. The swelling and deswelling rates of the hydrogels prepared via freezing polymerization were faster than those of the hydrogels prepared via conventional polymerization. This was attributed to the large mean pore size of the freeze‐polymerized hydrogels. The PAAc/PASP hydrogels that underwent freezing polymerization had better swelling–deswelling characteristics than the PAAc hydrogels. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43515.     

Effect of preparation methods on thermal properties of poly(acrylic acid)/silica composites

Poly(acrylic acid)-silica composites have been prepared by two different methods and thermally characterized. The glass transition temperature (T_g) of the PAA-SiO₂ system prepared by mixture method was found to be 120°C irrespective of the type and amounts of silica involved in this work. However, the T_g varied between 132°C and 113°C in the systems prepared by polymerization reaction depending upon the type of silica and percentage conversion. The composites prepared by mixture and polymerization method have been investigated by using thermogravimetry (TGA) to follow the kinetics of anhydride formation and thermal degradation reactions. The activation energy of thermal anhydride formation and thermal degradation reaction was not found to change very much with ratio of PAA-SiO₂ when the composites were prepared by simple mixing. For the composites prepared by polymerization method the activation energy of anhydride formation and thermal degradation reaction were observed to change with percentage conversion. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 891–895, 1998     

磁性半纤维素接枝聚丙烯酰胺水凝胶的制备及其性能研究

以半纤维素和丙烯酰胺为原料,利用自由基聚合法制备了多孔半纤维素接枝聚丙烯酰胺水凝胶,并且通过原位共沉淀法在凝胶上负载Fe3O4粒子,从而得到了磁性水凝胶。分别用FT-IR和SEM对水凝胶的结构和表面形态进行分析;考察了多孔半纤维素接枝聚丙烯酰胺凝胶的溶胀性能并对溶胀动力学进行了数学拟合。研究表明多孔半纤维素接枝聚丙烯酰胺水凝胶的平衡溶胀率随着交联剂量的增大而减小,随着半纤维素/丙烯酰胺比例的增大而增大,随着pH的增大而增大,水凝胶在pH=5.6的溶胀符合Schott溶胀动力学模型。振动样品磁强计(VSM)磁性能测试表明,磁性半纤维素接枝聚丙烯酰胺凝胶具有超顺磁性特征,其饱和磁化强度为10 emu/g。     

Synthesis and properties of radiation‐induced acrylamide–acrylic acid hydrogels

Acrylamide (AAm)/acrylic acid (AAc) hydrogels in the cylindirical form were prepared by γ‐irradiating binary systems of AAm/AAc with 2.6–20.0 kGy γ‐rays. The effect of the dose and relative amounts of AAc and pH on the swelling properties, diffusion behavior of water, diffusion coefficients, and network properties of hydrogel systems was investigated. The swelling capacities of AAm/AAc hydrogels were in the range of 1000–3000%, while poly(acrylamide) (PAAm) hydrogels swelled in the range of 450–700%. Water diffusion into hydrogels was found to be non‐Fickian‐type diffusion. Diffusion coefficients of AAm/AAc hydrogels were found between 0.79 × 10^?5 and 2.78 × 10^?5 cm² min^?1. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3570–3580, 2002     

Mechanical properties and drug release rate of poly(vinyl alcohol)/poly(ethylene glycol)/clay nanocomposite hydrogels: Correlation with structure and physical properties

Poly(vinyl alcohol)/poly(ethylene glycol) hydrogels containing curcumin as a drug and the various amounts of a montmorillonite nanoclay are prepared using the freezing–thawing method. Nanoclay quantity influence on the physicomechanical properties and the drug release rate of the hydrogel as well as relationship between them is investigated. X-Ray diffraction and Atomic force microscopy analysis reveal the nanoclays have an intercalation structure in the hydrogel, and the hydrogel crystallization decreases with increasing the nanoclay inclusion. From the SEM micrographs observation, it was revealed that due to the presence of the nanoclay in the hydrogel, its porosity decreased. The naonoclay has an amount-depended dual effect on the hydrogel swelling. The swelling mechanism is a normal Fickian diffusion for all the hydrogel samples. Strong physical interactions between the nanoclays and the polymer chains in the nanocomposite hydrogels are evidenced by the rheological studies. These interactions lead to significant reinforcement of the hydrogel tensile strength, intensified by the nanoclay amount. Interestingly, the nanoclays show the capability of accelerating and, also, decelerating the drug release of the hydrogel. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47843.     

Characterization of viscoelastic properties of polyacrylamide/Cr(III) hydrogels

Summary The viscoelastic properties of polyacrylamide/Cr(III) hydrogels were characterized with the help of oscillatory shear rheometer. The serrated-plate geometry rather than the cone-plate geometry was used in order to avoid the slip effect. The dynamic storage modulus (G') increased with increasing polyacrylamide and/or Cr(III) concentrations. The mean molecular weight of the chains adjoining adjacent crosslinks (M_c), calculated according to the elastic rubber theory, exhibited the same order of the primary polymer. G' decreased with increasing monovalent salt concentration, owing to the polyelectrolyte effect.