Synthesis and characterization of new optically active polymers carrying calix[4]arene and amino acid units in the main chain and their binding properties towards toxic heavy metals

BACKGROUND: A series of novel optically active polymers containing upper rim calix[4]arene was prepared from the polycondensation reaction of calix diamine derivative 2 with two optically active diacid chlorides. RESULTS: The optically active compounds were prepared from the reaction of a pyromellitic dianhydride with two chiral amino acids. The optically active polymers were obtained in a yield of 80–86% and had an inherent viscosity of 0.20–0.26 dL g^?1. The polymers were characterized using Fourier transform infrared and ¹H NMR spectroscopy and elemental analysis. Studies of the complexation of the polymers towards some alkali metal and toxic transition metal cations were performed using solid–liquid sorption procedures and comparisons made with the starting monomer. CONCLUSION: It is evident from the complexation studies that the polymers investigated are good polymeric ionophores for alkali metal cations like Na⁺ and K⁺, for Ag⁺ and for toxic heavy metal cations such as Cu²⁺, Co²⁺, Cd²⁺ and Hg²⁺. These polymers are good candidates for use in chiral stationary phases for separation of enantiomers in ionic media, as well for removing metal ions. Copyright © 2009 Society of Chemical Industry     

Grafting of poly(acrylic acid) on polyamide yarn

Graft copolymerization of acrylic acid onto PA6 yarn was examined in this study. Prior to the grafting process, the fibers were activated with a benzene solution of benzoyl peroxide. Next, the fibers were put into a bath containing acrylic acid, a dispersing agent, and the activator of reaction. The effects of the main process parameters and auxiliary additives on the degree of grafting, quantity of the homopolymer formed during grafting, effectiveness of grafting, extent of conversion, and grafting ratio were determined. Using calculation factors such as the reaction efficiency, the extent of reaction, and the ratio of grafting, the conditions of grafting were found that made possible the reduction or elimination of the by‐product. Also determined were the influence of the degree of grafting on the moisture sorption and the swelling of modified fibers. In addition, the value of apparent activation energy was calculated (49.123 kJ/mol). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1914–1919, 2001     

Thermal behavior of poly(acrylic acid)–poly(vinyl pyrrolidone) and poly(acrylic acid)–metal–poly(vinyl pyrrolidone) complexes

Thermal analysis (TGA and DTA) of samples of PAA, PVP, PAA–PVP complexes, containing different weight fractions of PAA and ternary polymer–metal–polymer complexes, were studied. The activation energy parameters for the thermal degradation were also calculated. The study of the effect of FeCl₃, NiCl₂, and Ni(NO₃)₂ on the TGA and DTA curves of the complexes showed that the decompositions are dependent on the concentrations and the nature of the metal ions. The DTA traces of PAA–PVP complex containing FeCl₃, NiCl₂, and Ni(NO₃)₂ showed that the treatment of the complex with these metal ions causes considerable changes in the thermal decomposition of PAA–PVP complex. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4049–4057, 2006     

Characterization of polyelectrolyte effect in poly(acrylic acid) solutions

The viscometric behavior of poly(acrylic acid) solutions, as well as their ion transport properties, were monitored as a function of polymer concentration and the addition of KOH in nonisoionic conditions. Polyelectrolyte effect was studied and characterized by conductivimetry as well as viscometric properties at the infinite dilution limit. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 191–196, 2003     

Modification of polyester fibers by grafting with poly(acrylic acid)

The grafting of acrylic acid on PET using benzoyl peroxide has been investigated. The influence of the main parameters of grafting, the effect of additives on the degree of grafting, and the amount of homopolymer formed during the process have been determined. Futhermore, the values of apparent activation energy have been calculated. Also, the influence of the degree of grafting on the moisture sorption and swelling of modified fibers have been determined. By an additional treatment of the grafted fibers with antibiotics it is possible to provide the fibers with antibacterial properties. Liberation of antibiotics from fibers into solutions has been examined and mathematically described. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:967–977, 1997     

Glass polyalkenoate dental cements based on physical blends of poly(acrylic acid) and poly(vinyl phosphonic acid)

Physical blends of spray-dried poly(acrylic acid), PAA, with poly(vinyl phosphonic acid), PVPA, have been prepared and used in experimental dental cements by mixing them with basic sub-45 μm acid-degradable fluoroaluminosilicate glass powders and adding water. The effect of varying the ratio of PAA to PVPA, of altering the molar mass of PAA, and of using glasses of differing basicity have been investigated. The compressive strengths of the best of the cements formed from these blends were comparable to those formed from the individual polyacids, i.e. about 160 MPa.     

The intrinsic viscosity of poly(acrylic acid) and partially neutralized poly(acrylic acid) by isoionic dilution

The isoionic dilution method has been used to measure the intrinsic viscosity, [η], of a poly(acrylic acid) (PAA) sample as a function of neutralization degree, i, at low ionic strength, I = 1.0 × 10. The results obtained for the counterion activity are in close agreement with Manning's theory for counterion condensation. The influence of the ionic strength, I, on [η] and on the Huggins coefficient, k', was also examined and the exponents of the scaling laws relating these two parameters with I were found.     

Preparation of poly(acrylic acid)/poly(vinyl alcohol) membrane for the facilitated transport of CO2

Poly(acrylic acid) (PAA)/poly(vinyl alcohol) (PVA) membrane was prepared for the facilitated transport of CO₂. The carrier of CO₂ was monoprotonated ethylenediamine and was introduced in the membrane by ion exchange. The ion‐exchange capacity of the membrane was 4.5 meq/g, which was much higher than that of the Nafion 117 membrane. The membrane was highly swollen by the aqueous solution. Much higher selectivity of CO₂ over N₂ and higher CO₂ permeability were obtained in the PAA/PVA membrane than in the Nafion membrane because of the higher ion‐exchange capacity and solvent content. The highest selectivity was more than 1900 when the CO₂ partial pressure in the feed gas was 0.061 atm. Effects of ion‐exchange capacity, membrane thickness, and annealing temperature in conditions of membrane preparation on membrane performance were investigated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 936–942, 2001     

Study of the interaction of poly(acrylic acid) and poly(acrylic acid‐poly acrylamide) complex with bone powders and hydroxyapatite by using TGA and DSC

The thermo gravimetric analysis (TGA) and differential scanning calorimetric analysis (DSC) were used to study the thermal degradation of poly(acrylic acid) PAA and poly(acrylamide) PAAm as well as the compound obtained from their interactions. The examination of the thermal curves revealed that the characteristics of the curves of the compound resulting from the cooperative interactions are different from those of the constituent polymers. The differences in the characteristics of the thermal curves were attributed to the formation of an interpolymer complex resulting from the interaction of PAA with PAAm at low pH value. These two thermal techniques were also used to investigate the thermal behavior of the compounds obtained from the interaction of PAA and (PAA‐PAAm) mixture with bone powders (BP) and hydroxyapatite (HA). It was found that the TGA, DTG, and DSC curves do not show the peak of formation and degradation of PAA anhydride which provided strong evidence for the consumption of PAA in the reaction between the polymer and BP. The interaction between PAA and the thermally treated BPs and HA was investigated. Moreover the interaction between the mixture of PAA and PAAm at different pH values and the BPs and HA was discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Swelling behavior of chitosan/poly(acrylic acid) complex

This study investigates the improved swelling behavior of chitosan/poly(acrylic acid) complex by solvent (methanol, ethanol, and acetone) extraction. The complex is developed by photoinitiated free‐radical polymerization of acrylic acid in the presence of chitosan. The swelling ratio of the complexes depends on the cosolvency effect of poly(acrylic acid) to the extracted solvent, which in turn affects the polymer network structure and ionic states characterized by dynamic force microscopy (DFM), Raman, and FT‐IR spectroscopy. The DFM investigation displays the improved structural changes of the polymer network structure after solvent extraction and its relation to the improved swelling property of the chosen system in different environmental conditions (pH, solvent, and salt concentration) are discussed. A high swelling ratio of about 600 times its dry weight is observed in water as well as in low salt and solvent concentration after methanol extraction. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2930–2940, 2004     

Grafting of poly(acrylic acid) onto poly(amidoamine)-functionalized graphene oxide via surface-mediated reversible addition-fragmentation chain transfer polymerization

Graphene oxide was modified with third-generation poly(amidoamine) (PAMAM) to obtain dendrimer-grafted GO (DGO) with high content of functional groups. DGO's amine groups were conjugated with S-(thiobenzoyl)thioglycolic acid as proved by XPS and poly(acrylic acid) was grafted onto surface via RAFT polymerization (DGO@PAA). FT-IR results approved the synthesis of samples whereas TGA revealed 40.3% grafting of PAA. XRD patterns showed that with further modification, d-spacing increased. According to Raman spectra, modification resulted in more disordered structure whereas DGO@PAA showed a high value of I_D/I_G. Morphological studies were performed by SEM and TEM that showed a polymeric layer covered the surface of nanosheets.     

Interpolymer complexes of poly(acrylamide) and poly(N-isopropylacrylamide) with poly(acrylic acid): a comparative study

The interpolymer complexation, through successive hydrogen bonding, between poly(acrylamide) (PAAm) and poly(N-isopropylacrylamide) (PNiPAAm) with poly(acrylic acid) (PAA) in aqueous solution has been viscometrically and potentiometrically investigated. The stoichiometry of the complexes formed was determined. By comparing the strength of the two complexes the very important contribution of the hydrophobic interaction in their formation has been indicated.     

Absorption and desorption of chromium ions by poly(acrylic acid) gels

The ability of crosslinked poly(acrylic acid) gels to retain chromium species was studied as a function of pH. Chromium retention was found to increase with pH according to two mechanisms. In the low pH range where chromium species are soluble, retention occurs via ion‐binding in the whole volume of the gel. At higher pH where insoluble chromium hydroxide particles are formed, retention comes from an adsorption process at the surface of the gel. The desorption of chromium species under acidic conditions was also investigated and found to be very dependent on retention mechanism and aging time of the polymer–chromium complex. When retention occurs by ion‐binding, only partial desorption was achieved at very short aging time. In contrast, a very fast desorption was observed when retention occurs via adsorption at the surface of the polymer gel. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 455–466, 1999     

Poly(acrylic acid)-grafted magnetic nanoparticle for conjugation with folic acid

Poly(acrylic acid) (poly(AA))-grafted magnetite nanoparticles (MNPs) prepared via surface-initiated atom transfer radical polymerization (ATRP) of t-butyl acrylate, followed by acid-catalyzed deprotection of t-butyl groups, is herein presented. In addition to serve as both steric and electrostatic stabilizers, poly(AA) grafted on MNP surface also served as a platform for conjugating folic acid, a cancer cell targeting agent. Fourier transform infrared spectroscopy (FTIR) was used to monitor the reaction progress in each step of the syntheses. The particle size was 8 nm in diameter without significant aggregation during the preparation process. Photocorrelation spectroscopy (PCS) indicated that, as increasing pH of the dispersions, their hydrodynamic diameter was decreased and negatively charge surface was obtained. According to thermogravimetric analysis (TGA), up to 14 wt% of folic acid (about 400 molecules of folic acid per particle) was bound to the surface-modified MNPs. This novel nanocomplex is hypothetically viable to efficiently graft other affinity molecules on their surfaces and thus might be suitable for use as an efficient drug delivery vehicle particularly for cancer treatment.     

A study of blending and complexation of poly(acrylic acid)/poly(vinyl pyrrolidone)

Poly(acrylic acid) (PAA) and poly(vinyl pyrrolidone) (PVP) were chosen to prepare polymer complex and blends. The complex was prepared from ethanol solution and the blends were prepared from 1-methyl-2-pyrrolidone solution. DSC results show that the T_gs of the PAA/PVP blends lie between those of the two constituent polymers, whereas T_g of the PAA/PVP complex is higher than both blends and the two constituent polymers. TGA results show that degradation temperature, T_d, of PAA increases upon adding PVP in the blend, but thermal stability of the complex is higher than that of the blends as reflected by the higher T_d. Both FTIR and high-resolution solid state NMR show strong hydrogen bonding between PAA and PVP by showing significant chemical shift. The T_1ρ(H) measurement shows that the homogeneity scale for the blend is at ∼20 Å and that for the complex is ∼15 Å.     

Drug release behavior of electrical responsive poly(vinyl alcohol)/poly(acrylic acid) IPN hydrogels under an electric stimulus

The electrically modulated properties of interpenetrating polymer networks (IPN) composed of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAAc) under electric field were investigated for drug delivery systems. PVA/PAAc IPNs with various compositions were synthesized by a sequential method, that is, ultraviolet polymerization of AAc in the mixture of PVA and aqueous AAc monomer solution, followed by a freeze‐thawing process to prepare elastic hydrogels. The amount of loaded drug significantly increased with the content of PAAc containing ionizable groups in IPN. The amount of introduced ionic drug (cefazoline) was greater than that of the nonionic drug (theophylline). Release behaviors of drug molecules from negatively charged PVA/PAAc IPN were switched on and off in a pulsatile pattern depending on the applied electric stimulus. The released amount and the release rate of drug were influenced significantly by the applied voltage, ionic group contents in IPN, ionic properties of drug solute, and the ionic strength of release medium. In addition, the ionic properties of drug molecules dramatically affected release behaviors, thus the release of ionic drug was much more enhanced than that of the nonionic drug. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1752–1761, 1999     

聚丙烯酸/丙烯酰胺高吸水性树脂吸附性能

用反相悬浮聚合法合成了聚丙烯酸/丙烯酰胺高吸水性树脂(PAAAM),讨论了其吸附CuCl₂、NiCl₂、CoCl₂溶液中金属离子的性能,考察了溶液pH值和初始浓度对金属离子吸附的影响。结果表明,PAAAM在不同pH值及浓度区间,对金属离子的吸附能力有较大差异,可被用于Cu(II)、Ni(II)、Co(II)的分离。同时还探讨了PAAAM在混合金属离子溶液中的吸附性能及反复利用的可能性,发现在混合溶液中PAAAM表现出对Cu（II）有较好的选择性吸附能力;4次循环后对Cu(II)、Ni(II)、Co(II) 离子的吸附量为最大吸附量的80%以上,重复使用效果理想。     

Synthesis and characterization of fluorocarbon‐containing,hydrophobically associative poly(acrylic acid‐co‐Rf‐poly(ethylene glycol) macromonomer)

Fluorocarbon‐ or hydrocarbon‐end‐capped poly(ethylene glycol) (PEG) macromonomers were prepared with coupling methods. Several factors affecting the synthesis were studied, and the optimal condition was ascertained. The critical micelle concentrations of these macromonomers were determined with the fluorescence method. Novel fluorocarbon‐containing, hydrophobically modified, alkali‐soluble copolymers were made by the copolymerization of fluorocarbon‐ or hydrocarbon‐alkyl‐end‐capped PEG macromonomers with acrylic acid in an organic solvent. The effects of the macromonomer contents, polymerization conditions, spacer, temperature, shear rate, pH, and addition of salt and various surfactants on the solution viscosity were preliminarily investigated. A very strong hydrophobic association was found for these copolymer solutions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1035–1047, 2002; DOI 10.1002/app.10393     

Electrospun crosslinked poly(acrylic acid) fiber constructs: towards a synthetic model of the cortical layer of nerve

In an attempt to mimic properties of the polyanionic nanofibrous cortical layer (ectoplasm) of nerve, tube‐shaped poly(acrylic acid) (PAA) nanofiber constructs were prepared via electrospinning. The influence of processing parameters on the morphology of the electrospun PAA nanofibers was systematically investigated. Smooth and uniform PAA nanofibers with average fiber diameter of 820 nm were produced at a concentration of 4 wt% with a flow rate of 0.8 mL h^?1 when a high voltage of 15 kV was applied. Water‐stable PAA nanofibers were obtained by thermally crosslinking PAA with ethylene glycol. The resulting tubes were neutralized to the sodium polyacrylate form and were shown to undergo reversible and abrupt length changes upon titration with CaCl₂ followed by titration with sodium citrate. The sharpness of the length transition was found to be highly dependent upon the bathing NaCl concentration and the operation temperature. It is suggested that electrospun PAA may be a promising candidate as a key element of an abiotic macromolecular mimic of selected properties of axons. © 2014 Society of Chemical Industry     

Crosslinking reaction of poly(vinyl alcohol) with poly(acrylic acid) (PAA) by heat treatment: Effect of neutralization of PAA

The crosslinking reaction of poly(vinyl alcohol) (PVA) by esterification using poly(acrylic acid) (PAA) as a crosslinking reagent was investigated to obtain highly insoluble PVA materials. Blend films of PVA and PAA (PVA/PAA = 8/2) were prepared to examine the effect of degree of neutralization (DN) in PAA and heat‐treatment conditions on the degree of crosslinking reaction. The degree of crosslinking reaction varied significantly when the DN of PAA changed. The optimum DN for the crosslinking reaction was in the range of 5 to 10 mol %. In the case of unneutralized PAA, the degree of crosslinking reaction was at most 15 mol % by heat treatment for 20 min at 200°C. Applying partially neutralized PAA (DN = 10 mol %) raised the degree to about 40 mol % under the same heat‐treatment conditions. FTIR analysis revealed that the hydroxyl group of PVA in the film blended with unneutralized PAA was degraded to a greater degree than that with partially neutralized PAA as a result of heat treatment. It was found that heat treatment at a low pH condition enhances the degradation of the hydroxyl group of PVA, resulting in a decrease of the number of crosslinking sites by esterification. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2420–2427, 2003