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.     

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.     

Dextran/poly(acrylic acid) mixtures as miscible blends

Bioartificial polymeric materials based on blends of dextran and poly(acrylic acid) were prepared in form of films and characterized in order to evaluate the miscibility of the natural component with the synthetic one. Films with different composition ratios were prepared by solution casting and analyzed by dynamic mechanical-thermal analysis, differential scanning calorimetry, and scanning electron microscopy. The obtained results indicate that dextran is miscible with poly(acrylic acid). The miscibility was mainly ascertained on the bases of the occurrence of a single composition-dependent glass transition temperature in each blend and also on the bases of the transparency and homogeneity of the films. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2089–2094, 1997     

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     

Formation of polymer-polymer complexes and blends in the system poly(acrylic acid)-poly(vinyl methyl ether)

The formation of a 1:1 polymer-polymer complex from poly(acrylic acid) and poly(vinyl methyl ether) has been detected by viscosity measurements in aqueous solution, and the glass transition temperature of the isolated complex has been determined. Infrared spectroscopy indicates that specific hydrogen bonding occurs between the components of the complex. Miscible blends of the two polymers can also be formed (at all compositions) and, although hydrogen bonding occurs, the structures of the blends are likely to be dissimilar to that of the complex.     

基于双硫键和氢键协效的高性能自修复聚氨酯脲的研制

为解决自修复弹性体同时具有优异的力学性能和自修复性能的矛盾,首先将原料胱氨酸（CYS）进行甲酯化得到含双硫键的二胺扩链剂胱氨酸二甲酯（CDE）,然后以聚四氢呋喃醚二醇（PTMG）为软段,异佛尔酮二异氰酸酯（IPDI）和CDE为硬段,固定摩尔比为1∶3∶2,采用两步法制备了自修复聚氨酯脲（SH-PUU）弹性体,并对SH-PUU进行了红外光谱测试、拉曼光谱测试、力学性能测试、自修复性能测试、划痕修复微观形貌观察、应力松弛和动态力学性能测试。实验结果表明：SH-PUU的软段和硬段的玻璃化转变温度分别为-38.5℃和77.6℃,微相分离程度较高,SH-PUU具有良好的力学性能,拉伸强度为13.6MPa,断裂伸长率达531.3%;同时SH-PUU具有高效的自修复能力,试样在经过80℃修复2h后,基于拉伸强度的自修复效率达到97.1%,SH-PUU的力学性能和自修复性能达到较好的平衡。SH-PUU的高自修复能力是由动态双硫键和氢键协效增强引起的,其通过加热方式的自修复机理为：SH-PUU中的动态双硫键在80℃发生可逆交换反应,SH-PUU中的氢键在低于100℃时会重新形成。     

Bioartificial materials based on blends of collagen and poly(acrylic acid)

The interactions between soluble collagen (C) from calf skin and poly(acrylic acid) (PAA) were studied. Mixing aqueous solutions of collagen and PAA, at various pH values (2.5–4), leads to the formation of complexes that precipitate in the form of insoluble aggregates. The effects of mixture composition, pH, and ionic strength on C/PAA complex formation were investigated by gravimetric, turbidimetric, and conductometric analysis. The experimental results indicate that the complexes form through electrostatic interactions. Homogeneous solid films with variable C/PAA ratios were obtained by casting from solutions in which the pH was adjusted just over the isoelectric point of collagen, thus avoiding the attractive ionic interactions responsible for the complexation of collagen and PAA molecules. A relevant result obtained is related to the possibility of restoring the ionic interactions between the two polymers inside the solid films. Mixture composition and pH appear to influence the thermal properties of both complexes and films. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 971–976, 1999     

Synthesis and characterization of chitosan/poly(acrylic acid) polyelectrolyte complex

Polyelectrolyte complex based on chitosan and acrylic acid monomer by photoinitiated free‐radical polymerization in the absence of crosslinker showed a large transition in swelling in response to changes in pH of surrounding medium. Their ability to swell arises from polyelectrolyte interactions and molecular structure of the complex. The main properties of interest that related to the molecular structure, swelling volumes, glass transition temperature, and elastic modulus of the complex were investigated. The effect of water content, the only variable in the sample component, played an important role in molecular structure of the complex and as a consequence, the extent of intermolecular linkage, especially amide bonds which in turn governed the degree of swelling of the polyelectrolyte complex in this study. The decreased degree of swelling and higher temperature shift of glass transition temperature was found with increased water content, whereas increased modulus of elasticity of dry complex was found in lower water content of synthesis component. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1025–1035, 2002     

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     

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.     

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     

Liquid crystallization of poly(styrene‐co‐maleic anhydride) induced by intermolecular hydrogen bonds

The liquid crystallization of general polymer (GP) with maleic anhydride in the main chain has been realized through molecular recognition and self‐assembly based on intermolecular hydrogen bonds. Poly[styrene‐co‐(N‐4‐carboxylphenyl)maleimide] (SMIBA) was synthesized by imidization and dehydration of Poly(styrene‐co‐maleic anhydride) (SMA) with p‐aminobenzoic acid (ABA) for use as an H‐bonded donor polymer. 4‐Methoxy‐4′‐stilbazole (MSZ) and 4‐nitro‐4′‐stilbazole (SZNO₂) were prepared as an H‐bonded acceptor. SMIBA was complexed with MSZ or SZNO₂ by slow evaporation from pyridine solution to form a self‐assembly, which exhibits the mesophase, while neither of the individual components is mesogenic. The phase diagrams of a variety of mixtures between of SMIBA and stilbazoles have been established using DSC and POM. They show complete miscibility and high thermal stability of the liquid crystalline phase over the whole composition range. The tuning of liquid crystalline properties was achieved by changing the composition of the mixture and involving it with a mixture of SZNO₂ and MSZ. IR measurements strongly support the existence of an H‐bonded complex between the carboxylic acid of SMIBA and the pyridine group of stibazoles. Unlike conventional side‐chain liquid crystalline polymer (SLCP), supramolecular SLCP with a lower molecular weigh polymeric donor has higher thermal stability of the liquid crystalline phase due to the microphase separated in the hydrogen bonding case. Liquid crystallization of GP, such as SMA, induced by hydrogen bonds, offers a new route to prepare functional material with controlled molecular architecture from readily accessible and simpler precursors. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 97–105, 1999     

Electrically conducting polyaniline–poly(acrylic acid) blends

We report an electrically conducting polyaniline–poly(acrylic acid) blend coatings prepared by mixing the emeraldine base (EB) form of polyaniline (PANI) and poly(acrylic acid) (PAA) aqueous solution. The samples show a moderate electrical conductivity σ. If they are immersed in an HCl aqueous solution, the conductivity of the samples is increased by two or three orders of magnitude and their thermal stability is also improved. Optical transmittance spectra show a complete protonation of PANI–PAA blends after immersion in HCl aqueous solution. Fourier transform infrared spectroscopy studies indicate that the better thermal stability of σ could come from the more stable protonated imine nitrogen ions. A low percolation threshold phenomenon is observed in PANI–PAA blends, from a strong interaction between the carboxylic acid groups of PAA and the nitrogen atoms of PANI. © 1998 SCI.     

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     

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.     

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     

Siloxane-modified poly(acrylic acid) synthesized in supercritical CO2

Copolymerization of acrylic acid and 3-[tris(trimethylsilyloxy)silyl]propyl methacrylate (TMSPMA) in supercritical carbon dioxide was successfully carried out. The products were obtained in the form of dry white powder with diameter about 0.2 μm. Viscosities of 2% aqueous solution of the copolymers dramatically increased as the content of TMSPMA in the copolymer increased and it was much higher than that of poly(acrylic acid). In addition, the viscosity of the copolymers showed a strong dependence on pH with a maximum at pH 5.0, which is due to the cooperation of intermolecular association and electrostatic repulsion.     

Interpenetrating polymer networks based on poly(acrylic acid) and gelatin. I: Swelling and thermal behavior

This article describes the synthesis of full and semi-interpenetrating polymer networks (IPNs) based on poly(acrylic acid) and gelatin as polymers 1 and 2, which were crosslinked sequentially using N,N′-methylene bisacrylamide (B_Am) and glutaraldehyde, respectively. Various samples were prepared by taking varying amounts of acrylic acid and gelatin in the initial feed. Sequential IPNs were prepared by first polymerizing and crosslinking acrylic acid in the presence of gelatin using redox initiators (ammonium persulphate and sodium metabisulphite) and B_Am as a crosslinking agent. Gelatin present in the firm gels was then crosslinked using 4% glutaraldehyde. Characterization of these gels was done by measuring their swelling behavior as a function of pH, temperature, and time. Percent swelling increased with increasing amounts of acrylic acid. The swelling ratio was also determined in the pH range of 1 to 12. Acid/alkali or buffers were used for maintaining pH. A significant increase in the percent swelling was observed when pH of distilled water was above 10. On the other hand, in the case of buffer, the swelling ratio increased with increasing the pH, and a maxima was observed at pH 8.4. A further increase in pH resulted in a decrease in the swelling ratio. Thermal and morphological characterization was done using thermogravimetric analyzer and scanning electron microscopy, respectively. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 217–227, 2001     

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.     

A supramolecular structured complex of poly(acrylic acid) and polystyrene‐block‐poly(vinylbenzyltrimethylammonium chloride)

Complexation of poly(acrylic acid) (PAA) by polystyrene‐block‐poly(vinylbenzyltrimethylammonium chloride) (PS‐b‐VB) results in a mesomorphously ordered material with a glass transition temperature of 71 °C. The complex is assumed to consist of hexagonally‐ordered ion‐rich cylindrical rods containing the PAA embedded in a polystyrene matrix. It has been shown by small‐angle X‐ray scattering (SAXS) analysis that the mesophase is characterized by sharp phase boundaries between ionic and non‐ionic regions. The structure parameters are evaluated by using a two‐dimensional interface distribution function resulting in an average cylinder radius in the range 3.0–3.5 nm and a lattice constant of 14 nm. The radius distribution is calculated to be relatively broad, which is found to be consistant with sharp phase boundaries. PS‐b‐VB‐PAA represents an example of a new type of polymeric hybrid material with a supramolecular ordered ionic–non‐ionic nanostructure. © 2000 Society of Chemical Industry