Swelling behavior and pervaporation properties of new composite membrane systems: Porous polyethylene film‐poly(acrylic acid) hydrogel

A new type of composite membrane for pervaporation has been developed. These membranes were prepared by free‐radical copolymerization of acrylic acid with a macromolecular polyfunctional crosslinker (allylhydroxyethylcellulose) inside the porous polyethylene (PE) film. It was shown that the porous structure of the PE matrix is filled with poly(acrylic acid) (PAA), and a layer of acid is formed on the film surface. To investigate the effect of the porous matrix on the composite membrane properties, a hydrogel membrane of crosslinked PAA was also prepared without the matrix using the same procedure. PAA in both membranes was in the neutralized form (K⁺). Swelling behavior of the membranes and their separation characteristics for pervaporation were investigated in water–ethanol solutions depending on the ethanol concentration. All membranes exhibited a high degree of equilibrium swelling (Q = 20–50 g/g) in dilute ethanol solutions (0–30 vol %), and Q sharply dropped to 1.5–2 g/g at a EtOH concentration of 30–40 vol % due to collapse of the gel. All membranes under study were highly permeable and selective to water over a wide range of ethanol concentrations in the feed (50–96 vol %), but composite membranes had a higher separation factor due to the restriction effect of the matrix porous structure on swelling of PAA(K⁺) inside the pores. However, composite membranes were characterized by a lower permeation rate, compared to the crosslinked PAA membranes without a matrix, because of their lower effective surface for diffusion. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1461–1465, 2004     

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     

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.     

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     

Thermal properties of poly(maleic anhydride‐alt‐acrylic acid) in the presence of certain metal chlorides

Polychelates were synthesized by the addition of aqueous solutions of copper(II), cadmium(II), and nickel(II) chlorides to aqueous solutions of poly(maleic anhydride‐alt‐acrylic acid) [poly(MA‐alt‐AA)] in different pH media. The thermal properties of poly(MA‐alt‐AA) and its metal complexes were investigated with thermogravimetry and differential scanning calorimetry (DSC) measurements. The polychelates showed higher thermal stability than poly(MA‐alt‐AA). The thermogravimetry of the polymer–metal complexes revealed variations of the thermal stability by complexation with metal ions. The relative thermal stabilities of the systems under investigation were as follows: poly(MA‐alt‐AA)–Cd(II) > poly(MA‐alt‐AA)–Cu(II) > poly(MA‐alt‐AA)–Ni(II) > poly(MA‐alt‐AA). The effects of pH on the complexation and gravimetric analysis of the polychelates were also studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3926–3930, 2006     

Absorbency and adsorption of poly(acrylic acid‐co‐acrylamide) hydrogel

Poly(acrylic acid‐co‐acrylamide) (PAAAM) hydrogels have been prepared from partly neutralized acrylic acid (AA) and acrylamide (AM) by solution polymerization, and their absorbency and adsorption in both CuCl₂ and FeCl₃ solutions have been investigated. PAAAM hydrogels and their complexes with Cu²⁺ or Fe³⁺ have been characterized by FTIR. The absorbency of PAAAM in both CuCl₂ and FeCl₃ solutions increases initially and then decreases as the absorbing time increases. The adsorption of PAAAM in both CuCl₂ and FeCl₃ solutions can be described by the pseudo‐second order chemisorption kinetics proposed by Ho and McKay, and the equilibrium uptake of Cu²⁺ on PAAAM can well be fit with the Langmuir adsorption isotherm. However, the equilibrium uptake of Fe³⁺ on PAAAM increases as the initial Fe³⁺ concentration increases for Fe³⁺ concentration smaller than 5.625 × 10^?3 mol/L, and then decreases with Fe³⁺ concentration. The largest uptakes for Cu²⁺ and Fe³⁺ are 247 and 173 mg/g, respectively. The results also show that the uptake of Cu²⁺ and Fe³⁺ on PAAAM increases remarkably when pH of the solution is changed from 2.3 to 4.2 and from 1.0 and 2.1, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Novel approach in investigation of the poly(acrylic acid) hydrogel swelling kinetics in water

The swelling kinetics curves of structurally defined poly(acrylic acid) hydrogel in bidistilled water at temperatures: 25, 30, 35, 40, and 45°C were determined. The possibility of kinetically explaining the isothermal swelling process by applying the following models: reaction controlled by diffusion, first order chemical reaction kinetics, and second order chemical reaction kinetics, was investigated. It was found that kinetically explaining the swelling process using these methods was limited to only certain parts of the process. The swelling process in bidistilled water was described in full range assuming that the hydrogel's swelling rate was a kinetically controlled reaction by the rate of the movement of reactive interface of hydrogel. Based on that model, the kinetic parameters, activation energy (E_a) and preexponential factor (A), of the swelling process were determined to be E_a = 35 kJ/mol and lnA = 8.6. A possible mechanism of the investigated swelling process was discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Investigation of pH sensitivity of poly(acrylic acid‐co‐acrylamide) hydrogel

It was found that the upper critical solution temperature (UCST) of poly(acrylic acid‐co‐acrylamide) hydrogel decreases with increase in pH. The UCST of samples equilibrated in a buffer at pH 2.5 was 33.7 °C, whereas it shifted to below 0 °C when swollen in buffers above pH 10. FT‐IR showed that COOH group of acrylic acid ionized gradually in alkaline media. The morphology change of the hydrogel swollen in different buffers was studied by environmental scanning electron microscopy (ESEM). ESEM images showed that the pore size of the sample increased with increase in pH, and in strongly basic media the three‐dimensional network was replaced by a ‘sausage‐like’ or ‘desert‐like’ structure. A study of the pH‐dependent release of cefazolin sodium was also carried out. Copyright © 2003 Society of Chemical Industry     

聚对氨基苯磺酸/石墨烯复合膜修饰玻碳电极测定葡萄糖

制备了对氨基苯磺酸/石墨烯复合膜修饰电极,研究了葡萄糖在该修饰电极上的电化学行为.在0.1 moL/L NaOH溶液中,峰电流与葡萄糖的浓度在1 ×1O-6 ～5 ×1O-4 mol/L的范围内呈良好的线性关系,检出限为2×10-7 mol/L(S/N =3).实验结果表明对氨基苯磺酸/石墨烯复合膜显著提高了方法的检测...     

Biodegradable blends of high molecular weight poly(ethylene oxide) with poly(3‐hydroxypropionic acid) and poly(3‐hydroxybutyric acid): a miscibility study by DSC,DMTA and NMR spectroscopy

The miscibility of high molecular weight poly(ethylene oxide) blends with poly(3‐hydroxypropionic acid) and poly(3‐hydroxybutyric acid) (P(3HB)) has been investigated by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and high‐resolution solid state ¹³C nuclear magnetic resonance (NMR). The DSC thermal behaviour of the blends revealed that the binary blends of poly(ethylene oxide)/poly(3‐hydroxypropionic acid) (OP blends) were miscible over the whole composition range while the miscibility of poly(ethylene oxide)/poly(3‐hydroxybutyric acid) blends (OB blends) was dependent on the blend composition. OB blends were found to be partly miscible at the middle P(3HB) contents (25 %, 50 %) and miscible at other P(3HB) contents (10 %, 75 % and 90 %). Single‐phase behaviour for OP blends and phase separation behaviour for OB blends were observed from DMTA. The results from NMR spectroscopy revealed that the two components in the OP50 blend were intimately mixed on a scale of about 35 nm, while the domain sizes in the OB blend with a P(3HB) content of 50 % were larger than about 32 nm. © 2000 Society of Chemical Industry     

Effect of base‐deposited graphene oxide on the thermal stabilization of poly(vinyl chloride)

Graphene oxide was deposited in a base solution to form base‐deposited graphene oxide (bd‐GO) particles. The structure and properties of the bd‐GO particles were evaluated using transmission electron microscopy, powder X‐ray diffraction and X‐ray photoelectron, Fourier transform infrared, UV‐visible and fluorescence spectroscopies. The effect of the bd‐GO particles on the thermal stabilization of poly(vinyl chloride) (PVC) was investigated using the Congo red test and thermogravimetric analysis. The results showed that the thermal stability of PVC was greatly improved by the bd‐GO particles. Furthermore, this stabilization mechanism was investigated using UV‐visible spectroscopy and nitrogen adsorption–desorption isotherm analysis. It was found that the improvement of thermal stability was mainly related to the deactivation of thermally labile structural defects in the PVC chains by the carboxylate and alkoxide moieties of the basic groups in the bd‐GO particles, and the highly efficient adsorption of the bd‐GO particles with hydrogen chloride produced during PVC degradation. © 2015 Society of Chemical Industry     

Effect of crystallization on microstructure and mechanical properties of poly[(ethylene oxide)‐block‐(amide‐12)]‐toughened poly(lactic acid) blend

The effect of crystallization on the microstructure and mechanical properties of a poly[(ethylene oxide)‐block‐(amide‐12)] (PEBA)‐toughened poly(lactic acid) (PLA) blend was investigated. Annealing was used to govern the crystallization microstructure and hence the mechanical properties of the blend. Crystallization resulted in the morphology of the PLA component altering from a continuous amorphous phase to continuous crystalline phase. Moreover, as the crystallization of PLA proceeded, the degree of crystallinity, spherulite size and lamellar thickness increased, and the interlamellar and interspherulitic connections became weaker. These led to the large plastic deformation in the matrix during tension being suppressed, and cracks appeared easily under tensile load, which was favorable to fracture for the blend during tension and so a small elongation at break was obtained. However, the elongation at break for all the annealed specimens was higher than that for neat amorphous PLA, suggesting that PEBA still showed a toughening effect for PLA under annealing. © 2012 Society of Chemical Industry     

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     

Nonisothermal crystallization behaviors of poly(3‐hexylthiophene)/reduced graphene oxide nanocomposites

Poly(3‐hexylthiophene) (P3HT)/reduced graphene oxide (rGO) nanocomposites were prepared through in situ reduction of graphene oxide in the presence of P3HT. The nonisothermal crystallization behaviors of P3HT and P3HT/rGO nanocomposites were investigated by differential scanning calorimetry. The Avrami, Ozawa, and Mo models were used to analyze the nonisothermal kinetics. The addition of rGO remarkably increased the crystallization peak temperature and crystallinity of P3HT, but the crystallization half‐time revealed little variation. The crystallization activation energies were calculated by the Kissinger equation. The results suggested that rGO plays a twofold role in the nonisothermal crystallization of P3HT, that is, rGO promotes the crystallization of P3HT as nucleating agent, and meanwhile, it also restricts the motion of P3HT chains. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Poly(acrylic acid)–poly(vinyl alcohol) copolymers with superabsorbent properties

Biodegradable polyacrylates were produced by a series of novel copolymerization and/or crosslinking techniques using poly(vinyl alcohol) (PVA) moieties modified by the incorporation of olefinic structures. PVA was modified by a tosylation and/or detosylation reaction. The functionalized PVA was copolymerized and/or crosslinked with acrylic acid or its partially neutralized form to give crosslinked polyacrylates that could swell in water. Their swelling behavior was determined under load. Degradation studies were performed in α-chymotrypsin, trypsin, and papain solutions. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 817–829, 1998     

Enhanced oxygen‐barrier and water‐resistance properties of poly(vinyl alcohol) blended with poly(acrylic acid) for packaging applications

To enhance the oxygen‐barrier and water‐resistance properties of poly(vinyl alcohol) (PVA) and expand its food packaging applicability, five crosslinked poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) blend films were prepared via esterification reactions between hydroxyl groups in PVA and carboxylic acid groups in PAA. The physical characteristics of the blends, including the thermal, barrier, mechanical and optical properties, were investigated as a function of PAA ratio. With increasing PAA content, the crosslinking density was significantly increased, resulting in changes in the chemical structure, morphology and crystallinity of the films. The oxygen transmission rate of pure PVA decreased from 5.91 to 1.59 cc m^?1 day^?1 with increasing PAA ratio. The water resistance, too, increased remarkably. All the blend films showed good optical transparency. The physical properties of the blend films were strongly correlated with the chemical structure and morphology changes, which varied with the PAA content. © 2016 Society of Chemical Industry     

Calcium ion‐induced self‐healing pattern of chemically crosslinked poly(acrylic acid) hydrogels

Poly(acrylic acid) hydrogels crosslinked with N,N′‐methylenebisacrylamide were synthesized by free radical polymerization. Polymerization conditions had a significant influence over the gel content and swelling behaviour of the hydrogels. The incorporation of calcium ions led to the origin of a self‐healing feature. The self‐healing behaviour and mechanical performance of the hydrogels were systematically investigated. The hydrogels showed good tensile strength of 1 MPa and excellent stretchable behaviour where hydrogels regained instantaneously. Hydrogel pieces joined together to become an integrated matrix as soon as two cut pieces were brought in contact. The hydrogels possessed a marked healing efficiency of 97% within 6 h at room temperature without any external intervention. The results are explained in terms of the dynamic mobility of calcium ions within the dual‐crosslinked networks of the poly(acrylic acid) hydrogels. © 2017 Society of Chemical Industry     

Preparation of poly(tert‐butyl acrylate)‐poly(acrylic acid) amphiphilic copolymers via radiation‐induced reversible addition–fragmentation chain transfer mediated polymerization of tert‐butyl acrylate

Poly(tert‐butyl acrylate) (PtBA) is a versatile hydrophobic macromolecule usually preferred in the development of new materials for a host of applications. PtBA homopolymers with well‐defined structure and controlled molecular weight in a wide range were successfully synthesized via radiation‐induced reversible addition–fragmentation chain transfer (RAFT) polymerization in the presence of a trithiocarbonate type RAFT agent. The polymerization of tBA was performed under ⁶⁰Co γ‐irradiation in the presence of 2‐(dodecylthiocarbonothioylthio)‐2‐methylpropionic acid (DDMAT) as the RAFT agent in toluene at room temperature with three [tBA]/[DDMAT] ratios (400, 600 and 1000) and different irradiation times. Radiation‐induced polymerization of tBA displayed controlled free radical polymerization characteristics: a narrow molecular weight distribution (M_w/M_n ~ 1.1), pseudo first order kinetics and controlled molecular weights. The system followed the RAFT polymerization mechanism even at very low amounts of RAFT agent ([tBA]/[DDMAT] = 1000), and molecular weights up to 113 900 with narrow dispersity (Ð =1.06) were obtained. PtBA was further hydrolysed into different amphiphilic PtBA‐co‐poly(acrylic acid) (PAA) copolymers by low (27.5%) and high (77.3%) degrees of hydrolysis. The pH sensitivity of the two copolymers was investigated by dynamic light scattering at pH 2 and pH 9 (above and below the pK_a value of PAA) and their hydrodynamic diameters and zeta potential values were determined. © 2020 Society of Chemical Industry     

Swelling behaviour of poly(α‐hydroxyacrylic acid) gel

Poly(α‐hydroxy acrylic acid) (PHA) and poly(acrylicacid) (PAA) gels were prepared by irradiating the respective 15 wt% aqueous solutions with γ‐rays. Swelling ratios for PHA gel were measured as a function of pH and divalent cation (Mg²⁺, Ca²⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺) concentration C₂ in the external solution to provide a comparison with the results for PAA gels. It was found that the swelling ratio of PHA gel steeply increases between pH 2 and 4, followed by a gradual swelling in the higher pH region. The corresponding steep swelling of PAA gel was observed at pH 3–6. Cation specificity in the equilibrium swelling ratio at a lower C₂ value (1.0 × 10⁻³ M) was approximately consistent with the binding selectivity in the solution system. Typically, the swelling ratio of PHA gel in the presence of Ca²⁺ was significantly lower than in the Mg²⁺ system, while the difference was slight for PAA gel. The response of the swelling ratio to changes in pH and C₂ was analysed as a first order relaxation to estimate the time constants. The (de)swelling kinetics measured by both the pH and C₂ jump were qualitatively interpreted in terms of main‐chain stiffness and intermolecular hydrogen bonding in the respective polymers. © 2000 Society of Chemical Industry     

The preparation of microporous membranes from blends of poly(2,6‐dimethyl‐1,4‐phenylene oxide) and sulfonated poly(2,6‐dimethyl‐1,4‐phenylene oxide)

Poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) is a chemically resistant polymer and, therefore, an attractive material for the formation of membranes. However, membranes of unmodified PPO prepared by an immersion precipitation possess very low hydraulic permeabilities at the filtration processes. The membranes with higher hydraulic permeabilities can be prepared from sulfonated PPO and/or from blends of unsulfonated PPO and sulfonated PPO. In conclusion, the mechanism of the formation of membranes from blends of unsulfonated PPO and sulfonated PPO is suggested. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 161–167, 1999