Viscoelastic behavior of highly crosslinked poly(acrylic acid)

The effects of crosslinking upon the dynamic mechanical properties and swelling behavior of poly(acrylic acid) (PAA) have been studied. Materials were prepared by the free radical copolymerization of acrylic acid with varying amounts of the tetrafunctional monomer allyl acrylate (ALA). The results indicated a linear dependence of the glass-transition temperature (T_g) on composition, T_g increasing by ～43°C over the mole fraction range X = 0?0.37 ALA. Room temperature (25°C) modulus values, as determined by both dynamic and compression methods, were inversely proportional to the initial concentration of ALA. The degree of network formation has been characterized in terms of the molecular weight between crosslinks M_c, and the influence of this parameter on the swelling ratio was discussed.     

Degradation behavior of hydrogel based on crosslinked poly(aspartic acid)

The degradation behavior of hydrogel based on poly(aspartic acid) (PASP) which crosslinked by 1, 6‐hexamethylene diamine (HD) was studied in α‐chymotrypsin solution. The degradation behaviors of PASP under different crosslinking levels were evaluated as a function of biodegradation time by monitoring the changes of crosslinking density, molecular weight, rheological behavior, interior morphology, mass loss, and swelling ratio. It was found that the degradation behaviors relied heavily on the crosslinking density which calculated from the Flory‐Rehner equation. A pseudo first‐kinetic equation was proposed to model the mass loss behavior and the degradation rate constant was calculated under different crosslinking levels. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermal decomposition behavior of poly[3,3-bis(ethoxymethyl) oxetane] and related polyethers

The thermal decomposition behavior of poly[3,3-bis(ethoxymethyl)oxetane] (polyBEMO) was examined and compared to the decomposition of poly(ethylene oxide) (PEO) and poly(tetramethylene oxide) (polyTHF). Differential scanning calorimetric (DSC) studies as a function of heating rates and at constant temperature as a function of time yielded activation energies of 45–50 kcal/mol, characteristic of polyether decomposition. First-order decomposition kinetics were found. The reaction is endothermic, with a heat of decomposition of 18.6 kcal/mol. Effusion mass spectroscopy on polyBEMO showed major peaks at 112, 140, 168, and 174 amu. A mechanism is proposed in which the thermal scission of the ether bonds in both the polymer chain and in the appendanges initiates the decomposition. The main decomposition reaction for polyBEMO can be written as where the appendages and main chain are cleaved in an unknown order.     

Removal properties of crosslinked poly(2‐acrylamido glycolic acid) for trace heavy metal ions: Effect of pH,temperature, contact time,and salinity on the adsorption behavior

Crosslinked poly(2‐acrylamido glycolic acid) resin was synthesized by radical polymerization. This resin contains three potential ligand groups and was studied as an adsorbent of trace heavy metal ions from a saline aqueous solution and sea water by using the Batch equilibrium procedure. Adsorption characteristics of the resin toward Cu(II), Ni(II), Cd(II), and Pb(II) were studied spectrophotometrically, both in competitive and noncompetitive conditions. The effect of pH, contact time, amount of sorbent, temperature, and salinity were studied. The resin showed a high affinity particularly for Ni(II). It was possible to remove completely Ni(II) and Pb(II) from the resin by 4M HNO₃. The retention properties of the resin were also investigated for Cu(II) contained in natural sea waters. The retention behavior was similar to that of the synthetic metal ion aqueous solution. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2614–2621, 2003     

交联淀粉微球对Co~(2+)的吸附行为及机理研究

研究了交联淀粉微球(CSM)对Co2+的静态吸附行为,并根据吸附等温线研究了吸附热力学性质,利用红外光谱仪、X射线衍射仪对吸附产物进行了结构表征,探讨了吸附机理。结果表明:在研究的浓度范围内,CSM对Co2+吸附等温线同时符合Langmu ir等温方程和Freund lich等温方程,不同温度下,CSM吸附Co2+的吸附焓变ΔH、吸附自由能变ΔG、吸附熵变ΔS均为负值,表明吸附是一个自发的、放热的过程,降低温度有利于吸附;CSM通过物理吸附、配位吸附方式吸附Co2+,并导致CSM结晶结构被进一步破坏。     

Adsorption of Cu2+ ions with poly(N‐isopropylacrylamide‐co‐methacrylic acid) micro/nanoparticles

Chelation efficiency of stimuli‐responsive poly(N‐iospropylacrylamide‐co‐methyacrylic acid) (PNIPAAm‐MAA) nanoparticles with Cu²⁺ ions from CuSO₄·5H₂O solution and from wood treated with copper‐based preservatives was studied. It was shown that particle size played a very important role in the adsorption process. The nano‐scale particles showed much improved Cu ion adsorption efficiency, compared with the micro hydrogels. The amount of Cu ion adsorption increased with increase of MAA ratio in copolymers and adsorption efficiency decreased with increased particle size. Furthermore, the adsorption amount varied with adsorption temperature at temperatures both below and above the corresponding low critical solution temperature (LCST). The high adsorption efficiency of Cu ions by PNIPAAm‐MAA polymer particles provides an effective technique for recovering metal ions (e.g., Cu²⁺) from wood treated with metal‐based preservatives. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Physicochemical study of the complexation of poly(acrylic acid) with Cu2+ ions in water

The complexation of poly(acrylic acid) (PAA) with Cu²⁺ ions in a dilute aqueous solution has been investigated as a function of the mixing molar ratio of the two species and the neutralization degree (i) of PAA by means of turbidimetry, viscometry, potentiometry, and ultraviolet–visible (UV–vis) spectrophotometry. Turbidimetry reveals that, for i > 0.1, phase separation takes place when the mixing ratio approaches the critical value of two carboxylate ions per Cu²⁺ ion, which is indicative of the formation of a 2 : 1 polymer/metal complex. This complex is very compact, as evidenced by the very low reduced viscosity values obtained just before phase separation. The variation of the fraction of complexed carboxylate anions and complexed Cu²⁺ ions can be followed as a function of the mixing ratio and i from the analysis of the potentiometric results for i < 0.5. Finally, the combination of the potentiometric and UV–vis spectrophotometric results supports the idea that both mononuclear and binuclear PAA/Cu²⁺ complexes are formed in an aqueous solution, depending on the mixing ratio and i. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Adsorption of Cu(II) ions from an aqueous solution by crosslinked amphoteric starch

The adsorption process of Cu(II) ions from aqueous solutions by crosslinked amphoteric starch with quaternary ammonium and carboxymethyl groups was investigated. The adsorption capacity was found to be dependent on the solution pH, the dose of the crosslinked amphoteric starch, and the initial concentration of Cu(II) ions. Moreover, the adsorption capacity increased with an increasing degree of substitution (DS) of the carboxymethyl groups. The adsorption followed a Freundlich adsorption isotherm. The adsorption process was endothermic, and the thermodynamic parameters were calculated at different DS values. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 728–732, 2004     

Methacryloylamidoglutamic acid functionalized poly(2-hydroxyethyl methacrylate) beads for UO22+ removal

A novel approach was developed to obtaining high uranium adsorption capacity utilizing 2-methacryloylamidoglutamic acid (MAGA) as a metal-complexing ligand. MAGA was synthesized by using methacryloyl chloride and glutamic acid. Spherical beads with an average size of 150–200 μm were obtained by suspension polymerization of MAGA and 2-hydroxyethyl methacrylate (HEMA) conducted in an aqueous dispersion medium. Poly(2-hydroxyethyl methacrylate–methacryloylamidoglutamic acid) [p(HEMA–MAGA)] beads have a specific surface area of 56.7 m²/g. p(HEMA–MAGA) beads were characterized by swelling studies, FTIR and elemental analysis. The p(HEMA–MAGA) beads with a swelling ratio of 63%, and containing 3.5 mmol MAGA/g were used in the removal of UO₂²⁺ from aqueous solutions. Adsorption equilibrium was achieved in about 120 min. The adsorption of uranium(VI) ions onto pHEMA was negligible (1.4 mg/g). The MAGA incorporation significantly increased the uranium adsorption capacity (204.8 mg/g). Adsorption capacity of MAGA incorporated beads increased significantly with pH and then reached the maximum at pH 6.0. Consecutive adsorption and elution operations showed the feasibility of repeated use for p(HEMA–MAGA) chelating beads.     

Aggregation behavior of poly(methacrylic acid) with cucurbit[7]uril and the effect of ammonia ions on aggregation

The interaction between poly(methacrylic acid) (PMAA) and cucurbit[7]uril (CB[7]) in aqueous solution were investigated by dynamic light scattering (DLS), fluorescence techniques, UV-spectrophotometer, and resonance light scattering (RLS). The experimental results show that the aggregates were formed between CB[7] and H⁺ of PMAA by the hydrogen bonding interaction that increases with increasing the concentration of CB[7], which leads to the formation of the larger aggregates. Interestingly, PMAA has temperature sensitivity with the addition of CB[7] by UV-spectrophotometer and DLS. The pH of the solution of PMAA appears a inflection point with increasing the concentration of CB[7] comparing with the increase of the electrical conductivity all the time with the addition of CB[7]. In addition, in order to investigate the effect of cation on the size of the aggregates and avoid the effect of other anions at the same time, the dilute ammonia was added into the solution of PMAA. The experimental data show that the size of the aggregates increases with adding CB[7] because CB[7] could combine with both NH₄⁺ by the electrostatic and iondipole interactions and H⁺ by the hydrogen bonding interaction, and a possible model is proposed to explain the host-guest interactions between PMAA and CB[7].     

Adsorption behavior of kenyaite for Cu2+ and Pb2+

Journal of Porous Materials - Hydrated layered polysilicates (HLPSs) have received considerable attention as adsorbents because of their selective adsorption for heavy metal cations. However, the...     

Complexation behavior of poly(acrylic acid) and lanthanide ions

The complexation behavior of PAA and lanthanide (Ln) ions was schematically investigated. As pH increased, the complexation between PAA and Ln ions will greatly strengthen because COO⁻ groups exhibit much stronger interaction with Ln ions than COOH. When the pH values are higher than 2.5, where the ionization of PAA is about 2.0%, the PAA–Ln complex would precipitate out from the solution. The precipitation is a direct indicator for the complexation between PAA and Ln ions. Besides pH values, the complex precipitation is related with the concentration, the molar ratio, and the operation procedure. At the extremely low concentration, there is no polymer–metal complex precipitation but fluorescence spectroscopy reveals that the complexation between PAA and Ln ions still exists when pH value is higher than 2.5. When the molar ratio of PAA and Ln ions exceeds the certain level, it would produce soluble polymer–metal complex, even at the high concentration of Ln ions.     

Synthesis and photodegradation of poly[2,5-bis(dimethylsilyl)thiophene]

Summary Poly[2,5-bis(dimethylsilyl)thiophene] (I), a copolymer with alternating thiophene and disilyl units, has been prepared by the Wurtz coupling of 2,5-bis(dimethylchlorosilyl)thiophene (IV) with sodium metal in toluene. I has been characterized by ¹H, ¹³C, and ²⁹Si NMR, IR, UV, GPC, TGA and elemental analysis. The photolysis of I in benzene/methanol solution results in degradation of the polymer. The structure of the photoproducts and possible mechanisms for their formation are discussed.     

Synthesis and photodegradation of poly[2,5-bis(dimethylsilyl)furan]

Summary Poly[2,5-bis(dimethylsilyl)furan] (V), a copolymer with alternating furan and disilyl units, has been prepared by the Wurtz coupling of 2,5-bis(dimethylchlorosilyl)furan (II) with sodium metal dispersion in toluene. Lower molecular weight poly[2,5-bis(dimethylsilyl)furan] (IV) has been prepared by a similar condensation reaction with 2,5-bis(dimethylfluorosilyl)furan (III). IV and V have been characterized by ¹H, ¹³C and ²⁹Si NMR, IR, and UV spectroscopy as well as by GPC, TGA and elemental analysis. Photolysis of V in a benzene/methanol solution results in degradation of the polymer.     

Crosslinked poly[acryloylN,N,-bis(2,2-dimethoxyethyl) amine] and crosslinked poly[acryloylmorpholine/acryloyl N,N,-bis(2,2-dimethoxyethyl) amine] gel networks and their application to the immobilization of β-d-glucosidase

The synthesis and homopolymerization of acryloyl N,N,-bis(2,2-dimethoxyethyl)amine is described. Gel networks were obtained by copolymerization of acryloyl N,N,-bis(2,2-dimethoxyethyl)amine and N,N,′-methylenediacrylamide (molar ratio 8:1) and by copolymerization of acryloyl morpholine, acryloyl N,N,-bis(2,2-dimethoxyethyl)amine and N,N,′-methylenediacrylamide (molar ratio 8:2:1). Following treatment of the gel networks with tartaric dihydrazide in dilute hydrochloric acid and subsequent activation with nitrous acid, conjugates of β-d-glucosidase were prepared. In both cases the immobilized enzyme was more resistant to heat denaturation than the native enzyme in solution. The nature of the polymer-enzyme linkage is discussed with reference to studies on the model compound phenylacetyl N,N-bis(2,2-dimethoxyethyl)amine.     

Synthesis and photodegradation of poly[1,4-bis(dimethylsilyl)naphthalene]

Summary Poly[1,4-bis(dimethylsilyl)naphthalene](I), a copolymer with alternating 1,4-naphthalene and disilyl units, has been prepared by the Wurtz coupling of 1,4-bis(dimethylchlorosilyl) naphthalene (II) or 1,4-bis(dimethylfluorosilyl)naphthalene (III) with sodium metal dispersion in toluene. The molecular weight distribution of I prepared from III is significantly higher than when I is prepared from II. I has been characterized by ¹H, ¹³C and ²⁹Si NMR, IR, UV, GPC, TGA and elemental analysis. Photolysis of I in benzene/methanol solution results in rapid degradation of I.     

2,2-二[4-(2-羟基乙氧基)苯基]丙烷在正丁醚中的合成研究

以双酚A和环氧乙烷为原料在三苯基膦的催化下合成了2,2-二[4-(2-羟基乙氧基)苯基]丙烷,研究了有无溶剂对反应产物组成的影响,并在正丁醚溶剂中研究了反应原料配比、溶剂用量和溶剂套用对反应选择性的影响。结果表明:无溶剂时反应产物较为复杂、副产物较多,反应选择性低,加入溶剂后,反应选择性明显增大,正丁醚中反应选择性较高。在正丁醚中,较佳的环氧乙烷与双酚A摩尔配比为2.3,较佳的正丁醚与双酚A质量比为1.25,溶剂可以多次套用,溶剂套用对反应选择性无明显影响。研究为开发2,2-二[4-(2-羟基乙氧基)苯基]丙烷的连续生产装置和工艺提供理论和实验基础。     

Aqueous solution properties of poly(trimethyl acrylamido propyl ammonium iodide) [poly(TMAAI)]

The aqueous solution properties of a cationic poly(trimethyl acrylamido propyl ammonium iodide) [poly(TMAAI)] were studied by measurements of reduced viscosity, intrinsic viscosity, and flocculation test. The reduced viscosity and intrinsic viscosity of this cationic polyelectrolyte were related to the types and concentration of added salt. “Soft” salt anions were more easily bound on the quaternary ammonium (R₄N⁺) of poly(TMAAI) than those of “hard” salt anions. Halide anions are hard anions; consequently, hard cations were more easily attracted to halide anions for reducing the binding degree of halide anion on the quaternary ammonium group (R₄N⁺). Some salt ions were observed to strongly attract the quaternary ammonium of the cationic polymeric side chain for coagulation of the polymers. This effect would make the polymeric aqueous solution become turbid. The intrinsic viscosity behavior for cationic polyelectrolyte resulting from the electrostatic repulsive force of the polymer chain is contrasted with polyampholyte. A comparison of various flocculants as to the effect of flocculation was also studied. © 1994 John Wiley & Sons, Inc.     

2，2-双[4-（3，4-二氨基苯氧基）苯基]六氟丙烷的合成及表征

以六氟双酚A与5-氯-2-硝基苯胺为原料,在N,N-二甲基甲酰胺中发生缩合反应,再经Pd/C催化剂还原合成了一种新型的六氟四胺,其结构分别用元素分析、IR和 1HNMR进行了表征.这种新型四胺由于引入了六氟丙基和氧原子,可以用于合成溶解性能良好的聚苯并咪唑.