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.     

Formation of interpolymer complexes between poly(monoethyl itaconate) and poly(N-vinyl-2-pyrrolidone)

This paper reports on the interpolymer complex formation and polymer blends between poly(monoethyl itaconate) (PMEI) and poly(N-vinyl-2-pyrrolidone) (PVP). The formation of the interpolymer complex was found to depend upon the solvent medium. Stoichiometry of the complexes prepared from methanol solutions, as calculated from elemental analysis, is close to 1 : 1. Specific interactions of PMEI/PVP complexes and blends of these polymers have been characterized by FTIR. Strong hydrogen bonding for complexes and blends has been found. A calorimetric study of the complexes and blends has been performed over a wide temperature range.     

Decolorization of colored poly(ethylene terephthalate) bottle flakes using hydrogen peroxide

A novel process for the oxidative decolorization of green and blue colored poly(ethylene terephthalate) (PET) bottle flakes, using an aqueous solution of hydrogen peroxide (H₂O₂) has been developed. A strong dependence of H₂O₂ concentration and temperature on decolorization rate has been found. The decolorized flakes were characterized for color and intrinsic viscosity (IV) values; decolorized flakes exhibit color values similar to those of colorless recycled PET. The IV of peroxide bleached PET flakes indicated a decrease in PET molecular weight, which correlated with the severity of decolorization conditions. Despite decreases in PET IV values, the bleached flake still exhibited useful PET molecular weights. The consumption of H₂O₂ during the bleaching process was quantified titrating residual peroxide with a standardized potassium permanganate solution. H₂O₂ consumption rates of 0.3–0.9 g per gram of green PET flake were measured, depending on the specific bleaching conditions used. © 2007 Wiley Periodicals, Inc. JAppl Polym Sci, 2008     

Morphological and thermal characterization of interpolymer complexes and blends based on poly(acrylic acid) and hydroxypropylcellulose

Interpolymer complexes and blends were prepared based on poly(acrylic acid) and hydroxypropylcellulose. The structural features of polycomplexes and blends were evaluated by scanning electron microscopy and thermal analysis. It was found that the interpolymer complex obtained as a result of co‐precipitation of the polymeric components is characterized by an uniform structure which indicates the complete miscibility between the components. Films were prepared based on blends of neutralized poly(acrylic acid) and hydroxypropylcellulose. In this case the two components resulted immiscible because of the lack of intermolecular hydrogen bonding. Copyright © 2004 Society of Chemical Industry     

氨肟化反应中影响双氧水分解因素浅析

本文对环己酮氨肟化反应体系中引发H2O2分解的因素进行了研究,针对各种影响因素提出控制H2O2分解的优化措施。结果表明：在氨肟化反应体系中,NH3过量导致的碱性环境、H2O2过量加入或H2O2浓度过高以及氨肟化反应不完全,是引起H2O2分解的主要原因;反应温度、反应压力等操作条件的变化也可改变H2O2的分解速度;微量的锰、锌、铜、铁、镍等金属离子的存在,也会大大加速H2O2的分解。控制适当的NH3浓度及酮/H2O2摩尔比、反应条件以及降低金属离子含量有利于提高H2O2的有效利用率,这些结果可以为优化氨肟化反应工艺、降低H2O2消耗提供依据。     

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     

嵌段聚醚酯弹性纤维的老化及热分解

通过测定以PBT为硬段 ,聚乙二醇 (PEG)和聚丁二醇 (PTMG)为软段的嵌段聚醚酯弹性纤维在老化前后的特性粘数、断裂强度、断裂伸长率和弹性回复率的变化 ,发现添加抗氧剂能明显改善该弹性纤维的抗老化性能并提高纤维的力学性能和回弹性能 ;采用热失重测定了PBT -PTMG2嵌段聚醚酯弹性纤维的热分解性能 ,热分解动力学计算表明其热分解活化能较低 ,为 69.6kJ ,容易热分解 ,热分解为 1级反应     

烷基多苷的过氧乙酸漂色及组合漂色工艺研究

对烷基多苷(APG)的过氧乙酸(CH3COOOH)漂色工艺进行了优化,优化条件是:烷基多苷(APG)水溶液的浓度为50%,CH3COOOH用量为5%,漂色时间90 m in,漂色温度80℃,初始pH 12~12.5。在此条件下漂色,可使APG水溶液的消光系数由6~7降至0.4左右;采用质量分数分别为3%的H2O2与CH3COOOH组合漂色,可使漂色效果进一步提高;对H2O2与CH3COOOH漂色前后的APG样品进行了红外光谱对比分析。     

pH值对双氧水绝热分解特性的影响

为了考察pH值对双氧水热危害的影响,利用VSP2绝热量热仪对pH值分别为1.8,4,5,6,7及8的质量分数为27.5%的双氧水进行了绝热条件下测试,得到了不同pH值双氧水的绝热分解特征,求得了双氧水的分解动力学,并计算得到双氧水在起始温度为30℃时绝热条件下到达最大反应速率所需时间。结果表明:当双氧水pH值增加时,起始放热温度降低,到达最大反应速率所需时间缩短,热失控危险性明显增加,双氧水在工业条件下存储时,当pH值增加至6时就有一定危险性,当pH值增加至7以上时热失控几乎不可避免。     

Interactions between poly(acrylamide)–poly(itaconic acid) and cerium(IV)–nitrilotriacetic acid redox pair in the synthesis of acrylamide and itaconic acid homo‐ and copolymers

Homopolymers of itaconic acid (PIA) and its copolymers with acrylamide (P(IA‐AAm) were synthesized using ceric ammonium nitrate (NH₄)₂Ce(NO₃)₆ in combination with nitrilotriacetic acid (NTA) as redox initiator, and potassium persulphate at pH 1. The chain structures of the resulting products have been studied by FTIR spectroscopy. It is concluded from a comparison of spectroscopic results with gravimetric and viscometric data that the depressions in the yields and viscosity numbers in the case of Ce(IV)–NTA redox pair result from interactions between the constituents of the redox initiator and IA. Spectra of the insoluble and pale yellow precipitates, which are formed during the first 4 h of the reaction, after addition of Ce(IV) solution to the NTA and NTA–IA homogeneous solutions, also indicate the presence of various oxidation products. Furthermore, it is observed that H‐bonded homopolymer complex obtained from PAAm–PIA blends, prepared from aqueous solutions containing equal unit moles of each polymer, contain both ordered and defective structures. © 2001 Society of Chemical Industry     

Sintered metal fibers coated with transition metal oxides as structured catalysts for hydrogen peroxide decomposition

This study aimed at the development of active and stable structured catalyst for the decomposition of hydrogen peroxide under industrial conditions. Sintered metal fibers of stainless steel (SMF_SS) in the form of flat panels were surface coated by different catalytic metal oxides. The oxide coating has been carried out by incipient wetness impregnation of SMF_SS with suitable precursors followed by calcination in air at temperatures between 500 and 600 °C. The coating of SMF_SS renders a very thin homogeneous oxide layer of less than 1 μm covering the individual fibers and ensures an optimal accessibility of the treated H₂O₂ solution to the catalytically active phase without any mass-transfer limitations. In the decomposition of hydrogen peroxide, the 5 wt.% MnO_x/5 wt.% (Al₂O₃ + MgO)/SMF_SS was found to be the most active and stable catalyst in a range of pH = 4–7 at 25 °C exhibiting a significant first order rate constant of 5.2 min⁻¹ at pH 7. The same catalyst was tested in the back end of the epoxidation of soybean oil process demonstrating its suitability for industrial application.     

Synthesis and characterization of coordination polymers of Hg(II) with poly(thiooxamides)

Coordination polymers of Hg(II) with dithiooxamide, poly(ethylene thiooxamide), poly(butane thiooxamide), and poly(hexane thiooxamide) have been synthesized. All coordination polymers are solid compounds insoluble in common organic solvents. Coordination polymers have been characterized by elemental analysis, IR spectra, and thermogravimetric analysis and structures have been proposed leading to coordination of metal through S alone as well as N and S both. Thermal stability of the polymers has also been discussed.     

Synthesis and characterization of waterborne polyurethane emulsions based on poly(butylene itaconate) ester

Waterborne polyurethane (WPU) prepolymer was synthesised by the reaction of poly(butylene itaconate) ester (PBI, Mn = 1109 g/mol), 1,6-hexanediol, dimethylol propionic acid (DMPA), 2,4-toluene diisocynate (TDI), hydroxyethyl acrylate (HEA), and absolute ethanol as blocking agent, triethylamine as neutralizer. Cross-linked WPU was synthesized by trimethylolpropane (TMP) as crosslinker. The influences of PBI, DMPA, and TMP content on WPU emulsions and films were investigated. The structure of WPU was determined by Fourier transform infrared (FTIR) spectra, thermal properties and glass transition temperature of WPU films were determined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively, and morphology of the emulsion particles was observed by transmission electron microscopy (TEM). Through TGA, the heat resistance of the cross-linked WPU film was better than WPU film. By DSC analysis, glass transition temperature of cross-linked WPU film (21 °C) was higher than WPU film (10 °C).     

有机磷酸稳定剂对双氧水绝热分解特性的影响

为研究有机磷酸稳定剂对双氧水的作用,利用绝热量热仪VSP2（vent sizing package 2）进行了不同浓度的氨基三亚甲基膦酸（ATMP）分别与纯双氧水以及含0.01% Fe3+的双氧水的放热测试,得到其在绝热条件下的热力学参数,并在此基础上计算出样品在起始温度为25℃时到达最大温升速率的时间TMRad。结果表明：有机磷酸稳定剂能有效抑制温度、Fe3+对双氧水的催化分解作用,降低双氧水发生热失控的风险。双氧水的起始分解温度T0随着ATMP质量分数的增加而提高。在质量分数为0.04% ATMP的影响下,双氧水的起始分解温度T0可由50℃提高至115℃。     

氢氧直接合成过氧化氢用催化剂的研究进展

过氧化氢（H₂O₂）是一种高效的绿色氧化剂,广泛应用于化学品合成、印染纺织、污水处理等领域。近年来,氢氧直接合成过氧化氢作为一种简单、环保、原子效率高的合成方法,成为一大研究热点。本文系统性地介绍了近年来氢氧直接合成过氧化氢催化剂的催化反应机理,负载金属的不同结构和性质对直接合成过氧化氢的催化性能与作用机理,重点讨论了与催化剂载体相关的载体结构、载体酸性、载体添加物、载体与金属相互作用等方面对反应活性和选择性的影响。最后对比了近年来直接合成过氧化氢用催化剂的催化性能,认为合成高选择性、高产率的催化剂仍是未来直接合成过氧化氢工业化应用的发展方向。     

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     

Characterization of composite membrane of poly(vinyl alcohol) and regenerated silk fibroin for immobilization of horseradish peroxidase and an amperometric neckelocene-mediated sensor sensitive to hydrogen peroxide

Horseradish peroxidase (HRP) was effectively entrapped in a novel composite membrane of poly(vinyl alcohol) and regenerated silk fibroin. IR spectroscopy was employed to characterize the structure of the composite membrane and scanning electron microscopy was used to visualize the morphology of the composite membrane. HRP was utilized to amplify the amperometric response of the sensor by catalyzing reduction of hydrogen peroxide via nickelocene, an electron transfer mediator between immobilized HRP and a glassy carbon electrode. The influence of various experimental parameters such as pH, temperature and applied potential were explored for optimum analytical performance. The sensor possessed a variety of characteristics including good sensitivity, rapid response time and a low detection of limit of 0·1 μmol dm⁻³, which arose from the efficiency of electron transfer between immobilized HRP and the electrode via nickelocene.     

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.     

Degradable poly(ester amine) based on poly(ethylene glycol) dimethacrylate and polyethylenimine as a gene carrier

Degradable poly(ester amine) (PEA) based on poly(ethylene glycol) dimethacrylate (PMEG) and polyethylenimine (PEI) were synthesized by Michael addition reaction. The ratios of PEI to PMEG in PEAs were 0.99, 1.02, and 1.07 with corresponding number‐average molecular weight of 1.3 × 10⁴, 1.2 × 10⁴, and 0.9 × 10⁴, respectively. Degradation rate of PEA at pH 7.4 was higher than that at pH 5.6. Good plasmid condensation and protection ability was shown when N/P molar ratio of PEA to DNA was above 15 (N: nitrogen element in PEA, P: phosphate in DNA). PEA/DNA complexes had positive zeta potential, narrow size distribution, good dispersity, and spheric shape with size below 250 nm when N/P ratio was above 30, suggestion of their endocytosis potential. Compared with PEI 25 KDa, the PEAs showed essential nontoxic to HeLa, HepG2 and 293T cells. With an increase in the molecular weight of PMEG, the transfection efficiency of PEAs in HeLa, HepG2 and 293T showed a tendency to decrease as well as the percent decrease of gene transfection efficiency with serum. The mechanism of PEA‐mediated gene transfection was attributed to “proton sponge effect” of PEI in the PEA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The kinetics of the thermal decomposition of poly(3‐hydroxybutyrate) and maleated poly(3‐hydroxybutyrate)

The thermal decomposition mechanism of maleated poly(3‐hydroxybutyrate) (PHB) was investigated by FTIR and ¹H NMR. The results of experiments showed that the random chain scission of maleated PHB obeyed the six‐membered ring ester decomposition process. The thermal decomposition behavior of PHB and maleated PHB with different graft degree were studied by thermogravimetry (TGA) using various heating‐up rates. The thermal stability of maleated PHB was evidently better than that of PHB. With increase in graft degree, the thermal decomposition temperature of maleated PHB gradually increased and then declined. Activation energy E_a as a kinetic parameter of thermal decomposition was estimated by the Flynn‐Wall‐Ozawa and Kissinger methods, respectively. It could be seen that approximately equal values of activation energy were obtained by both methods. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1789–1796, 2002; DOI 10.1002/app.10463