Effect of pH on Poly(acrylic acid) Solution Polymerization

The free-radical redox-initiated aqueous solution polymerization of fully and partially neutralized acrylic acid was carried out at room temperature under full exposure to air. The effect of neutralization degree on the polymerization rate and product properties was studied. Increasing neutralization of the reaction mixture with sodium hydroxide resulted in greater conversion of acrylic acid to sodium acrylate. The rate of polymerization, determined from a gravimetric off-line water removal technique, was shown to decrease significantly with decreasing degree of neutralization. Molecular weight also decreased with decreasing degree of neutralization. The glass transition temperature and hydrophilicity of the polymer product decreased with increasing degree of neutralization. In-line infrared monitoring was also used to monitor the reaction progress and was shown to be an effective tool for this purpose.     

植物油酸／Tween－60复配体系与原油间的界面张力

研究了植物油酸及其中和物／Ｔｗｅｅｎ－６０复配体系与大庆原油间界面张力随各种因素的变化规律。结果表明，当０．４０％ＮａＣｌ存在时，植物油酸中和度为０．８５，ＮａＣｌ浓度为０．９０％时，复配以０．１０％Ｔｗｅｅｎ－６０既可使体系兼容，又可使之保持较低界面张力。     

Micron range morphology of physical chitosan hydrogels

Physical chitosan hydrogels are potential biomaterials for several biomedical applications, such as wound healing, tissue repair, and drug delivery. Controlling the microstructural organization of chitosan gels is one of the keys for monitoring the physical, mechanical, and biological properties. As a result, the main objective of the present work was to explore the microstructural organization of chitosan hydrogels in relation with the processing conditions of gelation. For this purpose, different gelation routes were studied, that is, chitosan solution neutralization of an aqueous or hydroalcoholic solution and neutralization of an alco-gel. Overall, the resulting morphology after processing was determined by the medium viscosity during neutralization and the nature and concentration of the base. The effect of these processing parameters on the morphology was evaluated mainly through small angle light scattering (SALS) measurements including in situ measurements during chitosan neutralization. As a result, we reported different bulk microstructures consisting in 200-400 nm aggregates (primary particles) agglomerated into micrometer range clusters or arranged into more organized structures, that is, forming microchannels (4-6 μm). We thus established a qualitative and quantitative relation between supramolecular morphology and gelation conditions of chitosan hydrogels.     

On sorption extraction of rare-earth elements in the nitric acid processing of Khibiny apatite concentrate

Fundamental aspects of the sorption recovery of rare-earth elements with a sulfocationite from a nitric-phosphoric acid solution formed as intermediate product in the nitric acid processing of Khibiny apatite concentrate were studied. It was confirmed that rare-earth elements can be effectively sorbed from a nitric-phosphoric acid solution without its preliminary neutralization. It was found that polyvalent metals can be sorbed from a nitric-phosphoric acid solution in the form of positively charged (possibly, single-charged) complexes containing nitrate and(or) phosphate ligands.     

硫铁矿烧渣制备氧化铁黄和氧化铁红

对利用硫铁矿烧渣制备氧化铁黄和氧化铁红进行了研究。考察了影响硫铁矿烧渣还原、酸溶、中和、氧化等过程的各种因素。结果表明,在适宜的条件下,利用烧渣可以制备出用做颜料的氧化铁黄和氧化铁红。     

油酸-油酸钠水溶液/原油间的瞬时界面张力

羧酸盐表面活性剂以其价格低廉、资源丰富和较高的界面活性而受到重视[1]．我们将廉价的天然核酸盐复配体系用于提高采收率研究，取得良好效果问．据最近报道问，用瞬时界面张力（l）评价驱油体系更符合实际采油过程．本文应用试剂级油酸，试图从理论上探讨不同因素对混合体系瞬时界面张力的影响规律，为驱油体系配方的选择提供依据．1实验部分1．1试剂油酸（R17C00H），分析纯收京长城化学试剂厂产品）．水解聚丙烯酸胶（HPAM），平均分子量为1．7X10’，平均水解度为20％，（美国辉瑞公司产品）．1．2方法按设计量在电子分析天平（精…     

聚苯乙烯磺酸钠与阳离子表面活性剂的相互作用和纳米聚集体的生成

在聚苯乙烯磺酸钠(PSS)的水溶液中,引入阳离子表面活性剂(CTAB或DDAB)使与PSS通过静电相互作用实现聚苯乙烯磺酸盐不同程度的中性化,并进而对PSS/表面活性剂复合物在水中的行为特征、特别是PSS因疏水化而产生的聚集行为以及临界聚集浓度等采用多种方法如溶液的透光率;荧光光谱;荧光探针以及扫描电镜观察等进行了研究,得到一些颇为有趣的结果.结果表明PSS-CTAB或DDAB加成物可自发的形成约70 nm的纳米粒子。而中性化程度则对加成物的构型以及体系的透光率等有较大影响。结果还表明所得具有亲水外壳和疏松的疏水内核的聚集体能容易的使疏水分子进入其中。     

Polypropylene ionic thermoplastic elastomers: Synthesis and properties

Polypropylene ionic thermoplastic elastomers have been prepared by melt radical grafting of maleic anhydride onto polypropylene in the presence of N-bromosuccinimide followed by neutralization of the resulting elastomeric grafted polypropylene using sodium salts. Sodium hydroxide and sodium acetate were compared in aqueous solution, as anhydrous or hydrated powders. The neutralization reaction was followed by Fourier transform infrared spectroscopy, allowing the development of a method to determine the effective neutralization degree. Important physical changes were recorded upon neutralization. Especially thermal stability, shear storage modulus and complex viscosity in the flow region were largely increased as a function of the neutralization degree.     

Solution properties of stilbene‐containing sterically crowded alternating polyanions

Sterically crowded stilbene‐containing alternating polyanions were prepared via an indirect strategy of synthesizing “protected” monomers followed by deprotection and neutralization of the polyanion precursors. The solution properties of these new sterically crowded polyelectrolytes were studied. Steady‐state solution shear rheology showed a pronounced polyelectrolyte effect. The persistence lengths of these polyelectrolytes were determined. The dissociation behavior of the polyanions was investigated by pH titration with HCl, and multistep dissociation behavior was observed. Chain size and aggregation were studied by using DLS at varying ionic strengths. Polyelectrolytes behaved like rigid‐rods and formed concentrated solutions at the polymer concentration of 1.0 mg mL^?1. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1565–1570     

Rheological behavior of PAA–C n TAB complex: influence of PAA charge density and surfactant tail length in PAA semidilute aqueous solution

Interactions between anionic polyelectrolyte, poly(acrylic acid) (PAA), and cationic surfactant, alkyltrimethylammonium bromide (C _n TAB), were investigated by rheological measurements in semidilute PAA solution. The dependences of the rheological behavior on the chain length of the surfactant, PAA neutralization degree, and temperature were discussed. The results revealed that both dodecyl and cetyltrimethylammonium bromides (C₁₂TAB and C₁₆TAB) could increase the viscosity of PAA solution when the surfactant amounts surpassed a critical surfactant concentration (C _c), and C _c of C₁₆TAB was lower than that of C₁₂TAB at same PAA neutralization degree. The increase of viscosity is attributed to the surfactant micelles bridging of the polymer chains and confine the mobility PAA chain. On the other hand, it is found that the hydrogen bonding also played an important role in the PAA–C _n TAB system, especially in lower neutralization degree PAA solution, which results in the viscosity increase rapidly with the added surfactant into lower neutralization degree PAA solution.     

pH Change of buffer solution in a microcapillary chip and its suppression

During the electrophoresis separation of B- and T-cells from lymphocytes employing a microcapillary chip, they were found to become inactive in the reservoir after a short time. This was caused by the buffer solution becoming alkaline due to electrolysis. This was considered to take place in chips with small reservoir volumes. The pH change was confirmed by the ISFET (ion-sensitive field effect transistor) embedded in the chip. To suppress the pH change, two methods were studied. One is the insertion of a salt bridge just in front of and behind the capillary, thus introducing an electric potential but stopping flow of the acid and alkaline solutions into the capillary. The other is neutralization of the alkaline solution in the reservoir by injecting the acid solution produced in another capillary with the same structure by employing an electroosmotic flow (EOF) pump. Both methods achieved no pH change during electrophoresis measurements in the microcapillary.     

Association behavior of poly(methyl methacrylate-block-methacrylic acid) in aqueous medium

The atom transfer radical polymerization technique was used to synthesize the poly(methyl methacrylate-block-methacrylic acid) (P(MAA-b-MMA)) copolymer in order to study the aggregation behavior in aqueous solution over the course of neutralization. Combinations of static and dynamic light scattering (SLS, DLS) and potentiometric titration techniques were used to investigate the size and shape of the micelle at various degrees of neutralization (alpha). By comparing the effect of different polymer chain length with similar MMA/MAA ratio on the aggregation behavior during neutralization, we found relatively strong entanglement of long MMA polymer chains. The comparison between the different MMA/MAA ratios showed that longer MMA chains produced more entanglements. Conductometric titration was used to determine the counterion condensation phenomenon during the course of neutralization. At a critical micellar charge density observed at alpha approximately 0.4, Na+ ions are condensed on the polymer chains. The amount of condensed Na+ was evaluated by the conductivity change, yielding the condensation ratio when the polymer was completely neutralized.     

Needleless electrospinning of poly(acrylic acid) superabsorbent: Fabrication,characterization and swelling behavior

In this work, nanofibrous hydrogel has been fabricated from needleless electrospinning of Poly(acrylic acid) (PAA) in an aqueous solution with different concentrations. First, all solution samples were characterized for pH, surface tension, conductivity and viscosity. Next, electrospinnability of the PAA-water dope solution was investigated using the needleless electrospinning technique under constant conditions. Results indicated that the PAA-water solution was not electrospinnable. Therefore, the neutralization of carboxylic groups in the PAA chemical structure using the NaOH solution was investigated to enhance the PAA electrospinnability. Morphology observation revealed that the fiber diameters ranged from 40 to 250 nm and increased with increasing the solution concentrations. Increasing the neutralization degree (10%, 15% and 20% with 50 wt% NaOH solution) led to increase the dope viscosity and conductivity. The resultant nanofibers could be rendered water-insoluble by incorporating 1,4-butanediol diglycidyl-ether in the PAA-water dope solution, then heat-induced crosslinking was performed using a microwave at different curing times (1–5 min) and temperatures (45–105 °C). The nanofibrous hydrogel mat was then characterized by FTIR. The resulting nanofibrous hydrogel showed remarkable water absorption capacity up to 17,000% and 51,000% (within 15 min) in the standard saline solution and distilled water, respectively.     

Oxonol 染料的稳态光物理行为研究

对oxonol——一种带负电荷类菁染料化合物溶液的光谱和光物理问题进行了研究.发现它和一般分子内共轭的电荷转移化合物相比，无论在吸收光谱或荧光发射光谱上，都表现出不同的光物理和光化学行为.对出现的这种差异，特别是负的溶致变色行为和在不同pH条件下分子的互变异构等对吸收光谱的影响进行了讨论.     

Synthesis and rheology of methacrylic acid-ethyl acrylate crosslinked polymers

The rheological behaviour of methacrylic acid-ethyl acrylate copolymers (MAA 61.9–78.5 mol%) and terpolymers with two crosslinking agents, i.e. ethylene glycol dimethacrylate (EGDM, 0.23–4.83 mol%) or N, N′-methylene bisacrylamide (MBAM, 0.29–1.48 mol%) has been studied. The effect of pH, shear rate, solid content of the solution, and the addition of electrolyte on the viscosity has been reported. As the viscosity is a function of neutralization of carboxylic acid groups, it was found to be highly dependent on pH. Addition of electrolytes (0.5–1.5%) led to a drastic drop in the viscosity. The influence of different crosslinking agents on the viscosity was also studied and N, N′-methylene bisacrylamide was found to be more efficient than ethylene glycol dimethacrylate. The gel content of the crosslinked polymers was determined to obtain an idea of the degree of crosslinking of the polymers.     

表面交联的三元共聚高吸水树脂的合成及其性能研究

以丙烯酸、丙烯酰胺及丙烯磺酸钠为单体,采用水溶液聚合法制得三元共聚高吸水树脂(SAP1),用乙二醇二环氧甘油醚与氯化铝作交联剂,对SAP1进行表面交联处理得高吸水树脂SAP2。SAP2在加压下吸盐水率高,凝胶颗粒表面干爽且易分散。考察了引发温度、丙烯酸中和度、交联剂、引发剂、丙烯酰胺及丙烯磺酸钠的用量对常压下吸盐水率的影响。同时还考察了乙二醇二环氧甘油醚与无机盐用量对常压及加压下吸盐水率的影响。     

Binding of dodecyltrimethylammonium bromide to pH-responsive nanocolloids containing cross-linked methacrylic acid-ethyl acrylate copolymers

The binding of dodecyltrimethylammonium bromide (DoTab) to cross-linked methacrylic acid-ethyl acrylate (MAA-EA) copolymers with various MAA/EA molar ratios at different degrees of neutralization (alpha) was quantitatively studied using isothermal titration calorimetry, dynamic light scattering, surfactant selective electrode, and electrophoresis techniques. The surfactant binds to the polymers at all degrees of neutralization, but via different mechanisms. When alpha is sufficiently high, the binding is primarily electrostatic interaction between the surfactant and ionized polymer chains, which is reinforced by the micellization of electrostatically bound surfactant molecules. The saturation takes place at charge ratio ([DoTa(+)]/[ approximately COO(-)]) close to 1, indicating that the binding is a one-to-one charge neutralization between the cationic surfactant headgroups and anionic carboxylate sites of the polymers. When alpha is low, the binding of DoTab to the unneutralized polymers is driven by the hydrophobic interaction. The onset of hydrophobic binding takes place at DoTab concentration as low as 0.01 mM in 0.05 wt % polymer solution, where the saturation occurs at C(DoTab) approximately 0.19 mM and the amount of bound surfactant is approximately 0.09 mmol of DoTab/(g of polymer) at saturation concentration. The binding results in the formation of the polymer-surfactant complex. For the polymer with low MAA/EA molar ratio, the complex coagulates at a higher DoTab concentration that leads to phase separation; however, for polymers with high MAA/EA molar ratio, the complex remains dispersed and the mixture is stable even at high DoTab concentration.     

On the properties of Calcein Blue

A satisfactory method for the preparation of Calcein Blue has been devised. Elemental analysis, equivalent weight by neutralization, and the NMR spectrum show the compound to be 4-methylumbelliferone-8-methyleneiminodiacetic acid·0·25H₂O. The ultraviolet absorbance and fluorescence have been studied as a function of pH and, combined with potentiometric titration and solubility date, have yielded for the acid dissociation constants the values pK₁ = 3·0, pK₂ = 6·9, and pK₃ = 11·3. These acid functions are identified respectively as carboxyl, phenol, and ammonium ion, the free Calcein Blue being a zwitter-ion. Calcein Blue fluoresces in both acidic and basic solution when excited at a suitable wavelength. The fluorescence of the doubly-charged anion formed on the neutralization of the phenol group, when excited at 360 nm, reaches a maximum at pH 9, and decreases to zero with the neutralization of the ammonium ion; the wavelength of maximum emission is 455 nm. In the presence of calcium, the fluorescence increases with alkalinity up to pH 9 and then remains constant. The calcium derivative is a 1:1 compound, formation constant 10^7·1. The fluorescence of Calcein Blue at all pH values is quenched by copper(II). The calcium derivative is changed on standing in highly alkaline solution, presumably by ring opening, to another fluorescent material; thus Calcein Blue, although satisfactory as an indicator, is not useful for the direct fluorometric determination of calcium.     

Gel speciation studies-II An extension of earlier studies of the protonation equilibria of cross-linked carboxymethyldextran

The potentiometric properties of the rigidly cross-linked Sephadex gel CM-25 have been studied. The gel was equilibrated in sodium perchlorate at fixed concentration levels (0.010 and 0.0010M) and with variable concentration levels of NaClO(4) (from 0.0010 to 0.10M). The volume of the gel was measured for every equilibrated sample simultaneously with the solution pH and pNa. The pK computed after correction for a Donnan potential term was found to be independent of alpha, the degree of neutralization, and ionic strength; its value of 3.35 +/-0.15 was in excellent agreement with the intrinsic pK measured earlier for the flexible CM-50 Sephadex gel and reported for its linear polyelectrolyte analogue, carboxymethyldextran. An interesting observation from these studies is the efficient screening of the charged surface by the counter-ions in the presence of a three-dimensional charged network.     

Webcam camera as a detector for a simple lab-on-chip time based approach

A modification of a webcam camera for use as a small and low cost detector was demonstrated with a simple lab-on-chip reactor. Real time continuous monitoring of the reaction zone could be done. Acid-base neutralization with phenolphthalein indicator was used as a model reaction. The fading of pink color of the indicator when the acidic solution diffused into the basic solution zone was recorded as the change of red, blue and green colors (%RBG.) The change was related to acid concentration. A low cost portable semi-automation analysis system was achieved.