Flocculation of gelatinized starch: Flocculation performance and floc characterization

The removal of single macromolecules impurity is the basis study for the promotion of flocculation technology application in the Chinese herbal medicine solution purification. We applied the flocculation process to remove gelatinized starch in solution. Three types of cationic polyacrylamide (CPAM) with different charge density were used for flocculation of gelatinized starch solution. The flocculation performance was evaluated in terms of the amylose removal ratio (AMRR), the amylopectin removal ratio (APRR), total starch removal ratio (TSRR) and supernatant turbidity (ST). The flocs were characterized by sedimentation performance, Fourier transform infrared (FTIR), scanning electron microscope (SEM) and X-ray photoelectric spectroscopy (XPS) method. The experimental results show that the flocculant CN15 has the best performance for gelatinized starch flocculation among three flocculants. According to the characterization analysis, the flocs exhibited an obvious network structure, and it is concluded that hydrogen bonding between N-H in CPAM and C-O in the starch and bridging flocculation played the essential roles in flocculation of the gelatinized starch.     

Thermal stability of polymers based on acrylamide and 2-acrylamido-2-methylpropane sulfonic acid in different temperature and salinity conditions

Partially hydrolyzed polyacrylamide (PHPA) is the most widely used polymer in enhanced oil recovery (EOR) applications. However, under conditions of high temperature and salinity, the PHPA molecules become hydrolyzed, causing a drastic reduction of the viscosity of the polymer solution due to the presence of negative charges, making the molecules more susceptible to interactions with cations. In this sense, in order to increase the stability of these polymers, an anionic monomer more resistant to cations such as 2-acrylamido-2-methylpropane sulfonic acid (AMPS) has been incorporated into the HPAM molecules. This work evaluated the thermal stability of a copolymer (acrylamide and AMPS - AN125) and a terpolymer (acrylamide, acrylate, and AMPS-FP5115) in the time course of 360 days. The tests were carried out in typical conditions of Brazilian offshore reservoirs, such as absence of oxygen, high temperature, and high salt concentration. The test method involved measurements of intrinsic viscosity in function of time and determination of the hydrolysis degree of the polymers by elemental analysis. The copolymer AN125 was more stable under the test conditions than the terpolymer FP 5115 due to the presence of a higher concentration of AMPS in the copolymer. The AMPS group was hydrolyzed to AA at a temperature of 100 °C, however, the increase in salt concentration delayed the onset of this degradation. The tests indicated that the presence of a higher AMPS content in the copolymer does not prevent the polymer from undergoing hydrolysis, but delays the polymer precipitation step in the solution.     

Synthesis and applications of reactive carbohydrates. III. Preparation and methylolation of polyacrylamide-carboxymethyl cellulose graft copolymers

Carboxymethyl cellulose (CMC) was treated with HCl at 80°C for different time periods (15 – 60 min). The hydrolyzed CMC samples as well as the original sample were graft copolymerized with acrylamide using K₂S₂O₈ as initiator. It was disclosed that the increasing duration of acid hydrolysis is accompanied by a progressive increment in the copper number of CMC, meanwhile its carboxyl content decreases. Acid hydrolysis enhances significantly the susceptibility of the CMC toward grafting. The latter reduces the copper number of the hydrolyzed CMC samples most probably via conversion of the aldehydic to carboxylic groups under the action of K₂S₂O₈ during grafting. Grafting also reduces the carboxyl content of the original CMC sample while increasing those of the hydrolyzed CMC samples. Methylolation of the polyacrylamide-CMC graft copolymers results in reactive finishes. When the latter were applied to cotton fabric according to the conventional pad-dry-cure method followed by a thorough washing, the fabric retained ca. 86% of the finish derived from the copolymer of CMC and 92% of finishes derived from the copolymers of hydrolyzed CMC.     

The flame‐retardant polyester fiber: Improvement of hydrolysis resistance

As far as the flame‐retardant polyester fibers are concerned, the copolymerization of phosphorus retardants is the most common method. But a serious problem is that the phosphorus‐containing polymer is easily hydrolyzed. We investigated the flame retardancy and the hydrolysis properties of two poly(ethylene terephthalate) (PET) fibers, one with a phosphorus compound as a side chain (side‐chain type: HEIM® Toyobo Co., Ltd.), and one with a phosphorus compound inserted in the polymer backbone (main‐chain type). Both types had almost the same properties of fibers and flame retardancy, but the main‐chain type was hydrolyzed about two times faster than the side‐chain type, and led to a decrease of toughness immediately. This difference of hydrolysis properties between main‐chain type and side‐chain type depends on whether a phosphonate ester bond is placed in the polymer backbone or the pendant site. In the case of the main‐chain type, the scission of the polymer backbone chain occurs by hydrolysis of phosphonate ester bonds; however, in the case of the side‐chain type, this does not occur. These results demonstrate that the flame‐retardant polyester fiber with the side‐chain type modifier gives sufficient flame retardancy and excellent hydrolysis resistance. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1134–1138, 2000     

Effects of hydrolysis treatment on the structure and properties of semi-interpenetrating superabsorbent polymers

A semi-interpenetrating polymer network superabsorbent polymer based on sodium lignosulfonate-graft-poly(acrylic acid-acrylamide)/potassium dihydrogen phosphate and polyvinyl alcohol (PVA/SL-g-P[AA-AM]/KDP) was synthesized by using solution polymerization. The PVA/SL-g-P(AA-AM)/KDP was further hydrolyzed in NaOH solution. The structure, thermal stability, and morphologies of samples were examined by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The results of FTIR, TGA, and DSC showed that PVA interpenetration through SL-g-P(AA-AM)/KDP network has occurred, and PVA/SL-g-P(AA-AM)/KDP was successfully alkaline hydrolyzed. From the SEM images, the high porous and loose surface structure of polymers was formed after hydrolysis, which greatly increased the specific surface area. Samples after hydrolysis exhibited higher equilibrium swelling capacity (1963 g/g) compared to the nonhydrolyzed samples (866 g/g). The swelling kinetics of all samples well complied with the pseudo-second order swelling kinetics model. Simple hydrolysis treatment not only improved the swelling capacity of PVA/SL-g-P(AA-AM)/KDP but also induced an enhancement on its water retention performance, which made it potentially useful as a water retention agent in the revegetation of abandoned mines or slope wasteland.     

Study on the acidic hydrolysis process of poly(N‐vinylformamide/acrylonitrile) fiber

A convenient method of preparing chelating fiber with amine groups on the fiber surface was developed. The precursor polymer of Poly(N‐vinylformamide/acrylonitrile) (P(NVF/AN)) was synthesized via solution polymerization, using N‐vinylforaimde as a functional monomer. The solution of P(NVF/AN) was spun through a wet spinning method and the precursor fiber was hydrolyzed in the hydrochloric acid solution to convert formamide moieties to the corresponding amine. The influence of hydrolytic conditions on hydrolysis degree, such as hydrolysis temperature, hydrolysis time, and hydrochloric acid concentrations were examined experimentally. The hydrolysis degree of the precursor fiber was evaluated by potentiometric and conductometric titrations. The changes of the structure and properties of the fibers were characterized through infrared spectroscopy, scanning electron microscopy, and tensile strength tester. The results showed that the hydrolysis degree was limited in acidic hydrolysis because of the electrostatic repulsion among the cationic amine groups and proton. The hydrolysis degree of precursor fiber reached nearly 60%, and the chelating fiber remained the adequate mechanical properties under the suitable hydrolysis condition. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

星形聚合物的发展近况

综述了采用负离子聚合技术合成的星形聚合物的结构与性能的关系、合成路线及应用。新开发的星形聚合物,如ＳＳＢＲ,ＬＣＢＲ,ＭＶＢＲ,ＨＶＢＲ,ＳＩＢＲ等,运用高分子分子设计的方法来合成,因而具有更佳的综合性能,如高的抗湿滑性及低的滚动阻力等。     

Properties of flocs in sludge conditioning by a novel amphoteric polymer with different anionic degrees

This paper aimed to examine how the amphoteric conditioner poly (acrylamide‐′acryloyloxyethyl trimethyl ammonium chloride ?2‐acrylamido‐2‐methyl‐propane sulfonate) (PADA) with different anionic degrees (AD) affected the properties of sludge flocs in the conditioning. The floc properties were characterized by morphological parameters (floc size distribution, fractal dimension, specific surface area, and pore volume), physical properties (floc strength and surface charge density), and chemical constituents (Fe³⁺, Al³⁺ and extracellular polymeric substances (EPS), including the polymeric proteins and carbohydrates). The results of this investigation revealed that (1) morphological properties of flocs were associated with anionic degree, particularly in the range of 0–4%, where the anionic degree led to a shift of the particle size toward groupings of larger diameter, meanwhile better regularity and increased compactness of floc structure formed. (2) The introduction of the anionic groups indeed had bad effects on flocs in terms of its stability and charge neutralization, but the downtrend could be inhibited by adjusting the anionic degree of polymer to a reasonable level. (3) The dissolved EPS for sludge followed a role of decreasing firstly then increasing with increased anionic degree, but the content of bound EPS kept nearly constant. (4) The polymer with anionic groups had apparent effects on enrichment of metal ions. POLYM. ENG. SCI., 57:197–205, 2017. © 2016 Society of Plastics Engineers     

Role of cationic polyacrylamide in fiber‐CaCO3 pigment interactions

It is believed that the action of cationic polyacrylamide as a retention aid for incorporating pigment particles into a paper is based on its ability to form a polymeric bridge between particles and pulp fiber suspended in water. When the polymer is added to a mixture of fibers and pigments, this process is complicated by the different rates of polymer adsorption on the fibers and the pigment particles, the rate of collision between them, and the charge reversal of the polymer from the hydrolysis. To elucidate under which conditions the polymer can form a bridge, the processes of polymer adsorption and pigment–fiber interaction were separated. A deposition of pigment particles onto fibers suspended in water was investigated, using both components pretreated with the polymer. The results indicated that polymer adsorbed on fiber can form a bridge with untreated pigment particles regardless of the polymer charge. On the other hand, negatively charged hydrolyzed polymer adsorbed on the pigment does not form a bridge with untreated fiber. When both the fiber and the pigment are pretreated, the bridge formation depends on their surface coverage by polymer and its charge. No deposition takes place when both components are sufficiently coated by anionic hydrolyzed polymer, which indicates electrosteric repulsion. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2409–2415, 2003     

Effect of microscopic aggregation behavior on polymer shear resistance

The study of polymer aggregation behavior effect on shear resistance shed light on the synthesis of antishear polymer for oil displacement and enhances the application effect of polymer flooding. The effects of mechanical degradation on the properties of polymer solutions were studied by using partially hydrolyzed polyacrylamide (HPAM), hydrophobically modified HPAM (HMPAM), and dendritic hydrophobic associative polymers (DHAP), which are characterized by “granular,” “chain,” and “cluster” aggregation behavior, respectively. The results show that mechanical shearing can dramatically reduce the performance of polymer solution. The shearing resistance can be effectively enhanced by improving the polymer aggregation behavior. After being strongly sheared, hydrophobically associating polymers can still partially restore its network through hydrophobic association, therefore rebuild the solution viscosity. For DHAP, the broken molecular chains distribute more evenly in solution after shearing. In addition, the strength of reconstructed network structure of DHAP is better than that of HMAPM, which implies a better shear resistance. Furthermore, the hydrophobic association of linear polymers will increase their static adsorption on quartz sand. Meanwhile, DHAP with stronger spatial structure has less static adsorption, which is beneficial to maintain a higher polymer concentration in solution. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48670.     

The flocculation of kaolin by cationic polyacrylamides and the effect of cationic surfactant on this process

The flocculation of kaolin suspended in a dilute salt solution was studied as a function of the addition of cationic surfactant and cationic polyacrylamide (CPAM) added separately, consecutively, or simultaneously. Cationic polyacrylamide caused flocculation by bridging when added in low concentrations, but at higher concentrations, charge neutralization became the dominant mechanism and the flocculation rate was highly dependent on the charge density of the polymer. Adsorption of sufficient polymer or surfactant (cetyl pyridinium chloride) prevented immediate adsorption of the other, although surfactant could replace polymer after extended agitation. The adsorption of polymer was greatest when small flocs were formed by charge neutralization or by prolonged shaking. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2382–2389, 2002     

Combination of atomic force microscopy and chemical hydrolysis to characterize degradable regions in polymer blends

In this study, we demonstrate the usefulness of chemical‐based method in combination with atomic force microscopy (AFM) to characterize the degradable regions in a wide range of polymer blends. This approach is based on selective hydrolysis of one of the components in a multiple‐phase system, and the ability of AFM to provide nanoscale lateral information about the different phases in the polymer system. Composite films containing different percentage of hydrolyzable polymer were either melt processed or solution casted and then exposed to a hydrolytic acidic environment. Tapping mode AFM was used to analyze the samples before and after hydrolysis. Dramatic topographic changes such as pits were observed on the acid exposed samples, indicating that the degradation was localized and the more susceptible component in the blend was hydrolyzed. Additionally, the progressive hydrolysis of the composites was studied by attenuated total reflection FTIR (ATR‐FTIR) analyses to confirm the AFM results. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 726–733, 2006     

Flows of dilute hydrolyzed polyacrylamide solutions in porous media under various solvent conditions

Experimental results on pressure losses of flows of dilute polymer solutions through porous media are summarized. The polymer products employed in this study consisted of partially hydrolyzed polyacrylamides (HPAM) with different degrees of hydrolysis. The effect of the hydrolysis on the pressure drop is investigated in a porous media test section designed to minimize polymer degradation. The investigations were carried out for various solvent conditions, and it is shown that the maximum increase in pressure drop is mainly dependent on the molecular weight of the polymers. The onset of the polymer action is measured for various fluid and solvent properties. Particular attention is given to measurements near θ-conditions. The results stress the importance of the solvent properties on the actions of the polymers and on the resultant pressure drop for porous media flows. The addition of salt ions to solutions of partially hydrolyzed polyacrylamides yields onset behavior previously observed for nonionic polymers. The differences measured between various solvent properties can be explained by the actual hydrodynamic molecule dimensions for a given molecular weight and polymer concentration. To quantify the influences of the solvent properties on the polymers, measurements were carried out in aqueous solutions for various pH values and therefore at various degrees of dissociation. The importance of separating polymer effects caused by their linear dimension in the solution from those that are introduced by and increase in solvent viscosity is shown. Measurements were performed to quantify the effects of solvent viscosity on the polymer action and to separate these effects from those due to changes in molecule dimensions. The implications of the present results are stressed in connection with applications of polymer solutions in tertiary oil recovery, and the positive features of the molecule actions on flow in such applications are described.     

Structure-property-performance relationships of sulfonated poly(arylene ether sulfone)s as a polymer electrolyte for fuel cell applications

This article focuses on structure-property-performance relationships of directly copolymerized sulfonated polysulfone polymer electrolyte membranes. The chemical structure of the bisphenol-based disulfonated polysulfones was systematically alternated by introducing fluorine moieties or other polar functional groups such as benzonitrile or phenyl phosphine oxide in the copolymer backbone. Ac impedance measurements of the polymer electrolyte membranes indicated that fluorine incorporation increased proton conductivity, while polar functional group incorporation decreased conductivity. Likewise, other properties such as water uptake and ion exchange capacity are impacted by the incorporation of fluorine moiety or polar groups. These properties are critically tied with H₂/air and direct methanol fuel cell performance. We have rationalized fuel cell performance of these selected copolymers in light of structure-property relationships, which gives useful insight for the development and application of next generation polymer electrolytes.     

多级孔金属有机骨架材料的合成及其在生物医药中的应用研究进展

金属有机骨架（metal-organic frameworks,MOFs）是多孔材料领域的研究热点之一。MOFs具有高比表面积和孔道均一等特点,但微孔MOFs在大分子应用领域受到限制。本文介绍了延长配体法、模板剂法和聚合物法等多种制备多级孔MOFs的方法,合成后的多级孔MOFs兼具微孔、介孔和大孔,能够参与大分子反应,同时具有水热稳定性和化学稳定性,在催化、气体吸附分离、储能材料等诸多领域表现出优异性能。本文重点介绍了多级孔MOFs在生物医药领域的研究进展,结果表明多级孔MOFs是一种孔道可调节、可在特定条件下分解的生物相容性材料,用于固定化酶和负载医药分子均表现出良好性能。最后讨论了多级孔MOFs材料制备和应用目前存在的问题与挑战,展望了多级孔MOFs材料作为一类新型功能化多孔材料的应用前景。     

Covalent immobilization of biological molecules to maleic anhydride and methyl vinyl ether copolymers—A physico‐chemical approach

The covalent grafting of biological molecules to copolymers of maleic anhydride and methyl vinyl ether (MAMVE) has been used in various applications in diagnostics. To tentatively elucidate the phenomena involved in the control of the immobilization of oligodeoxynucleotides and proteins, the physico‐chemical properties of MAMVE copolymers were investigated. Because the grafting mixture contains water, to allow dissolution of the biomolecules without loss of biological properties, the anhydride‐based copolymer evolves from a neutral to a negatively charged macromolecule due to hydrolysis of the anhydride moities. The properties of both hydrolyzed and nonhydrolyzed polymers were investigated. As demonstrated by light‐scattering measurements in batch, the copolymers showed some level of aggregation in DMF, DMSO, and aqueous DMSO. The presence of aggregates was confirmed by size‐exclusion chromatography in DMF. However, partial deaggregation occurred for the lowest molecular weight sample, on adding 1% w/v of LiBr. The nonhydrolyzed copolymers exhibited a rigid conformation in a 5% water/DMSO mixture, as well as their hydrolyzed counterpart at a low ionization degree. The rate of the hydrolysis reaction was shown to be dependent on the pH of the reaction medium and on temperature. The activation energy of the hydrolysis reaction was 14 kJ/mol, and the rate constant in the order of 10⁻⁴ s⁻¹. On the basis of these data, the effect on the grafting reaction of biomolecules of different parameters such as ionic strength and the nature of the solvent, along with some other results were interpreted in terms of interactions between the synthetic and bioactive macromolecules. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 927–936, 1999     

侧链含酯基的聚对苯撑的合成及其水解性研究

以自制的2,5-二氯苯甲酸甲酯和2,5-二氯苯甲酸异辛酯为单体,采用Ni/Zn催化体系,合成了侧基分别为甲酯基、异辛酯基的聚对苯撑及其共聚物,利用凝胶渗透色谱法和差示扫描量热法测试了3种聚合物的分子量及玻璃化转变温度(T_g),并测试了它们在有机溶剂中的溶解性。结果表明,利用该催化体系能得到一定分子量的聚对苯撑均聚物和共聚物,两种单体按投料比进行了共聚;通过调整单体投料比,可以调控共聚物的T_g在–7.7~130℃之间变化,当单体投料比为1∶1(物质的量之比)时,共聚物的Tg为87.7℃;当引入大支链侧基异辛酯基时,聚对苯撑在有机溶剂中的溶解性大大提高。由于侧基酯基水解的难易程度不同,通过一定的水解条件考察均聚物和共聚物的水解特性,发现在一定碱性条件下,含甲酯基的均聚物30 min内已全部水解,而含异辛酯基的均聚物在该时间内几乎不水解,水解完全需要12 h。对单体投料比为1∶1的共聚物进行水解,发现相同条件下完全水解只需75 min。水解后侧基羧基的存在可为后续的改性比如交联提供反应活性点。     

Effect of micro-aggregation behavior on the salt tolerance of polymer solutions

Polymer solution for oil displacement is mostly used in the middle and late stage of water flooding reservoir development, and reservoir groundwater conditions are often one of the main conditions restricting polymer application. Therefore, it is necessary to develop salt tolerance of polymer solutions with different aggregation behaviors, so as to facilitate the synthesis and optimization of suitable polymer systems. The differences in the micro-aggregation behavior of three polymers with different molecular structures were explored. On this basis, the effects of divalent metal cations on the properties of the polymer solutions were analyzed by assessing the micro-aggregation behavior, apparent viscosity, hydrodynamic size, and shear rheological characteristics. The results showed that the linear partially hydrolyzed polyacrylamide (HPAM) was seriously affected by divalent cations, and the viscosity decreased obviously. The aggregation behavior of the polymer changed by hydrophobic association can enhance the salt tolerance of the solution. The hydrophobically modified partially hydrolyzed polyacrylamide (HMPAM) with “chain beam” aggregation behavior has strong intermolecular connection, which enables it to withstand the content of calcium and magnesium ions of 1100 mg l⁻¹. When the content of calcium and magnesium ions exceeds 600 mg l⁻¹, dendritic hydrophobically associating polymer (DHAP) will destroy the interaction between molecular chains, resulting in the decrease of apparent viscosity and hydrodynamic size. For polymer flooding in high-salinity reservoir, salt tolerant polymer system can be constructed by optimizing molecular weight and hydrophobic group content.     

Synthesis and functionality of dendrimer with finely controlled metal assembly

Integrated research on the synthesis and functionality of macromolecular metal complexes has suggested that dendritic structures exhibiting a geometrical density gradient also impart a potential gradient within the constituent molecules. Focusing on dendritic π-conjugated macromolecules containing azomethine (imine) as a metal assembly site, the stepwise radial complexation of metal ions in a dendritic phenylazomethine structure has been identified for the first time. Using this discovery, the first macromolecules with precision control of the number and position of metal molecules have been synthesized. A series of new physicochemical discoveries have followed from this success, related to stepwise radial complexation, one-step multi-electron transfer, and potential gradients. The usefulness of these new macromolecules as a nano-material has also been demonstrated through application to (1) polymer electroluminescent devices, (2) organic solar cells with high energy conversion efficiency, and (3) the storage and release of metals in a manner similar to ferritin protein.     

Improvement of filtration performance of polyvinyl chloride/cellulose acetate blend membrane via acid hydrolysis

Based on the hydrophilicity and biodegradability of cellulose acetate (CA), polyvinyl chloride (PVC)/CA blend membrane was prepared by solution comixing and phase transformation method. Then the CA in the blend membrane was partially hydrolyzed under acidic conditions to improve the hydrophilicity of the blend membrane, so as to improve the filtration performance of the PVC/CA blend membrane. The properties of the membranes were systematically characterized by Fourier transform infrared spectroscopy, differential scanning calorimeter, and scanning electron microscopy (SEM). The porosity, water contact angle, pure water flux (PWF), protein retention rate, and mechanical properties of the membrane were measured, and the effect of hydrolysis on the filtration performance of the blend membrane was analyzed. The results showed that the hydrophilicity and porosity of the blend membrane increased, the PWF and protein rejection rate enhanced after acid catalyzed hydrolysis, while the mechanical properties of PVC membrane were maintained. This simple preparation method endows PVC/CA blend membrane with desirable filtration performance, and also helps to overcome the disadvantages of poor hydrophilicity and easy pollution of pure PVC membrane.