壳聚糖溶液pH对载细胞海藻酸钠-壳聚糖微胶囊性能的影响

以激光共聚焦扫描显微镜为研究手段, 原位直观地考察了在不同pH条件下聚电解质膜的络合程度和蛋白扩散情况. 通过分析pH值对微胶囊膜性能的影响规律, 并结合不同种类细胞对环境pH的敏感特性, 确定了制备细胞培养用海藻酸钠-壳聚糖微胶囊的最佳pH值. 结果表明, 当壳聚糖溶液的pH值由3.50增加到6.50, 微胶囊膜的络合深度呈现高-低-高的趋势, 而微胶囊膜的膨胀性能呈现低-高-低的趋势, 模型蛋白通过微囊膜的扩散呈现低-高-低的趋势, 拐点均出现在pH=4.00和5.50处. 结合动物细胞及微生物细胞对环境pH耐受能力的考察, 确定制备微囊化动物细胞时, 微胶囊成膜反应溶液的最佳pH值为5.50; 制备微囊化大肠杆菌时, 反应溶液的最佳pH值为5.00; 制备微囊化酵母菌时, 反应溶液的最佳pH值为4.50.     

Influence of non-reactive solvent on optical performance, photopolymerization kinetics and morphology of nanoporous polymer gratings

A study of nanoporous polymer gratings, with controllable nanostructured porosity, as a function of grating performance, photopolymerization kinetics and morphology is presented. Modifying the standard holographic polymer dispersed liquid crystal (H-PDLC) system, by including a non-reactive solvent, results in a layered, nanoporous morphology and produces reflective optical elements with excellent optical performance of broadband reflection. The addition of the non-reactive solvent in the pre-polymer mixture results in a morphology typified by void/polymer layer-by-layer structures if sufficient optical energy is used during the holographic writing process. The duration and intensity of optical exposure necessary to form well-aligned nanoporous structures can only be obtained in the modified system by (a) illumination under longer time of holographic interference patterning (30 min) or (b) illumination under very short time of holographic interference patterning (30 s) and followed by post-curing using homogeneous optical exposure for 60 min. Comparatively, a typical H-PDLC is formed in less than 1 min. To further understand the differences in the formation of these two analogous materials, the temporal dynamics of the photoinitiation and polymerization (propagation) kinetics were examined. It is shown herein that the writing exposure gives a cross-linked polymer network that is denser in the bright regions. With 60% (or even 45%) acrylate conversion, almost no free monomer would be left after the writing. Continued exposure serves primarily to add cross-links. This has the tendency to collapse the network, especially the less dense portions, which in effect get glued down to the more dense parts. To the extent that the solvent increases the mobility of the polymer network, this process will be aided. Equally important, the size of the periodic nanopores can be varied from 10 to 50 nm by controlling either the LC concentration in the pre-polymer mixture or by controlling the time of the homogeneous post-cure.     

乳化工艺对微胶囊型硬脂酸相变材料热性质的影响

以硬脂酸为芯材, 碳酸钙为壁材, 采用原位聚合法制备了微胶囊型相变材料; 通过扫描电子显微镜、 红外光谱及差热-热重分析对其表面形貌和热性质进行了表征; 通过改变乳化剂的种类及用量, 研究了乳化工艺对微胶囊型相变材料表面形貌、 相变温度和包覆率的影响. 实验结果表明, 在选用的3种乳化剂十二烷基苯磺酸钠、 十六烷基三甲基溴化铵和曲拉通X-100中, 十二烷基苯磺酸钠相对效果最好, 乳化剂与芯材最佳质量比为0.5%, 相变温度为112.24 ℃时, 封装率达到92.1%.     

Formation of porous poly(vinylidene fluoride) membranes with symmetric or asymmetric morphology by immersion precipitation in the water/TEP/PVDF system

The phase equilibrium boundaries of the membrane forming system, water/triethyl phosphate (TEP)/PVDF, at 25 °C were determined experimentally using cloud-point and equilibrium absorption methods. Based on the phase diagram, appropriate dope and bath compositions were selected to prepare microporous membranes by means of the isothermal immersion-precipitation technique. As a metastable casting dope with respect to crystallization was adopted, the formed membranes exhibited a uniform cross-section composed of interlocked crystal elements coexisting with the network of continuous pores, as was revealed by high resolution FESEM imaging. Morphologies of the membranes’ top surfaces were found to depend heavily on the bath strength, which was controlled by the TEP content. By changing the bath gradually from pure water to 70% TEP, the top surface evolved from a dense skin (asymmetric membrane) to a totally porous morphology (symmetric membrane). Wide angle X-ray diffraction analysis indicated that PVDF crystallized into α-type structure for all of the synthesized membranes. The crystallinity as determined from diffraction peak deconvolution was ≈65%, which value was confirmed by Differential Scanning Calorimetry (DSC). The obtained thermograms also showed a similar melting peak temperature (T_m ≈ 169 °C) for all membranes. Furthermore, water fluxes and tensile strengths of the membranes were measured. The results were found to correlate with the morphologies of the membranes.     

Effect of neighboring groups on the pH responsive adsorption/desorption behaviors of carboxylate functionalized hollow polymer particles

In this article, a serial of bi‐functionalized hollow polymer particles (BF‐HPPs), containing both carboxylate and different amide/amine groups [HPP‐NH₂, HPP‐ethylenediamine (EDA), and HPP‐diethylenetriamine (DETA)], were specially designed and synthesized to investigate the effect of neighboring amino groups on their adsorption/desorption behavior. Due to the high density of carboxylate groups, these BF‐HPPs can serve as efficient adsorbents for selective removal of positively charged methylene blue (b‐MB). With increasing chain length of the neighboring amino groups, the maximum adsorption capacities (q_max) at pH 7 decrease dramatically from 606.1 mg g^?1 for HPP‐NH₂, to 404.9 mg g^?1 for HPP‐EDA, and 332.2 mg g^?1 for HPP‐DETA, due to increasing steric hindrance. Significantly, the equilibrium adsorption can be achieved within 15 min for HPP‐EDA and HPP‐DETA, while it takes more than 720 min for HPP‐NH₂. Moreover, the q_max of HPP‐DETA exhibits remarkable pH‐sensitive property, which decreases sharply to 32.7 mg g^?1 at pH 3 due to strong electrostatic repulsion between positively charged ammonium groups and b‐MB molecules. Accordingly, the desorption efficiency of HPP‐DETA reached up to 94% after one desorption step, which is much higher than that of HPP‐EDA (78%) and HPP‐NH₂ (60%). The absorbed b‐MB can be facilely desorbed and the adsorption capacity of the regenerated HPP‐DETA keeps above 95% after five consecutive adsorption–desorption cycles. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1404–1413     

The pH induced vesicle to micelle morphology transition of a THP‐protected polymer

A diblock copolymer consisting of tetrahydropyranyl acrylate (THPA) as a pH‐deprotectable block, and a permanently hydrophobic block, methyl acrylate, was synthesized by RAFT polymerization using a quaternary amine functionalized, hydrophilic, RAFT chain transfer agent. The polymer self‐assembled in water to form vesicles with D_h = 130 nm, as determined by DLS and cryogenic transmission electron microscopy. Acid catalyzed deprotection of the THPA units to yield acrylic acid resulted in a vesicle to micelle morphology transition, as evidenced by the decrease in hydrodynamic diameter to D_h = 19 nm and the observation of micelles by dry state transmission electron microscopy. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3026–3031     

Effect of external electrical field on phase behavior and morphology development of polymer dispersed liquid crystal

Phase diagrams for mixtures of liquid crystal (LC)/monomer with and without an external electrical field applied have been established using polarized light microscope (PLM).The (isotropic + nematic) coexistent phase region and (isotropic + isotropic) phase boundary of LC/monomer mixtures were observed to shift upward to higher temperatures when the external electrical field exists. It was found that the electrical field applied during the cross-linking polymerization has a significant influence on the phase diagrams for the LC/polymer mixtures by rendering the coexistent phase regions shift upward to higher temperatures. The influence of the external electrical field on the processes of the isotropic-isotropic phase separation and liquid crystal ordering in PDLC formation has also been investigated. The results revealed that both the processes could be highly accelerated by the electrical field.     

Preparation of micrometer-sized, monodisperse, hollow polystyrene/poly(ethylene glycol dimethacrylate) particles with a single hole in the shell

Micrometer-sized, monodisperse, hollow polystyrene (PS)/poly(ethylene glycol dimethacrylate) (PEGDM) composite particles with a single hole in the shell were prepared by seeded polymerization using (ethylene glycol dimethacrylate/xylene)-swollen PS particles in the presence of sodium dodecyl sulfate (SDS). Single holes were observed at SDS concentrations above 3 mM, much lower than in the PS/polydivinylbenzene (PDVB) system previously reported (above 45 mM). Phase separation inside droplets occurred at lower conversion in the PEGDM system than the PDVB system. Phase separation in the droplet at the early stage of the polymerization is an important factor for the formation of the single hole in the shell. Part CCCXIII of the series “Studies on Suspension and Emulsion.”     

A microfluidic chip with a staircase pH gradient generator,a packed column and a fraction collector for chromatofocusing of proteins

A microfluidic device for pH gradient chromatofocusing is presented, which performs creation of a micro‐column, pH gradient generation, and fraction collection in a single device. Using a sieve micro‐valve, anion exchange particles were packed into a microchannel in order to realize a solid‐phase absorption column. To fractionate proteins according to their isoelectric points, elution buffer solutions with a stepwise pH gradient were prepared in 16 parallel mixing reactors and flowed through the micro‐column, wherein a protein mixture was previously loaded. The volume of the column is only 20 nL, hence it allows extremely low sample consumption and fast analysis compared with a conventional system. We demonstrated separation of two proteins, albumin–fluorescein isothiocyanate conjugate (FITC‐BSA) and R‐Phycoerythrin (R‐PE), by using a microcolumn of commercial charged polymeric particles (Source 15Q). The microfluidic device can be used as a rapid diagnostic tool to analyse crude mixtures of proteins or nucleic acids and determine adsorption/desorption characteristics of various biochemical products, which can be helpful for scientific fundamental understanding as well as instrumental in various industrial applications, especially in early stage screening and process development.     

pH对毛细管电泳分离多肽的影响

设计了一个针对高年级本科生的毛细管电泳分离实验,用以研究pH对生物小分子多肽分离的影响。5种多肽包括Bradykinin、[Hyp3]-bradykinin、Angiotensin I、Leucine Enkephalin和[Met5]-Enkaphalin,被用于毛细管电泳的分离实验。研究了毛细管电泳生物分析实验中最重要的2个因素即电渗流和样品吸附随pH的变化以及对于分离的影响。在pH=10的条件下,酸性多肽几乎没有吸附,少量的碱性多肽有吸附。在pH=6的条件下,碱性多肽具有非常强的吸附从而导致非常差的分离效果,在pH=2.3的条件下,5种多肽都能被很好地分离,由于多肽此时都带有正电荷因此几乎没有吸附。而在此pH,电渗流消失。对具有一定分析化学基础理论知识的学生而言,这是一个非常好的生物分析实验,有助于学生充分理解相关环境因素对仪器分析的重要影响。     

The Influence of pH on the Properties of Cobalt Styrylphosphonate

Abstract

The synthesis of a new metal phosphonate and the influence of pH on its crystallinity is presented. Cobalt styrylphosphonate was synthesized by 2 methods (75^°C, 180^°C) at pH 1.5, 2, 2.4, 2.8, and 3.2, and its crystallinity was confirmed by X-ray powder diffraction.     

Effect of surface morphology on membrane fouling by humic acid with the use of cellulose acetate butyrate hollow fiber membranes

A serious problem faced during the application of membrane filtration in water treatment is membrane fouling by natural organic matter (NOM). The hydrophilicity, zeta potential and morphology of membrane surface mainly influence membrane fouling. The aim of the present study is to reveal the correlation between membrane surface morphology and membrane fouling by use of humic acid solution and to investigate the efficiency of backwashing by water, which is applied to restore membrane flux. Cellulose acetate butyrate (CAB) hollow fiber membranes were used in the present study. To obtain the membranes with various surface structures, membranes were prepared via both thermally induced phase separation (TIPS) and nonsolvent-induced phase separation (NIPS) by changing the preparation conditions such as polymer concentration, air gap distance and coagulation bath composition. Since the membrane material is the same, the effects of hydrophilicity and zeta potential on membrane fouling can be ignored. More significant flux decline was observed in the membrane with lower humic acid rejection. For the membranes with similar water permeability, the lower the porosity at the outer surface, the more serious the membrane fouling. Furthermore, the effect of the membrane morphology on backwashing performance was discussed.     

Reconstruction of morphology of micron-sized,monodisperse composite polymer particles by the solvent-absorbing/releasing method

Micron-sized, monodisperse polystyrene (PS)/poly(n-butyl methacrylate) (PBMA) (2/1 w/w) composite particles having different morphologies were prepared by the solvent-absorbing/releasing method (SARM). There was an obvious influence of the releasing rate of toluene from the toluene-swollen composite particles on the reconstructed morphology by the SARM. In the case of fast release, the reconstructed morphology was a bicontinuous structure that is similar to that formed by spinodal decomposition. On the other hand, in the case of slow release, a hemispherical structure was formed that consisted of PS and PBMA phases.Part CCLIV of the series Studies on Suspension and Emulsion     

pH值对硅油乳液Zeta电位及其制备的影响

1994年,T．M．Obey和V．Brian采用二甲基二乙氧基硅烷在氨水催化剂下进行乳液聚合,获得了具有较好单分散性的聚二甲硅油乳液。本文研究了pH值对二甲基二乙氧基硅乳液Zeta电位的影响,比较了有相同单体浓度的单相体系在低pH值(酸性)和高pH值(碱性)条件下乳液聚合的规律,以期对硅烷乳液制备做更进一步的研究。     

Influence of side chains assembly on the structure and transport properties of comb-like polysiloxanes in hydrocarbon separation

We have synthesized a number of comb-like polysiloxanes with linear, branched, cyclic and silicon-containing substituents; most of them are new and previously not studied polymers. The physicochemical properties of comb-like polysiloxanes have been systematically investigated. Differential-scanning calorimetry and wide-angle X-ray scattering data revealed the side-chain microphase assembly for polymers with linear aliphatic substituents, while the polymers with bulky substituents did not form a microphase. It is shown that the ratio of microphase in the polymer is greater, the closer the values of the thickness of the microphase layer and the length of the cross-link. The effect of the side-chain substituent on the hydrocarbon transport properties of comb-like polysiloxanes was studied. All synthesized polymers are promising as membrane materials for a vital process of hydrocarbon separation. This is associated with an increase in the solubility selectivity of n-butane/methane because the solubility coefficient of methane sharply decreases when long side chains are introduced into the polysiloxane. It was shown for the first time that microphase forming polymers have a significantly higher butane/methane selectivity (23.2–27.5) than polysiloxanes not forming a microphase (selectivity 12.3–20.0). The effect is demonstrated on polysiloxanes with various types of side substituents. It was revealed that for the comb-like polysiloxanes, the diffusivity selectivity and permselectivity are proportional to the fraction of the side-chain microphase in the polymer. With the increase in the hydrocarbon microphase share, the diffusion coefficient of the permanent gas methane is decreasing more rapidly than n-butane, which dissolves well in hydrocarbons and plasticizes polymer. Consequently, the polymers forming the microphase have a higher selectivity C₃₊/CH₄ in the separation of a multicomponent hydrocarbons mixture.     

New breathable and waterproof coatings for textiles: effect of an aliphatic polyurethane on the formation of PEEK-WC porous membranes

PEEK-WC is an amorphous polyetheretherketone with high chemical stability, excellent thermal resistance and significant solubility in various solvents. It has been used to prepare flat membranes by the phase inversion technique. The water vapour permeability through a porous PEEK-WC film was 1350 g/m² day at 26 °C and its liquid entry pressure (LEP) of water equivalent to a column of 2.0 m. These values were remarkably improved by addition of an aliphatic ether polyurethane (PU) into the PEEK-WC/DMF dopes: the water vapour flux was increased up to 2000 g/m² day and the LEP was equivalent to 12.5 m. This improvement is correlated to the different structure of the membranes: a spongy, porous and almost symmetric structure for the PEEK-WC/PU membranes, and an asymmetric structure with fingers for PEEK-WC membrane. The presence of PU influences also the mechanical properties of the blend membranes. The role of the PU on the resulting membrane morphology is rationalised on the basis of the mechanism of phase separation.     

Application of a pH responsive multimodal hydrophobic interaction chromatography medium for the analysis of glycosylated proteins

Protein glycosylation has significant effects on the structure and function of proteins. The efficient separation and enrichment of glycoproteins from complex biological samples is one key aspect and represents a major bottleneck of glycoproteome research. In this paper, we have explored pH multimodal hydrophobic interaction chromatography to separate glycosylated from non-glycosylated forms of proteins. Three different proteins, ribonuclease, invertase and IgG, have been examined and different glycoforms have been identified. The media itself shows strong responsiveness to small variations in pH, which makes it possible to fine-tune the chromatographic conditions according to the properties of the protein isolated. Optimal glycoprotein separation has been obtained at pH 4. The pH responsive multimodal HIC medium in contrast to conventional HIC media is able to resolve contaminating DNA.     

Influence of solid surface on the compatibility in polymer blends produced in situ

Blends of linear polyurethane and poly(methyl methacrylate) were obtained in situ in the course of simultaneously proceeding reactions of polymerization and polyaddition. The effect of filler nanoparticles on the thermodynamic properties of the systems was investigated. Introduction of filler into the monomer mixture before curing increases the compatibility of final systems, as follows from diminishing thermodynamic interaction parameters. The reverse correlation has been established between the interaction parameter and the fraction of an interfacial region between two phases, its origin being the result of incomplete phase separation. Introducing filler into the reaction system determines simultaneously the increasing compatibility and increasing fraction of an interfacial region, i.e., prevents phase separation. Both effects are due to increasing of the interaction between two polymeric components at the interface with solid and changing conditions of incomplete phase separation in the course of reaction.