Synthesis and evaluation of polymer-based zwitterionic stationary phases for separation of ionic species

Three different zwitterionic functional stationary phases for chromatography were synthesized on the basis of 2-hydroxyethyl methacrylate (HEMA) polymeric particles. Two synthesis routes, producing materials designated S300-ECH-DMA-PS or S300-TC-DMA-PS, involved activation of the hydroxyl groups of the HEMA material with epichlorohydrin or thionyl chloride, respectively, followed by dimethylamination and quaternizing 3-sulfopropylation with 1,3-propane sultone. The third route was accomplished by attaching methacrylate moieties to the HEMA through a reaction with methacrylic anhydride, followed by graft photopolymerization of the zwitterionic monomer 3-[N,N-dimethyl-N-(methacryloyloxyethyl)ammonium] propanesulfonate, initiated by benzoin methyl ether under 365-nm light. According to elemental analyses, both the S300-ECH-DMA-PS and S300-TC-DMA-PS materials appeared to have overall charge stoichometries close to unity, whereas the grafted material, S300-MAA-SPE, seemed to carry an excess of anion exchange sites in addition to the zwitterionic groups. Yet all three zwitterionic stationary phases were capable of separating inorganic anions and cations simultaneously and independently using aqueous solutions of perchloric acid or perchlorate salts as eluent, albeit with markedly different selectivities. On the S300-TC-DMA-PS and S300-MAA-SPE materials, the retention times increased for cations and decreased for anions with increasing eluent concentration, whereas with the S300-ECH-DMA-PS material, the retention times of both anions and cations decreased with increasing eluent concentration. These results demonstrate the importance of choosing appropriate synthesis conditions in order to prepare covalently bonded zwitterionic separation materials with an acceptable charge balance.     

Control of electroosmotic flow and wall interactions in capillary electrophoresis capillaries by photografted zwitterionic polymer surface layers

A novel capillary with covalently bonded zwitterionic surface modification was prepared by photograft polymerization of the zwitterionic monomer N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl)ammonium betaine, onto the inner surface of a UV-transparent fused-silica capillary. Although the zwitterionic moieties in the resulting polymeric "tentacles" comprise both a positive quaternary ammonium group and a negative sulfonate group, the coating has a net zero charge. The electroosmotic flow (EOF) was therefore extensively suppressed on the grafted capillary compared to the native silica capillary and to the silica capillary that had been activated for graft polymerization by reaction with 3-(methacryloyl)oxypropyltrimethoxysilane. It was also found that the EOF can be varied by adding chaotropic anions or divalent cations such as perchlorate ion and magnesium ion to the running buffer, due to the interaction between these ions and zwitterionic functional group. This provides a new way of altering the EOF and the wall interaction without changing the pH or the overall ionic strength of the separation buffer. The influence of pH and ionic strength of separation buffer on the EOF were also investigated to optimize the separation conditions. Good separations of a mixture containing eight inorganic anions were achieved within 5 min under optimal conditions by capillary zone electrophoresis. The newly prepared capillary was also well suited for the separation of peptides or proteins.     

Monolithic column with zwitterionic stationary phase for capillary electrochromatography

A capillary electrochromatography (CEC) monolithic column with zwitterionic stationary phases was prepared by in situ polymerization of butyl methacrylate, ethylene dimethacrylate, methacrylic acid, and 2-(dimethyl amino) ethyl methacrylate in the presence of porogens. The stationary phases have zwitterionic functional groups, that is, both tertiary amine and acrylic acid groups, so the ionization of those groups on the zwitterionic stationary phase was affected by the pH values of the mobile phase, and further affects the strength and direction of the electroosmotic flow (EOF). Separations of alkylbenzenes and polycyclic aromatic hydrocarbons based on the hydrophobic mechanism were obtained. Separation of various types of polar compounds, including phenols, anilines, and peptides, on the prepared column were performed under CEC mode with anodic and cathodic EOF, and different separation selectivities of those polar analytes were observed on the monolithic capillary column by using mobile phases with different pH values.     

Novel polyzwitterion shell with adaptable surface chemistry engineered to enhance anti-fouling and intracellular imaging of detonation nanodiamonds under tumor pHe

In this work, zwitterionic polymer (polyzwitterion) coated nanodiamonds (ND) with tumorous pH responsiveness were prepared for efficient application of commercial NDs in tumor cells imaging. Poly(carboxybetaine methacrylate) was firstly grafted on the pristine NDs (PCBMA-@-NDs) by surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization. To achieve pH responsiveness and activated interaction with tumor cells, PCBMA-@-NDs were subsequently modified with benzene sulfonamide (PCBSA-@-NDs) via one step carbodiimide chemistry. The surface polymer functionalization was characterized by FTIR, ¹H NMR and TGA, and PCBMA-@-NDs and PCBSA-@-NDs showed great dispersibility, enhanced fluorescence intensity and excellent antifouling property in contrast to pristine NDs. Moreover, PCBSA-@-NDs was able to switch zwitterionic surface (at pH 7.4) reversibly into positive charge (at pH 6.5) via protonated or deprotonated acylsulfonamide. As expected, PCBSA-@-NDs demonstrated higher cell affinity and better imaging performance than those of zwitterionic NDs at tumor slight acid environment, proven by fluorescence microscopy and flow cytometry. Overall, we provide a feasible and valuable strategy to construct smart NDs, thus encouraging the application of cost-effective fluorescence nanomaterials in biomedical fields.     

氯化镁介质中氧化铝表面的相互作用力

利用原子力显微镜研究了氯化镁介质中氧化铝表面的相互作用力随盐浓度、ｐＨ的变化规律．在中性条件下;当ＭｇＣｌ_２盐浓度由１０^－５ｍｏｌ／Ｌ增加到１０^－2ｍｏｌ／Ｌ时,长程排斥作用由于双电层压缩,作用范围从一百多纳米减弱到十几纳米,实验测得的双电层厚度的实际值与理论值较好的吻合．保持ＭｇＣｌ_２介质浓度不变;ｐＨ由３．６４变化到９．０９;氧化铝表面的相互作用始终表现为排斥力,与测得的Ｚｅｔａ电位值始终为正值相一致．当ｐＨ＝９．５时,由于镁离子的水合氢氧化物在氧化铝表面的特性吸附,产生了短程非静电徘斥力,首次用原子力显微镜证实了Ｍｇ^２＋特性吸附层的存在,厚度约为５ｎｍ。     

Stability of Silver and Pyrex in Perchloric Acid-Silver Perchlorate Solutions and in Conductivity Water

The stability of mint silver, purified mint silver, and Pyrex fritted crucibles in aqueous solutions of perchloric acid, in aqueous solutions of perchloric acid containing silver perchlorate, and in conductivity water at room temperature was determined. The stability of the silver in various states of subdivision was studied. The corrosion current-density for mint silver in sheet form is 1.1 × 10⁻⁸ amp cm⁻² for 20 percent aqueous solutions of perchloric acid, 1.3×10⁻⁹ amp cm⁻² for 20 percent aqueous solutions of perchloric acid containing 0.5 percent silver perchlorate, and within the limits of detection is zero for conductivity water. Pyrex has high stability at 25° C in 20 percent aqueous solutions of perchloric acid and in 20 percent aqueous solutions of perchloric acid containing 0.5 percent silver perchlorate. Finely-divided silver contained in Pyrex crucibles was found to be highly stable when the crucibles were filled repeatedly with aqueous solutions of perchloric acid containing silver perchlorate, rinsed with conductivity water, and dried at 105° C. These observations are important in the determination of the faraday by the anodic dissolution of silver in aqueous solutions of perchloric acid which is now underway at the National Bureau of Standards.     

Zwitterionic sulfobetaine-grafted poly(vinylidene fluoride) membrane with highly effective blood compatibility via atmospheric plasma-induced surface copolymerization

Development of nonfouling membranes to prevent nonspecific protein adsorption and platelet adhesion is critical for many biomedical applications. It is always a challenge to control the surface graft copolymerization of a highly polar monomer from the highly hydrophobic surface of a fluoropolymer membrane. In this work, the blood compatibility of poly(vinylidene fluoride) (PVDF) membranes with surface-grafted electrically neutral zwitterionic poly(sulfobetaine methacrylate) (PSBMA), from atmospheric plasma-induced surface copolymerization, was studied. The effect of surface composition and graft morphology, electrical neutrality, hydrophilicity and hydration capability on blood compatibility of the membranes were determined. Blood compatibility of the zwitterionic PVDF membranes was systematically evaluated by plasma protein adsorption, platelet adhesion, plasma-clotting time, and blood cell hemolysis. It was found that the nonfouling nature and hydration capability of grafted PSBMA polymers can be effectively controlled by regulating the grafting coverage and charge balance of the PSBMA layer on the PVDF membrane surface. Even a slight charge bias in the grafted zwitterionic PSBMA layer can induce electrostatic interactions between proteins and the membrane surfaces, leading to surface protein adsorption, platelet activation, plasma clotting and blood cell hemolysis. Thus, the optimized PSBMA surface graft layer in overall charge neutrality has a high hydration capability and the best antifouling, anticoagulant, and antihemolytic activities when comes into contact with human blood.     

Combined effect of coulombic and van der Waals interactions in the chromatography of proteins.

We have recently proposed a theoretical framework for the effect of the eluting salt ionic strength of the eluent on the retention factor of proteins in ion-exchange chromatography of proteins. It is based on the solution of the linearized Poisson-Boltzmann equation for two oppositely charged planar surfaces in contact with a salt solution and describes the coulombic interaction between the protein and the oppositely charged stationary-phase surface. At sufficiently high salt concentrations in the mobile phase van der Waals interactions between the protein and the stationary phase become important. In this work we consider the effect of salt on the combined coulombic and van der Waals interactions by combining the electrostatic theory with the theory for van der Waals interactions. The combined theory describes the retention of proteins as a function of eluting salt concentration over a wide salt concentration range. The protein molecules are, according to the proposed theory, held in a diffuse layer close to the stationary phase and are not in a distinct layer, which is assumed in the traditional thermodynamic interpretation of the capacity factor. For this reason, we also examine the thermodynamic interpretation of the capacity factor when it is due to distant dependent interactions.     

Perchlorate adsorption and desorption on activated carbon and anion exchange resin

The mechanisms of perchlorate adsorption on activated carbon (AC) and anion exchange resin (SR-7 resin) were investigated using Raman, FTIR, and zeta potential analyses. Batch adsorption and desorption results demonstrated that the adsorption of perchlorate by AC and SR-7 resin was reversible. The reversibility of perchlorate adsorption by the resin was also proved by column regeneration test. Solution pH significantly affected perchlorate adsorption and the zeta potential of AC, while it did not influence perchlorate adsorption and the zeta potential of resin. Zeta potential measurements showed that perchlorate was adsorbed on the negatively charged AC surface. Raman spectra indicated the adsorption resulted in an obvious position shift of the perchlorate peak, suggesting that perchlorate was associated with functional groups on AC at neutral pH through interactions stronger than electrostatic interaction. The adsorbed perchlorate on the resin exhibited a Raman peak at similar position as the aqueous perchlorate, indicating that perchlorate was adsorbed on the resin through electrostatic attraction between the anion and positively charged surface sites.     

两步法LDPE/HSS表面光接枝的研究

采用两步表面光接枝方法研究了乙烯基苯磺酸(HSS)在低密度聚乙烯(LDPE)膜表面的接枝聚合,使LDPE膜表面有效强酸化．探讨了各反应条件对表面接枝的影响规律,利用称量法、表面水接触角测定法、红外光谱分析、扫描电镜观察等手段对表面接枝膜进行了表征。     

天然高分子吸水材料的制备工艺与性能评价

以天然薯粉为基本原料,采用直接聚合法和反相悬乳法两种不同方式,研究了淀粉接枝丙烯酸制备高叹水材料的工艺条件及产品性能,探讨了接枝剂用量、丙烯酸中和度、反应温度、反应时间等对产品吸水性能的影响,评价了下同方法制备所得吸水材料对淡、盐、肥水的吸水速率、吸水量、保水率和重复使用性能．研究结果表明,直接聚合法在简化工艺、降低成本等方面有明显优势,可制得吸水量约410g／g,吸盐水量约40g/g,吧乏吧水量约49g／g,且可多次重复使用的产品,具有广泛的工农业和市场应用前景．     

Preparation of thermosensitive gold nanoparticles by plasma pretreatment and UV grafted polymerization

This work is to develop an easy method of plasma treatment and graft polymerization to prepare thermosensitive gold nanoparticles. Gold nanoparticles (Nano-Au) were reduced by trisodium citrate combined with hydrogen tetrachloroaurate(III) tetrahydrate (chloroauric acid) and modified with 11-mercaptoundecanoic acid (MUA) by the self-assembly monolayers (SAM). The surface graft polymerization of N-isopropylacrylamide (NIPAAm) was carried out by two steps, using O₂ plasma pretreatment of the surface on MUA SAM modified Nano-Au to form the peroxide groups on Nano-Au(MUA), and then subsequently using UV light to induce grafting with thermosensitive polymer. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to direct investigation of the particle size and morphology in situ. The diameters of the gold nanoparticles measured from the TEM images are in good agreement with data measured at room temperature which is about 15 nm. The thermosensitive gold nanoparticles were characterized by chemical structure of surface (ESCA) and Fourier-transform infrared spectroscopy (FTIR). ESCA result suggests that plasma treatments can be employed to generate peroxides on the Nano-Au(MUA) for the subsequent UV graft polymerization of PNIPAAm.     

聚季铵盐与丙烯酰胺的接枝聚合

以环氧氟丙烷和二乙胺为原料，合成一种聚季铵盐；研究了过硫酸铵、异丙醇氧化还原体系引发聚季铵盐与丙烯酰胺的接枝聚合反应，应用IR对其结构进行了表征。并着重探讨了反应温度、反应时间、异丙醇浓度、原料配比对接枝聚合的影响。     

Polymer grafted hydroxyapatite whisker as a filler for dental composite resin with enhanced physical and mechanical properties

The objective of this study was to investigate the effect of surface graft polymerization of hydroxyapatite whisker (HW) on physical and mechanical properties of dental composite resin. Poly bisphenol A glycidyl methacrylate (Poly(Bis-GMA)) was grafted onto silanized hydroxyapatite whisker (SHW) via solution polymerization and the amount of the Poly(Bis-GMA) on the surface was effectively controlled by polymerization time. The obtained poly(Bis-GMA) grafted hydroxyapatite whisker (PGHW) with different polymer contents was filled into a resin matrix respectively, meanwhile the composites with HW and with SHW served as controls. Monomer conversion was characterized by Fourier transform infrared spectroscopy (FTIR) and volume shrinkage of the composite resin was measured with a density tester. Mechanical properties were tested with a universal testing machine. The results indicated that the composite filled with PGHW-1 h (graft ratio of poly(Bis-GMA): 8.5 wt.%) showed lower shrinkage and better mechanical properties, improving flexural strength by 6.5% and 11.9% compared with SHW filled composite and HW filled composite, respectively. However, PGHW with higher graft ratios aggregated seriously and formed defects in the composite, leading to deterioration of mechanical properties. It was revealed that the poly(Bis-GMA) on the surface of PGHW acted as a functional transition layer and enhanced interfacial compatibility and interaction between whisker and resin matrix, which facilitated the dispersion of PGHW in the composite and decreased the composite shrinkage. Thus, the graft polymerization of Bis-GMA on the surface of filler might be a promising modification method for the fabrication of dental materials.     

复合纳滤膜凝胶功能层的聚电解质特性

通过界面聚合的方法制备了以聚甲基丙烯酸二甲氨基乙酯(PDMAEMA)为交联预聚体,以微孔聚砜膜为基膜的复合纳滤膜;研究了凝胶表层的聚电解质特性.实验表明:荷电纳滤膜的表面具有一定的疏水性.交联凝胶层的溶胀度表现出pH、外加盐浓度、温度的响应性.     

Perchlorate removal by quaternary amine modified reed

We report a kinetic and equilibrium study of perchlorate adsorption onto giant reed modified by quaternary amine (QA) functional groups in batch reactors. The effect of pH, contact time, and initial perchlorate concentration on removal was investigated. The adsorption capacity for perchlorate was 169 mg/g on the modified reed (MR) particles ranging in size from 100 to 250 μm. The isotherm results were best described by the combined Langmuir-Freundlich equation. Optimum removal occurred in the pH range 3.5-7.0 and was reduced at pH>8.5. The maximum adsorption rate occurred within the first minute of contact and equilibrium was achieved within 7 min. A three-stage adsorption occurred. In stage 1, adsorption was rapid and was controlled by boundary layer diffusion. In stage 2, adsorption was gradual and was controlled by both boundary layer and intraparticle diffusion. In stage 3, adsorption reached a plateau. The kinetic results fit well with a pseudo second-order equation. The adsorption mechanism was explored using Zeta potential analysis and Raman spectroscopy. Zeta potential measurements showed that reed modification enhanced perchlorate removal by increasing the surface potential. Electrostatic attraction between perchlorate anion and positively charged quaternary amine groups on the MR was the primary mechanism responsible for perchlorate removal.     

High resolution of DL-tryptophan at high flow rates using a bovine serum albumin-multilayered porous hollow-fiber membrane

We describe a bovine serum albumin (BSA)-multilayer-adsorbed porous hollow-fiber membrane as a stationary phase that enables chiral separations at a high resolution and high rate. Epoxy-group-containing graft chains were uniformly immobilized on the surface of pores throughout a porous hollow-fiber membrane by radiation-induced graft polymerization. Subsequently, a diethylamino group as an anion-exchange moiety was introduced to the graft chains, which caused the chains to expand toward the interior of the pores due to mutual electrostatic repulsion. The expanding polymer chains provided multilayer binding sites for BSA as a chiral selector. BSA with a degree of multilayer binding of 4 specifically recognized L-tryptophan with a separation factor of 6.6 during permeation by a mobile phase (Tris-HC1 buffer) injected with a racemic solution of DL-tryptophan through the BSA-multilayered porous membrane. In addition, the separation factor was constant irrespective of flow rates of the mobile phase because of negligible diffusional mass-transfer resistance of tryptophan to BSA multilayered by the graft chains.     

HRP引发酚类与淀粉接枝共聚物的制备及结构性能表征

降解淀粉和酚类在辣根过氧化物酶(HRP)/H2O2的催化作用下进行自由基接枝共聚反应,制备了淀粉和酚类接枝共聚物。研究了淀粉降解程度、酚类单体配比、HRP用量、反应温度和pH对接枝改性淀粉结构与性能的影响。研究结果表明,用α-淀粉酶降解后的淀粉15与12g间苯三酚(PG)和20g对羟基苯磺酸钠(HBS)在5mg HRP/H2O2引发体系下,在30℃及pH值为7.0时反应5h制备的酚类与淀粉接枝共聚物具有较好的性能,其水溶液的表面张力为26.6mN/m,所鞣制皮革收缩温度(Ts)达到了78℃。用FT-IR、1 H NMR、UV-Vis和GPC等方法对产物的化学结构进行了表征。     

One‐Step Assembly of a Biomimetic Biopolymer Coating for Particle Surface Engineering

Advances in material design and applications are highly dependent on the development of particle surface engineering strategies. However, few universal methods can functionalize particles of different compositions, sizes, shapes, and structures. The amyloid‐like lysozyme assembly‐mediated surface functionalization of inorganic, polymeric or metal micro/nanoparticles in a unique amyloid‐like phase‐transition buffer containing lysozyme are described. The rapid formation of a robust nanoscale phase‐transitioned lysozyme (PTL) coating on the particle surfaces presents strong interfacial binding to resist mechanical and chemical peeling under harsh conditions and versatile surface functional groups to support various sequential surface chemical derivatizations, such as radical living graft polymerization, the electroless deposition of metals, biomineralization, and the facile synthesis of Janus particles and metal/protein capsules. Being distinct from other methods, the preparation of this pure protein coating under biocompatible conditions (e.g., neutral pH and nontoxic reagents) provides a reliable opportunity to directly modify living cell surfaces without affecting their biological activity. The PTL coating arms yeasts with a functional shell to protect their adhered body against foreign enzymatic digestion. The PTL coating further supports the surface immobilization of living yeasts for heterogeneous microbial reactions and the sequential surface chemical derivatization of the cell surfaces, e.g., radical living graft polymerization.     

窄分子量分布端羟基聚四氢呋喃的合成与表征

以高氯酸为催化剂,乙酸酐为促进剂及分子量调节剂,通过四氢呋喃阳离子开环聚合合成了分子量可控且分子量分布较窄(Mw/Mn1.2)的聚四氢呋喃,聚合产物端部含有乙酸酯基,经醇解后得到端羟基聚四氢呋喃(PTMEG)。探讨了聚合时间、高氯酸用量、乙酸酐用量、溶剂对聚四氢呋喃分子量(Mn)及分子量分布(Mw/Mn)的影响。研究表明,延长聚合时间、增加高氯酸及乙酸酐的用量均会造成Mn先升后降,但只有聚合时间对Mw/Mn会造成显著的影响,聚合时间为4h时Mw/Mn最小;加入CH2Cl2溶剂会降低聚四氢呋喃的Mn及Mw/Mn。采用凝胶渗透色谱-多角度激光散射联用仪(SEC-MALLS)对聚合产物的Mn及Mw/Mn进行了准确地测定,应用FT-IR、1 H-NMR表征了端羟基聚四氢呋喃大分子结构,利用DSC及TG研究了其热性能,结果表明,端羟基聚四氢呋喃的熔点及分解温度随着Mn的增加略有升高。