Highly improved adsorption selectivity of L-phenylalanine imprinted polymeric submicron/nanoscale beads prepared by modified suspension polymerization

Molecularly imprinted polymer (MIP) submicron/nanoscale beads selective for L-Phenylalanine (L-Phe) and D-Phe as well as non-imprinted beads were prepared by modified suspension polymerization involving agitation of the reaction mixture at high rotation speed under safe radical conditions. The effects of pH, template and concentration of racemate solution on the performance of the phenylalanine (Phe) imprinted polymeric submicron/nanoscale beads were studied. L-Phe-imprinted submicron/nanoscale beads prepared for the first time by modified suspension polymerization showed enhanced adsorption capacity and selectivity over those of D-Phe imprinted and non-imprinted beads. Maximum adsorption capacity, 0.35 mg/g, and selectivity, 1.62, of L-Phe imprinted submicron/nanoscale beads were higher than the adsorption capacities, 0.30 and 0.19mg/g, and selectivities, 1.59 and 1.02, of D-Phe imprinted and nonimprinted submicron/nanoscale beads, respectively. FE-SEM analyses revealed that L- and D-Phe imprinted beads were larger (100 nm–1.5 μm) than non-imprinted nanobeads (100–800 nm). ¹³C CP-MAS NMR spectroscopy helped in correlating the bead sizes and the extent of reaction during polymerization. Similarly, FT-IR study was used for evaluation of structural characteristics of the prepared Phe-imprinted and non-imprinted beads. The preparation of Phe-imprinted submicron/nanoscale beads with improved adsorption and separation properties and the study of effect of template on the size and performance of the prepared beads are suitable from both economical and research point of view in MIP field.     

N - BOC -L-色氨酸分子印迹聚合物的手性拆分

以分散聚合法制备的聚苯乙烯微球为种子,采用单步溶胀悬浮聚合法,N - BOC -L -色氨酸为模板分子,丙烯酰胺为功能单体,乙二醇二甲基丙烯酸酯为交联剂,在水相中成功制备了分子印迹聚合物微球,吸附实验表明,印迹聚合物对模板N - BOC -L-色氨酸有良好的吸附性,该聚合物作为液谱固定相,实现了模板与其对映体的快速基线...     

Preparation of Glutathione Molecularly Imprinted Polymer Microspheres by Reversed Phase Suspension Polymerization

Molecularly imprinted polymer microspheres (MIPMs) for Glutathione had been prepared by the reversed phase suspension polymerization method; MIPMs were synthesized by using acrylamide and N-vinyl pyrrolidone as functional monomers. N,N’-methylenebisacrylamide and dimethyl diallyl ammonium chloride were the cross-linkers and H₂O₂ and Vc were redox initiators, Span-80 was the surfactant used and cyclohexane was the oil phase. Our work can provide a method to obtain ball MIPMs, and in this way, the destruction of acting sites because powdery MIPMs could be avoided. Moreover, the low concentration of cross-linker results in imprinted sites not being formed during the reversed phase suspension polymerization. The double cross-linkers not only solved this problem, but they also enlarged the selection range of the template, monomer and cross-linker. Simultaneously, there’s obviously a significant amount of synergy between the two cross-linkers that perhaps improve the adsorption capacity and selectivity. The conditions were investigated and optimized, and the optimum conditions were obtained as follows: the ratio of n_AM/n_NVP was 2; the optimum temperature and time were 50°C and 4.5 h; and, the dosage of GSH, DMDAAC and Vc were 0.8 g, 14 g and 0.023 g, respectively, under the optimum conditions, GSH-MIPM was prepared and showed the adsorption capacity was 75 mg · g^?1. Also, based on the samples prepared at the starting process and under optimal conditions, the adsorption kinetics and adsorption isotherm were investigated and analyzed, respectively.     

Emulsification in batch emulsion polymerization

Dispersion of liquid–liquid systems is often applied in industrial processes such as extraction, suspension, and emulsion polymerization. The influence of emulsification of the monomer in the aqueous phase on the course and outcome of the batch emulsion polymerization of styrene has been studied. A visual criterion was applied for determining the lowest impeller speed for sufficient emulsification (N*). It appeared that in polymerization experiments under the same conditions, N* was the critical value above which no further increase in polymerization rate was observed. Using a turbine impeller instead of a pitched blade impeller as well as using a larger impeller diameter provides better emulsification at constant power input. The results indicate that scale‐up with constant impeller tip speed is most appropriate in case of a turbine impeller. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3225–3241, 1999     

Preparation of monodisperse PMMA particles by dispersion polymerization of MMA using poly(styrene-co-methacrylic acid) copolymer as a steric stabilizer

Dispersion polymerization of MMA was conducted using poly(styrene-co-methacrylic acid) copolymer as a steric stabilizer in an aqueous methanol medium. Various composition copolymers were easily prepared with a conventional radical polymerization by changing the monomer ratios of styrene to methacrylic acid, and were employed as a steric stabilizer for dispersion polymerization. The copolymers prepared with monomer ratios of 1.25–1.50 were found to be suitable steric stabilizers for dispersion polymerization. A very small amount of copolymer (0.6 wt% based on MMA) could act as a steric stabilizer effectively to obtain monodisperse PMMA particles. The particle size decreased with increasing the solvent polarity from 4 to 0.14 μm.     

喹唑啉分子印迹聚合物微球的吸附特性

以2,4-二氯-6,7-二甲氧基喹唑啉(DCQAL)为模板分子,采用单步溶胀聚合法制备了粒径均匀的分子印迹聚合物微球(M IPM s),并用静态吸附法研究了功能单体、三乙胺及水对M IPM s吸附性能的影响,考察了微球的识别性能。制得的M IPM s主要靠氢键作用吸附与识别模板分子,甲基丙烯酸(MAA)与模板分子间能产生较强的氢键作用,以其为功能单体制得的M IPM s具有较好的吸附与识别性能,其高亲和力与低亲和力结合点的最大表观吸附量分别为17.53μmol/g和117.02μmol/g,以4-氯-6,7-二甲氧基喹唑啉(CQAL)为竞争底物,其分离因子α达1.78。往吸附液中添加三乙胺或少量水会减弱M IPM s的吸附能力。     

Synthesis and regular reflection property of cocoon-like poly(methyl methacrylate) particles by seeded suspension polymerization

Synthesis and optical properties of cocoon-like poly(methyl methacrylate) (CPM) particles in the size range of D _n  = 3.0–6.5 μm were studied. The synthesis of these anisotropic particles consists of two steps. The spherical poly(methyl methacrylate) (PMA) particles (D _n  = 2.2–5.5 μm) cross-linked by 0.2–0.8 wt% ethylene glycol dimethacrylate (EGDMA) were prepared by dispersion polymerization, using a combination of poly(vinyl pyrrolidone) (PVP) and sodium di-(2-ethylhexyl) sulfosuccinate (NaEHS) as a stabilizer in 94:840 water–methanol. Then, a suspension polymerization of 9:1 methyl methacrylate (MMA)/EGDMA in the presence of the PMA particles as seed at 85 °C in water gave non-spherical, cocoon-like CPM particles, depending on the cross-linking densities of PMA particles. The cocoon-like CPM particles (D _n,c  = 4.0 μm) showed the characteristic features of regular reflection, which can not be attained for conventional poly(methyl methacrylate) particles with a spherical shape. The effects of seed PMA particles with different properties on the formation of cocoon-like CPM particles and their regular reflection properties are described.     

Influence of emulsifiers on particle size and particle size distribution of PVC latex synthesized by miniemulsion polymerization

We synthesized poly(vinyl chloride) (PVC) latexes via miniemulsion polymerization using a mixture of cetyl alcohol (CA) and sodium lauryl sulfate (SLS). A vinyl chloride miniemulsion is easily prepared by conventional mechanical stirring. Experimental design methods were applied to investigate the effects of composition and polymerization conditions on average particle size (APS) and particle size distribution (PSD) of the latexes produced. The APS of the latexes produced ranged from 0.4–0.7 μm. When the APS of the latex produced was above 0.7 μm, the resulting latex was highly unstable. The emulsifier ratio (CA/SLS) was the most prominent factor influencing APS and PSD.     

氯霉素分子印迹聚合物功能单体筛选及分子识别性能

以氯霉素(CAP)为模板,采用分子动力学和紫外光谱法分析不同功能单体与模板分子间的相互作用情况以辅助筛选单体,并进行实验印证。分子动力学计算出结合能ΔE和紫外光谱最大吸收峰红移程度大小顺序均为甲基丙烯酸(MAA)>丙烯酸(AA)>丙烯酰胺(AM)>甲基丙烯酸甲酯(MMA),且n(MAA):n(CAP)=1:4时MAA与CAP间已有较强的相互作用。由不同功能单体合成的CAP分子印迹聚合物微球(MIPMs)的静态吸附实验表明,在甲醇溶液中,以MAA为功能单体合成的MIPMs对模板CAP的吸附性能最好,饱和吸附量为470.4μmol/g,AA和AM次之,分别为397.5μmol/g和378.3μmol/g,MMA最小,为172.8μmol/g,该结果与分子动力学计算及紫外光谱分析结果相吻合。以MAA为功能单体优化制备MIPMs,SEM显示所得聚合物微球具有良好的单分散性,平均粒径为8.44μm,分散系数为14.2%。最后研究不同用量MAA合成的CAP-MIPMs的分子识别性,实验发现,在各MAA用量下,所得MIPMs对CAP的静态分配系数均高于结构类似物,在n(CAP):n(MAA)=1:4时,其静态分配系数达到111.63 mL/g,CAP与甲砜霉素(TAP)和氟甲砜霉素(FF)间的分离因子分别为4.57和2.78,具有明显的特异识别性。     

单步溶胀聚合法制备单分散分子印迹聚合物微球

用无皂乳液聚合法制得的微米级聚苯乙烯微球为种球,以N-甲基天门冬氨酸(NMA)为模板分子,通过单步溶胀聚合法在水相中制备了单分散分子印迹聚合物微球(MIPMs)。研究了影响种球溶胀的因素,并对MIPMs的结构进行了表征。实验表明,单步溶胀聚合法能够制得粒径2~3μm、单分散性好的MIPMs,且具有较好的特异吸附性能。Scatchard分析表明,MIPMs在识别NMA过程中存在两类结合位点,计算得到高亲和力的结合位点的离解常数KD1和最大表观结合常数Bmax1分别为0.223 mmol/L和2.12μmol/g,低亲和力的结合位点的离解常数KD2和最大表观结合常数Bmax2分别为5.34 mmol/L和36.42μmol/g。     

Adsorption of carbon dioxide using polyethyleneimine modified silica gel

To find an ideal adsorbent for carbon dioxide capture, a new polyethyleneimine modified silica gel material was synthesized with a simple procedure. Three silica gel materials with various particle sizes (15, 25 and 40–63 μm) were prepared and functionalized with polyethyleneimine. The carbon dioxide adsorption amounts of modified silica gel and non-modified silica gel were calculated using a mass balance equation at three different temperatures (298.15, 308.15 and 318.15 K), respectively, and the influence of gas pressure and particle size on adsorption was discussed. Experimental data showed that the carbon dioxide adsorption capacity of modified silica gel was better than non-modified silica gel, and the adsorption capacity gradually decreased with increasing particle size. The smaller particle size (15 μm) PEI modified silica gel had the largest adsorption capacity, at 298.15 K, and the adsorption amounts of various particle sizes of PEI-silica better fit the Langmuir isotherm model.     

CRITICAL IMPELLER SPEED FOR SOLID SUSPENSION IN MULTI-IMPELLER AGITATED CONTACTORS: SOLID-LIQUID SYSTEM

The critical impeller speed for suspension of solid particles (N_js) has been measured in multi-impeller mechanically agitated contactors of 0.15 and 0.30m id and 1.0 m height. Three types of impellers, i.e. disk turbine (DT), pitched turbine downflow(PTD) and pitched turbine upflow(PTU) were used. The number of impellers used in the 0.3 m and 0.15 m id reactors were three and four, respectively. The distance maintained between two impellers was equivalent lo the tank diameter. The effect of impeller type and diameter, particle size and loading, and clearance of the bottom impeller from the reactor bottom was studied and results compared with those of single impeller agitated contactors. PTD impeller was found to be more efficient for solid suspension. The N_js values obtained in reactors with multiple impeller are essentially the same as those observed in single impeller reactor and the bottom impeller plays dominant role in determining the N_js, values. An empirical correlation has been proposed for estimation of N_js and an attempt has been made to explain the mechanism of suspension in multi-impeller agitated reactor.     

Preparation and property of porous hydroxyapatite as an inorganic dispersant used in suspension polymerization

The porous hydroxyapatite (HAP) for suspension polymerization dispersant was prepared using calcium carbonate and phosphoric acid as raw materials. The samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and BET nitrogen adsorption. The results show that the prepared HAP has a porous structure, low particle density, large specific surface area, uniform particle size and does not agglomerate easily between the particles. The preparation conditions for the HAP were optimized as follows: solid content of calcium carbonate aqueous suspension 90 g/L, concentration of phosphoric acid 1.0 mol/L, reaction/aging temperature 50°C, and aging time 3 h. The HAP prepared under optimal preparation conditions has 106.8 m²·g⁻¹ of specific surface area, which is about 1.5–1.8 times asmuch as that of Japanese HAP or commercial HAP. Its application result in the suspension polymerization of styrene show that the porous HAP dispersant has high surface activity, excellent suspension dispersibility and stability and can markedly improve the quality of polystyrene beads. __________ Translated from Journal of Sichuan University (Engineering Science Edition), 2006, 38(6): 73–78 [译自: 四川大学学报(工程科学版)]     

充气条件下多层桨悬浮颗粒的临界转速

在直径为386 mm 的通气多层桨搅拌釜中,实验考察了下层搅拌桨型、挡板和气体分布器等对颗粒悬浮临界搅拌转速的影响,这对工业过程的设计和放大具有一定的指导意义.     

Development of superparamagnetic functional carriers and application for affinity separation of subtilisin Carlsberg

Superparamagnetic functional carriers to obtain high selectivity were reported in this study. Magnetic carriers with epoxy groups were synthesized by spraying suspension polymerization (SSP). The measurement of scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) showed that the magnetic carriers have a narrow size distribution and displayed superparamagnetic characteristics. The magnetic carriers with epoxy groups were modified by various affinity ligands to magnetic functional carriers such as copper-IDA carriers, benzamidine carriers and phenylboronic acid carriers. The effects of medium pH and subtilisin Carlsberg concentration on adsorption capacity were investigated. It was found that phenylboronic acid and benzamidine immobilized magnetic carriers were effective magnetic carriers for affinity adsorption of subtilisin Carlsberg, and the maximum adsorption capacity (about 65 mg/g) was obtained at pH 9.5. The adsorbed subtilisin Carlsberg was also desorbed successfully by using dissociation agents, and the recovery of the enzyme activity was still around 85%.     

The effect of flow reversal on solids suspension in agitated vessels

Flow patterns in agitated vessels are influenced by geometry, particularly impeller diameter and impeller off-bottom clearance. Large impellers and/or high off-bottom clearances lead to reversed flow in which the flow at the base of the vessel is radially-inward as opposed to radially-outward as expected with axial-flow impellers. Reversed flow is detrimental in solids suspension agitation because inordinately high torque and power are required to achieve suspension. This work experimentally characterizes the effect of flow reversal on solids suspension performance, including guidelines for avoiding flow reversal with straight-blade turbines, pitched-blade turbines, and high-efficiency impellers.     

Rapid synthesis of thin SAPO-34 membranes using microwave heating

SAPO-34 membranes were prepared by microwave (MW) heating method using a colloidal solution containing tetraethylammonium hydroxide as a template. SAPO-34 in the form of seed and membranes were investigated for their properties such as morphology, pore characteristic, crystallinity and thickness, using characterization method of scanning electron microscope (SEM), X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), FT-IR and nitrogen adsorption-desorption. SAPO-34 membrane was also prepared using conventional hydrothermal heating and studied for its comparison with those formed by MW heating. SAPO-34 membrane containing homogenous SAPO-34 crystals with average size of ~0.7 μm was formed during MW heating. Compare to the conventional hydrothermal heating, MW heating facilitates formation of SAPO-34 crystals with narrower size distribution due to the highly uniform volumetric heating provided by microwave heating. MW heating was able to produce thinner SAPO-34 membrane (1–2 μm) where as hydrothermal heating formed thicker SAPO-34 membrane (~3.6–5.5 μm). The synthesis time for membrane formation was significantly shortened from 24 h for conventional hydrothermal heating to 2 h for microwave heating at 200 °C.     

Emulsification in batch‐emulsion polymerization of styrene and vinyl acetate: A reaction calorimetric study

Dispersion of liquid–liquid systems is commonly applied in industrial processes such as extraction, suspension, and emulsion polymerization. This article describes the influence of the quality of emulsification on the course and outcome of a batch‐emulsion polymerization of styrene and vinyl acetate. From visualization experiments and polymerizations in combination with reaction calorimetric studies, a critical impeller speed, N*, can accurately be determined for a particular reactor setup and a given recipe. The results show that styrene–water emulsions are more difficult to emulsify than vinyl acetate–water emulsions. In general, a large turbine impeller appears to be more effective in emulsifying monomer–water dispersions than a pitched‐blade impeller. In addition, for vinyl acetate emulsion polymerization, the possibility of premixing the reaction mixture has been investigated. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 944–957, 2001     

无挡板搅拌槽中液－固体系的分散特性

在内径0.3 m、高0.45 m的无挡板搅拌槽内,采用直径0.15 m的三叶70o下推斜叶透平桨(PBTD, Pitched Blade Turbine Downflow)进行水-二氧化硅两相体系液固分散特性的研究. 应用PC-6A粉体浓度测量仪对体系中颗粒局部浓度进行测定. 考察了颗粒平均相含率为0.005的条件下,不同搅拌转速、搅拌桨离底高度对颗粒局部浓度分布的影响. 结果表明,采用较高搅拌转速、较低的搅拌桨离底高度有利于固体颗粒的悬浮. 本实验中,在搅拌转速为173 r/min、搅拌桨离底高度为0.08 m的操作条件下,颗粒悬浮效果最好.     

Adsorption of carbon dioxide on ionic liquids-modified active carbons and amino-modified polymer

Active carbons with various particle sizes (38–150, 300–500 and 800–1,200 μm) were modified by ionic liquids (ILs), and organic polymer was modified by acrylamide using a simple procedure, and these materials were applied to capture carbon dioxide (CO₂). The CO₂ adsorption amounts were calculated using a mass balance equation at three different temperatures (298.15, 308.15 and 318.15 K), respectively, and the influences of gas pressure, particle size and temperature on adsorption were discussed. Experimental results showed that the CO₂ adsorption capacity of ILs-modified active carbons was better than amino-modified polymer, and the smaller particle size (38–150 μm) ILsmodified active carbons had the largest adsorption capacity at 298.15 K. Compared with previous research about polyethyleneimine (PEI)-modified silica gel, the adsorption amount of CO₂ on ILs-modified active carbons has been greatly improved with lower cost.