Immobilization of hydrophobic lipase derivatives on to organic polymer beads

A simple and effective method of lipase immobilization is described. Lipase from Candida rugosa was first modified with several hydrophobic modifiers before being adsorbed on to organic polymer beads. The soluble hydrophobic lipase derivatives adsorbed more strongly on to the various polymers as compared with the native lipase. The optimal adsorption temperature of the native and modified lipases on all the polymers was 40°C. The optimal pH of adsorption was between 6 and 7. Lipase immobilized in this manner produced high catalytic recoveries which were affected by the type of modifiers, degree of modification and type of supports used. Monomethoxypolyethylene glycol (1900) activated with p-nitrophenyl chloroformate was found to be the best modifier of the enzyme at 95% modification, for adsorption to the polymers. Increasing the degree of modification of the enzyme increased the activity which was immobilized. Generally, both native and hydrophobic lipase derivatives showed higher specific activities when immobilized on polar polymers compared with non-polar polymers.     

Development of porous polymer monolith by photoinitiated polymerization

Porous polymer monoliths have been successfully prepared by photoinitiated polymerization of butyl methacrylate (BMA) and ethylene glycol dimethacrylate (EDMA) monomers in porogenic solvent of methanol. Mercury intrusion porosimetry and scanning electron microscope are used to characterize the porous properties; nevertheless, the pore size obtained from both techniques is not comparable. The porous structure of the porous polymers is controlled by the phase separation during the polymerization and crosslinking. By varying the composition of the starting solution such as initiator fraction, BMA/EDMA ratio, porogen fraction, and UV intensity, porous polymers with median pore size from about 140 nm to 3 μm can be obtained, and the pore size distribution for majority of the porous polymers is also narrow. The results present a very positive prospect to microfluidic applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

S-enriched porous polymer derived N-doped porous carbons for electrochemical energy storage and conversion

Porous polymers have been recently recognized as one of the most important precursors for fabrication of heteroatom-doped porous carbons due to the intrinsic porous structure, easy available heteroatom-containing monomers and versatile polymerization methods. However, the heteroatom elements in as-produced porous carbons are quite relied on monomers. So far, the manipulating of heteroatom in porous polymer derived porous carbons are still very rare and challenge. In this work, a sulfur-enriched porous polymer, which was prepared from a diacetylene-linked porous polymer, was used as precursor to prepare S-doped and/or N-doped porous carbons under nitrogen and/or ammonia atmospheres. Remarkably, S content can sharply decrease from 36.3% to 0.05% after ammonia treatment. The N content and specific surface area of as-fabricated porous carbons can reach up to 1.32% and 1508 m²·g⁻¹, respectively. As the electrode materials for electrical double-layer capacitors, as-fabricated porous carbons exhibit high specific capacitance of up to 431.6 F·g⁻¹ at 5 mV·s⁻¹ and excellent cycling stability of 99.74% capacitance retention after 3000 cycles at 100 mV·s⁻¹. Furthermore, as the electrochemical catalysts for oxygen reduction reaction, as-fabricated porous carbons presented ultralow half-wave-potential of 0.78 V versus RHE. This work not only offers a new strategy for manipulating S and N doping features for the porous carbons derived from S-containing porous polymers, but also paves the way for the structure-performance interrelationship study of heteroatoms co-doped porous carbon for energy applications.     

Controlling porous properties of polymer monoliths synthesized by photoinitiated polymerization

Porous monoliths have been successfully prepared by photoinitiated polymerization of hydroxyethyl methacrylate and ethylene glycol dimethacrylate monomers in a porogenic solvent. By varying the composition of the starting solutions such as initiator fraction, monomer ratio and pore generator (porogen) fraction and type, as well as UV intensity, monoliths have been obtained with narrow pore size distribution and median pore size from about a few nanometres to a few micrometres. © 2012 Society of Chemical Industry     

Toward a continuous synthesis of porous carbon xerogel beads

A continuous process for producing porous carbon xerogel beads has been developed. It consists in injecting a pre‐cured aqueous solution of resorcinol and formaldehyde on top of a column filled with hot oleic acid. The latter is pumped on the top of the column and fed at the bottom, generating an upward flow that can be adjusted to match the terminal velocity of the settling beads. Thus, the bead residence time in the column can be adjusted to match the gelation time, allowing the beads to solidify before reaching the bottom of the vessel. The obtained beads are subsequently dried and pyrolyzed. The developed experimental setup proved the continuous synthesis of porous carbon beads is possible. Nevertheless, the shaping process caused various texture changes of the porous carbon, which mainly yields macropores instead of micro and mesopores. This process also leads to the build‐up of a denser skin around the beads. © 2018 American Institute of Chemical Engineers AIChE J, 64: 1049–1058, 2018     

Synthesis of silver/polymer colloidal composites from surface-functional porous polymer microspheres

This study presents a different colloidal silver (Ag)/polymer system where Ag nanoparticles are deposited uniformly onto surface-functional porous poly(ethylene glycol dimethacrylate-co-acrylonitrile) (poly(EGDMA-co-AN)) microspheres. The formation and morphology of the composite microspheres were characterized from electron microscopy and X-ray diffraction analyses. The significance of the present report is that owing to the high affinity between Ag and nitrile group (CN) on the large surface of the microspheres, the Ag nanoparticles having a face-centered cubic phase were incorporated evenly into the deep pores of the microspheres with fine size and size distribution. In the preservation test, the Ag/poly(EGDMA-co-AN) composite microspheres obtained showed an excellent anti-bacterial performance, elucidating a high applicability for a new preservative.     

Ordered porous polymer films via phase separation in humidity environment

A transition of morphology from island-like structure to disordered and ordered holes on the surface of polystyrene (PS) and poly(2-vinylpyridine) (PVP) blend films were observed with the increase of humidity. At appropriate weight ratio of PS/PVP and PS molecular weight, when humidity reached to a critical value, the hexagonal arrays of holes formed for PS/PVP blend films due to ‘breath figures’ stabilized by PVP with its strong hygroscopic characteristics during phase separation.     

Hierarchically porous polymeric materials from ternary polymer blends

Hierarchically porous polymers with controllable pore size were generated through a novel polymer blending strategy in an A/B/C–B–C ternary blend system. Polylactide/high-density polyethylene/poly(styrene-ethylene/butylene-styrene) triblock copolymer (PLA/HDPE/SEBS) was used as a model system to demonstrate this technique. During melt blending, the SEBS was driven into the HDPE phase owing to the presence of the PE block in the copolymer. With proper volume fractions of PLA/HDPE/SEBS (e.g., 50/25/25), a bi-modal, dual co-continuous morphology was obtained and hierarchically porous polymeric materials were further generated by selectively removing the PLA and SEBS phases. Annealing and compositional variation were further employed to control the pore size and it is shown that the length scales of the two co-continuous morphologies can be controlled independently.     

多孔微珠用于制备低密度BMC材料

采用多孔微珠为填料制备了不饱和聚酯低密度团状模塑料(BMC)。选取多孔微珠的粒径及掺量,短切玻璃纤维的长度及掺量为4因素,设计L16(44)正交试验,并结合示差扫描量热法(DSC)和扫描电镜(SEM)对复合体系的增强机理进行了研究。结果表明,制备轻质BMC材料的最佳条件为:多孔微珠的粒径<0.710 mm,掺量4%,短切玻纤长度6 mm,掺量30%,此时制得BMC材料密度为1.314 g/cm3,弯曲强度为81.50 MPa,满足国标GB/T 23641—2009对BMC弯曲强度的要求(≥80 MPa)。多孔微珠的蜂窝壁对树脂的固化起到了阻碍作用,固化时间延长,放热不完全,同时多孔微珠的填充使得树脂基体的应力分散不均,样品的表观密度和弯曲强度降低。     

Facile synthesis of bimodal porous silica and multimodal porous carbon as an anode catalyst support in proton exchange membrane fuel cell

A simple and easy sol-gel approach has been developed to directly synthesize in situ three-dimensionally interconnected uniform ordered bimodal porous silica (BPS) incorporating both the macroporosity and mesoporosity in the lattice without extra synthesis process performed in previous work. Multimodal porous carbon (MPC) was fabricated through the inverse replication of the BPS. The unique structural characteristics such as well-developed 3-D interconnected ordered macropore framework with open mesopores embedded in the macropore walls, large surface area (1120 m² g⁻¹) and mesopore volume (1.95 cm³ g⁻¹) make MPC very attractive as an anode catalyst support in polymer exchange membrane fuel cell. The MPC-supported Pt-Ru alloy catalyst has demonstrated much higher power density toward hydrogen oxidation than the commercial carbon black Vulcan XC-72-supported ones.     

交联聚合物溶液在孔隙介质中的流动与滞留行为

在内径为40 mm、长度为1500 mm的填充砂管中,在线测量了由部分水解聚丙烯酰胺和柠檬酸铝所形成的交联聚合物溶液在填充砂孔隙介质中的流动和滞留特性,考察了交联聚合物溶液的流动形态及流动速度对孔隙封堵位置的影响。结果表明,交联聚合物溶液在孔隙介质中的流动过程中,经过多次压力脉动最终导致一种局部性的非均匀封堵;随着流动线速度的增加,封堵位置与交联聚合物注入口间的距离呈非线性增大;对应于封堵现象的发生,可能存在一个临界注入量,只有当交联聚合物溶液的注入量大于该临界值时,才会对孔隙介质产生封堵作用。     

Wet foam stability and tailoring microstructure of porous ceramics using polymer beads

The microstructures of the porous ceramics are improved considerably using polymethyl methacrylate (PMMA) as a pore template since particles tend to adsorb irreversibly at the air-water interface. This paper presents a versatile approach for the production of porous SiO₂ ceramics by a process of direct foaming with the addition of PMMA beads. The adsorption free energy of the colloidal suspension was found to be 2.0?×?10⁹?kT. A wet foam stability of >80% was achieved using the surfactant hexylamine (0.05?M), which resulted in a colloidal suspension with the highest surface tension (116.2?mN?m^??1).     

Effect of porogenic solvent on the porous properties of polymer monoliths

Polymer monoliths with open pores and median pore size of about 15 nm–3 μm have been successfully synthesized by photoinitiated polymerization of butyl methacrylate and ethylene glycol dimethacrylate monomers. The solubility of the monomers in a porogenic solvent is determined by Hildebrand solubility parameter, and it is found that it has great effect on the pore size of the polymers synthesized. Polymers with larger pores are usually generated with poorer solvents for the monomers. However, polymers with different pore sizes and porosities have been obtained using porogenic solvents with similar Hildebrand solubility parameters. The evaporation rate of the porogenic solvents might be another critical factor affecting the properties of the polymer monoliths. Moreover, the effect of water as a cosolvent on the pore size and porosity of the polymers have also been investigated. Polymers with larger pore size have been prepared with the presence of water due to the occurrence of earlier phase separation in the polymerization. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

亲水性环氧聚合物磁性微球的制备及其固定化青霉素酰化酶

通过设计反相悬浮聚合体系,制备了聚甲基丙烯酸缩水甘油酯（GMA）-甲基丙烯酸羟乙酯（HEMA）- N,N′-亚甲基双丙烯酰胺（MBAA）亲水性磁性聚合物GHM微球。球中的Fe₃O₄微晶呈倒立尖晶石结构,在微球表面存在着大量环氧基和亲水性的羟基及酰胺等基团,这些功能性基团为青霉素酰化酶（PGA）的固定化提供了适宜的微环境;同时,GHM微球具有的大孔结构和较高的比表面积,使其制备的固定化酶的载酶量高,这些有利因素使得固定化酶PGA/GHM在37℃下水解青霉素G钾合成6-氨基青霉烷酸的表观活性达748 IU·g^-1。 PGA/GHM经15次重复使用,其催化活性未出现明显的衰减,在使用中,固定化酶在磁场的作用下能够快速沉降与产物分离。     

Enzymic synthesis of fatty esters by hydrophobic lipase derivatives immobilized on organic polymer beads

Lipase fromCandida rugosa was modified with several hydrophobic modifiers before being adsorbed onto organic polymer beads. The effects of different enzyme modifiers, supports, solvents, reaction temperatures, fatty acids, and alcohols on the activity of the immobilized enzyme were investigated. The immobilized lipases were good biocatalysts for esterification reactions in organic solvents. They exhibited high activities in all solvents tested, including polar solvents. The activity seemed to depend on the type of support rather than on the modifier of the enzyme. The medium polar support, XAD7, appeared to be the best for the modified lipases. The immobilized lipase favored the medium-chain fatty acids rather than the long-chain fatty acids as acyl donors. The alcohol selectivity of the enzyme was unchanged upon immobilization. The native and immobilized lipases favored the short-chain and terpene alcohols as nucleophiles.     

Adsorption of heavy metal ions from aqueous solutions by porous polyacrylonitrile beads

The adsorption of Cu(II), Ni(II), Zn(II), and Pb(II) from aqueous solutions on acrylonitrile copolymer sorbents was studied. We prepared five types of sorbents from polyacrylonitrile by varying its concentration in the initial polymer solution and the composition of the coagulation bath, aiming to achieve a different porous structure. The specific area, pore volume, and pore radius of the sorbents were determined on a porosimeter. The porous structure was studied by scanning electron microscopy. Modification of sorbents with sodium hydroxide and hydroxylamine was carried out to form amidooxyme and carboxylic groups with proven complex‐forming properties toward heavy metal ions. The optimal pH of the sorption of metal ions was found. The adsorption kinetics were investigated. The order of polymer sorbents toward the sorption of Pb(II), Cu(II), Ni(II), and Zn(II) ions, and the order of heavy metal uptake were determined for all types of sorbents. The effectiveness of heavy metal desorption and the coefficient of recovery of sorption ability were determined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3036–3044, 2002; DOI 10.1002/app.2334     

Electroplating and electroless plating of Ni through/onto a porous polymer in a flow cell

Porous Ni coatings on electrodes were produced by electroplating through the cells and pores of a generic high internal phase emulsion polymer (PHIPE), a styrene-ethylhexylacrylate-divinylbenzene copolymer, and subsequent thermal decomposition of the polymer template. Electroplating was carried out from flowing solutions through a polymer block fitted in the interelectrode gap of a flow-by cell. The mass transfer conditions and the flow regime in the cell were also characterized. The structure of the porous electrodeposits thus produced was determined by the distortion of the electric field through the cells and pores of the insulating polymer and depends on the current density and the thickness of the polymer layer. Porous deposits plated at 5 mA cm^–2 showed high utilization of electroactive surface area when used as hydrogen evolving cathodes from alkaline solutions. Finally, Ni/PHIPE composite foams were prepared by Ni electroless plating through the polymer pores and their electrochemical surface area was evaluated.     

两亲性聚合物多孔微球的制备研究

合成了具有悬挂双键的苯乙烯-二乙烯基苯多孔微球,在悬挂双键处接枝甲基丙烯酸甲酯,制成了一系列不同接枝度的两亲性聚合物多孔微球。考察了悬挂双键数量、反应时间等因素对接枝率的影响以及接枝率对微球形貌的影响。实验中通过观测澄清点,有效地控制了反应后期自加速现象对接枝率的影响。在反应时间25 m in时,制得了平均孔径为50 nm的两亲性多孔微球。将该微球用于对化妆品活性组分的负载,对极性物的负载率比接枝前高出2倍。     

Preparation and characterization of amphoteric cellulose–montmorillonite composite beads with a controllable porous structure

Conventional amphoteric and porous materials are often synthetic and polymer based; this tends to raise environmental concerns because of their poor biodegradability. To address this issue, novel natural-polymer- or amphoteric-modified cellulose and MOt (ACeOMt) composite beads with a typical mesoporous structure were developed in this study. These green-based porous beads, consisting of regenerated bagasse cellulose and oxalic acid modified montmorillonite (OMt), were successfully prepared by a facile coagulation method with fine calcium carbonate as a pore-forming agent. The beads with the best sphericity were obtained at a 1:1 weight ratio of cellulose to OMt. Scanning electron microscopy observation showed that ACeOMt possessed a smooth surface with abundant macropores. X-ray diffraction and thermogravimetric analysis characterizations demonstrated the success of the modification of montmorillonite and cellulose. The results of Brunauer–Emmett–Teller analysis indicate the presence of a typical mesoporous structure in the composite with a relatively high specific surface area. The resulting ACeOMt are expected to be biodegradable, nonhazardous, and applicable for various uses, including adsorption, chromatography, and soil remediation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47941.     

Diffusion and adsorption phenomena in an immobilized enzyme reactor using adsorbed polymer for attachment of the enzyme in porous alumina particles

Experiments were performed to study the effects of an immobilized enzyme on the adsorption capacity and on the diffusion in a porous solid. The enzyme invertase was immobilized by covalently binding it to a polymer matrix adsorbed in the pores of alumina. The enzyme was found to hydrolyse sucrose to glucose plus fructose with an initial activity of 60 μmol/min-g alumina. Data on the long-term stability showed a 14% decrease in initial activity in 22 days. The adsorption of glucose, fructose, or sucrose alone on porous alumina and on porous alumina containing polymer and immobilized invertase was investigated. The presence of immobilized invertase and polymer matrices decreased the adsorption capacity by about 75%. The presence of immobilized invertase on the adsorbed polymer matrices also raised the experimental tortuosity factor for diffusion in the pores from 2.0 for plain alumina to 2.75 for invertase immobilized on alumina. The decrease of particle void fraction, the enzyme blockage effect, and an increase in pore restriction effect were used to explain the increase of the tortuosity factor.