Ag/P(St-MMA)纳米复合高分子微球固定化青霉素酰化酶的研究

通过溶剂热法和无皂乳液聚合相结合,制备了P(St-MMA)高分子纳米微球.并以吸附沉积的方式在其表面沉积了Ag金属纳米粒子,最后将青霉素酰化酶共价连接在微球表面.初步研究了微球直径、银的质量分数等因素对固定化酶活力的影响.结果显示随着微球直径减小,固定化酶的偶联率和活力逐渐增加;银纳米粒子最多将固定化酶的偶联率和活力分别提高了42%和72%,固定化酶的最大表观活力(以干重记)达到了1 869 u/g,明显高于其它高分子载体固定化青霉素酰化酶的活力;实验证明银纳米粒子在青霉素水解过程中没有催化活力,但能大大提高青霉素酰化酶的催化活力.     

纤维素在固定化酶的研究进展

分析了酶及固定化酶研究进展及工业化应用瓶颈,并对无机载体、合成聚合物载体、天然聚合物载体等当前酶固定化载体材料和种类及其特点进行总结,重点介绍了纤维素作为一种无毒、可再生、可降解、生物相容性好的天然高分子材料用于固定酶载体的研究进展,阐述了纤维素在固定化酶技术工业应用亟需解决的问题及未来的发展趋势。     

以壳聚糖为载体固定化青霉素酰化酶的研究

介绍了以壳聚糖为载体固定化青霉素酰化酶需首先制备壳聚糖颗粒 ,使用戊二醛、甲醛、乙二醛 3种活化剂处理所得的壳聚糖颗粒 ,确定了以戊二醛为活化剂交联其上的氨基共价结合青霉素酰化酶的固定化方法。从戊二醛的浓度、pH值、固定化时间、固定化pH值、酶用量等条件摸索了最佳固定化条件 ,获得了酶活力为4 0 0 0 0U/ (g·h)、回收率为 5 0 %左右的固定化青霉素酰化酶。     

用于酶固定化的高分子载体材料研究进展

固定化酶是一种高效、高选择性和反应条件温和的生物催化剂。近年来,高分子材料作为酶固定化载体的研究越来越受到重视,相关的研究报道很多。对近十多年来用于固定化酶的高分子载体材料以及它们的优缺点进行了综述,并对用于酶固定化高分子载体材料的发展前景作了展望。     

青霉素酰化酶的分离纯化和固定化研究新进展

青霉素酰化酶又称为青霉素酰胺酶或青霉素氨基水解酶,主要从大肠埃希菌胞内酶和巨大芽孢杆菌胞外酶获得,该酶已大规模应用于工业生产β-内酰胺类抗生素的关键中间体和半合成β-内酰胺类抗生素。主要介绍了青霉素酰化酶固定化技术的进展,讨论了不同固定化技术的特点,并展望了固定化青霉素酰化酶的发展前景。     

小分子封闭提高固定化青霉素酰化酶的稳定性

为提高青霉素酰化酶的催化性能和热稳定性,在酶组装过程中添加小分子试剂对介孔泡沫硅载体表面过量的活化位点进行封闭。详细考察了小分子添加质量分数和种类对青霉素酰化酶负载率、催化活力及热稳定性的影响。实验结果得到:经精氨酸封闭的固定化酶活力提高至1.92倍;甘氨酸封闭的固定化酶5 h的50℃热稳定性提高至2.9倍,甘氨酸和谷氨酸封闭的固定化酶50℃热处理25 h仍保持87.9%和82.2%的残余活力;甘氨酸和谷氨酸封闭的固定化酶最适催化pH值向中性偏移且对pH值的耐受性增强。结果表明,在青霉素酰化酶共价组装过程中添加合适的小分子封闭能显著提高酶的催化性能和热稳定性。     

我自主开发成功固定化酶技术

“十五”国家科技攻关计划“纳米材料技术及应用开发”延续项目一纳米结构固定化酶组装技术的开发，日前在北京通过了中国石油和化学工业协会、中国钢协粉末冶金协会共同组织的专家验收。这一成果可望使我国摆脱依赖进口载体生产固定化青霉素酰化酶催化剂的被动局面，促进我国固定化酶技术提升和抗生素产业可持续发展。     

我自主开发成功固定化酶技术

“十五”国家科技攻关计划‘纳米材料技术及应用开发’延续项目——纳米结构固定化酶组装技术的开发．上周在北京通过了中国石油和化学工业协会、中国钢协粉末冶金协会共同组织的专家验收。这一成果可望使我国摆脱依赖进口载体生产固定化青霉素酰化酶催化剂的被动局面，促进我国固定化酶技术提升和抗生素产业可持续发展。     

青霉素酰化酶的生产与应用新进展

介绍了青霉素酰化酶的生产及应用新进展。着重介绍了青霉素酰化酶固定化技术的发展。青霉素酰化酶主要应用于6氨基青霉烷酸的工业生产和半合成的β内酰胺抗生素的合成,是在半合成抗生素的生产上有重要作用的一种酶。此外,青霉素酰化酶也可应用于其它的生物转化,如肽的合成、手性化合物的外消旋混合物的拆分。     

我国自主开发成功固定化酶技术

“十五”国家科技攻关计划“纳米材料技术及应用开发”延续项目——纳米结构固定化酶组装技术的开发，日前在北京通过了中国石油和化学工业协会、中国钢协粉末冶金协会共同组织的专家验收．这一成果可望使我国摆脱依赖进口载体生产固定化青霉素酰化酶催化剂的被动局面，促进我国固定化酶技术提升和抗生素产业可持续发展。     

Low-density polyethylene/polyamide 6 blends from multilayer films waste

Multilayer films combine properties of different polymers in a single material, attending specifications to applications such as packaging. However, the mechanical recycling for this material king is commercially less interesting because the polymeric components cannot easily be separated and the direct mechanical processing of the material leads to the immiscible and incompatible polymeric blends. The aim of this study was to evaluate properties of the blends of low-density polyethylene (LDPE) and polyamide 6 (PA6) generated from mechanical recycling of multilayer films constituted by LDPE and PA6, containing maleic anhydride grafted polyethylene (PE-g-MA) as compatibilizing agent and different amounts of virgin PA6. The LDPE/PA6 blends are immiscible for all composition and the use of PE-g-MA has showed little effect on the compatibility of the blends with high content of PA6. However, LDPE/PA6 blends with PA6 content up to 20 wt % showed considerable performance for mechanical performance that can justify the mechanical recycling of the material. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47456     

A new approach of microwave treatment to augment the mechanical properties of polymeric materials

The present study portrays a novel post-processing treatment by using microwave radiations for enhancing mechanical properties of five commonly used engineering polymers, polyamide (PA), polybutylene terephthalate (PBT), polypropylene (PP), polycarbonate (PC), and acrylonitrile-butadiene-styrene (ABS). The analysis revealed that the crystal structures of the polymers improved after the treatment due to more favorable rearrangement of crystalline segments within the polymers. Furthermore, tensile properties and tribological performance of microwave-treated polymers were found to be significantly better when compared to those of untreated counterparts. The tensile strength, elongation, and wear performance of PA increased by 51%, 286%, and 45%, respectively, only after a treatment of 20 s. A similar response was also exhibited by other polymers as well. It was noted that optimum time for microwave treatment can vary depending on different crystalline nature of the polymers. The degree of randomness in the molecular chains of semicrystalline polymers is less; thus, it requires less treatment time. However, for amorphous polymers, as randomness increases, more time is needed. As such, post-processing microwave treatment of polymers has proven beneficial as a cost-effective, time-saving, and environment-friendly technique for enhancing material properties significantly.     

笼型倍半硅氧烷基聚合物的制备和结构性能以及应用

笼型倍半硅氧烷基聚合物是一种典型的多面体有机／无机分子复合物材料,因其具有优异的光、电、热、磁、声、力学和化学相容性等性能,所以近年来被引入较为尖端的技术领域进行研究和应用。本文归纳总结了笼型倍半硅氧烷基聚合物的现行制备方法,讨论了笼型倍半硅氧烷结构对材料性能的影响。最后,对笼型倍半硅氧烷基聚合物材料的应用领域和发展趋势进行了说明。     

The effect of PTFE on the friction and wear behavior of polymers in rolling-sliding contact

The effect of PTFE on the tribological behavior of polymers in rolling sliding contact has been investigated. The two most widely used polymers — nylon 66 and polyacetal—were used as the base material. Tests were conducted over a wide range of running conditions using a twin disc rolling-sliding test rig for both the unfilled materials and for the base materials filled with 20 wt% PTFE. The experimental results showed that the friction and wear performance of the PTFE filled polymers was superior to that of the unfilled polymers. In addition the surface cracking that was found in unfilled PA66 and was thought to be responsible for premature fracture of components such as gear teeth was suppressed by the PTFE. It is suggested that a combination of high surface temperature and high surface tensile stress, produced by friction, is required to initiate these cracks and that PTFE, by reducing friction, inhibits crack formation.     

Research progress on polymer-inorganic thermoelectric nanocomposite materials

A thermoelectric (TE) material is a material where a potential difference is generated as a result of a temperature difference or the corollary of this where a temperature difference is generated when a voltage is applied. These phenomena can be used to generate electricity and/or control temperature. Traditionally, thermoelectric materials are inorganic semiconductors which have been limited in their application by low efficiency and high cost. Since the 1990s, both theoretical and experimental studies have shown that low-dimensional TE materials, such as superlattices and nanowires, can enhance the value of the TE figure of merit (ZT) which is an indicator of TE thermodynamic efficiency. To date it has not been feasible to apply these materials in large-scale energy-conversion processes because of limitations in both their heat transfer efficiency and cost. When compared to inorganic materials, organic conducting polymers possess some unique features, such as low density, low cost, low thermal conductivity, easy synthesis and versatile processability and their use in preparing polymer-inorganic TE nanocomposites appears to have great potential for producing relatively low cost and high-performance TE materials. Recently, an increasing number of studies have reported on polymeric and polymer-inorganic TE nanocomposite materials. The purpose of this paper is to review the research progress on the conducting polymers and their corresponding TE nanocomposites. Its main focus is the TE nanocomposites based on conducting polymers such as polyaniline (PANI), polythiophene (PTH), poly (3, 4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS), as well as other polymers such as polyacetylene (PA), polypyrrole (PPY), polycarbazoles (PC) and polyphenylenevinylene (PPV). Typically, polymer-inorganic TE nanocomposites are produced by physical mixing, solution mixing and in situ polymerization. The key factors that limit the use of these polymers and their polymer-inorganic TE nanocomposites as TE materials are their low ZT values. More recent developments designed to overcome the limitation including, for example, the use of carbon nanotubes and graphenes and the use of computational modelling to accelerate the selection of suitable pairs of conductive polymer and inorganic TE materials to achieve best possible nanocomposites are reviewed.     

Morphological prediction and its application to the synthesis of polyacrylate/polysiloxane core/shell latex particles

A theoretical analysis and a morphological prediction of polyacrylate (PA)/polysiloxane (PSi) latex particles with core/shell morphologies were first conducted based on interfacial tensions and relative volumes of the two polymers in the latex system. The results indicated that the normal core/shell morphology particles (PSi/PA), with hydrophobic polysiloxane as the core and with hydrophilic polyacrylate as the shell, can be easily formed. Although the inverted core/shell morphology particles (PA/PSi) with polyacrylate as the core could not be formed in most cases, even if the fraction volume of polysiloxane was larger than 0.872, which is the smallest value of forming a PA/PSi particle, the PSi/PA particles were unavoidably formed simultaneously with PA/PSi particle formation. The synthesis of PA/PSi particles containing equal amounts of polyacrylate and polysiloxane was then carried out using seeded emulsion polymerization. Before the cyclosiloxane cationic polymerization, 3‐methacryloyloxypropyl trimethoxysilane (MATS) was introduced into the polyacrylate seed latex to form an intermediate layer and chemical bonds between the core and the shell polymers. The characterization by transmission electron microscopy (TEM) demonstrated that the perfect PA/PSi core/shell particle is successfully synthesized when both the core and the shell polymers are crosslinked. The experiments showed that both the hardness and water adsorption ratio characteristics of latex films of the PA/PSi particles are in good agreement with those of the polysiloxane film. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2251–2258, 2001     

Some solid-state properties of blends of polyethylene terephthalate and polyamide-6,6

Polymer blends incorporating polyamide-6,6 (PA) and polyethylene terephthalate (PET) and having the following PA wt,% concentrations were prepared: 0, 5, 10, 25, 30, 35, and 100. Samples were obtained by molding in a reciprocating-screw injection-molding machine. The samples were annealed to minimize frozen-in stresses without increasing the crystallinity level in the material. Melting and heat-of-fnsion data, obtained with the differential scanning calorimeter, suggest an overall increased crystallinity in the blends, as indicated by a significant excess heat of fusion. Whereas the neat polymers exhibit ductile failure under both tensile and impact testing conditions, the blends show brittle behavior. Finally, the abrasion resistance of the blends is inferior to that observed for PET but higher than the resistance of PA.     

Microlayer coextrusion as a route to innovative blend structures

Nanolayer and microlayer coextrusion is a method for combining two or three polymers as hundreds or thousands of alternating layers with individual layers as thin as tens of nanometers. The possibility for utilizing microlayer coextrusion as a tool for creating microplatelets of high aspect ration was explored. Polypropylene (PP) was combined with polyamide‐66 (PA66) in microlayers. A high volume fraction of PA66 microplatelets dispersed in PP was achieved by injection molding the microlayered materials at a temperature intermediate between the melting points of the two constituents. The difference in melting temperatures provided a broad processing window of about 60°C in which the PP layers melted to form the matrix whereas the PA66 layers remained in the solid state as dispersed microplatelets of high aspect ration. The resulting material had significantly improved oxygen barrier properties. An enhancement of 4–5 times over the barrier of the conventional melt blend resulted from increased tortuosity of the diffusion pathway.     

Toughness optimization of glass‐fiber reinforced PA 6/PA 66‐based composites: Effect of matrix composition and colorants

Mixing of polyamide 6 (PA 6) and polyamide 66 (PA 66) is integrated in the trend of development of new and improved materials by combination of different polymers and some reinforcing materials to polymer composites. The specific polymer composite PA 6/PA 66 reinforced with short glass‐fibers combines the good coloring of PA 6, and the small moisture absorption of PA 66. Technical applications of PA 6/PA 66 composites are mainly used in the automotive industry. Specific requirements of this industry lead to the necessity to optimize the material resistance against crack propagation of the PA 6/PA 66 composites, using mechanical and fracture mechanical methods. So, the present investigations focus on fracture mechanics toughness optimization of the PA 6/PA 66 composites, including unstable and stable crack growth. The aim of this toughness optimization is to find out the optimal mixing ratio of PA 6/PA 66. Applications of PA 6/PA 66 in the automotive industry and specific client wishes are the main reasons for black‐coloring of the PA materials. The influence of several black‐colorants (carbon black, nigrosine, spinel, iron oxide) on mechanical and fracture mechanical properties of the PA composites is also investigated using fracture mechanical methods. As experimental fracture mechanical method, preferentially, the instrumented Charpy impact test (ICIT) and the new cut method to determine the stable crack growth of glass‐fiber reinforced materials was used. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Physical Properties of Polyblends of Polyamide 6 Polymer with Cationic Dyeable Polyamide 6 Polymer

Polyamide 6 (PA 6) and cationic dyeable polyamide 6 (CD-PA 6) polymers were blended mechanically in the proportions of 75/25, 50/50, 25/75 in a melt twin-screw extruder to prepare three PA 6/CD-PA 6 polyblended polymers. The molar ratio of dimethyl 5-sulfoisophthalate sodium salt (SIPM) for CD-PA 6 polymer was 2%. This study investigated the physical properties of PA 6/CD-PA 6 polyblended materials using gel permeation chromatograph (GPC), nuclear magnetic resonance (NMR), gas chromatography (GC), potentiometer, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), the density gradient method, a rheometer, and extension stress–strain measurement. Experimental results of the DSC indicated PA 6 and CD-PA 6 molecules easily formed miscible domains. The surface of PA 6/CD-PA 6 polyblend exhibited a uniform morphology from the scanning electron microscope (SEM). The SEM observations of morphologies were consistent with the DSC results for PA 6/CD-PA 6 polyblends. PA 6 and CD-PA 6 polymers were proven to be a compatible system. Flow behavior of PA 6/CD-PA 6 polyblends exhibited positive-deviation blends (PDB) and the 50/50 blend of PA 6/CD-PA 6 showed a maximum value of the melt viscosity. The crystallinities of PA 6/CD-PA 6 polyblends declined as a SIPM content increased. Moreover, the crystallinity of DSC method was slightly less than that of the density gradient method. The weight loss percentages of the PA 6/CD-PA 6 polyblends increased as the SIPM content increased in aqueous NaOH solution.