Functional cyclodextrins. 1. Chloroacetylated cyclodextrins

The paper discusses the synthesis of the chloroacetylated derivatives of α-, β- and γ-cyclodextrins. These novel functionalized products can be used both in the synthesis of some conjugates with bioactive substances by covalent bonding and/or for inclusion of hydrophobic compounds.     

Supercritical antisolvent micronization of cyclodextrins

Micronization of α- and β-cyclodextrins solubilized in dimethylsulfoxide (DMSO) has been successfully performed using the Supercritical AntiSolvent (SAS) precipitation. We obtained sub-microparticles, microparticles and expanded microparticles of both cyclodextrins, ranging from about 0.1 to 11 μm, varying the concentration of the liquid solution from 5 to 200 mg/mL, process temperature (40-60 °C) and pressure (90-180 bar). Particularly, we observed for both materials that, increasing the concentration of the liquid solution, decreasing the pressure or increasing the temperature, the mean particle size increased and the particle size distribution enlarged.We also tried to relate the morphologies obtained to the position of the process operating point with respect to the mixture critical point (MCP) of the ternary system cyclodextrin-DMSO-CO₂.     

Macromolecular recognition by cyclodextrins. Interaction of cyclodextrins with polymethacrylamides bearing hydrophobic amino acid residues

The interaction of cyclodextrins (CDs) with poly(N-methacryloyltryptophan) (pMTrp) and with poly(N-methacryloylphenylalanine) (pMPhe) was investigated as a simple model system of macromolecular recognition of proteins. The association constants (K) for the model compounds, sodium salts of tryptophan and phenylalanine, are not so different (i.e. 43 and 16 M⁻¹ for α-CD, 59 and 69 M⁻¹ for β-CD, and 12 and 3 M⁻¹ for γ-CD, respectively). On the other hand, there is a significant difference in the apparent K values for pMTrp and pMPhe (i.e. the K values for pMPhe are considerably smaller than ca. 10 M⁻¹, whereas those for pMTrp are 30, 83, and 11 M⁻¹ for α-, β-, and γ-CDs, respectively). These observations indicate that a subtle difference in polymer side chains can be critical in macromolecular recognition.     

封端型聚醚改性聚硅氧烷非离子表面活性剂的合成

以低含氢硅油、α-烯丙基聚醚等为原料,经烷基封端、硅氢加成等反应制备了封端型聚醚改性聚硅氧烷非离子表面活性剂,讨论了温度、催化剂以及聚醚结构等对封端率的影响。结果表明,采用以氢氧化钠和碳酸钠制备的缓释性复合碱为催化剂的一步法封端工艺,在反应温度25~65℃条件下,α-烯丙基聚醚的烷基封端率可达85%以上。封端型聚醚改性有机硅表面活性剂可用于单组分聚氨酯密封胶、高回弹和软质聚氨酯泡沫的泡沫稳定剂。     

Nanostructuring and functionalizing polymers with cyclodextrins

We summarize our recent studies employing the cyclic starches called cyclodextrins (CDs) to both nanostructure and functionalize polymers. Two important structural characteristics of CDs are taken as advantages to achieve these goals. First the ability of CDs to form non-covalent inclusion complexes (ICs) with a variety of guest molecules, including many polymers, by threading and inclusion into their relatively hydrophobic interior cavities, which are roughly cylindrical with diameters of ∼0.5 to 1.0 nm for α-, β-, and γ-CD containing 6, 7, and 8 α-1,4-linked glucose units, respectively. When guest polymers are coalesced from the CD-ICs by removing their host CDs, they are observed to solidify with structures, morphologies, and even conformations that are distinct from bulk samples made from their solutions and melts. Molecularly mixed, intimate blends of two or more polymers that are normally immiscible can be obtained from their common CD-ICs, and the phase segregation of incompatible blocks can be controlled (suppressed or increased) in CD-IC coalesced block copolymers. In addition, additives may be more effectively delivered to polymers in the form of their soluble or crystalline CD-ICs or rotaxanes. Secondly, many -OH groups attached to the exterior rims of CDs, in addition to conferring water solubility, provide an opportunity to covalently bond them to polymers either during their syntheses or via post-polymerization reactions. Polymers containing CDs in their backbones or attached to their side chains are observed to more readily accept and retain additives, such as dyes, fragrances, etc. They may also be further reacted or treated through their CDs to cross-link and form networks or to form blends with other polymers having a propensity to thread through their attached CD cavities.     

不饱和聚醚醋酸酐酯化封端合成工艺的探讨

简单介绍了目前不饱和伯羟基聚醚封端的几种常用方法,讨论了最具可操性的工艺方案,即利用醋酸酐酯化封端工艺各因素对封端结果影响的问题,通过系列正交实验数据,得出最佳封端剂用量、反应温度及时间等工艺条件。     

Macromolecular recognition by cyclodextrins. Interaction of cyclodextrins with poly(N-acryloyl-amino acids)

The interactions of cyclodextrins (CDs) with poly(N-acryloyl-amino acids) (pAXaa) were investigated by ¹H NMR and two dimensional nuclear Overhauser effect spectroscopy (2D NOESY) to elucidate the effect of attachment of amino acid residues to the polymer chain. Using the ¹H NMR data measured at varying pAXaa concentrations, apparent association constants (K) were roughly estimated for the CDs/pAXaa systems. These apparent K values indicated that α-CD interacted with poly(N-acryloylphenylalanine) and with poly(N-acryloyltyrosine) and β-CD and γ-CD interacted with poly(N-acryloyltryptophan). Comparison of these apparent K values with those for the model compounds, i.e., amino acid sodium salts, revealed that the effect of attachment of amino acid residues to the polymer chain was stronger for a smaller amino acid residue.     

Thermodynamics of the encapsulation by cyclodextrins

Molecular encapsulation on a molecular basis can be performed by cyclodextrins. The inclusion of organic molecules into the interior changes the properties of these molecules, which may be used for a broad variety of applications. The affinity of guest molecules for the cavities of various cyclodextrins depends on the stereochemistry and on the interaction forces of the molecules involved. Calculations of the thermodynamic parameters show that the reaction entropy is highly important for the inclusion reaction. Completely different reaction mechanisms are observed for various types of cyclodextrins as some of these reactions show enthalpy–entropy compensation. Others are supported by the reaction entropy or are even entropically controlled. Protonation and deprotonation reactions contribute significantly to the inclusion reaction, as first of all the solubility of the compounds in water is strongly influenced by the acidity of the solution, and, moreover, all tautomeric forms of the compounds show different affinities to various cyclodextrins. Copyright © 2006 Society of Chemical Industry     

直接从水玻璃合成表面修饰的纳米SiO2微粒

采用溶胶-凝胶法,以水玻璃为原料,在加入复合表面活性剂和分散剂的条件下,与乙酸反应直接得到纳米表面修饰的SiO2微粒。TEM照片显示,纳米SiO2颗粒为球形,粒度为10～30nm,统计平均粒径为20nm。合成工艺研究表明,纳米SiO2粒度大小和分散度大小可由表面活性剂浓度、反应物浓度、分散剂浓度和反应温度等控制,其中表面活性剂浓度、反应物浓度、分散剂浓度、反应温度的最佳值分别为：0．6mmol／L,0．6mol／L,7mmol／L,55℃。     

两亲性环糊精的合成研究进展

与天然环糊精相比,两亲性环糊精不仅包结客体分子,而且自组装形成囊状结构,是一类重要的药物载体.本文综述了两亲性环糊精的合成,并对其发展前景进行了展望.     

环糊精在化妆品领域中的应用研究

简要介绍了环糊精、人体皮肤结构及化妆品透皮吸收过程,重点阐述了环糊精包合作用对化妆品祛痘能力、美白能力、抗衰老能力、抗敏能力、抑菌效果及消除不良气味等性能的改善,展望了环糊精在中国化妆品行业的前景。     

Analysis of cyclodextrins using a calorimetric biosensor

A thermostable α-amylase catalyzed the exothermal hydrolysis of cyclodextrins. It was immobilized covalently via a spacer on controlled pore glass (CPG-10) or Silicagel. The temperature signal caused by the reaction heat of the cyclodextrin hydrolysis was determined in a one column calorimetric system (enzyme thermistor). It was correlated to the cyclodextrin concentration and depended on the type of enzyme carrier and kind of cyclodextrin hydrolyzed. The proposed technique offers a direct route to the determination of α-amylase activity, and the results are of importance for analysis of cyclodextrin concentration.     

环糊精催化有机反应的进展

环糊精通过主客体相互作用能将疏水性有机分子转移到对环境友好的水中进行有机反应,还能影响分子的电性环境,使反应在温和的条件下就能获得良好的收率,几乎没有副产物,在有机合成中应用十分广泛。本文就近年来环糊精在有机合成中的催化应用分为氧化、加成、开环、水解、偶联和取代等几种反应类型,并对这些反应进行了概述。     

改性端氨基硅油制备洗去型护发素的研究

双端氨丙基硅油与2,3-环氧丙基三甲基氯化铵(GTA)在乳液体系中反应并乳化,制得季铵盐改性双端氨丙基硅油乳液,用于护发素组合物,并护理发束后进行感官评价、头发梳理性测试,同时用原子吸收光谱测定经多次洗发与护发后发束上残留的硅油类物质。结果表明,季铵盐改性双端氨丙基硅油用于护发素能获得较好的效果,发束经洗发后硅油类物质在头发上积累量非常少,季铵盐改性双端氨丙基聚硅氧烷乳液是良好的洗去型发用调理剂。     

Ring-opening polymerization of cyclic esters by cyclodextrins

Synthetic polymers, typically prepared by addition polymerization or stepwise polymerization, are used constantly in our daily lives. In recent years, polymer scientists have focused on more environmentally friendly synthetic methods such as mild reaction conditions and biodegradable condensation polymers, including polyesters and polyamides. However, challenges remain in finding greener methods for the synthesis of polymers. Although reactions carried out in water are more environmentally friendly than those in organic solvents, aqueous media can lead to the hydrolysis of condensation polymers. Furthermore, bulk polymerizations are difficult to control. In biological systems, enzymes synthesize most polymers (proteins, DNAs, RNAs, and polysaccharides) in aqueous environments or in condensed phases (membranes). Most enzymes, such as DNA polymerases, RNA polymerases, and ribosomes, form doughnutlike shapes, which encircle the growing polymer chain. As biopolymers form, the active sites and the substrate-combining sites are located at the end of the growing polymer chain and carefully control the polymerization. Therefore, a synthetic catalyst that could insert the monomers between the active site and binding site would create an ideal biomimetic polymerization system. In this Account, we describe cyclodextrins (CDs) as catalysts that can polymerize cyclic esters (lactones and lactides). CDs can initiate polymerizations of cyclic esters in bulk without solvents (even water) to give products in high yields. During our studies on the polymerization of lactones by CDs in bulk, we found that CDs function not only as initiators (catalysts) but also as supporting architectures similar to chaperone proteins. CDs encircle a linear polymer chain so that the chain assumes the proper conformation and avoids coagulation. The CDs can mimic the strategy that living systems use to prepare polymers. Thus, we can obtain polyesters tethered to CDs without employing additional solvents or cocatalysts. Although CD has many hydroxyl groups, only one secondary hydroxyl group attaches to the polyester chain. In addition, the polymerization is highly specific for monomer substrates. We believe that this is the first system in which the catalyst includes monomers initially and subsequently activates the included monomers. The catalyst then inserts the monomers between the binding site and the growing chain. Therefore, this system should provide a new environmentally friendly route to produce biodegradable functional polymers.     

Nanophotothermolysis of Poly-(vinyl) Alcohol Capped Silver Particles

Laser-induced thermal fusion and fragmentation of poly-(vinyl) alcohol (PVA)-capped silver nanoparticles in aqueous medium have been reported. PVA-capped silver nanoparticles with an average size of 15 nm were prepared by chemical reduction technique. The laser-induced photo-fragmentation of these particles has been monitored by UV-visible spectroscopy and transmission electron microscopy. The morphological changes induced by thermal and photochemical effects were found to influence the optical properties of these nanoparticles.     

醚化封端聚醚的研究进展及应用

重点论述了醚化封端聚醚的主要合成方法、醚化封端聚醚的分子结构对产品特性的影响,以及近年来醚化封端聚醚的技术进展。并通过实例介绍了醚化封端聚醚在清洗、纺织印染、食品加工及在合成聚醚改性有机硅等领域的应用。     

Electronic Structures of S-Doped Capped C-SWNT from First Principles Study

The semiconducting single-walled carbon nanotube (C-SWNT) has been synthesized by S-doping, and they have extensive potential application in electronic devices. We investigated the electronic structures of S-doped capped (5, 5) C-SWNT with different doping position using first principles calculations. It is found that the electronic structures influence strongly on the workfunction without and with external electric field. It is considered that the extended wave functions at the sidewall of the tube favor for the emission properties. With the S-doping into the C-SWNT, the HOMO and LUMO charges distribution is mainly more localized at the sidewall of the tube and the presence of the unsaturated dangling bond, which are believed to enhance workfunction. When external electric field is applied, the coupled states with mixture of localized and extended states are presented at the cap, which provide the lower workfunction. In addition, the wave functions close to the cap have flowed to the cap as coupled states and to the sidewall of the tube mainly as extended states, which results in the larger workfunction. It is concluded that the S-doped C-SWNT is not incentive to be applied in field emitter fabrication. The results are also helpful to understand and interpret the application in other electronic devices.     

Novel Semi-Interpenetrating Polyimide Network Based on Acryl End Capped Oligoimides

Amino terminated oligoimides (AOIs) were prepared by the Michael addition reaction of various bismaleimides(1a–c) with excess of 4,4′-diamino diphenyl methane (DDM). These AOIs were characterized by elemental analysis, FT-IR spectral studies and number average molecular weight estimated by non-aqueous conductometric titrations. AOIs were then reacted with acrylol chloride and resultant acryl end capped oligoimides (AcOIs) sample were also characterized thermogravimetrically. Each of these AcOI was then combined with the commercially available thermoplastic polyamic acid solution in various proportions. The resultant suspensions were then heated in the presence of azobisisobutyronitrile (AIBN) as a initiator. The AcOI polymerized through double bond and polyamic acid is cyclized to form SEMI-IPN polymides, which were analyzed thermogravimetrically. The glass fibre reinforced composites were fabricated by using the suspensions of the AcOI and polyamic acid solution. The composites of SEMI IPN polymides were analyzed for their mechanical, chemical and electrical properties.