酶催化生物可降解聚酯的合成与研究进展

生物可降解聚酯是一种新型高分子聚合材料,可通过发酵、化学方法和酶催化来合成.本文综述了酶催化下通过缩聚、酯交换、内酯开环聚合等方法合成此类聚酯.酶催化合成生物可降解聚酯是一种新型的技术,可以在温和条件下高效合成,有着传统方法难以比拟的优势.     

脂肪酶催化开环聚合的研究进展

酶是一种绿色、安全、高效、专一的生物催化剂,在反应中具有能耗小、可循环利用和选择性高等优点,更重要的是酶催化聚合能够制备传统的化学催化无法(或难以)实现的聚合物,具有一定的工业化前景。本文简述了酶催化的发展历程、机理以及其制备特殊结构和功能聚合物材料的特点,特别是脂肪酶催化下的开环聚合相对于缩聚反应来说,具有反应条件温和、分子量和结构可控性好等优势,因此重点描述脂肪酶催化开环聚合在合成不同拓扑结构(线型、支化、交联)聚合物中的研究进展。     

化学-酶多步串联反应及其在高附加值手性化合物高效、绿色合成中的应用

与化学催化或酶催化合成相比,化学-酶相结合的多步串联反应是一种更简单、高效、经济的方法,兼具酶催化剂的高效、高选择性等优点,且合成原料价廉易得,合成工艺简捷高效,生产环境绿色友好,所得产品光学纯度高,使其在高附加值手性化合物的开发和合成方面得到了广泛的应用.近年来,化学家们通过改变催化剂和设计更为合理的反应方式,致力于将化学-酶催化反应条件变得更为容易,从而将其应用于更多反应领域.综述了近年来国内外化学-酶多步串联反应,如酶与金属催化、酶与有机催化、酶与新型反应技术等相结合多步串联合成手性醇类、环氧类、杂环类以及其他手性化合物的研究进展,并对该领域的发展趋势进行了展望.     

有机小分子催化环醚与环状酸酐共聚研究进展

有机小分子催化聚合反应是合成化学领域新的研究方向。有机催化环醚(主要为环氧化物)与环状酸酐共聚制备聚酯的合成路线,由于单体具有来源广泛、有机催化剂低毒、对水和空气不敏感等特点,因而应用前景广阔。本文按有机小分子催化剂、环醚与环状酸酐的种类综述了近年来出现的有机催化共聚合成聚酯的反应,并详细讨论了该共聚反应及其机理,尤其是高催化活性和聚合可控性的Lewis酸碱对催化共聚的机理;提出了利用Lewis酸为增长链阴离子提供结构因素(如基团和电子结构效应)来调控聚合的方法。今后,催化环氧化物与环状酸酐共聚研究的中心任务仍然是发展新的高活性有机催化剂,并实现"活性"的全交替共聚反应,进一步提高共聚物的分子量,并实现共聚反应的化学选择性、区域和立体选择性的精确控制。     

酶促水凝胶的合成及生物传感应用研究进展

近年来,聚合物基水凝胶材料已经成为一种独特的修饰材料,为新型生物传感器的设计提供了新思路.酶具有特异性高、毒性低、催化效率高等良好特性,已被用于催化聚合各种新型水凝胶.本文综述了几种酶促水凝胶的合成方法及其在细胞代谢物、组织工程、伤口愈合和癌症监测等方面的潜在应用,并对基于酶促水凝胶反应的生物传感器的制备与应用进行了总结与展望.     

光酶级联一锅法合成手性脂肪胺

对映体脂肪胺在有机合成与化工领域具有广泛的应用, 但其主要依赖于金属催化获得. 我们设计了一种光催化与酶催化级联催化的合成方法, 由脂肪醇出发合成手性脂肪胺. 通过筛选, 发现9-芴酮在可见光激发下可高效催化脂肪醇氧化为脂肪酮, 后者作为反应中间体被转氨酶在胺供体存在下经转氨反应合成手性胺. 在一锅法条件下, 该级联方法转化率可达99%, 目标产物的光学纯度>99%. 此外, 该光催化体系可分别与手性互补的转氨酶级联, 进而获得手性反转的脂肪胺产物. 该光酶级联催化方法充分结合了光催化的高效率与酶催化的立体选择性优势, 为手性脂肪胺类分子的合成提供了一种新型合成方法.     

生物可降解性聚羟基脂肪酸酯的化学合成研究进展

聚羟基脂肪酸酯是一种新型合成的脂肪族聚酯,同聚乳酸相似,具有优异的生物相容性能、生物可降解性和优良的力学机械性能,可作为生物医用材料和生物可降解包装材料,是最具前景的环境友好型聚合材料之一。目前合成聚乳酸和聚羟基脂肪酸酯的化学方法主要有开环聚合法、直接缩聚法以及自身酯交换聚合法,不过后者研究得较少。本文对这3种方法的研究进展进行了叙述,重点讨论了开环聚合法和直接缩聚法,尤其对开环聚合中的配位插入聚合的新进展进行了较详细的论述。     

β-氨基酸合成研究进展

综述了合成β-氨基酸的五种主要方法,包括化学拆分、手性色谱柱拆分、Arndt-Eistert反应、不对称合成和酶催化合成的最新研究进展,特别是近年来发展迅速的不对称合成和酶催化合成。参考文献90篇。     

多组分聚合体系的探索

多组分反应是利用三种或者三种以上反应物一锅法得到终产物的反应。在此过程中,无需对中间产物进行分离提纯,而且几乎所有反应物的原子都出现在生成物当中。因此多组分反应经常被用来合成具有复杂结构的化合物。我们在多组分反应中引入可聚合元素,将功能化单体合成和可控聚合结合在一起,一步合成具有特殊官能结构的聚合物。这个体系中的反应均互不干扰,有着良好的匹配效果。因此,得到的产物具有可控的分子量和很窄的分子量分布。与传统方法相比,这种多组分聚合体系节省了反应时间、降低了合成成本、合成途径更加绿色经济。我们现已发展了多种多组分聚合体系,按照复杂程度不同分为二元、三元和四元体系。通过不同的有机小分子反应与可控聚合的结合,我们成功制备了一些通过其他聚合方法难以或是无法合成的新型聚合物,体现了这一聚合方法的特点和优势。随着对多组分聚合体系认识的不断深入,相信我们能够更简便地合成更多结构新颖的聚合物。     

脂肪酶催化缩聚法合成可完全降解的聚羟基丙酸酯(英文)

以3-羟基丙酸甲酯为聚合单体,建立了以固定化脂肪酶Novozym 435为催化剂的酶催化缩聚反应体系,合成可完全降解的高分子聚酯聚羟基丙酸酯,考察了反应条件和介质对反应性能的影响,结果表明,纯度大于95%的单体即可在温和条件下合成聚羟基羧酸酯;降低反应压力可有效提升产物产率和分子量.通过选择合适的有机溶剂介质和表面活性剂,可使产物分子量提升至13000(Mw)以上.脂肪酶催化剂重复利用能力优异,经6批次反应后,其相对活性保持在95%以上.     

Polycondensation of Sebacic Acid with Primary and Secondary Hydroxyl Groups Containing Diols Catalyzed by Candida antarctica Lipase B

Abstract

The aliphatic polyesters are normally synthesized by ester interchange reactions or direct esterification of hydroxyacids or diacid/diol combinations. Biotransformation, utilizing the enzymes as catalysts, was accepted as an alternative route for the synthesis of aliphatic polyesters and offers various advantages compared with the conventional, metal-catalyzed polymerization reactions. Previous studies indicated that lipase-catalyzed polycondensation reactions between diols and diacids occurred preferentially at primary hydroxyl groups of diols, when diols contained both primary and secondary hydroxyl groups. In this work, we investigated lipase-catalyzed polycondensation of diacids and secondary hydroxyl group–containing diols, and successfully synthesized polyesters by polycondensation with secondary hydroxyl groups as well as primary hydroxyl groups. Various diols, glycerol, 1,2-propanediol, 1,3-butanediol, 2,3-butanediol, and 2,4-pentanediol were tested for the polycondensation. The polymerization was achieved by heating a mixture of lipase B, sebacic acid, and the diols in anhydrous toluene at 100 °C for 72 h. The resulting polymers were characterized by ¹H and ¹³C NMR spectroscopy, Fourier transform–infrared spectroscopy, thermogravimetric analysis, and gel permeation chromatography.     

Enzyme‐Catalyzed Synthesis and Chemical Recycling of Polyesters

This article summarizes the enzyme‐catalyzed synthesis and chemical recycling of biodegradable aliphatic polyesters and poly(carbonate ester)s directed towards establishing green polymer chemistry. Lipase catalyzes the condensation polymerization of a hydroxy acid, diacid with diol, diacid anhydride with oxirane, and polyanhydride with diol, or the ring‐opening polymerization of lactones of small to large rings, and a cyclic diester to produce the corresponding polyesters. Also, lipase catalyzes the condensation polymerization of a dialkyl carbonate with diol, and the ring‐opening polymerization of a cyclic carbonate to produce the corresponding polycarbonates. These polyesters and polycarbonates were selectively degraded by lipase to produce repolymerizable oligomers. These chemical recycling systems using an enzyme will establish a novel methodology for sustainable polymer recycling. Finally, current trends in green polymer production using enzymes are discussed.     

Synthesis of High Molecular Weight Polyesters via In Vacuo Dehydrogenation Polymerization of Diols

The Milstein catalyst has proven to be highly effective for the conversion of alcohols to esters, as well as alcohols and amines to amides and polyamides. We have recently found that the catalyst's range can be extended to very efficient in vacuo dehydrogenation polymerization of α,ω‐diols to generate polyesters. The gaseous hydrogen byproduct that is produced is easily removed to drive the equilibrium toward product, which leads to the formation of high molecular weight polymer ( up to 145 000 g mol⁻¹). This optimized methodology works well to polymerize diols with a spacer of six carbons or more. Diols with fewer carbons are cyclized to lactone; the dividing point is the dehydrogenation of 1,5‐pentanediol, which leads to a mixture of polyester and lactone. Reported herein is the synthesis and characterization of five aliphatic polyesters prepared via this novel dehydrogenation polymerization approach.     

Terephthalic Acid Copolyesters Containing Tetramethylcyclobutanediol for High-Performance Plastics

There is a need for high-performance applications for terephthalic acid (TPA) polyesters with high heat resistance, impact toughness, and optical clarity. Bisphenol A (BPA) based polycarbonates and polyarylates have such properties, but BPA is an endocrine disruptor. Therefore, new TPA polyesters that are less hazardous to health and the environment are becoming popular. Tetramethylcyclobutanediol (TMCD) is a difunctional monomer that can be polymerized with TPA and other diols to yield copolyesters with superior properties to conventional TPA polyesters. It has a cyclobutyl ring that makes it more rigid than cyclohexanedimethanol (CHDM) and EG. Thus, TMCD containing TPA copolyesters can have high heat resistance and impact strength. TPA can be made from abundantly available upcycled polyethylene terephthalate (PET). Therefore, this review discusses the synthesis of monomers and copolyesters, the impact of diol composition on material properties, molecular weight, effects of photodegradation, health safety, and substitution of cyclobutane diols for future polyesters.     

Synthesis and characterization of polyesters derived from sebacic acid,hexanediol, and hydroquinone

Oils and fats derived from animals and plants provide a good renewable source for polymer precursors. In this investigation, fatty acids derived from plant oils and diols were used as monomers to produce polyesters by melt polycondensation. Sebacic acid, hexanediol, and hydroquinone were used as precursors in the polymer synthesis. The polymers were characterized by gel permeation chromatography, Fourier transform infrared spectroscopy, three-bending point flexural test, X-ray diffraction, tensile testing, and contact angle. The resulting polyesters were blended with epoxies to create materials with an increased elongation at break without affecting other mechanical properties.     

Enzymatic polymerization: A new method of polymer synthesis

Enzymatic polymerization denotes an in vitro polymerization via nonbiosynthetic pathways catalyzed by an isolated enzyme. This article describes the recent progress of this polymerization technique, developed mainly during this decade. The polymerization utilizes enzymes of hydrolases and oxidoreductases as catalysts. This new method of polymer synthesis provided natural polysaccharides like cellulose, amylose, xylan, and chitin, and unnatural polysaccharides catalyzed by a glycosidase from well-designed monomers, various functionalized polyesters catalyzed by lipase from a variety of monomers, and polyaromatics materials catalyzed by an oxidoreductase and an enzyme model complex from phenols and anilines. An oxidoreductase also initiated vinyl polymerizations. Characteristic features of enzymatic polymerizations are discussed, including the importance of the combination of substrate monomer and enzyme. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3041–3056, 1999     

Iterative tandem catalysis of secondary diols and diesters to chiral polyesters

The well-known dynamic kinetic resolution of secondary alcohols and esters was extended to secondary diols and diesters to afford chiral polyesters. This process is an example of iterative tandem catalysis (ITC), a polymerization method where the concurrent action of two fundamentally different catalysts is required to achieve chain growth. In order to procure chiral polyesters of high enantiomeric excess value (ee) and good molecular weight, the catalysts employed need to be complementary and compatible during the polymerization reaction. We here show that Shvo's catalyst and Novozym 435 fulfil these requirements. The optimal polymerization conditions of 1,1'-(1,3-phenylene) diethanol (1,3-diol) and diisopropyl adipate required 2 mol% Shvo's catalyst and 12 mg Novozym 435 per mmol alcohol group in the presence of 0.5 M 2,4-dimethyl-3-pentanol as the hydrogen donor. With these conditions, chiral polyesters were obtained with peak molecular weights up to 15 kDa, an ee value up to 99% and with 1-3 % ketone end groups. Also with the structural isomer, 1,4-diol, a chiral polyester was obtained, albeit with lower molecular weight (8.3 kDa) and slightly lower ee (94%). Aliphatic secondary diols also resulted in enantio-enriched polymers but at most an ee of 46 % was obtained with molecular weights in the range of 3.3-3.7 kDa. This low ee originates from the intrinsic low enantioselectivity of Novozym 435 for this type of secondary aliphatic diols. The results presented here show that ITC can be applied to procure chiral polyesters with good molecular weight and high ee from optically inactive AA-BB type monomers.     

Copper-Catalyzed Si-H Bond Insertion Polymerization for Synthesis of Optically Active Polyesters Containing Silicon

The synthesis and characterization of chiral polymers with diverse structure remain a long-term challenging research topic.Herein,a copper-catalyzed enantioselective insertion of carbene into Si-H bond was applied to polycondensation,giving a new type of optically active degradable polyesters containing Si-C bond in the main chain.The polymerization features mild condition,broad substrate scope,excellent yields and enantioselectivities.Chiral diols could be obtained via reduction of optically active polyesters.Thermogravimetric analysis indicated these chiral polyesters exhibit good thermal stability.     

Biocatalytic synthesis of polymers. II. Preparation of [AA–BB]x polyesters by porcine pancreatic lipase catalyzed transesterification in anhydrous,low polarity organic solvents

Enzyme-catalyzed preparation of polymers offers several potentially valuable advantages over the usual polymerization procedures. (1) Such polymerizations may allow the polymer to retain functionality that would be destroyed under normal polymerization conditions. (2) The selectivity provided by enzyme catalysts may permit polymers, including optically active polymers, to be prepared that are either not accessible or accessible only with difficulty by other methods. (3) The characteristics of the enzyme and the mild polymerization conditions may permit formation of polymers having highly regular sizes and backbone structures. This report describes the first successful use of an enzyme-catalyzed polycondensation to prepare a chiral (AA–BB)_x polyesters of more than a few repeat units. Polymerization of bis(2,2,2-trichloroethyl) alkanedioates (BB) with diols (AA) using the enzyme porcine pancreatic lipase (PPL) as a catalyst is detailed. The polycondensations were carried out at ambient temperature in anhydrous, low polarity organic solvents such as ether, THF, and methylene chloride. End group analysis by NMR provided M_n values of 1300–8200 daltons while GPC provided M_w values of 2800–14900 daltons for the polymers. Based on proton NMR spectra obtained during the polymerization, relatively rapid formation of an AA–BB “dimer” and an AA–BB–AA “trimer,” slower formation of a BB–AA–BB “trimer,” and subsequent condensation of these to give higher polymers are suggested to be components of the polymerization mechanism.