Renewability is not Enough: Recent Advances in the Sustainable Synthesis of Biomass‐Derived Monomers and Polymers

Taking advantage of the structural diversity of different biomass resources, recent efforts were directed towards the synthesis of renewable monomers and polymers, either for the substitution of petroleum‐based resources or for the design of novel polymers. Not only the use of biomass, but also the development of sustainable chemical approaches is a crucial aspect for the production of sustainable materials. This review discusses the recent examples of chemical modifications and polymerizations of abundant biomass resources with a clear focus on the sustainability of the described processes. Topics such as synthetic methodology, catalysis, and development of new solvent systems or greener alternative reagents are addressed. The chemistry of vegetable oil derivatives, terpenes, lignin, carbohydrates, and sugar‐based platform chemicals was selected to highlight the trends in the active field of a sustainable use of renewable resources.     

基于天然萜类的可持续性聚合物

随着可持续发展观念的逐步深入,可持续性聚合物已发展成为当今高分子领域的研究热点之一.萜类化合物作为自然界中一类来源广泛的天然资源,具有多种可修饰位点和丰富的功能性,由它出发制备可持续性聚合物,不仅可以简化聚合物的合成步骤,还可以赋予聚合物独特的立体构型、良好的生物活性和生物相容性等特点,进而拓展其在表面涂层、生物医药、组织工程等领域中的应用.本文综述了近年来国内外基于天然萜类可持续性聚合物的研究进展,从萜类化合物的结构特点出发,系统介绍了基于天然萜类可持续性聚合物的合成策略、特性及应用.     

Plant oil renewable resources as green alternatives in polymer science

The utilization of plant oil renewable resources as raw materials for monomers and polymers is discussed and reviewed. In an age of increasing oil prices, global warming and other environmental problems (e.g. waste) the change from fossil feedstock to renewable resources can considerably contribute to a sustainable development in the future. Especially plant derived fats and oils bear a large potential for the substitution of currently used petrochemicals, since monomers, fine chemicals and polymers can be derived from these resources in a straightforward fashion. The synthesis of monomers as well as polymers from plant fats and oils has already found some industrial application and recent developments in this field offer promising new opportunities, as is shown within this contribution. (138 references.)     

Combining renewable gum rosin and lignin: Towards hydrophobic polymer composites by controlled polymerization

Rosin polymer–grafted lignin composites were prepared via “grafting from” atom transfer radical polymerization (ATRP) with the aid of 2‐bromoisobutyryl ester‐modified lignin as macroinitiators. Three different monomers derived from dehydroabietic acid (DA) were used for execution of grafting from ATRP, while DA was separately attached onto lignin by a simple esterification reaction. Kinetic studies indicated controlled and “living” characteristics of all monomer polymerizations. Thermal studies indicated that rosin polymer–grafted lignin composites exhibited glass transition temperatures in a broad temperature range from ～20 to 100°C. The grafting of both DA and rosin polymers significantly enhanced hydrophobicity of lignin. Static contact angle measurement of water droplets showed ～90° for all these rosin modified lignin composites. X‐ray photoelectron spectroscopy demonstrated that the surface of rosin–lignin composites was dominated with chemical compositions originating from the hydrocarbon rich rosin moiety. The impartation of hydrophobicity of rosin into lignin provided excellent water resistance of this class of renewable polymers, as all rosin‐modified lignin composites showed water uptake below 1.0 wt %. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

How well can renewable resources mimic commodity monomers and polymers?

This highlight discusses the recent progress aimed at maximizing the potential of biomass for commodity monomers and polymers. These efforts are no longer solely academic issues. In recent years, a variety of alkene, diene, aromatic, and condensation type monomers have utilized renewable resources, such as cellulose, lignin, plant oils, starches, and monoterpenes in commercial polymers. Generally, these multifaceted efforts involve pretreatment of biomass with thermal, chemical, or physical methods followed by a catalyst sequence that entails a combination of acid‐catalysis, bio‐catalysis, or metal‐based catalysis. In this regard, synthesis strategies for ethylene, propylene, α‐olefins, methylmethacrylate, 1,3‐butadiene, 1,3‐cyclohexadiene, isoprene, 1,3‐propanediol, 1,4‐butanediol, and terephthalic acid are discussed as well as opportunities for other renewable‐based monomers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

生物基环氧树脂及固化剂研究现状

生物基高分子材料以可再生资源为主要原料,它在减少塑料行业对石油资源消耗的同时,也减少了石油化工原料在生产过程中对环境的污染,具有节约石油资源和保护环境的双重功效。桐油和松香是我国两种重要的天然可再生资源,在目前将化工原料逐步转向可再生资源的时代背景下,它们已被广泛应用于高分子材料的合成和改性。生物基热固性树脂是一个意义重大且前景广阔的研究领域,本文就桐油和松香在生物基环氧树脂和固化剂方面的应用进行了系统的综述和展望。     

松香在高分子合成中的应用

松香主要从松树的分泌物中提炼而来,是自然界极其丰富的一种天然树脂,也是一种可再生资源.松香因其氢菲环结构刚性强而具有显著的结构特点,其刚性可与苯环媲美.在当前石油等不可再生资源日渐枯竭以及人们对环境保护日益重视的形势下,合成生物基高分子材料已成为近年来高分子研究领域的热点.因此,松香用于高分子合成的研究正日益引起重视....     

Comparative Analysis of Volatile Terpenes and Terpenoids in the Leaves of Pinus Species—A Potentially Abundant Renewable Resource

Pinaceae plants are widely distributed in the world, and the resources of pine leaves are abundant. In the extensive literature concerning Pinus species, there is much data on the composition and the content of essential oil of leaves. Still, a detailed comparative analysis of volatile terpenes and terpenoids between different species is missing. In this paper, headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry was used to determine the volatile terpenes and terpenoids of typical Pinus species in China. A total of 46 volatile terpenes and terpenoids were identified, and 12 common compounds were found, which exhibited a great diversity in the leaves of Pinus species. According to the structures and properties of the compounds, all those compounds can be classified into four categories, namely monoterpenes, oxygenated terpenes, terpene esters, and sesquiterpenes. The results of principal component analysis and cluster analysis showed that the leaves of the six Pinus species could be divided into two groups. The species and contents of volatile terpenes and terpenoids in the leaves were quite different. The results not only provide a reference for the utilization of pine leaves resource, but also bring a broader vision on the biodiversity.     

氢化松香及其衍生物的制备研究进展

氢化松香是重要的天然可再生资源松香的深加工产品之一,在电子、食品、医药等领域有着重要的用途。本文介绍了氢化松香的主要组分、氢化松香国内外工业化生产历程及氢化松香制备工艺,特别是由贵金属钯和非贵金属镍为催化剂的制备工艺的研究现状;对近年来氢化松香和二氢枞酸衍生物,主要是以氢化松香为整体的衍生物的制备研究进行了综述,并对氢化松香及其衍生物研究前景进行了展望。     

分子印迹固相萃取技术在天然产物有效成分分离分析中的应用进展

天然产物体系复杂,尤其是一些活性成分含量较低,采用一般的方法对其进行分离富集难度较大。分子印迹聚合物具有良好的亲和性和专一的选择性,将分子印迹固相萃取技术应用于天然药物资源样品前处理过程,能够选择性地分离富集复杂基质中的目标成分。本文对近几年分子印迹固相萃取技术在天然产物有效成分分离分析中的应用进行了总结,分析物包括黄酮类、多元酚类、生物碱类、有机酸类、苯丙素类、萜类以及其他一些类型的生物活性成分。     

Advances in polymer precursors and bio‐based polymers synthesized from 5‐hydroxymethylfurfural

In recent years, considerable efforts have been made regarding the synthesis of renewable chemicals from natural resources. 5‐hydroxymethylfurfural (HMF) is an interesting platform chemical which has been widely exploited due to its rich chemistry and potential availability. The versatility of HMF has been demonstrated in several areas such as fine chemicals, biofuel precursors, and polymers. In particular, the potential to replace petroleum‐based analogues in the preparation of polymers associated with high performance has been observed owing to the structural rigidity of furan rings. This review aims at critically discuss the current research studies related to the derivatives of HMF, alongside with the synthesis and characterization of (co‐) polymers derived from HMF and its derivatives. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1478–1492     

Synthesis of acrylic rosin derivatives and application as negative photoresist

Functional monomers containing a rosin moiety, maleopimaric acid anhydride (MPA) and fumaropimaric acid (FPA) were synthesized from gum rosin. Monofunctional acrylic rosin derivatives were synthesized from esterification of MPA and various acrylates, (2-hydroxyethyl acrylate) (HEA), 3-hydroxypropyl acrylate, and 4-hydroxybutyl acrylate. Monofunctional monomers were copolymerized with (methyl methacrylate) (MMA) by radical polymerization. Trifunctional acrylate was synthesized from FPA and HEA. All the monomers and polymers showed good solubility and low absorbance in the UV region (200-400 nm). Negative patterns from rosin derivatives were obtained by two methods, one is a photocuring method using trifunctional acrylate and copolymers, and the other is photocrosslinking of copolymers using a photocrosslinker under UV (I-line) radiation. Negative photoresists containing rosin moiety showed high contrast and minimum linewidth of 2.2 μm.     

Recent advances in epoxy resins and composites derived from lignin and related bio-oils

This short critical review gives an insight on the potential that lignin and its bio-oils present towards the production of thermosetting epoxy polymers and composites. Green and sustainable ways of producing monomers and polymers from renewable sources are critical and lignin, as an underutilized bio-based waste material, presents a high exploitation potential. Due to its versatile and highly functional phenolic structure, the utilization of lignin or its depolymerized fractions (bio-oils) has been investigated in the last years as alternative for fossil-based epoxy resin pre-polymers and crosslinkers. Lignin can in fact be considered as a crosslinker for epoxy resins, especially after appropriate functionalization with amine groups or with additional hydroxyl groups, or it can be modified with epoxide groups towards the replacement of toxic BPA-based epoxy prepolymers. Furthermore, lignin derived pyrolysis or hydrogenolysis bio-oils may offer highly reactive soluble oligomers that after appropriate functionalization could be utilized as bio-based epoxy prepolymers. The lignin-based epoxy resins and composites exhibit similar or even better and novel properties, compared to those of pristine epoxy polymers, thus rendering lignin a highly valuable feedstock for further utilization in the thermoset polymer industry.     

Preparation of Isotope Labeled/Unlabeled Key Intermediates in 2‐Methyl‐D‐erythritol 4‐Phosphate Terpenoid Biosynthetic Pathway

Naturally occurring terpenes constitute one of the largest groups of natural products with complicated and variable structures, and a great number of important biological activities. The 2‐methyl‐D ‐erythritol 4‐phosphate (MEP) pathway is a newly found and established biosynthetic route for terpenoids, and all the enzymes involved in this pathway can be used as targets for the screening of antibiotics. Progress in chemical and enzymatic preparation of the key intermediates in this pathway is reviewed with the emphasis on the synthesis of 1‐deoxy‐D ‐xylulose 5‐phosphate and 2‐methyl‐D ‐erythritol 4‐phosphate with isotope labels.     

Monomers and polymers from plant oils via click chemistry reactions

As a consequence of the depleting of fossil reserves and environmental issues, today, plant oils and fatty acids derived therefrom have a respectable status within the polymer chemistry community. However, maximizing the benefits of these renewable feedstocks requires the utilization of sustainable and efficient chemical transformations. The emergence of click chemistry concept and especially the renaissance of thiol‐ene addition reaction have had an impact on the way to make plant oil‐derived polymers. This highlight discusses the applicability and success of thiol‐ene addition and other click reactions in the transformation of oleochemicals into monomers and polymers. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013     

Self‐assembly of Renewable Nano‐sized Triterpenoids

Studies on plant metabolites have gained renewed interest in recent years because these can serve as renewable chemicals for the development of a sustainable society. Among various plant secondary metabolites, terpenoids constitute the major component and triterpenoids are the 30C subset of it. In recent years, triterpenoids have drawn the attention of scientific community due to many of its potential and realized applications in medicine, drug delivery, thermochromic materials, pollutant capture, catalysis, liquid crystals, etc. In this personal review, we have discussed our computational results carried out on sixty representative naturally occurring triterpenoids demonstrating that all the triterpenoids are renewable functional nano‐entities. Study of the self‐assembly of several triterpenoids such as betulin, betulinic acid, oleanolic acid, glycyrrhetinic acid and arjunolic acid and their derivatives in different liquids have also been discussed. Moreover, the utilization of the resulting supramolecular architectures such as vesicles, spheres, flowers and fibrillar networks of nano‐ to micrometer dimensions and gels have also been discussed in the perspective of green, renewable and nanos.     

From Glucose to Polymers: A Continuous Chemoenzymatic Process

Efforts to synthesize degradable polymers from renewable resources are deterred by technical and economic challenges; especially, the conversion of natural building blocks into polymerizable monomers is inefficient, requiring multistep synthesis and chromatographic purification. Herein we report a chemoenzymatic process to address these challenges. An enzymatic reaction system was designed that allows for regioselective functional group transformation, efficiently converting glucose into a polymerizable monomer in quantitative yield, thus removing the need for chromatographic purification. With this key success, we further designed a continuous, three-step process, which enabled the synthesis of a sugar polymer, sugar poly(orthoester), directly from glucose in high yield (73 % from glucose). This work may provide a proof-of-concept in developing technically and economically viable approaches to address the many issues associated with current petroleum-based polymers.     

An Artificial Estrogen Receptor through Combinatorial Imprinting

Polymeric sorbents targeting endocrine‐disrupting estrogen active compounds (EAC) were prepared by terpolymer imprinting using 17β‐estradiol (E2) as template. From a group of eight functional monomers representing Brønsted acids, bases, hydrogen‐bond donors and acceptors, as well as π‐interacting monomers, a terpolymer library that comprises all possible binary combinations of the functional monomers was prepared. Binding tests revealed that imprinted polymers exhibit a markedly higher affinity for E2 compared to nonimprinted polymers (NIPs) or polymers prepared by using single functional monomers. A combination of methacrylic acid (MAA) and p‐vinylbenzoic acid offered a particularly promising lead polymer, displaying an imprinting factor of 17 versus 2.4 for a benchmark polymer prepared by using only MAA as functional monomer. The saturation capacities ascribed to imprinted sites were four to five times higher for this polymer compared to previously reported imprinted polymers. NMR titrations and molecular dynamics simulations corroborated these results, indicating an orthogonal preference of the two functional monomers with respect to the E2 3‐OH and 17‐OH groups. The optimized polymer exhibited a retentivity for EACs that correlates with their inhibitory effect on the natural receptor. By using the optimized molecularly imprinted polymers (MIPs) in a model water‐purification system, they were capable of completely removing ppb levels of a small group of EACs from water. This is in contrast to the performance of nonimprinted polymers and well‐established sorbents for water purification (e.g., active carbon), which still contained detectable amounts of the compounds after treatment.     

Synthesis and characterization of poly(2,5‐furan dicarboxylate)s based on a variety of diols

Novel polyesters from renewable resources based on 2,5‐dicarboxylic acid and several diols were synthesized and characterized using different polycondensation techniques. The aliphatic diols were sufficiently volatile to allow the use of polytransesterifications, which gave high‐molecular weight semicrystalline materials with good thermal stability. In particular, the polyester based on ethylene glycol displayed properties comparable with those of its aromatic counterpart, poly(ethylene terephthalate), namely, the most important industrial polyester. The use of isosorbide gave rise to amorphous polymers with very stiff chains and hence a high glass transition temperature and an enhanced thermal stability. The interfacial polycondensation between the acid dichloride and hydroquinone produced a semicrystalline material with features similar to those of entirely aromatic polyesters, characterized essentially by the absence of melting and poor solubility, both associated with their remarkable chain rigidity. The replacement of hydroquinone with the corresponding benzylic diol was sufficient to provide a more tractable polyester. This study provided ample evidence in favor of the exploitation of furan monomers as renewable alternatives to fossil‐based aromatic homologs. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of new terpene derivatives via ruthenium catalysis: rearrangement of silylated enynes derived from terpenoids

Enyne rearrangement of silylated modified terpenoids has been used as the key step for the synthesis of new terpenes and terpenoids. The catalytic system generated in situ from [RuCl₂(p-cymene]₂, 1,3-bis(mesityl)imidazolinium chloride and cesium carbonate is able to perform the transformation of silylated 1,7-enynes into cyclic siloxanes. Selective cleavage of the silicon-carbon and silicon-oxygen bonds by simple reactions has been performed to afford new terpenes and terpenoids by formal addition of a C5 unit.