Towards greener synthesis of sustainable terpene-based monomers for renewable polymers

项目背景（确定问题及其对可持续性的重要性和相关性）随着政府和社会不断向更可持续的未来转变，对生物来源的和理想的生物降解塑料和聚合物的需求正在增加。从广义上讲，为了生产这种材料，需要考虑四个关键方面及其对环境的影响：（i）原料来源，（ii）构建单元的合成路线，（iii）聚合物制造的条件，以及（iv）新材料的可用性和性能。聚合物材料的理想原料应该是天然来源（植物），廉价和非食品基，以避免与食品市场的竞争。单体的合成路线有益于环境友好，具有温和或可回收的溶剂和试剂，以及最大化的产率和原子经济性。最后，所获得的绿色聚合物应允许与传统的合成聚合物相当的性能和性质，同时具有使用目前工业上实施的技术可生物堆肥或可回收/可降解的优点。萜类化合物由于其低成本、副产物性质和固有的功能性而被认为是合成单体的有希望的天然原料。在此，我们提出了简单的，绿色氧化裂解化学的应用程序，四个选定的环状，烯属单萜合成一系列的生物质为基础的单体单元与生产可持续的聚酰胺，聚酯，聚碳酸酯和聚氨酯兼容。在这项研究中，我们的主要目标是从四种选择的单环和双环烯属萜烯合成一系列新的，可持续的单体：α-蒎烯，3-$>烯，α-松油醇和松油烯-4-醇。一旦获得官能化单体萜烯，就可以合成具有可调化学和物理性质的各种聚合物材料。拟建项目的第一阶段旨在通过氧化的二羟基化合物的氧化裂解将所选的烯烃萜类化合物转化为1，6-二醇，其具有直接与天然二酸或天然二酸的二甲酯反应并通过缩聚聚合产生各种聚酯的潜力。另一系列聚酯将通过烯烃萜烯直接氧化裂解成双官能单体单元（羟基酸）来获得。聚酰胺是通过将1，6-二羰基中间体通过还原胺化转化为二胺，然后与各种天然二羧酸聚合而获得的。拟议项目的第二阶段旨在利用合成的二醇和二胺获得结构中含有胺部分的聚酯和聚氨酯。通过使基于萜的1，6-二胺与羰基二咪唑反应，随后使获得的二甲酰胺与萜1，6-二醇反应，可以获得多萜。具有嵌入的胺部分的聚酯由于具有能够被环境中的细菌分解的两个官能团而特别令人感兴趣。基于萜类化合物的丙烯酸酯可以通过二醇与丙烯酸的酯化来获得。随后脂肪族丙烯酸酯与二胺的加成聚合提供了过多的潜在生物降解酯。

Project background (identification of the problem and its importance and relevance to sustainability) Demand for bio-sourced and ideally bio-degradable plastics and polymers is increasing as the governments and the society are making a continuous shift towards a more sustainable future. Broadly, to produce such materials, the four crucial aspects and their environmental impact need to be considered: (i) the source of the feedstock, (ii) the synthetic route towards building blocks, (iii) the conditions for polymer manufacture, and (iv) the usability and performance of newly created materials. The ideal feedstock for building blocks of polymeric materials should be of natural origin (plants), inexpensive and non-food based to avoid the competition with food market. The synthetic route to monomers benefits of being environmentally benign, with mild or recoverable solvents and reagents, and maximized yield and atom economy. Finally, the green polymers obtained should allow for comparable performance and properties with traditional, synthetic polymers, with the simultaneous advantage of being bio-compostable or recyclable/degradable using currently industrially implemented technologies. Terpenes and terpenoids have been recognized as promising natural starting materials for monomer synthesis due to their low cost, by-product nature and intrinsic functionality. Herein, we present the application of simple, green oxidative cleavage chemistry to four selected cyclic, olefinic monoterpenes to synthesise a range of biomass-based monomeric units compatible with the production of sustainable polyamides, polyesters, polycarbonates, and polyurethanes. Proposed solution and methodology In this study, our primary aim is to synthesise a range of novel, sustainable monomers from four selected mono and bicyclic olefinic terpenes: a-pinene, 3-carene, a-terpineol and terpinene-4-ol. Once the functionalized monomeric terpenes are obtained, various polymeric materials with tuneable chemical and physical properties might be synthesised. Phase 1 of proposed project aims to convert the chosen alkene terpenoids into 1,6-diols, via oxidative cleavage of oxidized synthons, which have the potential to directly react with natural diacids or the dimethyl esters of natural diacids and produce various polyesters via polycondensation polymerization. Another range of polyesters is going to be accessed via direct oxidative cleavage of olefinic terpenes into difunctional monomeric units (hydroxy acids). Polyamides are to be acquired by transforming 1,6-dicarbonyl intermediates, via reductive amination, into diamines, and subsequent polymerization with a diverse range of natural dicarboxylic acids. Phase 2 of proposed project aims to utilize the synthesised diols and diamines to obtain polyesters with amine moiety incorporated in the structure, and polyurethanes. Polyurethanes can be acquired by reacting terpene-based 1,6-diamines with carbonyldiimidazole, and subsequent reaction of acquired dicarbamides with terpenoic 1,6-diols. Polyesters with embedded amine moiety are of particular interest due to possessing two functional groups capable of breaking down by bacteria in the environment. Terpenoid-based acrylate esters can be acquired by esterification of diols with acrylic acid. The subsequent addition polymerization of aliphatic acrylates with diamines affords the plethora of potentially biodegradable esters.