Aliphatic polycarbonates, synthesis

Carbon dioxide can itself be used as a feedstock as well as a solvent for the synthesis of aliphatic polycarbonates by precipitation polymerization. Propylene oxide [39] and 1,2-cyclohexene oxide [40] can both be polymerized with CO2 using a heterogeneous zinc catalyst (Scheme 10.21). 

Carbon dioxide is a widely available, inexpensive, and renewable resource. Hence, its utilization as a source of chemical carbon or as a solvent in chemical synthesis can lead to less of an impact on the environment than alternative processes. The preparation of aliphatic polycarbonates via the coupling of epoxides or oxetanes with CO2 illustrates processes where carbon dioxide can serve in both capacities, i.e., as a monomer and as a solvent. The reactions represented in (1) and (2) are two of the most well-studied instances of using carbon dioxide in chemical synthesis of polymeric materials, and represent environmentally benign routes to these biodegradable polymers. We and others have comprehensively reviewed this important area of chemistry fairly recently. Nevertheless, because of the intense interest and activity in this discipline, regular updates are warranted. 

Lu L, Huang K (2005) Synthesis and characteristics of a novel aliphatic polycarbonate, poly [(propylene oxide)-co-(carbon dioxide)-co-(gamma-butyrolactone)]. Polym hit 54 870-874... 

Liu Y, Huang K, Peng D, Wu H (2006) Synthesis, characterization and hydrolysis of an aliphatic polycarbonate by terpolymerization of carbon dioxide, propylene oxide and maleic anhydride. Polymer 47(26) 8453-8461... 

Chen, X. McCarthy, S.P. Gross, R.A. Synthesis, characterization, and epoxidation of an aliphatic polycarbonate from 2,2-(2-pentene-l, 5-diyl)trimethylene carbonate (cHTC) ringopening polymerization. Macromolecules 1997, 30 (12), 3470-3476. 

Synthesis of Aliphatic Polycarbonates and Poly(Methyl Aciylate) Derivatives... 

Scheme 6.12 Examples of titanium precursors for the synthesis of aliphatic polycarbonates.

Zhu, W., et al. 2011. High-molecular-weight aliphatic polycarbonates by melt polycondensation of dimethyl carbonate and aliphatic diols synthesis and characterization. Polymer International 60(7) 1060-1067. 

Early developments in aliphatic and aromatic polycarbonates. The first significant documentation of aromatic polycarbonates synthesis began with Einhom [24]. He reacted hydroquinone, resorcinol, and catechol with phosgene in a pyridine solution, obtaining linear polymers from hydroquinone (an insoluble crystalline powder that melted above 280°C) and resorcinol (an amorphous material that melted with decomposition at 190 to 200°C), and a cyclic carbonate from catechol. Subsequent research was focused on finding more efficient preparation methods and on improving material properties [25]. 

This chapter reviews the research and the most relevant progresses in polycarbonates (PC)s science and provides a comprehensive source of information on history, synthesis, processing and applications. The application of different polymerization procedure of the commercial aromatic bisphenol-A polycarbonate (referred herein as PC) and the innovative enzymatic catalysed polymerization of aliphatic polycarbonate are summarized. Due to the high engineering performance of PC polymer, an extensive section on mechanical, electrical, chemical and thermal properties is included. The thermo and photo oxidative behaviours, the hydrolytic stability and the consequent modification on PC chemical structure are also discussed. The development of PC polymeric materials such as composites and blends are also addressed, emphasizing in particular the properties and the applications of impact modified PC blends and even of the PC/Polyester systems. 

Because CO2 is a nontoxic, nonflammable, and inexpensive substance, there is continued interest in its activation with transition metal complexes and its subsequent use as a Cl feedstock (1,2). Even though CO2 is used to make commodity chemicals such as urea, salicylic acid and metal carbonates, efficient catalyst systems that exploit this feedstock as a comonomer in polymerization reactions have been elusive (3,4). One reaction that has been considerably successful is that of CO2 with epoxides to yield aliphatic polycarbonates (Scheme 1) (5). Of particular significance is the synthesis of poly(propylene carbonate) (PPC), because the starting materials—propylene oxide (PO) and CO2—are inexpensive. 

Because polymer properties are governed by the constitution and orientation of the side chains, a great deal of research has been aimed at controlling and modifying these features in aliphatic polycarbonates. Initial research focused on catalyst discovery thus PO and CHO were the model epoxides. A modest amount of research, however, has been directed at the synthesis of other polycarbonates, and more recently, the properties of such materials have been examined. 

Gabriel Rokicki is a chemistry professor at the Faculty of Chemistry, Warsaw University of Technology, Poland, where he received all his academic education (MSc in 1971, PhD in 1989, and tenure professor in 2002). His current scientific activities include synthesis, stmcture, and properties of polymer materials, such as aliphatic polycarbonates, polyurethanes, epoxy resins, and biodegradable polymers. He has devoted a special interest to the use of functional polymers in obtaining specialty ceramic materials as well as to polymer recycling. Earlier major interests included the utilization of carbon dioxide and cyclic carbonates in the synthesis of condensation polymers. Another topic of interest was polymeric ion-sensors based on modified calixarenes. He is the author and coauthor of 160 scientific papers and holds more than 50 patents in the above-mentioned areas. At the Faculty of Chemistry of Warsaw University of Technology, he conducts lectures on polymer chemistry and technology. 

The synthesis and characteristics of poly(ester-ester) multiblock copolymers from DMT, alkyl glycols (C2-C10), and pivalolactone have also been described [36,37]. More details about the exchange of units between chains or segments in polymer systems, i.e., the type of the sequential order in condensation copolymers, were given by Fakirov and Denchev [185]. Roslaniec et al described the synthesis and physical properties of PEE containing aliphatic polycarbonate soft segments [38,40,41]. Multiblock copolyesters can also be obtained by an... 

The discovery by Inoue (20) that epoxides and carbon dioxide could be copolymerized in the presence of a diethylzinc water catalysts offers an additional route to aliphatic polycarbonates. The catalyst types which are effective for this polymerization were expanded upon in later work, demonstrating that zincipyrogallol (21) and aluminum-porphyrin (22) catalyst systems afforded the desired linear polycarbonates. The synthesis has been applied to fimctional epoxides with pendent hydroxy (23) and o-nitrobenz)d ether groups (24), the later being investigated as a new photoresist scheme. 

One of the most interesting properties of aliphatic polycarbonates is their clean thermal degradation to gaseous products (5,77). In this paper we describe the synthesis... 

Liu Zhi-lan, Zhou Yu, Zhuo Ren-xi (2003), Synthesis and properties of functional aliphatic polycarbonates , J Polym Sci, Part A Polym Chem, 41(24), 4001 006. 

Several review articles on biodegradable polymers and polyesters have appeared in the literature [12-22]. Extensive studies have been carried out by Al-bertsson and coworkers developing biodegradable polymers such as polyesters, polyanhydrides, polycarbonates, etc., and relating the structure and properties of aliphatic polyesters prepared by ROP and polycondensation techniques. In the present paper, the current status of aliphatic polyesters and copolyesters (block, random, and star-shaped), their synthesis and characterization, properties, degradation, and applications are described. Emphasis is placed primarily on aliphatic polyesters derived by condensation of diols with dicarboxylic acids (or their derivatives) or by the ROP of cyclic monoesters. Polyesters derived from cyclic diesters or microbial polyesters are beyond the scope of this review. 

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