报告时间：2023年10月20日(星期五) 上午10:00
报告地点：25号楼346会议室
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材料科学与工程学院
2023年10月17日
报告一题目：Chemical Recycling of Polymers
报告人：Ema Žagar教授（National Institute of Chemistry, Slovenia）
报告人简介：
Dr. Ema Žagar received her PhD from the Faculty of Chemistry and Chemical Technology at the University of Ljubljana in 1999. From 2012, she has been a head of Department of Polymer Chemistry and Technology at the National Institute of Chemistry. Her current research interests include polymer recycling and comprehensive characterization of complex polymers using light scattering and various liquid chromatographic techniques. She is (co-)author of 130 peer-reviewed papers, three granted patents and five patent applications.
报告摘要：
Plastic materials are key components of almost every technology today. After their service life, they represent a waste that has become a growing environmental problem. Mechanical recycling includes high-temperature melt-reprocessing of waste plastics and is currently the most established. However, it is not suitable for thermoset plastics with a cross-linked structure and those that encounter difficulties in reprocessing. In addition, mechanical recycling of polymers is hindered by deterioration of material performance (down-cycling) as a result of partial cleavage of polymer chains during high temperature reprocessing. For this reason, other technologies such as chemical and thermal recycling of plastic waste are being intensively developed. Chemical recycling is particularly suitable for polymers with chemically labile groups in the backbone such as polyesters, polyamides, polyurethanes, and polycarbonates. Depolymerization of these polymer types is usually carried out by solvolysis using nucleophilic solvents in the presence of a catalyst.
Here we present chemical recycling of different types of aliphatic polyamides by acid-catalyzed hydrolysis using microwaves as a heating source. The advantages of our chemical recycling method compared to known methods are the rapid (several minutes) and efficient conversion of polyamides into monomers as the only degradation product, which greatly simplifies the procedures for isolation and purification of the recovered monomers and reinforcing additives (glass fibers, carbon fibers) in the case of composites. The secondary raw materials obtained by this process are of comparable quality to commercially available chemicals used in polyamide production.
In the next part we will present the advantages and disadvantages of the different methods of degrading flexible polyurethane (PU) foams. We will discuss the influence of the experimental conditions, such as reaction temperature, reaction time, and type and amount of degradation reagent, on the polyol functionality, molecular weight characteristics, presence of side products, and the degree of degradation of the remaining PU foam hard segments, as well as the influence of the structural properties of the recycled polyols on the quality of the flexible PU foams produced from recycled polyols.
报告二题目：Ring-Opening Polymerization of Heterocyclic Monomers
报告人：David Pahovnik博士（National Institute of Chemistry, Slovenia）
报告人简介：
Dr. David Pahovnik is a research fellow in the Department of Polymer Chemistry and Technology at the National Institute of Chemistry, Ljubljana, Slovenia. He received his Ph.D. in Chemistry from the Faculty of Chemistry and Chemical Technology at the University of Ljubljana in 2012. In 2013-2014 he was a postdoctoral fellow at prof. Nikos Hadjichristidis group in the Polymer Synthesis Laboratory, King Abdullah University of Science and Technology (KAUST), Saudi Arabia. His current research work focuses on the synthesis and characterization of polymers prepared by ring-opening polymerizations of various heterocyclic monomers.
报告摘要：
Ring-opening polymerization (ROP) of heterocyclic monomers such as lactones, lactides, epoxides and α-amino acid N-carboxyanhydrides (NCAs) is an invaluable tool for the preparation of biocompatible and (bio)degradable polymers in a controlled manner. Since polyesters/polyethers prepared by ROP propagate through hydroxyl group, which is a slow initiating group for ROP of NCAs, the synthesis of polypeptide-based hybrid block copolymers usually requires multi-step reactions. To overcome the issue of slow NCA initiation by the hydroxyl group, we separated the slow initiation from the fast propagation and instead performed them sequentially. The developed method has been successfully applied for the synthesis of block copolymers using hydroxyl-terminated macroinitiators and for one-pot sequential ROP of cyclic esters or carbonates and NCA, which differ not only in reactivity but also in the type of the propagating species.
ROP can also be used for the preparation of various porous polymers. By performing ROP in the oil-in-oil high internal phase emulsions (HIPE), we have prepared fully degradable macroporous cross-linked PCL polyHIPE foams that exhibit shape memory behaviour. HIPE templating was extended to ROP of NCA to prepare HIPE templated synthetic polypeptide scaffolds, where experimental conditions were carefully tuned to prevent scaffold foaming due to CO2 evolution. By deprotecting the corresponding polypeptide scaffolds, the stimuli-responsive polypeptide hydrogels were prepared with fully preserved polyHIPE morphology. The hydrogels exhibit pH-dependent behavior, which can be modulated together with their mechanical properties by changing the chemical composition of the polypeptides. The mechanical properties of polypeptide scaffolds were also modulated by copolymerization with polyester allyl-functionalized star macromonomers using thiol–ene photopolymerization.