Non-catalytic, non-isocyanate conditions for the recovery of heavy metal ions can be prepared a cyclic thiourethane

Polythiourethane (thiourethane also known as) is a promising material polymer containing a sulfur, nitrogen heteroatom. It has special properties such as high refractive index, good biocompatibility, and capability of complexing heavy metal ions, and the like. Conventional synthetic methods include polycondensation dithiol compound with a diisocyanate polyaddition reaction there are five yuan bifunctional cyclic thiocarbonate with a diamine and the like. Synthesized according to the above process cumbersome, toxicity and poor stability. Since the synthetic method is very limited, the less thiourethane stories.

无催化、非异氰酸酯条件制备可用于回收重金属离子的环状硫代聚氨酯
Figure 1 a schematic view of the polymerization reaction.

To solve this problem, the teacher Ming Luo Changshu INSTITUTE TF atmospheric pollutants carbon oxysulfide (COS) turning waste into a sulfur-containing monomer used to make three-membered ring nitrogen compound N-methyl-2- aziridines (MeAz) at room temperature, no spontaneous polymerization catalyst under conditions with high selectivity, high activity to give a clear preparation of poly mono thiocarbamate (FIG. 1) . It can be completed within 2 hours at room temperature, up to 95% selectivity of the polymer, and the polymer having a full alternating structure. On further by matrix-assisted time of flight mass spectrometry to study the structure of the main chain of the polymer (FIG. 2), it found that the polymer having a ring topology. It refers to a polymer containing no cyclic end groups, the polymer structure of the butt ring. Synthesis of Polymer Science cyclic polymers has been a very special and challenging task. OF explanation, the non-catalyzed polymerization reaction and the polymer is formed from an annular particularity of its special mechanism zwitterionic copolymer (zwitterionic copolymerization). COS and MeAz two monomers spontaneously zwitterions intermediate, intermediate interact with each other to form a polymer chain growth, and ultimately, the end of the zwitterionic quenching occurs polymer chain to form a cyclic structure.

无催化、非异氰酸酯条件制备可用于回收重金属离子的环状硫代聚氨酯
Figure 2. The polymer matrix-assisted time of flight mass spectrometry FIG. Source:.. ACS Sustain Chem Eng

The thiourethane having special thermal degradation. At 200 ℃ thereof for 1.5 hours to complete degradation of the polymer was recovered five- thiocarbamate (known as thiazolidin-2-one) (FIG. 3). Thiazolidine-2-ones compounds are important pharmaceutical intermediates in organic synthesis, andBlock. This indicates that the polymer may be fully recovered by thermal degradation with a use value of a small molecule. Throughout the polymerization and the degradation process is sustainable, and has high atom economy.

无催化、非异氰酸酯条件制备可用于回收重金属离子的环状硫代聚氨酯
Figure 3 a schematic view of thermal degradation of the polymer.

The thiourethane aqueous solution of heavy metal ions such as mercury, lead, cadmium ions exhibit excellent adsorption effect. Heavy metals and thermal degradation characteristics of the polymer adsorption researchers designed by combining a green method (FIG. 4) An adsorption and recovery of lead ion from an aqueous solution. NATURAL lead ion adsorption polymer precipitate was centrifuged to obtain a polymer – metal mixture. The mixture was heated and distilled high temperature, lead-containing compounds may be collected to give a clear and clean, and five-membered cyclic thiocarbamate residue obtained. And absorb the whole recovery process in line with the concept of sustainable development and green chemistry, green provides a method does not generate solid waste and VOC emissions harmful to the recovery of metals.

无催化、非异氰酸酯条件制备可用于回收重金属离子的环状硫代聚氨酯
FIG 5.COS-MeAz copolymerization and recovery of lead ion FIG. Source:.. ACS Sustain Chem Eng

The study reported a method which does not require a catalyst, can be recycled to the thermal degradation of the synthesis of cyclic thiourethane structure of the non-isocyanate route. Synthesis thiourethane provides a new method for the work, while providing a new method for the preparation of a cyclic polymer and adsorption of heavy metal ion recovery is also provided a method of green (FIG. 5). This achievement with Non-Isocyanate and Catalyst-Free Synthesis of A Recyclable Polythiourethane with Cyclic Structure was published in ACS Sustainable Chemistry & Engineering (DOI: 10.1021 / acssuschemeng.0c00435) on. First author Changshu Institute of Technology and the University of Suzhou joint training Master Wu double. Article link: https://pubs.acs.org/doi/abs/10.1021/acssuschemeng.0c00435

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