Preparation Of Rare-Earth Hybrid Ferrocene-Based Polyurethanes For X-ray Protection

The rapid development of nuclear energy has made the increasing application of ionizing radiation,and the environmental and health hazards caused by it are getting more and more attention.The creation of high-performance radiation shielding materials is imperative.The current lead-based shields are highly toxic,clumsy and rigid,and they have poor reliability due to insufficient mechanical properties,which are contrary to the development of nextgeneration protective materials.Hybridization of the most radiation-tolerance elastomer polyurethane(PU)with green and non-toxic rare earths is one of the effective ways.This thesis focused on the unique role of ferrocene in shielding materials,aiming to overcome the problems of insufficient mechanical properties and poor atom economy of flexible materials,to develop novel shielding materials.At first,rare-earth hybrid ferrocene-based PUs were prepared.Using ferrocene-based diols as chain extenders,PUs with different ferrocene-based hard segments structures were obtained by solution polymerization,which were modified with pendant sulfonate anions and then hybridized with Gd3+,Eu3+,and Sm3+.Rare earths were mainly directed into the hard segments and anchored within the hard domains through noncovalent crosslinks.Ferrocene can interact with rare-earth ions,while regulating the coordination of carbonyl with rare earths.Bisferrocene-based PUs have the best dispersing ability for rare earths and make them distributed at the atomic to nanocluster level below 2.9 nm.The maximum density of the prepared hybrid bisferrocene-based PUs is 1.28 g cm-3,which has reached the level of commercial natural rubber-based protective materials.Secondly,the properties of rare-earth hybrid PUs were studied.Bisferrocene enables PUs to maintain excellent mechanical properties after hybridization.For Gd3+,Eu3+,and Sm3+hybrid bisferrocene-based PUs with sulfonation degree(DS)of 71%.the break strengths were 27.8±0.2 MPa,35.4±1.1 MPa,and 29.4±0.6 MPa,and the elongation at break were 575±11%,612±15%,and 583±6%,respectively.The mechanical properties were the best among the reported flexible X-ray shielding materials as we know.At the same time,they still maintained good thermal stability.In addition,the bisferrocene significantly improves the solvent resistance of the hybrid material,which promoted the green development goal of its industrial application.At last,the research aimed at the application of rare-earth hybrid ferrocene-based PUs in radiation shielding.It has been confirmed that ferrocene can synergistically improve the shielding ability of hybrid materials,and the effect of bisferrocene was more obvious.Thus,the atom utilization efficiency of rare earths was significantly improved by ferrocene.Gd3+hybrid bisferrocene-based PU with the DS of 71%had the best shielding ability,which can be close to 0.25 mmPb at 80 kV tube voltage,and the mass attenuationicient was above 0.84 cm2 g-1 at 33～83 keV photon energy with only 11.26 wt%Gd3+.The atomic efficiency has exceeded most reported flexible materials.Our strategy has promoted the development of flexible radiation shielding materials towards green,lightweight,and high atom efficiency.