Compatibilization Of Carbon Nanodots For The Immiscible Polymer Blends

Polymer blending can combine the desirable properties of the both components to develop novel materials with excellent performance.However,the intrinsic thermodynamically immiscibility of most polymer pairs forces us to select appropriate compatibilizers for polymer blends to enhance the compatibility of the two phases and acquire high performance blends with favorable micromorphology and macroscopic properties.The rigid inorganic nanoparticles have unique advantages in improving the interfacial compatibility of the immiscible polymer systems because of their small scale and high specific area.However,nanoparticles usually require surface modification,which is complex and thus with low production yield:The functional groups of nanoparticles are single and thus limit the realization of further modification.Carbon nanodots(CDs)as a novel type of carbon nano-materials are generally less than 10 nm,that have the advantages of simple preparation method,wide sources of synthetic materials,easy surface functionalization,low toxicity and good biocompatibility.This study utilized CDs as compatibilizers for the first time,to promote the compatibilization of immiscible polymer blends.We started from the structural design of CDs,and selected appropriate raw materials to synthesis suitable CDs with the surface of required molecular chains and functional groups.Through the regulation of the size,surface chain density and chain length of CDs,we obtained the changing law of the effect of the surface structure and loading of CDs on the micromorphology and macroscopic properties of the blends,which could have a good application prospect in biomaterials and engineering materials.The research contents are mainly divided as follows.In the second chapter,silane-functionalized carbon nanodots(Si-CDs)were prepared using silane coupling agent KH792 as passivation agent and citric acid as carbon source by one-step solvothermal method.The yield was as high as 82%.Silane coupling agent acts as surface passivation agent and solvent for preparing CDs,which is simple,efficient and environmentally friendly.Such Si-CDs were used as compatibilizers for thermoplastic polyurethane/methyl vinyl silicone rubber(TPU/MVQ)blends.We systematically investigated the effect of Si-CDs size,surface graft density,and loading on the micromorphology and performance of TPU/MVQ blends.The results showed that Si-CDs-High with smaller size and the highest surface silane molecular chain density had the best compatibilization effect,that can reduce the size of the MVQ dispersed phase by about 3 times at an additive amount of 3 wt%.Furthermore,combining CDs structure,interface interaction analysis and infrared spectroscopy studies clarified the compatibilization mechanism of carbon quantum dots to TPU/MVQ blends.As-prepared Si-CDs could be stabilzed at the blend interface,improve the interfacial adhesion,prevent the MVQ phase coalescence and finally improve the thermal stability and mechanical properties of the TPU/MVQ blends.In addition,the TPU/MVQ polymer blends compatibilized with Si-CDs exhibited tunable fluorescence under UV light,paving a new possibility for biological field.In the third chapter,novel nitrogen-doped CDs with different chain lengths(NH2-CDs-BAPTMDS,NH2-CDs-2000 and NH2-CDs-4000)were synthesized using the blocking agent BAPTMDS or the successfully synthesized amino silicone oils with molecular weights of 2000 and 4000 as passivators and citric acid via one-step solvothermal method.Through focusing on the effect of surface chain length on the morphology and performance of TPU/MVQ blends,we found that NH2-CDs-2000 with a side chain of 2000 molecular weight amino silicone oil had the best compatibilization ability.With the incorporation of 0.5 wt%NH2-CDs2000 into the TPU/MVQ blend,the size of dispersed phase shifted from original 2.53±1.03 ?m to 0.66±0.21 ?m,and the tensile strength was also improved.This is mainly due to the more effective intermolecular interaction between NH2-CDs-2000 and the molecular chains of the twophase polymer at the interface.Compared with commercial EMA compatibilizer,the size of the dispersed phases in TPU/MVQ blends compatibilized by EMA and NH2-CDs-2000 were 0.99±0.34 and 0.43±0.11 ?m respectively with the addition of 3 wt%,indicating that asobtained NH2-CDs-2000 has a more effective compatibilization efficiency for TPU/MVQ blends.The reason is that the rigid NH2-CDs-2000 as a nanoparticle compatibilizer can effectively stabilize the phase morphology at the interface and prevent the integration of dispersive phases.In the fourth chapter,supported catalysts(Pd(II)/MIL-100(Fe))for hydrogenation of NBR at room temperature were prepared by combining the one-step hydrothermal method and the solution impregnation menthod.The catalysts have good hydrogenation activity for hydrogenation of NBR at mild temperature and the hydrogenation degree can reach to 93%.Afterwards,the CDs covered with epoxy groups(OSiCDs)were prepared by one-step solvothermal method using silane coupling agent GPTMS and citric acid,and the effect of their surface structure on the micromorphology of HNBR/PA6 polymer blends was also investigated.With the addition of OSiCDs and carboxyl butyronitrile(XNBR)into the blends simultaneously,XNBR can react with the epoxy groups of OSiCDs and grafted onto the surface of OSiCDs to form XNBR functionalized OSiCDs(XNBROSiCDs)in situ.The most efficient compatibilizer can be obtained when change the ratio of XNBR to OSiCDs to 2:1,which could reduce the size of the dispersed phase from 2.17±0.50 ?m to 0.94±0.29 ?m and successfully promote the compatibility of the two phases.