Effect Of Oligomer Containing Ionic Liquid Moiety On The Structure And Properties Of PLA And Its Blends

In this work,Poly(lactic acid)(PLA)/oligomer containing ionic liquid moiety(IL)and Poly(lactic acid)(PLA)/Poly(?-caprolactone)(PCL)/IL blends were prepared by solution blending,and the effect of the structure of the IL on the evolution of the aggregate structure and properties of PLA were systematically studied by using differential scanning calorimetry(DSC),polarizing optical microscopy(POM),and X-ray diffraction(XRD)and universal testing machine.Besides,the effects and mechanism of IL on the fabrication of the aggregate structure and phase interface of PLA/PCL blend were aslo explored in detail.The main contents are described as follows:(1)The effects and mechanism of IL with different structure on the aggregate structure of PLA.The results shows that IL14 with short molecular chains and low amounts of ionic moiety had the most obvious effect on enhancing the cold crystallization ability of PLA,but it could not strongly improve the melt crystallization ability of PLA.IL19 could improve the cold crystallization ability of PLA,but it would obviously decrease the melt crystallization ability of PLA.IL34,which has relative long chain and the high amounts of ionic liquid moiety,could obviously improve the cold crystallization ability and melt crystallization ability of PLA.The reson is that IL14 could easily diffuse into the PLA chains due to its structure,and promote the disentanglement process of PLA chains due to the non-covalent interaction between IL14 and PLA chains,resulting in the significantly improvement of the mobility of PLA chains.However,the PLA chains with high mobility could not stack regularly during the melt cooling process hence the melt crystallization ability of PLA was weak.IL19 had a weak effect on the crystallization process of PLA because it was prone to aggregation.IL34,which has large amounts of ionic moiety,could not only enhance the mobility of PLA chains,but aslo fromed ionic clusters in the melt,which could serve as nucleation sites;besids,the strong non-covalent interaction between IL34 and PLA could induce PLA chains to accumulate on the surface of ionic clusters and stack regulary.Therefore,IL34 could significantly improves the melt crystallization ability of PLA.The mechanical test shows that PLA could obtain an excellent comprehensive performance with the addition of IL34.(2)The results of the investigation of effect of IL34 on the phase interface and aggregate structure indicates that the fractionated crystallization of PCL was mitigated and the crystal structure of PCL was more perfect with the addition of IL34.Additionally,compact crystal region was formed in PLA and the amorphous region could have a strong interaction with crystalline region,which was proved by POM.The interface adhesion of PLA and PCL was significantly enhanced with the addition of IL34 that is pronounced by SEM,besids,the PCL phase transformed from spherical structure to cylindrical structure and the phase structure of the blends transformed from island structure to bicontinuous structure by increasing the amounts of IL34,which pronounced that IL34 had a positive effect on controlling the phase morphology of PLA/PCL blend.The rheological curve shows that the storage modulus of PLA was significantly increased in the low frequency region with the addition of IL34,which proves that IL34 could promote the physical entanglement and chemical crosslinking of PLA and PCL chains,resulting in significantly improving the compatibility of PLA and PCL.TEM images could also demonstrated that IL34 has a positive effect on controlling the morphology of PLA/PCL blends.The mechanical test shows that a high-performance PLA material could be achieved with the addition of IL34.