Synthesis,Properties And Application Of Block Polyesteramide Based On Polyamide 6

Polymer materials have close relationship with people’s daily life.With the development of society,we are urgent to improve the comprehensive performance of polymer materials and realize its functionalization.It is well known that the structure of materials determines the properties.It’s a hot topic to prepare materials with comprehensive properties by means of physics and chemistry.In this paper,a series of triblock poly（ε-caprolactone-b-ε-caprolactam-b-ε-caprolactone）（PCL-b-PA6-b-PCL）with well-design structure and adjustable composition were prepared.The spherulite morphology,crystal orientation and arragement of lamellae were studied from different scales.The influence of triblock copolymer on the structure and performance of PA6/PCL blends was also investigated.Considering that PA6 has a large number of amide groups,which provided hydrogen bond donors and acceptors.The enhanced solubility of copolymer was favor of its introduction into polyurethane.The effect of triblock copolymer on microphse separation,hierarchical hydrogen-bond,mechanical properties,self-healing and conductivity of polyurethane/ionic liquid have been investigated,which provided basic data and guidance for the preparation of PA6-based materials with excellent comprehensive properties.The specific content of this paper is as follows:1.Owing to the dissolubility of PA6 and transacylation of PCL,we found PA6 could dissolve in N,N-Dimethylformamide（DMF）at a certain temperature.A series of PCL-b-PA6-b-PCL with well-design structure and different compositions were synthesized by bulk polymerization and solution ring-opening polymerization.Firstval,the amino terminal-group was confirmed by acid-base neutralization titration structure.Besides,the molecular weight,composition and block sequence of triblock copolymer were determined by gel permeation chromatography（GPC）,¹H,DOSY and ¹³C NMR.The thermal properties of the triblock copolymer were studied.In addition,the influence of copolymer composition on its thermal properties,crystal structure and degradation behavior were investigated.The mechanism of the effect of PA6block on the mechanical properties and degradation behavior of the copolymer was discussed,which provided a simple and effective method for the synthesis of PA6 based block copolymer,and provided basic data for the relationship between the structure and properties of the copolymer.2.For the triblock copolymer PA6-PCL-1:6.2,there are three unique spherulites observed under polarized optical microscope（POM）through changing crystallization conditions,including curve-like spherulites,ring-banded spherulites and composite spherulites with both characters above.The dependence of crystal morphology on temperature was studied and it was found that the ring-banded spherulite gradually turned into curve-like spherulites with the increase of crystallization temperature.Combined with differential scanning calorimetry（DSC）and in situ infrared（FTIR）,it was proposed that the appearance of curved spherulite was caused by the simultaneous crystallization of PA6 and PCL.By adjusting the crystallization conditions,PA6 was pre-crystallized,and the final crystal morphology was dominated by ring-banded spherulite.It was further confirmed that only when PA6 and PCL crystallized simultaneously,curve-like spherulites could be obtained,which reflected that the internal stresses of different forms played a decisive role in the crystal morphology.By means of atomic force microscopy（AFM）and scanning electron microscopy（SEM）,it is found that the curve-like spherulite consist of flat-on and tilted terrace lamellae,which are arranged alternately in the tangential direction.Thin film and ultra-thin film were investigated in order to have a deep insight into tilted terrace lamellae,it shows a tilted orientation of lamella.In conclusion,the curved spherulite was arraged alternatively by flat-on and tilted lamellae along the tangential direction.3.The effect of triblock copolymers with different compostions on the phase separation morphology of PA6/PCL were evaluated.It was found that PA6-PCL-1:1.9 can significantly improve the phase separation morphology of blends.Subsequently,a certain amount of PA6-PCL-1:1.9 was added into binary blends with different compositions to study the changes in physical,thermal and water absorption properties of the blends through SEM,DSC and FTIR,as well as their relationship between structure and properties.It was found that the mechanical properties of different blends showed different trends after compatibilization,indicating that the content of compatibilizers had a significant effect on the properties.Then,the composition of the blend was fixed,the content of the compatibilizer changed,and the changes of mechanical and thermal properties were investigated.It is found that the appropriate amount of compatibilizer can improve the compatibility,toughness and reduce the water absorption,but the excessive amount of compatibilizer makes the droplet phase aggregated,which is not conducive to the improvement of performance.4.Owing to the better solubility of PCL-b-PA6-b-PCL,the triblock copolymer is introduced in polyurethane as macrodiol or chain extender to prepare a series of poly（urethane-amide）with well-design structure and similar molecular weight.Subsequently,the effect of different polymerization methods,diisocyanate,the content and molecular weight of PA6 and the composition of triblock copolymer on the mechanical properties of PUA are evaluated.The relationship among hydrogen-bond,microstructure,composition and properties of the materials were studied by DSC,FTIR and small angle X-ray scattering（SAXS）.It was found that the introduction of PA6 segment significantly improved the mechanical properties.Besides,the microphase separation structure and crystallization properties of PUA were affected by the composition of the blocks.Consequently,PUA was blended with ionic liquid（IL）and found to have good compatibility.The effect of the type and content of IL on the thermal properties,self-healing efficiency and electrical conductivity of the materials were studied.The hierarchical hydrogen-bond in the material was proved to play an important role in self-healing.The above scheme provides a new strategy for the preparation of sensing materials with excellent mechanical robustness and self-healing properties.