The Fabrication And Crystallization Study Of Functional Polymer PHB And P3HT Ultrathin Film

With the development of research,more and more attention has been paid to the study of polymer ultrathin films.The crystallization of polymer ultrathin films with regular chemical structure is one of the most remarkable phenomena in condensed matter physics.In addition,ultra-thin polymer films have important technical value in many fields,from coatings to organic electronic devices.Considering that the microstructure of macromolecules in the restricted geometry plays an important role in the final macroscopic properties of ultrathin films,it is crucial to understand the influence of the crystallization mechanism of ultrathin films on the structure of polymer films.In this paper,classical crystalline polymers Poly(3-hydroxybutyrate)(PHB)and semicrystallized polymers Poly(trihexylthiophene)and Poly(3-hexylthiophene)(P3HT)were selected as the research objects.Firstly,PHB and P3 HT ultrathin films with different thickness and PHB/ PVPH blends were successfully prepared by spin coating method.In addition,nanoimprint of P3 HT thin film was carried out by hot imprint method,and the patterned nanolines were successfully copied.On this basis,the P3 HT double-layer film with PVPH as the substrate was successfully constructed,and the patterned nanowires were also obtained by hot imprinting method,which successfully achieved the complete limitation of the upper P3 HT ultra-thin film.Secondly,the crystallization behavior and morphology of PHB ultrathin film were systematically studied by atomic force microscope,polarizing microscope,scanning electron microscope and X-ray diffractometer,and the thickness of PHB ultrathin film below 100 nm was measured.The results show that with the increase of melting temperature,the morphology of PHB ultra-thin film crystals generally changes from "cluster" crystal state to "bundle" crystal state,and finally changes to "spherulite" morphology.The diffraction signal of PHB films with different thickness appears at2θ=13.4° and 2=27.2.When the thickness of PHB films is reduced to ～ 20 nm,the crystallization ability of PHB films is the weakest and no crystallization signal appears.When amorphous polymer PVPH is added,the crystallization behavior of PHB/ PVPH(8/2)blends has a great change.Only when the thickness of the blend ultrathin film is relatively high and the melting temperature is also high,can the surface of the film appear classical spherulite morphology.When the thickness or melting temperature is reduced,the spherulite morphology does not appear,and when the thickness is reduced to 15 nm,it is difficult to see the ordered state on the surface of the blend film.The results of X-ray diffractometer show that the diffraction signal of ～ 75 nm thickness co-supermixed films appears at 2θ=13.4°,but the diffraction signal peak of ～ 45 nm and ～ 15 nm thickness does not appear,which is caused by the limited crystallization of PHB.Furthermore,the morphology and crystallization properties of the original P3 HT ultrathin films and the patterned P3 HT nanocrystalline films were systematically characterized by atomic force microscopy(AFM),scanning electron microscopy(SEM)and X-ray diffraction.The results show that there is no obvious crystallization peak in the original P3HT(～ 80 nm)films without nano-imprint,which indicates that the crystallization intensity of the original P3 HT films at lower thickness is low.The patterned P3HT(～ 80 nm)thin film shows a distinct diffraction signal peak at2θ=5.4.This is because the application of nanoimprint technology makes the crystallization of the film stronger.The crystallization peak of ～ 160 nm thick P3 HT ultrathin film after nano-imprint was the highest,and the strength was the highest,which was due to the joint result of the thickness of the film and the nano-imprint.Finally,the PVPH /P3 HT double-layer ultrathin films and the patterned nanolines were characterized by atomic force microscopy and scanning electron microscopy.The results show that the patterned PVPH /P3 HT double-layer ultrathin film nanolines match the template perfectly.The crystallization behavior of patterned polymer thin films under confinement conditions was characterized in detail by using GIWAXD and area detector.The results show that the orientations of original films,unpatterned films and nanometer grating films are generally unidirectional.But the diffraction peak of the diffraction signal(100)plane has obvious light intensity transition.Compared with the unpatterned polymer films,the diffraction profile strength of the nanograting films increases obviously.Under partial constraints,the molecular orientation of P3 HT nanometer grating thin films is one-sided,and there is no other molecular orientation.The crystallization ability of P3 HT nanometer grating films under partial confinement is smaller than that under complete confinement.Therefore,it can be further inferred that complete confinement plays an important role in enhancing the crystallization of P3 HT polymer molecules during the preparation of nanograting structures based on nanoimprinted lithography.