Preparation And Field-Effect Performance Of Poly(3-hexylthiophene) Block Copolymers

Poly-3-hexylthiophene(P3HT)and its derivatives have been widely used in electronic devices such as organic thin film transistors,organic photovoltaic cells and so on,because of their simple synthesis process,excellent electrical properties and good environmental stability.However,with the development of modern electronic devices,higher requirements are placed on semiconductor materials.The ductility is one of the research focus,but P3HT does not have this feature.According to the principle of thermoplastic elastomer SBS,a hard-soft-hard tri-block polymer with hard segments of P3HT was designed,it would be expected to improve the mechanical properties of P3HT,but the synthesis is difficult,and there are few reports in this field.The experimental content and research results of this paper are as follows:(1)A series of tri-block copolymers poly(3-hexylthiophene)-b-polyhexadecyloxy-allene-b-poly(3-hexylthiop-hene)(P3HT-b-PHA-b-P3HT)was synthesized under GRIM mechanism,in one pot via sequential monomer addition with Ni(dppp)C12 as a single catalyst.The structure of copolymer is monitored and characterized by nuclear magnetic resonance spectroscopy,volume exclusion chromatography,and Fourier infrared spectroscopy.The results showed that the reaction process was active/controllable,and the molecular weight distribution of the block polymers was small,all less than 1.5.The polymerization process is simple and the product is easy to purify,simplifying the steps of synthesizing the P3HT block copolymer.(2)Bottom-gate top-contact organic thin-film transistors device with these polymers as the active layer was prepared,and the effects of the preparation process,the structure of the block polymer,the molecular weight,and the block ratio on the performance of the organic thin-film transistor device were studied.The results of device performance studies show that high molecular weight P3HT and high content of P3HT contribute to increase the mobility of block polymers,and the device’s maximum mobility reaches 4.54×10-2 cm2·V-1·S-1.The micromorphology of the active layer film was further studied.The results show that high molecular weight P3HT and high content of P3HT are favorable for obtaining a longer and wider nanofiber structure,which will facilitate carrier transport.(3)The field-effect properties and micro-morphology changes of the three materials P3HT,P3HT-b-PHA,and P3HT-b-PHA-b-P3HT on force are preliminary studied.The results show that the field-effect mobility of the P3HT-b-PHA-b-P3HT triblock polymer decreases from 6.01×10-3 cm2· V-1· s-1 to 4.44×10-5 cm2·V-1·S-1 when the tensile strain increases from 0%to 100%,it is obviously better than P3HT and P3HT-b-PHA.The microstructure study showed that the mechanical properties of the P3HT-b-PHA-b-P3HT tri-block polymer are superior to that of the P3HT and P3HT-b-PHA diblock materials,and P3HT-b-PHA-b-P3HT triblock polymer still have higher field-effect mobility when tensile deformations up to 100%,the number of cracks is less.