Design Synthesis And Application Of Photoresponsive Polysiloxane Semiconductor Materials

Polysiloxane semiconductor materials have unique advantages in physical and electronic properties and can be obtained by simple molecular mod fication,design and synthesis.Polysiloxane has excellent solubility,film-forming property,non-selectivity to various substrates,light resistance,thermal and chemical corrosion resistance,as well as high dielectric constant and electron inertia.Therefore,Compared with other semiconductor materials,polysiloxane semiconductor materials,which are made by introducing macromolecular groups with excellent photoelectric properties into siloxane,have obvious advantages in polymer solubility,intermolecular interaction,physical and thermomechanical properties.Due to the stimulation of external light signals,the molecular structure and properties of photoresponsive groups can be changed reversibly.At the same time,light signals have the advantages of cleanness,high efficiency,safety and remote control.Therefore,it is of great significance to design and synthesize photoresponsive polysiloxane semiconductor materials.In this paper,we focus on the application of this material in organic storage and second-order nonlinear optics.Therefore,the main contents of this paper are as follows:In the first chapter,the research progress of polymers with coumarin and azobenzene as photoresponsive groups and their applications in electrical storage devices and second-order nonlinear optical materials are reviewed.The synthesis method,photophysical chemical properties and the application of polysiloxane materials are also introduced.After that,the research background,concept,type,storage mechanism,design ideas and principles of functional layer polymer materials for electrical memory,as well as common donor materials and acceptor materials are introduced.The selection of functional groups and the design of effective combinations between them are the key to the electrical memory properties of materials.In view of the relationship between the structure and the properties of the material,the research progress of the second order nonlinear optical material and design ideas are briefly summarized.Finally,the purpose,significance and main contents of this paper are discussed.In the second chapter,perylene imides with large conjugated rigid electron-deficient structures and electron donor thiophene were selected as donors and acceptors respectively,designed and synthesized main chain copolysiloxanes PBIClSi-alt-PTSi.After that,we focused on the memory performance of PBIClSi-alt-PTSi as active functional layer of ITO/PBIClSi-alt-PTSi/Au,the results showed that the device had WORM memory characteristics with lower turn-on voltage(1 V),higher switching current ratio(6×103)and response speed at nanoscale(90 ns).For the first time,current sensing atomic force microscopy(CSAFM)was introduced to prove the memory mechanism.As the device from OFF state to ON state,the topological structure of PBIClSi-ail-PTSi films changed obviously.Therefore,we consider that the memory mechanism of the device is conformation transformation and charge transfer.The third chapter,we researched the bistable electric memory materials deeply and proposed the concept of reversible and photo-control organic electric memory device.So,designed and synthesized poly(vinylcoumarinsiloxane)(PCoumSi)with light response groups-coumarin as the side group.After that,we prepared ITO/polymer/Au memory device with two polymers as the functional layer respectively.The results of J-V test showed that the device ITO/PCoumSi/Au has no storage behavior,while the device ITO/PDCoumSi/Au has WORM memory characteristics with lower turn-on voltage(1.05 V),higher switching current ratio(2×103).By appling proper light and bias,the devices had optical control and reversible electrical memory behaviors.The fourth chapter,we choose azobenzene as photoresponsive group,designed and synthesized based on the nitro azobenzene as side group,main chain siloxane copolymer of side chain type poly(vinylpnitroazobenzene)siloxane(PVAzoSiNO2).After that,ITO/PVAzoSiNO2/Au sandwich devices were fabricated by using the PVAzoSiNO2 as the functional layer of memory devices,the test and analysis results showed that the device has a Flash memory features.At the same time,the device has low voltage(-1.25 V)and high current switch ON/OFF ratio(4×103).The trans structure is transformed into cis structure by reverse irradiation.It is found that the device still havs memory performance.So,memory performance of the polymer film PVAzoSiNO2 is not affected by UV light.And the properties of memory are not caused by isomerization.The results of flexible device showed that the device still have a good memory features and stability of flexible.The results have guiding significance for the development of flexible devices.In fifth chapter,the side chain(PSAzoSi),main chain(PMAzoSi)and main-side alternating(PAltAzoSi)copolymers with azobenzene as reactive functional groups are designed and synthesized.After that,we tested the second-order nonlinear optical properties of three polymers,the results showed that the polymer of PMAzoSi has the best second order nonlinear performance with high degree of conjugation.