Preparation And Characterization Of Shapememory Polymer Films

Shape memory polymers(SMPs) are a new generation of functional materials which are capable of memorizing temporary shapes and then recovering to their original geometries via external stimuli. SMPs and their composite materials have been widely developed and used in various applications from the biomedicine to the out space environment, due to their unique material properties, such as large structural bearing capacity, large recoverable strain, low density, controllability of recovery behavior and low cost. Recently, the study of SMPs has greatly promoted the development of smart morphing structures and some key technologies, including micro-optics components, deployable space structures and morphing wings. However, most researches of the smart morphing structures just be based on macroscopic deformation and recovery of SMPs. With the development of smart materials and micro-and nanoscale fabrication technologies, the ability of SMPs to memorize and recover surface features at the micro-and nanoscale has recently attracted more attention. For expanding the application field of the SMPs, realizing functional diversification, in this thesis, an SMP film with controllable micro-structures is proposed and studied, which is able to applicate in tunable micro-optics components. The main works are as follows:Firstly, in consideration of the applicative requirement of SMPs, an effectiveness and potentiality sensing system was proposed for the simultaneous measurement of both temperature and strain during the whole cure process, by monitoring the change in reflected wavelength from two coupled FBG sensors that have been embedded into the SMP plate. The obtained results analyses the factors influencing the chemical reaction and rheological behavior, which could provide the foundation for preferred materials. The monitoring experimental results indirect reflect the evolutionary process of SMPs during the whole cure process. The SMP’s coefficient of thermal expansion(CTE) and glass transition temperature(Tg) also have been obtained after cured. They can provide the better support performances of the materials.Secondly, based on the characteristics of SMPs deployable structure during their service time, we consider first the simple deformation and displacement of an SMP sample in pure bending condition. For relatively large size of the SMP plate, a simple and practical scheme for shape recovery deformation monitoring of SMP deployable structure model has been demonstrated based on the measurement of FBG vector sensors attached or embedded in the SMP structure. For relatively small size of the SMP film, some micro groove diffraction grating structures were replicated on the SMP film’s surface. When the SMP film was bent at different angles, the diffraction patterns distributions changed accordingly due to the grating’s period changed, indicating the bent direction and angles. The SMP sample under various static bending angles and dynamic shape recovery deformation process were investigated, which is very important to ensure their smart structures’ safety in operation and promote development of SMP films’ applications in flexible bending deployable structures.Thirdly, in accordance with application requirements of the tunable micro-optic components, two types of SMP films with controllable optical properties are proposed based on the ability of SMPs to memorize and recover surface features at the micro- and nanoscale. Some SMP films with controllable thickness and pre-programmable micro/nanoscale structures are prepared using the typical spin coat wafer processing or pouring technologies, which exhibit colorful diffraction by illuminated white light. Fabrication based on this approach is remarkable for its simplicity and for its fidelity in transferring the structure from the template to the replica surface. On the other hand, some SMP films with temporary pre-programmable micro/nanoscale structures are obtained by the hot embossing technology, which exhibit excellent transparent in the initial state. The surface topography, static and dynamic mechanical properties and shape memory effect of the SMP films are discussed by a series of testing methods.Finally, the film’s active compressive deformation could be monitoring by the film’s transmission diffraction patterns’ power changed. Using micro-groove grating patterns on the SMP films, the diffraction efficiency measurements is stated by investigating the optical property response to the micro groove grating patterns changed during the whole thermal activated recovery process. Such a structural film is easily prepared and has the potential for tuning and switching the optical power as an optical beam power splitter, and widely applied in the micro-optic, physics and nanotechnology fields. Three types of the optical beam film splitter were designed, fabricated and investigated based on the mechanical properties, shape memory and optical diffraction effect. The splitting beam effect of SMP film splitters were demonstrated: when an incident light beam goes through a pre-designed 1×N splitter, it splits into multi-beams; when multiple light beams go through a M×1 splitter, they merged single beam; when two-dimensional spot-array go through the M × N splitter, they switch to one-dimensional spot-array. Through pre-designing complex Si template, an SMP film with nanoscale structures was proposed, which could switch the virtual computer keyboard with laser impressions on any table or other surface.