Research On Photoresponse Of Azobenzene Containing Polymer Vesicles With Optical Tweezer Raman Spectrum

Optical tweezers(OT) are the beam gradient optical traps where micro particles could be trapped by focusing the laser beam using a microscope objective. The gradient force generated by optical tweezers is in the pinoNewton region and is suitable to trap and manipulate microscale and nano-scale particles. In the last ten years, with the advent of new technologies like plasma, hologram, and photon crystal fiber the OT technologies develops very quickly, a lot of new OTs have been created such as surface plasmon optical tweezers(SPOT), optical trap array and optical vertex trap and so on. When combined with other technologies such as weak fluorescence detection technology, dual-beam interference technique, scanning confocal microscopy and Raman spectrum, the application areas of OT are much more expansive.Raman spectroscopy is an important detection technique in analyzing the chemical composition and structure of matter. It is able to achieve chemical fingerprint recognition and plays a unique role in chemistry, materials science, biomedicine, food hygiene, environmental monitoring and other fields. Compared with the fluorescence detection technology, its ascendancy lie in weak absorption of water from the sample, is unnecessary complex fluorescent labeling, only require a small amount of sample etc. We employ the785nm diode laser as the light source of OT and combined the Raman spectrometer to build a set of optical tweezers Raman spectrum (OTRS) system. The OTRS system can capture a single micron particles to collect Raman spectra excitation signal stably for long time. Since the particle is stably trapped in liquid remote from the surface of glass-plate to avoid interference with the surface effect of the sample cell, it is suitable in the spectrum detection of suspended particle in colloidal system.Amphiphilic block copolymers can self-assemble to form micron size aggregates or micelles. Block copolymer aggregates, like small molecule surfactants, can assume a range of different morphologies in dilute solution, including spheres, rods, vesicles, compound micelles, and others. In the past years, vesicles prepared from block copolymers have been well investigated. The interest in polymer vesicles was motivated, in part, by their potential use as micro reactors, targeted drug delivery, contrast enhanced imaging, and mimic for biological membranes. In solutions of amphiphilic molecules or polymers containing suitable chromophores, exposure to light can be used to achieve photo responses, such as precipitation, aggregation, and self-assembly. Recently, azobenzene-containing amphiphilic block polymers have received considerable attention. Upon light irradiation, azobenzene polymers can show a variety of structure and property variations triggered by the trans-cis photoisomerization of the azo chromophores, which in turn triggers mesoscopic up to macroscopic changes. Base on the big application potential of the polymer vesicle system, we utilize the OTRS system to study the photoresponsive behaviors of azobenzene vesicles. They are described in the following part.There are nine chapters in this thesis. The first chapter is the introduction of my work, include the research background status of OTRS, and the significance of studying property of azobenzene containing vesicles. The second chapter we describe the design principles, system configuration of OTRS system and its applications and instruction. And then in the next six chapters, I present six experiments about the application of OTRS system in the photo response behaviors of azobenzene containing polymer vesicle. The first experiment is I add the cross linker (Dibromopropane, DBP) to the membrane of the azobenzene polymer vesicles (PNIPAM-b-PAzPy6), and detecte the photo induced shrink-expansion of vesicle under UV light. The next experiment is three kind of polymers with different space chain length self-assemble vesicle have different morphology change under UV light irradiation. We also used another azobenzene polymer (PNIPAM-b-PAzoMO) to prepare vesicle, and it ruptures and reconstructed in to small vesicle under UV light. When two different azobenzene polymer are combined in the same solution, they formed Janus vesicles. The two part of the binary vesicle have different rate of trans-cis isomerization. We add polarize element to the OTRS system to detect the orientation of azobenzene group in the shell of vesicle under UV light. Because the mechanical property is important in the stability of the vesicle, and it is harder than the small molecular vesicles, I used the micropipette absorption (MPA) technology to detect the elastic modular of the polymer vesicles.The main innovation of this dissertation is to develop optical tweezer technology. I combined optical tweezers and Raman spectroscopy to form a versatile detection system OTRS. I use this detect system to study the photo induced transform behaviors of azobenzene containing polymer vesicles, and base on the Raman change analyzed its mechanism. The study have major implications for the exploration of new functional vesicles.