Self-Assembly Behaviors Of Azobenzene And Cyclodextrin Supramolecular Systems

Supramolecular self-assemblies are organized assemblies formed by intermolecular forces (such as hydrogen bond, electrostatic force and Van der Waals'force). They are easily response to stimuli. Based on typical light sensitive azobenzene/cyclodextrin supramolecular assemblies, the manuscript studied on the preparation of the azobenzene/yclodextrin modified polymers, the formation of the aggregates by the polymers in aqueous solutions, the change of the morphology of aggregates by environment and the functionality of the azobenzene/yclodextrin modified materials.The basic of the study was modification of cyclodextrin (CD) and azobenzene (Azo). The modified CD and Azo could be introduced to polymers at different position, such as end groups, side groups and crosslinking points. The Azo/CD superamolecular assemblies could match molecules, tune the mophology of assemblies, tune the sol-gel transformation, and achieve the functionalities, such as molecular absorption and drug delivery. The manuscript included the following four parts in details:(1) The light controlled matching of Azo and CD was studied. The mCPOSS was synthesized by coupling of CD and POSS via click chemistry and the PPA was syntheiszed by ATRP and end group modification. mCPOSS formed nanospheres in aqueous solutions and the nanospheres induced PPA to form micelles. The mophologies of the aggregates formed by mCPOSS and PPA were tuned by ratio, light and pH. They formed complex micelles when the ratio of mCPOSS:PPA is 1: 1 and they formed spherical micelles when the ratio of mCPOSS:PPA is 1:5. The aggregates were disociated under UV light and restored to micelles under visible light. The size of the micelles is big at pH=3 and small at pH=9.(2) The self-assembly behaviar of the polymers prepared by new Azo monomer in aqueous solutions was studied. The Azo monmer AZOTEGMA, which was composed of hydrophilic TEG, Azo group and methacrylate group, was synthesised. The random polymer PAZOEG was prepared via ATRP and the polymer was temperature responsive. The sol-gel transformation of PAZOEG/?-CD supramolecular assemblies was studied by tuning CD to Azo ratio, temperature and light irradiation. The state of the assemblies changed from sol to gel at 25? when the mole amount of ?-CD was three times larger than that of Azo. In addition, the gelation needed more a-CD when the temperature was higher than 25?. UV light irradiation made the gelation easier and the change was reversible.(3) The preparation of hydrogels with CD as crosslinkers was studied. The CD-based polyurethane hydrogels were prepared using CD, PEG and HDI. The relationship between the content of each component and the swelling and viscoelasticity properties of the hydrogels was studied. The results showed that the water absorption ratio, water content and viscosity of the hydrogel increased and the elasticity of the hydrogel decreased when the content of PEG or CD increased. The water absorption ratio, water content and viscosity of the hydrogel decreased and the elasticity of the hydrogel increased when the content of HDI increased. The relationship between the content of each component and the absorption properties of the hydrogels was studied. The hydrogel absorbed the methyl orange by both physical absorption and supramolecular absorption.(4) The light-responsive Azo/CD hydrogels were studied. The gel networks were prepared by isocyanate end-capped PEG, CD, DSO and Azo. The hydrogels had good elasticities at high water content (above 90%). The swelling, mechanical and viscoelastical properties of the hydrogels were tunable by reductant and UV light. The hydrogels had low cytotoxicity when using for short time. The hydrogels could load and release drugs. UV light irradiation promoted drug load process and reductant promoted drug release process.