Helical Conformation Switching Of Stimuli-responsive Dendronized Poly(phenylacetylene)s Through Supramolecular Interactions

As a typical class of dynamic helical polymers and due to unique structural characteristics of alternating single and double bonds along the backbone and easy modify of pendant groups,poly(phenylacetylene)s has received great interests in recent years.Their helical conformation and elongation can be manipulated by the action of external stimuli such as chiral additives,polarity changes or metal ions.Thus,poly(phenylacetylene)s materials can be widely used in chiral sensors,chiroptical switches,chiral catalysts and other applications.In the present thesis,we report on the synthesis of a novel type of dendronized poly(phenylacetylene)s which carry both oligoethylene glycols(OEGs)-based dendron and?-cyclodextrin as pendants.Their chemical structure,helical comformation and thermoresponsiveness were characterized with ~1H NMR,UV-vis and circular dichroism spectroscopy,and more importantly,helical conformation switching of poly(phenylacetylene)s through temperature and supramolecular interactions were focused.The results confirmed that OEG-dendrons ensure excellent thermoresponsiveness,while?-cyclodextrin introduced to backbone induces tunable helical conformation.This thesis includes the following aspects:(1)poly(phenylacetylene)s carrying?-cyclodextrins and dendritic OEG pendants were efficiently synthesized through both dynamic Schiff-base linkage and macromonomer copolymerization.All these polymers dissolve well in water at room temperature,which show unprecedented thermoresponsiveness with fast phase transitions and low hysteresis at elevated temperature.(2)Helical conformation of poly(phenylacetylene)s bearing?-cyclodextrin through Schiff-base dynamic covalent linake is reversible,which can be switched by pH conditions and temperature variation,as well as supramolecular interactions with various guests.(3)Copolymer carrying chiral?-cyclodextrins through copolymerization show preferred one-handed helical conformation.Apart from temperature,helical conformation of these polymers also switched by interaction with guests,which can be well swiched through supramolecular interactions.Moreover,helical conformation can be also swiched by solvent such as water and even within buffer solutions.In summary,dendronized poly(phenylacetylene)s carrying?-cyclodextrins and dendritic OEG pendants were desighed and synthesized,which possess excellent stimuli-responsive behavior and dynamic switchable conformation.Helical conformation of these polymers can be switched by temperature,pH and various guests,and these processes can be realized in aqueous solutions,thus,present research provides a new way for functionalization and practical applications of poly(phenyacetylene)derivatives,and demonstrates poly(phenylacetylene)s are no longer limited to organic sovents.At the same time,these polymers have potential applications in the field of chiral separation materials and smart materials.