Studies On Functional Polymeric Materials Which Respond To Ultrasound And Enhance Adhesion

Functional polymers material has spread widely in reaserach and in real life.Ultrasound is a useful tool for material synthesis and an effective method of studying polymer mechanochemistry.The interface modification of flexible electronics is also a wide-researched topic. It is very important to improve stability by solving the dismatch between the flexbile substrates and the mounted electronics above.I am honored to conduct reseaches in these fileds and have done several work during my PhD career. This thesis mainly focuses on:1. We present a convenient sonochemical approach for the synthesis of highly photoluminescent carbon nanodots (CDs). CDs were synthesized via pyrolysis of carbon precursors inside implosively collapsing bubbles. We further demonstrate that these CDs can be used for in vitro bioimaging. Sonochemistry can be applied to synthesize nanostructured materials from either volatile or nonvolatile precursors and can be categorized as primary sonochemistry and secondary sonochemistry.Primary sonochemistry occurs inside collapsing bubbles and usually involves volatile species. Secondary sonochemistry is a solution-phase chemistry and sonochemical products may arise from chemically active species (e.g, radicals from thermal decomposition of vapour molecules) generated inside bubbles which diffuse into the solution to initiate chemical reactions. Liquid nanodroplets containing nonvolatile species can be injected into the collapsing bubbles by capillary wave action, microjetting, or bubble coalescence because of the significant deformation during bubble collapse in the dense cloud of cavitating bubbles. Once the nanodroplets enter the hot interior of a collapsing bubble, the solvent evaporates and chemical reactions in the gas phase analogous to the processes in flame pyrolysis occur. Therefore, nonvolatile species can be excited and pyrolyzed inside the collapsing bubbles. Crossing the line between primary and secondary sonochemistry,that is, the application of collapsing bubbles as microreactors to pyrolyze nonvolatile precursors has not been reported yet.2. Polymer mechanochemistry provides a unique approach to promote or bias chemical reactions that may not be attainable using heat- or light-induced activation methods and thus could lead to fabricate novel materials. We designed and synthesized a new mechanophore based on platinum-acetylide complex incorporated into a polymer backbone. Ultrasound can produce a large solvated tensile stress in the polymer chain. The diluted polymer solution can experience the solvodynamic shear force generated by the solvodynamic solvate (ie, bubble nucleation, growth and collapse) near the collapse of the polymer chain at the end of the polymer chain than the distal end. These velocity gradients cause the polymer backbone to strain and produce tensile stresses near the midpoint of the polymer chain. The mechanically induced chain scission was demonstrated to be able to release catalytically active platinum species which could catalyze the olefin hydrosilylation process.This work further exemplifies the utilization of organometallic complexes in design and synthesis of latent catalysts for mechanocatalysis and development of self-healing materials based on silicone polymers.3. Flexible conductive electrodes are key elements in flexible and wearable electronics. However, current electrodes typically exhibit poor durability or scratch resistance, thereby has been one of the biggest limitations for their wider applications in industry. Inspired by the strong adhesion properties of mussel, an interface coating based on dopamine polymer could be introduced between conductive patterns (metal/non-metal) and the underlying flexible substrates to address this problem. The unique dopamine-based polymer coating can endow various flexible substrates including polyimide (PI), polydimethylsiloxane (PDMS),polyethylene terephthalate (PET), fabric with intense adhesion and superior mechanical performance. Furthermore, robust flexible conductive circuits based on polymer coating to power a LED bulb after 1000 cycles of bending or scratch were demonstrated. The polymer coating makes a great contribution for conductive patterns strongly adhering to the substrate and withstanding numbers of bending and scratches, which proved to be an ideal platform for robust flexible electronics.