Polydiacetylene-Based Supramolecular Systems: Synthesis, Characterization, And Applications

Official URL: https://risc01.sabanciuniv.edu/record=b3205844

Polydiacetylenes (PDAs) are useful conjugated polymers for studying supramolecular interactions and sensing applications. External stimuli disrupt the planar conjugated backbone of PDAs, resulting in a blue-to-red color transition and activated fluorescent signal. Modifying diacetylene monomers improved resistance to external triggers through enhanced head group interactions or facilitated the detection of specific molecules, thereby increasing sensitivity. This thesis investigates the covalent attachment of bulky mBzA (m-amino benzoic acid) and linear DETA (diethylenetriamine) molecules to the carboxylic head group of two DA monomers, namely PCDA and TCDA, with different alkyl tail lengths. Their responses were evaluated under various triggers using selfassembled PDA vesicles, enabling three-dimensional exposure to the stimuli. Testing mBzA-substituted PDA vesicles under basic conditions and varying photopolymerization duration revealed decreased sensitivity to high pH with prolonged UV irradiation and allowed reversibility in mBzA-functionalized vesicles. Furthermore, DETAfunctionalized PDA with a shorter alkyl tail initially produced purple-colored vesicles. The effect of the initial intermediate phase was assessed by comparing monocarboxylic and longer alkyl tail monomers under various external triggers, including acid and alcohol. The intermediate phase promoted the purple-to-red color transition despite being thermodynamically more stable than the blue phase. However, exposure to liquid ethanol and acetic acid vapor resulted in the presence of a small fraction of blue phase in poly(TCDA-DETA) vesicles but not in poly(PCDA-DETA) vesicles, indicating the significant role of inter- and intra-chain interactions in strain release through chain distortion and realignment. Electrospun fibers of DETA-functionalized andmonocarboxylic diacetylenes were employed for solid-phase sensor applications. Food spoilage sources such as wine, milk, and chicken were used. The results revealed that amine-substituted PDA/PEO fibers were affected by the spoilage of those products. However, more in-depth analysis is needed to optimize their response to the actual spoilage of the food products.