Synthesis And Characterization Of Self Assembling Polymers Using Hydrogen Bonding Or Hydrophobic Effect PDF Download

This dissertation is mainly based on the works of synthesis and characterization of self-assembling polymers using hydrogen bonding or hydrophobic interactions. Firstly, N-alkyl urea peptoid oligomer was synthesized as backbone of supramolecular polymers through three step repetition cycles with high yield. One N-alkyl urea peptoid precursor was explored to simplify the synthetic process. 4 different functional groups were converted from one precursor. Then 2-ureido-4[1H]-pyrimidinone (UPy) group which is a quadruple hydrogen bonding system was incorporated to N-alkyl urea peptoid oligomers to generate supramolecules. With the experience of UPy unit, we further explored UPy containing monomer to make organogelators. Three different monomers with different Tg values were copolymerized using reversible addition-fragmentation chain-transfer (RAFT) polymerization. Organogels were afforded in both chloroform and dichlorobenzene. Critical gelation concentration and mechanic properties of organogels were examined. Cooperating another novel monomer containing pyrene unit to the above copolymers, fluorescent organogels were achieved which were suitable for potential up-conversion applications. In addition to pyrene, anthracene is another molecule which shows great up-conversion property. A series of Poly[(9-anthrylmethyl methacrylate)-co-(methyl methacrylate)] (Poly(AnMMA-co-MMA)) with different AnMMA ratios were synthesized via RAFT polymerization, resulting in tunable inter-chromophore distances. These polymers can serve as emitters, with PtOEP as sensitizer, in triplet-triplet annihilation up-conversion (TTA-UC) systems. TTA-UC intensity of the Poly(AnMMA-co-MMA)/PtOEP mixtures displays interesting dependence on the AnMMA ratio in the polymer. Interactions between chromophores on the same polymer chain play the key role in affecting the TTA-UC intensity in these systems. It is critical to minimize intra-chain chromophore quenching in order to achieve high UC intensity. Hydrophobic effect was used to obtain a hybrid photosensitizer. By integrating amphiphilic block copolymer poly(N-isopropylacrylamide-b-styrene) (PNIPAAm-b-styrene) stabilized silver nanoparticles (Ag NPs) with hematoporphyrin (HP), HP was trapped by polystyrene block through hydrophobic effects. Hydrophilic block can increase the solubility of this photosensitizer in aqueous solution. This hybrid photosensitizer was demonstrated to enhance singlet oxygen production. Finally, a self-immolative polymer was made with a kinetically stable polymer backbone, whose chain end can respond to external stimulus by triggering a head-to-tail depolymerizaiton. Electrospining was used to fabricate nano-scale fibers which can be utilized in potential drug delivery system.