Chiral Aggregation Of TPPS In Confined Space

Chirality is one kind of fantastic phenomenon in the nature. The research on chirality is of great importance in life, pharmacology, polymer and material science. Supramolecular structures with chirality has attracted extensive interests of researchers due to the potential applications. Meanwhile, soft confined space is widely used for preparation of nano-materials. Supramolecular aggregation in confined space may give new perspective to supramolecular chemistry. In this dissertation,5,10,15,20-tetrakis-(4-sulfonatophenyl)-porphyrin (TPPS) is used as model compound. Chiral aggregation of TPPS in different kinds of confined space are studied. The regulation on the path and progress of the chiral aggregation of TPPS by cationic block copolymer are investigated. Furthermore, TPPS is dispersed into PMMA matrix to explore the practical applications.In acidic aqueous, protonated TPPS forms electrostatic cross-linked core with poly(ethylene glycol)-block-poly(L-lysine)(PEG-b-PLL) and is stablized with the external PEG block. The core-shell micelle serves as polymeric confined space in which the asymmetric alignment shows two kinds of induced optical activity, called as "wrapping mode" and "pending mode" by inverting the charging sequence of the two components. These asymmetric alignments can be displaced by poly(sodium-p-styrenesulfonate)(PSS) from the chiral PLL template through the competitive electrostatic complexation. The template-removed TPPS arrays preserve their induced optical activity and serve as primary subunits for further construction of TPPS aggregates. It is observed that the morphology of the aggregates is strongly dependent upon the primary asymmetric supramolecular arrangement of TPPS. The rod-like nanostructure with length about200nm is composed of the primary linear array that shows opposite Cotton effects between J-and H-bands. On the contrary, the linear array with same Cotton effects at J-and H-bands can aggregate into micron-sized fibrils or precipitation as usually been observed.Confined space produced by commercial surfactant is used to control the aggregation of TPPS.However, only the controllable growth in the earlier stage could be performed due to the poor dynamic stability of microemulsion and unstability of cofined aggregates. Additionally, the practical application is restricted due to the unstability of confined aggreagtes after escaping to the bulk. Poly(ethylene glycol)-block-poly(4-vinylpyridine)(PEG-b-P4VP), with a poly-cationic building block, forms electrostatic complexes with the J-type chiral pre-aggregates of TPPS in the water inner-phase of the TX-100reverse microemulsion at pH1.0using L-Tryptophan (Trp) as the chiral source. The complexation with PEG45-b-P4VP6offers extra encapsulation and prevents these chiral pre-aggregates from contacting with each other during the percolation of the droplets, so as to stabilize the CD intensity and the size of the complexes. After breaking the microemulsion, the PEG45-b-P4VP6/TPPS aggregates are also prevented from further clustering at optimized ratio of [polymer]/[TPPS], so these complex aggregates disperses in acetone with spherical morphology and well maintain their size and chiral signal for further storing.Supramolecular chirality of TPPS aggregates combines various photochemical/photophysical properties and chirality. Polymerizable surfactant is used to disperse water-soluble TPPS into the polymerizable oil phase, methyl methacrylate (MMA), to produce polymerizable reverse microemulsion serves as lockable confined space. UV-initiated polymerization leads to TPPS/PMMA nano-composite material. The photochemical/photophysical properties of TPPS, such as UV-absorption, fluorescence emission and reversal saturated absorption (RSA) due to multi-photon absorption, are retained in PMMA. Moreover, D/L-tartaric acid, D/L-Tryptophan and L-Lysine are used as inductor to produce chiral TPPS/PMMA nano-composite. The fixed microsturcture of microemulsion protects the aggregates from further aggregation. The nano-composite shows circular dichroism corresponding to the absorption band of TPPS. The chiral aggregation of TPPS in TPPS/PMMA nano-composite material leads to the transition from RSA to saturated absorption (SA), which would offer experimental supports to the design of optical device.