Synthesis And Self-assembly Of Rod-Coil Multiblock Poly (PPV-b-PEG) And Their Bioimaging Application

Synthesis and self-assembly of rod-coil block conjugated polymers is significant not only in academic research, but also has a very good application prospect. They self-assemble into micelles which scale is usually about10to100nm and easy functionalization, have potential applications in cell imaging, drug transport, clinical diagnosis and so on. Aggregation and microphase separation of rod-coil block copolymers have yielded a number of nanoscale morphologies, such as lamellar, spherical, cylindrical, vesicular, and microporous structures. For multiblock copolymer, such morphologies are driven not only by the solvent selectivity but also influenced by the solution concentration. This property of multiblock copolymers is just similar with cyclic copolymer but different with linear diblock and triblock copolymers. In this paper, novel alternant amphiphilic poly [1,4-bis(phenylenevinylene)-2,5-bis(alkyloxy)benzene-alt-poly(ethy lene oxide)](PPV-b-PEG) were synthesized. Also the morphology, and photophysical properties of PPV-b-PEG and the application in cell imaging were studied and discussed.(1) A novel class of multi-block copolymers were designed and synthesized based on Wittig coupling reaction. Oligonucleotide polyphenylene vinylene (OPV) as the rigid skeleton existing in the kind of rod-coil block copolymers, while the PEG chain is a flexible block. They can dissolve in common organic solvents but insoluble in water. In selective solvent THF/water, they self-assemble to form micelles of different morphologies and scale, the main driving forces of the self-assembly are hydrophobic interactions and π-π stacking interactions, and the mainly morphology is "core-corona" structure. The spectroscopic and morphology properties of these micelles were characterized by UV-fluorescence spectra, transmission electron microscopy (TEM), scanning electron microscopy (SEM), dynamic light scattering (DLS).(2) A novel class of amphiphilic PPV-b-PEG were designed and synthesized. A longer coil length was introduced to achieve its water-soluble. TEM images showed that the molecular self-assembly morphologies changed with the increase of the solution concentrations. A spherical shape with diameters around40-50nm were observed in dilute solution, while some aggregates formed in concentrated ones. This material can be used for cell imaging and confocal fluorescence microscopy(SCLM) indicates internalization of the material by the HepG-2cells. MTT method proves it low cytotoxicity.(3) A water-soluble fluorescent nanoparticles was prepared by a PPV-b-PEG(P65) which insoluble in water. This P65nanopaticles can be sable in water for a long time, and it shows a spherical shape with diameters around20-30nm. This fluorescent nanoparticles were incubated with HepG-2cells for4h, then the cytoplasm shows bright blue fluorescence.