Electrically Active Organic-Inorganic

             Molecular/Polymeric Hybrids             

                   Bringing vastly different structural and functional units together through covalent bonds is one of the most attractive approaches to obtain multifunctional materials or materials with unexpected synergistic properties.  In the past few years, we have discovered novel chemistry and developed rational strategies for the synthesis of covalently bonded hybrids based on polyoxometalate (POM) clusters and organic p-conjugated systems.  POMs are a unique class of metal-oxygen clusters, whose molecular identity is maintained both in the solid state and in solutions.  Coupled with interesting electrical and optical properties such as electrochromism, photochromism, conductivity, and redox activities, POMs are considered electrically active molecular materials.  On the other hand, conjugated molecules and polymers are electrically active organic materials.  Such materials have drawn tremendous attention in the last decade and have found numerous exciting applications in, for example, light emitting diodes, field-effect transistors, photovoltaic cells, and solid-state lasers.  The molecular nature of these two types of materials offers the opportunity to generate covalently bonded molecular hybrids where the interplay between cluster d-electrons and organic delocalized p-electrons can be explored at the molecular level.  The unprecedented hybrids are expected to possess interesting electrical/optical properties which may find applications in many areas. 

              Here are some of our focuses for this project:

 Develop new chemistry for the functionalization of POM clusters.

 

  Prepare POM-containing metal-coordinated hybrids and networks

 

Develop hybrids with unique crystal packing and NLO properties

Hybrid conjugated polymers

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Unsymmetrical conjugated

             dendrimers as novel materials.                                                

Dendrimers have been extensively studied in the last decade not only because of their aesthetically appealing molecular architectures, but also because of their great potential for practical applications.  A wide variety of dendrimers with different cores, branching units, and end groups have been synthesized.  However, almost all the dendrimers studied so far have symmetrical structures: branches in the same generation are equivalent.  In the past few years, we have been exploring dendrimers with unsymmetrical branching schemes.  Such tree-like dendrimers show excellent light-harvesting properties which may find applications in solar cells, LEDs, two-photo absorbing materials, and sensors.

Our focuses in functional dendrimers include:

Syntheses of dendrons/dendrimers with un-symmetrical    branching (chemistry & synthetic strategies)

  Dendrimer-based sensors

 Dendrimers for nonlinear optics

Aqueous soluble conjugated dendrimers and materials

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Aqueous soluble conjugated polymers and their applications

Water-soluble conjugated polymers (WSCPs) have drawn increasing attention recently as they not only allow environment-friendly processing of such polymers into the many well-demonstrated electronic devices such as light emitting diodes, photovoltaic cells, and field effect transistors, but also represent novel platforms for unique applications such as chemical, ionic and biological sensors, as well as light-emitting electrochemical cells.  The aqueous solubility of such polymers is usually achieved by attaching ionic pendants such as  anionic sulphonates, carboxylates, and phosphonates and cationic quaternary ammonium salts to the backbone.  Among all WSCPs, PPVs with sulfonate pendants are the ones most extensively studied.  In particular, they have been shown to possess extremely high photoluminescence quenching efficiencies to cationic electron acceptors such as methyl viologen (MV²⁺), and this property has been applied to build highly sensitive biosensors.  Research, however, has so far focused on only one PPV polymer, poly(2,5-methoxy-propyloxysulfonatephenylene vinylene) (MPS-PPV).  To allow a systematic study of water soluble PPVs (WS-PPVs) with sulphonate pendants, we have prepared a series of WS-PPVs.  Their optical properties are being studied.   

              The applications of WS-PPVs in chemical/biological sensors are being explored.

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Other on-going projects at the exploratory stage

Cyclodextrin-containing macromolecules and their applications

Helical Conjugated polymers

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