Semiconducting Diblock Copolymers Chemistry 765 Peter Dorff

Diblock Copolymers Commercial applications: thermoplastics Polymers as Semiconductors?

Why Semiconducting polymers? Combines properties of metals into polymers  flexibility & processing Range of conductivities Electroluminescence: LEDs Very important! = $$$$$$

Semiconducting Polymers Initial work in 1968 by Dall’Olio et al. 2 synthesis of polypyrrole on Pt electrode electrical conductivities of  = 8 Ω -1 cm -1 Diaz, A et al. in 1979 synthesized stable, manageable polymeric films electrical conductivities of  = 100 Ω -1 cm -1 Skotheim, T.A, Handbook of Conducting polymers (New York and Basel, New York, 1986)

Doping of Polymer Popular Method developed in 1970s “doping”with e - donor & acceptor permits charge transfer iodine polyacetylenes (  = 360 Ω -1 cm -1 ) (CH) x + D + + A -  (CH) x + A - + D (CH) x + D + + A -  D + (CH) - x + A

Photovoltaic Cell Inexpensive renewable energy resource Benefit of Polymer PV cells: Low cost fabrication, durable & flexible Reaction:

Poly(p-phenylenevinylene) Excellent charge transfer, however: Discontinuous  ionization potential Photoexcitable at  450 nm Present use in LEDs Skotheim, T.A, Handbook of Conducting polymers (New York and Basel, New York, 1986)

Evolution of Polymer PV cells Research by Sariciftci, N.S et al. in 1992 Dope PPV with C 60 & spin cast into film C 60 accepts 6 e - Sariciftci, N. S et al. ibid. 62, 585 (1992)

Luminescent Studies PPV’s photoluminescent properties disappear  charge transfer!

Progression Research by Yu, G et al in 1995: 1/3 energy lost via luminescence Charge transfer occurs at D-A interface  Soluble C 60 derivatives >5.5% energy conversion Yu, G., Gao, J., Hummelen, J, Wudl, A, Heeger, J; Science, 270, (1995) 1789

A New Approach Stalmach, U et al. & their goal structured morphology »microphase separation of blocks »self-assembled monolayers poly(PPV)-block-poly(___-C 60 ) Stalmach, U et al. J. Am. Chem Soc., 2000, 122, 5464 Stupp, S. et al., Science, 1997, 276, 384

Objective

Synthesis Step 1: Polymerization of PPV Monodispersed MW End Functional Group

Synthesis Step 2: Preparation of TEMPO linker

Synthesis Step 3: Attachment of TEMPO Facilitates diblock formation between very different groups

Synthesis Step 4. Synthesis of a Diblock copolymer NMRP leads to monodispersed block Random styrene / CMS block (1:1 ratio)

Synthesis Step 5. Functionalize with C 60

Conclusions Successful synthesis of rod-coil block copolymers Self-assembly into honeycomb monolayers Quenching of luminescence with excitation Future work in applying polymer to prototype photovoltaic cell