Final Report Summary - XLIM (Well-defined Conjugated Block Copolymer Nanofibers and their Applications in Photovoltaic Devices)
The goals of the proposal were to synthesize poly(3-hexyl thiophene) (P3HT)-containing block copolymers and to investigate their self-assembly into functional materials. These polymers were successfully prepared via sequential Grignard metathesis, and were found to readily self-assemble into nanoscale objects in selective solvents for the coil block. This allowed us to prepare cylinders with uniform length and structure. These materials were then used to prepare complex, functional nanoscale objects by low-cost solution processing. Importantly, these cylinders are demonstrated to be electroconductive and can be applied into electronic devices.
Highlights include:
1) The synthesis of all conjugated regioregular P3HT-block-regiosymmetric P3HT. This is the first example of semiconductive block copolymers with blocks of different regioregularities. The different regioregularities impart different properties to the two blocks and allows the formation of cylindrical micelles with crystalline core and amorphous corona. Specifically, we have found that the crystallization-driven self-assembly (CDSA) method provides an effective route to control the length of these cylindrical micelles from tens of nanometers up to above 800 nanometers, with a monodisperse (PDI < 1.2) length distribution. Due to the semiconductive nature of both core and corona of these micelles, they are demonstrated to be electroactive by tunneling atomic force microscope. The paper about this study is under preparation.
2) Field-effect transistors (FETs) based on cylindrical micelles from RR-RS diblock copolymers. We recently further explored the application of these electroactive cylindrical micelles by incorporating them into the active layer of FETs. By incorporating cylinders with controlled length, we found the length of cylinders can influence the charge-carrier mobility and thus the device performance greatly. The paper about this study is also under preparation.
3) Other research works beyond the original scope of this proposal. Formation of amphiphilic cylindrical B-A-B triblock co-micelles and their hierarchical superstructures has been achieved. Amphiphilic cylindrical B-A-B triblock co-micelles have been synthesized through a modified crystallization-driven living self-assembly approach. Supermicelles with hierarchical architectures have been obtained by assembling the micelles via a variety of interactions, such as solvophilic / solvophobic, hydrogen-bonding, etc.. Manuscript on the formation of amphiphilic cylindrical B-A-B triblock co-micelles and the formation of supermicelles has been submitted.
The proposed transfer of knowledge objectives progressed well throughout the duration of the fellowship. Working in the Manners group, Dr. Li has gained significant experience in the areas of polymer synthesis, self-assembly (especially CDSA), and characterization of nanoscale objects. Through the supervision of graduate students, Dr. Li has been able to transfer knowledge and skill sets to the students. Dr. Li established collaborative contacts within the EU that will be maintained in his future.
The work completed during the course of this fellowship will make a significant impact on the field of semiconductive polymer synthesis, self-assembly and device fabrication. The synthesis of diblock P3HT with different regioregularities is expected to have some influences in the field of semiconductive polymers. Also the discovery of cylinder length-dependent FET device is of great fundamental interest and provides new insights into semiconductive polymer device area. As a result of activities made possible by this fellowship, Dr. Li has obtained a faculty position at the Beijing Institute of Technology (China).
Highlights include:
1) The synthesis of all conjugated regioregular P3HT-block-regiosymmetric P3HT. This is the first example of semiconductive block copolymers with blocks of different regioregularities. The different regioregularities impart different properties to the two blocks and allows the formation of cylindrical micelles with crystalline core and amorphous corona. Specifically, we have found that the crystallization-driven self-assembly (CDSA) method provides an effective route to control the length of these cylindrical micelles from tens of nanometers up to above 800 nanometers, with a monodisperse (PDI < 1.2) length distribution. Due to the semiconductive nature of both core and corona of these micelles, they are demonstrated to be electroactive by tunneling atomic force microscope. The paper about this study is under preparation.
2) Field-effect transistors (FETs) based on cylindrical micelles from RR-RS diblock copolymers. We recently further explored the application of these electroactive cylindrical micelles by incorporating them into the active layer of FETs. By incorporating cylinders with controlled length, we found the length of cylinders can influence the charge-carrier mobility and thus the device performance greatly. The paper about this study is also under preparation.
3) Other research works beyond the original scope of this proposal. Formation of amphiphilic cylindrical B-A-B triblock co-micelles and their hierarchical superstructures has been achieved. Amphiphilic cylindrical B-A-B triblock co-micelles have been synthesized through a modified crystallization-driven living self-assembly approach. Supermicelles with hierarchical architectures have been obtained by assembling the micelles via a variety of interactions, such as solvophilic / solvophobic, hydrogen-bonding, etc.. Manuscript on the formation of amphiphilic cylindrical B-A-B triblock co-micelles and the formation of supermicelles has been submitted.
The proposed transfer of knowledge objectives progressed well throughout the duration of the fellowship. Working in the Manners group, Dr. Li has gained significant experience in the areas of polymer synthesis, self-assembly (especially CDSA), and characterization of nanoscale objects. Through the supervision of graduate students, Dr. Li has been able to transfer knowledge and skill sets to the students. Dr. Li established collaborative contacts within the EU that will be maintained in his future.
The work completed during the course of this fellowship will make a significant impact on the field of semiconductive polymer synthesis, self-assembly and device fabrication. The synthesis of diblock P3HT with different regioregularities is expected to have some influences in the field of semiconductive polymers. Also the discovery of cylinder length-dependent FET device is of great fundamental interest and provides new insights into semiconductive polymer device area. As a result of activities made possible by this fellowship, Dr. Li has obtained a faculty position at the Beijing Institute of Technology (China).