Materials Science

Bio-inspired Self-assembly of Functional Polymers
Zhixiang Wei, National Center for Nanoscience and Technology

Understanding the self-assembly behavior of natural materials is a crucial factor in designing nanoscale functional materials. Base on the assembly mechanism of biological molecules, many fascinating nanostructures and superstructures of biomolecules have recently been realized. Instead of using hydrogen bonds among biological molecules, - stacking interactions is the basic driving force for self-assembling nanostructures of functional molecules. As commonly known, both hydrogen bonds and - stacking interactions are directional interactions. Therefore, using synthetic functional molecules to self-assemble ordered nanostructures and superstructures by mimicking the assembly behavior of biomolecules is of great importance for function-oriented designing novel nanomaterials.

In this presentation, we will talk following contents using conjugated polymers as building blocks:

(1) Chiral conjugated polyaniline was used as building blocks to self-assemble nanostructures and superstructures with homochirality. The self-assembly behavior is similar to the protein, but the nanostructures posses anisotropic conductivity.[1]

(2) A general strategy was used to synthesize vertically aligned conjugated polymer nanostructures, which can be acted as high-performance electrode materials for supercapacitors.[2]

(3) A facile solution strategy was proposed to prepare branched and hyper-branched poly(3-hexylthiophene) nanostructures , which are further used to improve the efficiency of optoelectronic devices.[3]

Review Articles:

Helical polymers: Tuning twists, NPG Asia Materials research highlight, Published online 01 June 2009.

How Far Can We Push Chemical Self-Assembly?, Robert F. Service, Science 1 July 2005: Vol. 309 no. 5731 p. 95, DOI: 10.1126/science.309.5731.95.

References:

[1] Y. Yan, R. Wang, X. H. Qiu, Z. X. Wei.* “Hexagonal Superlattice of Chiral Conducting Polymers Self-Assembled by Mimicking -Sheet Proteins with Anisotropic Electrical Transport” J. Am. Chem. Soc. 2010, 132(34), 12006-12012.

[2] K. Wang , W. J. Zou , B. G. Quan , A. F. Yu , H. P. Wu , P. Jiang, Z. X. Wei *, “An All-Solid-State Flexible Micro-supercapacitor on a Chip” Adv. Energy Mater. 2011, DOI: 10.1002/aenm.201100488

[3] H. Yan, Y. Yan, Z.Yu, and Z.X. Wei*, “Self-Assembling Branched and Hyperbranched Nanostructuresof Poly(3-hexylthiophene) by a Solution Process”. J. Phys. Chem. C. 2011, 115, 3257.

Background summary

Several keywords for this presentation:

(1) Self-assembly is a term used to describe processes in which a disordered system of pre-existing components forms an organized structure or pattern as a consequence of specific, local interactions among the components themselves, without external direction. When the constitutive components are molecules, the process is termed molecular self-assembly; when the When the constitutive components are nano-objects, the process is termed nano self-assembly
Self-assembly in the classic sense can be defined as the spontaneous and reversible organization of molecular units into ordered structures by non-covalent interactions. The first property of a self-assembled system that this definition suggests is the spontaneity of the self-assembly process: the interactions responsible for the formation of the self-assembled system act on a strictly local level—in other words, the structure builds itself.

(2) Functional polymers are polymers with advanced optic and/or electronic properties. Advantages of functional polymers are low cost, ease of processing and a range of attractive mechanical characteristics for functional organic molecules. One can adjust properties while keeping material usage low.
Herein, we specifically interested with the conjugated polymers (also named as conducting polymers). Such compounds may have metallic conductivity or can be semiconductors. The biggest advantage of conducting polymers is their processability. They have been incorporated into commercial displays and batteries. They are also promising in organic solar cells, printing electronic circuits, organic light-emitting diodes, actuators, electrochromism, supercapacitors, biosensors, flexible transparent displays, electromagnetic shielding and possibly replacement for the popular transparent conductor indium tin oxide. Conducting polymers are rapidly gaining attraction in new applications with increasingly processable materials with better electrical and physical properties and lower costs. The new nanostructured forms of conducting polymers particularly, provide fresh air to this field with their higher surface area and better processability.

(3) Bioinspired (also named as biomimetic, bionics and etc. ) is the study of the structure and function of biological systems as models for the design and engineering of materials and machines

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Materials Science

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