Carbon Nanotube Induced Polymer Crystallization, Structure and Morphology

Drexel University, Philadelphia PA

Investigators

Abstract

TECHNICAL SUMMARY: The extraordinary mechanical, electrical and optical properties of carbon nanotubes (CNTs) have attracted great attention in recent years. The demand for products containing CNTs has created a pressing need to transfer these properties from nano- to macro- scale. One essential step towards this goal is assembling/processing CNTs, which involves dispersing them in an organic solvent/polymeric matrix. To this end, soft materials, polymers in particular, have been used to modify CNT surfaces. By using a controlled solution polymer crystallization method, the PI?s lab recently demonstrated that polymer lamellar single crystals could grow on CNT surface, leading to an intriguing hybrid nanostructure named as Nano Hybrid Shish Kebab (NHSK). NHSK provides a unique nanoscale platform that can be used for a variety of applications. The proposed research aims at systematically studying the structure and formation mechanism of this unique hybrid system. Specifically, the PI will, 1) fabricate NHSKs using a variety of crystallization conditions and explore the correlation between crystallization conditions and NHSK features such as periodicity as well as the kebab sizes; 2) demonstrate that NHSK is a general feature for CNT-crystalline polymer systems. The generality of the NHSK is two-fold: a) NHSK could form for different types of CNTs as well as for a variety of crystalline polymers; b) NHSK can be formed not only by solution crystallization, but also by other crystallization techniques such as physical vapor deposition of crystalline polymers as well as bulk crystallization; 3) fabricate uniformly patterned NHSK using block copolymers (BCPs). Semicrystalline BCPs will be used to form CNT/BCP NHSKs. It is anticipated that the uniformity of the NHSK structure could be improved by using BCPs instead of homopolymers. Because crystalline polymers can be readily functionalized, this approach represents a unique way to functionalize CNT and it is different from all the other reported methods. NHSK also provides a platform to realize numerous possible applications of CNTs, ranging from nanocomposites, sensors to catalysis supports. BCP NHSKs could open the door to patterning on CNTs with a precise periodicity control, which is one of the major hurdles for applying CNTs in nano electronics. NONTECHNICAL SUMMARY: Due to their wonderful mechanical, electrical and optical properties, carbon nanotubes (CNTs) have been proven to be one of the most fascinating materials recently discovered. One of the major challenges of bringing CNTs to the marketplace is their poor processibility. To this end, the PI?s lab recently discovered that polymer single crystals could grow on CNTs in a controllable manner. Since polymers can be easily end-functionalized, this discovery immediately leads to a unique CNT functionalization technique which is different from all the existing methods. The hybrid structure generated, named as nano hybrid shish kebabs (NHSK), possesses much higher specific surface area compared to that of pristine CNTs. This could facilitate using CNTs in sensor and catalysis support applications. The crystalline nature of the kebabs also enables a more efficient mechanical load transfer, which could directly lead to stronger composite materials. The educational component of the proposal includes: 1) addressing the need for the education of modern developments in polymer nanoscience and nanotechnology by developing a ?Hybrid Polymeric Materials? module which will be used in the ?Nanostructured Polymeric Materials? course; 2) involving high school students and teachers, particularly under-represented populations, in the proposed research activities. These proposed educational activities encompass a broad impact. First, the proposed plan will help bridge the existing gap between levels of educational developments by involving high school students and teachers in research activities through a number of mentoring programs. Secondly, due to the high population of under-represented groups in the Philadelphia region, the proposed outreach program will be specifically geared towards encouraging the participation of under-represented populations. Thirdly, the proposed research results will be widely disseminated through publications in scientific journals, conference presentations and more highly trained secondary education teachers.