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Study on morphologies of polymer nanocomposites with thermally stable Au NPs and star polymer 원문보기

  • 저자

    유미상

  • 학위수여기관

    Graduate School, Korea University

  • 학위구분

    국내박사

  • 학과

    化工生命工學科

  • 지도교수

    方畯昰

  • 발행년도

    2014

  • 총페이지

    xii, 234 p.

  • 키워드

    nanocomposite block copolymer gold nanoparticle star polymer;

  • 언어

    eng

  • 원문 URL

    http://www.riss.kr/link?id=T13541898&outLink=K  

  • 초록

    Self-assembly of block copolymer have been considered one of promising method to build nanometer scale features as a “bottom-up” method which can be overcome the limitations of “top-down” methods. Incorporation of metal nanoparticles into the polymeric system can allow for the formation of multi-functional thin films while achieving performances beyond those possible with single materials. However, all studies involving metal nanoparticles suffer from the thermal instability. To resolve the problem, we introduce the UV cross-linkable azide group (-N3) into the polymeric ligands attached to the Au core, so that the Au cores can be protected by cross-linked shells after in situ UV-cross-linking to give core-shell nanostructures. The resulting Au nanopaticles exhibited excellent thermal stability in both solution and thin film states after heat treatment. We also demonstrated that the thermally stable Au nanoparticles can act as effective compatibilizer in PS/PMMA homopolymer blend system. When the nanoparticles were incorporated into the polymeric matrices, accurate control of the placement of nanoparticles is critical to capitalize on the properties of nanoparticles. We could precisely tune the interfacial interaction between the Au nanoparticles and block copolymer template by varying the composition of MMA and styrene in polymeric ligands attached onto the Au nanoparticle surfaces. These selective or neutral Au nanoparticles were introduced to control the orientation of microdomains in block copolymer thin films. In case of lamellar forming PS-b-PMMA thin films, the neutral Au nanoparticles located at the interface of PS/PMMA domains induced the perpendicular orientation of PS-b-PMMA to the substrate. On the other hand, cylinder forming PS-b-PMMA thin films were orientated perpendicular to the substrate when the PMMA selective Au nanoparticles were added. The lateral and vertical location of the Au nanoparticles was investigated by transmission electron microscopy (TEM) tomography. Despite the Au nanoparticles' advantages such as easy tracing of Au nanoparticles in polymer matrix due to the strong contrast between Au nanoparticles and polymers under electron microscopy and tunability of the surface through the facile grafting of thiol end groups (-SH), the Au nanoparticles are still remained even after the dry or wet etching step owing to the its high etching resistance. To fabricate etching-friendly nanocomposite thin films, we introduced the neutral star polymer made up with P(S-r-MMA) random copolymer arms by “arm-first” method using Atom transfer radical polymerization (ATRP). The neutral star polymers induced a transition in the orientation of microdomains from parallel to perpendicular to the substrate. The vertical distribution of star polymer was investigated by neutron reflectivity.


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