† Nanostructures of PS-b-PEO Diblock Copolymer and its Nanocomposites

 

Juntao Wu, Minhua Zhao, Tinh Nguyen and Xiaohong Gu*

 

Materials and Construction Research Division, National Institute of Standards

and Technology, Gaithersburg, MD 20899

 

 

†††† Thin films of polystyrene-block-poly (ethylene oxide), PS-b-PEO, were prepared under different relative humidities (RHs) by spin coating. Effects of RH on the nanostructures of self-assembled PS-b-PEO were investigated using atomic force microscopy (AFM). The stability of the formed structures under different RHs in ambient condition was also studied by AFM with the aid of a small volume AFM environmental chamber. The results show that, the orientation and the ordering of the copolymer nanostructures are very sensitive to the humidity of the environments during the film formation. Well-defined cylindrical nanodomains oriented perpendicular to the surface are induced by the high humidity during spin coating. These perpendicular cylindrical structures are stable at a variety of the RHs, except that PEO domains are swollen at high RH (90 %) to form mushroom-like structures. Upon drying, the original nanostructures of the copolymer reform, indicating the swelling process is reversible. Moreover, the AFM phase contrast between the cylindrical PEO domains and the PS matrix has been significantly increased at the elevated RHs. After incorporation of the nanoparticles, however, the overall morphological structures of the PS-b-PEO are altered. The cylindrical nanodomains are still observed, but not as well-defined as those in the pure PS-b-PEO system. The aggregation of the nanoparticles appears to interrupt the long-range ordering of the nanostructures of the copolymer.

 

 

My Name: JUNTAO WU

 

Mentorís name: XIAOHONG GU

 

Division: 861

 

Laboratory: BRRL

 

Room and Building address: B344/bldg226

 

Mail Stop: 8615

 

Telephone #: 6714

 

FAX #: 301-990-6891

 

email: juntao.wu@nist.gov

 

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