Enhanced Polymer Grafting from Multiwalled Carbon Nanotubes through Living Anionic Surface-Initiated Polymerization.

Journal Article · Tue Jan 01 04:00:00 EST 2008 · Chemistry of Materials

DOI:https://doi.org/10.1021/cm801449t· OSTI ID:1038820

Sakellariou, Georgios ^[1]; Ji, Haining ^[1]; Mays, Jimmy ^[1]; Baskaran, Durairaj ^[2]

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1. ORNL
2. University of Tennessee, Knoxville (UTK)

Anionic surface-initiated polymerization of ethylene oxide and styrene has been performed using multiwalled carbon nanotubes (MWNTs) functionalized with anionic initiators. The surface of MWNTs was modified via covalent attachment of precursor anions such as 4-hydroxyethyl benzocyclobutene (BCBEO) and 1-benzocyclobutene-1 -phenylethylene (BCB-PE) through Diels-Alder cycloaddition at 235 C. Surface-functionalized MWNTs-g-(BCB-EO)n and MWNTs-g-(BCB-PE)n with 23 and 54 wt % precursor initiators, respectively, were used for the polymerizations. Alkoxide anion on the surface of MWNTs-g-(BCB-EO)n was generated through reaction with potassium triphenylmethane for the polymerization of ethylene oxide in tetrahydrofuran and phenyl substituted alkyllithium was generated from the surface of MWNTs-g-(BCB-PE)n using sec-butyllithium for the polymerization of styrene in benzene. In both cases, the initiation was found to be very slow because of the heterogeneous reaction medium. However, the MWNTs gradually dispersed in the reaction medium during the polymerization. A pale green color was noticed in the case of ethylene oxide polymerization and the color of initiator as well as the propagating anions was not discernible visually in styrene polymerization. Polymer grafted nanocomposites, MWNTs-g-(BCB-PEO)n and MWNTs-g-(BCB-PS)n containing a very high percentage of hairy polymer with a small fraction of MWNTs (<1 wt %) were obtained. The conversion of ethylene oxide and the weight percent of PEO on the surface of the MWNTs increased with increasing reaction time indicating a controlled polymerization. The polymer-grafted MWNTs were characterized using FTIR, 1H NMR, Raman spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and transmission electron microscopy (TEM). Size exclusion chromatography of the polymer grafted MWNTs revealed broad molecular weight distributions (1.3 < Mw/Mn < 1.8) indicating the presence of different sizes of polymer nanocomposites. The TEM images showed the presence of thick layers of polymer up to 30 nm around the MWNTs. The living nature of the growing polystyryllithium was used to produce diblock copolymer grafts using sequential polymerization of isoprene on the surface of MWNTs.

• Research Organization: Oak Ridge National Laboratory (ORNL)
• Sponsoring Organization: SC USDOE - Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1038820
• Journal Information: Chemistry of Materials, Journal Name: Chemistry of Materials Journal Issue: 19 Vol. 20; ISSN CMATEX; ISSN 0897-4756
• Country of Publication: United States
• Language: English

Related Subjects

77 NANOSCIENCE AND NANOTECHNOLOGY
ALKOXIDES
ANIONS
BENZENE
CALORIMETRY
CARBON
CHROMATOGRAPHY
COPOLYMERS
ETHYLENE
ISOPRENE
MOLECULAR WEIGHT
NANOTUBES
OXIDES
PLASMA SWITCHES
POLYMERIZATION
POLYMERS
POTASSIUM
RAMAN SPECTROSCOPY
STYRENE
TETRAHYDROFURAN
THERMAL GRAVIMETRIC ANALYSIS
TRANSMISSION ELECTRON MICROSCOPY