Nanocomposites and nanomaterials

Structural and thermal studies of MWCNT/poly(dimethylsiloxane) nanocomposites
Sulym I.Ya.1, Sternik D.2, Goncharuk O.V.1,
 Sementsov Yu.I.1, Derylo-Marczewska A.2
1 Chuiko Institute of Surface Chemistry, NASU, 17 General Naumov Str., 03164 Kyiv, Ukraine.
E-mail: irynasulym@ukrl.net
2 Faculty of Chemistry, Maria Curie-Sklodowska University, M.C. Sklodowska Sq.3, 20031 Lublin, Poland.

The incorporation of CNT into polymer improves their tensile strength, toughness, glass transition temperature, thermal conductivity, electrical conductivity, and mechanical properties. The current work focuses on research of the structural and thermal characteristics of composites based on powder multiwall carbon nanotubes (MWCNT), synthesized using catalytic chemical vapor deposition (CCVD), and linear poly(dimethylsiloxanes) of two molecular weights (PDMS-50 and PDMS-400 with Wm ≈ 2970, dp = 38, and Wm ≈ 5700, dp = 75, respectively).
The thermal characteristics (TG, DTG, and DSC) of the initial MWCNT and MWCNT/PDMS composites were studied upon heating of samples in air. The influence of PDMS revealed in a shift of characteristic DSC and DTG peaks. The degradation of the initial MWCNT took place in only one stage (Tmax2 = 628 ºC), while for all the samples with a polymer – in two stages (Tmax1 around 478 ºC and Tmax2 = 667-717 °C).
The structural properties and quality of the initial MWCNT and MWCNT/PDMS composites were investigated by means of Raman spectroscopy. Raman spectra exhibit the graphitic or G-band (around 1600 cm-1) from highly ordered CNTs sidewalls, whereas disorder in the sidewall structure results in the D-band (around 1310 cm-1). The integral intensity ratio between the D and G bands (AD/AG) is very important factor to distinguish the structural imperfections, i.e. chemical change of CNTs sidewalls and the percentage of defect. Decrease in AD/AG ratio for both series of samples after polymer adsorption (at CPDMS = 50 wt. %) was found (from 2.09 to 1.59 and to 1.55 for MWCNT/PDMS-50, and MWCNT/PDMS-400 composites, respectively), what indicates the decrease of concentration of structural defects and degree of disorder in the systems.