Sheng-Yen Wu

Effect of extended polymer chains on properties of transparent graphene nanosheets conductive film

This study examined the intercalation reaction of graphite oxide (GO) with poly(acryl amide)/poly(acrylic acid) (PMA) as a method to control the spacing between GOs. The interlayer spacing of GO was increased from 0.80 to 1.21 nm by grafting PMA on the GO surface. To fabricate transparent conductive films (TCFs), GOs must be reduced to graphene nanosheets (GNS) by a two-step chemical reduction with increased conductivity. The intercalated polymer chains of poly(acrylic acid) between GNS were extended as the carboxylic acid groups were deprotonated by the Na+ ions of NaBH4 on reduction, which efficiently inhibits GNS aggregation and restacking. The Na+ bonding on the polymer chains also facilitates electron transfer between the layers, yielding lower surface electrical resistance at the same GNS film thickness. The PMA grafted GNS (NE-PMA-GNS) composite films show the lowest sheet resistance of 2.11 × 102 Ω □−1, which is one order of magnitude less than that without grafting polymer (NE-GNS, 1.86 × 103 Ω □−1); moreover, instead of 0.22, the ratio of DC conductivity to optical conductivity (σDC/σOP) was 2.60. The higher σDC/σOP ratio indicates a higher TCFs performance.

The effect of extended polymer chains on the properties of transparent multi-walled carbon nanotubes/poly(methyl methacrylate/acrylic acid) film

Optically transparent and electrically conductive thin films composed of multi-walled carbon nanotube (MWCNT) reinforced polymethyl methacrylate/acrylic acid (PMMA/AA) were fabricated using a wire coating technique. Poly(acrylic acid) controls the level of MWCNT dispersion in aqueous mixtures and retains the well-dispersed state in the polymer matrix after solidification resulting from extended polymer chains by adjusting the pH value. The exfoliating the MWCNT bundles by extended polymer chains results in the excellent dispersion of MWCNT. It causes a lower surface electrical resistance at the same MWCNT content. The hydrophilic functional groups (-COO( - )NA( + )) also caused a decrease in the crystallization of PMMA and led to an increase in the transmittance.