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 × 10 ³ Ω □^-1); moreover, instead of 0.22, the ratio of DC conductivity to optical conductivity (σ_DC/ σ_OP) was 2.60. The higher σ_DC/σ _OP ratio indicates a higher TCFs performance.