Preparation Of Polypyrrole/ Graphene Composites And Their Electromagnetic Behaviours

Considering it’s unique structure and outstanding properties, graphene has attracted increasing attentions and become a focus in various areas, such as materials, chemistry and physics. As a typical conducting polymer, polypyrrole(PPy) possesses high electrical conductivity, good oxidation resistance and simple synthetic. In this paper, series of polypyrrole/graphene composites were synthesized using in situ intercalation polymerizations of pyrrole cation(Py+) into the layers of graphite oxide(GTO), expanded graphite(EG) and natural graphite(NG). Differences among the pyrrole’s intercalation effect to different kinds of graphite. The electromagnetic properties of a series of polypyrrole/graphene composites was also studied.First, graphite oxide was uesd as the carbon resource. An in situ intercalation polymerization was carried out for the preparation of polypyrrole/graphene oxide composites. Using Na2O4S2 and NaOH mixed solution as the chemical reducing agent, polypyrrole/reduced graphene oxide composites were further prepared. It was found that the layers of graphite oxide could be exfoliated to mono or few later graphene and make more wrinkled structures.It was believed to be due to the in situ intercalation polymerization of pyrrole cation into the layers of graphite oxide and the chain movement of PPy insite the layers of graphite oxide during the intercalation polymerization.Secondly, EG was used to synthesize polypyrrole/graphite nanosheets hybrid materials using an in situ intercalation polymerization. The results showed that pyrrole cation could intercalate into the the layers of EG and played an important role in the intercalation polymerization. Different intercalation seperation effect could be obtained by dominating the mole of ratio Py to EG. When the mole ratio of pyrrole to EG was 100:0.5, a optimal seperation effect of EG was reached in the X-ray diffraction patterns, the relative intensity of diffraction peak of graphite (002) plane showed the weakest direction. A further study showed that the seperation effect of EG could also be affected by the amount of HCl.Thirdly, NG with various particle sizes were used as carbon resource to investigate in situ intercalation polymerization mechanism of pyrrole cation into the layers of graphite. Series of polypyrrole/graphene nanosheets composites were synthesized using the in situ intercalation polymerization of pyrrole cation respectively into the layers of different sized natual graphite. It was found that thickness of NG layers significantly decreased after the pre-intercalation of pyrrole cation.The followed in situ intercalation polymerization of pyrrole cation into the layers of expanded graphites could further separate graphite into nano-exfoliated graphite sheets obtaining polypyrrole/graphene nanosheets composites. It has been found out that particle size of NG have something to do with the exfoliating effect of NG. It showed a better exfoliating effect when the particle size was 44,25 and 3 μm and exhibited a worse exfoliating effect when the particle size was 2.6 or 40 μm.Electromagnetic properties of series of polypyrrole/graphene composites were studied. It has been found that the polypyrrole/graphene composites showed obvious improvement in microwave absorption compared with those of the polypyrrole or the graphite itself. For polypyrrole/graphene oxide with a thickness of 3 mm, the reflection loss(RL) reached -36 dB at 13.4 GHz and the bandwidth corresponding to the reflection loss at -10 dB was 6.2 GHz (from 9.6 to 15.8 GHz). When the feed ratio of pyrrole to EG was 100:0.5, the polypyrrole/graphene hybrid performed the most excellent electromagnetic wave absorption properties, the optimal absorption peak reached -48 dB at 13.4 GHz with a thickness of 2.7 mm.