Functionalization Of Multi-Walled Carbon Nanotubes By Diels-Alder Reaction And The Dielectric Properties Of Their Composites

Covalent grafting of polymers onto carbon nanotubes (CNTs) can be performed via grafting to and grafting from strategies. The grafting from strategy otherwise called surface initiated polymerization is the most promising one, since it provides control over the functionality, density, thickness, composition and architecture of the grafted polymers. Based on the strategy, homopolymers and diblock copolymers, V-shaped as well as dendrimers have been grafted onto all types of CNTs. However, no paper has been published to describe the surface initiated multifunctional molecules onto the surface of CNTs by using atom transfer radical polymerization (ATRP) with a controlled manner. In order to avoid the corrosion, pollution, and the serious break of CNTs, Diels-Alder (DA)[4+2] cycloadditions on the sp2carbons of CNTs are used for the introduction of functional groups that allow the attachment of potential initiator moieties of ATRP. The multi-walled carbon nanotubes (MWNTs) based initiator of ATRP was synthetized by using a DA reaction between MWNTs and furfuryl-2-bromoisobutyrate that obtained via esterification reaction. The MWNTs-initiator (MWNTs-Br) with controlled grafted content by changing the conditions of the DA reaction was used to surface initiated the polymerization of acrylate-POSS on the MWNT surface. The thickness of acrylate-POSS coated onto MWNTs can be changed by controlling the grafted degree of MWNTs-Br. Finally, a core-shell structure with MWNT at the center was obtained successfully and the thickness of shell can be adjusted from about5,10, to15nm through choosing different initiators. The multifunctional molecules coated MWNTs have better compatibility with other polymer matrix and it provides a potential application for the preparation of composite materials based on CNT chemistry. In this way,we tried to develop high dielectric constant carbon nanorube-polymer composites using core-shell multiwalled CNTs (MWNTs) as a filler, in which the outer graphene layer is covalently functionalized to become non-conducting by insulated POSS, whereas the inner graphene layers are unfunctionalized and remain electrically conducting. As filler, the POSS@MWNTs was added in PVDF to obtain a kind of nanocomposites which has both high permittivity and low dielectric loss.MWNTs were modified by maleic anhydride(MA) using a DA reaction. We achieved MWNTs-MA with a core-shell structure via only one step in which MA used as dienophile and MWNTs used as diene.And then the modified MWNTs were mixed with nylon(PA) to enhance its electrical capacity.Also, the MWNTs-MA/PA composites have a relatively good mechanical property. Furfuryl alcohol(FA) was attached on MWNTs by using a DA reaction. We achieved MWNTs-FA with a core-shell structure in which MWNTs used as dienophile and FA used as diene. And then the modified MWNTs were used to initiate the polymerization of caprolactone.The MWNTs-FA/PCL composites have a relatively good electrical capacitiy.