Noncovalent functionalization of carbon nanotubes using branched random copolymer for improvement of thermal conductivity and mechanical properties of epoxy thermosets

• Published in: Polymer international Vol. 67; no. 8; pp. 1128 - 1136
• Main Authors: Tang, Yuyao, Zhao, Fangqiao, Fei, Xiaoma, Wei, Wei, Li, Xiaojie, Luo, Jing, Zhu, Ye, Liu, Xiaoya
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.08.2018; Wiley Subscription Services, Inc
• Subjects: carbon nanotubes; Chain transfer; Chemical synthesis; Conjugation; Electrical resistivity; Entanglement; epoxy resin; Epoxy resins; Fillers; Free radical polymerization; Free radicals; Glass transition temperature; Heat conductivity; Heat transfer; Hydroxyethyl acrylate; Impact strength; Mechanical properties; Monomers; Multi wall carbon nanotubes; Nanotubes; noncovalent functionalization; Organic chemistry; Polymer matrix composites; Polymerization; Polyvinyl carbazole; Thermal conductivity
• ISSN: 0959-8103; 1097-0126
• DOI: 10.1002/pi.5622

A branched random copolymer, poly[(hydroxyethyl acrylate)‐r‐(N‐vinylcarbazole)] (BPHNV), was synthesized with the aim of uniformly dispersing multiwall carbon nanotubes in epoxy matrix, improving the thermal conductivity and mechanical properties while keeping the excellent electrical resistivity of the thermosets. A branched random copolymer, poly[(hydroxyethyl acrylate)‐r‐(N‐vinylcarbazole)] (BPHNV), was synthesized through a facile one‐pot free radical polymerization with hydroxyethyl acrylate and N‐vinylcarbazole monomers, using 4‐vinylmethylmercaptan as the chain transfer agent. BPHNV was employed to noncovalently modify multiwall carbon nanotubes (MWCNTs) by π–π interaction. The as‐modified MWCNTs were then incorporated into epoxy resin to improve the thermal conductivity and mechanical properties of epoxy thermosets. The results suggest that, due to both the conjugation structure and the epoxy‐philic component, BPHNV could form a polymer layer on the wall of MWCNTs and inhibit entanglement, helping the uniform dispersion of MWCNTs in epoxy matrix. Owing to the unprecedented thermal conductivity of MWCNTs and the enhancement in the interfacial interaction between fillers and matrix, the thermal conductivity of epoxy/MWCNTs/BPHNV composites increases by 78% at extremely low filler loadings, while the electrical resistivity is still maintained on account of the insulating polymer layer. Meanwhile, the mechanical properties and glass transition temperature (Tg) of the thermosets are elevated effectively, with no significant decrease occurring to the modulus. The addition of as little as 0.1 wt% of MWCNTs decorated with 1.0 wt% of BPHNV to an epoxy matrix affords a great increase of 130% in impact strength for the epoxy thermosets, as well as an increase of over 13 °C in Tg. © 2018 Society of Chemical Industry