Immobilized Imidazolium Ionic Liquid And Impact On Properties Of Carbon Nanotube-based Polymer Composites

Ionic liquids (IL) are a kind of molten salts which have unique structures and properties. The incorporation of imidazolium IL and support materials expected to combines their merits and gave the attractive characters to the new hybrid. Many studies have shown that there are supramolecular ?-? stacking interactions between imidazolium IL and CNTs, leading to remarkable scientific and technological advances in the development of CNTs-based materials. More importantly, such noncovalent approaches are easy to perform and have an additional advantage in that they can avoid disruption of the ?-electronic conjugation of the CNTs. Their properties can also be adjusted to meet the requirements of a particular process. The objective of this study here aims at fabricating CNTs composites based on this noncovalent interaction and demonstrating the introducing of imidazolium segment in improving the performance of the final composites. This work includes four main parts as follows:(1) IL was loaded to the nanoparticle and we employed a new strategy to prepare IL-CNTs hybrids by in situ polymerization and crosslinking. The ionic liquid monomers were attached on the surface of CNTs through ?-? interaction. By copolymerized with DVB monomers,the IL polymer will be cross-linked to form a network structure, and wrapped onto the surface of CNTs. The resulting hybrids had a well core-shell structure with CNTs as the nuclear and polymer as the shell.By adjusting the kind of monomer, solvents and concentrations of solution, we could adjust the thickness of the polymer shell. The conductivity of hybrids could range from 12.98 S·cm-1 to 2.45×10-7 S cm-1, decreased with the enhancement of polymer shell in a nonlinear way. The process of modification lead to less structural damage of CNTs than the typical acid-oxidation treatment, and will be a valuable tool for synthesizing core-shell structured hybrid for large-scale applications.(2) IL was loaded to the polymer and we have synthesized polycaprolactone (PCL) macromolecules containing imidazolium segment. First, an imidazole IL with hydroxyl group was successfully synthesized. PCL diol bearing imidazolium cations have been performed by ring-opening polymerization (ROP) of ?-caprolactone (?-CL) initiated from the hydroxylated ionic liquid. Linked by urethane, PCL blocks finally became multi-block macromolecules which have the imidazolium segment preserved in polymer chain. Imidazolium cations enable to further tailor the thermal stabilities properties of PCL and the degradation rate could also be effectively modulated. More importantly, the polymer provided an attractive and efficient strategy for fabricating composites because of the supramolecular cation-? interactions between polymer matrices and CNTs. The CNTs composites showed two orders of magnitude higher conductivity than the contrast sample.(3) We studied the impacts of IL loading on polymer composites.The CNTs/PVDF composites were fabricated using the IL-CNTs hybrids above via solution casting. The IL shell took part in the formation of composites interfaces so the properties of composites were directly correlated with it. We also investigated the relationship between the coating and the conductivity, permittivity, dielectric loss of the final composites. Moreover, the block copolymer consisting of ionic liquid modities was used as interfacial controller compatibilizer between CNTs and PCL to assess the CNTs dispersion in the polymer matrix because the imidazolium rings segment could interact with CNTs by ?-? staking interaction while the PCL block segment was compatible with PCL matrix. The resulting CNTs/PCL composites with the polymer showed well dispersibility and enhancements both in electronic and dielectric properties due to excellent interfacial control by the comapatibilizer.(4) In this work, we incorporated Montmorillonite (MMT) and carbon CNTs together using IL to arouse the synergetic effect in thermoplastic elastomer. Modified by imidazolium ionic liquid, CNTs exhibited affinity for the negatively charged MMT nanolayers in aqueous solution. The electrostatic self-assembly approach made CNTs been encapsulated into MMT layers to form a sandwiched architecture. This unique hybrid architecture endowed the CNTs with an insulation layer which could suppress the leakage current in composites by preventing direct contact between CNTs in the polymer matrices. The obtained MMT-CNTs composites exhibited high dielectric constant and low dielectric loss over a wide frequency range. By controlling the proportion offillers, the dielectric properties could be easily tailored.