Preparation And Characterization Of Vinylidene Chloride Copolymer Nanocomposites And Hierarchical Porous Carbons

Hierarchical porous carbons (HPCs) are new carbon materials possessing a multimodal pore size distribution of micropores, mesopores, and/or macropores, and have a board application in lithium battery and supercapacitor electrode materials, adsorption and separation, catalyst supporting and so on. HPCs containing both micropores and mesopores combine the characteristics of microporous and mesoporous carbons, and exhibit wide adsorption spectrum, great adsorption and diffusion rate, and excellent electrochemical performance. In this thesis, a noval method of preparing HPCs containing both micropores and mesopores was proposed using vinylidene chloride-methyl acrylate (VDC-MA) copolymer as carbon precursor. Inorganic materials, modified by anion group of reversible addition-fragmentation chain transfer (RAFT) reagent, were used as templates. VDC-MA copolymer/inorganic nanocomposites were prepared by RAFT living radical polymerization, and HPCs were obtained by carbonization of the as-prepard VDC-MA copolymer/inorganic nanocomposites and removal of the inorganic templates. Firstly, VDC-MA copolymer/layered double hydroxides (LDH) nanocomposites were prepared by RAFT living radical polymerization in the presence of LDH intercalated with anion group of S,S’-bis(a’a-dimethyl-a"-acetic acid)-trithiocarbonate (CTA)(CTA-LDH) RAFT agent. The structure and properties of CTA-LDH and VDC-MA copolymer/LDH nanocomposites were characterized by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA), X-ray powder diffraction patterns (XRD), transmission electron microscopy (TEM), gel permeation chromatography (GPC), and thermogravimetric analysis (TGA). It was found that the layer spacing of LDH changed from0.89nm to1.50nm when CTA group successfully intercalated into LDH through the ion-exchange reaction. It was evidenced by XRD and TEM results that LDH would be exfoliated gradually in the process of in-situ RAFT polymerization, and LDH would be distributed in the VDC-MA copolymer/LDH nanocomposites in the form of nanolaminates. The TGA data evidenced that the thermal degradation temperatures of VDC-MA copolymer/LDH nanocomposites were increased as the weight fraction of LDH increased.Secondly, the preparation of HPCs from VDC-MA copolymer/LDH nanocomposites were carried out by carbonization of the nanocomposites at600-900℃and removing of LDH and its calcined product (LDO) templates by acid etching. The structure and properties of the HPCs were characterized by FT-IR, XRD, TEM, and nitrogen adsorption-desorption. It was found that the nitrogen adsorption-desorption isotherms curves of the HPCs prepared by VDC-MA copolymer/LDH nanocomposites with different LDH contents exhibited IV type absorption behavior with a hysteresis loop at relativity high pressure, indicating the presence of mesopores in the carbons. The diameter of mesopores was about4nm. With the increase of carbonization temperature, the micropores generated by VDC-MA copolymer were greatly increased, so the specific surface area, total pore volume and micropore volume of HPCs were greatly increased, while the volume fraction of mesopores and the average pore size were decreased. Under the same carbonization temperature, the volume fraction of mesopores and the average pore size were increased with the increase of LDH content in VDC-MA copolymer/LDH nanocomposites. The result showed that LDH played a well role as mesopore template. The above results illustrated that using VDC-MA copolymer/LDH nanocomposites as the carbon precursor was a novel method to prepare HPCs containing both micropores and mesopores.Finally, VDC-MA copolymer/mesoporous silica (SBA-15) nanocomposites were prepared by in-situ RAFT polymerization, aiming to obtain ordered HPCs from the above nanocomposites. It was found that CTA was successfully anchored onto SBA-15through the reaction between acylating chlorinated CTA and SBA-15modified by amino groups. The structure and properties of CTA modified SBA-15and VDC-MA copolymer/SBA-15nanocomposites were characterized by NMR, FT-IR, EA, SEM, TEM, nitrogen adsorption-desorption and TGA. It was found that the average pore size of SBA-15 changed from9.60nm to6.82nm and BET surface area of SBA-15changed from745m2/g to124m2/g after anchoring of CTA. VDC-MA copolymerization would occur in the presence of CTA modified SBA-15, but the formed copolymer mainly existed in the reaction medium.