Micellization Behavior Of Vinylidene Chloride Copolymers And Preparation Of Hierarchical Porous Carbons By Templating Methods

Hierarchical porous carbons (HPCs) contain multimodal pore size distribution of micro-, meso-and/or macro-pores, and combine advantages of large surface area and pore size. HPCs have potential application in separation, catalyst, supercapacitors. HPCs have been successfully synthesized by hard template, soft-template, template-activation combination and template-free methods. The pore structure and morphology of HPCs can be well controlled by using pre-prepared hard templates, while the removal of templates is complicated. Prepartion of HPCs by soft template method is mainly based on the self-assembly block copolymers. The preparation process is relatively simple, and the pore size and size distribution can be well designed. In this thesis, preparation of vinylidene chloride (VDC) polymer based HPCs by hard template method and preparation of HPCs by using amiphiphilic VDC block copolymers as soft templates were investigated.Firstly, VDC polymer based HPCs were prepared by vapor polymerization of VDC or VDC/vinyl chloride (VC) in the presence of mesoporous silica (SBA-15) used as hard templates, carbonization of the VDC polymer/SBA-15 composites under high temperature, and remove of SBA-15 templates. The effects initiator, polymerization time and SBA-15 content on the conversion of monomer(s) were studied. The composition, structure and VDC polymer composites and corresponding porous carbons were analyzed by infrared radiation (IR.), elemental analyzer, pore size analyzer and transmission electron microscope (TEM).It is found that the maximum monomer conversion reached 39.07% when SBA-15 content was 26.19%, AIBN used as a initiator, and polymerization time of 16 h. After carbonization, surface area of VDC-VC/SBA15 nanocoposites increased to 681 m2/g. Carbonization temperatures and time also affected the pore size and size distribution. The pore channel became clearer with the increase of carbonization temperature. Using tetrapropyl ammonium bromide (TPAB) and hexadecyl trimethyl ammonium bromide (CTAB) as adsorbents, adsorption behavior of VDC polymer based HPCs was measured.Secondly, polyethylene glycol (PEG) and polyacrylic acid (PAA) were adopted as hydrophilic blocks and PVDC as hydrophobic block to synthesize PVDC-b-PEG-b-PVDC and PVDC-b-PAA block copolymers by reversible addition fragmentation-chain transfer (RAFT) polymerization. It is found that PVDC-b-PAA and PVDC-b-PEG-b-PVDC copolymers could be self-assembled to form transparent micelle aqueous solution by dissolving of the copolymer in N,N-dimethylformamide and dialysis by water. The critcal micelle concentration (CMC), micelle size and morphology of PVDC-b-PAA and PVDC-b-PEG-b-PVDC copolymers in water were analyzed via surface tension measurement, TEM and dynamic light scattering method. The CMCs of PVDC-b-PAA copolymer aqeous solution were ranged from 9.9 to 19.6 mg/L, and increased with the increasing PAA content in the copolymers. The micelles were almost in the spherical morphology with a size range of 70.9-110.9 nm and with narrow size distributions. The pH value of aqueous phase affected the Zeta potential and aggregation of of micelles. When pH value was decreased from 3 to 1, the Zeta potential of micelles was changed from a negative value to a positive one, the aggregation degree and the average size of micelle aggregates were rapidly increased, and the size distribution became wider. PVDC-b-PEG-b-PVDC copolymers were also capable of self-assembling into spherical micelles in aqueous solutions, comprising of a hydrophobic PVDC globule decorated with a loop of hydrophilic PEG segments. CMCs of PVDC-b-PEG-b-PVDC copolymers were measured under the range of 10.3-27.9 mg/L. The micelles were in spherical morphology and in a size range of 91-172 nm. The mean size of the micelles depended sharply on the length of PVDC blocks, thus enabling to control the length and disparity of the resultant spherical micelles.Finally, HPCs were prepared by soft-template method employing PVDC-b-PAA, PVDC-b-PEG-b-PVDC and poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (PEO-b-PPO-b-PEO) as soft templates, phenolic resin as carbon source. It is found that the morphologies of HPCs prepared by using PVDC-b-PEG-b-PVDC or PVDC-b-PAA copolymers as templates were quite different from that of HPCs prepared by using PEO-b-PPO-b-PEO copolymer templates. The clear order mesopore channels could be formed when PVDC block copolymers with hight contents of hydrophilic blocks (PEG or PAA) were used as soft templates.