Preparation And Properties Study Of V-shaped Amphiphilic Polymer Brushes Grafted Nanomaterials

Carbon nanotubes have been an area of intense research due to its potential utility in numerous areas,such as molecular wires and electronic,sensors,high-strength fibers,and field emission displays.Nanodiamond is a promising and valuable powder material with the remarkable properties like diamond such as superhardness,excellent chemical stability,thermal conductivity and biocompatibility.Recently years,the research on Nanodiamond is become popular.Nevertheless,the carbon nanotube and nanodiamond are not soluble in almost any solvents,which remain a severe limitation to the extensive use.So,it is very important to functionalize the carbon nanotubes and nanodiamond in order to improve their dispersibility in solvents and matrics. Reversible addition fragmentation chain transfer mediated polymerization(RAFT), one of a number of leading living radical polymerization techniques,has attracted considerable interest.It provides molecular weights predetermined by the chain transfer agent and conversion,and,more importantly,Produce polymers under mild reaction conditions.The main purpose of this work is to study the synthesis of well-defined functional polymers via the RAFT process and surface-modification of carbon nanotubes and nanodiamond with polymers resulting from living radical polymerization.This dissertation contains the following aspects:(1)Functional monomers N,N-dimethylaminoethyl methacrylate(DMAEMA), poly(ethylene glycol)methyl ether methacrylate(PEGMA),t-butyl methacrylate (t-BMA),2-hydroxyl ethyl methacrylate(HEMA),glycidyl methacrylate(GMA), methy methacrylate(MMA) and styrene(st) were polymerized by RAFT with cumyl dithiobenzoate as a chain transfer agent and AIBN as initiator.The process showed living characteristic and the functional polymers were obtained with controlled molecular weights and polymer polydispersity indices less than 1.35.Tri-block copolymers PtBMA-b-PGMA-b-PS,PMMA-b-PG MA-b-P(PEGMA), PtBMA-b-PHEMA-b-PDMAEMA containing small amount of epoxy groups or hydroxyl groups in the middle of the chains were synthesized by sequential polymerization of functional monomers using macro-chain transfer agent via RAFT process.The adamantine containing block copolymers were synthesized by reaction of amantadine with the epoxy groups of PtBMA-b-PGMA-b-PS.(2)PS and PtBMA were grafted onto nanodiamond particles by the reaction of epoxy groups in the block copolymers of PtBMA-b-PGMA-b-PS and carboxylic groups on the surface of nanodiamond.This "center-linking" process resulting in "V shaped" block polymer functionalized nanodiamond PtBMA-g-ND-g-PS.TEM,SEM, and TGA were employed to determine the structure,morphology,and the grafting quantities of the resulting products.Amphiphilic polymers grafted nanodiamond PMAA-g-ND-g-PS was prepared by subsequent hydrolysis of the tert-butyl group into carboxylic group.Those "V shaped" Amphiphilic polymers grafted nanodiamond displayed dispersibility not only in organic solvent but also in water. PMAA-g-ND-g-PS self-assembled at the interfaces of chloroform and water,or toluene and water.(3)PtBMA-b-PGMA-b-PS and PtBMA-b-PHEMA-b-PDMAEMA were synthesized via RAFT process.Those block polymers were grafted onto multi-walled carbon nanotubes by the reaction of epoxy groups or hydroxyl groups in the block copolymers with carboxylic groups or chloride on the surface of tubes.This "center-linking" process resulting in "V shaped" block polymer functionalized carbon nanotubes.Amphiphilic polymers and zwitterionic polymers grafted tubes were prepared respectively by subsequent hydrolysis of the tert-butyl group into carboxylic group.These Amphiphilic polymers and zwitterionic polymers grafted tubes displayed dispersibility not only in organic solvent but also in water and showed pH responsibility.PMAA-g-MWCNT-g-PS and PMAA-g-MWCNT-g-PDMAEMA can self assemble at the interfaces of chloroform and water,or toluene and water.(4)Pristine carbon nanotubes are insoluble in either water or oil.When mixtures of CNTs,water,and organic solvent are sheared vigorously,a macroscopic emulsion of oil droplets forms in water,with the CNTs residing at the interface between the immiscible fluids,acting as a natural "surfactant" or interphase material.Herein we present the formation of amphiphilic polymer grafted CNTs by simultaneous biphasic grafting of different polymer at a liquid/liquid emulsion interface through free radical polymerization.Interface is separated into two phases,which can be synchronously modified by free radical polymerization in the two phases with hydrophilic/lipophilic monomers.As a result,through one single step we prepared amphiphilic polymer grafted CNTs PS-g-MWCNT-g-PAM and PS-g-MWCNT-g-PDMAEMA.This approach is facile with high grafting efficiency.