Preparation of Polyionic Liquids via RAFT-PISA and Preparation of Polymers via Photoinitiated Catalytic System

Author:Yang Yong Qi

Supervisor:an ze sheng


Degree Year:2019





Polymeric materials have important applications in industrial production and daily life,especially in aviation,optoelectronic devices,and nanocarriers.As a reversible deactivation radical polymerization(RDRP),reversible addition-fragmentation chain transfer(RAFT)is a powerful and versatile technique widely used in precise synthesis of a variety of polymers,including homopolymers,gradient polymers,block polymers,star polymers as well as polymers with more complex structures,including microgels and polymer brushes.There are few studies on the preparation of polymers by ionic liquid monomer for polymerization induced self-assembl,and there is a lack of systematic research.A series of ionic liquid monomers with different chain length cations and different anion types were synthesized,the polymerization induced self-assembly of them was studied in detail.Then,RAFT-PISA of[MVBIm][BF4]and[BVBIm][BF4]was conducted using PDMA43 as a macro molecular chain transfer agent(macro-CTA)in ethanol at 70℃.The effect of solid content and degree of polymerization on the morphology of PDMA43-P([BVBIm][BF4])x were investigated in detail.The phase diagram was constructed in order to study the morphological evolution.The structures of PDMA43-P([BVBIm][BF4])x was confirmed by 1H NMR,morphologies were determined via TEM and the glass transition temperature was measured by DSC.Next,the hexafluorophosphate imidazoles with different alkyl groups were chosen as the modular monomer,which was investigated to evaluate the effect of alkyl chain length on PISA-generated morphologies.RAFT-PISA was conducted via using PDMA43 macro-CTA in ethanol at 70℃ and 20%w/v solids.Experimental results show that the solvophobicity and steric hindrance of monomers enhance with the increasing length of the alkyl moieties.When the carbon chain is 12 or 16,only co mpo und lamellae/ellipso id vesicles were obtained.By comparing the morphological evolution of PDMA43-P([BVBIm][BF4])x and PDMA43-P([BVBIm][PF6])x nano-objects,higher order morphologies are more accessible for hexafluorophosphate based PISA due to its higher solvophobicity.Photocatalytic room temperature preparation of polymer research work is mostly concentrated on metal catalysts,but there are problems of low catalytic efficiency and often introducing metal ions to contaminate polymers.In order to solve the above problems,organic dyes phthalimide(PDI)and triethanolamine(TEOA)were used as a redox initiation system.In order to reduce the aggregation of PDI in aqueous solution and increase its solubility,cucurbit[7](CB[7])was employed to form a host-guest complex(PDI/(CB[7])).The photoinitiated/catalyzed RAFT solution polymerization was conducted at room temperature irradiated by green light.The UV-Vis absorption spectroscopy,fluorescence spectroscopies and cyclic voltammetry measurements and polymerization results show that the photocatalytic system involves a hybrid mechanism involving photosensitized initiation and PET-RAFT.Kinetic study shows that the host-guest complex of PDI and CB[7]can increase the polymerization rate because of reduced aggregation and lowered energy levels of PDI,which can facilitate the PET from TEOA to PDI/(CB[7])2 complex.The photopolymerization can be activated and deactivated by switching the light on and off.This photopolymerization system is highly efficient and PDMA with an ultrahigh molecular weight(Mn,GPc=1.04 × 106 g/mol)can be readily synthesized in a short time(8 h)at an extremely low photocatalyst concentration(1 ppm relative to monomer).The molecular weight determined by GPC is close to the theoretically calculated molecular weight and the dispersity is relatively low.The supramolecular photopolymerization system also exhibits high livingness and provides a high level of control over the synthesis of homopolymers of other kinds of monomers and efficiently to produce block copolymers and with predictable molecular weight and low dispersities.