Synthesis Of Precise Polymer Chain Structures By Using Furan/maleimide Dynamic Covalent Bond

Polymeric materials have extensive applications in numerous fields for their excellent properties,such as industry,biology,information technology and so on.However,traditional polymeric materials cannot meet the rising demand of current society.There is an increasing tendency to develop polymeric materials with high performance and multifunction.As wellknown,polymeric structure determines its properties.The design and synthesis of polymer chain structures is beneficial to understanding of the relationship between polymer chain structures and properties and is distinctly important for the development of polymeric materials.Sequence and topology,two important polymeric primary structures,play an extremely important role in performance of polymer.Therefore,design and synthesis of sequence-controlled and topological polymer as well as further research on the relationship between polymer chain structures and properties are important subject in polymer science.Dynamic covalent bonds,a stimulus-response covalent bond,has been widely applied to synthesize of precise polymer and design functional polymeric materials for its advantages,such as mild reversible reaction condition,fast exchange rate.In this thesis,the fabrication of single chain polymeric nanoparticles and thioester-containing sequence-controlled polymer were realized utilizing dynamic covalent bond of furan/maleimide.1)Furanprotected maleimide moieties(FMI),a convenient synthetic platform for single-chain folding,were incorporated into polymer side chain.Several well-defined single-chain polymeric nanoparticles(SCNPs)with variable sizes were synthesized via different intramolecular crosslinking reaction.Furthermore,we researched the influence of different chemical crosslinking reactions and conditions on the single-chain folding manner and the variation of the surface properties of spin-coating films prepared by SCNPs,such as surface roughness,hydrophilic-lipophilic property,cell growth.2)Thioester-containing functional polymers with different sequential structures were fabricated via dormant monomer strategy,in which thioester-containing furan-protected maleimide served as dormant monomer.A novel approach to synthesize side-chain functional sequence-controlled polymer was explored by utilizing high reactivity of thioester.Specific research contents are as the follows:(1)Efficient fabrication of single-chain polymeric nanoparticles by utilizing furan/maleimide dynamic covalent bond.Linear precursors with different molecular weights were prepared by reversible addition-fragmentation chain transfer(RAFT)polymerization and subsequent post-modification.Then,these linear polymer chains were folded into globular particles with diameters of 5-20 nm via three folding routes: intramolecular ringopening metathesis polymerization(ROMP),intramolecular RAFT polymerization,or bimolecular thiol-maleimide coupling.Size exclusion chromatography(SEC),proton nuclear magnetic resonance spectroscopy(1H NMR),atomic force microscopy(AFM),and dynamic light scattering(DLS)analyses confirmed the formation of these SCNPs.The chain-polymerization routes(RAFT and ROMP)resulted in more compact nanoparticles than the thiol-maleimide bimolecular coupling route because of the different inherent reaction mechanisms.SCNPs were made into polymeric films and served as carrier for cell culture.Cell culture experiments revealed that cell proliferation was promoted for these surface-bound SCNPs compared with those bound with a linear precursor.This work offers a new perspective on the fabrication of SCNPs with variable sizes and an instructive pathway for the potential use of SCNPs as functional polymeric materials.(2)Synthesis of side-chain functional sequence-controlled polymers based on furanprotected maleimide dormant monomer strategy.Thioester-containing furan-protected maleimide(FMITL)was used for dormant monomer,and then temperature dependence of reverse Diels-Alder reaction was explored.The results indicate that retro-Diels-Alder reaction could not occur under 40 ? while efficient retro-Diels-Alder reaction occur under 110 ? and thioester-containing polymerizable maleimide(MITL)generated.The copolymerization of MITL and styrene revealed its alternating copolymerization feature.According to these preliminary explorations,thioester-containing functional polymer with different sequence structure were prepared at programmed changes of temperature via dormant monomer strategy.Finally,an efficient approach to synthesize side-chain functional sequence-controlled polymer was established based on high reactivity of thioester.