Polymer Sequence Regulation Based On Furan/Maleimide Retro Diels-Alder Reaction

The precision structure of biological macromolecule enables its specific function.Sequencing of biological macromolecules,such as genes and proteins,is considered to be one of the greatest scientific achievements in the 20th century,and inspired by the nature,exploring the relationship between polymer's sequence and function has become a research hotspot in polymer chemistry.Recently,with the introduction of various methods of sequence-regulated polymer construction,chemists have made great progress in the study of the relationship between polymer sequence structure and performance.For example,they found that the sequence can affect the optical properties,assembly behavior,solubility and antibacterial properties of polymer.My dissertation focuses on the construction of sequence-regulated polymer,including:(1)We successfully prepared sequence-controlled polymers with succimide motifs using latent-monomer strategy.The functionalization of the sequence-controlled poly mers is realized through post-modification;(2)Through combination of the thiol-maleimide Michael addition reaction and orthogonal protection-deprotection strategy,we obtained four sequence-defined polymers containing azobenzene in main chain,and the relationship between polymer sequence structure and properties was initially explored.The specific research contents are as follows:(1)Firstly,we prepared sequence-controlled polymers with similar molecular weights and maleimide(MI)contents by reversible addition-fragmentation chain-transfer(RAFT)polymerization of styrene and furan-protected maleimide.The thermal properties of sequence-controlled polymers were explored.The results demonstrated that the introducing of polar groups(MI)into the PS led to Tg increasing of the polymers,and different St/MI sequence copolymers convey different Tgs,depending on the different positions of St and MI units in the polymer chain.Secondly,1-bromopropane,n-propanol,methoxypolyethylene glycols and monomer with azobenzene group were respectively modified to succimide motifs along the polymer chain by nucleophilic substitution and Mitsunobu condensation reactions.1H NMR,SEC,MALDI-TOF MS,and FT-IR were used to verify the efficiency of post-modification.Meanwhile,the thermal properties and photoisomerization behavior of functional polymers containing azobenzene were explored.The results indicated that the introduced azobenzene groups(linked via an alkyl spacer)led to a strong decrease of the Tg.However,due to the low amount of azobenzene in the polymer chains,the photoisomerization rate constants of different sequence-controlled functional polymers were mostly similar.(2)Two monomers with furan-protected maleimide and thioacetate group were firstly designed.Then,using the high-efficiency thiol-maleimide Michael addition and orthogonal protection-deprotection strategy,four sequence-defined polymers(ABB?BAB?A8B?4BA4B)with monodispersity of molecular weight containing azobenzene in main chain were obtained.The successful preparation of sequence-defined polymers were verified through1H NMR,MALDI-TOF MS,and SEC.Finally,we preliminarily explored the thermal properties and photoisomerization behavior of the sequence-defined polymers containing azobenzene in main chain.The results indicated that different sequence-defined polymers convey different Tgs,depending on the different positions of azobenzene group in the polymer chain.Due to only one azobenzene group was introduced into the polymer chain,the photoisomerization rate constants of different sequence-defined polymers were mostly similar.