Synthesis Of Sequence-Controlled Polymers With Different Topologies And Their Applications

The sequence of monomer units in a polymer chain and the topological structure of the polymer play an important role in the performance of the polymer.In recent years,the synthesis and application of sequence-controlled polymer and topological polymers have attracted considerable attention.Click reaction is characterized by high efficiency and selectivity,which has been widely used in the synthesis of sequence-controlled polymer.In this paper,a strategy combining quantitative reactions and reversible-covalent chemistry is proposed for synthesizing sequence-controlled polymers with different sequences;two different sequence-controlled polymers are synthesized by controlling the reaction conditions of efficient reactions;sequence-defined cyclic polymers are fabricated from molecular modules with definite sequences;and fluorescent polyamidoamine is synthesized from non-fluorescent monomer and used for efficient gene delivery and biological imaging.The specific research results are listed as follows:1.A new strategy combing quantitative reactions and reversible-covalent chemistry is proposed for sequential synthesis of sequence-controlled polymers with different sequences.Using a Michael addition reaction between acrylate and thiol,an aminolysis reaction of five-membered cyclic dithiocarbonate and a thiol substitution reaction of bromomaleimide and thiol,AB-,AB'C-and AB'CD-sequenced molecules are synthesized via sequential monomer additions,respectively.These three molecules all have furan-protected maleimido group at one end,and the other ends are amine,thiol and anthracene groups,respectively.Due to the fact that the furan-protected maleimido group can be efficiently transformed to maleimide group at high temperature via retro Diels-Alder reaction,AB-,AB'C-and AB'CD-sequenced molecules polymerize into sequence-controlled polymers with corresponding sequences at 120 ?.Through this strategy,the sequence of synthetic sequence-controlled polymers can be controlled via adding different monomers and adjusting reaction condition.2.Sequence-controlled polymers with different sequences are synthesized by controlling the reaction conditions.Three efficient reactions are used,including the metamorphosis reaction between furan-protected maleimido and anthracene groups,copper catalysed azide/alkyne cycloaddition(CuAAC)reaction,and oxime formation reaction between tert-butylcarbonate(Boc)-protected aminooxy and aldehyde groups,and their reaction conditions are different,requiring high temperature,copper salt and acidic condition,respectively.On the basis of three quantitative reactions,three monomers are synthesized,and they can't react with each other at room temperature,which ensures that three monomers can coexist stably in a pot.ACB-and BAC-sequenced polymers are successfully synthesized by controlling the reaction conditions.3.Sequence-defined cyclic oligomers are fabricated from molecular modules with definite sequences.AB-and ABC-sequenced molecules are synthesized through thiol-halide substitution reaction and isocyanate-hydroxyl reaction,and the end of two molecules can transform into alkyne group through orthogonal deprotection,and the another end can become into azide group via azidation.After three cycles of deprotection,azidation and coupling reactions,two molecular modules can envolve into AB-16mer and ABC-24mer oligomers via interative exponential growth.Through further orthogonal deprotection and azidation reactions,the two ends of AB-or ABC-sequenced oligomers are modified with azide and alkynyl groups,repectively.Moreover,sequence-defined cyclic polymers are readily synthesized in high dilution by copper catalyzed azide-alkyne cycloaddition(CuAAC)cyclization reaction.4.A fluorescent branched polyamidoamine is synthesized from non-fluorescent monomers for efficient gene delivery and biological imaging.AB2 type of monomer with furan-protected maleimido and amino groups was synthesized.At high temperature,branched polyamidoamine containing amino-succinimide groups was synthesized via polycondensation reaction between the released maleimide group and amine group.The synthesized polymer can emit green fluorescence under the excitation of ultraviolet light,and gene transfection ability and intracellular bioimaging of this novel polyamidoamine are investigated.