Study On The Synthesis And Self-assembly Of Nucleobase-functionalized Polymers

Nucleobase-functionalized polymer,which contained organic main chain and nucleobase side chain is a kind of macromolecular compound.And it has molecular structures and physiological characteristics that similar to DNA.In addition,chemists can also manipulate the molecular functions of such polymers by varying their macromolecular backbones and nucleoside unit structures.Therefore,the exploitation and development of nucleobase-functionalized polymers have attracted widespread attention in the scientific community.In this article,we have synthesized and prepared three major series of chiral nucleobase monomers,and then prepared three types of nucleobase-functionalized polymers,those were optically active nucleobase-functionalized polynorbornene,olefin-bridged oligodeoxynucleosides and heterodinucleoside polytriazoles respectively through ring-opening metathesis polymerization(ROMP),acyclic diene metathesis polymerization(ADMET)and azide-alkyne cycloaddition polymerization(CuAAC).The idiographic research contents will be discussed from the following three aspects:(1)Chiral cores can be used to build nucleobase-functionalized polymers with double-helical self-assembly structures.In this thesis,we separately designed and synthesized adenine-,thymine-,guanine-and cytosine-functionalized optically active norbornene monomers,which can form hydrogen-bonded complexes through the complementary nucleobases among those monomers.After ring-opening metathesis polymerization(ROMP)of the obtained monomers and complexes,the optically active nucleobase-functionalized polynorbornenes were given.High-resolution transmission electron microscopy(HRTEM)clearly showed that the optically active adenine-thymine-functionalized polynorbornene could self-assemble into double-helix nanostructures.In addition,computer simulations and a2D-NOESY experiments further proved that this helical double-stranded polynorbornene tends to form a copolymer with alternating adenine and thymine units.(2)The regio-controlled and regio-uncontrolled polymerization modes determine the self-assembly behaviors of the prepared nucleobase-functionalized polymers.In this thesis,we have designed and prepared two types of olefin-bridged oligodeoxynucleosides through acyclic diene metathesis polymerization(ADMET).First,the 3'-OH and 5'-OH groups of chiral deoxythymidine and deoxyadenosine monomers were functionalized with either two allyl units or allyl and acryloyl units to give the corresponding monomers,respectively.Then,the obtained chiral deoxynucleoside monomers were subjected to ADMET polymerization to provide either regio-uncontrolled olefin-bridged oligodeoxynucleosides with poor E/Z selectivity or regio-controlled olefin-bridged oligodeoxynucleosides with E selectivity.These two prepared olefin-bridged oligodeoxynucleosides with different macromolecular structures self-assembled into spherical nanostructures and helical filamentous nanostructures,respectively.(3)The 1,4-regioregular copper(?)-catalysed[3+2]azide-alkyne cycloaddition polymerization(CuAAC)can be used to prepare double-stranded nucleobase-functionalized polymers with alternating nucleobase sequences.In this thesis,we designed and synthesized two azide-alkyne-functionalized chiral heterodinucleoside monomers respectively,which could further form hydrogen-bonded complexes through self-complementary nucleobases.After CuAAC polymerization on these complexes,two double-stranded heterodinucleoside polytriazoles with alternating nucleobase sequences were obtained,which could be observed the self-assembled obvious helical filamentous nanostructures under transmission electron microscopy(TEM).In conclusion,we have designed and synthesized three major series of chiral nucleobase monomers,and obtained a series of nucleobase-functionalized polymers by using different polymerization methods on these chiral nucleobase monomers in this thesis.Subsequently,the molecular structures and self-assembly properties of these nucleobase-functionalized polymers were studied by 2D ~1H,~1H NOESY,ultraviolet and visible spectroscopy(UV-vis)circular dichroic spectroscopy(CD)and transmission electron microscope(TEM),et al.,and clarified the chiral transmission and amplification mechanism in the polymeric processes:When the polymeric chain amplified direction is different from that of chiral twisting force of chiral nucleobase monomer,the prepared polymer can self-assemble into the spherical nanostructure;And when the polymeric chain amplified direction is the same as that of chiral twisting force of chiral nucleobase monomer,the prepared polymer can realize the transfer and amplification of chirality in chiral nucleobase monomer,and self-assemble into the helical filamentous nanostructure.