Synthesis And Chiroptical Properties Of Optically Active Chiral Polymer

In recent years,the design and synthesis of new chiral polymers with different functional groups have been a hotspot in the field of polymer research.There are two commonly used methods for obtaining chiral polymers,one is obtained by the use of chiral monomer and achiral catalyst;the other is by the use of achiral monomer and chiral initiator or chiral additives.Based on this,a new class of dipropynylfluorene derivatives with chiral pendant groups was designed and synthesized and studied.The chiral polymers with optical activity were obtained.In addition,the artemisinin derivatives are used as chiral free radical initiators to initiate the polymerization of achiral monomers to prepare chiral polymers.The details are as follows:1 A new type of dipropynylfluorene monomer with oxazoline pendant was synthesized:?S?-2-?9-dipropynyl-fluoren-2-yl?-4-isopropyl-4,5-dihydrooxazoline [?S?-1],?R?-2-?9-dipropynyl-fluoren-2-yl?isopropyl-4,5-dihydrooxazoline [?R?-1],?S?-2-?9-dipropynyl-fluoren-2-yl?-4-tert-4,5-dihydrooxazoline [?S?-2],?S?-2-?9-dipropyn yl-fluoren-2-yl?-4-phenyl-4,5-dihydrooxazole [?S?-3].2 Using [Rh?nbd?Cl]₂ as the catalyst,the polymerization reaction and the chiral properties of the chiral monomer under different solvents were studied.The results shows that the polymerization reaction can proceed smoothly;the yield and the number average molecular weight?Mn?is low;13C-NMR showes that the polymer backbone mainly forms a six-membered ring structure;circular dichroism?CD?shows that poly-?S?-2 and poly-?S?-3 may have a single-handed helix conformation.3 The asymmetric oxidative coupling polymerization of?1?monomer was performed using CuCl-TMEAD catalytic system.A good yield and a number average molecular weight were achieved.1H NMR showed that the polymer had high stereoregularity.CD and XRD indicated that the polymer backbone had chiral helix characteristics,while the atomic force microscopy?AFM?showed that poly-?S?-2-2was the right helix structure.The temperature change CD shows that the helical structure of poly-?S?-2-3 has obvious temperature response characteristics in the solution.The CPL of poly-?S?-2-2 indicates that the polymer has glum =-1.1 x 10-3.4 In addition,three kinds of artemisinin derivatives,including artemether,dihydroartemisinin and artesunate,were used as free radical initiators,the asymmetric polymerization behavior of N-substituted Itaconimides and N-vinylcarbazoles wereinvestigated.The result shows that the three initiators can successfully initiate the monomer to obtain the optically active chiral polymer with high yield and number average molecular weight.The results revealed that the optical activity of the polymer is not dependent on the initiator chain and indicates that the main-chain of the polymer are in a chiral environment induced by the effect of the chiral initiator.