Study On The Helical Induction Of Poly(phenylacetylene) With Biphenyl Side Groups

Helix is an asymmetric structure widely existed in nature.The complex helical molecular structure of biological macromolecules such as proteins,biological enzymes and DNA gives its magical and rich functions,supporting the operation of the living system.The research on the control of helical molecular structure is an important research content in the fields of chemistry,biology and pharmacy,and it is an indispensable part of the research and development in related fields.Polyphenylacetylene is a typical molecular polymer with a dynamic helical structure.Due to the instability of its dynamic helical structure,the helical structure can be changed by changing the external environment.In this paper,we synthesized polyphenylacetylene with different side chain structures,studing the effects of chiral molecules,temperature and solvent on the helical behavior of polyphenylacetylene,revealing the mechanism and influencing factors of helical behavior,preparing one-handed helical Polyphenylacetylene materials,and providing a theoretical basis for application in chiral recognition,asymmetric catalysis and so on.Three phenylacetylene monomers of M1,M2 and M3 were synthesized.The intermediate compounds and monomers were characterized by nuclear magnetic resonance(NMR)and infrared spectroscopy(IR).Using Triethylamine /[Rh(NBD)Cl]2 system,the corresponding phenylene acetylene homopolymers P1,P2 and P3 were prepared.The molecular weight of the polymers were determined by the gel permeation chromatograph(GPC).Through analyzing and comparing CD and UV spectra,the process of chiral inducing poly(phenylacetylene)precursor by chiral amines was explored.The effects of solvent,temperature and chiral inducer were investigated.The mechanism helical induction on homopolymer was studied.The results show that bishydroxyl is an important structure for transmitting chiral signals.Only ?-? stacking effect can not efficiently transmit chiral signals.That is,the bishydroxy structure is a key factor in the formation and transmission of the helical structure.In the R-phenylethylamine system,P1 showed good thermal stability in toluene and chloroform.In the R-cyclohexylethylamine system,P1 has good thermal stability in chloroform,and helical inversion occured in toluene with temperature increase.The chiral induction on P1 shows a chiral amplification effect.The helical structure of P3 was stable in the organic solvent.When the basic ammonium was added,deprotonation occurs,which destroys the original intramolecular hydrogen bond,so that the one-handed helical structure disappears.