Synthesis And Thermal Response Of Poly(Phenyl Acetylene) With Bishydroxy Groups In Side Chains

Poly?phenyl acetylene?is a typical dynamic helix polymer.In recent experimental studies,we have found a polyphenylene acetylene system with a thermally controlled,controlled critical one-way helix transition temperature and another thermally stable polyphenylacetylene system under homogeneous conditions.In this paper,We designed and completed two kinds of achiral monomers,dodecyloxy-3,5-dimethylolphenylacetylene?M1?and 4-?dodecyloxy?-4'-ethynyl-[1,1'-biphenyl]-3,5-dimethylol?M2?and the correspond-ing structural characterization.In the triethylamine/[Rh?nbd?Cl]₂ catalyst system,the two monomers were polymerized to produce non-optically active polyphenylenevinylene derivatives P1 and P2.By studying the CD and UV-vis of polymer/chiral molecule/solvent ternary systems with the change of temperature,solvent and chiral inducer,Thermal responsiveness of materials under different systems.Homopolymer P1 was conformed in n-Hexane,toluene,tetrahydrofuran?THF?,and chloroform solvents by heating the system in a solvent/chiral phenylethylamine and solvent/R,R-cyclohexanediamine,showed strong CD signal and UV absorption and had criticalone-handedhelicesin n-hexane/R-phenylethylamine,toluene/R,R-cyclohexanediamine and tetrahydrofuran/R,R-cyclohexanediamine.This result shows that in the presence of a chiral inducer,heating causes P1 to be induced as a one-handed helical polymer.The temperature change can effectively affect the conformational transition of the P1 molecule while the polarity of the solvent and the polarity of the chiral inducer can also affect P1 conformational changes effectively.This unique thermotropic chiral induction and solvent-induced spiraling is caused by competition in the system for hydrogen bonds in different solvent polarities at different temperatures.Homopolymer P2 compared to P1,phenylacetylene pendent one more benzene ring,which makes the distance between the hydroxyl side groups farther,the polymer dissolved in different polar solvents,the polymer side chain hydroxyl neither of them formed a hydrogen bond structure,which is the homopolymer P2 was a meso-loose,fully cis-trans structure in solution.When small chiral molecules are added,the small chiral molecules combine with the hydroxyl groups of the polymer to form hydrogen bonds,which will induce the regular?-?stacking of the biphenyl structure of the homopolymer P2 side chains.As the temperature increases,the?-?stacking structure of the side chain biphenyl structure of the homopolymer P2 is subjected to a temperature test.In the toluene/chiral inducer and chloroform/chiral inducer have better thermal stability,but in tetrahydrofuran solution,due to the strong polarity of the solvent,in the presence of different chiral inducer during the heating process P2 induces different changes in the helical structure.