Synthesis And Properties Of Helical Poly(Phenylacetylene)s Functionalized By L-Proline Peptide Derivatives

Substituted helical poly(phenylacetylene)s,as a branch of the substituted polyacetylenes,maintain the conjugated structure of polyacetylene with alternating single and double bonds,and the benzene ring in the side chain endows the side chains with stronger?-?interaction,which is beneficial to stabilizing the spiral of the polymer main chain and making it difficult to be destroyed.Due to the dynamic helical structure of the polymer main chain,poly(phenylacetylene)s can be stimulated by the external stimuli,such as solvent polarity,temperature,p H,additives and so on.These unique structures and properties make poly(phenylacetylene)s have broad application prospects in many fields such as chiral resolution,asymmetric catalysis,molecular recognition,intelligent materials and luminescent materials.Proline is the only proteinogenic amino acid that contains secondary amines.When proline is part of a peptide chain,it does not produce hydrogen bonds.The unique PPII helical structure of L-proline polypeptide plays an important role in signal transduction and immune response and is also considered as a local conformation of protein in disorder.In this thesis,according to the characteristics of the helical poly(phenylacetylene)derivatives,the unique secondary structure of L-proline peptide was introduced to the structure of the helical poly(phenylacetylene)s and the chiral recognition abilities and stimuli responsive properties of the polymers were investigated.PA-Pro₂-ee and PA-Pro₂-Boc with different L-proline dipeptide were synthesized by Sonogashira coupling,elimination and amine condensation reaction,respectively,and were polymerized in THF using Rh(nbd)BPh₄ as the catalyst to obtain the corresponding poly(phenylacetylene)s PPA-Pro₂-ee and PPA-Pro₂-Boc.FT-IR,NMR,GPC and Raman spectra were used to characterize the structures of the monomers and polymers.The results showed that the polymers possessed cis-transoidal conformation.The results of optical rotations and CD spectra showed that the main chain of the polymers exhibited helical conformation,and the helical structure was controlled by solvent,temperature and L-proline dipeptide derivatives.In DMAc,the two polymers had the opposite CD signals where PPA-Pro₂-ee had higher CD signal intensity than PPA-Pro₂-Boc,indicating that the two polymers had two different helical conformations and PPA-Pro₂-ee might have higher helical regularity.Chiral stationary phases(CSPs)were prepared and the influence of coating solvent and different bond modes of L-proline dipeptide derivatives in the side chains on chiral recognition abilities were characterized by HPLC.The chiral recognition properties of the polymers depended on different helical structures,coating solvents and different bond modes of L-proline dipeptide derivatives in the side chain.PPA-Pro₂-ee showed more extensive chiral selectivity,while PPA-Pro₂-Boc showed more specific recognition of racemates N,N'-(cyclohexane-1,2-diyl)dibenzamide(8)and N,N'-diphenylcyclohexyl-1,2-diformamide(9).The separation factors of these two racemates on PPA-Pro₂-Boc were higher than those on commercialized polysaccharide-based columns AD,OD,AS and OJ-H.Eight phenylacetylene monomers containing different lengths of L-proline peptide were synthesized by Sonogashira coupling reaction and iterative amino-acid condensation reaction.Optical rotation and CD spectra showed that the monomers formed a secondary helical structure with the increase of the length of L-proline peptide.2D NMR spectra showed that the left-handed all-trans PPII helical structure could be formed by phenylacetylene monomers containing more than six L-proline units.CHCl₃ was used as coating solvent to prepare coated-type CSPs,and the influence of L-proline peptide on the chiral recognition abilities of the CSPs were investigated.The results showed that the chiral recognition abilities of CSPs were improved with the increase of length of L-proline peptide.Eight poly(phenylacetylene)derivatives with different lengths of L-proline peptide were obtained by polymerization of the monomers using Rh(nbd)BPh₄ as the catalyst.FT-IR,NMR,GPC and Raman spectra were used to characterize the structures of the polymers.The results showed that the polymers had cis-transoidal conformation.The results of optical rotations and CD spectra showed that the main chains of the polymers possessed helical conformation,and the helical structures were controlled by solvent,temperature and L-proline peptide lengths.The morphology of PPA-Pro₃-e was observed by AFM,the information of its spiral direction,pitch and chain arrangement were obtained.The chiral recognition abilities of CSPs were investigated.The results showed that the chiral recognition abilities of CSPs were improved gradually with the increase of the length of L-proline peptide in the side chain.CSP-PPA-Pro₉-e showed the best chiral recognition ability.For racemates 2,3-diphenyloxirane(2)and N,N'-diphenylcyclohexyl-1,2-diformamide(9),the chiral recognition ability of CSP-PPA-Pro₉-e was better than several commercial chiral columns.The external stimulus response properties of PPA-Pro₁-e,PPA-Pro₂-e,PPA-Pro₃-e,PPA-Pro₄-e,PPA-Pro₅-e and PPA-Pro₆-e to Ba²⁺,Co²⁺,Ni²⁺,Zn²⁺and Al³⁺were investigated.The results showed that the helical structures of the polymer backbones were tuned by the types of metal ions and the different addition equivalents.The different L-proline peptide lengths in the side chains also responded differently to the metal ions,which can be expressed as helical inversion or chirality attenuation.FT-IR spectra showed that the tuning of helical structures of polymer backbones were caused by the chelations of carbonyl groups in the polymer side chains and the metal ions.The morphologies of a series of supramolecular assemblies,including spheres,ribbon assemblies,films,fibers,and nanogel-like assemblies were observed by SEM which were conducted via helical polymer-metal complexes(HPMCs)method.The size of the microspheres increased with the increase of the addition amount of metal ions,indicating that the morphology and size of the supramolecular assemblies can be adjusted by the type and amount of metal ions.