Post-modification And Functional Applications Of Conjugated Polymers With Activated Ester

In nature,every species exist well after the evolution and making adjustment to the environment.During the evolution process,the expression of external characters were determined by the gene(DNA and RNA,fewer depend on protein).The knowledge from biology textbook told us that the genetic recombination or variation was only attributed to the increase or decrease or changes the order of the base pairs.Such changes didn't change the structure of the main chain.Although the final state is stable in thermodynamics,it consumes huge energy from small molecules to polymers.At the same time,the entropy derease caused by the connection of small molecule to polymers is acosmia with nature.As a result,there is a strategy in nature:the change or enriched functions are realized by the combination of multiple pendants while with relative onefold main chain.Till now,fluorescent polymer materials have drawn attention in organic device,chemical sensing and biological imaging,while the properties of optoelectric functional polymers are tuned via the change of the monomer structures.In other words,if we want to change the structure and functions of a conjugated polymer,we have to synthesize the monomer from the beginning.This is quite different with the nature process.In this thesis,combined the previous work on PDSAs in our group and enlightenment from nature,together with the good fluorescent property of poly(disubstituted acetylene)s(PDSAs)and poly(phenylene ethylnylenes)(PPEs),we prepared the two kinds of polymer precursors with reactive center.The polymer can be further modified and functionalized.We firstly prepared a PDSA precursor carrying pentafluorophenyl ester directly by metathesis polymerization under the WCl6-Ph4Sn catalyst systems.The ester was activated due to the electron-withdrawing effect of pentafluorophenyl.The activated ester can react with nucleophilic reagents under mild conditions.The second polymer precursor carrying terminal alkyne was prepared by polymer precursor and propargylamine.Next,we prepared PDSAs containing triazole part by the second polymer precursor and azide molecule.The two steps of post-polymerization modification(PPM)were both in high efficiency,complete transformation,with high yield and under mild conditions.What's more,the obtained polymers were in yellow-green fluorescence and had good quantum yield(QY).Next,we continued using PO as polymer precursor,the functional second PDSAs precursor carrying amine and tertiary amine pendants were prepared successfully.Based on such polymers,the graphene oxide(GO)/PDSA hybrids were fabricated.The hybrid and precursor polymer gave different maximum emission wavelength in different state.We attributed this phenomenon to coplanar induced red-shift emission.The PDSAs carrying tertiary amine group exhibited pH response behavior,this is due to the different degree of protonation in different pH value.Furthermore,the PDSAs carrying tertiary amine pendant can be derivated to zwitterionic PDSAs,showing water solubility properties.After the preparation of water soluble zwitterionic PDSAs,we continued preparing two kinds of PDSAs carrying cationic and anionic pendant,respectively.In order to compare the water dispersion ability of the three kinds of PDSAs,we analyzed the 'H NMR spectra and actual dispersed weight of polymers in water.The order of water dispersion is as follows:zwitterionic PDSAs>anionic PDSAs>cationic PDSAs.Furthermore,we studied the relationship of fluorescence intensity and concentration of the three kinds of PDSAs.At lower concentration,PL intensity kept linear relationship with polymer concentration.While in higher polymer concentration,the PL intensity increased slowly or decreased,respectively.After the analysis,we believed that the formation of intra-chain excimer led the fluorescence quenching at higher concentration for PDSAs carrying zwtterionic pendant.Azobenzene is a functional group with optical active properties.We prepared PDSAs carrying azobenzene derivatives,together with the reported poly(monosubstituted acetylene)s(PMSAs)counterpart,to compare their properties.After the detailed study,two kinds of polymers showed photo-isomerization behavior under irradiation of UV lamp(365 nm),and this behavior had relationship with the steric x effect of the main chain.We utilized shorter wavelength(254 nm)to realize the reversion from cis to trans of azobeneze derivatives.Besides,the aggregate FL behavior of azobenzene-containing PDSAs was oppositely different with that of PDSA precursor.The latter exhibited aggregation enhanced emission(AEE)while the former one showed aggregation caused quenching(ACQ).This provided a convenient method to adjust the PL behavior.There have been reports about the chirality transfer from chiral pendants to main chain based on PDSAs.The previous work mainly focused on the opposite Cotton effect and circular polarized luminescence.Compared with the previous reports,there were some different properties for PDSAs carrying bulky enantiomers after PPM via activated ester strategy.The distinct differences included the reaction phenomenon,reaction degree,solubility,microscopic morphology and CD spectra.In order to investigate the reason,we calculated and optimized the molecular structure of the chiral pendants.The data showed that it met the demand for L style pendant to form intramolecular hydrogen bond,while the D style pendant can't.The distinct difference of their structures led to the different properties.At last,we prepared triple-bond copolymers containing tetraphenylethylene(TPE)via Sonogashira coupling polymerization.The introduction of activated ester can facilely prepare functional polymers.The precursor and modified polymers all showed AEE behavior.Also there were differences in turning point and threshold values for polymers in different solvent mixtures.The chirality can be transffered to main chain by introducing chiral pendants and the polymers exhibited the 'chirality amplification'effect.Modified by PEG chain,the hydrophobic-hydrophilic property of the polymers can be tuned.The precursor polymer and PEG-modified polymer showed distinct differences in contact angle and SEM test.What's more,the prepared polymers showed excellent properties in explosive detection.