Study On Chiral Assembly Of Achiral Polyfluorene And The Response To Ion

In this thesis.a range of achiral polyfluorene derivatives containing crown ether and amine groups were successfully prepared.The chiral assembly of achiral polyfluorene derivatives was achieved in single solvent system((R)-(+)-limonene,1R or(S)-(-)-limonene,1S),employing limonene as chiral solvent by controlling the temperature during assembly process.The effects of polymer structures,temperature and time on assembly of achiral polymers were investigated,and we further studied the response ability of the chiral assembly systems to corresponding ions.This thesis is devoted to the following two points:(1)The chiral assembly of side polar crown ether containing main-chain ?-conjugated polymer could be induced by pure nonpolar chiral limonene.However,PF8 could not performed similar chiral assembly in the similar experimental condition.After adding potassium ion,the CD signal of chiral assembly system became stronger;(2)In the amine group-functionalized polyfluorene system,chiral assembly of polymer is slow at the room temperature.However the addition of acetic acid into above system could enhance the assembly rate.The main research contents of this thesis are roughly described as follows:(1)Monomer,2,7-dibromo-9-(15-crown-4)-9H-fluorene containing crown ether,was synthesized through a series of organic reactions,and then three linear 7r-conjugated polymers with similar main-chain structures,including homopolymers poly(9,9-di-n-octylfluorenyl-2,7-diyl)(PF8),poly(9-(15-crown-4)-9H-fluorene-2,7-diyl)(PC4)and alternating copolymer PF8C4 were successfully prepared.The corresponding polymers was characterized by nuclear magnetic resonance(NMR),elemental analysis(EA)and gel permeation chromatography(GPC).The effects of polymer structures,temperature and time on assembly of achiral polymers were investigated,employing chiral limonene((R)-(+)-limonene or(S)-(-)-limonene)as chiral solvent.Furthermore we investigated the response of chiral assembly system to potassium ion preliminarily.The main research results are summarized as follows.1)Under the identical experimental conditions,PF8C4 aggregates showed apparent CD signal,but the CD intensity of PF8 was hardly detected in the similar experimental conditions.Other than that,the homopolymer PC4 was proved that it was undissolved in limonene.Alternating copolymer PF8C4 contains both flexible octyl chains and polar crown ether groups,which makes it dissolve and then aggregate in nonpolar chiral limonene at the same concentration and temperature.2)For PF8C4,temperature was an important factor in the formation of chiral aggregates.At relatively high temperature,polymer chains were difficult to aggregate effectively,and at relatively low temperature,acute reduction of CD signal was attributable to the formation of precipitation arising from rapidly cooling process.In addition,assembly time was also critical.In the early stage of assembly,gCD values of PF8C4 aggregates increased with cooling time,and then became stable with the further extension of time.3)After adding potassium ion to PF8C4 assembly system,an obvious increase of CD signal could be observed.It is because,?-? interaction was intensified by the formation of 2:1 sandwich complex between potassium ion and crown ether group.(2)Poly((9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene))was prepared by means of purification.The polymer was characterized by nuclear magnetic resonance(NMR)and gel permeation chromatography(GPC).The effects of temperature and time on assembly of achiral polymers were investigated,employing chiral limonene((R)-(+)-limonene or(S)-(-)-limonene)as chiral solvent.We explored the response of achiral PFN amine containing system to acetic acid preliminarily.The main reseearch results are summarized as follows.1)At different temperatures in pure chiral limonene,the UV spectra of polymer showed diverse changes.The obvious red-shift in UV absorption peak was observed at constant 20 ?,and clear signal appeared in circular dichroism spectrum,which indicated that ?-? stacking of PF chain took place at suitable temperature in chiral limonene.2)After adding acetic acid in fresh pure chiral limonene solution of PFN,chiral aggregates appeared quickly.In contrast with the system without acetic acid.chiral inversion was observed in circular dichroism spectrum.