Two regioregular poly(p-phenyleneethynylene-alt-m-phenyleneethynylene)s bearing (-)-trans-myrtanoxyl side groups with different substitution patterns were designed and synthesized

e.g. Myr-PMPE-1 and Myr-PMPE-2.In order to obtain regioregular polymer

a novel AB type monomer 1-((5-bromo-2-myrtanoxyphenyl)ethynyl)-4ethynyl-2

5-myrtanoxybenzene and a novel AA type monomer 2

2′-(2

5-dimyrtanoxy-1

4-phenylene)bis(ethyne-2

1-diyl)bis(4-bromo-1-myrtanoxybenzene) were designed and synthesized by the strategy based on the different activity between bromo and iodo-benzene in Sonogashira reaction.By Sonogashira polymerization

the AB type monomer gave Myr-PMPE-1

in which the side chiral groups were distributed uniformly along the backbone.On the other hand

the obtained AA type monomer was polymerized with 1

4-diethynyl-2

5-dimyrtanoxybenzene to give Myr-PMPE-2

in which the distribution of the side chiral groups was alternatively crowd and loose.Both of these two polymers showed no CD signal in solution because of their good solubilities.Then

the investigations of chiroptical properties of these two polymers were carried out in the form of spincast films.The films were annealed above the glass temperature of the corresponding polymer

and the effects of annealing temperature and time on the properties of the films were investigated by UV-Vis absorption

fluorescence and circular dichroism spectra.The results showed that annealing treatment had no significant effect on the properties of Myr-PMPE-1

including UV-Vis absorption

fluorescence and optical activity.The maximum absolute value of dissymmetry factor (|gmax|) was 1.62×10-4. On the other hand

annealing treatment significantly affected the properties of Myr-PMPE-2.Without annealing or being annealed below 100℃

the Myr-PMPE-2 films showed almost no Cotton effect.In contrast

when annealed above 120℃

the absorption and emission of MyrPMPE2 film slightly red shifted with increasing annealing temperature and annealing time

and most importantly

the intense of CD signals increased significantly

and the optical activity of Myr-PMPE-2 films increased obviously.After annealing at 140℃ for 4 h

|gmax|of Myr-PMPE-2 film was up to 3.07×10-3

about one order of magnitude higher than that of Myr-PMPE-1 film.These observations indicate that the substitution pattern of the chiral side groups has significant effect on the chiroptical properties of chirally substituted conjugated polymers.The obtained results can contribute to the design of chiral conjugated polymers with high optical activity.