Structure–Property Relationship of Regioregular Polytriazoles Produced by Ligand-Controlled Regiodivergent Ru(II)-Catalyzed Azide–Alkyne Click Polymerization

Exploitation of new polymerization with selectivity is of significance to the preparation of functional polymers and the study of their structure–property relationship. In this work, we successfully developed an efficient Ru(II)-catalyzed azide–alkyne click polymerization (RuAACP), of which the regioselectivity can be switched by the ligands on the Ru(II) catalysts. With RuH2(CO)(PPh3)3 as catalyst, 1,4-regioregular polytriazoles (PTAs) with high weight-average molecular weights (Mw up to 15300) and high 1,4-regioregularities (the fraction of 1,4-isomer, F1,4 up to 100%) were produced in satisfactory yields (up to 97.6%). In contrast, Cp*Ru(PPh3)2Cl-catalyzed AACP facilely yielded (up to 98.3%) 1,5-regioregular PTAs with high Mw (up to 15520) and F1,5 (up to 100%). All the obtained PTAs exhibit good solubility and high thermal stability. The glass transition temperature (Tg) of 1,4-regioregular PTA is much higher than that of its 1,5-regioregular counterpart, revealing the considerable effect of the regiostructure on their Tg. Both 1,4- and 1,5-regioregular PTAs containing tetraphenylethene moieties in their backbones show aggregation-induced emission features. In addition, the impact of regiostructure on the light refractivity of the PTAs was also investigated, and 1,4-regioregular PTA possesses higher refractivity indices than 1,5-regioregular PTA.