Well-defined benzoxazine/triphenylamine-based hyperbranched polymers with controlled degree of branching

Abstract

Well-defined thermally polymerizable hyperbranched polymers (TPA-BZs) containing various numbers of triphenylamine (TPA) and benzoxazine (BZ) units have been prepared using a "click-like" reaction concept, through one-pot Mannich condensations of 4-(bis(4-aminophenyl)amino)phenol (TPA-2NH2-OH, as the AB2 branching groups), aniline (as the focal groups), CH2O, and phenol in 1,4-dioxane, with a unique feeding approach. Two design strategies for the chemical construction were applied: (i) simple hyperbranched TPA-BZs, such as those containing one or three TPA units, developed from the focal or the terminal group direction to form the resultant monomers; (ii) three dendritic TPA-BZs containing four TPA units possessing different degrees of branching (DBs) for the conformation study. The exothermic temperature for the dendritic TPA-BZs decreased upon increasing the DB. The bathochromic shifts of the dendritic TPA-BZs increased upon increasing the number of TPA units, in UV-Vis absorption and PL emission spectra, presumably because of an increase in the effective conjugation length. In addition, the polymerized dendritic TPA-BZ DG1 possessed thermal properties superior to those of the hyperbranched TPA-BZ polybenzoxazines, possibly because the segmental mobility in the polymer network was restricted by the dendrimer core group and because of its symmetrical construction. The hyperbranched TPA-BZ possessed unique photophysical properties, suggesting potential applications in optoelectronic devices.