Hyperbranched Poly(silylenephenylenes) from Polycyclotrimerization of A₂-Type Diyne Monomers:  Synthesis, Characterization, Structural Modeling, Thermal Stability, and Fluorescent Patterning

A group of hyperbranched poly(silylenephenylenes) (hb-PSPs) were synthesized in high yields (up to 100%) by TaBr5-catalyzed polycyclotrimerization of A2-type monomers of silylenediynes [HC⋮C−C6H4−Si(CnH2n+1)2−C6H4−C⋮CH, n = 2, 4, 6]. The hb-PSPs are completely soluble in common organic solvents such as chloroform, toluene, and THF. Spectroscopic and modeling studies confirmed that the polymers had formed via a [2 + 2 + 2] cyclotrimerization mechanism. Analysis of the triple-bond conversion processes led to the establishment of a relationship between the degree of branching and the fraction of dendritic unit. Computational simulation shed light on the real topological structures of the hb-PSPs. The polymers lost little weights when heated up to 480 °C and carbonize in high yields (up to 71%) after pyrolysis at 800 °C. The hb-PSPs possess a unique σ−π conjugated electronic structure and emit strong violet-blue light upon photoexcitation. The triple bonds on the peripheries allowed the thin films of the polymers to be readily photo-cross-linked, generating fluorescent photoimages in high resolutions.