Fully branched hyperbranched polymers with a focal point: analogous to dendrimers

Abstract

A fully branched hyperbranched polymer with a focal point has been prepared by superelectrophilic polycondensation of AB₂ monomers with a core with six functional arms (B₆′) in a slow addition manner. To reduce the chance of the homopolymerization of the monomers, the acenaphthenequinone group with higher reactivity was chosen as B′ for the core and the isatin group with lower reactivity as B in the monomer. The obtained polymers were characterized by ¹H NMR, ¹³C NMR, TGA and GPC. The thermo-decomposition temperature of the polymer could reach 400 °C. The NMR spectra indicated the 100% branching degree of the hyperbranched polymers and the successful introduction of the core. The proportions of the terminal/dendritic groups in the hyperbranched polymers with low monomer/core feeding ratio were evaluated through NMR and GPC data respectively. Through comparison and analysis it was revealed that most of the hyperbranched polymers possessed quasi-spherical structures. The molecular weights of the hyperbranched polymers increased almost linearly with the feeding ratio of the monomer to the core and the polydispersities of the polymers were greatly influenced by the monomer concentration. At the optimal monomer concentration, the main parts of the GPC curves were symmetric and narrow. Although there were traces of faint shoulder, the molecular weight distributions of the polymers were still acceptable. The branching degree of 100%, controllable molecular weights, narrow distribution, plus the quasi-spherical and hierarchical architectures of cores, dendritic and terminal units made the fully branched polymer with a focal point analogous to dendrimers in all respects, offering a highly efficient option to fabricate dendrimer substitutes.