Synthetic methodologies for the preparation of highly branched polymers

Highly branched or hyperbranched (hb) polymers possess many interesting properties such as compact structures, limited or no chain entanglement, lower viscosity, enhanced solubility in solvents, and much higher chemical reactivity due to the large number of chain ends. They are of great potential to various applications including photoelectric materials, nanomaterials, coatings, adhesives, modifiers, drug delivery and so forth. Therefore, facile and practical synthetic methodologies to design well-defined functional hb polymers are highly needed.;In this dissertation, based on different monomers, a variety of novel synthetic routes have been developed to prepare hb polymers. For example, using the same lipoic acid-derived monomer, reductively degradable and non-degradable hb polymers were synthesized under different reaction conditions. The chemistry included the ring-opening radical polymerization of cyclic disulfides or the radical or ionic step-growth thiol-ene reactions. The second part is the design and preparation of cyanoacrylate-based polymers. In the presence of di-vinyl crosslinkers and suitable chain transfer agents (CBr4), polycyanoacrylates with hb structures could be synthesized. The last part of this dissertation discusses the use of hypervalent iodine (III) (HVI) compounds in polymer synthesis. In particularly, a heterocyclic HVI compound, chloro benziodoxolone, could not only serve as an initiator, but also participate in transfer reaction to the propagating radicals. When di or multi-vinyl crosslinkers were added to the mono-vinyl monomer, the radical copolymerization afforded hb polymers prior to gelation. Overall, this dissertation is focused on these three topics, and the synthetic routes, characterization, and appropriate functionalization of various hb polymers will be presented.