Dendrimers and Hyperbranched Polymers as Promising and Versatile Additives in Polyolefins
Aanchal Jaisingh, Leena Nebhani
Abstract
Hyperbranched polymers (HBPs) are globular macromolecules with nonuniformly grown branches terminating in functional groups. Dendrimers are like HBPs but have a perfectly oriented structure with branches arising from the central core in a uniform fashion. The numerous functional groups present in dendrimers and HBPs can be tailored by organic modification for catering to specific applications. Over the years, these macromolecules have been tested as additives for polyolefins, particularly polypropylene (PP) and polyethylene (PE). PP and PE are the most consumed types of plastics today because of their attractive properties, such as low cost, lightweight, good chemical and electrical resistance, etc. To utilize polyolefins to their maximum potential, certain external agents called additives are incorporated in polyolefin matrices to make them more functional for engineering applications. Dendrimers and HBPs have been extensively known and acknowledged for their applications in drug delivery, wastewater treatment, bioimaging, catalysis, etc. This review exclusively accounts for the role of dendrimers and HBPs as additives in polyolefins, including processing aids, nucleating agents, flame retardants, and antioxidants, to improve thermoxidative and color stability, dyeability, and paintability, as well as mechanical, rheological, and barrier properties of polyolefins. We also review the role of unique architecture and characteristics of HBPs and dendrimers in having an edge over their analogous linear counterparts in improving multiple polyolefin properties simultaneously and their ability to increase the efficiency of conventional additives.