Star-shaped polymer

Star-shaped polymers are the simplest class of branched polymers with a general structure consisting of several (more than three) linear chains connected to a central core. The core, or the center, of the polymer can be an atom, molecule, or macromolecule; the chains, or "arms", consist of variable-length organic chains. Star-shaped polymers in which the arms are all equivalent in length and structure are considered homogeneous, and ones with variable lengths and structures are considered heterogeneous.

Star-shaped polymers' unique shape and associated properties, such as their compact structure, high arm density, efficient synthetic routes, and unique rheological properties make them promising tools for use in drug delivery, other biomedical applications,thermoplastics, and nanoelectronics among other applications.

Star-shaped polymers were first reported by John Schaefgen and Paul Flory in 1948 while studying multichain polymers; they synthesized star-shaped polyamides. The next major publication regarding star-shaped polymers was in 1962 by Maurice Morton et al. Their research presented the first study demonstrating a method to create well-defined star-shaped polymers; this route was through living anionic polymerization. Many studies on the characteristics, syntheses, and applications of star-shaped polymers have since been undertaken and remain an active area of study.

Star-shaped polymers consist of a multifunctional center from which at least three polymer chains (arms) radiate. These arms can be chemically identical (homostars) or different (heterostars or Miktoarm stars). Additionally, individual arms may be composed of multiple polymers, resulting in star-block polymers or star copolymers. The unique properties of star-shaped polymers come from their chemical structure as well as the length and number of their arms.

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