For Heteroarm polymers, increasing the molecular weight of soluble chains increases the overall solubility of the star. These self-assembly properties have implications for solubility of the whole star polymers themselves and for other solutes in solution. Heteroarm polymers have been shown to aggregate into particularly interesting supramolecular formations such as stars, segmented ribbons, and core-shell-corona micellar assemblies depending on their arms' solubility in solution, which can be affected by changes in temperature, pH, solvent, etc. Increasing the number of functional groups while retaining the same molecular weight decreases aggregation numbers. The addition of functional groups to the arms of star-shaped polymers as well as selective solvent choice can affect their aggregation properties. Generally, star-shaped polymers have higher critical micelle concentrations, and so lower aggregation numbers, than their analogous, similar molecular weight linear chains. The unique self-assembly properties of star shaped polymers make them a promising field of research for use in applications such as drug delivery and multiphase processes such as separation of organic/inorganic materials. In addition, star-shaped polymers exhibit lower melt temperatures, lower crystallization temperatures and lower degrees of crystallinity than comparable linear analogues. This is due to the increased repulsive interactions that occur as a result of a greater number of heterocontacts between the different arms. Heteroarm stars have observed viscosities and hydrodynamic radii higher than homostars. Internal viscosity increases with increased functionality and molecular weight of branches with the effects of functionality eventually saturating, leaving viscosity dependent only on molecular weight of the arms. Generally, they have smaller hydrodynamic radii, radii of gyration and lower internal viscosities than linear analogues of the same molecular weight. Some of the most interesting characteristics exhibited by star-shaped polymers are their unique rheological and dynamic properties compared to linear analogues of identical molecular weight and monomer composition. The unique properties of star-shaped polymers come from their chemical structure as well as the length and number of their arms. Additionally, individual arms may be composed of multiple polymers, resulting in star-block polymers or star copolymers. These arms can be chemically identical (homostars) or different (heteroarm stars). Star-shaped polymers consist of a multifunctional center from which at least three polymer chains (arms) radiate.
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Stars with more than one arm species are designated as variegated stars (hetero-arm). Stars containing only one species (same chemistry and molar mass) of arms are called regular stars (also called homo-arm). When the number of arms and its distribution is known this can be designated as for example 6- star-(polyA( f3) polyB( f3)) where 6 arms exist in total whereof 3 consist of polyA polymer. An example would be star-(polyA polyB pol圜) for a variegated (heteroarm) star polymer with three arm species, but an undefined number of arms and distribution of arms. According to IUPAC star-shaped polymers are designated by a star prefix which can be further specified as f- star when the number of arms f is known. Recommendations on nomenclatures still differ widely across different regulatory bodies ( IUPAC, CAS, MDL). Many studies on the characteristics, syntheses, and applications of star-shaped polymers have since been undertaken and remain an active area of study. Their research presented the first study demonstrating a method to create well-defined star-shaped polymers this route was through living anionic polymerization. The next major publication regarding star-shaped polymers was in 1962 by Maurice Morton et al. Star-shaped polymers were first reported by John Schaefgen and Paul Flory in 1948 while studying multichain polymers they synthesized star-shaped polyamides.