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In polymer science, star-shaped polymers are the simplest class of branched polymers with a general structure consisting of several (at least three) linear chains connected to a central core. [1] 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.
A star-shaped polymer molecule is a branched polymer molecule in which a single branch point gives rise to multiple linear chains or arms. If the arms are identical the star polymer molecule is said to be regular. If adjacent arms are composed of different repeating subunits, the star polymer molecule is said to be variegated.
Branch point in a polymer. Polymer architecture in polymer science relates to the way branching leads to a deviation from a strictly linear polymer chain. [1] Branching may occur randomly or reactions may be designed so that specific architectures are targeted. [1] It is an important microstructural feature.
All polymers are made of repetitive units called monomers. Biopolymers often have a well-defined structure, though this is not a defining characteristic (example: lignocellulose ): The exact chemical composition and the sequence in which these units are arranged is called the primary structure , in the case of proteins.
Star-shaped, their many processes envelop synapses made by neurons. In humans, a single astrocyte cell can interact with up to 2 million synapses at a time. [ 8 ] Astrocytes are classically identified using histological analysis; many of these cells express the intermediate filament glial fibrillary acidic protein (GFAP).
In 1903, Nikolai K. Koltsov proposed that the shape of cells was determined by a network of tubules that he termed the cytoskeleton. The concept of a protein mosaic that dynamically coordinated cytoplasmic biochemistry was proposed by Rudolph Peters in 1929 [12] while the term (cytosquelette, in French) was first introduced by French embryologist Paul Wintrebert in 1931.
Polymers are composed of long molecular chains which form irregular, entangled coils in the melt. Some polymers retain such a disordered structure upon freezing and readily convert into amorphous solids. In other polymers, the chains rearrange upon freezing and form partly ordered regions with a typical size of the order 1 micrometer. [3]
All functional groups on a branch unit are equally reactive; All reactions occur between A and B; There are no intramolecular reactions; As a result of these assumptions, a conversion slightly higher than that predicted by the Flory–Stockmayer Theory is commonly needed to actually create a polymer gel.