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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.
Crystal structure of a first-generation polyphenylene dendrimer reported by Müllen et al [5] A first-generation "cyanostar" dendrimer and its STM image [6]. The first dendrimers were made by divergent synthesis approaches by Fritz Vögtle in 1978, [7] R.G. Denkewalter at Allied Corporation in 1981, [8] [9] Donald Tomalia at Dow Chemical in 1983 [10] and in 1985, [11] [12] and by George R ...
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).
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]
Microfilament functions include cytokinesis, amoeboid movement, cell motility, changes in cell shape, endocytosis and exocytosis, cell contractility, and mechanical stability. Microfilaments are flexible and relatively strong, resisting buckling by multi-piconewton compressive forces and filament fracture by nanonewton tensile forces.