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A repeat unit or repeating unit (or mer) is a part of a polymer whose repetition would produce the complete polymer chain (except for the end-groups) by linking the repeat units together successively along the chain, like the beads of a necklace.
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The smallest repeating portion is a CRU, so all such possibilities are identified (including multiple directional possibilities for the chain). For the preceding polymer, they are: The subunits that make up each of these structures are identified, i.e., the largest divalent groups that can be named using IUPAC nomenclature of organic chemistry .
A repeating decimal or recurring decimal is a decimal representation of a number whose digits are eventually periodic (that is, after some place, the same sequence of digits is repeated forever); if this sequence consists only of zeros (that is if there is only a finite number of nonzero digits), the decimal is said to be terminating, and is not considered as repeating.
The mass-average molecular mass, M w, is also related to the fractional monomer conversion, p, in step-growth polymerization (for the simplest case of linear polymers formed from two monomers in equimolar quantities) as per Carothers' equation: ¯ = + ¯ = (+), where M o is the molecular mass of the repeating unit.
The union of the homopolymer subunits may require an intermediate non-repeating subunit, known as a junction block. Diblock copolymers have two distinct blocks; triblock copolymers have three. Technically, a block is a portion of a macromolecule, comprising many units, that has at least one feature which is not present in the adjacent portions. [1]
If a diad consists of units oriented in opposition, the diad is called an r diad (formerly racemo diad, as in a racemic compound, now proscribed [3]). In the case of vinyl polymer molecules, an m diad is one in which the substituents are oriented on the same side of the polymer backbone; in the Natta projection, they both point into the plane ...
When a monomer adds to a radical chain end, there are two factors to consider regarding its stereochemistry: 1) the interaction between the terminal chain carbon and the approaching monomer molecule and 2) the configuration of the penultimate repeating unit in the polymer chain. [4] The terminal carbon atom has sp 2 hybridization and is planar.