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Polyisoprene is strictly speaking a collective name for polymers that are produced by polymerization of isoprene. In practice polyisoprene is commonly used to refer to synthetic cis -1,4-polyisoprene, made by the industrial polymerisation of isoprene.
Suspension polymerization is divided into two main types, depending on the morphology of the particles that result. In bead polymerization, the polymer is soluble in its monomer and the result is a smooth, translucent bead.
An example of chain transfer in styrene polymerization. Here X = Cl and Y = CCl 3. In some chain-growth polymerizations there is also a chain transfer step, in which the growing polymer chain RM n ° takes an atom X from an inactive molecule XY, terminating the growth of the polymer chain: RM n ° + XY → RM n X + Y°.
This work provided the foundations for the synthesis of polymers with improved control over molecular weight, molecular weight distribution, and the architecture. [7] The use of alkali metals to initiate polymerization of 1,3-dienes led to the discovery by Stavely and co-workers at Firestone Tire and Rubber company of cis-1,4-polyisoprene. [8]
During vulcanization, rubber's polyisoprene molecules (long chains of isoprene) are heated and cross-linked with molecular bonds to sulfur, forming a 3-D matrix. The optimal percentage of sulfur is approximately 10%. In this form, the polyisoprene molecules orientation is still random but they become aligned when the rubber is stretched.
A successful approach relies on native chemical ligation, which achieves the synthesis of proteins by linking shorter unprotected peptides. This strategy allowed to obtain, amongst many others, proteins such as insulin-like growth factor 1 , [ 13 ] the precursor of Aequorea green fluorescent protein [ 14 ] and the influenza A virus M2 membrane ...
About 95% of isoprene production is used to produce cis-1,4-polyisoprene—a synthetic version of natural rubber. [ 14 ] Natural rubber consists mainly of poly-cis-isoprene with a molecular mass of 100,000 to 1,000,000 g/mol. Typically natural rubber contains a few percent of other materials, such as proteins, fatty acids, resins, and inorganic ...
The total number of radicals delivered to the system by the initiator during the course of the polymerization is low compared to the number of RAFT agent molecules, meaning that the R group initiated polymer chains from the re-initiation step form the majority of the chains in the system, rather than initiator fragment bearing chains formed in ...