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A graft polymer molecule is a branched polymer molecule in which one or more of the side chains are different, structurally or configurationally, from the main chain. A star-shaped polymer molecule is a branched polymer molecule in which a single branch point gives rise to multiple linear chains or arms.
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.
Branched polymers are formed as monomer adds to the new radical site which is located along the polymer backbone. The properties of low-density polyethylene are critically determined by the amount of chain transfer to polymer that takes place. Chain transfer from polypropylene to backbone of another polypropylene. Transfer to solvent.
At this second resting state, the ethylene molecule can insert to grow the polymer or dissociate inducing further chain walking. If many branches can form, a hyperbranched topology results. Therefore, ethene only homopolymerization can provide branched polymer whereas the same mechanism leads to chain straightening in α-olefin polymerization. [8]
The easiest way to visualize the mechanism of a step-growth polymerization is a group of people reaching out to hold their hands to form a human chain—each person has two hands (= reactive sites). There also is the possibility to have more than two reactive sites on a monomer: In this case branched polymers production take place.
Graft copolymers are a branched copolymer where the components of the side chain are structurally different than that of the main chain. Graft copolymers containing a larger quantity of side chains are capable of wormlike conformation, compact molecular dimension, and notable chain end effects due to their confined and tight fit structures. [1]
As the linking continues, larger branched polymers are obtained and at a certain extent of the reaction, links between the polymer result in the formation of a single macroscopic molecule. At that point in the reaction, which is defined as gel point , the system loses fluidity and viscosity becomes very large.
This type of polymerization is described as "chain" or "chain-growth" because the reaction mechanism is a chemical chain reaction with an initiation step in which an active center is formed, followed by a rapid sequence of chain propagation steps in which the polymer molecule grows by addition of one monomer molecule to the active center in ...