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Then according to the chain reaction mechanism, the polymer loses the monomer one by one. However, the molecular chain doesn't change a lot in a short time. The reaction is shown below. [5] This process is common for polymethymethacrylate (perspex). CH 2-C(CH 3)COOCH 3-CH 2-C*(CH 3)COOCH 3 →CH 2-C*(CH 3)COOCH 3 + CH 2 =C(CH 3)COOCH 3
The styrene monomer (from which polystyrene is made) is a cancer suspect agent. [109] Styrene is "generally found in such low levels in consumer products that risks aren't substantial". [110] Polystyrene which is used for food contact may not contain more than 1% (0.5% for fatty foods) of styrene by weight. [111]
Usage of monomer in the reaction: Rapid loss of monomer early in the reaction: Some monomer remains even at long reaction times Reaction steps: Similar steps repeated throughout reaction process: Different steps operate at different stages of mechanism (i.e. initiation, propagation, termination, and chain transfer) Average molecular weight
In the absence of chain-transfer and chain termination, the monomer in the system is consumed and the polymerization stops but the polymer chain remains active. If new monomer is added, the polymerization can proceed. Due to the low PDI and predictable molecular weight, living polymerization is at the forefront of polymer research.
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.
Styrene is an organic compound with the chemical formula C 6 H 5 CH=CH 2.Its structure consists of a vinyl group as substituent on benzene.Styrene is a colorless, oily liquid, although aged samples can appear yellowish.
Chain transfer to monomer may take place in which the growing polymer chain abstracts an atom from unreacted monomer existing in the reaction medium. Because, by definition, polymerization reactions only take place in the presence of monomer, chain transfer to monomer determines the theoretical maximum molecular weight that can be achieved by a ...
Several strategies were employed to minimize monomer-monomer reactions (or self-condensation) and polymerizations with low D and controllable Mn have been attained by this mechanism for small molecular weight polymers. [22]