Ring-opening polymerization
A ring-opening polymerization is a chain polymerization in which a cyclic monomer is converted into a mostly linear polymer by breaking a bond and then forming a (mostly) similar bond . An example of a non-linear polymer is the polymerization of aziridine to give polyethyleneimine , which upon direct polymerization yields a highly branched product. Such reactions mostly get the driving force exclusively from the reduction of the ring tension in the monomer molecule, since no new, energetically more favorable bonds are created and the loss of entropy cannot be compensated for by the condensation of a low molecular weight by-product.
application
One example is the conversion of lactams into polyamides, as in the case of the polymerisability of caprolactam (more precisely ε-aminocaprolactam) discovered by Paul Schlack in 1938 through ring opening. The end product polyamide 6 became known worldwide under the trade name Perlon .
Another technically very important process is the production of polyethylene glycols from ethylene oxide . This reaction is a classic living polymerization , in which the resulting molar mass is determined by the ratio of monomer to initiator .
In ring-opening metathesis polymerization (see also alkene metathesis ), the driving force is also to be found in the ring tension of the monomers used.
Individual evidence
- ^ Siegfried Hauptmann : Organic Chemistry , 2nd Edition, VEB Deutscher Verlag für Grundstoffindindustrie, Leipzig, 1985, p. 737, ISBN 3-342-00280-8 .