Pyridines ring-opening polymerization

Py = pyridine, Ar = o,o-i-(C3H7)2C6H3. Ring-opening polymerization. 

Ring-opening polymerization of lactides can also be brought about by strong Lewis bases such as 4-(dimethylamino)pyridine (DMAP), or aN-heterocyclic carbene in the presence of aprimary alcohol initiator (Scheme 25.3). These polymerizations are living, and polymer molecular weight can be controlled by the amount of the primary alcohol introduced. ... 

Stereospecific polymerization of cyanides and isocyanides. Geometrical isomerism around a C=N-double bond (syn and anti forms) is possible in principle. Polymers with C=N-dou-ble bonds in the main chain have been obtained by the polymerization of cyanides and by the ring-opening polymerization of pyridine (88). The polymer obtained from pyridine has monomeric units of the type VI. The configuration of the double bonds in... 

Kficheldorf et al. have reported that pyridines can be directly used as organic nucleophilic initiators for the metal-free - but noncatalyzed - zwitterionic ring-opening polymerization (ZROP) of pivalolactone (Scheme 7). Linear zwitterionic aliphatic polyesters, with a pytidinium and a car-boxylate group, in a- and co-position respectively, are formed in this way. 

Template polymerization for polypeptide synthesis was reported by Ballard and Bamford (63) and described in detail in Reference 2. The substrate for the synthesis was V -carboxy-a-amino acid anhydride (NCA). The first step consists in the reaction of NCA with secondary amine on the end of the polypeptide template. The ring-opening process and the elimination of CO2 then proceeds as a chain reaction. Valuable experimental material concerning the polymerization of many different N-carboxyanhydrides initiated by many different polypeptides (64-66) as well as by poly(vinyl pyridine) (67,68) was collected by Imanishi and co-workers. 

Method 2. Reequilibration of Cyclic Dimethylsiloxanes Recent evidence supports the presence of macrocyclic poly(dimethylsilox-anes) in dimethyl silicone polymers (22,23,31). In what is really a ring-opening followed by a ring-forming polymerization, octamethylcyclotetrasiloxane was heated with traces of potassium hydroxide with or without a diluent and chain-stopped with trimethylchlorosilane/pyridine. 

---