Ring-opening addition condensation

The other entries in Table 13.2 show that heat removal is not a problem for most ring-opening and condensation polymerizations. Polycaprolactam (also called Nylon 6) is an addition polymer, but with rather similar bond energies for the monomer and the polymer. The reaction exotherm is small enough that large parts are made by essentially adiabatic reaction in a mold. An equilibrium between monomer and polymer does exist for polycaprolactam, but it occurs at commercially acceptable molecular weights. 

Nucleophiles usually react with 47/-benzopyran-4-ones at C-2, which results in pyran ring opening. The condensation of dilithiooximes onto 4/7-chroman-4-ones occurs by a 1,2-addition process to afford 47/-chromene 4-spiro-5 -isoxazolines 130 in good yield (Equation 61) <2004TL7351>. 

Method of synthesis ring-opening addition polymerization of 8-caprolactone at 170°C under nitrogen with dibutyl stanneous oxide as the catalyst also condensation of 6-hydroxycaproic acid gives PCL polymerization is frequently conducted in extruder Kim, B J White, J L, Antec, 224-8, 2000 Label, M Thielemans, Chem. Soc. Rev., 38,3484-3504, 2009. 

There are several aspects of these polymerizations that are not well understood. In addition, the literature reports do not include details on the yields of the polymers and on the purification methods that were used. In this paper, we report the results of our studies on both the ring opening and condensation polymerizations. Our studies of the ring opening polymerizations focus on the effects of the alkylene groups on the polymerizations of the cyclic phosphonates and on the best methods for converting the poly(alkylene phosphonate)s to poly(alkylene phosphate) s. Our studies on the condensation polymerizations are more preliminary in nature and focus on the mechanism by which the polymerizations occur. 

In the next group of chapters we shall discuss condensation or step-growth polymers and polymerizations in Chap. 5, addition or chain-growth polymers and polymerizations in Chap. 6, and copolymers and stereoregular polymers in Chap. 7. It should not be inferred from this that these are the only classes of polymers and polymerization reactions. Topics such as ring-opening polymeri-... 

Base-induced eliminative ring fission, in which both the double bond and the sulfone function take part, has been observed in thiete dioxides253. The reaction can be rationalized in terms of initial Michael-type addition to the double bond of the ring vinyl sulfone, followed by a reverse aldol condensation with ring opening. The isolation of the ether 270c in the treatment of 6c with potassium ethoxide (since the transformation 267 -> 268 is not possible in this case) is in agreement with the reaction mechanism outlined in equation 101253. 

Polymers are formed via two general mechanisms, namely chain or step polymerisation, originally called addition and condensation, respectively, although some polymerisations can yield polymers by both routes (see Chapter 2). For example, ring opening of cyclic compounds (e.g., cyclic lactides and lactams, cyclic siloxanes) yield polymers either with added catalyst (chain) or by hydrolysis followed by condensation (step). Many polymers are made via vinyl polymerisation, e.g., PE, PP, PVC, poly(methyl methacrylate) (PMMA). It could be argued that the ethylenic double bond is a strained cyclic system. 

---