Monomer reversion

THE NETWORK POLYMER-BIFUNCTIONAL MONOMER REVERSIBLE SYSTEM Endo T Suzuki T Sanda F Takata T Tokyo,Institute of Technology... 

Moreover, taking into account that reversed micelles coexist with surfactant monomers, in principle, further effects due to the aggregation of polar and amphiphilic so-lubihzates with surfactant monomers and the shift of the monomer/reversed micelle equilibrium must be also considered [25,26],... 

Endo T, Suzuki T, Sanda F, Takata T (1996) A novel approach for the chemical recycling of polymeric materials the network polymer bifunctional monomer reversible system. Macromolecules 29 3315-3316... 

Zero order kinetics in monomer was reported [95,97] for the polymerization of vinyl ethers initiated by HI/I2 in hexane and was ascribed to the formation of a complex between iodine (Lewis acid) and monomer. It has been proposed that monomer reversibly forms a complex with the growing chain (.. . -CH2CH(OR)I,l2) which then slowly inserts monomer in the rate-determining step [74]. Another possibility is that the ionization of the dormant species the rate-determining step where the cation subsequently undergoes the rapid reaction with monomer and then soon col-... 

The 19F NMR spectrum shown in Figure 7-26 is actually very close to this, with 5-6% of the monomers reversed. 

The question of which degradation mechanism a particular polymer will be subjected to — random scission, side group scission, monomer reversion, or a combination of these — is simplified by considering the nature of thermal degradation as a free radical process. All of the degradation products shown, as well as minor constituents, and deviations to the simplified rules are consistent with the following general statements ... 

Many acrylic copolymers are currently used in the textile industry as binders for nonwoven fabrics. The purpose of these fibers is to stabilize the material. In many instances, these copolymers are used in conjunction with amino resins. Casanovas and Rovira have done a study of methyl methacrylate-ethyl acrylate-N-methylol-acrylamide by PY/GC-MS. Among the products identified were methane, ethylene, propene, isobutene, methanol, propionaldehyde, ethanol, ethyl acetate, methyl acrylate, methyl isobutyrate, ethyl acrylate, methyl methacrylate, n-propyl acrylate, and ethyl methacrylate. In this sample, clearly monomer reversion is the primary degradation process occurring however, several other degradation mechanisms are at work. When the sample contains an amino resin in the mixture, acrylonitrile is observed in the pyrogram. Another effect of the amino presence was a marked increase in the amount of methanol detected. Other products detected were meth-oxyhydrazine, methyl isocyanate, and methyl isocyanide. 

Scheme 31.13 Synthesis of crosslinked polynorbornene-supported NHC-metal complexes through C02-masked NHC monomers reversible reaction of NHCs with CO2 (inset).

Similar colour changes occur, if partially polymerized samples are heated (Fig. 7c) or treated with a solvent able to dissolve the monomer and unable to dissolve the polymer (Fig. 7 d) Colour changes upon heating of the samples are reversible, unless the annealing temperature exceeds the melting point of the residual monomer. Reversible thermochromism is especially observed for high melting salts as for example the lithium salt 6b... 

The combination of triisobutylborane [1116-39-8] and oxygen has been used to polymerize VF at reduced temperature and pressure (81). Polymerization temperature was varied from 0 to 85° C, with a corresponding drop in melting point from about 230°C (polymerization at 0°C) to about 200°C (pol5unerization at 85°C). This dependence of melting temperature, and degree of crystallinity, has been interpreted in terms of variations in the extent of monomer reversals during polymerization (82). 

Bruch and co-workers [56] studied a commercial sample and also a laboratory-prepared sample containing no monomer reversals. Broadband proton-decoupled... 

Bruch and co-workers [79] stndied a commercial sample and also a laboratory-prepared sample containing no monomer reversals. Broadband proton-decoupled fluorine-NMR spectra of solntions in N,N-dimethylformamide at 130 °C were obtained at 188.2 MHz. A two-dimensional /-correlated NMR experiment enabled definitive assignments of the individual peaks to different tactic sequences to be made. 

---