Atmosphere during polymerization

Figure 6. Chromatographs of two samples of poly(dichlorophosphazene) exposed to the atmosphere during polymerization...

Under an argon atmosphere, to a stirred solution of equimolar quantities of dialdehyde 621 and 1,4-phenylenediacetonitrile in THF and tert-h Ay alcohol (1 1) was added dropwise 5mol% of Bu4NOH (1 M in methanol) at 45°C for 20 min. The resulting paste-like polymeric product that precipitated from the solution during polymerization was collected and thoroughly washed with methanol to remove ionic species and unreacted compounds. The scarlet polymeric product was dried in a vacuum oven at 40°C for 2 days. The polymer yield was 93%. GPC (THF, polystyrene standard) Mw= 1.5 x 106 g/mol, Mn = 3.1 x 105 g/mol. 

The polymerization proceeds via a radical chain-reaction mechanism, judging from some features of the polymerization initiation by irradiation or upon heating, no formation of oligomers, and polymer formation irrespective of the medium or atmosphere. The propagating radicals are readily detected by ESR spectroscopy during polymerization in the crystalline state (Fig. 2), because termination between the propagating radicals occurs less frequently in the solid state [50]. 

After purification, the lactam is polymerized by heating at elevated temperatures in an inert atmosphere. During self-condensation, the ring structure of the lactam is opened so that the monomer acts as an epsilon-aminocaproic acid radical. Unlike that of nylon 66, the polymerization of caprolactam is reversible the polymer remains in equilibrium with a small amount of monomer. As with nylon 66, nylon 6 is extruded in thin strands, quenched, and cut into chips for subsequent spinning, or the molten polymer is pumped directly to the spinning equipment. 

To remove the polymeric binder, the green body is heated often in an oxidizing atmosphere. During this process the polymer degrades along many possible degradation pathways, which include (1) scission of the main chain, (2) reaction with side chains and substituents, and... 

Homogenous lactam polymerizations usually proceed with a decrease of volume. At atmospheric pressure the value of the pAV term is negligible and the heat of polymerization can be considered as a measure of the difference in internal energy between the linear and cyclic monomer unit. At very high pressures, however, the effect of volume contraction during polymerization on the monomer-polymer equilibrium cannot be neg-... 

The enthalpy change of polymerization of alphamethyl-styrene is -8.4 kcal/mole and change in volume during polymerization is -14.7 mL/mole at 20°C. If the ceiling temperature for polyalphamethyl-styrene at atmospheric pressure is 61 °C, what is the ceiling temperature of polyalphamethyl-styrene at 500 atm pressure ... 

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