Temperature effects ring-opening polymerization

The conventional route to prepare I generally involves a high temperature melt polymerization of hexachlorocyclotriphosphazene, or trimer (IV). Recent studies have demonstrated the effectiveness of various acids and organometalllcs as catalysts for the polymerization of IV (8). Alternate routes for the preparation of chloro-polymer which do not involve the ring opening polymerization of trimer have been reported in the patent literature (9. 10). These routes involve a condensation polymerization process and may prove to be of technological importance for the preparation of low to moderate molecular weight polyphosphazenes. 

The low temperature ( 140°C) anionic ring opening polymerization is further complicated by the crystallinity in nylon 6. Magill [66] has reported that the temperature for maximum crystallization rate in nylon 6 is about 140-145°C. The nucleation rate is low above 145°C, whereas viscous effects hinder crystal growth below this temperature. As a result, at about 140-145°C, heterogeneous reaction conditions can be encountered (as we have seen in our studies) if there is simultaneous polymerization of caprolactam and crystallization of the nylon 6 formed. 

We report on the reaction of 2,2-dimethyl-1,3-propanediol catalyzed by various solid acids in the gas phase at temperatures > 250 °C. Originally, we tried to synthesize four membered cyclic ethers since several oxetanes are of synthetic interest [7,8], E g. 3-hydroxy-oxetane can undergo ring opening polymerization, leading to a water soluble polymer Since 3-hydroxy-oxetane is not very stable, we choose 2,2-dimethyl-1,3-propanediol as model substrate. In this communication, we describe the effect of catalyst structure (various zeolites. 

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