Polypropylene oxide , perfluorinated

Subsequently, we were able to make perfluorinated analogues ofKrytox from the hydrocarbon polypropylene oxide)40 (Figure 14.4). In 1985, we published three interesting perfluoropolyethers. First we copolymerized hexafluoroacetone with ethylene oxide, propylene oxide, and trimethylene oxide. Subsequent fluorination yielded the new perfluoropolyethers (Figure 14.5). 

A similar strategy was reported by Asahi Glass which prepared fluoroacrylic (FA) diblock copolymem used as surface active agents [117]. Acrylates containing perfluorinated groups were telomerized with mercapto acetic acid followed by the condensation of the telomer produced with polypropylene oxide (PPO) to yield PPO-t-PFA diblock copolymers. 

The rapid reaction between atomic oxygen and polymer films is discussed. This typical interface reaction is considerably influenced by the structure of the polymer. All polymers immediately react with atomic oxygen there is no evidence of even short induction periods or autocatalysis. Most readily attacked are highly branched polymers such as polypropylene and polymers with ether links for example, polyformaldehyde. Perfluorinated polymers, rubbers vulcanized with sulphur, and highly aromatic polymers are most resistant (Fig. 22). Oxidation of polymers by atomic oxygen occurs only at or near the surface of the polymer. For this reason the elucidation of the reaction kinetics and mechanism is very difficult. The conventional physico-chemical methods, UV and IR spectroscopy, are in this case inadequate. 

Polypropylene imine dendrimers with covalently attached perfluorinated poly-(propylene oxide) end-groups have been employed for the stabilization of palladium colloids in Heck reactions in fluorous solvents by Crooks et al. [36] (Table 2). Relatively low activities were obtained, which were further reduced upon re-use of the fluorous phase in a second cycle. From the results of repeated Heck reactions without an added base, it can be asstuned that the reduction in activity upon recycling is due to protonation of the dendrimer scaffold, serving as a base. No leaching of palladium from the fluorous phase was detected (< 0.01 ppm) however, this value was not related to the overall palladium loading (cf. also Section 4.2). 

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