Polymer high temperature, reactive oligomer

The thermal polymerization of reactive polyimide oligomers is a critical part of a number of currently important polymers. Both the system in which we are interested, PMR-15, and others like it (LARC-13, HR-600), are useful high temperature resins. They also share the feature that, while the basic structure and chemistry of their imide portions is well defined, the mode of reaction and ultimately the structures that result from their thermally activated end-groups is not clear. Since an understanding of this thermal cure would be an important step towards the improvement of both the cure process and the properties of such systems, we have approached our study of PMR-15 with a focus only on this higher temperature thermal curing process. To this end, we have used small molecule model compounds with pre-formed imide moieties and have concentrated on the chemistry of the norbornenyl end-cap (1). 

The method of acceptor-catalyst polyetherification can be used to produce [184, 185] thermo-reactive polyarylenesulfones on the basis of nonsaturated 4,4 -dioxy-3,3 -diallylbisphenyl-2,2 -propane and various chlor- and sulfo- containing monomers and oligomers. The set of physic-mechanical properties of polymers obtained allows one to propose them as constructional polymers, sealing coatings, film materials capable of operating under the influence of aggressive environments and high temperatures. 

It was later noticed that the hexachlorocyclotriphosphazene can be polymerized by heating in the melt to yield an uncrosslinked linear high polymer, poly[(dichloro)-phosphazene] (Allcock et al, 1965-1966 Rose, 1968). Further heating results in the formation of an insoluble crosslinked material. This leads in both cases to a transparent, rubbery elastomer which hydrolyzes slowly, when exposed to moisture, forming phosphate, ammonia and hydrochloric acid. At temperatures above 350°C, the polymer depolymerizes to cyclic oligomers. The uncrosslinked species serve as highly reactive polymeric precursor. 

With MAO activation, Zr- and Hf-FI catalysts 1 and 3 exhibit fairly high reactivity toward propylene and produce propylene oligomers [64, 65], Conversely, the corresponding Ti-FI catalyst/MAO 2 forms semicrystalline PP (1 °C polymerization), which displays a peak melting temperature of 97 °C, indicative of the formation of a stereoregular polymer. To our surprise, microstructural analysis by 13C NMR indicates that the resultant polymer is syndiotactic (rr 19%), and that a chain-end control mechanism is responsible for the observed stereocontrol, regardless of the C2 symmetric catalyst ([28] for the first report on syndiospecific propylene... 

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