Poly thermal reactions

The degradation reactions of polymers have been widely reviewed 525). In the absence of air, thermal reactions are the important degradation route. They may involve reactions of functional groups on the chain without chain scission, typified for example by the dehydrochlorination of PVC, or reactions involving chain scission, often followed by depropagation and chain-transfer reactions to yield complex mixtures of products. This latter route would be typical of the degradation of poly(methyl methacrylate), which depolymerizes smoothly to its monomer, and of polystyrene, which produces a wide range of tarry products. 

The thermal decomposition of 1,1,1,-trifluoroacetone has been studied by Fekete - , and that of fluoroacetone hemiacetal esters by Newallis et Lewis and Newman have reported on the rearrangements of fluoroesters in the gas phase. Thermal reactions of nitrogen-containing fluoro-compounds have included trifluoromethyl cyanide , hexafluoroazomethane , tetrafluorohydra-zine , fluorodiazirines , perfluoropyridazines , fluorochlorodinitrometh-ane and poly(difluoroamino)fluoromethanes - . ... 

Later, the same methodology was applied by Wallow and Novak for the synthesis of water-soluble poly(p-phenylene) derivatives via the poly-Suzuki reaction of 4,4 -biphenylylene bis(boronic acid) with 4,4 -dibromodiphenic acid in aqueous di-methylformamide [26]. These aromatic, rigid-chain polymers exhibit outstanding thermal stability (decomposition above 500 °C) and play an important role in high-performance engineering materials [27] conducting polymers [28] and nonlinear optical materials [29]. 

Depolymerization is the reverse reaction to polymerization it consists of unzipping the monomeric units after initiation of the reaction either at random or at the chain ends. The initiation can be the consequence of a photochemical reaction but depolymerization itself is a purely thermal reaction which is discussed in Chapter 1 of this book. It is usually negligible at room temperature. Photochemically initiated depolymerization has been studied in the case of polymethylmethacrylate [9], poly-a-methylstyrene [10] and polymethylisopropenylketone [11]. 

Earlier suggested syntheses for poly(arylene sulfides) are shown in Scheme 4. Most of these syntheses involve either electrophilic or thermal reactions. 

The aliphatic poly-l,3,4-oxadiazoles are made by a similar process by the thermal reaction of the polyhydrazides. 

As the temperature increases, sequences containing totally aromatic polyester accumulate in the residue, indicating that the overall thermal reaction has resulted in the formation of the most thermally stable compound, i.e., a totally aromatic polyester. As a consequence, the last decomposition stage is solely due to the evolution of the cyclic dimer (ion at m/z 717) formed by tiie thermal degradation of the aromatic polyester sequences (Scheme 5.11c), as confirmed by the DPMS analysis of pure poly(bisphenol A terephthalate). ... 

Reaction (1) shows the calcination of kaolin, which can also be described as a thermal dehydration process that destroys the original layered structure of the system. Reactions (2) and (4) describe the alkahne dissolution of metakaolin resulting in primary condensation structures (aluminosilicate oligomers), which, by further poly condensation reactions (3) and (5) in the alkaline environment, give rise to an infinite number of repeating units, thus resulting in a geopolymeric network [10]. The formation of the aluminosilicate structure was initially simply described as a series of destructive and condensation reactions ... 

The thermal reaction of cis or trans 1,4-poly(butadiene) with iron carbonyls results in geometrical isomerization of the alkenyl moieties and formation of polymers containing conjugated diene) iron tricarbonyl units. In the course of our continuing studies of the formation of stable colloidal iron dispersions by thermal decomposition of metal carbonyls in the presence of functional polymers, some aspects of this work have been repeated. Our objective was to isolate the soluble organometallic polymer which was intermediate to particle nucleation and independently examine the intramolecular condensation of metal atoms to yield metal clusters and metal particles. In this paper, the structure of the intermediate obtained on thermolysis of an excess of FeCCO) in a dilute xylene solution of c/5-poly(butadiene) has been described. 

We studied the postpolymerization thermal reaction of polybutadiyne by DSC, TGA, IR, ESR and electrical conduc vity measurements. The results are summarized as follows. Polybutadiyne was vapor deposited onto thin films of polyethylene (PE), poly(vinylidene fluoride) (PVF2), poly(tetrafluoroethylene) (FIFE) and poly(tetrafluoroethylene co-hexafluoropropylene)... 

The experimental observations of poly condensation reactions involving aqueous acetic acid open an important area for future research. Thermally induced reactions of this type may involve similar catalytic pathways to the oxidation process in (6). 

Under 254 nm radiation additional methane and ethylene are formed compared with the thermal reaction Poly(methyl methacrylate) stabilized by blending with polypropylene pre-irradiation with 2537 A radiation at ambient temperature reduces amount of methyl methacrylale formed on subsequent thermal degradation missing methyl methacrylate units appear in a chain fragment fiaction... 

The most innovative photohalogenation technology developed in the latter twentieth century is that for purposes of photochlorination of poly(vinyl chloride) (PVC). More highly chlorinated products of improved thermal stabiUty, fire resistance, and rigidity are obtained. In production, the stepwise chlorination may be effected in Hquid chlorine which serves both as solvent for the polymer and reagent (46). A soHd-state process has also been devised in which a bed of microparticulate PVC is fluidized with CI2 gas and simultaneously irradiated (47). In both cases the reaction proceeds, counterintuitively, to introduce Cl exclusively at unchlorinated carbon atoms on the polymer backbone. 

Polymerization by Transimidization Reaction. Exchange polymerization via equihbrium reactions is commonly practiced for the preparation of polyesters and polycarbonates. The two-step transimidization polymerization of polyimides was described in an early patent (65). The reaction of pyromellitic diimide with diamines in dipolar solvents resulted in poly(amic amide)s that were thermally converted to the polyimides. High molecular weight polyimides were obtained by employing a more reactive bisimide system (66). The intermediate poly(amic ethylcarboamide) was converted to the polyimide at 240°C. 

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