Poly reaction path

Figure 4. Phase inversion followed by the reaction path of poly[(CO,SA,TDI)-SIN-(S,DVB)].

Consequently, two possible reaction paths, i.e., an intramolecular hh addition of uncyclized head radical and an intermolecular hh addition of cyclized head radical should be considered for the incorporating process of hh linkage into the derived poly-AAc chain. The discrimination of these two reactions is not easy, but the possibility of the occurrence of an intermolecular hh addition of cyclized head radical may be omitted by considering the steric crowding in the resulting cyclized polymer. Thus, the following three types of typical cyclopolymers will be given schematically. ... 

When this poly (ortho ester) is placed in an aqueous environment, an initial hydrolysis to a diol and y-butyrolactone takes place. The y-butyrolactone then rapidly hydrolyzes to y-hydroxybutyric acid. This reaction path is shown in Scheme 4. 

The initial steps in oxidative reaction of aromatic, poly-aromatic and other cyclic and linear unsaturated hydrocarbons in the atmosphere or in combustion involve radical formation. These radicals react with molecular oxygen. The subsequent reactions of these peroxy radicals, as shown e.g. in Figure 4.1, result in unsaturated linear or cyclic, oxygenated or multi-oxygenated hydrocarbon intermediates. The thermochemistry for these unsaturated - oxygenated species is needed to evaluate their stability and likely reaction paths in the environment, in combustion and in other thermal and oxidative processes. 

The results obtained in a study of the reactions of one of the same cryptands, Eu(2.2.1) , with the excited states of a series of poly(pyridine)Ru(II) complexes show a qualitative agreement with the previous study. The detailed analysis of the data by Sabbatini et al. (1986), however, invokes the availability of nonadiabatic reaction paths for the cross reactions. The fact that in this later study, the thermody-... 

Anionic polymerization of unsubstituted acrylamide, catalyzed by strong bases, does not yield typical vinyl polymers. Instead, the product is a 1,3-adduct, poly -alanine). " Two alternate reaction paths were originally proposed " ... 

The thermal degradation of poly(butylene terephthalate) was examined with the aid of a laser microprobe and mass spectrometry [506]. A complex multistage decomposition mechanism was observed that involves two reaction paths. The initial degradation takes place by an ionic mechanism. This results in an evolution of tetrahydrofuran. This is followed by concerted ester pyrolyses reactions that involve intermediate cyclic transition states and result in formation of 1,3-butadiene. Simultaneous decarboxylations occur in both decomposition paths. The latter stages of decomposition are... 

Radiation has been employed for the synthesis of various microgel dispersions. P Ulanski etal. [11] exposed an aqueous solution of linear poly acrylic acid (PAA) to pulse irradiation produced by fast electrons. The irradiation energy facilitated the formation of PAA radicals and these radicals imderwent a major reaction path of intramolecular recombination. This reaction led to an interlinking process within the polymer molecules and the final formation of nano-gel particles. 

It should additionally be noted that a number of the paths of the schemes above have received some confirmation in a number of literature reports dealing with the photolysis and photo-oxidation of other polyesters [32-35], Because these reports investigated poly(butylene terephthalate) (PBT), poly(ethylene naphthalate) and poly(butylene naphthalate), however, they may not have direct application to understanding of the processes involved in PET and PECT and so have not been discussed in this present chapter. All do contain support for the formation of radicals leading to CO and C02 evolution, as well as the hydrogen abstraction at glycolic carbons to form hydroperoxides which then decompose to form alkoxy radicals and the hydroxyl radical. These species then were postulated to undergo further reaction consistent with what we have proposed above. 

In a poly crystalline mixture of solid reactants, we might expect the particle size to be of the order of 10 pm even careful and persistent grinding will only reduce the particle size to around 0.1 pm. Diffusion during a ceramic reaction is therefore taking place across anywhere between 100 and 10,000 unit cells. Various ingenious methods, some physical and some chemical, have been pioneered to bring the components of the reaction either into more intimate contact, or into contact at an atomic level, and so reduce this diffusion path in doing so, the reactions can often take place at lower temperatures. 

Path B in Fig. 2 is the convergent method. It is the outside-inward method, proposed independently by Miller and Neenan [9] and by Hawker and Frechet [10]. This method is well suited when the branch point is an aromatic ring. As an example of the convergent process we show in Scheme 3 the preparation of poly(benzyl ether) dendrimers. The phenol functionality of 2,5-dihydroxyben-zyl alcohol is first protected by Williamson reaction with benzyl bromide to provide the first generation dendron [G-l]-OH. The benzyl alcohol in [G-l]-OH is then converted to the benzyl bromide form [G-1]-Br. This in turn reacts with... 

Poly(iminoborane)s [(-BR=N-)n] are a potential 7t-conjugated polymers, since boron-nitrogen bonds possess the double bond like nature owing to pTt-pjt interaction However, these materials are not fully characterized so far 10>. In order to incorporate the monomeric B-N bond into the conjugation path, we examined an alternating boration copolymerization between diisocyanates and diynes making use of different reactivity between haloboration and phenylboration reactions. 

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