Chain propagation linear

A molecule of linear alkyl ether possesses a very convenient geometry for intramolecular hydrogen atom abstraction by the peroxyl radical. Therefore, chain propagation is performed by two ways in oxidized ethers intermolecular and intramolecular. As a result, two peroxides as primary intermediates are formed from ether due to oxidation, namely, hydroperoxide and dihydroperoxide [62],... 

Linear chain termination is not, however, a necessary condition for the critical behavior. Indeed, with mechanisms V and XII, chain termination is quadratic (v v,172), but critical transition does take place because hydroperoxide decomposes into radicals that contribute to chain propagation. As a result, v (v [ROOH])1/2 v, [ROOH]172, and v [ROOH] (see Equation (14.11)) which explains the critical behavior. 

The species IA, IB, IC represent the chain-propagating ester molecules, stabilised by styrene, and they are equivalent from the point of view of the polymerisation. At the end of the polymerisation, the now unstabilised ester II reacts with its own kind to give the indanyl ion III and a saturated linear polymer IV. It is also in equilibrium with unsaturated polymer V, and it reacts with acid and/or V to give the polymer with indanyl end groups VI. This is equivalent to the transfer reaction with monomer which gives the indanyl end groups [23]. The oligostyryl ion VII can only be present in very small concentration, as it is much less stable than the other SD ions which co-exist with ion III [7] these other SD ions have been omitted from the scheme so as not to complicate it unnecessarily. 

From polymerization tests under the high pressure of 150 MPa, and varying concentrations of ethylene, Rau, Schmitz, and Luft [6] found that chain-propagation is the rate-limiting step and depends linearly on the concentration of ethylene (a = 1). This is different from polymerization at low pressure where an order of 1.2 - 2 was observed [7]. In agreement with results from low-pressure polymerization of ethylene, the overall rate at high pressure also depends linearly on the concentration of metallocene catalyst (b = 1). 

Mono- and dianions can, of course, be used for the initiation of linear chain propagation. Gordon and Loftus observed interesting differences in styrene polymerization when initiated with BuLi and with delocalized carbanions. In the latter case, the anions have various counter-ions (Li+ and K + ) at each of these, propagation proceeds at a different rate. When the initiator contains a greater number of delocalized carbanions, insolubility of the product and non-uniformity of charge on the anions cause some problems [199],... 

The catalytic chain-transfer (CCT) process displays all of the features characteristic of typical, uncatalyzed chain transfer other than taking place at a rate competitive with chain propagation. Thus, the rate of polymerization at low conversions is independent of the concentration of the cobalt porphyrin (Figure 1) while the molecular weight, Mn, decreases linearly by over 2 orders of magnitude with increasing concentration of cobalt catalyst (Figure 2). As expected for a typical polymerization, the rate of polymerization increases linearly with the square root of the concentration of the azo initiator and no polymerization occurs in the absence of the initiator. 

In general, a polymerization process model consists of material balances (component rate equations), energy balances, and additional set of equations to calculate polymer properties (e.g., molecular weight moment equations). The kinetic equations for a typical linear addition polymerization process include initiation or catalytic site activation, chain propagation, chain termination, and chain transfer reactions. The typical reactions that occur in a homogeneous free radical polymerization of vinyl monomers and coordination polymerization of olefins are illustrated in Table 2. 

The radical polymerization of acrylic anhydride(AA) as a typical 1,6-diene has been investigated in detail in terms of cyclopolymerization. Thus, in 1958 Crawshaw and Butler(31) and Jones(32) have independently demonstrated that AA could be polymerized in solution by an alternating intramolecular-intermolecular chain propagation or cyclopolymerization, leading to the formation of saturated, linear polymers consisting exclusively of six-membered ring anhydride structure. Later, Mercier and Smets(33)... 

Actually, we found that w° (wbm, iron(II) complexes,) [Cat]12, and wf [Cat], and linear radicals termination on catalyst may be not taken into account [22], With allowance for quasi-steady-state conditions for R02 radicals the calculated by formula (1) wterm= vr, can be considered a measure of activation of molecular oxygen with iron(II) complexes. Discrepancy between wAP+MPc and wterm in the case of absence of linear termination of chain is connected with additional formation of alcohol and ketone at the stage of chain propagation Cat + R02 (2) ... 

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