Effect of Coinitiator

Effect of Coinitiator Type on the Composition of Poly(4-methyl-l-pentene) 85... 

The effect of coinitiator type on the composition of poly(4-methyl-1-pentene) has been studied using EtAlCl2, A1G3, BF3, and PF5, in the range from —30° C to —120° C. Tables 6-9 and Fig. 22 show the results. The activation energy... 

Fig. 22, The effect of coinitiator type on the composition of poly(4-methyH-pentene)...

Importantly, the effect of coinitiator type, i.e., EtAlCl2 versus BF3, appears to be pronounced in nonpolar solvent Recall that for these two coinitiators at... 

Results of these orienting experiments compiled in Table 3 in regard to the effect of temperature, medium polarity, initiator concentration, monomer concentration, and coinitiator concentration are similar to those reported by others36"39 for cationic polymerization of a-methylstyrene. For example, decreasing temperature, the molecular weight increases and increasing medium polarity, the yield increases. 

Effects of solvent polarity, counter-anion nucleophilidty, temperature, and monomer concentration on the carbenium ion polymerization chemistry have been extensively studied29,36 38,49. Based on previous knowledge26"29 Me3Al was chosen because with this coinitiator undesired chain transfer to monomer processes are absent. Preliminary experiments showed that Et3Al coinitiator did not yield PaMeSt, possibly because the nuc-leophilicity of the counter-anion Et3AlQe is too high and thus termination by hydrida-tion is faster than propagation36. ... 

This section concerns the synthesis of polyisobutylenes (PIB) bearing a Si-H head-group (HSi-PIB) by the use of Si-H containing functional initiator in conjunction with Me3Al coinitiator. First the effect of reaction conditions on the rate and molecular weight have been investigated and subsequently a H1 NMR method for the quantitative characterization of Si-H groups in HSi-PIB was developed. 

VIII. Effect of the Nature of Halogen in t-BuX Initiators, Et2AlX Coinitiators... 

It was postulated that the rate decreased as the basicity of the halogen decreased and/or steric compression increased in f-BuX, and as the polarizability of halogen in MeX increased. The objective of the present research was to extend this model study to isobutylene polymerization systems, in particular to investigate the effect of reagent addition sequence and that of the nature of the halogen in f-BuX and MeX on the polymerization rate and PIB yield using Me3 Al coinitiator. 

Et2 All coinitiators and MeCl, MeBr and Mel solvents at various temperatures. The H20 /EtAiei2/n-pentane system was also briefly investigated. A large number of comparative molecular weight and conversion data were gathered. The effect of MeX on the polymerization was investigated in detail. In this section, conversion and initiator efficiency data will be discussed. 

Effect of f-BuX, MeX and Temperature on Isobutylene Polymerization Using Et2AlCl Coinitiator... 

In previous papers1,2 we described reactivity studies of cationic isobutylene polymerization using r-butyl halide initiators, alkylaluminum coinitiators and methyl halide solvents. The effects of these reagents as well as temperature on the overall rate of polymerization and polyisobutylene (PIB) yield were studied and reactivity orders were established. These results were explained by a modified initiation mechanism based on an earlier model proposed by Kennedy and co-workers3,4. This paper concerns the effects of f-butyl halide, alkylaluminums and methyl halide, as well as temperature and isobutylene concentration on PIB molecular weights. 

Effect of r-BuX Initiator, Et2AlX Coinitiator, MeX Solvent and Temperature on Mv and AEmv of PIB... 

Fig. 10. Effect of temperature on My of PIB prepared with Et2AlCi coinitiator...

To study the effect of temperature, coinitiator type, solvent polarity and monomer concentration on the composition of poly(4-methyl- 1-pentene) by high resolution lH NMR spectroscopy. 

The second objective of our work was to investigate the relation between synthesis conditions and the composition of poly(4-methyl-l -pentene). Having developed a satisfactory method for determining the composition of the polymer, a study was undertaken of the effect of monomer concentration, coinitiator concentration, conversion, temperature, coinitiator type, and solvent polarity on the composition of the polymer. 

Table 4 shows the effect of monomer concentration, coinitiator concentration, and conversion on the composition of poly(4-methyl-1-pentene) using EtAlCl2 coinitiator at — 50° C. The 1,2-, 1,3-, and 1,4-repeat unit concentrations in the polymer have been determined from polymer spectra by use of a computer curve simulator-plotting program and are rounded to the nearest percent. No limits of error are indicated since none could be determined analytically. A reasonable error is thought to be +15% of the measured value. 

The effect of monomer concentration on the rate of polymerization of 4-methyl-1-pentene was investigated using ethylaluminum dichloride coinitiator in ethyl chloride solvent at — 30°, — 50°, — 70°, and — 80° C. Results are compiled in Table 5 and shown in Fig. 18. 

Since isomerization and propagation are both ionic processes, solvent polarity was expected to affect their rates and in turn polymer composition. The effect of solvent polarity on I using a polar solvent, ethyl chloride, and a nonpolar solvent, n-pentane, and EtAlCl2 and BF3 coinitiators at various temperatures is shown in Table 10. 

The effect of the structure of the coinitiator is studied using 3% PDO and 5% electron donor. The measured photospeed increases in the order N-isopropylamine < dibenzylamine < triethylamine N,N dimethylbenzyl-amide < iV-benzylethanolamine < MDEA. However, a reactivity order for the electron donors can not be inferred from these data because the molar concentration is not the same for the different coinitiators. As shown for MDEA in Table 2, the variation of the photospeed with the amine concentration is not simple. The photospeed increases with increasing amine concentration up to 5%, higher concentrations resulting in lower polymerization rates. 

Common to these photopolymer products was the use of coinitiators, such as 2-MBO, diacrylate and triacrylate monomers, binders, and other additives as required. In general, the film products were coated on a polyester support and a polyolefin sheet laminated to the coated material, to permit exposure of the films in an oxygen-free environment, as was required to obviate the chain-stopping effect of peroxide formation. 

Thus, the ratio Cfi/Cia reflects the relative rate of proton elimination (transfer)/methylation(termination) in the first generation. By changing the coinitiator McaAl, McjAlCl, the effect of counter anions McsAlCl , Me2AlCl2 on this ratio can be studied. 

Results of a large number of experiments carried out to study the effect of temperature and the nature of the coinitiator in various solvents on conversion and product distributions are summarized in Table 3. The effect of temperature on overall conversions obtained in methyl chloride solvent is plotted separately in Fig. 2. These results will be (bussed in terms of the overall coinitiator reactivities and coinitiator efficiencies. Further, the effect of temperature, solvent and the nature of the alkyl-aluminum coinitiator-alkylhalide initiator system on the fundamental reactions of polymerization will be examined... 

The effectiveness of Lewis acids McjAlCl, Et2AlCl, and EtsAl in polymerization of isobutylene follow the trend predicted in model studies, i.e., Me2AlCl > Et2 AlCl > EtjAl, which supports the conclusions of model experiments. Further, the sequence of coinitiator efficiencies in terms of molecular weights, i.e., Me2AlCl > Et2AlCl > EtjAl is similar to that found in model experiments. The conclusions as to the influence of chlorinated and brominated counteranions (e.g., EtjAlClf and Et2AlClBr ) found in polymerization follow the expected behavior from the results of model investigations. 

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