Effect of initiator type

Several researchers have carried out experimental and/or theoretical investigations on emulsion polymerizations initiated with oil-soluble initiators and reported that the kinetics of the emulsion polymerizations is basically similar to that initiated with water-soluble initiators [193-202]. Breitenbach et al. [193] carried out the emulsion polymerization of St initiated by BPO at 50 and 60 °C. The authors interpreted the experimental results by assuming a relatively rapid exchange of low molecular weight radicals between the micelle-polymer 

In order to delve deeper into the similarities and differences between the kinetic behaviors of emulsion polymerization initiated by oil-soluble initiators or water-soluble initiators, Nomura et al. [199-202] carried out extensive investigations into the kinetics and mechanisms of the unseeded and seeded emulsion polymerizations of St at 50 °C using sodium lauryl sulfate (NaLS) as the emulsifier and AIBN as the initiator, and obtained the following conclusions  

The latex (polymer) particles are generated from the emulsifier micelles and the number of latex particles produced is proportional to the 0.70 power of the initial concentration of the emulsifier forming micelles and to the 0.30 power of the concentration of initially charged AIBN. This behavior is very similar to that observed when the water-soluble initiator KPS is used. The polymerization takes place both in the monomer droplets and in the latex particles produced. The polymerization inside the monomer droplets proceeds according to the kinetics of suspension polymerization until the 

The free radicals produced from the fraction of initiator dissolved in the water phase are responsible for particle formation and growth in the emulsion polymerization of St initiated by AIBN. The free radicals produced in pairs in the polymer particles play almost no role in the polymerization inside the polymer particles because pairs of radicals produced within a volume as small as a monomer-swollen latex particle or a monomer-swollen micelle are very hkely to recombine. 

A kinetic model developed for imseeded emulsion polymerization based on the knowledge and conclusions obtained above could explain the progress of polymerization inside both the monomer droplets and the latex particles in the seeded emulsion polymerization of St initiated by AIBN at 50 °C. 

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Effect of initiator type on copolvmer properties. Copolymer IV of p-dioxanone/glycolide at 90/10 weight composition was prepared using diethylene glycol (DEG) as the initiator. Fiber properties of the resulting copolymer were determined and compared with those of Copolymer II, which was made using 1-dodecanol as an initiator (as shown in Table IV). 

In Figure 5 the predictions of the second model are compared against the experimental data published in (2) and obtained in a small, well stirred, vessel reactor with 1 It total volume. The various initiators were tested under conditions representative of polymerization in commercial units, that is with 20 60 seconds residence time and an operating pressure between 1278 and 2352 atm. For the sake of convenience we will use here the same nomenclature and dimensions as in (2). The kinetic parameters used were those given in Table I. The relative size of the two small volumes and the recirculation rates were estimated once and for all cases from equations (13) and (15). The other parameter values, determined independently, were not changed in order to obtain a better fit with the data. As can be seen, the imperfectly mixed model is in excellent agreement with the experimental data, and accurately accounts for the effect of initiator type (Figure 5). 

The effect of initiator type on the formation of cyclic oligomers manifests itself very markedly in the nonactivated anionic polymerization of CL [24]. When the process is initiated by the sodium salt of lactam, the formation of macrocycles is kinetically controlled the concentration of the cycles pronouncedly exceeds the equilibrium values, in similar fashion to cationic polymerization. In contrast, when the magnesium salts of CL or ethyl magnesium bromide are used as initiators, a considerable suppression of cyclization reactions was demonstrated for... 

Effects of Initiator Parameters. Initiator types can best be characterized by the frequency factor (k ) and the activation energy (E ), and the effect of these parameters on the molecular weight-conversion relationship is shown in Figures 7 and 8. The curves shown are the result of choosing the jacket temperature-inlet initiator concentration combination which maximizes the reactor conversion for each initiator type investigated. 

EL), conjugated polymers are also of interest as materials for optically or electrically pumped stimulated emission. For effects of this type, the ratio of stimulated emission to photoinduced absorption (PA) is of particular interest for conjugated polymers. In this context, the orign of the PA is controversial the PA can be a result of the formation of either charge-separated polaron pair -states or excimers. Initial experiments support the conjecture that LPPP 26 is significantly superior [49], as the stimulated emission of LPPP 26 is markedly more intense than that of PPV under comparable conditions. 

At both these times, thigh muscle contained a higher concentration of 2-PAM I than abdominal muscle, but a lower concentration of III. Dogs and rabbits appear, therefore, to tolerate repeated daily intravenous doses of 2-PAM I at 30 mg/kg or of III at 10 mg/kg during a period of 6-8 wk when the dally doses are suspended during each weekend. Because in this and the other studies reviewed the animals were killed at or soon after the end of the period of administration of an oxime, there has been no opportunity to judge whether repeated administration of an oxime may initiate some alteration in normal structure or function that will result eventually in a definite lesion. No truly chronic study of the toxicity of an oxime has been found. Thus, possible cryptic toxic effects of this type of compound have never been assessed. 

The effect of the type and level of initiator on polymerization time, monomer conversion, and polymer molecular weight, the effect of polymerization temperature on the crystallization behavior of the polyamide generated, and the role of a higher lactam like laurolactam on the moisture absorption characteristics of the copolymers are discussed in our previous publication [23]. 

In this paper, we try to review results obtained from anionic copolymerization of cyclic ethers with cyclic anhydrides. For a better understanding data and theoretical views on non-catalyzed copolymerizations are also included. We concentrate mainly on the kinetics and mechanism of copolymerization and the effect of the type and character of the initiator used. The influence of the epoxide and anhydride structure on copolymerization, of proton donors on the rate and course of copolymerization, and on the molecular weight of the resulting polyesters are also discussed. 

Effect of Sugar Type on Rate of Fluorescence Development Because of the quasi-linear initial rate, relative initial rate is defined in this study as Fl/hour expressed in arbitrary units. This is obtained from the 30-min observation. Maximum AFI (AFImax i-s t le maximum excess over blank at any time in the experimental run for a given sugar. 

In order to predict the total level of degradation of fines for coal handling systems of the Gladstone port, a study was commenced to examine the mechanism of lump degradation and to reduce the fines generation. The effect of different types of surface onto which the coal with initial fines was... 

The results of cushioning effects of both types of coal in Figs. 6 and 7 shows that the initial fines with lump coal does not reduce much fines generation when dropped on coal... 

The percent denitrogenation data is shown in Figure 12 on a fresh catalyst basis corrected for catalyst deactivation. Here the effect of solvent type on nitrogen removal is easily observed. The denitrogenation improved with the higher initial boiling solvents. The 580-850°F solvent showed a 7% improvement, the 660-850°F solvent a 13% improvement, and the 740-850°F solvent a 28% improvement when compared to the 500-850°F solvent. 

Effect of initial copy number For large sequence spaces, a library can only include a small fraction of all possible sequences. The maximally diverse library, the most likely type of library to result from random sampling of a large sequence space, has only one copy of each sequence. Having only one copy is a major source of noise and error in the selection. For example, in all our simulations, increasing the initial copy number of all species from 1 drastically increases both the mole fraction of the best phage and the library s average affinity in all rounds. 

The effectiveness of initiation also depends on external conditions, e. g. on type of solvent [85b]. 

Fig. 5 Effect of treatment type on the increase in tumor volume in mice inoculated with BLSC-KU cells. The animals in treatment groups received i.v. doses of doxorubicin via tumor-specific or non-specific liposomes on day 0, 3, and 7 after the initiation of treatment. The tumor-specific and non-specific liposomes were conjugated with MoAbs against leukemia cells and normal mouse IgG, respectively. (Adapted in part from Ref. l)...

The cationic polymerization of several para-substi-tuted a-methylstyrenes initiated by various Friedel-Crafts catalyst-cocatalyst combinations has been studied for the effects of catalyst type, monomer substituent and reaction solvent polarity on polymer structure and properties. By using solvent mixtures, the tacticity of the resulting polymers could be varied over a wide range, the syndiotactic form being favored in the more polar mixtures. 

It appears from this work that the chain unit structure in the organolithium polymerization of butadiene and isoprene is sensitive to certain reaction parameters even in non-polar media. This is especially true for the effect of initiator concentration and the amount and type of hydrocarbon solvent present. These effects apparently influence mainly the cis/trans ratio of 1,4 units in the chain, being largely ineffective in changing the side-vinyl content. 

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