Polymerization studies

Polymerization Studies. Anionic Polymerization of Caprolactam (the use of (CFs C0)20 (ca. 2 mole %) enabled a lower reaction temperature to be employed and higher yiel and polyamide molecular weights to be obtained]. Soil-retardant Finishing of Cotton Ooth by Vapour-phase Graft Polymerization of Fluoroalkyl Acrylates. Radical Polymerization of a-Fluoroacrylic Acid and -Vinylpyrrolidone in an Aqueous Solution. Perfluoropolyether Esters of Quinones [the preparation of the title compounds by reaction of 1.5-dihydroxyanthraquinone with per-fluoropolyetheracyl fluorides, e.g. CFj-CFi-CF -O-CF(Ci )-CaPj-O-CF(CF,)-C50F, is 

Similar to its analog complex 2, complex 3b is well-controlled for lactide polymerization displaying good agreement between theoretical and experimental molecular weights, albeit with higher dispersity values. In contrast to complex 2, complex 3b shows a moderate heterotactic bias (P 0.6), suggesting chain-end control, not enantiomorphic site control, is responsible for the moderate selectivity of the system 

Glassware was cleaned with aqueous carbitol, rinsed with dilute HQ and with distilled water. The culture tubes were dried in an oven at IS) °C overnight and cooled to room temperature in the dry box under nitrogen. 

Polymerizations were generally carried out as follows Gaseous reagents, i.e.,isobutylene, methyl chloride, were passed through drying columns and condensed in the bath and collected in culture tubes. 

Precooled coinitiator solution was rapidly added to precooled solution of monomer and initiator while shaking the culture tube. Polymerizations were terminated generally 

In experiments in which the effect of monomer concentration was studied the polarity of the medium was maintained by replacing aliquots of the monomers by /i-hexane cosolvent, so that the total volume of n-hexane and monomer remained constant. This technique was also used in model studies. 

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The controlled synthesis of polymers, as opposed to their undesired formation, is an area that has not received much academic interest. Most interest to date has been commercial, and focused on a narrow area the use ofchloroaluminate(III) ionic liquids for cationic polymerization reactions. The lack of publications in the area, together with the lack of detailed and useful synthetic information in the patent literature, places hurdles in front of those with limited loiowledge of ionic liquid technology who wish to employ it for polymerization studies. The expanding interest in ionic liquids as solvents for synthesis, most notably for the synthesis of discrete organic molecules, should stimulate interest in their use for polymer science. 

Table 7 The Dispersion Polymerization Studies on Alkylcyanoacylates in the Aqueous Media...

Prior to polymerization studies extensive model experiments have been carried out for guidance in selecting suitable preparative conditions. The next section concerns model experiments it is followed by two sections concerning polymerization of a-methyl-styrene and isobutylene, respectively. 

As a prelude to polymerization studies, extensive model experiments have been carried out to define conditions under which the Si-H bonds in HnSi(CH3)3 CH2CH2[Pg.30]

Important conclusions regarding the polymerization study were ... 

The following kinetic scheme, usually adopted in free radical polymerization studies, is considered ... 

Synthesis of active Ni(II) a-diimine catalysts for ethylene polymerization study on substituent and cocatalyst effects... 

The presence of methylenic bands shifted at higher frequency in the very early stages of the polymerization reaction has also been reported by Nishimura and Thomas [114]. A few years later, Spoto et al. [30,77] reported an ethylene polymerization study on a Cr/silicalite, the aluminum-free ZSM-5 molecular sieve. This system is characterized by localized nests of hydroxyls [26,27,115], which can act as grafting centers for chromium ions, thus showing a definite propensity for the formation of mononuclear chromium species. In these samples two types of chromium are present those located in the internal nests and those located on the external surface. Besides the doublet at 2920-2850 cm two additional broad bands at 2931 and 2860 cm are observed. Even in this favorable case no evidence of CH3 groups was obtained [30,77]. The first doublet is assigned to the CH2 stretching mode of the chains formed on the external surface of the zeolite. The bands at 2931 and... 

A carefully prepared copolymer of the desired 70/30 proportions dissolved readily in the acetonitrile mobile phase. However, insoluble polymer was detected in all three large scale polymerizations studied. As illustrated in Figure 7, two hour samples contained a significant fraction of insoluble polymer. After a four hoiu reaction amount of insoluble polymer was not significantly changed, while amount of soluble polymer approximately doubled. After polymerizing six hours there was only a modest increase in amount of soluble polymer, but amount of insoluble polymer doubled. Thus, insoluble polymer was formed very early and very late in the reactions, and this was the case in each of the polymerizations studied. 

Amount of soluble polymer generated in this reaction (Figure 9) was only 18-19% solids, which was well below the 29% total solids found after reaction completion. Differences between calculated soluble solids and gravimetrically measured total solids were large, but variable, for all three polymerizations studied. Thus, amount of soluble polymer was not proportional to total solids. However, a good correlation between total solids and the sum of refractometer peak areas for both polymer peaks was obtained. Figure 10. This correlation included all three polymerizations and there was little or no batch bias. 

Initial polymerization studies were conducted with 2,2 -tetramethylenebls(4,4-dimethyl-2-oxazolin-5-one) 4 and... 

From our cationic polymerization studies of isopropenyl organometailic monomers, it can be concluded that structural and electronic... 

Whenever it is possible, by suitable purification techniques, to prepare a non-reacting mixture of catalyst and monomer, and then to start reaction by addition of a third substance, the question as to the need for a co-catalyst in that particular system is settled, and the way is open for the investigation of various co-catalysts. This is the rationale behind the stopping experiments which are such a characteristic feature of cationic polymerization studies. 

The presence of trace amounts of water in the organic phase is known to affect profoundly the rate of solid-liquid PTC processes. [11-13] Only recently has this problem been addressed by work in our laboratory as well as by Liotta and Sasson. Early in our polymerization studies we found that PTC polymerization did not occur in "bone dry" or "wet" solvents. Consequently, we undertook a... 

The following monomers were chosen to be used in polymerization studies that aimed at obtaining polymeric high-energy compounds [3] ... 

Why were free radicals polymerizations studied so well ... 

Organometallic compounds containing polymerizable carbon-carbon double bonds have been synthesized and their polymerization studied [Archer, 2001 Pittman et al., 1987]. Among the organometallic monomers studied are vinylferrrocene and trialkyltin methacrylate. Much of the interest in these polymerizations has been to obtain polymers with... 

Spontaneous polymerization of 4-vinyl pyridine in the presence of polyacids was one of the earliest cases of template polymerization studied. Vinyl pyridine polymerizes without an additional initiator in the presence of both low molecular weight acids and polyacids such as poly(acrylic acid), poly(methacrylic acid), polyCvinyl phosphonic acid), or poly(styrene sulfonic acid). The polyacids, in comparison with low molecular weight acids, support much higher initial rates of polymerization and lead to different kinetic equations. The authors suggested that the reaction was initiated by zwitterions. The chain reaction mechanism includes anion addition to activated double bonds of quaternary salt molecules of 4-vinylpyridine, then propagation in the activated center, and termination of the growing center by protonization. The proposed structure of the product, obtained in the case of poly(acrylic acid), used as a template is ... 

The authors thus concluded that the polymerization studied was affected by the template. The rules observed for polymerization of 4-vinylpyridine in the presence of low molecular weight acids and polyacids can be summarized as in the Table 4.1. ... 

The most complete insights into the behavior of mixtures of nonpolymeriz-able lipids have come from the phase diagrams of these systems. These data have provided important reference points for the polymerizable lipid systems described next, even though few phase diagrams have been reported for polymerizable lipid mixtures. In spite of this deficiency the polymerization studies have... 

Some experimental data that were obtained through a series of polymerization studies with a methacrylate-terminated MACROMER with vinyl chloride are shown in Figure 12. The Alfrey-Goldfinger equation was used to calculate the copolymer composition for comparison to the actual copolymer composition as estimated from GPC analysis. A reasonably close agreement was achieved of the actual and the theoretical copolymer compositions, which indicates that the r values are in the region of r2 = 10 and r2 = 0.1. 

In some instances of electrolytic polymerization studies, it is conceivable that the polymerization may proceed simultaneously by a free-radical, an anionic, or a cationic mechanism in the same reaction mixture. To discriminate among the various propagation mechanisms, the analysis of copolymer compositions is often used. 

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