Monomer to-catalyst ratio

Ring-opening metathesis polymerization was conducted by Verpoort et al. (4) using cyclooctene with a ruthenium Schiff base complex, (V), and proceeded with a monomer-to-catalyst ratio of 150,000 1, respectively. 

A small flask was charged with 1,4-butanediol diacrylate (0.45 mmol) dissolved in 2ml of CH2CI2 then treated with l,3-dimesityl-4,5-dihydroimidazol-2-ylidene)ben-zylidene-tricyclopentyl-phosphine ruthenium(II) dichloride (2.7 mg) and cyclooctene (0.45 mmol), the total monomer-to-catalyst ratio being 290 1. The mixture was... 

A series of homopolymerizations of norbornene and copolymerizations of norbornene and 5-decyhiorbornene were carried out at a 4000 1 monomer to catalyst ratio using catalyst 1. The polymerizations were conducted at room temperature for 1 h before short stopping the reaction. The results of these runs are presented in Tab. 4.1. 

Due to the water insolubility of these metal carbenes, aqueous polymerizations represent heterogeneous multiphase mixtures. Investigation of ROMP of the hydrophilic monomer 8 or of a hydrophobic norbomene in aqueous emulsion (catalyst precursor 7 b added as methylene chloride solution) or suspension demonstrated that the polymerization can occur in a living fashion. For example, at a monomer to catalyst ratio 8/7b = 100 with 78% yield, poly-8 of Mw/Mn 1.07 vs. polystyrene standards was obtained [68]. Using water-soluble carbene complexes of type 9 and water-soluble monomers 10, living polymerization can be carried out in aqueous solution, without the addition of surfactants or organic co-solvents [69]. 

Chemical polynKrizations were carried out in 10 ml Schlenck tub. The tubes were treated with trimethylsilyl chloride, washed with three S ml portions of methanol, dried at 120 in a oven for 12 h, flame dried and kept in a desiccator to cool down to room temperature. In a glove bag maintained under nitrogen atmosphere the lactone mixture and the catalyst (0.1 molar solution in toluene, monomer to catalyst ratio was 1 2(X)) were transferred into the polymerization tube ami capped with a rubber septum. The tubes were degassed by several vacuum purge cycles to remove the solvent in the catalyst solution and then placed in an oil bath maintained at 120 for 12 h. At the end of die reaction period, the crude sample was collected to estimate the conversion and the contents of the tubes woe dissolved in chloroform (0.5 ml) and precipated in methanol (30 ml) by vigorous stirring and methanol decanted. The precipitate was further washed with methanol (2 X 20 ml). The polymer was dried in a vacuum oven at 40 °C for 24 h and GPC data were recorded. 

A summary of ADMET polymerization of Ge- and Sn- containing polymer (1) and (2) in terms of polymerization conditions, polymer yield, and molecular weight is given in Table 1. It shows that the electrochemically reduced catalyst is an active system toward ADMET polymerization because quantitative yield for polymer (1) and (2) is 68% and 92% depending on the monomer to catalyst ratio and reaction time. The slightly higher trans polymers were obtained by this catalyst system with high yields in a short periods. 

As the monomer to catalyst ratio was increased, yield of the polymer also increased reaching to a maximum value which is around 100 1 polymer (1) or 90 1 polymer (2), and further increase of the ratio caused a decrease in the yield of the polymer. A maximum yield of 68% and 92% for polymer (1) and (2) was obtained. At high monomer concentrations deactivation of the active catalyst may occur which results in low yield of polymer. 

This group of experiments were performed for different reaction times (180-3200 min). The monomer to catalyst ratio was kept at 100 1 for polymer (1) or 90 1 for polymer (2), and the reaction was quenched by the addition of methanol after a certain time from the start of reactioa Figure 2 shows the influences of different reaction times on the amount of polymers (1) and (2). Polymerization yield first increased with time and almost reached a plateau value around 36-48 h. 

The ADMET polymerization yield of Ge- (1) and Sn (2)-containing polymers reaches a maximum at a total monomer to catalyst ratio of about 100 1 and 90 1, respectively. Polymerization reaction completed at around 36-48 h. 

Expected molecular weight from monomer to catalyst ratio. 

A representative example of a metal-based catalysis is the Ziegler-Natta process, which has been gradually improved to such an extent that the monomer-to-catalyst ratio is typically in the range 10 -10 . As a matter of fact, removal of the metallic catalyst is not needed and commodity polymers obtained in this way (polyolefins) are directly processed without any purification step. In contrast, the synthesis of specialty polymers used in niche applications requires larger amounts of metallic catalysts (the monomer-to-catalyst ratios being 10 -10 ). To prevent hazards due to the presence of toxic metallic species that can freely migrate out of the polymeric material when in service, a purification process is sometimes required which... 

Copolymerization of 1,3-propane diol and malonic acid. The polymerizations were initially run in 10 mL test tubes at atmospheric pressure. 1,3-Propane diol and malonic acid wo-e fed in a 1 1 mole ratio with a 100 1 monomer to catalyst ratio and the test tubes were immediately placed into an oil bath and allowed to react for 24 h. These initial reactions were performed at temperatures from 125-175 C at 10 C intervals. 

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