Monomer to-catalyst molar ratio

Polymerizations were carried out in chlorobenzene at 70 C for 17hr the monomer-to-catalyst molar ratio, 200. 2) Polymerization in 1,2-... 

Thermal stability of the as-polymerised PLLAs (at a [LLA]q/ [Sn(Oct)2.PPh3]o ratio of 5000), thus contaminated by the residual tin-based catalyst, has been analysed by Thermal Gravimetric Analysis. Table 4.2 shows that the degradation rate is decreased by PPhs when the monomer-to catalyst molar ratio is higher than 5000. 

The (co-)polymerization of functional monomers was also explored with the Ni and Pd catalyst systems. The multi-component Ni catalyst (Ni(O2CR)2 -i-HSbFg-i-OBFs LlyO-i-lOAlLlj) works very well for the copolymerization of norbornene and 5-triefhoxysilylnorbornene. The copolymerization of norbornene and with 5-10 mol% 5-triethoxysilylnorbomene monomers yields a high molecular weight copolymer of fhe same molar composition in excellent yield (85%) at a 4000 1 monomer to nickel molar ratio. 

Reactivity ratios between acrylated lignin model compound (Fig. 2), defined as Mi, with either MM A or S, defined as M2, were determined experimentally in accordance with standard procedures (15). These involve mixing two different vinyl monomers in various molar ratios with catalyst (i.e., benzoyl peroxide) and solvent, heating the mixture to achieve polymerization, and recovering the polymer by the addition of non-solvent, and centrifugation. The respective molar monomer fractions of the copolymer were determined by UV-spectroscopy in the cases where MMA served as M2, and by methoxyl content analysis in those cases in which S was the M2-species. The results were subjected to numerical treatments according to the established relationships of Kelen-Tiidos (17) and Yezrielev-Brokhina-Roskin (YBR) (18), and this is described elsewhere (15). 

The dependence of molar mass on the ratio of monomer to catalyst ( m/mnpioneering study on the use of ternary catalyst systems Throckmorton investigated the influence of M/ ce on dilute solution viscosities (DSV) [34], Quite surprisingly, for two catalyst systems (1) Ce octanoate/TIBA/EtAlCl2 and (2) Ce octanoate/DIBAH/HBr DSV decreased with increasing ratios of nu/nce- This observation is not at all understood and is in contradiction with the requirements for a living system. 

In 1960 Vandenberg1 observed for the first time the positive influence of water on the activity of organoaluminum catalysts in the polymerization of organic monomers. As this activity achieved its maximum for A1 to H20 molar ratios of 1 1 or 2 1 he postulated aluminoxanes (RAIO), or dialuminoxanes (R2AIOAIR2), as the active catalytic species. Since that time, many people have worked in this field trying to prepare aluminoxanes and/or dialuminoxanes, to explore their properties and most of all to determine the structures of these compounds. 

The other highly important feature of the polymerizations of this monomer is that they proceed with little if any termination and, perhaps more importantly, with little transfer. As a result, polymer degrees of polymerization approach closely to the theoretical value dictated by the molar ratio of monomer to catalyst and encourage the idea that by suitable substitution of the monomer it may yet be possible to arrive at a truly living carbocationic polymerization of an olefin. 

As are the other commercial PGA- and PLA-based synthetic absorbable sutures, the P(LA/CL) polymer is synthesized from the traditional ringopening polymerization of L-lactide and e-caprolactone in the presence of octoate catalyst at 75 to 25 molar ratio of the two co-monomers. Ihe weight-... 

Although strong Lewis acid metal halogenides are known catalysts for cationic ROP, zinc dichloride can initiate ROP of -CL, according to a coordination-insertion mechanism in which the alkyl-oxygen bond of the monomer is cleaved (Fig. 13) (72). The mechanism was assessed by computational calculations, analysis of the two chain-ends by NMR, and agreement between A/ and the monomer/zinc dichloride molar ratio. Zinc carboxylates are ROP promoters in the presence of alcohols (71,73). Similarly to tin octanoate, zinc alkoxide is formed, which is the real initiator (72,74). Side formation of octanoate ester end groups is kinetically less favorable compared with the tin counterpart (73). 

Problem 11,6 Styrene (St) was polymerized by ATRP using a copper(I) bromide (CuBr) catalyst, com-plexed with A, A, A, A, iV"-pentamethyldiethylenetriamine (PMDETA) ligand, and methyl 2-bromopropion-ate (MBrP) as initiator. Experiments were performed in 1 E mixed vessel at 110°C with excellent temperature control using a monomer to solvent (toluene) ratio of 70 30 wt% and molar ratios of 50 1 1 1 for St/MBrP/CuBr/PMDETA. Under these reaction conditions, only a portion of the catalyst species was soluble and 90% monomer conversion was obtained in 6 h. Calculate a theoretical molecular weight (MW) of the polymer obtained. How would you explain if the experimental MW is found to be higher than the theoretical... 

Figure 8.4 Conversion versus time (top) and Af , M- versus conversion (bottom) for ringopening polymerization of lactide by using the catalytic system Sn(Oct)2/l-dodecanol. Molar ratio cocatalyst-to-catalyst = 1, different molar ratios monomer-to-catalyst = 3771,...

Figure 8.5 Comparison of experimental open circles) and simulated molecular weight distributions solid lines), molar ratio monomer to catalyst = 3771 molar ratio cocatalyst to catalyst = 25 increasing conversion values (a) = 41% (b) = 92% (c) = 95% (d) = 96%. Reprinted with permission from Yu Y, Fischer EJ, Storti G, MorbideUi M. Modeling of molecular weight distribution in ring-opening polymerization of L,L-lactide. Industrial Eng Chem Res 2014 53(18) 7333—42. Copyright 2014 American Chemical Society.

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. 

Figure 5. Variation of trans-7,4 content with the molar ratio of monomer to initiator. Conditions solvent, toluene catalyst, Ba[(t-BuO)gx (OH)x] and n-BuLi.

Certain metal-carbene complexes such as [(CH3 )4N][(CO)5WCOPh] and (CO)5WC(OC2H5)Ph in combination with PR3, sulfides, sulfoxides, quinones. or /V-chlorosuccinimide, together with a TiCl4 cocatalyst, were also effective catalysts, at monomer/W molar ratios of up to 5000/1 (104). 

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