Methyl acrylate constants

The molecular weight of a polymer can be controlled through the use of a chain-transfer agent, as well as by initiator concentration and type, monomer concentration, and solvent type and temperature. Chlorinated aUphatic compounds and thiols are particularly effective chain-transfer agents used for regulating the molecular weight of acryUc polymers (94). Chain-transfer constants (C at 60°C) for some typical agents for poly(methyl acrylate) are as follows (87) ... 

Giese and Kretzschmar7j found the rate of addition of hexenyl radicals to methyl acrylate increased 2-fold between aqueous tetrahydrofuran and aqueous ethanol, Salikhov and Fischer74 reported that the rate constant for /-butyl radical addition to acrylonitrile increased 3.6-fold between tetradecane and acetonitrile. Bednarek et al75 found that the relative reactivity of S vs MMA towards phenyl radicals was ca 20% greater in ketone solvents than it was in aromatic solvents. 

The susceptibility of the polymerization of a given monomer to autoacceleration seems to depend primarily on the size of the polymer molecules produced. The high propagation and low termination constants for methyl acrylate as compared to those for other common monomers lead to an unusually large average degree of polymerization (>10 ), and this fact alone seems to account for the incidence of the decrease in A f at very low conversions in this case. 

The butadiene is the limiting reagent and conversions will be expressed in terms of this species. Over the composition range of interest there will always be sufficient methyl acrylate present to tie up the aluminum chloride. Consequently the concentration of the complex (A1C13-M) will remain constant throughout the length of the reactor at a value equal to the initial A1C13 concentration. For these conditions the reaction rate expression is the form... 

The formation of the hydrogen bond between hydroperoxide and polar monomer, for example, methyl acrylate or acrylonitrile, does not influence the rate constant of the reaction of hydroperoxide with the double bond of monomer [101]. The values of the rate constants of the reaction of hydroperoxide with olefins are given in Table 4.13. The effect of multidipole interaction was observed for reactions of hydroperoxide with polyfunctional monomers (see Table 4.14, Ais the Gibbs energy of multidipole interaction in the transition state). 

Figure 4. Initiation Rate Constant (kj) for the Thermal Degradation of a Vinylidene Chloride/Methyl Acrylate (Five Mole Percent)/ 4-Vinylpyridine (0.1 Mole Percent) Terpolymer at 170 °C.

Density functional theory has been used to investigate the Diels-Alder reactions of triazolinedione with s-cis- and. y-fran -butadiene. " Combined quantum mechanics-molecular mechanics calculations have been used to investigate the asymmetric Diels-Alder reaction of cyclopentadiene with the complex dienophiles AICI3-methyl acrylate and methoxyaluminium dichloride-acrolein.Equilibrium constants have been determined for the molecular complexes formed from 1-alkyl-1-(2-naphthyl)ethenes and 1-vinylnaphthalene with TCNE in C1(CH2)2C1 at 27.1 °C ... 

At 24 °C and 15-60 bar ethylene, [Rh(Me)(0H)(H20)Cn] catalyzed the slow polymerization of ethylene [4], Propylene, methyl acrylate and methyl methacrylate did not react. After 90 days under 60 bar CH2=CH2 (the pressure was held constant throughout) the product was low molecular weight polyethylene with Mw =5100 and a polydispersity index of 1.6. This is certainly not a practical catalyst for ethylene polymerization (TOP 1 in a day), nevertheless the formation and further reactions of the various intermediates can be followed conveniently which may provide ideas for further catalyst design. For example, during such investigations it was established, that only the monohydroxo-monoaqua complex was a catalyst for this reaction, both [Rh(Me)3Cn] and [Rh(Me)(H20)2Cn] were found completely ineffective. The lack of catalytic activity of [Rh(Me)3Cn] is understandable since there is no free coordination site for ethylene. Such a coordination site can be provided by water dissociation from [Rh(Me)(OH)(H20)Cn] and [Rh(Me)(H20)2Cn] and the rate of this exchange is probably the lowest step of the overall reaction.The hydroxy ligand facilitates the dissociation of H2O and this leads to a slow catalysis of ethene polymerization. 

Compositionally uniform copolymers of tributyltin methacrylate (TBTM) and methyl methacrylate (MMA) are produced in a free running batch process by virtue of the monomer reactivity ratios for this combination of monomers (r (TBTM) = 0.96, r (MMA) = 1.0 at 80°C). Compositional ly homogeneous terpolymers were synthesised by keeping constant the instantaneous ratio of the three monomers in the reactor through the addition of the more reactive monomer (or monomers) at an appropriate rate. This procedure has been used by Guyot et al 6 in the preparation of butadiene-acrylonitrile emulsion copolymers and by Johnson et al (7) in the solution copolymerisation of styrene with methyl acrylate. 

Either addition sequence works if the two monomers are in the same family (e.g., methyl acrylate and butyl acrylate or methyl methacrylate and butyl methacrylate or styrene and 4-acetoxystyrene), because the equilibrium constants (for activation) for both types of chain ends have about the same value. The situation is usually quite different for pairs of monomers from different families. Chain ends from monomers with large equilibium constants can initiate the polymerization of monomers with lower equilibrium constants thus, cross-propagation is efficient. Methacrylate works well as the first monomer to form methacrylate-acrylate and methacrylate-styrene blocks. 

Figure 6.7 Hydrogen-bonding (thio)ureas screened in the DABCO-promoted MBH reaction between benzaldehyde and methyl acrylate the pseudo-first-order rate constants relative to the uncatalyzed reaction are given in h . ...

Confirmation was provided by the observation that the species produced by the photolysis of two different carbene sources (88 and 89) in acetonitrile and by photolysis of the azirine 92 all had the same strong absorption band at 390 nm and all reacted with acrylonitrile at the same rate (fc=4.6 x 10 Af s" ). Rate constants were also measured for its reaction with a range of substituted alkenes, methanol and ferf-butanol. Laser flash photolysis work on the photolysis of 9-diazothioxan-threne in acetonitrile also produced a new band attributed the nitrile ylide 87 (47). The first alkyl-substituted example, acetonitrilio methylide (95), was produced in a similar way by the photolysis of diazomethane or diazirine in acetonitrile (20,21). This species showed a strong absorption at 280 nm and was trapped with a variety of electron-deficient olefinic and acetylenic dipolarophiles to give the expected cycloadducts (e.g., 96 and 97) in high yields. When diazomethane was used as the precursor, the reaction was carried out at —40 °C to minimize the rate of its cycloaddition to the dipolarophile. In the reactions with unsymmetrical dipolarophiles such as acrylonitrile, methyl acrylate, or methyl propiolate, the ratio of regioisomers was found to be 1 1. 

Rates of radical additions to alkenes are controlled mainly by the enthalpy of the reaction, which is the origin of regioselectivity in additions to unsymmetrical systems, with polar effects superimposed when there is a favorable match between the electrophilic or nucleophilic character of the radical and that of the radico-phile. For example, in the addition of an alkyl radical to methyl acrylate (2), the nucleophilic alkyl radical interacts favorably with the resonance structure 3. Polar effects are apparent in the representative rate constants shown in Figure 4.14 for additions of carbon radicals to terminal alkenes. Addition of the electron-deficient or electrophilic rert-butoxycarbonylmethyl radical to the electron-deficient molecule methyl acrylate is 10 times as fast as addition of... 

Acrylonitrile (Figure 9) shows two periods of almost constant but different absolute reaction rates, followed by a period of first-order reaction rate at a high conversion. This monomer is somewhat similar to vinylidene chloride since it also does not swell in its own polymer. On the other hand acrylonitrile has a water solubility roughly three orders of magnitude higher than vinylidene chloride or styrene and even higher than methyl acrylate (see Table I). We therefore have to assume particle formation in the aqueous phase, as was done for methyl acrylate emulsions. 

The rates of cycloaddition of methyl acrylate with six 1-substituted pyridinium-3-olates have been studied, A Hammett plot of the second-order rate constants against tr values of the substituents gave satisfactory correlation. 272.373... 

A constant fraction of the monomer is converted to graft copolymer for the reactions of methyl methacrylate and methyl acrylate with SBS this is independent of the amount of monomer and the amount of initiator. Both homopolymer and graft copolymer are formed and 25 - 30% of the monomeric methyl methacrylate reacts to form the graft copolymer while the remainder forms homopolymer the fraction of graft copolymer is close to 40% for methyl acrylate. This is also true for the reaction of acrylonitrile with polystyryllithium, here the amount of graft copolymer is a little lower, in the range of 15 - 20%. ... 

This tertiary amine group terminated polymer can undergo transfer in the presence of a second monomer (25, 26), e.g. with acrylonitrile or methyl acrylate which show an exceptionally high transfer constant with such groups (see Table 2). By this method acrylonitrile blocks are bounded to polymethyl methacrylate sequences the overall composition of these block copolymers may be represented by... 

---