Solution copolymerizations experiments

Table III lists the initial solution copolymerization experiments conducted using vinyl ester monomers. Since our main objective is the synthesis of polymers for durable coatings, these experiments were conducted using more hindered vinyl monomers which are reported to have better durability than vinyl acetate.

Barrett and Thomas (10)proposed that these effects of differential monomer adsorption could be modeled by correcting homogeneous solution copolymerization reactivity ratios with the monomer s partition coefficient between the particles and the diluent. The partition coefficient is measured by static equilibrium experiments. Barrett s suggested equations are ... 

No triester of levoglucosan was found92 that polymerized at temperatures much below 0°. At —78°, the triacetate complexed with phosphorus pentafluoride, and, at high concentration, precipitated from solution.91 The tris(monofluoroacetate) failed to polymerize under a variety of conditions.91 The trinitrate polymerized at 0°, but the product was not fully characterized.92 Polymerization of the triacetate proceeded to reasonable conversions with a number of catalysts at 0°, but the viscosity and the stereoregularity of these polymers were low.92 In a simple, copolymerization experiment, it was demonstrated that the low polymerizability of levoglucosan triacetate was due not only to a failure to initiate but also to sluggish propagation.92... 

Solution Copolymerizations. Our primary objective in this preliminary study was to gain a qualitative understanding of the copolymerization behavior of VEC with various types of unsaturated monomers. Particularly, we wanted to determine if VEC could be incorporated into a variety of polymer types of interest to the coatings industry. Since VEC is used to provide cyclic carbonate functionality for subsequent reaction or crosslinking, limited amounts of VEC are used in the copolymerizations. A semi-batch process was used in the copolymerization experiments to approach starved-feed conditions. Starved-feed conditions can result in copolymers with more uniform composition since the conversion is kept high in the reactor. While there are a large number of variables to consider, we elected to focus on monomer composition, polymerization temperature, and initiator level. 

Apparent reactivity ratios obtained directly from suspension polymerization experiments may not be identical to those expected from the equivalent bulk processes if some monomer migrates to the continuous phase. Ashady et al. [10] found values for reactivity ratios that were not expected from results observed in bulk or solution copolymerization. Izumi and Kitagawa [11] showed that reactivity ratios for suspension copolymerization, of acrylonitrile and methyl acrylate, were different from those obtained from either solution or emulsion polymerization. Table 5.1 compares reactivity ratios obtained from solution copolymerization with those observed in suspension copolymerization. 

Unfortunately there seems to be no supplementary evidence on copolymerization initiated by phosphines. In a typical experiment, a solution of acrylonitrile in petroleum ether is treated with a little triethyl phosphine. A greenish-brown product settles on the walls of the flask. It is soluble in acetone, furfural, methyl ethyl ketone and DMF. Polymer precipitated from acetone by toluene is of low molecular weight and contains perhaps 0.5% combined phosphorus. In similar experiments it is possible to obtain pale yellow polymers with number average molecular weights of around 30,000 and with about one atom of P per polymer chain. On the basis of these results Horner and coworkers proposed the scheme (72) ... 

Thus, it is possible to provide homogeneous solution polymerization systems providing the solubility parameters of the monomer, polymer, and solvent are known. Styrene and maleic anhydride were copolymerized by both techniques in the experiments described in this report. 

An immobilized Ru-PyBOx catalyst 56 was synthesized by thermally induced radical copolymerization and used to catalyze the flow cyclopropanation reaction between styrene and ethyldiazoacetate (Scheme 4.79), building on initial work performed in batch [179]. For the flow example, a range of experiments using the starting materials in CH2C12 solution, neat or in scC02 were assessed and the results are summarized in Table 4.2 [180],... 

Hence, within the framework of the traditional kinetic model (2.8) there is a mathematically rigorous solution of the problem of the calculations of the azeotropic composition x under the copolymerization of any number of monomer types knowing their reactivity ratios, i.e. the elements of matrix ay. However, since the values of au can be estimated from the experiment with certain errors Say, the calculated location of azeotrope x is also determined with an accuracy, the degree of which is characterized by vector 8x with components 8xj (k = 1,2,..., m) and modulus 8X ... 

In some very remarkable experiments, Bystrom et al. [77] were recently able to demonstrate high regio- and stereoselectivity in reactions inside the imprinted cavity. The steroid 12 was copolymerized as the template monomer, and removed by reduction. The hydroxyl group in the polymer newly formed from the carboxyl group was converted into an active hydride by LiAlH4. With the help of this polymer, androstan-3,I7-dione was reduced to the alcohol exclusively in position 17, whereas in solution or with a polymer with statistically distributed hydride groups it is reduced exclusively in position 3. 

A study of the microstructure of copolymers made use of a simple solution procedure for the copolymerization of methyl acrylate (MA) with A-vinylcarba-zole (NVK). The ratio of the feed composition ranged from (0.1429 moles of MA to 1.00 of NVK) to (7 moles of 1 of NVK)—a 49-fold range in composition. The experiments were carried out to high conversions [41]. Preparation 2-8 is based on this work. The reactivity ratios calculated from this series were approximately... 

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