Copolymerization conditions

The mechanism of phase separation proposed here (and also observed experimentally) involves the formation in the first stage of polymer blanks1, the globules size depends on the initial comonomers and the copolymerization conditions. In the case of slow phase separation proceeding near the thermodynamic equilibrium... 

Rytter et al. reported polymerizations with the dual precatalyst system 14/15 in presence of MAO [30]. Under ethylene-hexene copolymerization conditions, 14/MAO produced a polymer with 0.7 mol% hexene, while the 15/MAO gave a copolymer with ca. 5 mol% hexene. In the mixed catalyst system, the activity and comonomer incorporation were approximate averages of what would be expected for the two catalysts. Using crystallization analysis fractionation (CRYSTAF) and differential scanning calorimetry (DSC) analysis, it was concluded in a later paper by Rytter that the material was a blend containing no block copolymer [31],... 

COPOLYMERIZATION CONDITIONS AND SOME PROPERTIES OF RESULTING COPOLYMERS... 

The phase transition is directly related to the hydrophilic/hydrophobic balance in a copolymer and controlling the polymer composition provides a highly effective way of tuning the LCST. Another example of responsive polymer libraries was based on the combination of 2-hydroxypropyl acrylate and DMA or A-acryloyl morpholine [50]. The nitroxide mediated copolymerization conditions were chosen on the basis of the kinetic investigation of the homopolymerizations, as discussed in this chapter (see, e.g., Sect. 2.1.2). 

Figure 6.13 Radical polymerization of a growing polymer chain in the presence of two distinct monomers (i.e., copolymerization conditions) can at every step incorporate one monomer or the other. How might one quantitatively go about estimating the intrinsic preference for one monomer over the other What other molecular properties expected to correlate with this discrimination might be subject to computation ...

In a typical ethylene copolymerization condition, the comonomer (i.e. p-methylstyrene) was mixed with solvent (toluene or hexane) and methylaluminoxane (MAO) (30 wt% in toluene) needed in a Parr 450 ml stainless autoclave equipped with a mechanical stirrer. The sealed reactor was then saturated with 45 psi ethylene gas at 30 or 53 °C before... 

The same trend as that reported by the Nozaki group upon dilution was observed. The copolymerization conditions were 60°C and 40 bar CO2, with a PO/Cr ratio of 20,000 1, the TOF of the optimal dinuclear complex was 82 h, whereas the mononuclear analogue showed a TOF of just 7 h ... 

Copolymerization Conditions. It is necessary to use a 1-butene as pure as possible. 2-Butene and isobutene greatly inhibit the copolymerization reaction (Figure 1). 

Figure 2 shows a series of cloud-point curves determined for the system ethylene-2-ethylhexyl acrylate-poly(ethylene-co-2-ethylhexyl acrylate). Each cloud-point curve corresponds to one stationary copolymerization condition in CSTR1. The compositions and concentrations referring to the five monomer-polymer mixtures, including one ethylene homopolymerization reaction (Experiment 1), are listed in Tab. 1. FA is the concentration of the acrylate units within the copolymer (in mole-%),/P and/A denote the concentrations of polymer and of acrylate monomer in the monomer-polymer mixture, respectively. As can be seen from Fig. 1 and from Tab. 1, increasing acrylate content in the copolymer lowers the cloud-point pressure. 

The donor molecules usually have e values (Section 7.11) of less than 0.5. Monomers with negative e values are especially effective. Acceptor molecules have higher e values. Copolymerization conditions can be fairly mild for conjugated donor monomers but use of nonconjugated donors requires more careful selection of reactants and conditions. 

OFM are viscous liquids, or readily fusible resinTike substances, capable (in the presence of intiators or upon irradiation) of three-dimensional radical copolymerization with several active monomers (styrene, vinyltoluene, methylmethacrylate and others). The properties of the network copolymers formed largely depend on the chemical nature of the reagents and the copolymerization conditions. Hardening of OFM may be carried out at room temperature, or even lower, using mixtures... 

Much effort has been devoted over the last few years to preparing branched cellulose or cellulose derivatives, by combining the cellulose backbone with a synthetic polymer which confers desirable properties. The length of these branches or grafts varies considerably, depending on the copolymerization conditions. The most widely used monomers are acrylic and vinyl monomers, with the following order of reactivity [16] ethyl acrylate > methyl methacrylate > acrylonitrile > acrylamide > styrene. 

The copolymerization of TXN and St was analysed in a number of papers 150,151 in terms of conventional reactivity ratios without paying attention to the proper characterization of copolymers and other factors discussed in this volume (cf. Chap. 15). Some additional information comes from the studies of similar systems, i.e. DXL-St copolymerization 152). Also in this case product characterization mainly involved solubility studies, although Yamashita et al. claimed that 1H-NMR spectra confirmed that the product is indeed a true copolymer. This claim was based on a rather limited analysis of H-NMR spectra, however, and was not confirmed by analysis of spectra of related models. Copolymerization conditions were as follows [DXL]0 = 0.7 - 3.7 mol l [St]0 = 4.5 — 2.7 mol l-1, [BF3 OEt2] = 2,5 10-2 mol 1 1, 25 °C, in toluene. After 2-8hrs, from 2% to 9% product with fr ] = 0.12 — 0.32 dl g-1 (viscosity determination conditions not specified) was obtained. 

Copolymerization of hydrosiloxanes was studied without taking into account reversibility (cf. Sect. 15.1), and perhaps this was a reason for the observed dependence of reactivity ratios on copolymerization conditions. Thus, in the copolymerization of D4 with D4 rt = r2 = 1 for 22 wt % of comonomers in CH2C12 solvent, whereas Tj = 1.26 and r2 = 0.82 for 50 wt %, and 2.2 and 0.3 respectively in bulk. 

Copolymerization of 18 with styrene and acrylonitrile In the range of 40 to 60 mol % of the metallomonomer the copolymer composition does not depend on the monomeric mixture. The copolymers are soluble in benzene the molecular weights are about 10 Da. Under copolymerization conditions (75 °C, benzene, 1% of the initiator) of 18 with acrylonitrile (25 mol %) a light-yellow product containing -12% vanadium was obtained. The yield was 15%, the product is soluble in DMFA and DMSO, and its intrinsic viscosity was 0.11 (DMSO, 30 °C). IR 1720 (vc=o), 2245 cm (vc n) the ratio of the intensities of the absorptions /(C=0)//(C=N) = 13 1. This method can also be used for the synthesis and polymerization of optically active metallomonomers. 

Most of the monomers do not homopolymerize under the copolymerization conditions. Alternating copolymers are exclusively formed, since, ideally, the copolymerization only occurs after the prior formation of dimeric zwitterions. Thus, this joint polymerization of the two monomers is actually a homopolymerization of the zwitterion. 

A Copolymerization Conditions Poly((l-amido-1-methylene)-co-(sodium... 

The copolymerization of nonconjugated dienes with monoolefinic vinyl monomers is also known.Depending upon the comonomer pair and the copolymerization conditions, the product copolymer may contain (1) cyclized units made from sequential addition of both ends of the diene monomer (2) cyclized units made from addition of one end of the diene followed by the monoolefin comonomer or one side of a second diene, followed by the other end of the first diene (3) non-cyclized diene units bearing pendant olefins, and (4) crosslinked dienes formed by incorporation of these pendant olefins into another polymer chain (Scheme 19.1). For symmetrical, nonconjugated dienes, it has been shown that all of the well-known methods of polymerization can be employed to... 

Table 1. The composition of OCM-2 - styrene mixture and their copolymerization conditions [40]...

Copolymerization conditions Catalyst = O.lg, Al/Ti o 30 mole ratio each vol. of heptane = 100cm Total pressure = latm T = 30 0 t = lOmin E and P denote ethylene and propylene respectively. 

Methyl methacrylate-MA copolymerizations and property studies of the copolymers have also received substantial attention.Conditions have been developed for preparing alternating (1 1) copolymers of methyl methacrylate-MA (see Chapter 10). However, typical copolymerization conditions produce random copolymers. Binary mixtures of the monomers have been copolyirier-ized in solution, with peroxide initiators at 60°C and at pressures <4 000 atm. In benzene solvent, the specific viscosity (rjsp) of the copolymers varied from 1.10 to 5.27, as pressure increased from 1 to 4 000 atm. The composition of the copolymers was almost independent of pressure. The rates of copolymerization under these conditions increased from 4.34 to 194.0 %/h. The copolymerization rate constant for the pair, at 25°C, has been estimated as 40 liters morS The rate increase, which results from increasing chain propagation rate constants (Rp) with increasing pressure, was of the same order observed for homopolymerization of methyl methacrylate. 

The product of the polymerization constants, riT2, is very frequently used as an index for evaluating the alternating tendency in binary copolymeriz-ation/" In fact, the reciprocal of the product rir2 is often called the alternation tendency index. The ideal (random) copolymerization condition exists for the case / i/ 2 = Where ri and r2 are very low and the rir2 product tends to zero the alternating tendency increases.The product r r2 can be zero in two cases—where one or both reactivity ratios are zero. Where r — 0, the copolymer chain is built of isolated Mi units separated by sequences of M2 monomer units. Strictly alternating copolymer would be obtained when both / i and V2 are zero. The second condition is often found for MA copolymerizations, as described in Chapter 10. Where ri > 1, the polymer is richer in Ml monomers than the monomer feed. For ri < 1, the opposite holds. 

The aa- and -monomers, i.e., dimethallylidenepentaerythritol 28B and dicrotyllidenepentaerythritol 28C, under the same free-radical-initiated copolymerization conditions, also give copolymers with MA. Copolymerizations must be carried to low conversion to get soluble copolymers. In all three cases, the maximum rates of copolymerization occurred at a monomer mixture ratio of (28A-28C)/MA of 0.5. Copolymer compositions and IR and NMR studies indicated that 1 1 copolymerization was achieved between each vinyl residue and MA. ... 

In all cases, the copolymers are essentially equimolar regardless of the composition of the monomer feed, and the various copolymerization conditions serve only to cause variations of the copolymer microstructure. For example, the infrared spectrum of a copolymer prepared at 80°C, using -butyl peroxypivalate in cyclohexanone solvent, showed approximately 85-90% cis-1, units.In contrast, the infrared spectrum of a copolymer prepared in benzene solvent at 60°C with AIBN has approximately 74% cis-1,4 units. A homopolymer of butadiene, prepared under the same conditions, has approximately 62% trans-1,4 residues. 

Solution copolymerization of the MA-styrene pair has been studied in acetone at high pressure (1-4 kbars). At 40°C, the copolymerization reaction rate between MA and the growing polymer chain, having a MA unit preceding the active styrene moiety, increased with pressure for both bulk and solution copolymerizations condition. Thus, Enomoto and coworkers conclude the penultimate effect diminishes or disappears with pressure escalation. Composition and infrared studies show a 1 1 alternating structure for the material, over a wide range of monomer concentration of one component. 

The 2,3-dihydrofuran-MA copolymerization is essentially always 1 1, with the monomer composition not affected by the conversion under the copolymerization conditions [Mi] = [M2]. This being true, the copolymerization rate can be expressed as follows (where [Mi] = [M2] and Ri is the rate of initiation) ... 

Charging the deionized water, the solvent, and the surfactant to the reactor followed by rapid stirring to form a microemulsion started a typical polymerization run. The reactor was evacuated and purged with tetrafluoroethylene to ensure that oxygen content was below 30 ppm. The temperature of the reactor was increased to and maintained at 80°C. A quantity of HFP was precharged to the reactor followed by pressurization to 3.15 MPa using TFE. An aqueous solution of ammonium persulfate was pumped into the reactor to start the reaction. Pressure was held constant at 3.1 MPa for the duration of the reaction, which was stopped by discontinuing the flow of TFE into the reactor. Table 5.21 presents two examples of TFE/HFP copolymerization conditions and copolymer properties. 

Table 5.21. Examples of TFE/HFP Copolymerization Conditions and Copolymer PropertiesP ) ...

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