Polymerization of double bonds

Kuchanov and Pismen (94) have also applied their method to batch polymerization of a diene in which cross-linking by co-polymerization of double bonds in the polymer occurs as would be expected, the second moment diverges more rapidly than when this mode of reaction is absent. 

In this review article, templated syntheses of macromolecules and polymeric materials will be discussed in which a low-molecular-weight template controls the structure of macromolecules. The composition (e.g., the proportion of co-monomers), the sequence of co-monomers as well as the stereochemistry (including the chirality) of the newly formed stereogenic centers is controlled during the polymerization of double bonds. 

Oxypolymerized Oils Direct polymerization of double bonds can be achieved by oxidative polymerization via the free radical mechanism. Oils containing high content of unsaturation (drying and semidrying) can be oxidized with the atmospheric oxygen to form highly branched materials or cross-linked polymers [76]. 

Various aromatic and heteroaromatic aldehydes were coupled with styrenes in the presence of catalytic quantities of CuClj and TBHP at 80 °C. The procedure is remarkably selective, and the products detected arise from the acylation of the a,p-unsaturated ketone or radical polymerization of double bonds. The mechanism proceeds via the Cu-assisted generation of an acyl radical that adds onto the double bond of the olefin. Oxidation by the Cu... 

In the EPDM polymerization, the double bond of the bicycloheptene ring system of ENB is involved. The amount of third monomers used in any polymerization varies, but it is usually present at less than 10 wt% of the finished polymer. 

When monomer units add directly to one another, the result is an addition polymer. Table 23.1 lists some of the more familiar synthetic addition polymers. You will notice that each of these is derived from a monomer containing a carbon-carbon double bond. Upon polymerization, the double bond is converted to a single bond ... 

Olefin metathesis, an expression coined by Calderon in 1967,1 has been accurately described in Ivin and Mol s seminal text Olefin Metathesis and Metathesis Polymerization as the (apparent) interchange of carbon atoms between a pair of double bonds (ref. 2, p. 1). This remarkable conversion can be divided into three types of reactions, as illustrated in Fig. 8.1. These reactions have been used extensively in the synthesis of a broad range of both macromolecules and small molecules3 this chapter focuses on acyclic diene metathesis (ADMET) polymerization as a versatile route for the production of a wide range of functionalized polymers. 

Natural rubber latex, obtained from rubber trees, is converted to its final form by a process known as vulcanization, first discovered by Charles Goodyear in 1839. Vulcaiuzation is basically a crosslinking reaction of double bonds in the latex structure with sulfur. The polymerization of butadiene with itself or with other vinyl monomers results in a material that like natural latex, still contains double bonds. Thus, synthetic rubber made from butadiene can be processed and vulcanized just like natural rubber. 

DSP crystal, a detailed picture of the lattice motion and related displacements was constructed and related to the topochemical postulate and the mechanism of phonon assistance. Holm and Zienty (1972) have measured the quantum yield for the overall polymerization process of a,a -bis(4-acetoxy-3-methoxybenzylidene)-p-benzenediacetonitrile (AMBBA) crystals in slurries and reported it to be 0.7 on the basis of the disappearance of two double bonds ( = 1.4 if assigned on the basis of the number of double bonds consumed). 

Kinetic investigations demonstrate that the order of the network formation is nearly unity (see Fig. 1). This result agrees with the polymerization kinetics [3], The formation of the network and the decrease of double bond follow the same kinetic law. 

When heating treatments are applied to obtain stand oils, the following chemical modifications are likely to occur cross-linking of triacylglycerols, isomerization of double bonds, and formation of dimers through Diels-Alder cyclization [50,51]. As a result of double bond isomerization, the amounts of suberic and sebacic acids increase with respect to azelaic acid. Consequently, the ratio of suberic acid to azelaic acid may help to indicate a pre-polymerized oil [52,53]. 

During conventional polymerizations of both HEMA and DEGDMA, complications resulting from diffusion limitations to termination and propagation are observed. Features such as autoacceleration, autodeceleration and incomplete conversion of double bonds characterize the rate behavior of these polymerizations. As TED is added to the reacting system, the carbon-DTC radical termination reaction is introduced. Diffusion limitations to carbon-DTC radical combination are lower than those to carbon-carbon radical termination as the DTC radical is smaller and much more mobile than a typical polymeric carbon radical. As a result, the cross-... 

An alternative method to make PAEs is the acyclic diyne metathesis (ADIMET) shown in Scheme 2. It is the reaction of a dipropynylarene with Mo(CO)6 and 4-chlorophenol or a similarly acidic phenol. The reaction is performed at elevated temperatures (130-150 °C) and works well for almost any hydrocarbon monomer. The reaction mixture probably forms a Schrock-type molybdenum carbyne intermediate as the active catalyst. Table 5 shows PAEs that have been prepared utilizing ADIMET with these in situ catalysts . Functional groups (with the exception of double bonds) are not well tolerated, but dialkyl PPEs are obtained with a high degree of polymerization. The progress in this field has been documented in several reviews (Table 1, entries 2-4). Recently, a second generation of ADIMET catalyst has been developed that allows... 

Fig. 3 shows the maximum extents of double bond conversion x, obtained at various light intensities for polymerizations of TEGDA at 20 and 80"C, respectively. The increase of ultimate conversion with light intensity is observed at both temperatures. This effect is not caused by self-heating of the polymerizing samples (9). 

The maximum extent of double bond conversion in TEGDA as measured with DSC increases not only with temperature but also with light intensity. Mechanical measurements show, however, that the intensity dependence vanishes when equal doses are applied. This means that at low intensities the polymerization continues for a considerable time at a rate which is imperceptible with DSC. 

The peak of double bonds disappears while intensity of the carbonyl group peak is independent of reaction time. Using this method, the conversion of double bonds vs. time was calculated to monitor polymerization of multiacrylate at two different temperatures (Figure 11.2). 

Dilatometric technique can also be used for determination of polymerization rate in the case of multimonomer polymerization. However, in this case calibration of the dilatometric method is more complex. The substrates and products are both polymers with similar molecular weights. Difference in density during the course of polymerization is connected only with the conversion of double bonds to the single bonds. It is difficult to obtain a macromolecular product in which double bonds are fully converted to single bonds. Calibration must be based on simultaneous measurements of Ah and independent method (e.g., IR spectroscopy) and calculation of (1/dp l/d]vi). 

Fig. 1. Simulated profile of conversion of double bonds in a multifunctional monomer vs polymerization time at different depths in the polymer (-, surface), (----, 1,4 mm), (---, 2.8 mm), and...

Fig. 6. The characteristic behavior of the propagation kinetic constant, kp, and the termination kinetic constant, k as a function of double bond conversion for a multifunctional monomer polymerization...

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