Post-copolymerization

In the theoretical treatment, an equal reactivity of functional groups belonging to the monomer and polymer is assumed. So, any reduction of the reactivity of pendant allyl groups of the prepolymer compared with the monomer may beeome one of the reasons for a greatly delayed actual gel point. The reaetivity of DAP prepolymer was evaluated kinetically from the post-copolymerization with ABz which has equivalent reaetivity to one allyl group of DAP monomer [62]. 

The kinetic treatment revealed that the reactivity of pendant allyl groups of the prepolymer is approximately equal to that of the monomer. The ratios ri = kii/kii and r2 = kn/kn have been estimated to be 1.0 and 0.9, respectively [67]. A similar result was also observed for the post-copolymerization of DAI prepolymer with ABz [68]. Now, we can conclude that the concept of equal reactivity of functional groups belonging to the monomer and polymer is valid for the radical polymerization of diallyl aromatic dicarboxylates at an early stage of polymerization, at least up to the theoretical gel point. However, in the case of the highly branched prepolymer formed at a late stage of polymerization, i.e. far beyond the theoretical gel point, the reactivity of pendant allyl groups may be reduced by steric hindrance. 

The significance of intramolecular crosslinking was clearly demonstrated in the post-polymerization of DAP prepolymer (Fig. 8) and its post-copolymerization with ABz (Fig. 7). This was also checked by SEC-LALLS the occurrence of... 

Trapped Radicals Induce Post-Copolymerization of Oxygen... 

The fiving nature of the copolymerization with 5-dMMAO, which showed the highest activity, was investigated by post-copolymerization. The results and the gel permeation chromatography (GPC) curves of the copolymers are shown in Fig. 11, implying that the copolymerization of norbomene and 1-octene with 5-dMMAO proceeds in a living manner. The molecular weight distribution in the... 

Fig. 11 Post-copolymerization of norbomene and 1-octene with 5-dMMAO...

In this paper, the pseudo-kinetic rate constant method in which the kinetic treatment of a multicomponent polymerization reduces to that of a hcmopolymerization is extensively applied for the statistical copolymerization of vinyl/divinyl monomers and applications to the pre- and post-gelation periods are illustrated. 

Alternatively a non-metallated chelating monomer such as (227) or (228) may be copolymerized with (223) and the metal introduced post-polymerization. Using this strategy nanoclusters of silver,615 gold,616 ZnS617 and CdS618 have been prepared. A related approach has recently been adopted with the ROMP of norbornenes functionalized with crown ether, (229),619 and triazacy-clononane, (230),620 substituents. 

Now the post-gelation period of the copolymerization of divinyl/vinyl monomers in the presence of a good solvent as a diluent will be considered. Let Qv(x) be the equilibrium volume swelling ratio of the gel formed at conversion x, and Q°(x) its degree of dilution in the reaction system, i.e.,... 

The monomer compositions were copolymerized using several different cure cycles. All of the cure cycles in this series included an additional post cure at 290 °C for one hour. The exact monomer compositions used, their detailed cure cycles and the physical properties of the resulting copolymers are shown in Table 16. As in the previous examples, here too the glass transition temperature went down as the fracture toughness increased. As before the fracture toughness rose as the mole ratio of bisbenzocyclobutene to bismaleimide approached unity. The presence of phenothiazine appeared to increase the fracture toughness in all of the examples although, its effect appeared most pronounced when... 

So far, theoretically, there have been two possible approaches for the synthesis of functional polyolefins, namely, (a) direct copolymerization of olefins with functional monomers using polymerization and catalyst technologies, and (b) post-polymerization reaction with polyolefins. 

The concept of PO macroinitiators centers on the introduction of an initiation moiety into an olefinic polymer chain for polymerization. The most effective route for preparing PO macroinitiators is by employing functional polyolefins containing hydroxyl groups or other reactive groups. These functional POs are prepared by copolymerization of olefins with functional monomers and post-polymerization reaction, as mentioned above. In the case where an initiation moiety was at the chain-end of the polyolefins, a block type copolymer is produced. It has been reported that thiol-terminated PP was used as polymeric chain transfer agent in styrene and styrene/acrylonitrile polymerization to form polypropylene-b/odc-polystyrene (PP-b-PS) and polypropylene-btock-poly(styrene-co-acrylonitrile) (PP-b-SAN) block copolymer [19]. On the other hand, polymer hybrids with block and graft structures can be produced if initiation moieties are in the polymer chain. 

Post-polymerization fimctionalization has been used to this end, but most research has been directed toward the copolymerization of ethylene with polar monomers. In this manner, inexpensive monomers can be used to create novel polymeric materials with a wide range of applications. The major drawback to this methodology is the inherent difference in reactivity between ethylene and other vinyl monomers during chain polymerization. This phenomenon is known to yield copolymers with low polar monomer incorporation and increased branch content arising from chain transfer events caused by side reactions with polar and/or protic functionaUties [45]. 

Polymerization of modified monomers makes the polymerization itself more challenging, as polymerization parameters known for common monomers, such as copolymerization reaction rates, do not necessarily apply to pre-modified monomers. Post-polymerization functionahzation methods, however, enable the use of functionahties as the side-chain modifiers to a well-defined polymer backbone so that a variety of functional polymers can be produced through one single polymer scaffold. A major challenge of this method is that the modification step must be a clean... 

Figure 24.9 Copolymerization of acrylic acid and glycidyl methacrylate with styrene to achieve post-polymerizer branching...

The radical III would be the most stable (kt k2). Post-polymerization and copolymerization of acrylamide- or acrylonitrile-enriched solutions show higher tendency to homopolymerize rather than to copolymerize. 

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