Monomers, vinyl homopolymerization

DiaUyl fumarate polymerizes much more rapidly than diaUyl maleate. Because of its moderate reactivity, DAM is favored as a cross-linking and branching agent with some vinyl-type monomers (1). Cyclization from homopolymerizations in different concentrations in benzene has been investigated (91). DiaUyl itaconate and several other polyfunctional aUyl—vinyl monomers are available. 

Homopolymerization of macroazoinimers and co-polymerization of macroinimers with a vinyl monomer yield crosslinked polyethyleneglycol or polyethyleneglycol-vinyl polymer-crosslinked block copolymer, respectively. The homopolymers and block copolymers having PEG units with molecular weights of 1000 and 1500 still showed crystallinity of the PEG units in the network structure [48] and the second heating thermograms of polymers having PEG-1000 and PEG-1500 units showed that the recrystallization rates were very fast (Fig. 3). 

Since Ce4+ salts are capable of causing the homopolymerization of vinyl monomers starting after a certain induction period, the grafting process is carried out during a time period shorter than the period of induction so as to synthesize graft PAN copolymers without any homopolymer being formed68). 

The most important example of an addition polymerization is the homopolymerization of a vinyl monomer. The general formula for a vinyl monomer is... 

Many vinyl monomers were reported to have been grafted onto fluoropolymers, such as (meth)acrylic acid and (meth)acrylates, acrylamide, acrylonitryl, styrene, 4-vinyl pyridine, N-vinyl pyrrolidone, and vinyl acetate. Many fluoropolymers have been used as supports, such as PTFE, copolymers of TFE with HFP, PFAVE, VDF and ethylene, PCTFE, PVDF, polyvinyl fluoride, copolymers ofVDF with HFP, vinyl fluoride and chlorotrifluoroethylene (CTFE). The source of irradiation has been primarily y-rays and electron beams. The grafting can be carried out under either direct irradiation or through the use of preliminary irradiated fluoropolymers. Ordinary radical inhibitors can be added to the reaction mixture to avoid homopolymerization of functional monomers. 

The hydroxyl radical may also initiate homopolymerization by adding to a vinyl monomer ... 

Direct Radiation Grafting of Polymer in the Presence of Vinyl Monomer. This leads to the formation of free radicals on both polymer and monomer, resulting in graft polymerization and homopolymerization. The extent of homopolymerization depends on the sensitivity of the monomer used. 

Of particular importance in describing the difference between these two families of resins are the locations of die reactive unsaturation. In the polyester resin, these groups are located along the backbone of die polymer with terminal hydroxyl or carboxylic acid groups. The vinyl ester resins contain no significant acidity but terminate in reactive vinyl ester groups. Because of the location of these reactive sites, the vinyl ester resins will homopolymerize as well as coreact with various vinyl monomers. 

We consider styrene homopolymerization by a free-radical mechanism. Styrene, like any other vinyl monomer, is bifunctional, because the double bond opens two arms in the polymerization processs (one of the carbons is attacked by a free radical, activating the other carbon atom, which may continue to propagate the chain). 

Copolymerization of vinyl chloride with metal salts of unsaturated carboxylic acids has been investigated more closely. By radical copolymerization in methanol solution of vinyl chloride and lead acrylate small amounts of lead acrylate can be inserted into the copolymer chains. However, only about one-third to one-half of the lead salt originally present in the monomer mixture is incorporated in the chains. Moreover, the thermal stability of the resulting polymer shows only a relatively small improvement over that of homopolymeric vinyl chloride (1) (see Figure 4). Although the rate of dehydrochlorination is distinctly lowered with increasing lead content in the polymers, there is no induction period at the onset of thermal treatment. Therefore, one cannot speak of true stabilization in this case. 

Homopolymerization of a vinylic monomer (styrene, methyl methacrylate) in the presence of polysulphide yields a block copolymer [39]... 

Methylenemalononitrile would seem to be the vinyl monomer most likely to form macrozwitterions in the presence of covalent bases. However, its homopolymerization has not been studied, presumably because of its extreme reactivity and the insolubility of the polymer. 

As a general rule, the controlling factor in reactivity of a vinyl monomer toward radical homopolymerization appears to be the stability of the radical formed by addition of the monomer to the initial radical. 

A large number of copolymers of cyclic ethers, cyclic sulphides and cyclic formals have been prepared. Many cyclic compounds that will not homopolymerize do copolymerize readily [7, 146,147]. Some cyclic compounds will copolymerize with lactones, cyclic anhydrides, or vinyl monomers. Very many commercially important materials have resulted from these copolymerizations. 

Via metal catalysis, cyclic monomers such as TV-substituted maleimides M-40, M-41, and M-42 do not homopolymerize but can copolymerize with vinyl monomers, among which alternating copolymers can be obtained with styrene via a radical mechanism. The 1-13 (X = Br)/CuBr/L-l system induced alternating copolymerizations with styrene to give controlled molecular weights and narrow MWDs (Mw/Mn =1.1 — 1.4) in the bulk or anisole at 80—110 °C.219-222... 

The composition of a copolymer produced by simultaneous polymerization of two monomers is usually different from the composition of the comonomer feed from which it is produced. This shows that different monomers have different tendencies to undergo copolymerization. These tendencies often have little or no resemblance to their behavior in homopolymerization. Some monomers are more reactive in copolymerization than indicated by their rates of homopolymerization, and some monomers are less reactive. Thus, vinyl acetate polymerizes about twenty times as fast as styrene in a free-radical reaction, but the product in free-radical polymerization of a mixture of vinyl acetate and styrene is found to be almost pure polystyrene with practically no content of vinyl acetate. By contrast, maleic anhydride, which has very little or no tendency to undergo homopolymerization with radical initiation, undergoes facile copolymerization with styrene forming one-to-one copolymers. 

C Chemical shift values also give information on the reactivity of vinyl monomers in homopolymerization by radical mechanism. In the radical polymerization of styrene and -substituted styrene a participation of the following ionic structure in the transition state of the propagation reaction was suggested 366... 

As can be seen from the last column of Table II, DSC studies did not indicate any change in the glass transition temperature of the polyacrylates due to the presence and/or concentration of the ionogenic monomer (SST) incorporated. We have observed the same behavior in styrene, methyl acrylate and other systems (26). Other workers have also reported similar results in ionomers synthesized by the direct reactions of various acrylic acid salts and covalent vinyl monomers (27). This indicates either the simultaneous homopolymerization of both monomers or a "block copolymerization. 

Mapolie and co-workers have reported the synthesis of polymers containing cyclopentadi-enylmetal complexes in their side chains.293,294 The polymers were prepared by homopolymerization of iron- or tungsten-containing vinyl monomers or copolymerization with styrene.293 Low molecular weight polyesters containing rhenium and iron complexes in their side-chains have also been prepared via polycondensations (Scheme 2.66).294 It was determined that by increasing the reaction time of the polymerization, the amount of insoluble material recovered increased. 

Results and Discussion. It is claimed in the patent literature that 1,3-dioxepins will copolymerize with a variety of vinyl monomers (4,29) and function well as chain transfer agents (29) in the polymerization of vinyl monomers. In view of these reports and prior to any copolymerization studies, we wished to know if any of the 4,7-dihydro-l,3-dioxepins prepared (Table I) would undergo free-radical initiated homopolymerization. Free-radical polymerization of IA-IE were not observed. Using IA, Yokoyama and Hall (10) confirmed these results. 

---