Homopolymerization allyl monomers

The free radical copolymerization of methyl methacrylate or acrylonitrile in the presence of zinc chloride with allylic compounds such as allyl alcohol, allyl acetate, and allyl chloride or butene isomers such as isobutylene, 1-butene, and 2-butene is characterized by the incorporation of greater amounts of comonomer than is noted in the absence of zinc chloride (35). Analogous to the radical homopolymerization of allylic monomers in the presence of zince chloride, the increase in the electron-accepting capability of the methyl methacrylate or acrylonitrile as a result of complexation results in the formation of a charge transfer complex which undergoes homopolymerization and/or copolymerization with a polar monomer-complexed polar monomer complex. 

The first of these is an example of induced decomposition of benzoyl peroxide (see Section 1.3.1). The second shows chain transfer to toluene, which is a solvent commonly used for solution polymerization. The last reaction is characteristic of allylic monomers and is prevalent to the extent that homopolymerizations of allylic monomers yield only chains with degrees of polymerization below about 20 (i.e. oligomeric chains). The high incidence of chain transfer to allylic monomers results from the high resonance stability of the allylic radical produced and the reaction is often referred to as autoinhibition. 

Negrell-Guirao et al. proposed the homopolymerization of nitrogen-and phosphorus-eontaining allyl monomers by a radical method in aqueous media. They demonstrated the possibility to produce phosphonated... 

Based on the differences in mechanisms of homopolymerization of dimethacrylate and diallyl ethers mentioned above, differences in the processes of gel-matrix formation based on them are quite understandable. It is also noted [72, 84, 85] that, depending on the nature of applied allyl monomers (for example, DAIP, DAP DAC, etc.), a microgel at higher degrees of transformation may be formed due to selection of conditions of homopolymerization performance (the presence of inhibitors, chain transmitters, etc.). Therewith, the proportion of soluble linear and branched products (zole-fraction) increases significantly. It was also found that the zole-fraction output up to high conversion degrees of these monomers is lower than of insoluble polymer. 

Sulfur dioxide does not homopolymerize but does participate in a rather wide variety of free radical copolymerizations with unsaturated monomers. The resulting polysulfones have been known for quite a long time. Solonina ( f ) obtained a white solid from the reaction of SO2 with allyl ethers in 1898, but such products were not recognized as copolymers until the work of Marvel and Staudinger in the 1930 s. 

The monomer addition scheme, shown at the top, requires an initiator which is capable of removing a hydrogen atom from the allylic position of the butadiene, resonance stabilization of the radical from AIBN does not permit this initiator to effect this reaction while benzoyl peroxide is capable of reaction to remove a hydrogen atom and initiate the reaction. On the other hand the polymeric radical addition scheme requires that homopolymerization of the monomer be initiated and this macroradical then attack the polymer and lead to the formation of the graft copolymer. Huang and Sundberg explain that the reactivity of the monomer... 

If one combines all of this information, one can develop a scheme to account for all of these observations. There is a competition for initiator in the reaction of SBS with methyl methacrylate some is used to initiate the homopolymerization of the monomer and some is used to remove an allylic hydrogen from the SBS chain. Once both of these sites are initiated, they will both compete for monomer. In the other three cases the initiator can once again initiate both the polymer and the monomer. For these monomers the reactivity of the... 

Ferulic acid, a phenolic acid that can be found in rapeseed cake, has been used in the synthesis of monomers for ADMET homo- and copolymerization with fatty acid-based a,co-dienes [139]. Homopolymerizations were performed in the presence of several ruthenium-based olefin metathesis catalysts (1 mol% and 80°C), although only C5, the Zhan catalyst, and catalyst M5i of the company Umicore were able to produce oligomers with Tgs around 7°C. The comonomers were prepared by epoxidation of methyl oleate and erucate followed by simultaneous ring opening and transesterification with allyl alcohol. Best results for the copolymerizations were obtained with the erucic acid-derived monomer, reaching a crystalline polymer (Tm — 24.9°C) with molecular weight over 13 kDa. 

The homopolymerization of aliphatic carbodiimides, using n-butyl lithium as catalyst in hydrocarbon solvents at room temperature, affords nylon-1 imides 199 (R=Me, n-Bu, allyl, Ph), which have no commercial interest because unzipping occurs on heating. In the unzipping process the monomer is regenerated. The polymerization failed with DDC, diisopropylcarbodiimide and methyl-t-butylcarbodiimide. 

Vinylsilane monomers do not homopolymerize owing to steric inhibition within a required catalytic intermediate, yet will specifically copolymerize with an unhindered diene, resulting in isolated units of the vinylsilane within the copolymer. Allylic silanes, however, show no resistance to homometathesis and yield novel high molecular weight, unsaturated polycarbosilanes with low glass transition temperatures and good thermal stability. 

One of the early theoretical studies of the polymerization of allyl acrylate considered the homopolymerization of this monomer to be an intramolecular copolymerization of the allyl and the acrylic double bonds. In this process it was calculated that only about 3% of the allyl groups participated in the process. Upon extended heating, the residual allyl groups served as cross-linking sites [69]. 

In an old patent, Friedman prepared homopolymers from cyclic phosphites and phosphonates with allyl functions (Scheme 3.12). These compounds were homopolymerized or copolymerized with other monomers such as styrene or acrylate monomers in the presence of conventional initiators or from UV activation. The polymers produced quite tough, hard, colorless and clear non-burning plastics. 

Allylic compounds (CH2MDHCH2X) are usually reluctant to undergo homopolymerization, because of the activation of the allylic hydrogen atom toward abstraction. The generated allylic radical is highly stabilized both by the substituent X and by delocalization of the free electrons into the double bond. These radicals add to monomer very slowly and perform side reactions that in turn lead to retardation. 

---