Polymerization, vinyl

Azobisnittiles are efficient sources of free radicals for vinyl polymerizations and chain reactions, eg, chlorinations (see Initiators). These compounds decompose in a variety of solvents at nearly first-order rates to give free radicals with no evidence of induced chain decomposition. They can be used in bulk, solution, and suspension polymerizations, and because no oxygenated residues are produced, they are suitable for use in pigmented or dyed systems that may be susceptible to oxidative degradation. 

Itaconic acid, anhydride, and mono- and diesters undergo vinyl polymerization. Rates of polymerization and intrinsic viscosities of the resulting homopolymers ate lower than those of the related acrylates (see Acrylic ester polymers) (8,9). 

Fig. 2. Main steps of reaction kinetics, where chain initiation is identical to other vinyl polymerizations.

Imidazolidin-2-one, 4,5-dihydroxy-4,4-di(p-bromophenyl)-reactions with urea, 5, 406 Imidazolidin-2-one, 1,3-divinyl-polymerization, 1, 280 I midazolidin-2-one, 1 -ethyl-3-vinyl-polymerization, 1, 279 Imidazolidin-2-one, 4-methylene-synthesis, 5, 140... 

Imidazolinium perchlorate, 4-hydroxy-2,5,5-trimethyl-4-phenyl-synthesis, S, 487 Imidazolinium salts antistatic agents, 1, 409 Imidazolinium salts, 1-vinyl-polymerization, 1, 280 Imidazolin-2-one, 1-cyano-synthesis, S, 482 Imidazolin-2-one, 4,5-dialkyl-synthesis, S, 491 Imidazolin-2-one, 4,5-diaryl-bromination, S, 399-400 lmidazolin-2-one, 4,5-di( p-bromophenyl)-reactions... 

Phthalides — see Benzo[c]furan-l (3H)-one Phthalimide, 2-amino-pyridazine synthesis from, 3, 53 Phthalimide, N-cyclohexylthio-as vulcanization accelerator, 1, 404 Phthalimide. methylidine-polymerization, 1, 273 Phthalimide, N-(trichloromethylthio)-biocide, 1, 399 Phthalimide, 1-vinyl-polymerization, 1, 273 Phthalimide, N-vinyl-copolymer... 

Pyrazole, 3,4,5-tris(trifluoromethyl)-synthesis, 5, 282 Pyrazole, vinyl-reactions, 5, 261 Pyrazole, 1-vinyl-polymerization, 1, 279... 

Pyrazole, N-vinyl-polymerization, 5, 269 3H-Pyrazole, 3,3,5-trimethyl-irradiation, 5, 251 Pyrazole carbaldehydes reactions, 5, 260 Pyrazole carbinols dehydration, 5, 261... 

Reaction Mechanism of Vinyl Polymerization with Amine in Redox and Photo-Induced Charge-Transfer Initiation Systems... 

Organic peroxide-aromatic tertiary amine system is a well-known organic redox system 1]. The typical examples are benzoyl peroxide(BPO)-N,N-dimethylani-line(DMA) and BPO-DMT(N,N-dimethyl-p-toluidine) systems. The binary initiation system has been used in vinyl polymerization in dental acrylic resins and composite resins [2] and in bone cement [3]. Many papers have reported the initiation reaction of these systems for several decades, but the initiation mechanism is still not unified and in controversy [4,5]. Another kind of organic redox system consists of organic hydroperoxide and an aromatic tertiary amine system such as cumene hydroperoxide(CHP)-DMT is used in anaerobic adhesives [6]. Much less attention has been paid to this redox system and its initiation mechanism. A water-soluble peroxide such as persulfate and amine systems have been used in industrial aqueous solution and emulsion polymerization [7-10], yet the initiation mechanism has not been proposed in detail until recently [5]. In order to clarify the structural effect of peroxides and amines including functional monomers containing an amino group, a polymerizable amine, on the redox-initiated polymerization of vinyl monomers and its initiation mechanism, a series of studies have been carried out in our laboratory. 

A substantial number of photo-induced charge transfer polymerizations have been known to proceed through N-vinylcarbazole (VCZ) as an electron-donor monomer, but much less attention was paid to the polymerization of acrylic monomer as an electron receptor in the presence of amine as donor. The photo-induced charge-transfer polymerization of electron-attracting monomers, such as methyl acrylate(MA) and acrylonitrile (AN), have been recently studied [4]. In this paper, some results of our research on the reaction mechanism of vinyl polymerization with amine in redox and photo-induced charge transfer initiation systems are reviewed. 

In our laboratory, Sun et al. [35] reported that the terahydrofuran hydroperoxide (THFHP)-DMT system could initiate vinyl polymerization actively with very low Ea as 35.2 kJ/mol for MMA and 34.3 kj/mol for AAM polymerization. 

Several articles [7,8] have reported that a persulfate-amine system, particularly persulfate-triethanol amine and persulfate-tetramethylethylenediamine (TMEDA) can be used as redox initiators in aqueous solution polymerization of vinyl monomers. Recently, we studied the effect of various amines on the AAM aqueous solution polymerization and found that not only tertiary amine but also secondary and even primary aliphatic amine and their polyamines can promote the vinyl polymerization as shown in Table 6 [40-42]. 

Reaction Mechanism of Vinyl Polymerization Table 6 Effects of Monoamines on AAM Polymerization - 233... 

Thus, an aminium radical from primary or secondary amine will at last form an amino radical instead of an aminomethyl radical. This amino radical will then serve as the only active radical species to initiate the vinyl polymerization. 

One of the first methods of polymerizing vinyl monomers was to expose the monomer to sunlight. In 1845, Blyth and Hoffman [7] obtained by this means a clear glassy polymeric product from styrene. Berthelot and Gaudechon [8] were the first to polymerize ethylene to a solid form and they used ultraviolet (UV) light for this purpose. The first demonstration of the chain reaction nature of photoinitiation of vinyl polymerization was done by Ostromislenski in 1912 [9]. He showed that the amount of poly(vinyl bromide) produced was considerably in excess of that produced for an ordinary chemical reaction. 

The photoinitiation of vinyl polymerization by organic compounds (carbonyl, azo, peroxide, disulphide compounds, etc.) or inorganic salts (e.g., metal halides and their ion pairs, etc.) will not be discussed here, since these type of photoinitiators are beyond the scope of the present chapter. 

Two types of organometallic photoinitiators for free radical vinyl polymerization are considered (1) transi-... 

Osmium carbonyl (Os3(CO)i2) acts as a photoinitiator of vinyl polymerization [20], which can function without a halide additive. The mechanism of photoinitiation is by a hydrogen abstraction from monomer to pho-... 

Aliwi and coworkers have investigated many vanadium (V) chelate complexes as photoinitiators for vinyl polymerization [36-43]. The mixed ligand complex of chloro-oxo-bis(2,4-pentanedione) vanadium (V). VO(a-cac)2 Cl is used as the photoinitiator of polymerization... 

When the polymer was prepared by the suspension polymerization technique, the product was crosslinked beads of unusually uniform size (see Fig. 16 for SEM picture of the beads) with hydrophobic surface characteristics. This shows that cardanyl acrylate/methacry-late can be used as comonomers-cum-cross-linking agents in vinyl polymerizations. This further gives rise to more opportunities to prepare polymer supports for synthesis particularly for experiments in solid-state peptide synthesis. Polymer supports based on activated acrylates have recently been reported to be useful in supported organic reactions, metal ion separation, etc. [198,199]. Copolymers are expected to give better performance and, hence, coplymers of CA and CM A with methyl methacrylate (MMA), styrene (St), and acrylonitrile (AN) were prepared and characterized [196,197]. 

Chain-transfer reactions take place during vinyl polymerization involving abstraction of an atom such as... 

Mn(III) is able to oxidize many organic substrates via the free radical mechanism [32], The free radical species, generated during oxidation smoothly initiate vinyl polymerization [33-35]. Mn(III) interacts also with polymeric substrates to form effective systems leading to the formation of free radicals. These radicals are able to initiate vinyl polymerization and, consequently, grafting in the presence of vinyl monomers. 

As in the case of ceric and vanadium ions, the reaction of organic compounds with Co(III) proceeds via formation of an intermediate complex. Such a complex decomposes and produces free radicals capable of initiating vinyl polymerization. However, only a few reports on Co(IIl) ion-initiated grafting onto cellulose fibers are available [38]. 

In aqueous solutions the persulphate ion is known as a strong oxidizing agent, either alone or with activators. Thus, it has been extensively used as the initiator of vinyl polymerization [43-47]. However, only later, Kulkarni et al. [48] reported the graft copolymerization of AN onto cellulose using the Na2S203/K2S20s redox system. 

This technique is based in the fact that when cellulose is oxidized by ceric salts such as ceric ammonium nitrate Ce(NH4)2(N03)6 free radicals capable of initiating vinyl polymerization are formed on the cellulose. However, the possibility remains that the radical formed is an oxygen radical or that the radical is formed on the C-2 or C-3 instead of the C-6 carbon atom. Another mechanism, proposed by Livshits and coworkers [13], involves the oxidation of the glycolic portion of the an-hydroglucose unit. Several workers [14,15], however, have found evidence for the formation of some homopolymer. In the ceric ion method free radicals are first generated and are then capable of initiating the grafting process [16-18]. 

As we have mentioned previously, 1,3-diketone and anilide were very effective reducing agents for vinyl polymerization initiated by ceric ion, respectively. Acetoacet-anilide (AAA), a compound having a 1,3-diketone and an anilide structure as well ... 

Can it promote vinyl polymerization initiated with Ce(IV) ion Dong et al. [37-39] for the first time reported that AAA and its derivatives such as o-acetoacetotolu-idine (AAT), o-acetoacetanisidide (AAN), and 2-benzoyl acetanilide (BAA) possess very high reactivity toward Ce(IV) ion in initiating the polymerization of vinyl monomer. The results are tabulated in Table 3. 

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