Spontaneous Copolymerizations

Styrene readily copolymerizes with many other monomers spontaneously. The styrene double bond is electronegative on account of the donating effect of the phenyl ring. Monomers that have electron-withdrawiag substituents, eg, acrylonitrile and maleic anhydride, tend to copolymerize most readily with styrene because their electropositive double bonds are attached to the electronegative styrene double bond. Spontaneous copolymerization experiments of many different monomer pair combiaations iadicate that the mechanism of initiation changes with the relative electronegativity difference between the monomer pairs (185). 

Thermal polymerization of the VCZ-AN system was studied by Ellinger and it was reported that the homopolymer of poly VCZ alone was obtained (28). Due to the small electron affinity of weak acceptors such as AN and methyl methacrylate (MMA), total charge transfer from VCZ to acceptor was thought impossible this induced Ellinger to propose a new polymerization mechanism assuming mesomeric polarization between VCZ and acceptor to initiate and control the propagating step. The finding that AN did not copolymerize with VCZ seemed to support his mechanism. Later, spontaneous copolymerization of VCZ with MMA was reported by the same author. 

Spontaneous copolymerization of cyclopentene (CPT) with sulfur dioxide (SOt) suggests the participation of a charge transfer complex in the initiation and propagation step of the copolymerization. The ESR spectrum together with chain transfer and kinetic studies showed the presence of long lived SOg radical. Terpolymerization with acrylonitrile (AN) was analyzed as a binary copolymerization between CPT-SOt complex and free AN, and the dilution effect proved this mechanism. Moderately high polymers showed enhanced thermal stability, corresponding to the increase of AN content in the terpolymer. 

As a development of our studies on charge transfer complexes and polymerization, we reported on the spontaneous copolymerization of cyclopentene and sulfur dioxide (11), and kinetic evidence for the participation of the charge transfer complex in the copolymerization was presented. This paper discusses the terpolymerization of cyclopentene, sulfur dioxide, and acrylonitrile to give further evidence for the charge transfer... 

Dilution with toluene slowed the copolymerization rate, and kinetic measurements were carried out in toluene at 0°-30°C. As reported previously (II), the over-all activation energy of the spontaneous copolymerization of CPT and S02 was calculated to be 16.5 kcal/mole from the Arrhenius plot of the initial rate vs. polymerization temperature. Dependence of the intial rate of copolymerization upon monomer concentration was checked at various monomer concentrations and found to be quite high (II) this could not be explained without participation of the monomer in the initiation step. 

A yellow color developed when CPT and S02 were mixed, and the equilibrium constant of the molecular complex formation was measured as K = 0.0353 ( 40°C, in hexane) (2). This complex might be the intermediate in this alternating copolymerization, and it might participate both in the initiation and propagation steps of this spontaneous copolymerization. 

Spontaneous thermal copolymerizations of captodative acrylates with styrene lead to a copolymer with higher molecular weight than the homopolymer. Copolymerization parameters are summarized in Table 17 [70], Both parameters r and r2 in the spontaneous copolymerizations are in agreement with those in the AIBN-initiated copolymerizations within experimental error, supporting a radical mechanism for the spontaneous copolymerizations. 

Spontaneous copolymerizations are encountered much more frequently, particularly when monomers of opposite polarity are mixed [9-10]. Early workers noticed that, upon mixing of certain electron-rich and electron-poor olefins, spontaneous polymerizations occurred without added initiator [99, 124 128]. Mixing electron-rich olefins with electron-poor olefins almost always results in brightly colored solutions. The colors are due to the CT excitation (hvCT) of the electron-donor-acceptor (EDA) complex [129], Theories for these spontaneous polymerizations mostly center around the charge-transfer complexes (CT or EDA complexes) [128]. 

A thorough study of the spontaneous copolymerization of p-methoxystyrene and dimethyl cyanofumarate was carried out [135] (Scheme 2). In this system the... 

The scope of the spontaneous copolymerization of P(III) monomers has been extended to copolymerizations with more sophisticated regulations of the arrangements of monomeric units in copolymers. They include a 2 1 sequence-ordered binary copolymerization of 43 with 46 (Eq. (27))30) and 1 1 1 sequence-ordered terpolymerizations of 54/acrylate 47jCQ2 (Eq. (28)) 39) and 48/49139 (Eq. (29))40 ... 

In contrast to QM, three monomers of TCK, HCX and CTCX have been found to undergo spontaneous copolymerization with various vinyl monomers such as styrene (St), isoprene, vinyl acetate, acrylonitrile, and methyl methacrylate 58 59,60). For the copolymerization systems of TCX-St, HCX-St, CTCX-St, (Fig. 5) CTCX-... 

Another case of essentially spontaneous copolymerization is the low temperature reaction of trifluoronitrosomethane with tetrafluoroethylene to give a mixture of cyclic adduct and polymer (7). 

Spontaneous copolymerization of the (isoprene-complexed acrylonitrile) complex with an (acrylonitrile-complexed acrylonitrile) complex ... 

Hasha DL, Priddy DB, Rudolf PR, Stark EJ, De Pooter M and Van Damme F (1992) Oligomer formation and the mechanism of initiation in the spontaneous copolymerization of styrene and acrylonitrile. Macromolecules 25 3046-51. 

Table II. Structure and relative abundance of cyclic oligomers formed in the spontaneous copolymerization of equimolar amounts of TBA and PL.

Spontaneous copolymerization of styrene and maleic anhydride in the presence of a molten polymer or a bulk polymer undergoing deformation at elevated temperatures is a rapid and convenient route for carboxylating polymers. The reaction is carried out on the bulk polymer at 120° to 200°C. (depending upon the softening or melting point of the polymer) by injecting an equimolar solution of maleic anhydride in styrene into the molten polymer (II, 12). 

Later Kagiya et al. described the zwitterionic spontaneous copolymerization of P-propiolactone with different aziridines69), and since 1972 Saegusa has started extensive studies of zwitterionic alternating copolymerization 70 79). In most of these systems the molecular weights of the copolymers are low. 

Table 15.7. Oligomers detected in the spontaneous copolymerization of 1-tert-butylaziri-dine (M,) and P-propiolactone (M2). [Mil, = [M2]o = 0.8 mol -l-1, CH3CN solvent, 50 °C 87)...

The ability of AAm complexes with Cr(III), Er(III) and other metal nitrates to involve other comonomers, such as acrylic or methacrylic acid and maleide anhydride, in spontaneous copolymerization in aqueous solutions has been reported [122]. It was possible to copolymerize transition metal nitrate AAm complexes with maleic acid under frontal conditions by thermal initiation [83]. 

There are many examples of spontaneous reactions. When, for instance, isobutylene is added to methyl a-cyanoacrylate, a spontaneous copolymerization in a 1 1 ratio takes place at room temperature. This was explained by the following scheme " ... 

Mechanism and Kinetics of the Induction Period in Nitroxide Mediated Thermal Autopolymerizations. Application to the Spontaneous Copolymerization of Styrene and Maleic Anhydride... 

This mechanism has been extended to the spontaneous copolymerizations of styrene with maleic anhydride and other electron-acceptor monomers (see Scheme 1, Several authors have studied the spontaneous polymerization of st5rene with acrylonitrile focusing on isolated trimers that are produced presumably as a result of the initiation step however, the trimer structures do not suffice to differentiate between the Mayo mechanism and the Flory diradical mechanism. 

In this communication we give preliminary results aimed at the elucidation of the mechanism and the estimation of the rate of radical generation in the spontaneous copolymerization of styrene and maleic anhydride. First, we show experiments that give order-of-magnitude estimates of the rate of radical generation in the copolymerization system, as compared with the homopolymerization of styrene. Second, we show additional results that give a preliminary estimation of the corresponding kinetic rate constant under some... 

A few spontaneous copolymerizations between exceptionally reactive donor acceptor olefinic pairs have been observed. Miller and Gilbert [37] observed that vinylidene cyanide spontaneously copolymerized with vinyl ethers when the two monomers were mixed at room temperature. Yang and Gaoni [38] observed that 2,4,6-trinitrostyrene as the acceptor monomer spontaneously copolymerized with 4-vinylpyridine as the donor monomer when the two were mixed at room temperature. Butler and Sharpe [39] reported that divinyl ether and divinyl sulfone spontaneously copolymerized upon monomer mixing. Thus, the participation of the charge-transfer complex in the copolymerization mechanism of such strong electron donor electron acceptor monomer pairs appears to have considerable support. 

Figure 15 Temperature dependence of the electrical resistance and the magnetic susceptibility of high-superconducting ceramics, (a) Ceramics from a copolymer ofY, Ba, and Cu acrylates, (b) Ceramics prepared by spontaneous copolymerization of acrylamide complexes of Bi, Ca, Sr, Pb, and Cu.

The resistance to hydrolysis of a polycyanoacrylate can also be improved by copolymerization with another monomer. In fact, the cyanopentadienoates cited above should also be considered comonomers. An electron-rich vinyl monomer like styrene and a cyanoacrylate ester will spontaneously copolymerize a short time after mixing. The product is a one-to-one alternating copolymer. This reaction has been used to make a two-part adhesive with better hydrolytic stability than the standard cyanoacrylate. " The carbon dioxide evolved from a suspension of the polymer in boiling water was measured to follow the degradation. After eight hours, polymethyl cyanoacrylate had lost 28% carbon dioxide by hydrolysis and decarboxylation of the polycyanoacrylate ester groups, while the copolymer had lost none. However, this improvement in moisture durability is achieved at the expense of the convenience of a one-part adhesive. 

---