Other Carbonyl Monomers

A side reaction occurring with acetaldehyde and higher aldehydes containing a-hydro-gens is aldol condensation [Hashimoto et al., 1976, 1978 Yamamoto et al., 1978], Aldol reaction can be extensive at ambient temperatures and higher but is avoided by polymerization at low temperature. 

The effect of halogens on reactivity is also seen for fluorothiocarbonyl monomers. Thiocarbonyl fluoride is polymerized at —78°C by a trace of mild base such as dimethylforma-mide. The polymerization of hexafluorothioacetone is an extreme example of the effect of 

Thioacetone polymerizes adventitiously even at very low temperature, in contrast to the inability of acetone to polymerize. 

Carbonyl monomers can be polymerized by acidic initiators, although their reactivity is lower than in anionic polymerization. Protonic acids such as hydrochloric and acetic acids and Lewis acids of the metal halide type are effective in initiating the cationic polymerization of carbonyl monomers. The initiation and propagation steps in polymerizations initiated with protonic acids can be pictured as 

The termination reaction probably involves chain transfer with water or some other species present. 

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The chromatograph (Waters Associates) was fitted with PL Gel columns (Polymer Laboratories Ltd.) and two Infrared detectors in series. Chloroform was used as the eluant. Infrared detectors were used because the tin containing acrylic mommier has a characteristic carbonyl stretching frequency at 1620 cm which is well removed from that of other acrylic monomers which have, carbonyl absorptions at the more characteristic wavenumber 1720 cm . Both peaks obeyed the Beer Lambert law. A typical chromatogram showing the separation of residual monomers and polymer Is shown in Figure 1. 

Progress in the polymerization of the carbonyl linkage did not result until there was an understanding of the effect of ceiling temperature (Tc) on polymerization (Sec. 3-9c). With the major exception of formaldehyde and one or two other aldehydes, carbonyl monomers have low ceiling temperatures (Table 5-13). Most carbonyl monomers have ceiling temperatures at or appreciably below room temperature. The low Tc values for carbonyl polymerizations are due primarily to the AH factor. The entropy of polymerization of the carbonyl double bond in aldehydes is approximately the same as that for the alkene double bond. The enthalpy of polymerization for the carbonyl double bond, however, is appreciably lower. Thus AH for acetaldehyde polymerization is only about 29 kJ mol-1 compared to the usual 80-90 kJ mol-1 for polymerization of the carbon-carbon double bond (Table 3-14) [Hashimoto et al., 1076, 1978],... 

The copolymerization of carbonyl monomes with alkenes has been even less studied than that between different carbonhyl monomers. The radiation-initiated copolymerization of styrene with formaldehyde proceeds by a cationic mechanism with a trend toward ideal behavior, r = 52 and r2 = 0 at —78°C [Castille and Stannett, 1966]. Hexafluoroacetone undergoes radiation-initiated copolymerization with ethylene, propene, and other a-olefins [Watanabe et al., 1979]. Anionic copolymerizations of aldehydes with isocyanates have also been reported [Odian and Hiraoka, 1972]. 

Some cationic ring-opening polymerizations take place without termination and are reversible. Oxirane and oxetane polymerizations are seldom reversible, but polymerizations of larger-sized rings such as tetrahydrofuran are often reversible. The description of reversible ROP is presented below [Afshar-Taromi et al., 1978 Beste and Hall, 1964 Kobayashi et al., 1974 Szwarc, 1979]. It is also applicable to other reversible polymerizations such as those of alkene and carbonyl monomers. The propagation-depropagation equilibrium can be expressed by... 

Several other types of monomers are capable of yielding stereoisomeric polymer structures. Ordered structures are possible in the polymerization of carbonyl monomers (RCHO and RCOR ) and the ring-opening polymerizations of certain monomers. Thus, for example, the polymers from acetaldehyde and propylene oxide can have isotactic and syndiotactic structures as shown in Figs. 8-3 and 8-4. 

Coordination carbonylation polycondensation has been extended from the synthesis of polyamides [scheme (15)] and polyarylates [scheme (16)] to reactions using other nucleophilic monomers that, with dihaloarenes and carbon monoxide, yield poly(imide-amide)s, poly(acylhydrazide)s, and poly(benzoxa-zole)s [165,170,171],... 

However, even in the presence of vinyl monomers, an appreciable amoimt of the primary radical pair reacts in the cage giving rise to benzaldehyde and other carbonyl compounds [91,93,94] leading to coatings with acute characteristic smell (Scheme 21). 

U.v. irradiation of manganese or rhenium carbonyl in tetrafluoroethylene at — 93 °C results in rapid polymer formation, and the presence of tetrafluoroethylene in other vinyl monomers also allows initiation of polymerization by these carbonyls. Addition of photochemically generated Mn(CO)4 to CaF4 to give the o-bonded radical species (OC)4Mn CF2 CF2 is suggested. 

In the first step, a resin-bound secondary amine is acylated with bromoacetic acid, in the presence of N,N-diisopropylcarbodiimide. Acylation of secondary amines is difficult, especially when coupHng an amino acid with a bulky side chain. The sub-monomer method, on the other hand, is facilitated by the use of bromoacetic acid, which is a very reactive acylating agent Activated bromoacetic acid is bis-reactive, in that it acylates by reacting with a nucleophile at the carbonyl carbon, or it can alkylate by reacting with a nucleophile at the neighboring ah-phatic carbon. Because acylation is approximately 1000 times faster than alkylation, acylation is exclusively observed. 

Some transition metal ir-allyl compounds are not catalysts for polymerization. For example, Zr (allyl) 4 will not polymerize methyl methacrylate. Spectroscopic and other studies have shown that this allyl compound, unlike those of chromium, react with the carbonyl group of the monomer giving compounds of the type... 

At the first step, the insertion of MMA to the lanthanide-alkyl bond gave the enolate complex. The Michael addition of MMA to the enolate complex via the 8-membered transition state results in stereoselective C-C bond formation, giving a new chelating enolate complex with two MMA units one of them is enolate and the other is coordinated to Sm via its carbonyl group. The successive insertion of MMA afforded a syndiotactic polymer. The activity of the polymerization increased with an increase in the ionic radius of the metal (Sm > Y > Yb > Lu). Furthermore, these complexes become precursors for the block co-polymerization of ethylene with polar monomers such as MMA and lactones [215, 217]. 

The crystal structure of the 1 2 adduct 145 obtained by the reaction of [Cp SmH]2 with MMA was determined by X-ray analysis. One of the two monomer units is in the O-enolate form and the other unit coordinates to the samarium atom by the carbonyl group. A comparison between 145 and the... 

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