Polymerization of α-methyleneindane: A cyclic analog of α-methylstyrene

α-Methyleniedane (MI), a cyclic analog of α-methylstyrene which does not undergo radical homopolymerization under standard conditions, was synthesized and subjected to radical, cationic, and anionic polymerizations. MI undergoes radical polymerization with α,α′-azobis(isobutyronitrile) in contrast to α-methylstyrene, owing to its reduced steric hindrance, though the polymerization is slow even in bulk. Cationic and anionic polymerization of MI with BF₃OEt₂ and n-butyllithium, respectively, proceed rapidly. The thermal degradation behavior of the polymer depends on the polymerization conditions. The anionic and radical polymers are heteortactic-rich. Reactivity ratios in bulk radical copolymerization on MI (M₂) with methacrylate (MMA, M₁) were determined at 60°C (r₁ = 0.129 and r₂ = 1.07). In order to clarify the copolymerization mechanism, radical copolymerization of MI with MMA was investigated in bulk at temperatures ranging from 50 to 80°C. The Mayo–Lewis equation has been found to be inadequate to describe the result due to depolymerization of MI sequences above 70°C.     

Polymerization and copolymerization of α-methacrylophenone

Under a variety of conditions it has not been possible to induce the free-radical-initiated homopolymerization of α-methacrylophenone (α-MAP). The only product isolated from such efforts was the Diels-Alder dimer of the monomer. A Mayo-Lewis plot of the free-radical copolymerization of α-MAP and styrene shows considerable scatter but the copolymer composition indicates that an α-MAP unit can add to itself. These results have been ascribed to a penultimate effect. α-MAP is homopolymerized by dimsylsodium or n-butyllithium. Attempted copolymerization of α-map and styrene with n-butyllithium produces >95% α-MAP. Unexpectedly, α-MAP does not homopolymerize with lithium dispersion, but does react in the presence of styrene to give product containing a relatively small amount of α-MAP.     

Polymerization of α-halogenated p-xylenes with base

Various α-halo-p-xylenes have been polymerized with base yielding p-xylylene polymers. The reaction involves a 1,6-dehydrohalogenation to give a xylylene which then polymerizes. α,α′-Dichloro-p-xylene forms poly-α-chloro-p-xylylene and polymers containing stilbene units; α,α,α′,α′-tetrachloro-p-xylene gives poly-α,α,α′-trichloro-p-xylylene; alkyl, aryl, and halogen ring-substituted α-chloro-p-xylenes give the corresponding ring-substituted poly-p-xylylenes. The more halogens in the α positions (up to five), the weaker the base necessary for dehydrohalogenation. Sodium hydroxide in methanol will polymerize tetrachloro-p-xylene, while potassium tert-butoxide in refluxing p-xylene is necessary to polymerize α-chloro-p-xylenes. Stilbenes are formed when α-halo-p-xylenes are reacted with potassium tert-butoxide in polar solvents such as dimethyl sulfoxide.     

Polymerization of β-carbomethoxypropionaldehyde

High molecular weight crystalline poly(carbomethoxyethyl)oxymethylene was prepared from β-carbomethoxypropionaldehyde with the use of organometallic compounds. The characterization, fractionation, x-ray analysis, and viscosity measurement were carried out. Degradation by hydrochloric acid gave a highly crystalline but soluble polymer of a lower molecular weight. It was interesting to note the high solubility character of the polymer in organic solvents in contrast to the poor solubility of the isomeric poly(acetoxyethyl)oxymethylene. From the relationship among the intrinsic viscosity, Huggins' constant, and the solubility parameter of solvent, the solubility parameter of the polymer was determined to be 9.3 (cal/ml)^1/2.     

Polymerization of β-cyanopropionaldehyde

A new class of polyacetals, poly(cyanoethyl)oxymethylene, was obtained by the polymerization of β-cyanopropionaldehyde at ?78°C. with use of ionic initiators including boron trifluoride diethyl etherate, diethylzinc, triethylaluminum, and triethylaluminumtitanium tetrachloride complexes. The influence of temperature, initiator, and solvent upon the polymerization was studied. Infrared spectra of polymers obtained from different initiators are also illustrated. An attempt was made to fractionate the polymer by means of solvent extraction. The acetone-soluble polymer is an elastomeric material having a low solution viscosity. The acetone-insoluble, dimethylformamide-soluble polymer obtained as a white powder was found to have extremely high solution viscosity. Some amounts of insoluble fraction could be also separated. The latter two fractions were observed to have a reasonable stability.     

Polymerization of β-isovalerolactone

The polymerization of β,β′-dimethyl-β-propiolactone with various catalysts was investigated. A detailed study on the heterogeneous polymerization initiated by triethyl aluminum was carried out. A reaction mechanism is suggested on the basis of chemical analysis of the polymer.     

Polymerization photoinitiated by carbonyl compounds. IV. α-diketones and α-substituted alkanones

The photoinitiation efficiency of the free-radical polymerization of methyl methacrylate and styrene by several carbonly compounds has been determined. The compounds considered were α-substituted ketones and α-dicarbonyl compounds. For the ketones, the initiation efficiency employing methyl methacrylate depends on the α substitution; the values obtained change from less than 10^?3 (acetone) to 0.65 (3-hydroxy-3-methyl-2-butanone). All ketones are more efficient towards methyl methacrylate than styrene. This result can be explained in terms of triplet quenching by the last monomer. The results obtained employing α-dicarbonyl compounds do not conform to a simple pattern. In particular, benzil shows a considerably larger efficiency towards styrene than for methyl methacrylate. Since benzil is efficiently quenched by styrene, the initiation must involve the interaction of an excited benzil molecule and the monomer.     

Polymerization of α-methylstyrene by n-butyllithium in tetrahydrofuran

The kinetics of polymerization of α-methylstyrene by n-BuLi (labeled with C¹⁴ and unlabeled) has been studied in tetrahydrofuran at ?78°C. The catalyst n-BuLi was used as a complex of n-BuLi in THF and a hexane solution of n-BuLi. Contrary to expectations, the relative polymerization rate and the catalyst consumption were higher when a hexane solution of n-BuLi was used. Experimental molecular weights of the polymers greatly exceeded those calculated for the case of complete catalyst consumption. The polymers exhibited low polydispersity, and when a hexane solution of n-BuLi was used, the molecular weight distribution was bimodal. The rate of initiation for the case of polymerization α-methylstyrene with a hexane solution of n-BuLi as a catalyst was much higher than in the polymerization of α-methylstyrene with the use of the complex of n-BuLi in THF as in situ catalyst. Experimental data confirm the preferable interaction of α-methylstyrene with associated n-BuLi in the presence of THF. The complex which was formed as a result of such interaction is an active centers of polymerization.     

Polymerization of ethylene with nickel α-diimine catalysts

Several nickel α-diimine compounds of the general formula (ArNC(R) C(R)NAr)NiX₂ (Ar = 2,6-alkyl substituted Ph, R = H or CH₃, X = Br or CH³) were tested in ethylene polymerization after activation with different co-catalysts, such as methylaluminoxane, Al(C₂H₅)₂Cl or other aluminium alkyls, and ionizing reagents like B(C₆F₅)₃, [CPh₃][B(C₆F₅)₄] or HBF₄. The performances of the different catalytic systems were compared with reference to polymer productivity and structure. The degree of branching of the obtained polyethylenes was shown to depend not only on the ligand environment at the Ni centre but also on the type of co-catalyst.     

Polymerization of sterically congested α‐alkylacrylates under high pressure

A series of α‐alkylacrylates, including methyl ethacrylate (MEA), methyl α‐propylacrylate, methyl α‐isopropylacrylate (MiPA), methyl α‐butylacrylate (MnBA), and methyl α‐isobutylacrylate (MiBA), were successfully polymerized at 65 °C under high pressure (1–9 kbar). In contrast to results obtained at ambient pressure, all monomers yielded high molecular weight polymers (number‐average molecular weight = 4–18 × 10⁴), except for MiPA (number‐average molecular weight = 8 × 10³), probably because of the high steric hindrance of the isopropyl group. Polymerization kinetics under high pressure were obtained for MEA, MnBA, and MiBA. Overall activation volumes were estimated to be ?14.9, ?17.0, and ?11.6 mL mol^?1 for MEA (3–7 kbar), MnBA (3–7 kbar), and MiBA (5–9 kbar), respectively. Extrapolation to ambient pressure provided rates of polymerization for these monomers unaffected by the ceiling temperature effect. These values were further used to quantitatively assess the steric influence exerted by the α‐substituent on the polymerizability of these sterically congested acrylates with Meyer's steric parameter. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 836–843, 2002; DOI 10.1002/pola.10161     

Polymerization of α,α-disubstituted β-propiolactones and lactams. VII. Stereoregular polymers from optically active lactones

Optically active α-phenyl-ααethyl-β-propiolactone of high optical purity was prepared and polymerized by homogeneous anionic initiation to the isotactic polyester. The racemic and isotactic polymers had apparently different crystalline properties suggesting that the former may be syndiotactic or may crystallize with unit cells containing both R and S blocks. Similar attempts to prepare α-methyl-α-isopropyl-β-propiolactone of high optical purity were unsuccessful although a partially crystalline polymer was obtained from the racemic monomer.     

Polymerization behavior of 1,2,2,6,6-pentamethyl-4-piperidinyl m-isopropenyl-α,α-dimethylbenzyl carbamate

Copolymers of 1,2,2,6,6-pentamethyl-4-piperidinyl m-isopropenyl-α,α-dimethylbenzyl carbamate (CB) with styrene (S) and with methyl methacrylate (MMA) were synthesized using AIBN as initiator. S–CB copolymers made from feed ranging from 0.45–0.94 mole fractions S and MMA-CB copolymers made from feed of 0.34–0.88 mole fractions MMA were used to determine the monomer reactivity ratios r₁ and r₂. The structure of S–CB copolymers was inferred to be mainly of a random nature and in the MMA–CB copolymerization system there is a stronger tendency to form alternating copolymers. © 1993 John Wiley & Sons, Inc.     

Mechanism of Polymerization of α-Olefins on Oxide Catalysts

The polymerization of ethylene on a chromic oxide catalyst with and without a solvent has been studied. It was found that the active catalyst surface is formed exclusively as a result of its interaction with ethylene. This interaction is accompanied by the formation of products which poison the surface of the catalyst when they are sorbed on it in the absence of a solvent. A catalyst which contains no Cr⁺⁶ atoms as a result of reduction by alcohol is inactive. On the other hand, a catalyst which contains only Cr⁺⁶ atoms becomes active only after it has been partially reduced. The most probable product of this reduction is trivalent chromium atoms. The results obtained have given grounds for the assumption that the active complex contains Cr⁺⁶ and Cr⁺³ atoms. A possible mechanism of the reaction is discussed. Owing to the oxidative action of CrO₃ on the ethylene molecules, part of the Cr⁺⁶ is reduced to Cr⁺³, and the trivalent chromium becomes alkylated. The monomer molecule is added at the Cr⁺³—C bond thus formed. A strong Lewis acid, CrO₃, lowers the electron density on the Cr⁺³ atom. This increases the strength of the Cr⁺³—C bond and the ability of the Cr⁺³ atom to coordinate with the monomer molecule. The monomer molecule enters the chain at the moment when the strength of the Cr^?3—C bond is weakened due to coordination of this molecule with the Cr⁺³ atom.     

A novel synthesis of α-hydroxy- and α,α′-dihydroxyketone from α-iodo and α,α′-diiodo ketone using photoirradiation

A novel reaction of α-iodo ketone (α-iodocycloalkanone, α-iodo-β-alkoxy ester, and α-iodoacyclicketone) with irradiation under a high-pressure mercury lamp gave the corresponding α-hydroxyketone in good yields. In the case of α,α′-diiodo ketone, α,α′-dihydroxyketone which little has been reported until now was obtained. This reaction affords a new, clean and convenient synthetic method for α-hydroxy- and α,α′-dihydroxyketone.