Studies on stable free radicals. XVI. Copolymerizationo of a stable N-oxyl biradical with p-xylylene

Six copolymers were obtained by the reaction of a sterically hindered N-oxyl biradical with pseudodiradical p-xylylene using the reactivity of an N-oxyl toward the carbon radical. The feed ratio of the N-oxyl biradical to α-chloro-p-xylene, which was used as the precursor of the pseudodiradical p-xylylene, governed the properties of the copolymers produced. The copolymers with a terminalN-oxyl group, were obtained when a 0.4-1.2 molar ratio of the N-oxyl biradical to α-chloro-p-xylene. The polymerization process was also discussed.     

Copolymerization of styrene. V. Copolymerization with α-cyanocinnamamide

Copolymers of styrene with α-cyanocinnamamide were prepared by free radical initiation in bulk and in DMF solution and also by thermal initiation in bulk. The copolymerization parameters were determined by the conventional scheme of copolymerization and by an improved scheme taking into account the penultimate unit. Different values of the copolymerization parameters were obtained at the above mentioned different polymerization conditions, indicating the existence of a solvent effect. The influence of the comonomer on some of the basic properties, like intrinsic viscosity, solubility, melting range, and glass transition temperature and on some mechanical and behavior properties of the copolymers was studied in comparison with homopolystyrene.     

Copolymerization of acrylonitrile. III. Copolymerization with α-cyanocinnamamide

Acrylonitrile was copolymerized in solution with α-cyanocinnamamide up to low conversions. The conventional scheme of copolymerization fitted this copolymer. The basic properties, such as solubility, viscosity, and thermal behavior, of the copolymer prepared in bulk and in solution were determined.     

Isomerization of unsaturated radicals. V. Unimolecular isomerization of hot α,α- and α,β-dimethallyl radicals

The 147 nm photolysis of 3,3 dimethylbut-1-ene leads mainly to the formation of very hot (?375 kJ/mol) α,α-dimethallyl radicals. On the other hand, that of 3-methyl-cis-and trans-pentene-2, as well as that of 2,3-dimethylbut-1-ene is a source of very hot α,β-dimethallyl radicals. These allylic radicals are coolled down using pressure and are allowed to combine with available methyl radicals. From the formation of various C₆H₁₂ products, it is concluded that the very hot α,α- radical isomerizes towards the α,β-structure at low pressures and vice versa. The equilibrium constant of the following process has been evaluated to be 1.72 ± 0.30.      

Copolymerization of vinyl acetate with ethyl α-cyanocinnamate

Trisubstituted ethylene, ethyl α-cyanocinnamate, is readily copolymerized with vinyl acetate by a conventional radical initiator. Terminal, penultimate, and “complex” copolymerization models were applied by using the data of composition of the copolymers obtained in bulk and by copolymerization in benzene, ethyl acetate, and chloroform. The model based on the participation of the monomer complexes describes satisfactorily the deviation from the terminal copolymerization model. The proton NMR analyses of the monomer mixtures indicate that the interaction between the monomers leads to the formation of weak monomer complexes. Kinetic studies of the initial rate dependence on the total monomer concentration and monomer feed composition enabled us to evaluate the degree of participation of the free uncomplexed monomers and the monomer complex in the propagation reactions. The contribution of the complexed monomers in the propagation stages increases with the increase in total monomer concentration. The initial rate of the copolymerization is proportional to the square root of the initiator concentration, thus confirming the bimolecular termination of the macrochains. The rate constants of the addition reactions of the complex and free monomers were evaluated from the kinetic studies. The quantitative kinetic treatment provided information regarding the relative weight of the termination reaction and indicated that the termination in the system occurs predominantly by the cross-termination reaction between two growing polymer radicals with different kinds of monomer units at the ends. Additional information on the termination in this system was obtained from viscosity measurements.     

Free radicals in γ-irradiated poly-α-methylstyrene

Electron spin resonance (ESR) spectra were observed at ?160°C and at room temperature for γ-irradiated poly-α-methylstyrene. The spectrum observed at room temperature has been attributed to the radical species while that at ?160°C results from the same radical and superposition of the spectrum due to the radical ?H₂-C(CH₃)(C₆H₅)-. The radicals which are stable at room temperature could be used to graft vinyl acetate.     

Functional polymers. XLIX. Copolymerization of ω-alkenoates with α-olefins and ethylene

The 2,6-dimethylphenyl ester of 10-undecenoic acid was copolymerized with 1-dodecene, 1-octene, 1-hexene, propylene, and ethylene using coordination initiation systems based on “aluminum-activated” titanium trichloride and dialkylaluminum chlorides. The copolymerizations with higher α-olefins proceeded smoothly and gave copolymers incorporating from 60 to 90% of the 10-undecenoate feed. Copolymerization with propylene gave incorporation of 5 mol % of 2,6-dimethylphenyl 10-undecenoate; with ethylene only 3 mol % of the ω-alkenoate was readily incorporated. All copolymers were characterized by elemental analysis, dilute solution viscosity, and by their IR ¹H- and ¹³C-NMR spectra.     

Copolymerization with depropagation. V. Copolymerization of α-methylstyrene and methyl methacrylate between their ceiling temperatures

The variation of copolymer composition with monomer feed has been studied for the system α-methylstyrene-methyl methacrylate at 60, 114 and 147°C. The compositions predicted by the diad model of Part III of this series accurately describe the data.     

Radical copolymerization of acrylic monomers. VIII. Copolymerization of methyl methacrylate with methyl α-p-chlorobenzylacrylate and methyl methacrylate with methyl α-p-methoxybenzylacrylate

Free-radical copolymerization of methyl methacrylate with methyl α-p-chlorobenzylacrylate and methyl methacrylate with methyl α-p-methoxybenzylacrylate have been studied in benzene solution at 40°C. Although a simple copolymerization model fits the composition data, the kinetic behavior of both copolymerization systems are analyzed from simple and reversible copolymerization models, taking into account the relatively low ceiling temperature of both methyl α-(p-substituted benzyl)acrylates and considering that the overall rate of copolymerization drastically decreases with the increase of the corresponding methyl α-(p-substituted benzyl)acrylate molar fraction in the feed.     

Copolymerization of studies. Copolymerization of methyl α-cyanocrotonate with styrene,acrylonitrile, and vinyl acetate

Copolymers of methyl α-cyanocrotonate with styrene, acrylonitrile, and vinyl acetate were prepared in bulk by free radical initiation. The copolymerization parameters were determined for each pair by several methods. The basic properties, that is, intrinsic viscosity, solubility, melting range, and glass transition temperature of the obtained copolymers, were determined.     

Dimers from α-alkoxybenzyl radicals. An NMR study

meso and dl Dimers (ArCHOR)₂ where R is Me, Et, ⁱPr, ^tBu, cyclohexyl and 1-adamantyl may readily be differentiated by their NMR spectra; the benzylic protons of the meso isomer always absorb at a slightly higher field than those of the dl isomer in each of the solvents used. Differences in chemical shift are discussed in terms of preferences in conformer distribution. The formation of equal amounts of both dimers from the corresponding radical ArCHOR shows that steric and polar factors are not important in influencing the dimerization. Magnetic non-equivalence due to the presence of asymmetric centres was found in some of the compounds discussed above.     

Copolymerization of trioxane by γ-radiation

High molecular copolymers of trioxane with different cyclic ethers and formals were produced by γ-radiation from a ⁶⁰Co source. It was polymerized in the solid state at 53°C. Polymerization does not occur in the melt. Irradiation was carried out with exclusion of air at a dose rate of 7 × 10³ rad/hr. The polymerization rate was increased very considerably in the presence of 1,3-dioxolane and epichlorhydrin; the addition of other comonomers may reduce the yield. The concentration of the comonomer is generally higher in the polymer than in the initial mix. These comonomers which increase the polymerization rate are introduced preferentially into the polymer chain; this is proved by the unstable polymer part and the thermal stability. Experiments with the trioxane–1,3-dioxolane system revealed that the unstable polymer part is markedly reduced and the heat stability considerably inproved with rising concentrations of this monomer. The thermal stability and the reduced viscosity of these copolymers are within the range of technical processability.     

Copolymerization of β-butyrolactone and β-benzyl malolactone with aluminoxane catalysts

Poly (β-hydroxylbutyrate-co-benzyl β-malolactonate), (P-HB-co-BML) copolymers, were prepared by the ring-opening copolymerizations of β-butyrolactone (BL) and benzyl β-malolactone (BML) with several alkyl aluminoxane catalysts, including ethylaluminoxane (EAO), methylaluminoxane (MAO), and isobutylaluminoxane (IBAO). The copolymers had very broad molecular weight distributions with weight average molecular weights, M̄_w, greater than 200,000. The products were fractionated by solubility into acetone-soluble and insoluble copolymers. The former were random, atactic copolymers while the latter were stereoblock copolymers. Random, atactic copolyesters of these two monomers were also obtained with the diethylzinc-water, ZnEt₂-H₂O (0.6:1), and the (5,10,15,20-tetraphenylporphinato)aluminium chloride, TPPAlCl, catalysts. The copolymerization reactions with the latter two catalysts gave much higher yields (up to 98%) and better control of both the copolymer compositions and the molecular weight distributions, but these copolymers had M̄_w values of only 20,000 or less. The copolymer tacticities and comonomer sequences were determined by ¹³C NMR spectroscopy.     

Copolymerization of ethylene with higher linear α-olefins—reactivity ratios

Copolymerization of ethylene with mixtures of linear α-olefins C₆–C₃₆ in the presence of two heterogeneous Ziegler–Natta catalysts, δ-TiCl₃–AlEt₃ and TiCl₄/MgCl₂–AlEt₃, at 90°C was studied by the GC method, and reactivity ratios for all paris ethylene–α-olefin were estimated from the data on olefin consumption in the reactions. In the case of the δ-TiCl₃–AlEt₃ system, the r₂ value decreases from ca. 0.05 for 1-decene to ca. 0.02 for α-C₂₂H₄₄ and then remains approximately constant. This change is similar to the dependence of the modified steric parameter E_S^C of the olefin alkyl group on the size of the alkyl group. In the case of the supported TiCl₄/MgCl₂–AlEt₃ system a similar variation of r₂ with the length of the alkyl group were observed but the absolute values of r₂ were six to ten times lower than those for the first catalytic system.     

Polymerization of α-amino acid N-carboxy anhydride. IX. Copolymerization of α-amino acid N-carboxy anhydride in heterogeneous system

Copolymerization of NCA's was undertaken in a heterogeneous system in acetonitrile, which is not a solvent of the polypeptides. The reactivity ratio was calculated by using the Lewis-Mayo equation. Further, the conversion rate in the copolymerization and the configuration of the copolymer produced were compared with those of the copolymerization in the homogeneous system in nitrobenzene, in which the copolypeptides are swollen. The rate of copolymerization in acetonitrile was between the rates of polymerization of the individual monomers. It has been reported that the configuration of the copolymer obtained in dimethylformamide, in which the copolypeptides are swollen, is of the block type. On the other hand, many polypeptides obtained in acetonitrile, which is not a solvent of the copolypeptides, had a random configuration near to an alternating configuration.     

Studies of the γ ← α transition in syndiotactic polystyrene

In this work we compare calorimetric and X-ray diffraction experiments realized on annealed sPS in helical γ forms resulting by different treatements: From clathrate δ form and from interaction of amorphous sample with acetone. The experimental results show that the γ form obtained by acetone converts into the more ordered final α” form modification; while the γ form, obtained by thermal treatments of δ form, transforms into the poorly ordered final α' form.     

Copolymerization of vinyl cyclohexane and α-methyl vinyl cyclohexane with acrylonitrile

Copolymerization of vinyl cyclohexane and α-methyl vinyl cyclohexane with acrylonitrile in the presence of a complexing agent AlEtCl₂ results in the formation of alternate copolymers. In the copolymerization of vinyl cyclohexane with acrylonitrile the copolymer composition depends on the ratio of acrylonitrile to AlEtCl₂. If this ratio is unity, alternating copolymers of the composition 1:1 are formed; with a ratio greater than unity statistical copolymers that contain more than 50% acrylonitrile units are produced. The ¹H-NMR spectroscopy measurements indicate that the interaction between the comonomers and the complexing agent leads to the formation of ternary donor–acceptor complexes of equimolar composition. The equilibrium constants of these complexes at ?60°C have been determined. The effects of temperature, nature of solvent and dilution on the yield, and composition of the copolymers of vinyl cyclohexane with acrylonitrile formed have been studied. By lowering the temperature the yield of copolymers increases but their composition remains equimolar. An increase in the polarity of the medium results in an increase in copolymer yield, whereas the yield decreases if the reaction is conducted in a donor-solvent medium. Dilution of the reaction mixture disrupts the alternation of units in the macrochain of copolymers. The kinetic pecularities of copolymerization have been investigated. The linear dependence of the copolymerization rate on the product of comonomer concentration is observed. The rate of copolymerization is proportional to the square root of the incident light intensity. Various additions of radical type and irradiation accelerate the process of copolymerization. The mechanism of alternating copolymerization of vinyl cyclohexane monomers with acrylonitrile in the presence of AlEtCl₂ is discussed in terms of homopolymerization of the comonomer complex.