Kinetics of free-radical copolymerization of α-methylstyrene and styrene

The free-radical copolymerization of α-methylstyrene and styrene has been studied in toluene and dimethyl phthalate solutions at 60°C. Gas chromatography was used to monitor the rate of consumption of monomers. For styrene alone, the measured rate of polymerization R_p and M?_n of the polymer coincided with values expected from previous studies by other workers. Solution viscosity η affected R_p and M?_n of styrene homopolymers and copolymers as expected on the basis of an inverse proportionality between η^1/2 and termination rate. The rate of initiation by azobisisobutyronitrile appears to be independent of monomer feed composition in this system. Molecular weights of copolymers can be accounted for by considering combinative termination only. The effects of radical chain transfer are not significant. A theory is proposed in which the rate of termination of copolymer radicals is derived statistically from an ideal free-radical polymerization model. This simple theory accounts quantitatively for R_p and M?_n data reported here and for the results of other workers who have favored more complicated reaction models because of the apparent failure of simple copolymer reactivity ratios to predict polymer composition. This deficiency results from systematic losses of low molecular weight copolymer species in some analyses. Copolymer reactivity ratios derived with the assumption of a simple copolymer model and based on rates of monomer loss can be used to predict R_p values measured in other laboratories without necessity for consideration of depropagation or penultimate unit effects. The 60°C rate constants for propagation and termination in styrene homopolymerization were taken to be 176 and 2.7 × 10⁷ mole/l.-sec, respectively. The corresponding figures for α-methylstyrene are 26 and 8.1 × 10⁸ mole/l.-sec. These constants account for the sluggish copolymerization behavior of the latter monomer and the low molecular weights of its copolymers. The simple reaction scheme proposed here suggests that high molecular weight styrene–α-methylstyrene copolymers can be produced at reasonable rates at 60°C by emulsion polymerization. This is shown to be the case.     

Anionic copolymerization of α-methylstyrene and styrene: Kinetics and mechanism

A kinetic study of copolymerization of styrene and α-methylstyrene accompanied with depropagation, initiated by n-butyilithium in cyclohexane with tetrahydrofuran as an additive polar solvent, has been performed. The various propagation rate constants of active species and the complexation equilibrium constants between different kinds of active species were determined. Furthermore, the reactivity ratios of two monomers with regard to monomeric, monoetherated and dietherated active species were obtained.     

Alternating copolymerization of styrene and methyl α-chloroacrylate with diethylaluminum chloride

The alternating copolymerization of styrene and methyl α-chloroacrylate (MCA) with diethylaluminum chloride (Et₂AlCl) in benzene at 0°C has been investigated. The copolymer has an equimolar composition irrespective of the feed monomer composition, the copolymer yield and the amount of Et₂AlCl used. The copolymerization proceeds first very rapidly and then rather slowly after attaining a certain yield which varies proportionally to the amount of Et₂AlCl used. A maximum copolymer yield is observed at about 60% MCA feed composition. The ¹H-NMR analyses of dyad, triad, and pentad of the alternating deuterated α-d-St-MCA copolymer indicate that the configuration of this copolymer can be explained by a single parameter, coisotacticity σ(σ = 0.69). A favorable mechanism of the alternating propagation as well as of the stereoregularity control is discussed.     

Cationic copolymerization of β-pinene and epichlorohydrin

β-Pinene and epichlorohydrin (ECH) have been copolymerized cationically using BF₃(C₂H₅)₂O and SnCl₄ as catalysts. Polymerizations were carried out at ?80°C in methylenechloride. Monomer reactivity ratios were determined in both catalysts which were r₁(ECH) = 1.06 ± 0.15 and r₂ (β-pinene) = 0.32 ± 0.08 in BF₃(C₂H₅)₂O and r₁(ECH) = 0.33 ± 0.11 and r₂(β-pinene) = 2.03 ± 0.44 in SnCl₄. Copolymers of different composition were soluble in acetone and insoluble in methanol. This characteristic was taken to indicate that the polymeric products were real copolymers and not a mixture of two homopolymers of epichlorohydrin and β-pinene.     

Cationic polymerization of β-pinene,styrene and α-methylstyrene

Molecular weight distributions determined by gel permeation chromatography demonstrate that α-methylstyrene copolymerizes with both β-pinene and styrene, forming both bi- and terpolymers. The composition of precipitated polymer versus crude polymer, as determined by nuclear magnetic resonance, suggests that β-pinene and styrene also copolymerize. Extraction of the latter bipolymer of β-pinene and styrene with acetone gives only a small amount of insoluble β-pinene homopolymer, confirming that β-pinene and styrene copolymerize in m-xylene. GPC analysis shows that each copolymer contains some homopolymer. A comparison of M _n with molecular weight calculated from NMR analysis, assuming chain transfer to solvent, indicates that chain transfer is the predominant method of forming dead polymer. The carbonium ions of the growing chain tend to transfer to solvent with increasing ease in the order β-pinene, styrene, and α-methylstyrene.     

H NMR titration and quantum calculation for the inclusion complexes of styrene and α-methyl styrene with α, β and γ-cyclodextrins

The inclusion behavior between styrene (α-methyl styrene) and cyclodextrins (CDs) was studied by using ¹H NMR titration in solution. The results indicate that 1:1 inclusion complexes were formed. The association constants of the inclusion complexes were determined by nonlinear least-square method. The inclusion process was also studied by using PM3 quantum-mechanical semi-empirical method. The calculated results are in agreed with the experimental data.     

Ring-opening copolymerization of α-chloromethyl-α-methyl-β-propionolactone with ε-caprolactone

α-Chloromethyl-α-methyl-β-propionolactone (CMMPL) has been copolymerized with ε-caprolactone (CL) using a wide range of feed compositions and aluminium triisopropoxide [Al(OⁱPr)₃] as an initiator. Random copolymers of CMMPL with CL were obtained. The pendant chloromethyl groups of the copolymer were converted to quaternary ammonium salts by reaction with pyridine, resulting in an increased hydrophilicity of the copolymers.     

Controlled radical copolymerization of β‐pinene and acrylonitrile

The feasibility of the radical copolymerization of β‐pinene and acrylonitrile was clarified for the first time. The monomer reactivity ratios evaluated by the Fineman–Ross method were r_β‐pinene = 0 and r_{acrylonitrile} = 0.66 in dichloroethane at 60 °C with AIBN, which indicated that the copolymerization was a simple alternating copolymerization. The addition of the Lewis acid Et₂AlCl increased the copolymerization rate and enhanced the incorporation of β‐pinene. The first example for the synthesis of an almost perfectly alternating copolymer of β‐pinene and acrylonitrile was achieved in the presence of Et₂AlCl. Furthermore, the possible controlled copolymerization of β‐pinene and acrylonitrile was then attempted via the reversible addition–fragmentation transfer (RAFT) technique. At a low β‐pinene/acrylonitrile feed ratio of 10/90 or 25/75, the copolymerization with 2‐cyanopropyl‐2‐yl dithiobenzoate as the transfer agent displayed the typical features of living polymerization. However, the living character could be observed only within certain monomer conversions. At higher monomer conversions, the copolymerizations deviated from the living behavior, probably because of the competitive degradative chain transfer of β‐pinene. The β‐pinene/acrylonitrile copolymers with a high alternation degree and controlled molecular weight were also obtained by the combination of the RAFT agent cumyl dithiobenzoate and Lewis acid Et₂AlCl. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2376–2387, 2006     

Alternating copolymerization of β-methylstyrene and maleic anhydride

Alternating copolymers of β-methylstyrene and maleic anhydride were prepared by free-radical-initiated polymerization in bulk and in toluene as a solvent. The reactivity ratios k_1c/k₁₂ and k_2c/k₂₁ were calculated from the change of copolymerization rate with a monomer feed at a constant total monomer concentration according to the generalized model of Shirota and coworkers. From the equation R_p = R_p(f) + R_p(CT) were calculated R_p(f) and R_p(CT), and it was found that in toluene the copolymerization proceeds predominantly by the addition of CT-complex monomers. Termination occurs predominantly by homotermination of β-methyl-styrene macro free radicals, k_t22, but the cross termination k_t21 is also operative.     

Polymerization and copolymerization of β-butyrolactone and benzyl-β-malolactonate by aluminoxane catalysts

High molecular weight poly-β-hydroxybutyrate (PHB) and poly (β-hydroxybutyrate-co-β-benzyl malate) [P (HB? BM)], were prepared by ring-opening polymerization reactions of racemic β-butyrolactone (BL) and racemic β-benzyl malolactonate (BM) using two types of oligomeric aluminoxane catalysts prepared by the reaction of water with either triethyl-aluminum (EAO) or triisobutylaluminum (IBAO). The stereoregularities, crystallinities, and molecular weights were determined for both the PHB homopolymers and the P (HB? BM) copolymers by nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC). All homopolymers and copolymers obtained could be separated into acetone-soluble and acetone-insoluble fractions. In every case the latter had higher degrees of crystallinity, higher molecular weights and higher degrees of stereoregularity (84–87% isotactic dyads) than the former. Hence all of the polymers obtained from both types of catalysts apparently had stereoblock isotactic structures. Copolymer compositions and monomer dyad sequence distributions were determined by NMR spectroscopy.     

Soluble bimetallic μ-oxoalkoxides. IX. ε-caprolactone and β-propiolactone block copolymerization

The fast and living ring-opening polymerization of lactones by bimetallic μ-oxoalkoxides in homogeneous organic phase has led to successful block copolymerization. The catalyst is coordinatively associated in organic media; however, interaction with lactones can induce, following their nature, different rearrangements of the catalytic aggregates, depending on the nature of these lactones. Consequently, ε-caprolactone and β-propiolactone block copolymers are quantitatively obtained only in the presence of a completely dissociated catalyst.     

4‐Dimethyl­amino‐β‐nitro­styrene and 4‐dimethyl­amino‐β‐ethyl‐β‐nitro­styrene at 100 K

The structures of 4‐dimethyl­amino‐β‐nitro­styrene (DANS), C₁₀H₁₂N₂O₂, and 4‐dimethyl­amino‐β‐ethyl‐β‐nitro­styrene (DAENS), C₁₂H₁₆N₂O₂, have been solved at T = 100 K. The structure solution for DANS was complicated by the presence of a static disorder, characterized by a misorientation of 17% of the mol­ecules. The mol­ecule of DANS is almost planar, indicating significant conjugation, with a push–pull effect through the styrene skeleton extending up to the terminal substituents and enhancing the dipole moment. As a consequence of this conjugation, the hexa­gonal ring displays a quinoidal character; the lengths of the C—N [1.3595 (15) Å] and C—C [1.448 (2) Å] bonds adjacent to the benzene ring are shorter than single bonds. The mol­ecules are stacked in dimers with anti­parallel dipoles. In contrast, the mol­ecule of DAENS is not planar. The ethyl substituent pushes the nitro­propene group out of the benzene plane, with a torsion angle of −21.9 (3). Nevertheless, the mol­ecule remains conjugated, with a shortening of the same bonds as in DANS.     

Radical-initiated homo- and copolymerization of α-methylene-γ-butyrolactone

The kinetics of α-methylene-γ-butyrolactone (α-MBL) homopolymerization was investigated in N,N-dimethylformamide (DMF) with azobis(isobutyronitrile) as initiator. The rate of polymerization (R_p) was expresed by R_p = k[AIBN]^0.54[α-MBL]^1.1 and the overall activation energy was calculated as 76.1 kJ/mol. Kinetic constants for α-MBL polymerization were obtained as follows: k_p/k_t^1/2 = 0.161 L^1/2 mol^?1/2·s^?1/2; 2fk_d = 2.18 × 10^?5 s^?1. The relative reactivity ratios of α-MBL(M₂) copolymerization with styrene (r₁ = 0.14, r₂ = 0.87) were obtained. Applying the Q–e scheme led to Q = 2.2 and e = 0.65. These Q and e values for α-MBL are higher than those for MMA     

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.     

Copolymerization of β-pinene with styrene oxide and N-vinylpyrrolidone

The copolymerization of β-pinene with styrene oxide (SO) and β-pinene with N-vinylpyrrolidone (VP) was investigated by using SnCl₄ in dichloromethane diluent at low temperature. Monomer reactivity ratios were evaluated for both copolymers at ?80°C; these are r₁(SO) = 2.979 and r₂(β-pinene) = 0.002 and r₁(VP) = 0.096 and r₂(β-pinene) = 0.294.     

Thermal deesterification and decarboxylation of alternating copolymers of styrene with β-substituted t-butyl α-cyanoacrylates

Alternating copolymers of styrene with β-carboalkoxy-substituted t-butyl α-cyanoacrylates undergo facile deesterification at 150–190°C, about 60°C below the deprotection temperature of poly(t-butyl methacrylate), and decarboxylation at 170–200°C. When the β-substituent is a methyl ester, the two events are clearly separated, with the deesterification occurring at a maximum rate at 165°C and decarboxylation at 193°C. Anhydride formation is negligible in this case. The copolymer with t-butyl cyanofumarate exhibits simultaneous deesterification and decarboxylation events at 180°C with concomitant minor dehydration.