Monomer Reactivity Ratios for the Copolymerization of Styrene with Pure Meta-and Pure Para-Divinylbenzenes

Reactivity ratios for the copolymerization of styrene (r ₁) meta-divinylben-zene (r ₂–m) and with para-divinylbenzene (r ₂–p) have been redetermined under different reaction conditions and with different radioactivity assay techniques. The copolymers were prepared at two conversion levels [0.55 to 3.7% and 2.7 to 7.5% and at 80° (rather than 100°)] with benzoyl peroxide (in place of τ-butylhydroperoxide) initiator. The ionization chamber-vibrating reed electrometer radioactivity assay technique developed for other copolymerization studies was used in place of the direct counting technique previously used for the styrene/divinylbenzene systems. The new values are r ₁ = 0.605/r ₂-m = 0.88: r ₁ = 0.77/r ₂-p = 2.08 at 0.55 to 3.7% conversion and r ₁ = 1.27; r ₂–m = 1.08 at 2.7 to 7.5% conversion. These are not in close agreement with previous values partly because of the difference in conditions of copolymerization (temperature, per cent conversion, initiator) and in the improved analytical precision. Also the high-DVB-content (80%) para copolymer data are not assumed to be invalid and are not omitted (as they were before) from selection of the r ₂–p values.     

Copolymerization of vinyl monomers with Gd(OCOCCl3)3-(i-Bu)3Al-Et2AlCl

The polymerization of polar monomers such as methyl methacrylate (MMA), methyl acrylate (MA), methacrylonitrile (MAN), and acrylonitrile (AN) was carried out with gadolinium-based Ziegler–Natta catalysts [Gd(OCOCCl₃)₃-(i-Bu)₃Al-Et₂AlCl] in hexane at 50°C under N₂ to elucidate the effect of the monomer's HOMO(highest occupied moleculor orbital) and LUMO (lowest unoccupied molecular orbital) levels on the polymerizability. In the case of homopolymerization, all monomers were found to polymerize and the order of relative polymerizability was as follows: MM > MA > MAN > AN. On the other hand, the result of copolymerization of St with MMA shows that the values of the monomer reactivity ratios are r₁ = 0.06 and r₂ = 1.98 for St(M₁)/MMA(M₂). The monomer reactivity ratios of styrene (St), p-methoxystyrene (PMOS), p-methylstyrene (PMS), and p-chlorostyrene (PCS) evaluated as r₁ = 0.55 and r₂ = 1.07 for St(M₁)/PMOS(M₂), r₁ = 0.38 and r₂ = 0.51 for St(M₁)/PMS(M₂), and r₁ = 0.72 and r₂ = 1.25 for St(M₁)/PCS(M₂) were compared with those for St(M₁)/MMA(M₂). The copolymerization behavior is apparently different from the titanium-based Ziegler—Natta catalyst, regarding a larger monomer reactivity ratio of PCS. The lower LUMO level of PCS and MMA may enhance a back-donation process from the metal catalyst, therefore resulting in high polymerizability. These results are discussed on the basis of the energy level of the gadolinium catalyst and the HOMO and LUMO levels of the monomers. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2591–2597, 1997     

Effect of substitution on the reactivity of some new p-phenylacrylamide derivatives with organotin monomers

Three new monomers of p-phenylacrylamide derivatives were prepared by either the reaction of p-methyl-, p-nitro-, and p-chloroaniline with acryloyl chloride or with acrylic acid in the presence of dicyclohexyl carbodiimide (DCCI). The prepared monomers were copolymerized with each of tri-n-butyltinacrylate and tri-n-butyltinmethacrylate. Copolymerization reactions were carried out in dioxane at 70°C using 1 mol % azobisisobutyronitrile as a free radical initiator. The structure of the new monomers and the prepared copolymers were investigated by IR and ¹H-NMR spectroscopy. The monomer reactivity ratios for the copolymerization of p-chlorophenylacrylamide (M₁) with each of tri-n-butyltinacrylate (TBTA) and tri-n-butyltinmethacrylate (TBTMA) (M₂) were found to be r₁ = 2.6; r₂ = 0.83 and r₁ = 1.3; r₂ = 1.71, respectively. In case of p-tolyacrylamide (M₁) with TBTA and TBTMA (M₂) r₁ = 0.35, r₂ = 1.03 and r₁ = 1.38, r₂ = 0.366 respectively. The Q and e values for the prepared p-tolyl- and p-chlorophenylacrylamide were calculated © 1993 John Wiley & Sons, Inc.     

Copolymerization of fluorinated acrylic monomers with p-vinylphenol and hydroxyethyl methacrylate

Copolymers of p-vinylphenol were prepared in bulk with heptafluorobutyl and pentadecafluorooctyl acrylates and trifluoroethyl, hexafluoroisopropyl, heptafluorobutyl, octafluoropentyl and pentadecafluorooctyl methacrylates using azobisisobutyronitrile as the initiator in sealed tubes. Intrinsic viscosities of the copolymers ranged from 0.44 to 1.85. Monomer reactivity ratios for copolymers of trifluoroethyl methacrylate (M₁) were: with hydroxyethyl methacrylate (M₂), r₁ = 0.47, r₂ = 1.0; with methyl methacrylate (M₂), r₁ = 0.82, r₂ = 0.50; with styrene (M₂), r₁ = 0.29, r₂, = 0.20; and with p-vinylphenol (M₂), r₁ = 0.096, r₂ = 1.5. Q and e values of trifluoroethyl methacrylate were 1.30 and 0.92, respectively. Monomer reactivity ratios of octafluoropentyl methacrylate (M₁) were: with styrene (M₂), r₁ = 0.26, r₂ = 0.20; and with p-vinylphenol, r₁ = 0.21, r₂ = 1.5. Q and e values for octafluoropentyl methacrylate were 1.27 and 0.92, respectively. Critical surface tensions of the homopolymers ranged from 17.9 to 14.8 dyn/cm. A copolymer of hexafluoro-i-propyl methacrylate and p-vinylphenol exhibited a critical surface tension of 16.5 dyn/cm.     

Copolymerization of vinylsilanes with styrene

New vinylsilanes (M₂), i. e. phenylvinylsilane (I), allylmethylsilane (II), allylphenylsilane (III), and p-vinylphenylmethylsilane (IV), were prepared and copolymerized with styrene (M₁). The monomer reactivity ratios were r₁ = 5.7 and r₂ = 0, r₁ = 36 and r₂ = 0, r₁ = 29 and r₂ = 0₁, and r₁ = 0.91 and r₂ = 1.1, respectively. From the results of infrared and NMR spectra it was indicated that the vinylsilanes participated in copolymerization in the form of a vinyl type of polymerization and not in the form of a hydrogen-transfer type of polymerization. The reaction of copolymer with alcohols and methyl methacrylate and appropriate catalysts was investigated.     

Anionic copolymerization of isocyanates with ketenes

Diphenyl-, phenylethyl, and phenylmethylketene have been copolymerized with phenyl isocyanate by use of sodium naphthalene in dimethylformamide (DMF) at ?45°C. Reactivity ratios of phenyl isocyanate (r₂) with diphenylketene (r₁) were r₁ = 0.10, r₂ = 0.29; with phenylethylketene (r₁) were r₁ = 1.6, r₂ = 0.10; and with phenyl methyl ketene (r₁) were r₁ = 4.8, r₂ = 0.02. The same initiator and solvent system were used for homopolymerization of phenylethylketene and copolymerization with m-chloro-, p-chloro-, p-methoxy-, and m-methoxyphenyl isocyanate as well as with phenyl isocyanate. Molecular weights ranged from 1740 to 4000. The effect of substituents on the order of isocyanate incorporation into the copolymer was m-Cl = p-Cl > m-MeO > H > p-MeO. Phenylethylketene was also copolymerized with m-methoxyphenyl, p-methoxyphenyl, and p-tolyl isocyanate in tetrahydrofuran (THF) at ?78°C. Molecular weights ranged from 2800 to 10,500. The least reactive isocyanate was incorporated into the copolymer to a greater extent in this solvent than in the more polar DMF. DTA showed the presence of crystallinity only in polymers of high isocyanate content. The ketenes copolymerized less readily with alkyl isocyanates, such as ethyl, n-butyl, n-hexyl, and cyclohexyl isocyanate, than with the aromatic isocyanates when sodium naphthalene was used in either DMF or THF.     

Radical-initiated homo- and copolymerization of cyanomethyl methacrylate

The kinetics of cyanomethyl methacrylate (CyMA) homopolymerization was investigated in acetonitrile with azobisisobutyronitrile as initiator. The rate of polymerization R_p was expressed by R_p = k[AIBN]^0.49[CyMA]^1.2 and the overall activation energy was calculated as 72.3 kJ/mol. Kinetic constants for CyMA polymerization were obtained as follows: k_p/k = 0.10 L^1/2s^?1/2; 2fk_d = 1.57 × 10^?5s^?. The relative reactivity ratios of CyMA(M₂) copolymerization with styrene (r₁ = 0.15, r₂ = 0.29) and methyl methacrylate (r₁ = 0.43, r₂ = 0.75) in acetonitrile were obtained. Applying the Q-e scheme (in styrene copolymerization) led to Q = 1.64 and e = 0.98. The glass transition temperature T_g of poly(CyMA) was observed to be 91°C by thermomechanical analysis. Thermogravimetry of poly(CyMA) showed a 10% weight loss at 265°C in air.     

Monomer-isomerization polymerization. XVIII. Monomer-isomerization copolymerizations of 4-phenyl-2-butene with 4-methyl-2-pentene and 3-heptene with Ziegler-Natta catalyst

4-Phenyl-2-butene (4Ph2B) undergoes monomer-isomerization copolymerization with 4-methyl-2-pentene (4M2P) and 2-and 3-heptene (2H and 3H) with TiCl₃–(C₂H₅)₃Al catalyst at 80°C to produce copolymer consisting exclusively of 1-olefin units. For comparison the copolymerization of 4-phenyl-1-butene (4Ph1B) with 4-methyl-1-pentene (4M1P) and 1-heptene (1H) was carried out under similar conditions. The composition of the copolymers obtained from these copolymerizations was determined from the ratios of optical densities D₁₃₈₀ and D₁₆₀₀ of infrared (IR) spectra of their thin films. The apparent monomer reactivity ratios for the monomer-isomerization copolymerization of 4Ph2B with 4M2P, 2H, and 3H in which the concentration of olefin monomer in the feed was used as internal olefin and those for the copolymerization of 4Ph1B with 4M1P and 1H were determined as follows: 4Ph2B(M₁)-4M2P(M₂); r₁ = 0.90, r₂ = 0.20, 4Ph1B(M₁)-4M1P (M₂); r₁ = 0.40, r₂ = 0.70, 4Ph2B(M₁)-2H(M₂); r₁, = 0.45, r₂ = 1.85, 4Ph2B(M₁)-3H(M₂); r₁ = 0.50, r₂ = 1.20, 4Ph1B(M₁)-1H(M₂); r₁ = 0.55, r₂ = 0.75. The difference in monomer reactivity ratios seemed to originate from the rate of isomerization from 2- or 3-olefins to 1-oletins in these monomer-isomerization copolymerizations.     

Synthesis and polymerization of N-[4-N′- (α-methylbenzyl)aminocarbonylphenyl]maleimide

A novel type of optically active N-[4-N′-(α-methylbenzyl)aminocarbonylphenyl]maleimide [(R)-MBCP] was synthesized from maleic anhydride, p-aminobenzoic acid, and (R)-methylbenzylamine. Radical homopolymerization of (R)-MBCP was performed in tetrahydrofuran (THF) at 50 and 70°C for 24 h to give optically active polymers having [α]²⁵_D = -141° and -129°, respectively. Anionic polymerization of (R)-MBCP with n-butyllithium in THF and N,N-dimethylformamide gave an optically active polymer having ?78 to ?81° of [α]²⁵_D. Radical copolymerizations of (R)-MBCP (M₁) were performed with styrene (ST, M₂) and methyl methacrylate (MMA, M₂) in THF at 50°C. The monomer reactivity ratios (r₁, r₂) and the Alfrey-Price Q-e values were determined as follows: r₁ = 0.009, r₂ = 0.091, Q₁ = 1.30, e₁ = 1.87 in the (R)-MBCP-ST; r₁ = 0.27, r₂ = 1.21, Q₁ = 0.93, e₁ = 1.46 in the (R)-MBCP-MMA system. Chiroptical properties of the polymers were also investigated. © 1992 John Wiley & Sons, Inc.     

The Laplacian of the electronic density at the valence-shell charge concentration (VSCC): A comparative study of effective core potential and full-electron calculations in Mo compounds. II

The effective core potential (ECP), using a basis set of different qualities, and ab initio full-electron (FE) calculations were carried out for MoS⁻²₄, MoO⁻²₄, and MoOCl₄ molecules. The topology of − ▿²p(r_cp) (the negative Laplacian of the charge density at its critical points) in the atomic valence shell was studied. Results clearly indicate that semicore (ECP2) approaches are able to reproduce, in a qualitative way, the topology of the Laplacian distribution with respect to those obtained by the FE method. Modifications of basis sets, such as introduction of polarization functions on the ligands, affect the electronic charge distribution (number of critical points in MoOCl₄) for FE as well as for ECP2 approaches. The ECP2 scheme predicts correctly the order of − ▿²p_x(r_cp) (X = O, S, Cl, Mo) in the valence shell; nevertheless, it fails in the relative magnitudes of − ▿²p_Mo(r_cp) between Mo compounds in respect to FE calculations. A scaling factor consistently improves the values of − ▿²p(r_cp) and p(r_cp), which are larger than those obtained with FE, particularly the − ▿²p(r_c) values. © 1996 John Wiley & Sons, Inc.     

Polymerization behaviour of 2,5-dimethylene- 2,5-dihydrofuran

Spontaneous homopolymerization of 2,5-dimethylene-2,5-dihydrofuran (DDF) was studied. The polymerization rates in two different initial monomer concentrations of DDF were analyzed with the first-order and second-order kinetics, and the homopolymerization of DDF was found to obey the first-order kinetics. The Arrhenius plot of the apparent rate constants at 30, 40, 50, and 60° gave an overall activation energy of 68.0 kJ/mol for the polymerization of DDF. From the comparison of the apparent rate constants at –78° and the time (the so-called half-life time) to decrease in half the monomer concentration for DDF with the corresponding values for p-xylylene (QM), DDF was found to be a less reactive monomer than QM. The copolymerizations of DDF with vinyl monomers such as acrylonitrile (AN), α-chloroacrylonitrile (CIAN), diethyl fumarate (DEF), and fumaronitrile (FN) were carried out in chloroform at 50° in the presence of AIBN to obtain the monomer reactivity ratios r₁(DDF) = 30.0 ± 3.0 and r₂ (AN) = 0 for the DDF-AN system, r₁ (DDF) = 1.55 ± 0.2 and r₂(CIAN) = 0 for the DDF-CIAN system, r₁(DDF) = 3.88 ± 0.2 and r₂(DEF) = 0 for the DDF-DEF system, and r₁(DDF) = 2.41 ± 0.1 and r₂ (FN) = 0 for the DDF-FN system, respectively. As the monomer reactivity ratios of r₂ for all systems were zero, Q and e values of DDF were calculated from the combination of two r₁ (DDF) values of any two copolymerization systems to be the 7.64 to 6.63 ×10²¹ range for Q and the –0.70 to –6.31 range for e, indicating that DDF is a highly conjugative and electron-donating monomer. © 1995 John Wiley & Sons, Inc.     

Copolymerization of 1,6-anhydroglucose and 1,6-anhydromaltose derivatives

The copolymerization of 1,6-anhydro-2,3,4-tri-O-(p-methyl-benzyl)-β-D -glucopyrnose [TXGL, M₁] with 1,6-anhydro-2,3-di-O-benzyl-4-O-(2,3,4,6-tetra-O-benzyl-α-D -glucopyranosyl)-β-D -glucopyranose [HBMA, M₂] has been studied as a method of producing dextrans of controlled composition with a linear backbone and randomly distributed single glucose units as side chains. Copolymers of intrinsic viscosities ranging from 0.51 to 0.05 dl/g are produced. The copolymerization appears to follow classical copolymerization theory but is affected adversely by the low reactivity of the maltose derivative. Reactivity ratios have been calculated for runs catalyzed by 10 mole-% and 20 mole-% phosphorus pentafluoride (PF₅): r₁ = 1.91 ± 0.35, r₂ = 0.28 ± 0.25 and r₁ = 2.21 ± 0.15, r₂ = 0.21 ± 0.10, respectively.     

Vinylhydroquinone. III. Copolymerization of vinylhydroquinone and vinyl monomers by tri-n-butylborane

The copolymerization of vinylhydroquinone (VHQ) and vinyl monomers, e.g., methyl methacrylate (MMA), 4-vinyl-pyridine (4VP), acrylamide (AA), and vinyl acetate (VAc), by tri-n-butylborane (TBB) was investigated in cyclohexanone at 30°C under nitrogen. VHQ is assumed to copolymerize with MMA, 4VP, and AA by vinyl polymerization. The following monomer reactivity ratios were obtained (VHQ = M₂): for MMA/VHQ/TBB, r₁ = 0.62, r₂ = 0.17; for 4VP/VHQ/TBB, r₁ = 0.57, r₂ = 0.05; for AA/VHQ/TBB, r₁ = 0.35, r₂ = 0.08. The Q and e values of VHQ were estimated on the basis of these reactivity ratios as Q = 1.4 and e = ?;1.1, which are similar to those of styrene. This suggests that VHQ behaves like styrene rather than as an inhibitor in the TBB-initiated copolymerization. No homopolymerization was observed either under nitrogen or in the presence of oxygen. The reaction mechanism is discussed.     

Copolymerization of 4-cyclopentene-1,3-dione with p-chlorostyrene and vinylidene chloride

The copolymerization of 4-cyclopentene-1,3-dione (M₂) with p-chlorostyrene and vinylidene chloride is reported. The copolymers were prepared in sealed tubes under nitrogen with azobisisobutyronitrile initiator. Infrared absorption bands at 1580 cm.^?1 revealed the presence of a highly enolic β-diketone and indicated that copolymerization had occurred. The copolymer compositions were determined from the chlorine analyses and the reactivity ratios were evaluated. The copolymerization with p-chlorostyrene (M₁) was highly alternating and provided the reactivity ratios r₁ = 0.32 ± 0.06, r₂ = 0.02 ± 0.01. Copolymerization with vinylidene chloride (M₁) afforded the reactivity ratios r₁ = 2.4 ± 0.6, r₂ = 0.15 ± 0.05. The Q and e values for the dione (Q = 0.13, e = 1.37), as evaluated from the results of the vinylidene chloride case, agree closely with the previously reported results of copolymerization with methyl methacrylate and acrylonitrile and confirm the general low reactivity of 4-cyclopentene-1,3-dione in nonalternating systems.     

Esterolytic activity of imidazole-containing polymers. Synthesis and characterization of copoly[1-alkyl-4- or 5-vinylimidazole/4(5)-vinylimidazole] and its catalytic activity in the hydrolysis of p-nitrophenyl acetate

The water-soluble monomers, 1-methyl-4-vinylimidazole, 1-methyl-5-vinylimidazole, 1-ethyl-5-vinylimidazole, and 1-propyl-5-vinylimidazole have been synthesized, polymerized, and copolymerized with 4(5)-vinylimidazole. The copolymers were characterized by ¹⁴C-labeling, NMR, pK_a determination and viscosity measurements. The monomer reactivity ratios determined by ¹⁴C counting are r₁ = 1.04; r₂ = 0.94 [M₁ = 4(5)-vinylimidazole, M₂ = 1-methyl-4-vinylimidazole] and r₁ = 1.01; r₂ = 0.86 [M₁ = 4(5)-vinylimidazole, M₂ = 1-methyl-5-vinylimidazole]. The esterolytic activity of the copolymers for the hydrolysis of p-nitrophenyl acetate (PNPA) at pH 7–8 in 28.5% ethanol–water was higher than that of the mixtures of homopolymers. At pH 5–6 the esterolytic activities of the copolymers and the mixtures were similar. The most efficient esterolytic activity for PNPA hydrolysis at pH 7.11 in 28.5% ethanol–water occurred for copolymers containing 75 mole % 4(5)-vinylimidazole and for copolymers containing 1-methyl-4-vinylimidazole rather than 1-methyl-5-vinylimidazole.     

Carbon-13 NMR spectra of a series of para-substituted phenyl isothiocyanates. Linear free energy relationships for carbon-13 substituent chemical shifts

Carbon-13 chemical shifts are reported for 16 para-substituted phenyl isothiocyanates measured at 1 and 10 mol % in chloroform-d solution. Data for the ? N?C?S group were not obtained at 1 mol %, but concentration effects for the other resonances were negligible. Hammett, dual substituent parameter (DSP) and DSP-nonlinear resonance (DSP-NLR) analyses were used to evaluate substituent effects on the substituent chemical shifts (SCS) for the ipso-carbon (C-1), C-2, and the ? N?C?S carbon atoms. A good Hammett correlation was observed for C-1 (ν_p⁺ = 8.1 ppm, r = 0.98 at 1 mol %) but was improved for the higher order correlations with the following results, DSP:ρ _I = 5.4, ρ_R° = 22.2, r = 0.998; DSP-NLR: ρ_I = 5.6, ρ_R° = 20.5, ? = ?0.22, r = 0.999. The 10 mol % data were very similar except the value of ? was ?0.26 and confirms the phenyl-bonded ? N?C?S moiety as a mild electron acceptor substituent. Hammett correlations were unsuccessful for the C-2 data, but fairly good results were obtained from the higher order analyses. For the 1 mol % data, DSP: ν_I = 1.6, ν_R° = ?2.0, r = 0.976; DSP-NLR: ν_I = 1.8, ν_R° = ?2.6, ? = 1.1, r = 0.982. Excellent correlations were obtained for the 10 mol % ? N?C?S carbon data. Hammett: ν_p° = 6.2, r = 0.997; DSP: ν_I = 5.9, ν_R° = 7.0, r = 0.997; DSP-NLR: ν_I = 5.8, ν_R° = 7.6, ? = 0.25, r = 0.997. The positive ν values in these three correlations contrast the negative values usually observed for carbonyl and thiocarbonyl carbons, and more closely parallel results previously reported for the β-carbon of styrenes and benzylidene anilines with para-substituents in the aniline ring.     

Ferrocene-containing polymers. II. Radiation-induced copolymerizations of ferrocenylmethyl methacrylate with styrene,methyl methacrylate,and ethyl acrylate

Ferrocenylmethyl methacrylate (FMMA) was copolymerized with styrene (St), methyl methacrylate (MMA), and ethyl acrylate (EA) in benzene solution at 25°C by γ radiation. The reactions proceeded by a free radical mechanism, and monomer reactivity ratios were derived by the Tidwell–Mortimer method for St(M₁)–FMMA(M₂), r₁ = 0.35 and r₂ = 0.46; for MMA(M₁–FMMA)(M₂), r₁ = 0.85 and r₂ = 1.36; for EA(M₁)–FMMA(M₂), r₁ = 0.36 and r₂ = 3.03. The Q and e values of FMMA determined from copolymerization with St were 0.97 and 0.55, respectively. Terpolymerization of a MMA–FMMA–EA system based on the Alfrey–Goldfinger equations was studied. This is a typical terpolymerization system in which reactivities of the monomers obey the Q–e scheme. Comparing the results obtained here with those previously reported for other monomers, we concluded that FMMA is one of the most highly reactive monomers among alkyl methacrylates.     

Silolene-Bridged zirconocenium polymerization catalysts

A new silolene-bridged compound, racemic (1,4-butanediyl) silylene-bis (1-η⁵-in-denyl) dichlorozirconium ( 1 ) was synthesized by reacting ZrCl₄ with C₄H₈Si (IndLi)₂ in THF. 1 was reacted with trialkylaluminum and then with triphenylcarbenium tetrakis (penta-fluorophenyl) borate ( 2 ) to produce in situ the zirconocenium ion ( 1 ⁺). This “constraint geometry” catalyst is exceedingly stereoselective for propylene polymerization at low temperature (T_p = ?55°C), producing refluxing n-heptane insoluble isotactic poly(propylene) (i-PP) with a yield of 99.4%, T_m = 164.3°C, δH_f = 20.22 cal/g and M?_w = 350 000. It has catalytic activities of 10⁷?10⁸ g PP/(mol Zr · [C₃H₆] · h) in propylene polymerization at the T_p ranging from ?55°C to 70°C, and 10⁸ polymer/(mol Zr · [monomer] · h) in ethylene polymerization. The stereospecificity of 1 ⁺ decreases gradually as T_p approaches 20°C. At higher temperatures the catalytic species rapidly loses stereochemical control. Under all experimental conditions 1 ⁺ is more stereospecific than the analogous cation derived from rac-dimethylsilylenebis (1-η⁵-indenyl)dichlorozirconium ( 4 ). The variations of polymerization activities in ethylene and in propylene for T_p from ?55°C to +70°C indicates a Michaelis Mention kinetics. The zirconocenium-propylene π-complex has a larger insertion rate constant but lower thermal stability than the corresponding ethylene π-complex. This catalyst copolymerizes ethylene and propylene with reactivity ratios of comparable magnitude r_E ? 4r_p. Furthermore, r_E.r_p ? 0.5 indicating random copolymer formation. Both 1 and 4 activated with methylaluminoxane (MAO) exhibit much slower polymerization rates, and, under certain conditions, a lower stereo-selectivity than the corresponding 1 ⁺ or 4 ⁺ system. © 1994 John Wiley & Sons, Inc.     

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     

Copolymerization parameters of acrolein and acidic vinyl monomers

Acrolein was copolymerized by radical initiation in aqueous solutions with sodium p-styrenesulfonate and acrylic acid, respectively, in the pH range of 3–7. The reactivities were shown to be pH-dependent. For the acrolein (M₁)–sodium p-styrenesulfonate (M₂) pair, r₁ = 0.33 ± 0.15 and r₂ = 0.32 ± 0.05 at pH 3; r₁ = 0.23 ± 0.12 and r₂ = 0.05 ± 0.03 at pH 5; r₁ = 0.26 ± 0.03 and r₂ = 0.025 ± 0.025 at pH 7. For the acrolein (M₁)–acrylic acid (M₂) pair, r₁ = 0.50 ± 0.30 and r₂ = 1.15 ± 0.2 at pH 3; r₁ = 2.40 ± 0.50 and r₂ = 0.05 ± 0.05 at pH 5; r₁ = 6.70 ± 3.00 and r₂ = 0.00 at pH 7. For acrolein, the new values of Q = 1.6 and e = 1.2 have been calculated. For sodium p-styrenesulfonate, the values Q = 0.76 and e = ?0.26 at pH 3, Q = 0.51 and e = ?0.87 at pH 5, Q = 0.39 and e = ?1.00 at pH 7 were obtained; and for acrylic acid, the values Q = 1.27 and e = 0.50 at pH 3, Q = 0.11 and e = ?0.22 at pH 5 were derived. The changes in reactivity are explained on the basis of inductive and resonance effects.