Ring-opening-closing alternating copolymerization of 2-methyl-2-oxazoline with N-methyldiacrylamide

This paper describes a new ring-opening-closing alternating copolymerization (ROCAC) of 2-methyl-2-oxazoline (five-membered cyclic imino ether, 1 ) with N-methyldiacrylamide ( 2 ). The reaction of a 1 : 1 monomer feed ratio proceeded without any added catalyst to give an alternating copolymer 3 having two structural units formed by ring-opening and ring-closing (cyclization). The structure of copolymer 3 was determined by ¹H, ¹³C NMR, and IR spectroscopies. The extent of cyclization was at most 65%. The copolymerization was reasonably explained by a mechanism of propagation via zwitterion intermediates.     

Poly(germanium thiolate): a new class of organometallic polymers having a germanium-sulfur bond in the main chain

A novel germanium-containing copolymer 3 a having a germanium(IV) unit and a trimethylene sulfide unit alternatingly in the main chain was prepared by the combined use of a germylene, 1,3-bis(trimethylsilyl)-1,3-diaza-2-germa(II)-indan ( 1 a ) and thietane ( 2 ). The resulting copolymer has a very high molecular weight (M?_w > 10⁶). The usage of a germylene, bis[bis(trimethylsilyl)aminato]germanium(II) ( 1 b ), as a comonomer also gave an alternating copolymer 3 b with high molecular weight in good yields. On the other hand, the reaction of a germylene, bis(N-trimethylsilyl-tert-butylaminato)germanium(II) ( c ), with thietane afforded a 1 : 1 adduct 4c having a 1-thia-2-germacyclopentane structure without producing an alternating copolymer.     

Stereochemistry of copolymerization of optically active cyclohexylepoxyethane with carbon dioxide

The stereochemistry of alternating copolymerization of carbon dioxide with S-(+)-cyclohexylepoxyethane ( 1 ) using a diethylzinc/water system as catalyst was investigated. The optically active copolymer, poly[(oxycarbonyloxy)-1-cyclohexylethylene], was hydrolyzed and the epoxide was transformed into the form 1,2-bis(trimethylsilyloxy)-1-cyclohexylethane ( 2 ). From the determination of optical activity of this ether, it is concluded that the ring opening of 1 in the copolymerization takes place predominantly at the methylene-oxygen linkage.     

Spontaneous alternating copolymerization of methoxyallene with 7,7,8,8‐tetracyanoquinodimethane through a zwitterionic intermediate

Spontaneous copolymerization of methoxallene with 7,7,8,8‐tetracyanhoquinodimethane (TCNQ) was carried out. The obtained copolymer mainly consisted of 2,3‐polymerized methoxyallene units and TCNQ. The copolymer composition was 1 : 1 irrespective of the monomer feed ratios, suggesting that an alternating copolymerization occurred. UV‐Vis and ESR spectroscopic studies supported that the active species of the copolymerization was a zwitterion generated through a single electron transfer reaction from methoxyallene to TCNQ.     

Copolymerization of vinyl chloride and methyl acrylate catalyzed by ethylaluminium compounds

The copolymerization of vinyl chloride (VC) and methyl acrylate (MA) in the presence of ethylaluminium compounds (C₂H₅AlCl₂, (C₂H₅)₂AlCl, and (C₂H₅)₃Al) at low ethylaluminium compound (EAC)/MA mole ratios was investigated. An alternating copolymer was produced in this reaction when an excess of VC in the initial monomer feed was used. The addition of dibenzoyl peroxide (BPO) to the systems containing EAC resulted in an increase of the alternating copolymer yield. In polymerization systems containing EAC resulted in an increase of the alternating copolymer yield. In polymerization systems containing EAC combined with VOCl₃ an enhancement of the alternating copolymer yield and formation of VC-rich copolymers were observed. In the polymerization system with (C₂H₅)₃Al? VOCl₃ a VC-rich copolymer was the main product. It was concluded that VC-rich copolymers are formed in the random radical copolymerization which occurs when most of EAC is complexed by the alternating copolymer chain. The structure of alternating and VC-rich copolymers was studied in detail by means of ¹³C NMR spectroscopy.     

Alternating copolymerization of cyclohexene oxide and sulfur dioxide

Copolymerization of cyclohexene oxide (CHO) and sulfur dioxide (SO₂) was conducted at 80°C by using a variety of catalysts both in the presence and absence of solvent. Aromatic tertiary amines such as pyridine gave an alternating copolymer of CHO and SO₂ in the presence of solvents such as 1,2-dimethoxyethane. The alternating copolymer obtained was a white thermoplastic which could readily be thermoformed. It was soluble in acetone and chloroform but insoluble in water and hexane. From the reaction of the equimolar mixture of CHO, SO₂ and pyridine at 20°C, an 1 : 1 : 1 adduct of CHO, SO₂ and pyridine (see formula 2 ) could be isolated. This adduct was confirmed to be the active species for the present copolymerization.     

Copolymerization of carbon dioxide with propylene oxide in the presence of catalysts based on alkylmetal compounds and pyrogallol

Carbon dioxide was copolymerized with propylene oxide (PO, 2-methyloxirane) in the presence of a catalyst system based on alkylmetal compounds (MtR_n, Mt = Zn, Cd, Al) and pyrogallol (PG) at mole ratios 1:1, 2:1, and 3:1, respectively. The reaction was found to produce an alternating copolymer poly(propylene carbonate), [poly(oxycarbonyloxypropylene)], using Zn and Cd containing catalysts and non-alternating copolymers with Al containing catalysts. For the system ZnR₂/PG (mole ratio 2 : 1), the most active system, the influence of substituents R at the zinc atom, as well as effects of solvents and complexing agents on the copolymer yield and intrinsic viscosity were investigated. The results are discussed in terms of an anionic coordinative copolymerization mechanism.     

Copolymerization of methyl acrylate with isobutylene in the presence of lewis acids

The copolymerization of methyl acrylate (MA) and isobutylene (IB) in the presence of Lewis acids (EtAlCl₂, Et₂AlCl, Et₃Al, AlCl₃, and ZnCl₂) at low Lewis acid/MA mole ratio was investigated. EtAlCl₂ and Et₂AlCl were found to initiate the spontaneous reaction. An alternating copolymer was produced in this reaction when an excess of IB in the initial monomer feed was used. The copolymerization in the presence of Et₃Al, AlCl₃, and ZnCl₂ did not proceed spontaneously and was initiated by dibenzoyl peroxide (BPO). In this case MA-rich copolymers are formed even in systems containing a large excess of IB in the monomer feed. The addition of BPO to systems containing ethylaluminium chlorides strongly diminishes the tendency towards alternating propagation. It was concluded that the mode of initiation has a significant influence on the copolymer composition. The alternating copolymerization by EtAlCl₂ was studied in detail in order to determine the influence of the catalyst concentration, monomer feed ratio, reaction temperature and time on the monomer conversion, copolymer composition, molecular weight and tacticity.     

1H NMR study of random and alternating styrene/n-alkyl methacrylate copolymers

The ¹H NMR spectra of random and alternating copolymers of styrene and methyl methacrylate, ethyl methacrylate, butyl methacrylate, and octyl methacrylate were analyzed. In the first approximation, the one-parameter statistics suggested for the interpretation of these spectra is in agreement with the experimental data. The way in which the copolymer is synthesized and the copolymerization mechanism following therefrom markedly affect the magnitude of the parameter of coisotacticity σ: for all comonomer pairs under study, σ is higher if an organometallic catalyst is used (alternating copolymerization) than in the case of a radical initiator (statistical copolymerization). With increasing number of carbon atoms in the n-alkyl alcohol residue, σ decreases to a limiting value.     

Strictly alternating copolymers containing parabanic acid and amide or imide moieties

1,3-Bis(4-aminophenyl)imidazolidinetrione dihydrochloride ( 1 ) was synthesized and used as starting material for the synthesis of strictly alternating copolymers. Fully aromatic copolymers containing parabanic acid and amide moieties ( 7a, b ) were found to exhibit high glass temperatures and good thermal stability. Meltable copolymers with parabanic acid and amide moieties ( 7d–j ) could be obtained by introducing flexible aliphatic spacers. The use of an unusually short, but symmetrically branched spacer was particularly effective. The strictly alternating, thermally stable copolymer 10 was synthesized from 1 and pyromellitic dianhydride. By using the trimethylsilyl ester of polyamic acid 11 , the imidization temperature could be lowered by 100°C.     

Synthesis of functional unsaturated polyesters using rare earth coordination catalysts, 3. Mechanistic aspects of maleic anhydride-epichlorohydrin copolymerization with Nd[(RO)2 PO2]3/Al[CH2CH(CH3)2]3 as a catalyst

Ring-opening alternating copolymerization of maleic anhydride and epichlorohydrin was carried out at 70°C with rare earth coordination catalysts composed of Nd[(RO)₂ PO₂]₃ (R = CH₃(CH₂)₃CH(C₂H₅)CH₂? )and trialkylaluminium. Anlaysis of end-groups showed that the copolymer chain contains one ? OH and one ? CH?CH? CO? CH₂CH(CH₃)₂ end-group. IR, UV-Vis, ¹H NMR and GPC results imply that a catalyst-maleic anhyride complex is formed in the initiation step that the ring-opening copolymerization proceeds via coordinate insertion mechanism accompanied with chain-transfer.     

Copolymerization of 1-vinylindol with maleic anhydride

The formation of a charge-transfer complex between 1-vinylindole ( 1a ) and maleic anhydride (MA) was detected by ¹H NMR analysis, and the corresponding K_eq was measured (K_eq=0,251 mol in CDCl₃ at 25°C). It could be shown that this complex can be involved both in the initiation and propagation steps of the 1a -MA copolymerization by carrying out spontaneous copolymerization experiments and studying the influence of the feed composition on the conversion and [η] of the copolymer. The structure of the 1a -MA copolymer, investigated by ¹³C NMR spectroscopy, was found to be complicated due to the formation of indoline rings along the chains by an attack of the propagating MA radical at position 2 in the indole ring. As a consequence an excess of MA, with respect to a 1:1 mole ratio of monomer feed, was usually found in the copolymer. The mechanism of the cyclization reaction was clarified by copolymerizing MA with 2-methyl-1-vinylindole ( 1b ), 3-methyl-1-vinylindole ( 1c ), or 2,3-dimethyl-1-vinylindole ( 1d ). An alternating copolymer with MA (mole ratio 1:1 of monomeric units), without irregularities, was obtained only by employing 1d as a comonomer.     

Stereochemistry of copolymerization of optically active 3-phenyl-1,2-epoxypropane with carbon dioxide

The stereochemistry of alternating copolymerization of carbon dioxide with S-(–)-3-phenyl-1,2-epoxypropane ( 5 ) using a diethylzinc/water system as catalyst was investigated. The optically active copolymer, poly[(oxycarbonyloxy)-1-benzylethylene] ( 6 ), was hydrolyzed and the epoxide unit was transformed into the form of 1,2-bis(trimethylsilyloxy)-3-phenylpropane ( 8 ). From the determination of optical activity of this ether, it is concluded that the ring opening of 5 in the copolymerization takes place predominantly at the methylene-oxygen linkage. The substituent effect on the ring opening mode of oxiranes is also discussed.     

Spontaneous copolymerization of 1-(2-hydroxyethyl)aziridine with β-butyrolactone, 14

The copolymerization of 1-(2-hydroxyethyl)aziridine ( 1 ) as nucleophilic monomer with β-butyrolactone ( 2 ) as electrophilic monomer without initiator in solution at 45°C was investigated. Copolymers were characterized by IR and ¹H NMR spectroscopy. By elemental analyses it could be shown that their compositions depend on the monomer ratio in the feed. From the copolymer composition and ¹H NMR spectra it was possible to suggest four probable copolymer structures.     

Copolymerization via zwitterion, 5. β-butyrolactone and 2-methyl-2-oxazoline

The zwitterionic copolymerization of 2-methyl-2-oxazoline (MOX) as nucleophilic monomer with β-butyrolactone (BUL) as electrophilic monomer was investigated in bulk and in solution (CH₃CN) at 45°C. The copolymer composition was around 1,5/1,0 (BUL/MOX) as was established by ¹H NMR. ¹H and ¹³C NMR spectroscopy were used to identify the copolymers. The IR spectroscopy supported the NMR results. On the other hand, the copolymers behave as polyelectrolytes, according to viscosity determinations. A copolymerization mechanism through a zwitterion species is suggested.     

Copolymerization of carbon dioxide and some oxiranes by organoaluminium catalysts

Carbon dioxide was copolymerized with methyloxirane and 7-oxabicyclo[4.1.0]heptane using triethylaluminium as a catalyst component. Factors to control the copolymer composition were sought on the basis of an assumed copolymerization mechanism. Compared to nonpolar solvents, ethereal solvents were found to increase the carbon dioxide content in the copolymer obtained by the triethylaluminium/water system, giving a fraction with almost alternating sequence. The addition of a Lewis base, especially treiphenylphosphine, to triethylaluminium was also useful to get copolymers of high carbon dioxide content. The coincidence of these results with the expectation from the assumed copolymerization scheme clearly indicates that the copolymerization proceeds through a coordinated anionic mechanism.     

Discussion on the mechanism of alternating copolymerization of styrene and maleic anhydride

To clear up the detailed mechanism of the alternating copolymerization of styrene (St) and maleic anhydride (MAn) concerning the initiation species, the propagation species, the tendency of the chain transfer reaction as well as the directional tendency of the reaction between copolymer radicals and monomer complexes, the role of the charge transfer complexes, characterization of end groups and additional donor effects were examined. The equilibrium constant of the St/MAn (1 : 1) complex was determined to be 0.31 by NMR spectroscopy, that suggested considerable amounts of complexes existing in the system. As expected, a small quantity of initiator (¹⁴C-azobisisobutyronitrile (AIBN)) was incorporated into the St/MAn copolymer. Chlorine atoms were scarcely incorporated into the copolymer synthesized in CCl₄ with AIBN or benzoyl peroxide (BPO) as an initiator. Hence the copolymerization was considered to be induced only by attacke of initiator radicals to the monomer or the complexes, contrary to the usual conception of telomerization. When the electron donor monomer was added to the system, the terpolymerization could be treated as a copolymerization of the two complexes, i.e., St/MAn and Donor/MAn. By adding naphthalene the rate maximum point shifted from higher concentration of MAn to the equivalent concentration of St and MAn. Degradative chain transfer to N.N-dimethylaniline was observed, confirming the existance of poly-MAn radicals. It was suggested from these results that the charge transfer complex and uncomplexed MAn took part in the copolymerization of St and MAn. This was proved kinetically. The whole mechanism was discussed.     

Solvent effect on the asymmetric induction copolymerization of styrene with maleic anhydride in the presence of lecithin

The asymmetric induction radical copolymerization of styrene (St) with maleic anhydride (MAn) was studied in various solvents with different dielectric constants in the presence of lecithin as a chiral surfactant. The observed specific rotation of the resulting alternating copolymer decreased with an increase in the dielectric constant of the solvent used. It was concluded that the asymmetric induction depends mainly upon the incorporation of MAn within the reversed lecithin micelles.     

Ternary polymerization catalyst consisting of group ii metal halide,triethylaluminum and carbon tetrachloride

The present paper describes the ternary catalyst system consisting of Group II metal halides, AlEt₃, and CCl₄, which initiatesatroom temperature the polymerizations of ethylene (60 atmospheres), styrene, vinyl acetate, methyl methacrylate, acrylonitrile, and isobutyl vinyl ether. As the component of Group II metal halide, ZnCl₂, ZnI₂, CdCl₂, MgCl₂, and BeCl₂ were effective. This catalyst system induced the cationic polymerization of vinyl ether. On the other hand, the copolymer composition curve of the styrene-methacrylate copolymerization with this catalyst system was close to that of free radical copolymerization. In addition, this catalyst system has also been characterized by the 1:1 alternating copolymerization of ethylene with vinyl acetate at room temperature.     

Mechanistic study of the light‐induced copolymerization of maleimide/vinyl ether systems

Real‐time infrared spectroscopy was used to monitor the high‐speed copolymerization of N‐substituted alkyl maleimide (MI) and vinyl ether (VE) mixtures upon UV exposure, with or without photoinitiator. The monomer feed composition was shown to play a decisive role on the polymerization kinetics of each monomer. When VE is in excess, the two monomers disappear at similar rates to yield an alternating copolymer. When MI is in excess, the copolymerization and the MI homopolymerization occur simultaneously to yield a copolymer with isolated VE units. The reaction scheme proposed to account for the kinetic data is based on the homopolymerization of a donor‐acceptor complex, with the VE∗︁ radicals acting as the main propagating species. The kinetic chain length was evaluated from quantum yield measurements performed under controlled initiation conditions and found to be on the order of 10³. The propagation rate constant of the VE/MI copolymerization was calculated to be twice that of the MI homopolymerization.