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.     

Photoinitiation, 6. Copolymerization of styrene with maleic anhydride photoinitiated by the excited charge-transfer complex styrene-maleic anhydride

The kinetics of styrene (St) copolymerization with maleic anhydride (MA) initiated by light (at λ = 365 nm) was studied in acetone, acetonitrile, chloroform, and N,N-dimethyl formamide at 30°C. With the exception of the chloroform containing system, the copolymerizations took place in homogeneous reaction media. The copolymerization rate R_p = ?d([St] + [MA])/dt was found to be a function of the mole ratio of the comonomers in the reaction mixture. For a given ratio of comonomers R_p and the molecular weight of the resulting copolymer were found to be a function of the donor number of the solvent used for a given rate of initiation. Due to the dependence of R_p on the concentration of an equimolar mixture of both comonomers in acetone on [St] (at constant [MA]), and on [MA] (at constant [St]) the participation of the exciplex {St…acetone}^* in the initiation reaction can be expected. The ratio of the overall rate constants for the propagation (k?_p) and termination (k?_t) reactions, k?_p/2k?_t, determined by a rotating sector technique, was found to depend on the composition of the comonomer mixture. The copolymerization rate is proportional to the square root of the intensity of incident light, which, together with the observed inhibition effect of oxygen points to a radical mechanism of the photoinitiated copolymerization of St with MA. In the presence of the photosensitizer benzophenone in the system St/MA/acetone an increase in R_p was observed, accompanied by a decrease in molecular weight of the copolymer in comparison with the system without benzophenone.     

Radical copolymerization of cyclic acetals derived from acrolein, 2. Alternating copolymerization

Copolymerizations of 2-vinyl-l,3-dioxane ( 1a ), 5,5-bis(hydroxymethyl)-2-vinyl-1,3-dioxane ( 1b ), and 5,5-dimethyl-2-vinyl-1,3-dioxane ( 1c ) with maleic anhydride (MA) and N-vinyl-2-pyrrolidone (NVP) were investigated. Copolymerization of the cyclic acetals 1 with MA yielded copolymers with perfectly alternating sequences independent of the initial monomer feed composition. Terpolymerization of 1a , MA, and styrene, also despite of monomer composition, yielded terpolymers with a molar composition of 50% in MA which confirms the participation of transfer complexes in these copolymerizations. The composition of the 1 /NVP copolymers (mole fraction) F₁(NVP) ≈ 0,6–0,8 also varied little with the feed. The copolymerization rates passed through a maximum when the monomer mixture contained a mole fraction f₁ (NVP) of ca. 0,7.     

Cyclo-copolymerization of 1,6-diene with monoolefin, 2. The copolymer composition equation and the relative rates of addition in the cyclo-copolymerization of diallyl ether with maleic anhydride and fumaronitrile

A copolymer composition equation is derived for the cyclo-copolymerization of a 1,6-diene with a monoolefin that do not homopolymerize. The theory is applied to the free radical copolymerization of diallyl ether (DAE) with maleic anhydride (MA) and to that of DAE with fumaronitrile (FN). Both systems fall in the special case where there are no unreacted C?C bonds left in the copolymer. The copolymer compositions are between 1:1 and 1:2 (=[diene]:[monoolefin]) over a wide range of monomer feed composition. The reactivity ratios obtained from the equation indicate that for the DAE/MA system, the intramolecular cyclization of the uncyclized DAE radical is 2,9 times more effective than the addition of MA monomer to the uncyclized DAE radical, and that for the system of DAE/FN, the intramolecular cyclization of DAE radical is 6,7 times more effective than the addition of FN monomer.     

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.     

Areca nut‐induced micronuclei and cytokinesis failure in Chinese hamster ovary cells is related to reactive oxygen species production and actin filament deregulation

Epidemiological studies have shown a strong association between environmental exposure to betel quid (BQ) and oral cancer. Areca nut (AN), an ingredient of BQ, contains genotoxic and mutagenic compounds. In this study, we found that AN extract (ANE) inhibited the growth of Chinese hamster ovary cells (CHO‐K1) in a dose‐ and time‐dependent manner. Intracellular reactive oxygen species (ROS) levels and micronuclei (MN) frequency were significantly increased following ANE treatment in CHO‐K1 cells. Addition of catalase markedly inhibited ANE‐induced MN formation, indicating that ANE‐induced genotoxicity was correlated with intracellular H₂O₂. Incubation of CHO‐K1 cells with ANE (400–800 μg/ml) for 24 hr caused G2/M arrest, and prolonged exposure to ANE (800 μg/ml) significantly induced cell death. Surprisingly, ANE itself caused cytokinesis failure and subsequent increase in binucleated cell formation. Coexposure to catalase (2,000 U/ml) and ANE (800 μg/ml) reduced the generation of binucleated cells, indicating that ANE‐induced cytokinesis failure was associated with oxidative stress. Following prolonged exposure to ANE, an accumulation of hyperploid/aneuploid cells concomitant with bi‐, micro‐ or multinucleated cells was found. In summary, our results demonstrate that ANE exposure to CHO‐K1 cells caused increased MN frequency, G2/M arrest, cytokinesis failure, and an accumulation of hyperploid/aneuploid cells. These events are associated with an increase in intracellular H₂O₂ level and actin filament disorganization. Environ. Mol. Mutagen., 2009. © 2009 Wiley‐Liss, Inc.     

Phase separation in random copolymers from high conversion free radical copolymerization, 1

The phase separation of random copolymers during free radical copolymerization to high conversion was studied. In order to prepare in situ high impact thermoplastics during the copolymerization process, the attention was focussed on systems in which the more reactive comonomers form thermoplastics, whereas the less reactive components form elastomeric homopolymers. The studied systems (A, B) were (AN, EA), (AN, VA), (CHMA, MA) and (S, BA) (AN: acrylonitrile, EA: ethyl acrylate, VA: vinyl acetate, CHMA: cyclohexyl methacrylate, MA: methyl acrylate, S: styrene, BA: butyl acrylate). These copolymers display varying compositional heterogeneity depending on the different radical reactivity ratios and the feed composition used. Curves of instantaneous copolymer composition versus fractional conversion and the distribution functions of chemical composition were calculated for the various systems. In addition, miscibility diagrams of corresponding low conversion copolymers A_xB_1−x and A_yB_1−y, derived from the same monomer pair (A, B) but differing in composition, were recorded at high temperatures. Phase separation was detected by light microscopy and differential scanning calorimetry (DSC) using cast films. The onset of phase separation depending on the actual stage of copolymerization was recorded. The composition of the copolymers at the onset of phase separation was compared with the miscibility of low conversion copolymer blends. A satisfactory prediction of the start of phase separation during copolymerization is presented.     

Syntheses and reactions of functional polymers. LX. Copolymerization of N-vinyl-pyrrolidone with methacrylic acid

The copolymerization of N-vinyl-pyrrolidone (VP) with methacrylic acid (MA) was studied and the following results were obtained. (1) The molar ratio M_VP/M_MA in the copolymer is ca. 1. (2) The rate of polymerization reaches a maximum for a molar ratio of the monomers M_VP/M_MA = 1. (3) The rate increases in mixtures of dimethylformamide (DMF) and methylene chloride as the content of CH₂Cl₂ increases. (4) The rate and the ratio M_VP/M_MA in the copolymer decreases in mixtures of DMF and water as the amount of water in increased.     

Free radical terpolymerization of three non‐homopolymerizable monomers, 2. Terpolymerization of N‐ethylmaleimide,anethol and trans‐stilbene

The free radical terpolymerization of N‐ethylmaleimide (NEMI), anethol (ANE) and trans‐stilbene (Stb) in CCl₄ at 60°C is described. For the first time, a new kinetic treatment has been applied to this ternary system in order to evaluate the degree of participation of free monomers and charge‐transfer complexes in the polymerization process. It can be shown that at low monomer concentrations, free monomers dominate the polymerization process, at medium monomer concentrations, both species participate to the same extent and at high monomer concentrations, the participation of charge‐transfer complexes increases strongly. The ternary system was also investigated according to the known terminal and complex model. The reactivity ratio according to the terminal model is k₁₂ /k₁₃ = 1,33, the reactivitity ratios according to the complex model are r_I = 1,0 and r_II = 0,7. The equilibrium constants for the formation of CT complexes between NEMI/ANE (C_I) and NEMI/Stb (C_II) at 25°C in CCl₄ were determined to be K_I = 0,34 L·mol^–1 and K_II = 0,21 L·mol^–1, respectively.     

Copolymerization of styrene with α-chloromaleic anhydride, 1. Mechanism of the radical-initiated copolymerization in 1,4-dioxane

The radical-initiated copolymerization of styrene (ST) with α-chloromaleic anhydride (CMA) in 1,4-dioxane was investigated. The formation of a 1:1 charge transfer (CT) complex between the comonomers in 1,4-dioxane at 25°C was confirmed by UV-spectroscopic studies, and the formation constant was found to be near zero, indicating that the complex is of contact type. An alternating copolymer was obtained by copolymerization over a relatively wide range of feed composition, and the monomer reactivity ratios, r_ST and r_CMA, were found to be 0,07 and 0,00, respectively, at 60°C. The copolymerization at a constant total monomer concentration showed a maximum rate at a styrene mole fraction of 0,4 in the feed. The copolymerization was interpreted by a consecutive monomer addition mechanism without taking into account a participation of the CT complex in the propagation.     

Synthesis and characterization of some acrylic monomer/sulfur dioxide copolymers

The copolymerization of acrylic monomers (M) [acrolein (AL), methyl acrylate (MA), acrylamide (AM) and acrylonitrile (AN)] with liquid sulfur dioxide (S) at low temperature and high dilution in the presence of tert-butyl hydroperoxide gives high SO₂ incorporation into the resulting copolymers. Analysis of the composition of these polysulfones, by elemental analyses and ¹³C NMR, shows that they consist mostly of the MMM, SMM, MMS and MSM triad monomer sequences. Thermal (TG) analyses of selected samples demonstrate that their thermal stability, up to 30% weight loss, increases for different acrylic comonomers as follows: AL < AM < MA < AN. Preliminary flammability tests revealed that flame retardancy increases with increasing SO₂ content in the copolymer.     

Copolymerizations of sodium 10-undecenoate with styrene and sodium acrylate

Copolymerizations of sodium 10-undecenoate ( 1 ) with styrene and sodium acrylate ( 2 ) were examined under irradiation with UV light. In the polymerization of 1 in the presence of styrene, solubilized in the aqueous solution of 1, 1 and styrene were found to polymerize independently of each other, and a copolymer was virtually not obtained. In the copolymerization of 1 with 2 , at concentrations of 1 higher than its pre-critical micelle concentration (0,04 mol · L^?1, pre-CMC), two kinds of copolymer were obtained, one consisting predominantly of 2 units, and another consisting of comparable amounts of both monomeric units. However, at concentrations of 1 lower than its pre-CMC, only one kind of copolymer was obtained, where the composition of the copolymer was a function of the monomer feed ratio. Reactivity ratios of the monomers were estimated in the absence of micelles of 1 (conc. < 0,04 mol · L^?1) to be r₁ = 0,28 ± 0,09 and r₂ = 3,0 ± 1,2, which is indicative of an ideal copolymerization system. The number-average degrees of polymerization (DP _n) of the copolymer did not exceed 7, a value much lower than that of poly( 1 ) obtained in the homopolymerization of 1 .     

Copolymerization and copolymers of N-(2,4,6-tribromophenyl)maleimide with methyl acrylate and methyl methacrylate

N-(2,4,6-Tribromophenyi)maleimide (TBPMI) was copolymerized with methyl acrylate (MA) or methyl methacrylate (MMA) in toluene solution using 2,2′-azoisobutyronitrile as free-radical initiation. The copolymerization reactivity ratios were found to be for the system TBPMI/MA r₁ = 0,095 ± 0,045 (TBPMI) and r₂ = 2,17 ± 0,142 (MA) and for the system TBPMI/MMA r₁ = 0,037 ± 0,042 (TBPMI) and r₂ = 4,32 ± 0,230 (MMA); Q and e values were also calculated. The initial rate of copolymerization, R_p, for TBPMI/MA sharply decreases as the content of TBPMI in the monomer mixture increases but the composition of the feed does not have a strong influence on R_p for the TBPMI/MMA copolymerization system. The course of copolymerization to high conversion is characterized by an increase of conversion up to a mole fraction of TBPMI of 0,7 in the monomer mixture, when MA was used as the comonomer. An opposite behaviour was found with MMA. Its copolymers show a considerable increase of thermal stability as well as of the glass transition temperatures with increasing TBPMI content.     

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.     

Relation between the alternating monomer unit sequence and the cis and trans linkage configurations at the cyclic maleic anhydride units in the copolymers of styrene and maleic anhydride prepared in carbon tetrachloride

The monomer unit triad sequence distribution and the cis/trans linkage configurations at the cyclic maleic anhydride (MA) units in the copolymers of styrene (ST) and MA prepared in CCl₄ with AIBN at 50°C were quantitatively determined by ¹³C DEPT NMR spectroscopy. So much as 61 % of the linkages at the MA units were found to be in cis configuration, which was considered to be formed by a participation of the 1:1 electron donor-acceptor complex formed between ST and MA in the propagation step. The mole fraction of the cis configuration was found to be proportional to the mole fraction of alternating triad sequences when the monomer unit sequences approach to be completely alternating. This supported the proposal that, in alternating and semi-alternating copolymerizations, the alternating sequences were formed mainly by the addition of the complex. The equilibrium constant of the complexation in CCl₄ at 23°C was determined to be 0,21 L/mol.     

Copolymerization of styrene and butadiene with Co(acac)3‐methylaluminoxane catalyst

The copolymerization of Styrene (St) and butadiene (Bd) with Co(acac)₃‐MAO catalyst was investigated. The copolymers consisting of St and Bd with highly cis‐1,4‐structure could be synthesized with Co‐(acac)₃‐MAO catalyst without formation of homopolymer, although the St contents in the copolymer were not high. The copolymer composition curve for copolymerization of St and Bd with the Co(acac)₃‐MAO is different from that obtained with the Ni(acac)₂‐MAO catalyst. The additive effects of triphenylphosphine (TPP) and trifluoroacetic acid (TFA) on the copolymerization of St and Bd with the Co(acac)₃‐MAO catalyst were also investigated. The copolymer yields increased by adding TPP to the Co‐(acac)₃‐MAO catalyst, although the St contents in the copolymer did not change. In the microstructure of the Bd units in the copolymers, 1,2‐contents increased remarkably. The copolymer yields and the microstructure of the copolymer did not change by addition of TFA.     

Comparative 1H NMR studies of saturation transfer in copolymer gels and mouse lenses

Saturation transfer in cross‐linked copolymer gels and excised intact and perforating trauma‐induced cataract mouse lenses (4‐ or 8‐week‐old) were studied using intermolecular cross‐relaxation rates (1/T_IS(H₂O); 1/T_IS), monitored with f₂‐irradiation at ?8.79, ?4.00, and 7.13 ppm (γH₂/2π ～ 69 Hz). [1] The 1/T_IS(7.13 ppm) vs dry weight [W (%)] profiles for hydrophilic copolymer gels were far steeper than those for hydrophobic copolymer gels, indicating the participation of an amount of bound water and a number of copolymer hydroxyl groups in the saturation transfer process. In contrast, the 1/T_IS(?8.79 ppm) vs W (%) profiles exhibited little difference between the hydrophilic and hydrophobic copolymer gels, indicating the major participation of molecular rigidity, i.e. W (%) in the saturation transfer process. [2] The 1/T_IS(7.13 ppm) values for cataractous mouse lenses were larger than those for intact lenses, indicating the formation of large, immobile lens protein associates or aggregates containing a sufficient amount of bound water for the saturation transfer. [3] The 1/T_IS(7.13 ppm) vs W (%) profiles for the hydrophilic copolymer gels exhibited similar characteristics to the intact and cataractous mouse lenses with regard to the saturation transfer process. Copyright © 2010 John Wiley & Sons, Ltd.     

Optically active polymers, 2. Copolymerization of limonene with maleic anhydride

Copolymerization of maleic anhydride (MA) and (R),(S)-limonene (LIM) was studied in various solvents, using 2,2′-azoisobutyronitrile (AIBN) and benzoyl peroxide (BPO) as initiators and radiation (⁶⁰Co γ-source) within the temperature range of 20–70°C. Regardless of conversion or initial comonomer feed ratios, the composition of LIM-MA copolymers ranged from about 1 : 1 to 1 : 1,6 and was dependent on the reaction conditions, leading to a formation of materials with diverse solubilities, degrees of crosslinking and molecular weights. The main product consists of a 1 : 1 LIM-MA copolymer with pendant 4-methyl-3-cyclohexenyl residues. At higher conversion these alicyclic unsaturations lead to crosslinking. No reference to cyclocopolymerization was detected.     

Surface characterizations of copolymer films with pendant monosaccharides

We copolymerized a monomer with a pendant glucose unit (GEMA) with methyl methacrylate (MMA) and prepared copolymer films with pendant monosaccharides by casting the copolymer solution on glass plates. The surfaces of the copolymer films were characterized by contact angle measurements, X-ray photoelectron spectroscopy (XPS) and protein adsorption measurements, and compared with the surface of 2-hydroxyethyl methacrylate (HEMA)-MMA copolymer films. The surface free energy of the GEMA-MMA and HEMA-MMA copolymer was calculated from the contact angle of methylene diiodide and glycerol on the copolymer films. The surface free energy of the films increased gradually with increasing GEMA or HEMA content. The surface free energy of GEMA-MMA copolymers was larger than that of HEMA-MMA copolymers in the whole range of composition. The results of XPS measurements suggest that the fraction of GEMA at the copolymer surface increases as the content of GEMA in the copolymer increases. This indicates that introduction of GEMA makes the copolymer surface more hydrophilic. Further more, the higher the GEMA content is, the smaller amounts of fibrinogen and γ-globulin are adsorbed at the copolymer surface. The copolymer with a GEMA content of 20 mol-% hardly adsorbs fibrinogen and γ-globulin at all.     

Copolymerization of Ethylene Carbonate and 1,2‐Propylene Carbonate with Tetramethylene Urea and Characterization of the Polyurethanes

Summary: Tetramethylene urea (TeU, 1 ) is successfully copolymerized with 1,2‐propylene carbonate (PC, 2 ) leading to a polyurethane ( = 12 200; 18 400; = 1.50) with a T_m of 145.7 °C and a T_g of 53.7 °C. Mechanistic studies with a blocked isocyanate model compound revealed that, at no stage of the reaction is the TeU ring opened to form an isocyanate. Hence, a well‐underlined mechanism for the copolymerization is proposed. Furthermore, TeU is successfully copolymerized with mixtures of PC and ethylene carbonate (EC, 3 ). From NMR spectroscopic data of the polyurethanes obtained, it is concluded that PC is less reactive than EC. However, it is possible to increase the PC content in poly(TeU‐EC‐stat‐TeU‐PC) by increasing the PC/EC ratio in the feed. ¹³C NMR spectroscopy reveals that a random copolymer is obtained. This conclusion is supported by differential scanning calorimetry (DSC) data, which show a continuous decrease in T_m with increasing PC content.

T_m was found to decrease with increasing PC content.