Monte Carlo Study of Binary Copolymerizations. 2. The Determination of Reactivity Ratios,Applications

This paper discusses an improved and efficient version of the MEMØRY-7 computer program described in a previous paper. The program, called MEMØRY-7/1, implements a Monte Carlo algorithm to compute reactivity ratios in binary irreversible copolymerizations. For the copolymerization of acrylic acid and methyl acrylate, the computed r₁, r₂ values (r₁ = 1.374, r₂ = 1.038) compare quite well with experimentally determined ones (r₁ = 1.4, r₂ = 1.0; Eldridge and Treloar).     

A microcomputer program for estimation of copolymerization reactivity ratios

A user-friendly program has been developed to estimate copolymerization reactivity ratios based on a nonlinear minimization algorithm. The use of an optimal experimental design for copolymerization when the Mayo–Lewis model applies is presented. The applicability of the program is demonstrated using actual and simulated experimental data.     

Monte Carlo-studium der reversiblen copolymerisation. I. Theorie,memøry-6 programm,anwendungen

The binary reversible copolymerization, taking into account the length of the terminal sequence, are studied by the Monte Carlo method. We discuss the theoretical model, the algorithm, and a FR?RAN program. Finally, the α-methylstyrene-methyl methacrylate copolymerization is studied by means of the proposed Monte Carlo model, and the results obtained are compared with those obtained using the Markov chain model and Wittmer's equations.     

Das Monte Carlo-studium der binären copolymerisation in der annahme des vorletzten Effektes. I. Theorie,MEMORY 5-programm,anwendungen

This paper presents a mathematical model (using the Monte Carlo technique) for the building of a binary copolymer considering the penultimate effect. One discusses the algorithm and the computer implementation. Finally, two applications are given. The purpose of this series of papers is to provide a Monte Carlo method to compute the sequence distribution for the hypothesis of penultimate effect (program MEMORY 5), ultimate effect (program MEMORY 3), and copolymerization with depolymerization (program MEMORY 6).     

Polymerizability,copolymerizability, and properties of cyanoacrylate‐telechelic polyisobutylenes II: copolymerization of three‐arm star cyanoacrylate‐ telechelic polyisobutylene with ethyl cyanoacrylate

This research concerned the synthesis and characterization of novel conetworks containing polyisobutylene (PIB) and polyethyl‐2‐cyanoacrylate [poly(Et‐CA)] sequences. The syntheses involved the copolymerization of CA‐telechelic three‐arm star PIB [Ø(PIB‐CA)₃] with ethyl‐2‐cyanoacrylate (Et‐CA) mediated by nucleophiles or by living tissue (fresh eggs). The conetworks were characterized by swelling in hexanes, tetrahydrofuran (THF), and acetone, and the results indicate co‐continuous PIB and poly(Et‐CA) domains. The conetworks exhibit two T_gs indicating phase‐separation between PIB and poly(Et‐CA). The outstanding oxidative resistance of the conetworks was demonstrated by exposure to concentrated nitric acid. The tensile strengths, moduli, and elongations of a series of conetworks with different overall compositions were investigated and the findings interpreted in terms of covalently linked rubbery and glassy domains. AFM also suggests the presence of phase‐separated rubbery and glassy domains. DMTA spectra of a Ø(PIB‐CA)₃ homonetwork, and Ø(PIB‐CA)₃/Et‐CA conetworks were analyzed and interpreted in terms of coexisting rubbery and glassy domains. Observations made during the exposure of Ø(PIB‐CA)₃/Et‐CA mixtures to proteinaceous tissue, in combination with characterization data, were used to propose a structural model for the conetworks. Copyright © 2007 John Wiley & Sons, Ltd.     

Microemulsion copolymerization of styrene and acrylonitrile with n‐butanol as the cosurfactant

The microemulsion copolymerization of styrene and acrylonitrile in an n‐butanol/cetyltrimethylammonium bromide/oil/water microemulsion system was studied. The solubilization sites of the two monomers were determined with an NMR technique. The results showed that the solubilization behaviors of the two monomers were quite different. Most of the styrene was solubilized in the palisade layer of the microemulsion, whereas the acrylonitrile had an equilibrium distribution in the aqueous phase and palisade layer of the microemulsion. The reactivity ratios of styrene and acrylonitrile in the microemulsion system were different from those in other media. The effect of the monomer feed composition on the copolymerization kinetics was investigated, and the mechanism of nucleation of the latex particles was examined. The experimental results showed that the copolymerization loci were changed from the microemulsion droplets to the aqueous phase when the concentration of acrylonitrile in the monomer feed reached approximately 80%; this could be further proved by the effect of the monomer feed composition on the copolymerization kinetics. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 203–216, 2005     

Copolymerization of 2,2-diallyl-1,1,3,3-tetraethylguanidinium chloride with N-substituted maleimides

The free-radical copolymerization of 2,2-diallyl-1,1,3,3-tetraethylguanidinium chloride with N-phenyl- and N-p-carboxyphenylmaleimide is studied in bulk and in organic solvents. It is shown that copolymerization proceeds to form copolymers with a high tendency toward alternation of monomer units. The kinetic laws of the reaction are investigated, and the relative activities of the monomers are determined. It is found that 2,2-diallyl-1,1,3,3-tetraethylguanidinium chloride is involved in copolymerization with N-substituted maleimides to give rise to pyrrolidinium structures. This work was supported by the Russian Foundation for Basic Research (project no. 09-03-00220) and the by the Presidium of the Russian Academy of Sciences through the program Development of Methods of Synthesis of Chemical Substances and the Creation of Novel Materials.     

Thermal behaviours of sulphur-selenium mixtures

The thermal behaviours of sulphur, selenium and their mixtures have been studied over the range 40–450?. It has been shown that the polymerization threshold temperature of sulphur,T _Ø, decreases with increasing selenium content and follows the equilibrium copolymerization model proposed by Tobolsky and Owen. The formation of octa-atomic species Se_8?xS_x, where 8 >x > 4, takes place only after sulphur is in the liquid state. The rate of polymerization is enhanced by the addition of increasing amounts of selenium and this is reflected in the higher polymerization peak temperatures. The X-ray powder diffractograms show that all the sulphur-selenium melts belong to the same phase as that of SeS, though the constituent atoms are randomly distributed.     

STUDY ON THE SEQUENCE STRUCTURE OF SBR BY 13C-NMR METHOD Ⅵ MONTE CARLO SIMULATION OF THE SEQUENCE OF SBR

A program of Monte Carlo simulation of binary copolymerization for E-SBR (emulsion polymn. SB rubber) was made according to the terminal model. The simulation results obtained by this program were in good agreement with those experimental ones. A detail microstructure information of E-SBR molecular chain has been provided.     

A program generator for describing copolymerization and network formation in step reactions

A multi-purpose computer program has been developed for describing copolymerization and network formation in step reactions. It operates at two hierarchical levels: a generation level and an application level. At the generation level, the class of problems is defined and prepared, and this information is used to generate automatically a problem-specific program based on generalized concepts of the branching theory. At the application level, the problem-specific program can be used for model calculations with all possible variations in recipes and kinetic parameters within the boundaries of the specific class of processes concerned.     

Networks and conetworks of PIB‐based cyanoacrylate‐telechelic prepolymers: Synthesis,characterization, and properties

Novel networks and conetworks were prepared by the instantaneous polymerization of cyanoacrylate‐telechelic three‐arm star polyisobutylene [Ø(PIB‐CA)₃] and the copolymerization of Ø(PIB‐CA)₃/2,4,4‐trimethylpentane cyanoacrylate (TMP‐CA) mixtures, respectively, by means of strong nucleophiles, such as NEt₂‐telechleic linear or three‐arm star PIBs [Ø(PIB‐NEt₂)_{2 or 3}]. The reactants were combined in the bulk in double‐barrel syringes by reaction injection molding (RIM). The chemical and mechanical properties of products prepared in the bulk and by conventional solution techniques were characterized by various techniques (swelling, extractables, FTIR and NMR spectroscopies, Instron, microhardness, oxidative resistance, DSC, DMTA). Conditions for the preparation of rubbery materials for possible biomedical applications were developed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2612–2623, 2008     

Monte Carlo-studium der ireversiblen terpolymerisation: Das modell und anwendungen

The Monte Carlo model of the ternary irreversible copolymerization is presented. The computer program MEMøRY-4, which implements the described model, is used to study the methyl methacrylate/methyl acrylate/maleic anhydride, butadiene/styrene/2-methyl-5-vinylpyridine, and styrene/methacrylonitrile/α-methyl styrene terpolymers. One discusses the problem of transferability of reactivity ratios determined for binary copolymerizations to the ternary ones. It can be concluded that the transferability is not assured, but using only composition data it is difficult to achieve a safe conclusion (Fisher statistics).     

Copolymerization kinetics of a model siloxane system

Using ²⁹Si NMR, we monitor the copolymerization of trimethylethoxysilane and dimethyldiethoxysilane (model compounds for more complex sol-gel copolymer systems) in a batch reactor. Under the chosen conditions, the extents of self- and cross-condensation reactions are readily determined. Using a nonideal polycondensation kinetic model, we show that the copolymerization rate coefficient for a pair of sites of differing functionality is bounded by their homopolymerization rate coefficients, lying closer to the larger one. This reactivity pattern generates a heterogeneous monomer distribution in the copolymerization products. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1293–1302, 1997     

Termination Rates in Free Radical Copolymerizations

The rates of free radical copolymerizations at given rates of initiation can be analyzed ideally in terms of monomer feed concentrations and reactivity ratios, propagation rate constants for homopolymerizations of the particular monomers, and an overall rate constant for termination during copolymerization. This model, which is due to Atherton and North, can account for the effects of initiator concentration and viscosity of the polymerization medium on copolymerization rates.

This article reports an empirical formulation for the overall termination rate constant in terms of monomer concentrations and reactivity ratios and a cross-termination factor. The new model accounts for experimental data in the styrene-methyl methacrylate system in which polarity differences between unlike radicals may result in enhanced termination rates. It also predicts observed copolymerization rates of methyl methacrylate-vinyl acetate and styrene-α-methylstyrene mixtures in which polarity effects are absent. The cross-termination factor may be approximated from reactivity ratio data for predictive purposes.     

NON-LINEAR LEAST SQUARE CURVE FITTING OF COPOLYMERIZATION MODELS TO THE ALTERNATING TRIAD FRACTION OF COPOLYMERS OF STYRENE AND CITRACONIC ANHYDRIDE,AND COPOLYMERS OF STYRENE AND MALEIC ANHYDRIDE PREPARED IN N,N-DIMETHYLFORMAMIDE

Copolymers of styrene (ST) and citraconic anhydride (α-methylmaleic anhydride) (CA) were prepared in a very polar solvent, N,N-dimethylformamide (DMF), at 50.0°C with AIBN. The monomer unit triad fractions were determined by ¹³C NMR in acetone-d ₆ solution. Non linear least square (NLLS) curve fitting was performed for the copolymerization models of the terminal model, the penultimate unit effect model, the complex participation model, the complex dissociation model, and the so-called comppen model. The theoretical equations for the ST-centered alternating triad mole fraction were fitted by NLLS minimization routine to the triad fraction data of the ST-CA copolymers and that of the ST-maleic anhydride (MA) copolymers prepared in identical polymerization conditions. It was found that for rigidly alternating copolymers of ST-MA, the difference among the copolymerization models disappeared and all models merged together. The difference among the copolymerization models were somewhat more apparent for less alternating copolymers of ST-CA copolymers. The sum of squares values indicated that the copolymerization models, which involved some complex participation, fit the data better with the comppen model. This was a combination of a complex participation and penultimate unit effects, which performed best.     

Polyglycolic acid copolymers from one‐step cationic polymerization of formaldehyde,carbon monoxide,and epoxides derived from PEG

Biodegradable polyglycolic acid (PGA) is conventionally produced via the ring‐opening polymerization of glycolide, the cyclic dimer form of glycolic acid, in the presence of mostly tin‐based catalyst initiators which are rather known to be cytotoxic materials. Our previous studies revealed an alternative method for the synthesis of PGA from the perfectly alternating copolymerization of formaldehyde (from trioxane) and carbon monoxide (CO) under BrØnsted acidic conditions. The poor physical properties of PGA (insolubility in many organic solvents, brown color, etc.) limit its use in other marketing applications in the industry. To improve on the physical properties of PGA, such as solubility and appearance, copolymerization of trioxane, CO, and a minor amount of epoxides derived from polyethylene glycol (PEG) were performed under the same reaction conditions for PGA synthesis (in DCM, at 800 psi CO pressure, with triflic acid catalyst, reaction duration of 72 hours). The results have shown that the addition of minor quantities of epoxide comonomers vastly improves the appearance of the obtained PGA copolymers and allows for the control of the polymeric properties, such as solubility and melting temperature.     

Fortran IV programs for the penultimate copolymerization model

Three programs have been written for calculations involving use of the penultimate copolymerization model. The first computes the penultimate reactivity ratios from composition-conversion data, without constraints, at any conversion. A nonlinear leastsquares technique using Marquardt's algorithm is employed. The second program computes the four optimum starting monomer feed ratios, M₁⁰/M₂⁰ which should be used by the experimenter from the penultimate reactivity ratios. These optimum feed ratios are obtained by choosing the conditions necessary to minimize the determinant of the variance-covariance matrix. The input for the first program includes estimates of known values of the penultimate reactivity ratios. By using these two programs sequentially the experimenter has an optimized experimental approach toward evaluating penultimate reactivity ratios at any conversion. Finally, a program has been provided to calculate composition–conversion data, given penultimate reactivity ratios.     

Development and Modeling of a Continuous Dispersion Copolymerization Process in the Presence of a Stabilizing Agent Elaborated in situ

Summary: This work deals with the development of a process for the radical copolymerization of acrylonitrile and styrene in a dispersed medium. This process was carried out in a continuous stirred tank reactor, in the presence of a stabilizing agent produced in situ during the polymerization. The continuous phase is a polyol. Besides all elementary chemical mechanisms related to the copolymerization and to the synthesis and grafting of the stabilizing agent, this process involves several complex physical phenomena. A tendency model of the whole process was developed, using the corresponding mass balances and thermodynamics. Its unknown parameters were identified by use of an evolutionary algorithm and experimental data resulting from an adapted experimental strategy. This model was then validated and allowed to predict monomers and transfer agent conversions, amounts of solids and average molar masses, versus the operating conditions.