Studies on monomer reactivity ratios. II. A charge-transfer model

A charge-transfer model is proposed for the treatment of monomer reactivity ratios in free-radical bulk polymerization. The procedure involves the assignment of three parameters to each monomer, which can be interpreted as being related to the energies of the highest occupied monomer orbital, the singly occupied radical orbital, and the lowest lying virtual orbital of the monomer. Parameters are found for 17 monomers and computed reactivity ratios for a large number of copolymer systems are tabulated and compared with experiment. Similarities of the present model and the electronegativity scheme are discussed.     

Studies on monomer reactivity ratios. III. Comparison of various mathematical models

Seven mathematical models for the treatment of monomer reactivity ratios in free-radical copolymerization are compared from the viewpoint of their relative simplicity, accuracy, and the number of parameters necessary for their use. It is concluded that the electronegativity and charge-transfer models proposed in previous papers represent the best compromise for routine usage if quantitative accuracy is the primary concern.     

Effect of Substituents on the Copolymerization Parameters of Some Phenolic Monomers

Copolymerization parameters of some halogen substituted phenolic monomers have been determined by the linear graphical method of Kelen and Tüdös. The order of reactivity of p-chlorophenol, p-bromophenol and p-iodophenol is found to be the reverse of the order of electronegativity of their halogen substituents when they are copolymerized with p-hydroxy-benzoic acid. On copolymerization with p-cresol, these halogen substituted phenols have reactivity in the same order as the electronegativity of their substituents. This reversal of reactivity of phenolic monomers has been interpreted in terms of (1) opposite polarization caused by electrophilic or nucleophilic substituents present in the common monomers, and (2) the magnitude of their resonance stabilization.

The copolymerization parameters r₁ and r₂ are universally used for the characterization of monomer pairs with regard to their behavior in copolymerization. The classic copolymer equation describes the composition of the copolymer as a function of the reactivity ratios and the composition of the monomer feed. Several authors have used linear [1], nonlinear [2–6], specific coper composition equations [7], and computer programming routines [8] for calculating copolymerization parameters r_l and r₂. Kelen and Tödös [9] have recently.     

Polymerizable Tautomers. VII. Radical Copolymerization of Ethyl 3-oxo-4-Pentenoate and Ethyl 4-Methyl-3-oxo-4-Pentenoate with Methyl Methacrylate

Abstract

Ethyl 3-oxo-4-pentenoate (EAA) and ethyl 4-methyl-3-oxo-4-pentenoate (EMAA) exhibit the coexistence of the ketonic and enolic forms in most organic solvents. Radical copolymerizations of EAA and EMAA with methyl methacrylate (MMA) were carried out at 60 °C in various solvents, and monomer reactivity ratios were estimated. There are minor solvent effects on monomer reactivity ratios r_MMA in both EAA/MAA and EM A A/MM A systems. On the other hand, r_EAA and r_MMA values greatly change with the solvent: The values decrease with an increase in the ketonic fraction of the polymerizable tautomers (EAA and EMAA). Regression analysis of the monomer reactivity ratios with the solvatochromic parameters reveals that polarity of the solvent is the major factor governing the relative reactivity.     

Model prediction of batch emulsion copolymerization as a function of conversion: A sensitivity analysis

Recently a model has been developed capable of predicting absolute monomer concentrations and their ratios in the polymer, aqueous, and monomer droplet phases as a function of conversion in batch emulsion copolymerizations without using any adjustable parameters. In this article the sensitivity of model predictions of composition drift toward deviations of 10% in all model parameters (maximum swellabilities of monomer in the polymer phase, water solubilities, reactivity ratios, and monomer and polymer densities) was estimated using the monomer combination methyl methacrylate-styrene as an example. From the sensitivity analysis it can be concluded that the reactivity ratios are the most important parameters affecting composition drift. The effects of deviations in maximum swellabilities and monomer and polymer densities on composition drift can be neglected, while the water solubility is important only in those cases where the amount of monomer in the aqueous phase cannot be neglected as compared with the total monomer amount. © 1994 John Wiley & Sons, Inc.     

Estimation of Reactivity Ratios from Multicomponent Copolymerizations

Abstract

The composition of the copolymer formed from n monomers in addition polymerization can be expressed in terms of the monomer feed composition and n(n - 1) binary reactivity ratios, according to the familiar simple copolymer model. Reactivity ratios are determined experimentally from cor-responding feed and monomer compositions in binary co-polymerizations. This article reports methods for deriving such reactivity ratios directly from multicomponent polymerization data. Analytical solution of the multi-component copolymer equations is not feasible because of the limited number of experimental points and experimental uncertainty in the copolymer composition. Computer-assisted procedures have been developed to estimate re-activity rates by optimizing the fit of predicted and experimental copolymer compositions, given the monomer feed composition and preliminary values of the reactivity ratios. All n(n - 1) reactivity ratios are adjustable. The methods are demonstrated for styrene/methacrylonitrile/ a-methylstyrene, butadiene/styrene/2-methyl- 5-vinyl- pyridine and acrylonitrile/methyl methacrylate/& methylstyrene systems. Binary reactivity ratios predict ternary copolymer compositions generally well in these cues. Reasons are suggested why reactivity ratios from multicomponent experiments may not match the corresponding parameters from binary copolymerizations.     

The effect of water solubility of the monomers on composition drift on methyl acrylate-vinyl ester combinations

It has been shown theoretically that composition drift mainly depends on reactivity ratios and water solubilities. Minimum composition drift can be obtained by lowering the monomer-to-water ratio in monomer systems where the more reactive monomer is also the more water-soluble one. Investigating the effect of water solubility on composition drift while keeping the reactivity ratios constant can elucidate the importance of the water solubility. The monomer combinations methyl acrylate-vinyl acetate (MA-VAc), methyl acrylate-vinyl 2,2-dimethylpropanoate (MA-VPV), and methyl acrylate-vinyl 2-ethylhexanoate (MA-V2EH) are ideal monomer combinations for studying the effect of water solubility on composition drift since the reactivity ratios for this series of monomer systems are approximately equal. Solution copolymerizations are performed to elucidate maximum composition drift at extremely high monomer-to-water ratios. From comparing theoretical predictions with experimental results it could be concluded that composition drift for the monomer combination MA-VAc could only be reduced since the difference in water solubility was not large enough to compensate the effects of the large difference in reactivity ratios. However, for the monomer combinations MA-VPV and MA-V2EH the difference in water solubility was large enough to make minimum composition drift possible for low monomer-to-water ratios even for monomer combinations with reactivity ratios as far apart as in the MA-vinyl ester case. © 1996 John Wiley & Sons, Inc.     

Alternating copolymerization of polar vinyl monomers in the presence of zinc chloride. I. Propagation and initiation of the copolymerization of acrylonitrile with styrene copolymer

Copolymerization of acrylonitrile with styrene spontaneously occurred on addition of zinc chloride without addition of any other radical initiator. The composition of the copolymer approached that of strictly alternating copolymer as zinc chloride added to the copolymerization system increased. The significance of the apparent monomer reactivity ratios of this copolymerization system was studied from a kinetic point of view, and it was shown that the monomer sequence distribution is indicated by the apparent monomer reactivity ratios. Further, equations which represent the relation between the apparent monomer reactivity ratios and Q,e values at a given salt concentration were derived. These equations reasonably accounted for the decrease of the apparent monomer reactivity ratios of the copolymerization of acrylonitrile with styrene in the presence of zinc chloride and the behavior of the other acrylonitrile copolymerization systems in the presence of zinc chloride. The initiation step of the spontaneous radical copolymerization of acrylonitrile with styrene in the presence of zinc chloride was explained by a cross-initiation mechanism.     

Nonlinear regression by visualization of the sum of residual space applied to the integrated copolymerization equation with errors in all variables. I. Introduction of the model,simulations and design of experiments

A new model for estimating reactivity ratios using the integrated copolymerization equation is presented. The model is a general nonlinear least squares method taking the error in both monomer conversion and monomer fraction into account by a relation between these two variables. Simulations show that the model is able to predict reactivity ratios successfully. Special attention is given to experimental design, i.e., at which initial monomer feed ratios the experiments should be performed in order to obtain reliable values for the reactivity ratios. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3793–3803, 1999     

HEMA—NVP—St三元共聚体系中单体的表观竞聚率

本文采用计算机数字积分和单纯形调优法根据Alfrey-Goldfinger共聚方程微分式,从HEMA-NVP—St三元共聚高转化率体系的转化率一组成数据,直接求算了各单体的表观竞聚率,用求得的表观竞聚率计算的转化率一组成曲线,与实验值符合很好。讨论了单体部分互溶对表观竞聚率的影响。发现在此三元共聚体系中,引入少量的均化剂,可以明显改善St与其它单体的互溶程度,使相应的表观竞聚率显著降低。     

Copolymerization of a dendronized monomer with styrene and different acrylates: Determination of reactivity ratios

The reactivity ratios for the copolymerization of a first‐generation dendronized monomer with styrene and different acrylates are determined. The obtained ratios as well as the copolymer compositions that can be expected are discussed in detail. The influence of the dendron on the polymerization potential of the monomer is estimated by comparing its reactivity to those of linear systems as well as using higher generations of the dendronized monomer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Microstructure of ethylene–vinyl chloride copolymers. I. Direct verification of terminal radical effects on copolymerization by a simplified NMR approach

The sequence distributions of monomer units in a series of high-pressure, bulk ethylene–vinyl chloride copolymers have been determined by high-resolution NMR spectroscopy. The concentrations of EE, VV, and EV (VE) monomer pairs or diads were used with NMR-determined compositions to calculate, in addition to the sequence distribution parameters, the reactivity ratio product for the system. Inclusion of feed data allowed the calculation of individual reactivity ratios. Well within experimental error, the reactivity ratio product (r₁r₂ = 0.7) determined from microstructure analysis—independent of monomer feed data—was equal to that determined by the standard Fineman-Ross technique. Terminal monomer unit effects on the copolymerization were observed. The nonrandom structures result from a copolymerization described by first-order Markoffian statistics.     

Studies on propagating species in cationic polymerization of styrene derivatives by acetyl perchlorate or iodine. III. Effect of salt on cationic copolymerization of styrene derivatives with vinyl ethers by acetyl perchlorate

A common-ion salt, tetra-n-butylammonium perchlorate, was found to affect the monomer reactivity ratios in the cationic copolymerization by acetyl perchlorate of styrene with p-methylstyrene and of 2-chloroethyl vinyl ether with p-methylstyrene, but not those for the copolymerization of 2-chloroethyl vinyl ether with isobutyl vinyl ether. In the copolymerization of p-methylstyrene with styrene or with 2-chloroethyl vinyl ether, the addition of the common-ion salt in a polar solvent shifted the monomer reactivity ratios to those in a less polar solvent. The molecular weight distribution analysis of the copolymer suggested that the addition of the common-ion salt depresses the dissociation of propagating species. Therefore, it was concluded that a propagating species with a different degree of dissociation shows a different relative reactivity towards two monomers. The nature of propagating species was also discussed on the basis of the common-ion effect on the monomer reactivity ratios in various solvents.     

Fundamental Aspects of Measuring Copolymerization Reactivity Ratios Using Real-Time FTIR Monitoring

Real-time FTIR is a powerful tool to obtain copolymerization reactivity ratios because it allows simultaneous monitoring of individual monomer consumption rates. Based on the Mayo-Lewis equation we showed that in reactivity ratios can be defined as the ratios of apparent rate constants of monomer consumption. The validity and limitations on this new method are discussed in the isobutylene-isoprene and isobutylene-styrene carbocationic copolymerization systems.     

Emulsion polymerization. VI. Concentration of monomers in latex particles

Nonpolymerizing latex particles surrounded by an aqueous phase saturated with monomer absorb only a finite amount of monomer, even if the monomer is a good solvent for the polymer, because the surface energy of each particle increases on swelling. At equilibrium the change in surface energy and the free energy of mixing exactly balance. Equations based on this thermodynamic principle predict with good accuracy the saturation swelling of crosslinked and uncrosslinked latex particles and the partitioning of monomer between the aqueous phase and latex particles at partial saturation. The available experimental data on swelling of latex polymers with monomers are reviewed. Earlier papers assumed that during emulsion polymerization the monomer concentration in the latex particles is independent of conversion as long as monomer droplets are present. This assumption is shown to be a justifiable approximation. The thermodynamics of the swelling of latex particles with a blend of two monomers is presented. The calculations indicate that copolymerization in emulsion should define reactivity ratios differing from those of homogeneous copolymerization by not more than 40% if the solubility of the comonomers in water is low. The reactivity ratio scheme is strictly applicable to emulsion copolymerization if the solvent properties of the two comonomers are identical.     

Terminal and Penultimate Reactivity Ratios in the Styrene-Acrylonitrile Free-Radical Copolymerization System in Bulk

ABSTRACT

The terminal and penultimate model reactivity ratios for the styrene-acrylonitrile monomer system in bulk have been investigated by the simplex and scanning method. It has been shown that Mayo-Lewis equation has an unique solution when determining the reactivity ratios according to the terminal model while for the penultimate model the non-uniqueness in determination of the reactivity ratios has been found. The numerical values of the penultimate r-parameters calculated with the simplex method depend on the initial guess for r-parameters.

Several sets of penultimate reactivity ratios for the styrene-acrylonitrile system in bulk have been found to be equal from mathematical point of view. The reactivity ratios with comparable standard deviation have an equivalent graphical representation on the copolymerization diagragm. It has been also confirmed that the penultimate model is a more appropriate of the models considered to describe the variation of the copolymer composition with the monomer feed. Taking into account previous results for the styrene-methyl methacrylate system in bulk it is thereby assumed that the occurrence non-uniqueness in determination of the penultimate model reactivity ratios does not depend on the monomer system.     

全氟甲基乙烯基醚和其它含氟单体乳液共聚合的竞聚率测定

分别通过气相色谱法测定了全氟甲基乙烯基醚 (PMVE)与偏氟乙烯 (VDF)以及PMVE与四氟乙烯(TFE)二元乳液共聚反应中的气相单体组成和共聚物组成 ,然后用非线性回归法 (RREVM )计算得TFE PMVE及VDF PMVE乳液共聚合反应的表观竞聚率分别为γTFE =3 89和γPMVE =0 0 5以及γVDF =1 0 6和γPMVE =0 11.结合已经测定的TFE VDF二元乳液共聚的表观竞聚率 ,计算了由VDF TFE PMVE三元乳液共聚合反应合成的共聚物组成 ,后者与由1 9F NMR实测的共聚物组成吻合     

Copolymerization at high conversion when the concentration of one monomer does not change

Exact equations and several computer programs were developed for use in studies on copolymerizations carried to high conversion when the concentration of one of the monomers (A) remains constant. Simple ACSL® and DESIRE® programs are described for simulating such copolymerizations, and their output was used to test programs and procedures that were developed to evaluate monomer reactivity ratios for such copolymerization systems. Based on an integrated form of the copolymer equation, Excel® and Fortran programs were developed for evaluating monomer reactivity ratios from information about initial monomer compositions, copolymer compositions, and the fractions of the second monomer (B) that reacted. A graphical procedure for evaluating monomer reactivity ratios from such data was also developed. A previous program developed for calculating information about monomer sequence distributions in copolymers was modified so that it would apply to copolymerization at high conversion when the concentration of one monomer remains constant. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1118–1128, 2000     

氯乙烯/N-取代马来酰亚胺共聚竞聚率及共聚物组成

研究了氯乙烯(VC)与多种N-取代马来酰亚胺的溶液共聚合,求得各对单体的竞聚率.结果表明,各种马来酰亚胺的竞聚率都远高于VC的竞聚率,即N-取代马来酰亚胺单体的活性均比VC单体活性高.计算得到N-取代马来酰亚胺Q和e值.由于苯环的共轭效应,N-苯基及N-取代苯基马来酰亚胺具有较大的Q值.各对单体的e值差别较大,表明有形成交替共聚物的倾向.此外,还考察了聚合过程中共聚物组成的变化,用递推法预测了这类体系共聚物瞬时和累积组成随转化率的变化.     

Measurement of Monomer Reactivity Ratios of D,L-3-Methylglycolide with Glycolide or D,L-Lactide

Polylactides, polyglycolide and copolymers based on them, are still gaining interestbecause of the numerous applications in the biomedical and pharmaceutical fieldsl. Theyare usually prepared by bulk homo- and co-polymerizations of lactides, glycolideinitiated with stannous octoate (Snoot,) because Snoot, is a highly efficient commercialcatalyst and a permitted food additive in numerous countriesl-2. However, the propertiesof poly(D,L-lactic acid-co-glycolic acid) (D,L-PLGA) have widely va…