Copolymerization Reactivity Ratios Research Articles

Modelling and simulation of emulsion copolymerization of monomers of different polarities ‐ relationship polymerization process ‐ microstucture ‐ properties

AbstractAccurate kinetic investigations of emulsion copolymerization of monomers of different polarity have allowed to derive reliable mechanisms which appeared to be more complex than usually expected: polymerization in the water phase seems quite general; the solid content ‐ i.e. monomer/water ratio ‐ or, even the pH(when copolymerizing ionogenic monomers) modify the reactivity ratios in emulsion copolymerization; monomer partition is an upmost parameter. However, it is believed that what may be the monomers and the polymerization process, it is possible to model emulsion copolymerization and to develop simulation softwares. These computer simulations then allow to quantitatively compare theoretical behaviour with experimental data and to improve our knowledge of emulsion process. Furthermore, these programs give the sequence distribution of emulsion copolymers and can predict some important properties like the glass transition, which is closely related to copolymer microstructure and hetero‐geneity. Modelling and simulation have been applied to a lot of emulsion copolymerizations and terpolymerizations of various monomers, including some functional monomers.

Analysis of the linear methods for determining copolymerization reactivity ratios, VIII. A critical reexamination of radical copolymerization of methylmethacrylate or styrene

AbstractThe reactivity ratios of selected methylmethacrylate or styrene copolymerisation systems have been reviewed in terms of the extended Kelen‐Tüdős method. r‐values, together with their 95% confidence limits have been calculated. Quantities δ and Q, suitable for classification of the systems, have been applied. Of the 71 reevaluated methylmethacrylate systems 40 (56.3%) were found to belong to class I and 20 (28.2%) to class I(!), i. e. 60 (84.5%) systems for which the conventional copolymerisation equation was found to be adequate. For 3 (4.2%) systems belonging to class II the two‐parameter model does not hold and 8 (11.3%) systems were related to class III, i. e. systems for which the experimental data are inconsistent and the published r‐values meaningless. 32 styrene copolymerisation systems were reevaluated with the following classification: 19 (59.4%) systems in class I, 5 (15.6%) systems in class I(!), 2 systems in class II and 6 (18.8%) in class III.

Synthesis and characterization of glycidyl methacrylate-styrene copolymers and determination of monomer reactivity ratios

Copolymers of glycidyl methacrylate (GMA) and styrene were prepared in the presence of 2,2'-azobisisobutyronitrile in chlorobenzene. The polymers were characterized by infra-red and 13C nuclear magnetic resonance spectroscopy. The percentage of GMA present in the copolymers was established by elemental analysis. The copolymerization reactivity ratios were calculated using the Kelen—Tudos method. Molecular weights, glass transition temperatures and thermal properties were determined by gel permeation chromatography, differential scanning calorimetry and thermogravimetric analysis, respectively.

Preparation of a thermally phase‐separating copolymer, poly(N‐isopropylacrylamide‐co‐N‐acryloxysuccinimide), with a controlled number of active esters per polymer chain

AbstractN‐isopropylacrylamide and N‐acryloxysuccinimide have been copolymerized in various mixtures of terrahydrofuran and toluene using azobisisobutyronitrile as initiator. Polymerization has been conducted for 24 h at 50°C under a slightly positive pressure of nitrogen. The copolymers were assayed for active ester content by measuring the UV absorbance (259 nm) of N‐hydroxysuccinimide anion, generated by reacting the copolymers with N‐isopropylamine in dimethylformamide and dissolving the resulting mixture in 0.1M HEPES buffer, pH 7.5. The molecular weight and its distribution have been estimated by gel permeation chromatography. The active ester content was found to be equivalent to the comonomer feed ratio, and the major factor controlling the molecular weight was the ratio of tetrahydrofuran to toluene. Thus, the number of active esters per polymer chain could be controlled by adjustment of the comonomer feed ratio and the ratio of tetrahydrofuran to toluene. Monomer reactivity ratios for copolymerization of N‐isopropylacrylamide with N‐acryloxysuccinimide were also estimated. These copolymers are useful for immobilizing binding ligands such as antibodies for subsequent thermally induced precipitation immunoassays and bioseparation processes.

Direct polar conjugation in radical copolymerization of styrene with substituted styrenes

The electronic effects of substitutents on the values of monomer reactivity ratios in copolymerization of styrene with substituted styrenes have been isolated. The most important proved to be the direct polar conjugation of the substitutent with the nucleophilic reaction centre. A two-parameter correlation equation has been proposed which describes satisfactorily the experimentally determined reactivity of comonomers. The values of monomer reactivity ratios have been determined for copolymerization of styrene with para and meta-substituted aminostyrenes.

Heat resistant styrene/α‐methylstyrene copolymers made via continuous anionic polymerization at high temperature

AbstractStyrene/α‐methylstyrene (SAMS) copolymers were produced containing up to 67 weight % AMS. The polymerizations were carried out using anionic polymerization at high temperature (100°C) in a CSTR type reactor. The reactivity ratios for the anionic copolymerization of styrene (M1) and AMS (M2) were estimated to be r1 = 60 and r2 = 0.01. Thermal degradation of a SAMS copolymer containing 50 weight % AMS was studied and compared with free radical polystyrene (FRPS) and anionic polystyrene (APS). The relative rate of styrene monomer generation for the three polymers followed the order SAMS > FRPS > APS. The relative rate of loss of molecular weight for the three polymers was FRPS > APS > SAMS. This indicates that the main mechanism of thermal degradation of SAMS copolymers is depolymerization rather than chain scission.

Comments on the Kuo‐Chen method to determine monomer reactivity ratios in copolymerization

Comments on the Kuo‐Chen method to determine monomer reactivity ratios in copolymerization

Copolymerization of acrylamide with cationic monomers in solution and inverse‐microsuspension

AbstractThe free radical copolymerization of acrylamide with three of the most commonly used cationic comonomers diallyldimethylammonium chloride, dimethylaminoethylmethacrylate, and dimethylaminoethylacrylate, the latter two quaternized with methyl chloride, was investigated. The polymerizations were carried out with azocyanovaleric acid and potassium persulfate over the temperature range 45–60°C. The copolymer reactivity ratios were determined with the error‐in‐variables method using residual monomer concentrations, measured by a Nalco HPLC method. This combination of estimation procedure and analytical technique has been found to be superior to any methods used previously for the estimation of reactivity ratios for cationic‐acrylamide copolymers.

Influence of solvents on apparent reactivity ratios in the free radical copolymerization of polar monomers

The influence of solvents on the composition of the resulting copolymers is investigated using the following monomer pairs: acrylic acid-methyl acrylate; acrylic acid-acrylonitrile; acrylic acid-acrylamide; acrylonitrile-acrylamide and acrylic acid-methacrylic acid. It is found that copolymer compositions may either vary drastically with the nature of the solvent (copolymerization of acrylamide with acrylic acid or with acrylonitrile) or be slightly affected only. It is shown, in the case of acrylic acid, that a solvent mixture which enhances the “matrix effect” in the homopolymerization of this monomer also favors its introduction in the copolymer (with methyl acrylate). The apparent reactivity ratios are particularly sensitive to solvents in copolymerizations involving acrylamide, but no simple correlation could be established between the values of the reactivity ratios and the manner in which the solvents may affect the equilibria between the various molecular associations present in the system. If the copolymer is insoluble in the reaction medium, the resulting precipitation may or may not influence the apparent reactivity ratios depending on the system under investigation.

Determination of reactivity ratios from analysis of triad fractions—analysis of the copolymerization of styrene and acrylonitrile as evidence for the penultimate model

A numerical analysis of the relationship between the composition of the monomer feed and that for the resultant copolymer (at low conversion) is the method usually adopted for determination of copolymerization reactivity ratios. However, the six triad fractions provide much more information about a copolymer than does the single copolymer composition. In most of the cases where both sets of information can be reliably obtained, the copolymer composition can be determined with slightly greater experimental accuracy than the triad fractions. Despite the somewhat lower accuracy of the individual triad fractions, in some cases the “best” model of the copolymerization and the corresponding reactivity ratios can be determined with higher precision from the triad fractions, because of the extra information provided by these data. A direct numerical analysis of the triad fractions for the styrene-acrylonitrile copolymerization in terms of the penultimate model has yielded the reactivity ratios and their joint confidence regions for the bulk polymerization at 60°. The analysis shows that the data can be satisfactorily described by the penultimate model, whereas statistical tests demonstrate that the terminal model will not adequately represent the polymerization. The reactivity ratios are determined with higher precision from the triad fractions than from the copolymer compositions.

An easy calculation of the expected n‐ad sequence proportions in polymers obeying first‐order markov statistics and being prepared by ring‐opening polymerization of chiral heterocyclic monomers

AbstractAn easy and fast calculation method of the normalized n‐ad sequence proportions in optically active polymers which derive from heterocyclic monomers and which obey first‐order Markov statistics is developed. The proposed method does not require any computer calculation and provides very accurate values up to high conversions in polymer. It can be applied over a wide range of enantiomeric excess of the initial monomer, and of copolymerization reactivity ratios. This is useful for testing whether a polymer fits the first‐order Markov propagation model.

Copolymerization reactivities, electron structure and nuclear magnetic resonance spectra of vinylazoles

AbstractData obtained on the electronic structure of a series of C‐ and N‐vinylazoles using the SCF MO method in MNDO approximation and analysis of the 13C and 1H NMR data as well as their copolymerization reactivity ratios in the copolymerization with styrene have shown individual correlations between the relative activity 1/r (r is the copolymerization reactivity ratio of styrene) and the chemical shifts of the terminal vinyl carbon atoms in 13 C NMR spectra, between 1/r and chemical shifts of the protons in trans‐position towards the substituent in 1H NMR spectra, and between 1/r and the net effective charges on the terminal vinyl carbon atoms for each type of monomers considered. The correlations obtained and the analyses obtained from the monomers studied within the modified Alfrey‐Price scheme indicate that the reactivity of vinylazoles in copolymerization is mainly influenced by two factors: the acceptor inductive effect of a substituent in the vinyl bond and the conjugation effect. These factors operate in a different manner for C‐ and N‐vinylazoles and determine their different reactivity in radical copolymerization with styrene.

Polymerization and copolymerization of β-butyrolactone by aluminium compounds

Contrary to previous reports, mixed aluminium-zinc oxo-alkoxides ZnAl 2O 2(OC-HMe 2) 4 initiate the polymerization of β-butyrolactone to the biodegradable polyester poly(β-hydroxybutyrate). The polymerization is very much slower than that of β-propiolactone, produces low molecular weight products, and does not have living kinetics. There is evidence for catalyst deactivation during the reaction, and the polymer is completely atactic. Copolymerizations with unsubstituted lactones are initiated by the oxo-alkoxide, by aluminium 2-propoxide and by ( meso-tetraphenylporphinato)aluminium chloride. In all cases, the co-monomer dramatically reduces the rate of polymerization and the melting point of the product. Reactivity ratios for copolymerization where M 1 is ϵ-caprolactone have been determined to be r 1 = 13± 0.5 and r 2 = 0.4 ± 0.04. For the copolymerization with δ-valeroactone, the corresponding values are r 1 = 7.4 ± 0.5 and r 2 = 0.15 ± 0.04. These values imply that the copolymers contain only isolated units or short blocks of the β-lactone.

Copolymerization of N‐vinyl‐2‐pyrrolidone and 2‐phenyl‐1,1‐dicyanoethene

AbstractRadical copolymerization of N‐vinyl‐2‐pyrrolidone (NVP) with 2‐phenyl‐1,1‐dicyanoethene (PDE) was studied in benzene at 70°C. Terminal, penultimate, and monomer complex participation kinetic models were applied to compositional data for best prediction of the copolymer composition. Both penultimate and complex models described satisfactorily the deviation from the terminal copolymerization model, although the complex model did not predict as well as the penultimate model at high NVP/PDE monomer feed ratios. Copolymerization reactivity ratios rNVP = 0.08 and r′NVP = 1.8 indicated substantial effect of the penultimate PDE monomer unit associated with polar repulsion of cyano groups. Equilibrium constant of NVP‐PDE comonomer complex formation was found to be 0.08 L/mol as estimated by proton nuclear magnetic resonance (NMR) analysis of PDE's vinylic proton chemical shift upon complexation. Rate constants of propagation reactions were estimated by applying terminal complex copolymerization model.

Determination of reactivity ratios in copolymerization

AbstractFree radical copolymerization of two monomers is usually described in terms of reactivity ratios, only two of which are needed for the simplest (Mayo‐Lewis) model. Other, more complex models (such as penultimate unit effects or complex formation) require more kinetic parameters for a complete description. Published summaries of reactivity ratios list values for about 700 monomers taken from more than 1400 publications. These values represent an enormous amount of descriptive and physico‐chemical information about copolymerization in particular and free radical reactivity in general. It is important that we understand the limits to the numerical correctness of existing data, and that future data gathering be done in a statistically correct manner. In this paper several different linear and non‐linear regression approaches to estimating reactivity ratios are reviewed with emphasis being placed on the Mayo‐Lewis model. Two separate problems are recognized: the first is that of model discrimination, the second that of parameter estimation. It is rare that both problems can be properly treated with a single set of experiments, and we discuss the experimental approaches needed to obtain statistically good results.

Composition effect of highly active supported Ziegler catalysts for ethylene copolymerization with α-olefins

Comonomer reactivity ratios for ethylene copolymerization with propylene, butene-1 and hexene-1 over new high activity supported Ziegler catalysts and TiCl3 have been determined. It has been established that copolymerization reactivity of the catalysts decreases in the sequence: VCl4/MgCl2>δTiCl3 · 0.3 AlCl3>TiCl4/MgCl2. Copolymer density is practically independent of catalyst composition and controlled by the concentration and type of α-olefins. The catalysts examined are more active in copolymerization than in the homopolymerization of ethylene.

Polymerizable tautomers, 4. Solvent effects in radical copolymerization of ethyl 3‐oxo‐4‐pentenoate and styrene

AbstractEthyl 3‐oxo‐4‐pentenoate (1) exhibits the coexistence of two tautomers, the ketonic and enolic form, and its tautomeric equilibrium shifts with the solvent. The monomer reactivity ratios for the radical copolymerization of 1 (M1) and styrene (M2) in various solvents were determined. There is a marked and a minor solvent effect on r1 and r2, respectively. Regression analysis of r1 with the solvatochromic parameters yields a fairly good linear relationship, taking into account three factors: polarity and hydrogen bond donating and accepting powers of the solvents.

A method for determining reactivity ratios in copolymerizations in the presence of a ceiling temperature effect

A novel kinetic treatment is proposed for the copolymerization of two monomers, M 1 and M 2, when M 2 has a low ceiling temperature. In the mechanism used, the growing copolymer with a terminal −M 2M 2· can undergo depropagation to −M 2· and M 2. If [M 1] ⪢ [M 2], as is possible experimentally when M 2 is radioactively labelled, a value of the reactivity ratio r 1 which is independent of the ceiling temperature effect can be obtained. This value is then used to obtain a value of the reactivity ratio r 2 which is also independent of the ceiling temperature effect. The derivation is valid provided that r 2 is small, which is often the case when M 2 has a low ceiling temperature. The method involves solution for r 2 by means of intersecting parabolas, each one representing a given monomer feed ratio and copolymer composition ratio.

Synthesis and Characterization of Non-Fouling Polymer Surfaces: I. Radiation Grafting of Hydroxyethyl Methacrylate and Polyethylene Glycol Methacrylate onto Silastic Film

Polyethylene glycol (PEG) surfaces have been shown to be resistant to fouling by adsorbed proteins and cells. We have studied radiation induced graft copoly merization of hydroxyethyl methacrylate (HEMA) monomer and different molecular weight polyethylene glycol methacrylate (PEGMA) and methoxy PEGMA (MPEGMA) macromers onto Silastic film. The extent of grafting and chemical composition of the graft were found to be dependent on the HEMA/PEGMA ratio and the molecular weight of PEGMA. The influence of PEGMA molecular weight on grafting is explained in terms of both steric hin drance of PEG chains and the effect of radiation on the pendant polyether chains. Furthermore, the reactivity ratios in conventional copolymerizations initiated by y-ray or chemical initiators have been evaluated and compared with grafting reactivity ratios. The formation of interpenetrating chains was verified through microscopic observation of the cross section of the grafted film.

Polymérisation radicalaire du pentadiène‐1,3. I. Copolymérisation des cis et trans pentadiènes‐1,3 avec l'acrylonitrile. Détermination des rapports de réactivité

AbstractCis (CP) and trans (TP) isomers of 1,3‐pentadiene (piperylene) were homo and copolymerized with acrylonitrile (A) in bulk and emulsion, at 50°C, using azobisisobutyronitrile and potassium persulfate as free radical initiators. The cis isomer reacts more rapidly than the trans monomer. The copolymer compositions were determined from nitrogen analysis, 100‐MHz 1H‐NMR and 25‐MHz 13C‐NMR spectra. The results thus obtained show that both the bulk and emulsion processes yield copolymers characterized by a very similar composition. Data plotted according to the Kelen‐Tüdös method indicate that the terminal‐unit model is applicable to the piperylene‐acrylonitrile system. Reactivity ratios for bulk copolymerization were as follows: rA = 0.079, rTP = 0.114, and rA = 0.033, rCP = 0.188. These values are very small and hence suggest a strong alternating tendency for acrylonitrile and 1,3‐pentadiene in both comonomer systems. This latter conclusion is corroborated by the comparison of the NMR spectra of the synthesized copolymers with that of a standard alternating sample. The reactivity (Q) and electronegativity (e) of the 1,3‐pentadiene isomers calculated from the reactivity ratios by the Alfrey—Price equations were QTP = 0.56, eTP = −0.97 and QCP = 1.215, eCP = −1.055 for trans and cis dienes, respectively.