Ionic Graft Research Articles

Mechanism of radiational ionic graft polymerization

1. A discussion is given of the mechanism of initiation of radiational ionic graft polymerization, and the growth of the graft chains in the polymeric matrices. 2. The effect of the solvent on the rate of ionic graft polymerization is largely determined by ion solvation. 3. The graft polymerization rate is a maximum at the principal relaxation transition point (the glass point) of the swollen polymer. 4. Radiational graft polymerization involves both radical and ionic processes. An equation relating the contribution of the ionic process to the polymerization, the dose rate, and the concentration of inhibiting contaminants in the system (H2O) is derived and analyzed. 5. It is shown that the contribution from the ionic process increases with a rise in the dose rate. In the radiational graft copolymerization of styrene with acrylonitrile, the effect of the ionic process becomes appreciable at a dose rate of 103 Gy/sec.

Ionic Graft Polymerization onto Fibers and Its Related Compounds

Ionic Graft Polymerization onto Fibers and Its Related Compounds

Effect of sovents on radiation‐induced ionic graft polymerization

AbstractThe influence of various solvents on radiation‐induced cationic (grafting of vinyl‐n‐butyl ether onto polyethylene) and anionic (grafting of 2‐methyl‐5‐vinylpyridine onto polyethylene) graft polymerization was studied. This ionic grafting was performed in thoroughly dried systems at room temperature. It was established that electron‐acceptor solvents promote cationic grafting but that electron‐donor solvents promote the anionic. A clear correlation between the donor number of solvents and grafting value by the anionic mechanism was shown. There was no correlation between dielectric constants and grafting values. The reaction orders, according to monomer concentration by 2‐methyl‐5‐vinylpyridine grafting in various solvents, were equal to approximately 1.5 and 2 for the radical and anionic mechanisms, respectively. The effect of solvents on radiation‐induced ionic graft polymerization is discussed. The results of this study indicate the correct choice of solvents for radiation‐induced ionic grafting.

Radiation-Induced Ionic Grafting of Ethyl Vinyl Ether to Polypropylene Film

Abstract The radiation-induced grafting of ethyl vinyl ether to polypropylene film in bulk has been investigated under super-dry conditions. The per cent grafting increased linearly with increasing dose without an induction period. The grafting did not take place in the presence of traces of water, indicating that the grafting proceeds by an ionic mechanism. The dose-rate dependence of the rate of grafting was found to be 0.25. The grafting was also examined in n-pentane and neopentane solutions. Although the per cent grafting in the solution system was lower than that in the bulk system, n-pentane was found to increase the grafting efficiency.

Kinetics of diffusion‐free radiation graft polymerization of styrene onto polyethylene

AbstractThe diffusion‐free radiation graft polymerization of styrene onto polyethylene has been studied. The grafting rate shows a dependence on monomer which is far different than what has been assumed. Further, the dependence on monomer changes with increasing dose rate as does the dependence of grafting rate on radiation dose rate. Three different regions of behavior are defined: (1) a region of low dose rate where the grafting rate is 1/2‐order in dose rate and 3/2‐order in monomer; (2) a region of intermediate dose rate where the grafting rate is intermediate between 1/2‐and zero‐order in dose rate and 5/2‐order in monomer; and (3) a region of high dose rate, where the grafting rate is independent of dose rate and at least 5/2‐order in monomer. Various possible mechanisms responsible for these effects are discussed, including the effects of viscosity on the initiation and termination reactions, the possibility of ionic graft polymerization, and energy transfer.

Monomer exponent in radiation graft polymerization

The diffusion-free radiation graft polymerization of styrene onto polyethylene has been studied. The grafting rate shows a dependence on monomer which is far different than what has been assumed. Further, the dependence on monomer changes with increasing dose rate as does the dependence of grafting rate on radiation dose rate. Three different regions of behavior are defined: 1- a low dose rate region where the grafting rate is 1 2 - order in dose rate and 3 2 - order in monomer, 2- an intermediate dose rate region where the grafting rate is intermediate between 1 2 - and 0-order in dose rate and 5 2 - order in monomer, and 3- a high dose rate region where the grafting rate is independent of dose rate and at least 5 2 - order in monomer. Various possible mechanisms responsible for these effects are discussed, including the effects of viscosity on the initiation and termination reactions and the possibilities of ionic graft polymerization and energy transfer.

Radiation-induced grafting polymerization by the ionic mechanism

A technique of radiation-induced grafting under conditions of extreme drying of monomers has been developed. Under such conditions, radiation-induced grafting polymerization of isobutylene, α-methylstyrene, vinyl-n-butyl ether, styrene, acrylonitrile, and 4-vinylpyridine by the ionic mechanism at room temperature has been performed. The grafted copolymers of polyethylene, Teflon and polyvinyl chloride with monomers polymerized only ionically (isobutylene, α-methylstyrene, vinyl-n-butyl ether) have been obtained for the first time. The kinetics of the radiation-induced grafting of vinyl-n-butyl ether on to polyethylene have been studied; the ionic mechanism has been confirmed. It has been found that the rates of the radiation-induced ionic grafting of styrene, acrylonitrile, and 4-vinylpyridine are much greater than those for radical grafting. The highest grafting rates are observed for 4-vinylpyridine. The mechanism of radiation-induced ionic grafting polymerization has been discussed; generalized kinetic equations have been derived to account for the contributions from radical and ionic processes.

The kinetics of radiation-induced ionic graft copolymerizations

The kinetics of radiation-induced ionic graft copolymerizations

Radiation-induced ionic graft copolymerization at room temperature

The development of methods involving ionic grafting as a means of modifying the properties of polymers is of importance from both the practical and the general scientific standpoints. Practically all current investigations in this field are carried out without the use of irradiation techniques. Considerable difficulties are frequently encountered in ionic grafting; it is sometimes found to be impracticable on account of the necessity of devising some means of creating ionic active centres in the polymers, and authors often have recourse to rather complex ways of solving this problem [1, 2]. One of the simples and commonest methods used for the purpose naturally involves the use of ionizing radiation capable of giving rise to ionic active centres in polymers. Low-temperature radiation-induced ionic polymerization were first discovered a long time ago [3, 4], and a number of authors have reported on their investigations of radiation-induced ionic graft copolymerization processes in swollen polymeric films at low temperatures [5–7]. For instance the radiation-induced grafting of isobutylene onto PVC film is described by authors [6, 7] who did so by irradiating the film in a solution of isobutylene in chloroform at −78 and −196°. However, at low temperatures it may be inconvenient or impossible to carry out these processes of ionic grafting involving irradiation. On the other hand attempts to used the method of irradiation at room temperature as a means of grafting monomers polymerizable only by ionic mechanisms (α-methylstyrene, isobutylene, etc.) have generally been unsuccessful in that the grafting amounted to no more than fractions of a percentage. We assumed that radiation-induced ionic graft copolymerization would be possible at room temperature if the monomers were first subjected to a very high degree of drying. This assumption rested on the fact that a whole series of monomers polymerize on exposure to ionizing irradiation by a free ionic mechanism after very thorough drying, the reaction rate constant being ∼10 6−10 8l./mole.sec, which is higher by several orders than the rate constant for the radical mechanism. However, the rate of termination on impurities (especially H 2O, NH 3) is also very high (∼10 10l./mole·sec). The ionic polymerization initiators are thought to be the ion-radicals produced by irradiation of the monomers [8–11].

Ionic graft copolymerization. VII. Ionic graft copolymerization of β‐propiolactone onto the trunk polymers containing pyridine, amide, sulfonyl chloride, and carboxylic acid anhydride groups

AbstractThe graft copolymerization of β‐propiolactone (βPL) onto the various trunk polymers containing polar substituents such as pyridine, amide, sulfonyl chloride, and carboxylic acid anhydride groups was carried out. In the grafting onto the basic trunk polymer containing 4‐vinylpyriding units, two kinds of grafting mechanism are supposed. In the case of rigorously dried trunk polymer, the polymerization is initiated by betaine and proceeds with higher grafting efficiency. Another is initiated by pyridinium hydroxide and proceeds with lower grafting efficiency. Another is initiated by pyridinium hydroxide and proceeds with lower grafting efficiency in the presence of some amount of water. With acidic trunk polymer containing sulfonyl chloride groups, no graft copolymer was produced. The grafting efficiency of βPL onto the amphoteric trunk polymer containing acrylamide units was found to be between those of basic and acidic trunk polymer. In addition, the grafting by means of ionic copolymerization of βPL with maleic anhydride units contained in trunk polymer proceeded with very high grafting efficiency.

Ionic graft copolymerization. VIII. Homopolymerization of β‐propiolactone by radical catalysts in the presence of electron acceptors and application to graft copolymerization

AbstractThe polymerization of β‐propiolactone (βPL) induced by radiation and by radical catalysts, the influences of radical inhibitors and electron acceptors on this polymerization, and graft copolymerization were studied. It was found that βPL was polymerized by benzoyl peroxide in the presence of electron acceptors such as maleic anhydride and acrylonitrile. This polymerization method was applied to graft copolymerization. The electron donative trunk polymer containing ether groups was heated with benzoyl peroxide or was irradiated by γ‐rays from Co60 in the presence of maleic anhydride as the electron acceptor. βPL was added subsequently to form the graft copolymer.

Ionic graft copolymerization. IV. Polymerization of β‐propiolactone by acetic acid, p‐toluenesulfonic acid, and their sodium salts

AbstractAcetic acid, toluenesulfonic acid, and their salts are used as four representative ionic catalysts for polymerization of β‐propiolactone (βPL). They are classified as follows: sodium acetate is an anionic catalyst, acetic acid is a neutral one having more covalent character, sodium toluene sulfonate is a neutral one having more ionic character, toluenesulfonic acid is a cationic one. The neutral catalyst having more covalent nature is hardly dissociated, and therefore the rate of polymerization is quite small; however, dissociated ions consist of a higher neucleophilic anion and a higher electrophilic cation. On the contrary, the neutral catalyst having an ionic bond dissociates more easily, but the formed ions consist of the less reactive anion and cation. Therefore, it is of interest whether β‐propiolactone is polymerized by a cationic mechanism or an anionic mechanism by these catalysts. The mechanisms of polymerizations of βPL by these neutral catalysts were studied on the basis of the different behaviors of polymerizations by the four catalysts described above. In the cationic polymerization by toluenesulfonic acid, the rate of polymerization was high, but the conversion reaches a low, limited value. In the anionic polymerization by sodium acetate, the rate of polymerization was high and the degree of polymerization of polymer was the highest. Acetic acid has the lowest catalyst activity and the degree of polymerization is also very small. It was found that the polymerization by sodium p‐toluenesulfonate was accelerated in the presence of acrylic acid produced from βPL by hydrogen‐transfer reaction.

Ionic graft copolymerization. V. Graft copolymerization of β‐propiolactone onto the trunk polymers containing carboxylic acid, sulfonic acid, and other salts

Abstractβ‐Propiolactone (βPL) was graft‐copolymerized onto styrene–divinylbenzene copolymers containing various carboxylates or sulfonates, composed of anions and cations having different electronegativities. In parallel, the mechanism of polymerizations of βPL by relatively neutral catalysts was studied in comparison with the behaviors of graft copolymerizations. In the graft copolymerization onto the trunk polymer containing various carboxylates, a lower electronegativity of countercation favors a higher anionic polymerization activity and the order of rate of polymerization coincides with that of anionic activities of catalysts. On the other hand, in the case of trunk polymer containing sulfonates, a higher electronegativity of countercation favors a cationic polymerization activity, and the order of rate of polymerization coincides with that of cationic activity of catalyst. The order of grafting efficiency at fixed total conversion coincides almost with that of anionic activity. The comparatively higher grafting efficiency in the grafting onto trunk polymer containing carboxylic acid might support an anionic graft copolymerization mechanism by carboxyl anion. The two following mechanisms were proposed for the initiation of the polymerization by the trunk polymer containing sodium sulfonate, in which acrylic acid is transformed from βPL.

Ionic graft copolymerization. VI. Graft copolymerization of β‐propiolactone and N‐vinylcarbazole onto trunk polymer containing carboxylic acid, sulfonic acid, and their salts

AbstractIt was pointed out in previous papers that both cationic and anionic polymerization might be involved simultaneously in grafting onto trunk polymers containing COOH or SO3Na. The graft copolymerization of β‐Propiolactone (βPL)–N‐vinylcarbazole (NVCZ) onto styrene‐divinylbenzene copolymers containing carboxylic acid, sulfonic acid, and their salts was carried out in order to distinguish between the polymers produced by anionic and cationic mechanisms. The polymer obtained by the polymerization of βPL–NVCZ with BF3·OEt2, a typical cationic catalyst, consisted mainly of NVCZ units, but the polymer obtained with BuLi, a typical anionic catalyst, consisted mainly of βPL units. In the graft copolymerization of NVCZ–βPL onto trunk polymer containing COOH, the NVCZ contents of the branch polymer and the tolueneinsoluble fraction were estimated to be ca. 50 mole‐%; therefore these polymers were produced by both cationic and anionic mechanisms. In the case of graft copolymerization onto the trunk polymer containing SO3Na, it was found that both cationic and anionic polymerization also occurred simultaneously.

Ionic graft copolymerization. I. Homopolymerization of β‐propiolactone by sodium acetate catalyst

AbstractThe polymerization of β‐propiolactone (βPL) by sodium acetate catalyst has been investigated. The polymerization behavior with monomer purified with calcium chloride was found to be a little different from that previously reported for this monomer. That is, poly‐β‐propiolactone (PβPL) obtained from βPL dried with CaCl2 has a higher degree of polymerization than that obtained from conventionally treated βPL, and its infrared spectrum shows type II configuration, which differs from that reported in previous papers. Some chain transfer reaction is observed even for the polymerization of the CaCl2–dried βPL; however, this is less important in toluene. The electronegativity of the anion or cation in catalyst greatly influences the rate of polymerization.