V.P. Zubov

Kinetics and mechanism of the low-temperature radiation-induced post-polymerization of butyl methacrylate in the presence of zinc chloride☆

12. A. P. RUDAKOV and N. A. SEMENOV, Mekhamka pohmerov, No 3, 155, 1965 13 R. JEWELL, J . Appl. Polymer Sei. 12: 1137, 1968 14 E. N. TELESHOV, I. B. FELDBAUM and A. I. PRAVEDNIKOV, Vysokomol. soyed. AI0: 422, 1968. (Translated in Polymer SeL U.S.S R. 10: 2, 493, 1968) 15. L. A. LAIUS, M. I. BESSONOV and F. S. FLORINSKII, Vysokomol. soyed A12: 1834, 1970 (Translated m Polymer Sel. U S S R. 12: 8, 2080, 1970)

Study of the initiation mechanism of post-radiation graft polymerization of vinyl monomers on solid inorganic materials☆

Abstract ESR was used to study the type of active centre of silica gel exposed to γ-radiation. It was shown that at 20°SiO type radicals are the main initiating centres of polymerization on silica gel exposed to γ-radiation. When carrying out post-radiation graft polymerization of methylmethacrylate on silica gel exposed to γ-radiation high degree and efficiency of grafting cannot be achieved. As a result of the treatment of silica gel and macro-porous glass using chlorosilanes the concentration of active centres formed by the action of γ-radiation can be markedly increased and the yield of graft polymers and the efficiency of grafting, raised.

On the gel-effect mechanism in radical polymerization☆

Abstract An explanation of the gel-effect is proposed based on a representation of the change of the type of diffusion in macromolecules in moderately concentrated solution with increasing conversion by taking into account the non-equivalence of contacts of macromolecules of different length. Attention was mainly devoted to the threshold of gel-effect since it can be analyzed separately from other stages. The dependence of this threshold on the macromolecular mass distribution was considered for polymer being formed up to the onset of gel-effect. The conditions estimated from the suggested model for onset of gel-effect correspond with the experimental data. On the basis of this model some conclusions are discussed concerning auto-acceleration in systems containing polymer with bimodal distribution, which can be used for experimental verification and correcting the model.

ESR detection and study of polymerthyl-methacrylate radicals bound in a complex☆

The introduction of transition metal salts forming complexes with monomers permits substantial increase of the rate of radical homopolymerization, and makes it possible to influence the composition of copolymers produced in such systems [1–10]. We assumed on the basis of other work [6, 8] on the kinetics of polymerization in the system methyl methacrylate (MMA) with AlCl3 or AlBr3, that the reaction between the complex former and the chain propagation radicals would play an important part in the respective radical polymerization mechanism. The result of the above reaction could substantially change the radical reactivity. This work deals with the task of detection and study of the poly-MMA radicals, bound in the complex, by ESR. The complex formers were here AlCl3, AlBr3, ZnCl2, and GaCl3. An increase of the MMA polymerization rate in the presence of AlCl3, AlBr3 and ZnCl2 had already been observed [2, 4–6, 8]. Our preliminary tests have shown that GaCl3 also causes an increase of the rate of MMA photopolymerization (by a factor of 6, when the [GaCl3]/[MMA] molar ratio was increased to 0·5).

Effect of complexing agents on the polymerization of allyl monomers

IN SEVERAL papers [1-5] it was found that the radical polymerization of some vinyl monomers (methyl methacrylate, acrylonitrile, etc.) is accelerated in the presence of coordination-unsaturated metal halides (LiC1, ZnC12, A1Br3, etc.) which form complexes with functional groups of the monomer. I t was desired to s tudy the effect of complexing agents on the polymerization of allyl monomers. In this research we investigated the bulk polymerization of allylacetate (AA) and allyl alcohol (AS) in the presence of ZnCI~. The polymerization was initiated by e°Co F-irradiation, or photochemically. The monomers were purified by the usual methods, the criterion of puri ty being the agreement of the constants with those in the literature and the absence of alien peaks in the gas-liquid chromatogram. Zinc chloride of analytical puri ty was not subjected to further purification, but was dried in a vacuum by heating. The ZnC12 solutions in the monomers were prepared either by direct mixing of the ingredients or, in the case of high concentrations of ZnCI~, by vacuum distillation of the surplus monomer from a solution saturated at room temperature, as in this way the ZnC12 is not precipitated, and the system remains homogeneous. The kinetics of the polymerization were investigated by the dilatometric and gravitometric methods and the results were within the limits of measuring errors. With all the ZnCI~ concentrations the radiation polymerization and photochemical polymerization commenced immediately, without any induction period, and plots for degree of conversion versus time are linear right up to high degrees of conversion, which is characteristic of the radiation polymerization of allyl monomers [6]. A s tudy was made of the dependence of the rate of polymerization of AA on the concentration of ZnC12. The tests were carried out with close rates ranging from 160-620 r/sec, within limits of 20-55 °. In all cases the polymerization rate is increased 5.6-6 times in the change from pure AA to a 1 : 1 complex. The characteristic curve is shown in Fig. 1. The rate of polymerization is a function of the dose rate to a degree close to unity and is weakly dependent on tempera-

Synthesis of block copolymers by non-fissile radical polymerization in the presence of o-phosphoric acid☆

It was shown that during polymerization of methyl methacrylate (MMA) or methyl α-chloracrylate (MCA) in the presence of o-phosphoric acid, complex forming agent, long life radicals are formed at room temperature in an external homogenous system, which after excluding the source of initiation, can effect non-fissile polymerization. If, after all the monomer had reacted, further monomer is added, the reaction continues as a result of extension of macroradicals formed. MMA-MCA block copolymers were sythesized. Block copolymers were obtained both by grafting MCA on PMMA macroradicals and by grafting MMA on PMCA macroradicals. Fractionation, sedimentation and turbidimetric titration showed that the polymers synthesized only contain two types of macromolecule, one of which is a block copolymer and the other PEC is observed over a sufficiently wide composition range 2.5<PVPB:PMMA<5, and does not involve dissociation of PEC into components. The mechanism of formation of water-soluble polycomplexes is considered, and a model of such polymcomplexes is suggested.

Polymerization of allylamines in the presence of protonic acids

The polymerization of allylamine and dimethylallylamine has been studied in the presence of phosphoric acid. It has been shown that the polymerization product is a high molecular polymer. A kinetic scheme is put forward for the process, features of which are the participation of the monomer in the initiation stage and the linear annihilation of allyl radicals and their ability to renew the kinetic chain. It has been shown that the principal factor responsible for the increase in polymerization rate in the system allylamine-H3PO4 is the essential suppression of degradation chain transfer both as a result of a decrease in the removal of the α-hydrogen atom and also because of the ability of the complexed allyl radicals involved in chain transfer to link to the double bond of the monomer.

Study of the “alternating” copolymerization mechanism of butyl methacrylate and 2,3-dimethyl butadiene in the presence of complex-formers☆

The mechanism of the formation of alternating copolymers was studied on the system butyl methacrylate-2,3-dimethyl butadiene as model, using (C2H5)2AlCl and ZnCl2 as catalysts. ESR was used to trace the sequence of elementary reactions leading to the formation of the alternating copolymer. The monoradicals were found to be the reactive centres in all the process stages. Chain propagation is the result of consecutive monomer molecule additions to the growing macroradical. The mechanism of the formation of alternating copolymer in the system examined is believed to be the result of the large relative increase of the criss-cross chain propagation constants (k12 and k21) in the presence of the complex formers.

The initiation of low temperature polymerization in systems produced by the molecular beam method

WE have shown in previously published work, using the molecular beam method that a number of monomers when condensed on a strongly cooled surface together with small quantities of inorganic ~:ubstances (metals, salts, oxides) are capable of polymerization at and below the melting point at very high rates (often with explosion) [1-7]. At the same time these same inorganic substances are completely inert when added to the monomers under ordinary conditions. The present communication is devoted to a more detailed examination of the initiation of polymerization in these systems.

Effect of keto-enol tautomerism in complexation and radical copolymerization of vinylcyclohexyl ketones with maleic acid derivatives☆

Abstract IR and PMR spectroscopy have demonstrated the formation of charge transfer complexes in the monomer systems vinylcyclohexyl ketones-maleic acid derivatives and established that it is due to the keto-enol tautomerism of the vinyl ketones in presence of electron acceptor monomers of the maleic series. Radical copolymerization has been carried out for different ratios of monomers and the formation of alternating copolymers is established. The course of alternating copolymerization is explained by the influence of the enol form of the vinyl ketones on their reactivity in radical copolymerization with maleic acid derivatives. The photochemical conversion of the synthesized copolymers on exposure to UV radiation has been investigated.