SK214092A3 - Method of preparation of functional poly(met)acrylates by anions polymerization - Google Patents

Abstract

The proposed process for preparing functionalized poly(meth)acrylates by anion polymerization is characterized in that polymerization of either acrylate or methacrylate monomers is carried out in the presence of initiators being selected from a group comprising tertiary alkyl esters of saturated carboxy acids metallated in {alpha}-position with alkali metal, tertiary alkoxides of an alkali metal, optionally in a mixture with a tertiary alcohol and optionally in the presence of an alkali metal tertiary alkoxide functioning as a stabilizing agent of polymerization active centers in the presence of a solvent being selected from a group comprising an aromatic hydrocarbon, cyclic ether or a mixture thereof, at a temperature ranging from 70 to 50 degC, whereupon a selective hydrolysis of ether or ester bound tertiary alkoxy groups at the beginnings and/or ends of the polymeric chains.

Description

Technical field

The invention relates to a process for the preparation of functionalized poly (meth) acrylates by anionic polymerization.

The state of the art

Polymers carrying reactive functional groups at the end of their chains have found wide application in the preparation of block and graft copolymers, which have recently become increasingly important, particularly in the context of the study of the miscibility of commercial polymers. For the preparation of these functional and derived products, telechelic products are used. shows the most suitable method of utilizing the living nature of the anionic polymerization growth centers, by a suitable subsequent reaction which, after the monomer has been consumed, can incorporate the desired functional group at the end of the resulting polymer chain using the appropriate reagent. This problem has been and still is intensively studied, especially for those monomers whose active growth centers during anionic polymerization are extremely stable and do not undergo spontaneous side reactions.

An example is the hydroxylation of living polyv by a hydrocarbon medium by reaction with oxirane by protonation of the terminal

Wiloughby

Mechanisms and styryllithium and subsequent oxyanion (Schulz

anionic

Synthesis

ACS, Washington

D. N. Polymer et al., J.E., Ed., ACS

D.C. 1981). Because the initiators apparently alkoxides only very

Sanda J.C. , Kinetics,

Symposium Seires No 166, the oxirane ring is very difficult to homopolymerize due to its low reactivity, the product of this process is hydroxylated polystyrene in virtually quantitative yield. Similarly, telechelic alpha, omega-dihydroxy polybutadiene can be prepared using a bifunctional initiator (e.g., a dilute dimer of alpha, omega-methylstyrene) and terminated with alpha, omega-dihydroxy polybutadiene by oxirane units. These processes have been described previously and are practically free of major complications and are even commercially utilized. Another possibility of hydroxylation is, for example, initiation of polymerization by a lithium derivative of acetal, acetaldehyde or tetrahydropyran (Schulz DN, Halasa AF, Oberfahr AE: J. Polymer Sci., Pol. Chem. Ed. 12, 153 (1974)) containing masked hydroxy groups. , releasable upon completion of the reaction by slight hydrolysis. A less reactive, tertiary-bonded hydroxy group can also be incorporated at the end of the chain by reacting the living polymer with a suitable carbonyl compound (benzophenone) and then protonating the resulting alkoxide (Quirk RP et al .: Rubber Chem. And Technol., 64, 648 (1991)) . The functionalization of the carbohydrate polymers (polystyrene) has also been extensively studied, but the results are not as unambiguous as in hydroxylation. Conventionally, it is possible to actively terminate the polymer chains with carbon dioxide in solid or gaseous form. It is preferable to work in an environment with an increased solvation ability that reduces the degree of aggregation of the living chains and thereby limits their dimerization and trimerization. Experiments giving 60-90% yield of polystyrene or carboxy-functionalized polyisoprene according to the conditions have been described. The formation of by-products can also be reduced by converting styryl carbanion into a sterically more protected and less reactive carbanion by reacting living polystyrene with 1,1-diphenylethylene and its subsequent carboxylation (Fetters LJ, Young RN: in Anionic. Polymer isation: Kinetics, Mechanisms and Synthesis) McGrath JE, ACS Symp. No. 166, AACS, Washington DC, (1981), Quirk RP, Yin, Fetters LJ: Macromolec 1, 22, 85, (1989).

In the case of polar vinyl monomers, the preparation of functionalized polymers is clearly more difficult, since their living chains undergo spontaneous side reactions, i.e. more rapidly, and reactions with the corresponding termination factors. do not go unequivocally. They are used therefore, complicated processes, such as initiation of polymerization metylmetakr / methacrylate alyllítiom tetrahydro of the determined ane (THF) at -78 ^'::' C to vzri.kne polymethyl methacrylate (polyMMA) with allylic double bonds, the initial drive. This is then converted to the hydroxy group by hydroboration and reaction with peroxide. When the polymerization is terminated with an allyodide before spontaneously stopping, polymethyl methacrylate with double bonds at both ends of the chain is prepared, followed by the two-hydroxy telechelic polymethyl methacrylate (Al-Takrity ETB, Jenkins AD, Walton Chem. Macromol. 3077 (1990)).

Further possibilities have been developed in recent years by grouptransfer polymerization (GTP) (Webster O.W., Hertler W.R., Sogah D.Y., Farnham W.B., Rajan Babu T.W .: J. Am. Chem. Soc., 105, 5706 (1983)). Instead of conventional 1-methoxy-1-trimethylsiloxy-2-methylpropene, for example, 1-methoxy-1-trimethylsiloxy-2- (2-trimethylsiloxyethoxy) propene may be used and the trimethylsiloxy group may then be hydrolyzed to hydroxyl under mild conditions. By combining the two living polymer chains with a suitable bifunctional terminating agent such as dibromo-p-xylylene or terephthalic bifluoride with subsequent hydrolysis of trimethylsiloxy groups as before, a telechelic polymer with hydroxyl groups can be prepared at both ends of the chains ( J. Polymer Sci., Pol Lett, Ed., 21,927 (1983), Cohen GM: Pol Prepr., Am Chem Soc, Div Pol Chem 29 (2), 46 (1988). The authors also envisage the possibility of functionalizing the polymer with a carboxy group, however, further details are not yet available.

However, carboxylic polymers can also be prepared by radical polymerization using a functionalized transfer reagent such as thioglycolic acid (2-thiopropionic acid), by which the appropriate group can be introduced directly at the beginning of the polymer chains. Although the procedure is even commercially used, it cannot be reliably managed and gives not quite clear results.

All of the above methods are particularly complicated for polar vinyl monomers and require prior synthesis of special initiators (GTP), more complex multi-stage synthesis (anionic polymerization followed by hydroboration) or are not readily operable (radical polymerization).

Summary of the invention .......

These disadvantages are overcome by the process of the present invention, which utilizes the studied initiation systems and relatively simple hydrolysis of the masked functional group intermediates. SUMMARY OF THE INVENTION The present invention relates to a process for the preparation of functionalized poly (meth) acrylates, characterized in that the polymerization of acrylate or methacrylate monomers is carried out in the presence of initiators selected from the group consisting of tertiary alkyl esters of saturated carboxylic acids. , tert, alkali metal alkoxides, optionally in admixture with tert. with an alcohol and optionally in the presence of a tert, alkali metal alkoxide stabilizer of the active polymerization centers of the mixture, selectively in a solvent selected from the group consisting of aromatic at -70 ° C to ether, or ether hydrolysis thereof or of the tertiary alkoxy groups at the beginning and / or at the ends of the polymer chains.

In carrying out the process according to the invention, the polymerization can be carried out by a tert, alkyl ester of a saturated carboxylic acid, metallized at the alpha position with an alkali metal initiator, in the presence of tert, alkali metal alkoxide stabilizer of the active polymerization centers. of an alkyl ester of a saturated alkali metal metallized to the tert. the alkali metal alkoxide is in the range of 1: 1 to 1:20, preferably 1: 3 to 1:10, in a mixed solvent composed of an aromatic hydrocarbon and 0 to 10% by volume of a cyclic ether, at temperatures in the range of -70 ° C ^L to 0 ° C, to which, after the polymerization by acid catalyzed hydrolysis of the ester-linked selectively hydrolyzed t, alkoxy when at the beginning of each polymer chain.

It is further possible to proceed by adding tert to the reaction mixture after the monomer has been consumed before completion of the polymerization. butyl acrylate or methacrylate at a concentration equal to or higher than the active growth center concentration, then the polymerization is terminated, and then the product with ester-linked tert, alkoxy groups at the beginning and one or more groups at the end of each polymer chain is subjected to selective acidic hydrolysis.

Initiators used in the process according to the invention are tertiary. alkyl esters of saturated carboxylic acids having 2 to 10 carbon atoms in the chain, preferably tert, isobutyric and propionic alkyl esters metallized at the alpha position by an alkali metal selected from the group consisting of lithium, sodium, potassium and cesium.

The initiators or stabilizers of the active polymerization centers are tert, alkali metal alkoxides having 4 to 10 carbon atoms in the chain and an alkali metal selected from the group consisting of lithium, sodium, potassium and cesium.

A further feature of the process of the invention is that the polymerization of the monomer is carried out in the presence of 1 to 10 mol% of the alkali metal alkoxide initiator, based on the monomer concentration, in a cyclic ether or aromatic hydrocarbon environment at temperatures in the range of -60 'C to 20' 'C, to which the product with an ether-bound tert. undergoes acidic cleavage at the beginning of each chain.

The process of the present invention can be readily accomplished by polymerizing the monomer in the presence of a mixture of a tert-alkali metal alkoxide and a tert. % alcohol, wherein the molar ratio of monomer to tert-alcohol is selected according to the desired polymerization stage in the range of 2 to 100, in the presence of polar cyclic ether in an amount of 5 to 20% by volume based on the monomer volume and at a temperature of 0 ° C to 50 ° C, for which the product with an ether-linked tert-alkyl group is subjected to acidic cleavage at the beginning of each chain.

Thus, in the preparation of the carboxy-functionalized poly (meth) acrylates by the process of the invention, a tert-alkyl, preferably isobutyric, propionic, alkyl metallised in the alpha position with an alkali metal, together with the tert, alkali metal alkoxide as stabilizing additive is used to initiate polymerization. The initiator carbanion is incorporated as an initiating particle at the beginning of each polymer chain and upon completion of the polymerization, its tertiary alkoxy group can be liberated by selective hydrolysis, while the other ester groups on the polymer chain are not subject to acid hydrolysis and thus the chemical structure of the prepared polymer remains. The telechelic polymer can be prepared by adding a small amount of tert-butyl acrylate or methacrylate at a concentration approximately equal to that of the active centers to form a polymer such as polymethyl methacrylate (immediately after consuming the initial dose of a monomer such as methyl methacrylate (MMA)). p-MMA), terminated on average by one tert. butyl (meth) and rylate. By acid hydrolysis of both tert. butoxy groups then obtain a polymer, for example polymethyl methacrylate (p-MMA), functionalized on average by two carboxy groups, at both ends of the chain. When this monomer is used at a concentration several times higher than the concentration of the active chains, a polymer is obtained at the end stage, carrying a correspondingly higher number of carboxy groups at the end of each chain.

Tertiary initiator is used as the initiator for the preparation of hydroxy functionalized polymers. an alkoxide, preferably a butoxide, a pentoxide, an alkali metal hexoxide of lithium, sodium, potassium, and cesium; tert, the alkoxy group incorporated at the beginning of each polymer chain is converted to the hydroxy group by acidic cleavage upon completion of the polymerization. In this process, it is possible to utilize the transfer of growth centers with tertiary alcohol and specifically to prepare oligomeric products with a selected polymer of the initial stage.

Functionalized (reactive) poly (meth) acrylates may find widespread use, for example, in the preparation of block copolymers with polylurethane or polyylamide sequences containing a terminal isocyanate group, optionally polyester, hydroxy- or carboxy-terminated , in the cleavage of polymers with side carboxy, hydroxy or epoxy groups, in reactive injection, etc.

The invention is further illustrated by the examples without being limited thereto.

EXAMPLES

Example 1

0.45 g (0.00467 mol) of sodium tert-butoxide was added to a baked and dried flask equipped with a three-way inert gas inlet flask and a magnetic stirrer and dissolved in 2 ml of dried tetrahydrofuran. 0.44 ml (0.00463 mol) of distilled and dried tert-butanol are then added with stirring, and the mixture is stirred for an additional 5 minutes, still at normal temperature. 10 ml (0.0936 mol) of distilled and dried methyl methacrylate are then added, the flask is placed in a 25 ° C bath and the mixture is stirred at this temperature for 20 minutes. All reagent dosing operations are performed in countercurrent with inert gas (argon, nitrogen).

The temperature is then raised to 40 ° C, and the mixture is allowed to polymerize at this temperature for 5 hours. The reaction is then quenched by the addition of 1 ml of methanol in 10 ml of chloroform, in which the resulting polymer is dissolved. The product was isolated by precipitation to 20 times the volume of heptane and dried to constant weight under vacuum at 40 ° C. The following molecular weights of Mw-4580, Mn = 2840, were determined by SEC, the theoretical Mn, calculated from the ratio of methyl methacrylate to tert-butanol, was equal to 2100.

From the polymer thus prepared, 5 g was weighed into a 100 ml flask with a magnetic stirrer, and dissolved in 60 ml of distilled 1,4-dioxane. Concentrated hydrochloric acid (20 ml) was added and the mixture was heated under reflux for 6 hours with stirring. Then the solution is cooled, rotary evaporated to dryness, the polymer is dissolved in about ml of benzene and precipitated to twenty times the volume of hexane or heptane and dried under vacuum to constant weight. The product obtained does not contain the initial tert-butoxy groups from the alkoxide initiator, and by cleaving them a functionalized hydroxymethylmethacrylate (poly-MMA) with a hydroxy group is prepared at the starting unit of each polymer chain. In the ¹³ C NMR spectra of the final product, the band completely disappeared at 26.11 ppm and in the IR spectrum a broad band appeared by vibration of the OH groups of about 3500 cm ^-1 . The extent of cleavage of the methoxy groups on the polymethyl methacrylate (PMMA) chain is negligible.

Example 2

As in Example 1, a mixture of tert-potassium hexanolate (0.640 g, i.e. 0.00467 mol) and tert-butanol (0.22 ml, i.e. 0.00234 mol) in 2 ml distilled and dried was prepared. tetrahydrofuran (THF) and polymerized with 10 mL of methyl methacrylate (MMA). Upon completion, the polymer with Mn according to SEC 5400 is isolated. The product is then subjected to acidic cleavage of the tert-alkoxy group as in Example 1 and polymethylmethacrylate (PMMA) is prepared with one hydroxy group at the beginning of each chain.

Example 3

As in Example 1, a solution of sodium tert-butoxide and tert-butanol in tetrahydrofuran was prepared, followed by the addition of 14.8 ml (0.0936 mol) of butyl methacrylate. Upon completion of the polymerization, the resulting Mn-3800 polymer was isolated by precipitation into a 9: 1 methanol / water mixture and hydrolyzed in the same manner as in Example 1 except that the precipitation was made to a 9: 1 methanol / water mixture.

Final product by pin and by butoxy group. is quantitatively functional from the hydroxy-spectrum analysis it does not contain residual target.

Example 4 To the bank g (0.00028 mol) as in Example 1, 0.0224 tert-butoxide in 0.67 ml of dry hep-

and diluted with 2.33 ml dry toluene. With stirring, 3 ml of dried and distilled mety1 metakry1 carboxylate, the flask was put in the bath 20 ^'' and the mixture is left to the poly mer from ovata for 3 hours. Thereafter, the reaction is stopped by adding 1 ml of methanol in 30 ml of chloroform and, upon dissolution, is isolated by precipitation into a twenty-fold volume of methanol of half-methyl methacrylate with molecular weights according to SEC measurements Mw = 268000 and Mn = 174000. The polymer hydrolyzes as in Example 1 and, upon completion of the reaction, precipitates again into hexane or heptane. The product obtained is functionalized with hydroxy and does not contain tert-butoxy groups at the beginning of the chains.

Example 5

A 200 ml glass reactor equipped with a stirrer, a three-way stopcock for inert gas dosing and a side tempering and dosing flask of about 40 ml is used to prepare the polymer, connected to the main reactor space by a metering tube and also equipped with a three-way stopcock. . 50 ml of distilled and dried tetrahydrofuran and 0.462 g (0.00577 mol) of lithium tert-butoxide dissolved in 20 ml of dry tetrahydrofuran are charged to the main flask. A mixture of 20 ml (0.0961 mol) of distilled and dried 2-ethylhexyl and rylate and 10 ml of dry tetrahydrofuran is charged to a side flask and the reactor is placed in a -20 bath. After warming (about 15 min), the solution is transferred with vigorous stirring. of acrylate from the side to the main reactor bank by inert gas overpressure in the shortest possible time (less than 1 s). The reaction mixture is allowed to polymerize for 8 hours with stirring, then the polymerization is stopped by the addition of 1 ml of methanol, the polymer is precipitated by pouring the mixture into a twenty-fold volume of 9: 1 methanol-water and dried under vacuum at 40 ° C. According to SEC measurements, it has - 37300 and Mn = 16500. In the same manner as in Example 1, tert-butoxy groups from the starting units of the chain are cleaved to give the product. functionalized with hydroxy groups, which precipitates into a 9: 1 methanol-water mixture.

Example 6

66.5 ml of distilled and dried toluene were added to the reactor main flask, as in Example 5, followed by a solution of 0.256 g (0.00171 mol) of tert-butyl-alpha-1-i-butyrate (2-tert. butylcarbonyl-2-propyl lithium) and 0.412 g (0.00515 mol) of lithium tert -butoxide in 9.5 mL of dry tetrahydrofuran. A solution of 5 ml (0.0240 mol) of distilled and dried 2-ethylhexyl acrylate in 20 ml of dry toluene is charged to a side flask. The reactor was cooled to -60 ° C in a thermostate, and then the vinylic solution was transferred to the main flask of the reactor as in Example 5 with vigorous stirring, and the mixture was allowed to polymerize with stirring for 5 minutes and then quenched with 1 mL of methanol. The reaction mixture is then concentrated to about 30 ml in a vacuum evaporator and the polymer is precipitated to a twenty-fold volume of methanol / water 8: 2 and dried under vacuum. According to SEC is Mw = 4190 and Mn - 3700.

As in Example 1, the polymer (ca. 4 g) was dissolved in 60 ml of distilled 1,4-dioxane, 20 ml of concentrated hydrochloric acid was added, and the mixture was heated under reflux for 8 hours with stirring with a magnetic stirrer. This selectively cleaves the tert-butoxy groups of the starting chain units (tert-butyl isobutyrate) and yields a carboxy-functionalized polymer. Then the volume of the mixture is adjusted to about 40 ml by evaporation of dioxane and the product is precipitated to a twenty-fold excess of methanol / water 8: 2. In ¹³ C, it disappeared initially at 26.21 ppm and the band

The NMR spectrum of the hydrolyzed product contained a carbon-tertiary, butoxy, carbonyl group at 174.14 ppm, pertaining to the isobutyrate initially present at the beginning of each polymer chain, with the loss of 2-hexoxy groups practically non-measurable.

Example 7

As in Example 6, 62 ml of dry toluene and a solution of 0.090 g (0.00060 mol) of tert-butyl-1-phthalic acid and 0.144 g (0.00180 mol) of tert-butoxide are metered into the main reactor flask. of lithium in 8 ml of dry tetrahydrofuran and into a side flask a solution of 20 ml (0.0961 mol) of 2-ethylhexyl acrylate, which after transfer of the reactor to -60 ° C is transferred to the main flask. The mixture was allowed to polymerize with stirring for 30 minutes and the polymer was isolated in the same manner. Its = 63200 Mn = 55000. The acid hydrolysis of tert-butoxy groups on the initial polymer units is carried out in dioxane solution as in Example 6, and the carboxy functionalized polymer is precipitated into a 9: 1 methanol-water mixture and dried.

Example 8

As in Example 6, 70 ml of toluene and 0.105 g (0.0007 mol) of tert-butyl-alpha-lithium isobutyrate and 0.337 g (0.00421 mol) of tert-butyl butanolate in 5 ml of tetrahydrofuran are added to the main flask and a side flask is charged. 5 ml (0.0351 mol) of n-butyl acrylate in 20 ml of toluene. After cooling to -60 ° C and mixing of the two components, the mixture was allowed to polymerize with stirring for 5 minutes and then quenched by the addition of 1 ml of methanol. After concentration, the polymer is precipitated into a 9: 1 methanol-water mixture and dried, its Mn = 12500. Hydrolysis of the tert-butoxy groups is again carried out in dioxane solution as in Example 6, and then carboxy-functionalized polybutyl acrylate precipitates.

Example 9

As in Example 6, but in a side flask, a solution of 5 mL of methyl methacrylate (0.0468 mol) in 20 mL of toluene was charged. After cooling to -20 ° C, polymerization takes place for 30 minutes and the polymer is precipitated into methanol (Mn = 13000) after concentration. Hydrolysis of tert. butoxy groups are carried out in the same manner as in Example 6, the polymer is precipitated into heptane or hexane to prepare carboxy functionalized polymethyl methacrylate.

Example 10

As in Example 6, a tetrahydrofuran (THF) solution of 0.260 g (0.00171 mol) of tert-butyl alpha-sodium propionate and 0.639 g (0.00515 mol) of sodium tert-hexoxide was initiated into the main reactor flask. After warming to -20 ° C, a solution of methyl methacrylate (MMA) in toluene, as in Example 9, was added from a secondary flask. After 15 minutes the polymerization was terminated and the product precipitated into hexane (Mn-12700). This was subjected to acid hydrolysis as in the previous examples to give polymethyl methacrylate (PMMA) with initial carboxy groups.

Example 11

0.210 g (0.0014 mol) of tert-butyl alpha-lithium isobutyrate and 0.674 g (0.0084 mol) of lithium tert -butoxide in 70 ml of dry tetrahydrofuran (THF) are charged to the main reactor flask as in the previous examples. 10 ml (0.0936 mol) of distilled and dried methyl methacrylate (MMA) in 20 ml dry tetrahydrofuran (THF) was charged to the side flask, which was charged to the main flask after the reactor had warmed up as in the previous examples and allowed to polymerize 15 min. Meanwhile, 0.15 ml (0.0010 mol) of distilled and dried tert-butyl acrylate in 20 ml of dry THF is metered into the emptied side flask, and this solution is transferred to the main reactor flask with vigorous stirring after 15 minutes of polymerization. After an additional 5 minutes, the polymerization is thermoformed, the polymer is precipitated into heptane and subjected to acid hydrolysis as in the previous examples. After isolation, a polymethylmethacrylate having an average of two carboxy groups per polymer chain is obtained.

Example 12

The procedure was as in Example 11, but during the polymerization of methyl 1 methacrylate (MMA), a solution of 0.50 ml (0.0030 mol) of tert-butyl methacrylate was added to the secondary flask, which after 15 minutes of polymerization was treated with the same into the main reactor flask, vigorously stirred with the polymerization mixture and the reaction stopped after 5 minutes. After hydrolysis, tert. butyloxy groups of the thus prepared product yield polymethyl methacrylate (PMMA) with one carboxy group at the beginning and an average of three carboxy groups at the end of each polymer chain.

PI / O ^

Claims (7)

PATENT CLAIMS A process for the preparation of functionalized poly (meth) acrylates by anionic polymerization, characterized in that the polymerization of the acrylate or methacrylate monomers is carried out in the presence of initiators selected from the group consisting of tert. alkali metal alkoxides, optionally in admixture with tert, alcohol, and optionally in the presence of tert, alkali metal alkoxide as a stabilizer of active polymerization centers, in a solvent selected from the group consisting of an aromatic hydrocarbon, cyclic ether or mixtures thereof at temperatures ranging from -70 C 20 ^'::' C, which is carried out on the selective hydrolysis of the ether or ester-linked tert. alkoxy groups at the beginning and / or at the ends of the polymer chains. The process according to claim 1, characterized in that the polymerization is carried out with tert, an alkyl ester of a saturated carboxylic acid metallized in the alpha position with an alkali metal initiator in the presence of tert, an alkali metal alkoxide as the active center stabilizer, the ratio tert. the alkyl ester to the alkoxide is in the range of 1: 1 to 1:20, preferably 1: 3 to 1:10, in a mixed solvent composed of an aromatic hydrocarbon and 0 to 10% by volume of a cyclic ether, at temperatures in the range of -70 ° C up to 0, after which the ester-linked tert, alkoxy group at the beginning of each polymer chain is selectively saponified by acid-catalyzed hydrolysis. Process according to claims 1 and 2, characterized in that, after the monomer has been consumed, tert-butyl acrylate or methacrylate is added to the reaction mixture before the end of the polymerization, at a concentration equal to or higher than the active growth center concentration, the product with ester-linked tert-alkoxy pins at the beginning, and one or more groups at the end of each polymer chain, is subjected to selective acid hydrolysis. Method according to claims 1 to 3, characterized in that tert-alkyl esters of saturated carboxylic acids having 2 to 10 carbon atoms in the chain, preferably tert, alkyl esters of isobutyric acid and propionic acid, metallised in the alpha position with an alkali metal, are used as initiators , selected from the group consisting of lithium, sodium, potassium and via i. Method according to claims 1 to 4, characterized in that the initiators or stabilizers of the active polymerization centers are tert-alkali metal alkoxides having 4 to 10 carbon atoms in the alkali metal chain selected from the group consisting of lithium, sodium, potassium and alkali metal. cesium. The process according to claim 1, wherein the polymerization of the monomer is carried out in the presence of an alkali metal alkoxide initiator in an amount of 1 to 10 mol%, based on the monomer concentration, in a cyclic ether or aromatic hydrocarbon environment at temperatures of ^{-60, ''} C to 20 ^':' C, which is the product of the ether-bound target. undergoes acidic cleavage at the beginning of each chain. The process according to claims 1 to 6, characterized in that the polymerization of the monomer is carried out with a mixture of tert, alkali metal alkoxide and tert. alcohol, wherein the molar ratio of monomer to tert. the alcohol is selected according to the desired polymer starts to step in the range of 2 to 100, in the presence of a polar cyclic ether in an amount of 5 to 20% by volume, based on the amount of monomer and in a temperature range of 0 C to ^50: 'C, at which the ether-bound tert. undergoes acidic cleavage at the beginning of each chain.