CS258182B1 - A method of cationic polymerization and copolymerization of vinylaromatic hydrocarbons - Google Patents

Abstract

The solution relates to a method for cationic polymerization and copolymerization of vinylaromatic hydrocarbons with an initiation system enabling in particular quasiliving polymerization or copolymerization. The method consists in that the polymerization or copolymerization is carried out at a temperature of 20 to 80 °C in the presence of the initiation system 2,5-dichloro-2,5-diethylhexane/boron trichloride, wherein the molar ratio of 2,5-dichloro- -2,5-dimethylhexane to boron trichloride is in the range of 2.5-10-2 to 5, optionally in the environment of polar halogenated solvents or mixtures thereof with non-polar solvents. When carrying out the method according to the invention, it is possible to proceed in such a way that the monomer or mixture of monomers is continuously dosed into a previously prepared solution of the initiation system, while quasiliving polymerization or copolymerization takes place, in which the molecular weight of the polymer or copolymer increases with the consumption of monomers or in a conventional manner by mixing the initiation system with the monomer.

Description

The invention relates to a method for cationic polymerization and copolymerization of vinylaromatic monomers using an initiation system enabling, in particular, quasiliving polymerization or copolymerization.

Living anionic bulk polymerization by Prof. M. Szwarc has been known for 30 years (M. Szwarc, Nátuře 178, 1 186 (1956); M.Szwaro, M. Levý and R. Milkovich, J. Am. Chem. Soc. 78,

656 (1956)). Living anionic polymerization has enabled the synthesis of macromolecular substances with transferable molecular weights, where the polydispersity index has approached the theoretical value of 1. For example, in the anionic synthesis of polystyrene or poly(alpha-methylstyrene), the values are,!

Unlike anionic living polymerization, cationic synthesis has not been able to achieve living cationic polymerization until recently, despite considerable efforts by research laboratories, due to uncontrolled transfer and termination reactions. Only in 1982 was the quasiliving cationic polymerization of alpha-methyl-styrene (alpha-MeSt) described at a temperature of -50 °C in a solvent mixture of methylcyclohexane/dichloromethane (CHCl) (75/25) using the initiator system 2-chloro-2-propylbenzene/boron trichloride (BCCl) and water/boron trichloride (H ₂ O/BC1 ₃ ) (R. Faust, A. Fehérvári, J. P. Kennedy, J. Marcromol. Sci. - Chem., A 18, 1 209 (1982-83)).

According to Czechoslovak Patent No. AO 239 995 (Method of preparation of aliphatic halogeninifers, L. Toman), it is also known that 2,5-dichloro-2,5-dimethylhexane (DDH) initiates the polymerization of isobutylene in the presence of boron trichloride (BClg). The product of the synthesis is then teleohelic polyisobutylene, (C1-PIB-C1), which contains reactive chlorine at both ends of the polymer chain. This initiation and synthesis were later confirmed by Kennedy (J. P. Kennedy. 7 th International Symposium on Cationic Polymerization and Related Processes, Jena 1985, main lecture), also for the polymerization of isobutylene. The assumed mechanism of initiation is presented in the following scheme:

Cl-R-Cl + BCl _3Í =é C1-R-C1.BC1 ₃ C1-R ⁺ BC14—C1-RM ⁺ BC14” where

Cl-R-Cl is 2,5-dichloro-2,5-dimethylhexane (DDH), M is isobutylene.

This new initiation system known for the polymerization of isobutylene has not yet been described in the literature for the polymerization or copolymerization of vinylaromatic monomers such as styrene (St), alpha-methylstyrene (alpha-MeSr).

The subject of the present invention is a method for cationic polymerization and copolymerization of vinylaromatic monomers, the essence of which lies in the fact that the polymerization or copolymerization is carried out at a temperature of 20 to -80 °C in the presence of the 2,5-dichloro-2,5-dimethylhexane/boron trichloride initiator system, with the molar ratio of 2,5-dichloro-2,5-dimethylhexane to boron trichloride being in the range of 2.5.10 to 5, optionally in the environment of polar halogenated solvents or mixtures thereof with non-polar solvents.

When carrying out the method according to the invention, it is possible to proceed in such a way that the monomer or mixture of monomers is continuously dosed into a previously prepared solution of the initiation system, whereby quasi-living polymerization or copolymerization takes place, in which the molecular weight of the polymer or copolymer increases by consumption of monomers or by conventional mixing of the initiation system with the monomer.

A freshly prepared colorless CH2Cl2 solution of 2,5-dichloro-2,5-dimethylhexane (DDH)/boron trichloride (BC13) (initiation system I) or a previously prepared colored _CH2Cl2 solution _of DDH and _BC13 (initiation system II) is used as the initiation system.

Polymerization or copolymerization is carried out without an auxiliary solvent or in the environment of polar halogen solvents such as methylene chloride, methyl chloride, ethyl chloride or mixtures thereof with non-polar solvents, for example aliphatic solvents such as heptane and hexane.

The advantage of the method of polymerization and copolymerization of vinylaromatic monomers according to the invention using DDH/BCl^ i.e. initiation with aliphatic binifers Cl-R-Cl (Kennedy's name is used for substances that both initiate polymerization and cause transfer) is the synthesis of telechelic polymers or copolymers that contain reactive chlorine at both ends of the polymer chain during the synthesis carried out with continuous slow dosing of monomer into the binifer solution during the ongoing quasiliving polymerization, in which the molecular weight of the polymer or copolymers increases with the addition of monomers, which is possible in the case of using minifers such as 2-chloro-2-propylbenzene or the water' ¹ /boron trichloride /H ₂ O”/BC1 ₃ initiation system). The quasiliving synthesis of telechelic polymers/copolymers using vinylaromatic monomers and the initiation system according to the invention proceeds according to the scheme.

formation of ions Cl-R-Cl + 2BCl ₃ ^==acl-R-^. 2BC1 ₃ bci ₃ ci-r ⁺ bci ₄ initiation Cl-R ⁺ + M—>- ClR-M ⁺ propagation Cl-RM ⁺ + nM—> ClRM _n -M ⁺ termination Cl-RM M ⁺ BC1,-> Cl-RM M-Cl n 4 n

Quasiliving polymerization is enabled by the reionization reaction of the polymer chain end with boron trichloride according to the scheme:

X X

I I

CH ₂ ~ C - Cl + BClj i=- - C + BC1 ₄ where

X is H or _CH3

Reionization of the polymer chain end with boron trichloride and termination has been described previously. (J. P. Kennedy, T. Kelen and F. Tfidos, J. Macromol. Sci.-Chem., A 18 1 189 (1982-83).

Quasiliving polymerization can be carried out at temperatures higher than -50 °C, even in dichloromethane alone.

At a temperature of -20 °C, polymers with a very low polydispersity index (M _w /M _n ) = 1.1 are synthesized according to the invention at 100% conversion. This very low index corresponds to a value that has so far only been possible with polystyrenes and poly(alpha-methylstyrenes) prepared by anionic living polymerization. The thermostabilities of, for example, poly(alpha-methylstyrene) (PalfaMeSt) samples prepared according to the invention are also high, for example up to 280 °C, as shown in Example 2.

The method of cationic polymerization (alpha-MeSt), St and their copolymerization using the initiator system 2,5-dichloro-2,5-diethylhexane/boron trichloride (DDH/BC1 ₃ ) (X and II) according to the invention is shown in several examples. In all the examples below, the polymerizations were carried out in glass ampoules equipped with a piercing cap or in a glass reactor equipped with a stirrer. Solutions of DDH with BClj in dichloromethane (CH ₂ C1 ₂ ) were prepared in glass ampoules equipped with a three-way Teflon cap. The polymerizations were carried out under dry conditions under inert. Dry nitrogen was used. The ampoule and reactor were dried under vacuum while heating the dosing of CH ₂ C1 ₂ monomer solutions into the CH ₂ C1 ₂ solution containing the DDH/BClj initiator system (II) is shown in Fig. 1, where A is a calibrated monomer reservoir, B is a diaphragm pump, C is a monomer cooler to the polymerization temperature, D is a polymerization reactor containing the initiator and F is a cooling bath. Samples of the polymer solution were taken from the reactor with a syringe.

Molecular weights were determined by gel permeation chromatography (GPC) using a HP-1 084 liquid chromatograph (Hewlett-Packard, USA). The following form of the Mark. Houwink equation valid for polystyrene was used for the calculation: ⁼ 1.17.10 ² Μθ, 717, the relation for is expressed in cm ³ /g. Due to the known protegenic initiation of alpha-methylstyrene (alpha-MeSt) (HjO+BClj tp=aH ⁺ BC1 ₂ OH-^HM ⁺ + BCl^OH ) the initiation system according to the invention will be compared with the water/boron trichloride system (H ₂ O/BC1 ₃ ) in some examples below under the same experimental conditions. The synthesis products and the synthesis processes during continuous dosing of CH ₂ C1 ₂ solutions of alpha-MeSt into CH ₂ C1 ₂ solutions of initiators will also be compared.

Example 1

The polymerization of alpha-methylstyrene (alpha-MeSt) was carried out in a conventional manner in a dichloromethane (CHCl) solution. A freshly prepared colorless _{CHCl solution} of DDH with _BCCl (initiation system I) and _a tea-colored _CHCl solution of DDH with _BCCl (initiation system II) stored for 1 month at room temperature before use, containing a complex formed by the interaction of 2,5-dichloro-2,5-dimethylhexane with boron trichloride (DDH with BCl), were used for initiation. The results of the synthesis in the temperature range -20 to -60 °C are given in Table I.

Table I

Temperature °C I Initiation System II Conversion % Conversion % n -20 58.0 3 518 65.8 2 684 -30 73.1 3 887 82.6 3 275 -40 95.3 5 129 100 4 396 -50 100 7 661 100 6 142 -60 100 10 967 100 9 149

[_alpha-MeStJ = 0.85 mol/l, £bCl^ = 8.3.10 ^-2 mol/l, [[)Dh] = 1.66.10 ^-2 mol/l; polymerizations were stopped after 15 min by addition of methanol.

Example 2

The polymerization of alpha-methyl-Styrene (alpha-MeSt) was carried out as in Example 1 but in the temperature range of -70 to -75 °C. The polymerization using initiator systems I and XI is compared with the water/boron chloride (H ₂ O/BC1 ₃ ) system with a molar ratio of JĚC1^] / Jh ₂ Ó] = 4. The concentration of £bC1^| , JjĎdh] [alpha-MeSt] is the same as in Example 1. In the H ₂ O/BC1 ₃ system, water was added to the monomer solution using wet dichloromethane (CH ₂ Cl ₂ ) before the addition of the freshly prepared CH ₂ Cl ₂ solution of BClj. Thermogravimetric measurements were performed on the synthesized polymers, demonstrating that the thermostability of P-alpha-MeSt samples prepared according to the invention is 35 °C higher than that of P-afla-MeSt samples prepared by proton initiation. The results of the synthesis and thermogravimetric studies are presented in Table II and in Figs. 2 and 3.

Table II

Initiation system ^f, n Weight loss of P-alpha-MeSt was not detected up to temperature h ₂ o/bci 18,393 145°C (Fig. 2) II 23,227 ²⁸⁰ ° ^C (Fig. 3) I 38,459 280°C

after 15 min of polymerization, 100% conversion was achieved for all systems

Example 3

The polymerization of alpha-methylstyrene (alpha-MeSt) was carried out at a temperature of -40 °C by continuous slow dosing of CH ₂ C1 ₂ monomer solution at a rate (A) of 1.91.10 ^- ^ mol alpha-MeSt/min into 20 ml of pre-cooled stirred initiation system II (colored CHjCl, DDH solution with BClj prepared in the same way as in example 1 but with a concentration j_BClT] = = 2.5.10 ¹ mol/1 and [ddh] = 2.5.10 ² mol/1). Polymer samples taken from the reactor during continuous monomer dosing showed the presence of two polymer fractions in the resulting polymer, lower molecular weight (F^) and higher molecular weight (Fy).

With increasing monomer consumption, the molecular weight of both fractions increased proportionally, along with the increasing mass content of F^ in the polymer samples, as shown in Table III. After 75 minutes of continuous monomer dosing, the reaction was terminated by adding methanol at a total conversion of 100%. As a result, M . is more than 1 order of magnitude lower than M . and higher mass content in the polymer, it is clear that the number of polymer molecules EJ ^F N»t3 ^F V ^a (where (jQ =0F _n + QpjFyH, against the monomer consumption is shown in Fig. 4 and showed a linear increase M , with monomer consumption at a demonstrated very low transfer (the number of polymer molecules h -2 -2 increased in the interval from 3.84.10 to 14.21.10 mol alpha-MeSt only twice). Since ^H-NMR analysis of polymer samples did not show the presence of double bonds that would indicate transfer by the monomer, it is clear that the transfer probably took place by the transfer substance binifer, which complexes with BCl^. The mechanism of reversible transfer by binifer can then be shown by the scheme:

®R-C <λλ\/ íP + Cl-R-Cl. 2BC1 > WM-C1 + ^-dBC^ + BClj

4-C1 fiřebyteKJCl^zv^^ growth of the original chain

BCl-jClRíGrowth of a new chain where

Cl-R-Cl is 2,5-diochloro-2,5-dimethylhexane (DDH) and M is alpha-methylstyrene (alpha-MeSt).

With increasing monomer consumption, the index M _w /M _n u F^ increased somewhat (see Table III), which indicates the possibility of first forming a polymer of type A with the structure Cl-RM(M) _n -Cl (i.e., chain growth occurs only on one side of the initiation center) and later forming a polymer of type B with the structure Cl-M(M) _m MRM(M) _n ^M- Cl (i.e., chain growth also occurs on the other side of the initiation center, where m = n or m / n) and the resulting polymer is then a mixture of them (i.e., A + B).

Table III and ^f n ^F V P mol.10^ b wt· % fl g/mol ^fl w g/mol JT7TJ w n ^H n.l0 ^-4 g/mol mol.10 ³ 3.84 55.1 1,750 2,315 1.4 5.2 1.50 5.76 63.6 1,910 2,740 1.4 5.3 2.30 7.68 72.5 2,389 3,983 1.7 5.4 2.80 9.60 80.7 3,010 5,737 1.9 5.4 3.08 11.52 82.0 3,900 8,042 2.1 5.4 2.90 12.67 84.3 3,985 8 288 2.1 5.6 3.20 14.21 86.6 4,481 9,049 2.0 5.7 3.28 - and it is amount consumed monomer, b - mass ratio F^/(F^ + Fy), . (M _w /«n>: - 1.5, general convention 100%.

Under the same experimental conditions, the same concentration of BC1 ₃ during continuous dosing of CHjC^ solution of alpha-MeSt into freshly prepared CI^Cl^ solution of BCl^ (the initiation system does not contain DDH, i.e. binifer, and therefore protonic initiation by residual HjO of the reaction system is assumed), two polymer fractions F _N and F _v were also formed, in which, however, the molecular weight did not increase with monomer consumption, i.e. quasiliving polymerization did not occur. Only the mass content of F^ in the polymer samples taken increased, as can be seen from the GPC differential molecular weight distributions shown in Fig. 5.

Example 4

The polymerization of alpha-methylstyrene (alpha-MeSt) was carried out at a temperature of -20 °C by continuous dosing of the CHjClj monomer solution into the solution of initiation system II using the same concentrations (DDH, BC1,), the method of preparation of initiation system II and the dosing rate -3 ^J (1.91.10 mol alpha-MeSt/min) as in Example 3. During the continuous dosing of the monomer into the reaction system, a polymer with a very narrow polydispersity index with M _w /M _n =1/1 was formed, as can be seen from Table IV and from the GPC differential molecular weight distributions shown in Fig. 6. During the quasiliving polymerization of alpha-MeSt after /in 80 minutes of monomer dosing, the number of polymer molecules jjp] increased in the interval from 4.58.10 ^-3 to 15.28.10 ^-3 mol alpha-MeSt only 2.5 times, as can be seen from Table IV.

Table IV

and ^F N 0 mol.10 ³ b M g/mol g/mol mol.lO ² wt. % 4.58 90.0 1,433 1,673 1.2 3.80 5.76 93.7 1,454 1,637 1.1 4.68 7.68 95.7 1,479 1,661 1.1 6.14 9.60 97.9 1,505 1,690 1.1 7.54 11.52 98.5 1,540 1,739 1.1 8.34 13.37 100 1,550 1,705 1.1 10.20 15.28 100 1,859 2,042 1.1 9.70

a - is the amount of monomer consumed, b - is the mass ratio F^(F^+F^), total conversion ¹⁰⁰ *' ^M n(F _v ) ^{= 11,000 with index} V ^S n ^{= X} ' ³ ' ® = <®F ⁺ ĚJp '·

Example 5

The polymerization of alpha-MeSt was carried out at a temperature of -30 °C by the method described in Example 1, namely a) in 30 ml of CH ₂ Cl ₂ /heptane (50/50 v/v) with a concentration of [alpha-MeSt] = 1 mol/l; b) in 12 g of alpha-MeSt. The polymerizations were initiated by initiation system II using colored CH ₂ Cl ₂ solutions of DDH with BCl^ with a concentration of j^BCl^] = 5.10 ³ mol/l with a molar ratio of [bcI/J / DDH = = 0.5; 1; 4; 15 and 20. The DDH solutions with BCl^ were stored at room temperature for 1, 2, 4 and 10 days and then used for initiation. 70 to 100% conversion was achieved after 30 minutes of polymerization at M _n = 3.5.10 ³ to 5.10 ³ .

Example 6

The polymerization of styrene was carried out at 0 °C by the method described in Example 1, namely a) in 30 ml of CHCl; b) in 50 ml of CHCl/heptane (60/40 v/v) with a concentration of styrene = 1 mol/l.

The polymerizations were initiated with initiation system II described in Example 5. 55 to 80%

- 3 3 conversion was achieved after 30 minutes of polymerization at =® 1.6.10 to 2.2.10 .

Example 7

The copolymerization of alpha-methylstyrene with styrene was carried out at a temperature of -78 °C by the method described in Example 1 in 30 ml CH2Cl2 with a concentration of [alpha-MeSt] - 0.8 mol/l with fst = 0.2 mol/l (total concentration of the monomer mixture = 1 mol/l). The polymerizations were initiated with the initiation system II described in Example 5. 95 to 100% conversion was achieved after 20 minutes of polymerization at M _n = 1.9.10 ⁴ to 2.5.10 ⁴ .

Example 8

The polymerization of styrene (a) and the copolymerization of styrene with alpha-MeSt (b) were carried out at a temperature of -50 °C by continuous dosing of CH^Cl^ monomer solution/monomer mixture into the solution of initiation system II described in example 3. The concentration of monomers (a) £stj « 1.91 mol/1; in the case of (b) Jj3tJ = 1.0 mol/1 and [alpha-MeSt] = 0.91 mol/1. In both cases (a), (b), the dosing rate was the same = 1.91 mol St/min or 1.91 mol (St+lafa-MeSt)/min. During the continuous dosing of styrene or the mixture of styrene with alpha-MeSt, quasiliving polymerization/copolymerization took place up to 100% conversion. After 80 minutes of continuous dosing of monomer/monomer mixture, low transfer was demonstrated, the number of polymer molecules [KJ] increased by 2.2 times (in the interval from 3.8.10 to 15.3.10 _mol of monomers).

Claims (3)

SUBJECT OF THE INVENTION A process for the cationic polymerization and copolymerization of vinyl aromatic hydrocarbons, characterized in that the polymerization or copolymerization is carried out at a temperature of 20 to -80 ° C in the presence of the 2,5-dichloro-2,5-dimethylhexane / boron trichloride initiation system, The amount of 5-dichloro-2,5-dimethylhexane to boron trichloride ranges from 2.5 to 5, optionally in an environment of polar halogenated solvents or mixtures thereof with non-polar solvents. 2. A process according to claim 1, wherein the monomer or monomer mixture is continuously metered into a preformed solution of the initiator system, wherein quasiliving polymerization or copolymerization is carried out in which the molecular weight of the monomer-consuming polymer or copolymer increases. 3. Process according to claim 1, characterized in that chlorine solvents such as methylene chloride, methyl chloride, ethyl chloride or mixtures thereof with non-polar solvents such as aliphatic solvents such as heptane or hexane are used as polar solvents.