Polymerization of monomers containing functional groups protected by trialkylsilyl groups. II: Synthesis of poly[2-(4-vinylphenyl)-ethanol] by anionic living polymerization

Polymerization of monomers containing functional groups protected by trialkylsilyl groups: 2*. Synthesis of poly[2-(4-vinylphenyl)-ethanol] by anionic living polymerization Akita Hirao, Katsuhiko Takenaka, Kazuo Yamaguohi, Seii hi Naltahama and Noboru Yarnazaki Department of Polymer Science and Technology, Faculty of Engineering, Tokyo Institute of Technology, Oirolmyama, Megula-ku, Tokyo 152, Japan (Received 17 January 1983; revised 72 February 1983) Foly[2— (4—viny|phenyl)ethanol]s of known chain lengths and of narrow molecularweight distributions have been synthesrxed by means of an anionic living polymerization of the corresponding tri- methylsilylated monomer, 2-(4-viny|phenyl)ethoxy-(trImethy|)si|ane, followed by acid hydrolysis. A block copolvmer ol poly[2-(4-vinylphenyl)ethanol-b-styrene—b-]2-(4-vInylphenyl)ethano| has also been prepared using living polystyryldianion as the initiator. Keywords Fo|y[2-(4-viny|pheny|)ethano|]; living polymer; block copolymer; 2-(4-viny|pheny|)- ethoxy(trimethyI)siIane; ENOFIIC polymerization INTRODUCTION The method of anionic living polymerization presents the advantage of synthesis of linear polymers and block copolyrners with a high degree of structural perfection. However. this very ellicient method cannot be directly applied to the polymerization of monomers with ‘active‘ protons, such as hydroxyl and amino protons. which react immediately with anionic initiators. By suitably blocking such reactive groups, it may be possible to realize the anionic polymerization of these monomers. In a previous paper‘, we found that by blocking the phenolic proton of 4-vinylphenol by (er!- butyldimethylsilyl function, anionic polymerization of this silylated monomer proceeded without chain transfer and termination reactions. By subsequent acid hy- drolysis of the resulting polymer, a linear poly(4- vinylphenol) of known molecular weight and of narrow molecular weight distribution has been obtained in quantitative yield‘. As a part ofa series of studies using silyl protected monomers, this report describes a syn- thesis of 2-(4-vinylphenobethoxyttrimethyl)silane, the al- coholic hydroxyl group of which. is blocked by a tri- methylsilyl group. This report presents some preli- minary information on the attempts to carry out the anionic living polymerimtion of this monomer. EXPER IM ENTAL Materials 2—(4-vinylphenyllethanol was prepared from 4- vinylphenyl-magnesium chloride‘ and ethylene oxide in THF by adaptation of a known procedure’. The crude product was purified by a fractional distillation; yield: 72%; bp. 30°C/2.0 mbar (literature3 107°- 1l4°C/3.5 mmHg)i 2-(4-vinylphenyl)ethoxy(trimethyl)- silane(l) was prepared from 8.0 g (55 mmol) 2-(4- vinylphenyl)ethanol and 9.6 g (60 mmol) hexamethyldi- silazane under a nitrogen atmosphere at 30°C for 10 h. The crude product was purified by a fractional distilla- ‘ Part 1: Hirao, A.. Yamaguchi, K.. Takenaka, ., Suzuki, K. Nnltaltalllfl. S. and Yalnnnaki, .. Makroniol. Chem. Rapid Commun. 1982. 3» 941 D263 6476/B3/l 10339-03S03.(X) © 1983 Blltterworth & Co. (Publishers) Ltd. tion; yield: 95%; b. p. 73“ ~75°C per 20 mbar, ‘H n.m.r.: a=o.24 (s, 9H. osH3H3). 2.93 (L 2H, 1:7 Hz, —C,,H.£lj14IH; ). 3.68 (L 2H, 4:7 Hz, 4I[;l2 0- Si—J, 5.32--5.86 (29. 2H. 1: 10, 18 Hz, Ci_-l,= CH—), 6.87 (24, in. cr;i=cH,). 7.29~7.5l at 4H, 1:9 Hz, C6l;l4. :3, lg). Tetrahydrofuran was used as solvent in all polymerization experiments. It was distilled from sodium wire and then from sodium naphthalide solution. Lithium naphthalide was prepared from 1.28 g (10 mmol) naphthalene and 0.69 g (100 mg-atom) lithium metal in 50 ml tetrahydrofuran at 20°C for 10 h. The reaction mixture was filtered and the green-coloured filtrate was titrated by using n-octanol in tetrahydrofuran. All the operations were carried out in reactors with breakseals under high vacuum (~ 10" mbar). Palymerizarians Anionic polymerizations were carried out under high vacuum (~l0‘°mbar) in sealed glass reactors with breakseals by the method similar to that previously reported by Morton. Milkovich, McIntyre and Brad- ley‘. The reaction mixture was shaken and allowed to stand at —78°C for 1h. The polymers were precipitated, after quenching with methanol—2N HCI (1/1, v/v), by addition to an excess of water. They were filtered, redissolved in methanol, and precipitated into water two additional times and were dissolved in dioxane and dried by freeze-drying. Acetylalizm ofpoly[2-(4-vinylphenyllcrhanol] To 0.5 g polymer in 6ml dry pyridine under a nitrogen atomosphere, 3ml acetic anhydride was added over 30min period at 0°C. After the addition was oomplete. the reaction mixture was stirred at 20"C for 48 h. The reaction mixture was poured into water and the polymer precipitated was purified by filtration. The polymer was redissolved in tetrahydrofuran and precipitated into methanol two additional times and was then freeze- dried. The ‘H n.m.r. spectrum of the resulting polymer indicates complete acetylation of poly[2-(4- vinylphenyllethanol]. POLYMER COMMUNICATIONS, 1983, Vol 24, November 339 Fa/y[2-(4-viny/plreny/)-ethano/] by anionic living polymerization: A. Hirao et al. Measurements The infra-red (in) spectra were run by using a JASCO IR-G spectrophotometer. ‘H nmr. spectra were re- corded with Hitachi JNM-PMX60. Gel permeation ch- romatograms (g.p.c.) were obtained using a Toyosoda HLC-802 instrument with u.v, detection, tetrahydro- furan being the elution solvent. Vapour pressure os- mometry (v.p.0.) measurements were made with CO- RONA 1l7 in benzene solution. RESULTS AND DISCUSSION The starting monomer (1) was readily prepared by treating 2-(4-vinylpheny|)ethanol with a slight excess of hexamethyldisilazane giving an excellent yield. Anionic CH2=CH CH3 CH2CH3OS‘l—CH3 CH3 ll) polymerization of l with lithium naphthalide was in- vestigated in tetrahydrofuran at -78 ‘C. Ready in- itiation was observed by an immediate colour change from green to orange-red, similar to that observed in the well known living polymerization of styrene’, The colouration remained unchanged at —78°C for 1 h. The effect of temperature on the polymerization was critical, however. With raising the temperature to 20°C, it was found that the orange-red colour gradually faded. This is presumably ascribed to the attack of the silicon atom of the protecting group by the carbanion of the polymer end. Alter quenching the system with methanol—2N HCl (1/1, V/V). the polymer was precipitated by addition to an excess of water. The removal of the trimethylsilyl group by the above treatment was confirmed by the ‘H n.m.r. and i.r. spectra of the resulting polymer. The resulting polymer, therefore. should have been in the form of poly[2-(4-vinylphenyl)ethanol], ‘H n.m.r. and it. spectra of which displayed signals and absorptions of the expec- ted struclure. The poly[2-[4-vinylphenyl)ethanol] thus obtained is a white solid, soluble in methanol, ethanol, 1.4-dioxane, and pyridine, but insoluble in benzene, tetrahydrofuran. chloroform, and water. In order to determine the molecular weight and its distribution of the polymer by v.p.o. and g,p.c. measure- ments, the polymer was esterified with acetic anhydride in pyridine to afford the poly[2-(4-vinylphenyliethyl ace- tate] which was soluble in benzene and tetrahydrofuran. A ratio of ‘H n.m.r. peak integrals (integral of aromatic peak to that of methyl peak of acetoxy group} of an acetylated polymer indicated a full degree of esterifi- cation of the starting poly[2-[4-vinylphenyllethanol]. As shown in Table I, there is fair agreement between the values for the acetylated polymers measured by v.p.o. and the calculated values based on the initial monomer to initiator ratio. The g.p.c. curve indicates that the polymer possesses a narrow molecular weight distribution. The value of MW/M, is estimated to be around 1.1 in comparison with that of polystyrene standard sample (1171,,/M,,= 1.04) as illustrated in Figure: I and 2, respectively. These facts clearly indicate the rapid initiation and the absence of chain transfer and termination reactions during the course of the anionic polymerization of 1. It follows that a polymer of any desired molecular weight can be made in this system. It is possible that the utilization of living polystyryl anion as an initiator of polymerization of a second monomer I results in the preparation of new interesting block copolymers containing hydrophilic poly[2-[4- vinylphenyljelhanol] units. When 1 was added to the living polymeric dianion of styrene, initially prepared with lithium naphthalide in tetrahydrofuran at —78"C, the viscosity increased and a quantitative yield of tetra- 25 30 COUNT 35 40 ngm 1 Molecular weight distribution ror p0IV[2-(4-Vlny|- phenV|)e(hInDl] M,, obsvd (v.p.o. =1sooo Tablet Anionic polymerization or 2-(4-virlylphenyllethoxyltrimethyllsilane (1) with lithium naphthalide in tetiariydrolursn at —7s°c lor t it‘ ill Litnium iianrtrnalide Conversion lniirioll lirimcil) (as) W” A7,, calcdc ii" obsvit” lD.6iB 0.300 IUD 71.2 l35DU i l6lU0 i 5.20 Cl.l25 ‘I00 53.2 lsaoo 13000 24.05 0.355 too 132 25100 27 zoo 3 Monomer/Solvent (t :10, by volume) Degree at polymerization calculated ray 2 x [monomer] /[initiator] 9 Calculated fol polymer repeating units or Tlflrvlnylphenvllethyl acetate vapour pressure osmorrletrv in benzene 340 POLYMER COMMUNICATIONS, 1983, Vol 24, November Poly[2-(4-viny/phenyl)-ethanol] by anionic living po/ymeIi1atinn.'A. Hirao et al. fable 2 Block copolvmevizarion of styrene with 2—l4—vlnylphenVli!thoxV—(tvirnethylisllane (1) by use of polystyryl dianion“ Styrene (I) Llthlum nanhrhallde Yield i _ Addltlon lmmall lmmall (mmoll (96) A4,, calcd M,, obsvd Fivsr s.44 — 0.0730 I00 18 mo lsoood Second” 3.94 s.oa 0.|0I loo as 000‘ 33 coo” 3 All polymerlzauons were named out ln tetrahydrofuran at —78°(: to: I n (first polymerization) and for 1 n [second polymerization) 5 6.08 mmol 2-[4-vinylphenvllethoxyltrlmethyllsllane was added to a reaction mixture of 8.94 mmol styrene and o.lo1 mmol llmlum naphthalide 2 x 3.94 2 x 6.08 9 Calculated by 0 ‘O. x [styrene molecular welgm) + x llll molecular weight! '1 Gel permeation cttromaragram usmg standard polystyrene callbration curve 9 Estlmated Ivorrl ma copolymer composition which was determlnad by 1H n.m.r. 25 35 40 3° coum Figure 2 _ Molecular weight distribution for standard polystyrene sample. M,,=19750, M,/M,,=I.O-1 hydrofuran soluble polymer was obtained. The result of the block copolymerization is summarized in ‘Rzble 2 and the g.p.c. curves are shown in Figure 3. As can be seen the g.ple. curves show that the peak of starting polystyrene shifts completely towards the higher mole- cular weights after addition of] and that the resulting block copolymer possesses a single peak with a narrow molecular weight distribution, The observed value of M, of the final polymer estimated by ‘H n.m.r. from its composition was in reasonable agreement with that expected from the initiator to monomer ratio. These results indicate that the block copolymcrization is 30 35 25 COUNY Fiyure 3 Molecular weight distvlbutlons for polystyrene initially polymerized, A; and tor block copolymer, E carried out elliciently. A detailed study of the charac- terization of poly[2-(4-vinylphenynethanol] and block copolymers containing the poly[2-(4—vinylphenyl)~ ethanol] units is under investigation. REFER ENCES l Hirao. »\., Yamaguchl, K.. Takenaka. K., Stmrki. K., Nakahama. S. and Vamazaki. N. Makmmol. Chrml Rapid Cnrnmun. I932, 3, 941 2 Lccbrick. R. and Rams/den, H. E J‘ Org. Chem. I958. 13, 953 3 Tammola, S. and Oda. R. Kagva Kagaku Ztzxxhi 1961. 69. 932 4 Morton, M. M., Mllkovtch. R., Mclnlyrc, D. B. and Bradley, L. J. I. Palym. Sci. A. 1963. 1,443 5 Fctlcrs, L. J. J Palyrn Sci. C. 1969, 26. 1 POLYMER COMMUNICATIONS, 1983, Vol 24, November 341 polymer communications UK Associate Editor, POL YMER COMMUNICA TIONS R. Epton DSt:, PhD Department ol Physical Sciences, Wolverhampton Polytechnic, Wolverhampton WV1 1LY EDITORS Sir G. Allen FRS, PhD, FPR|', F|nstP Unilever FLC, PO Box 68, Unilever House, Blackirlars London EC4 C. H. Bamford FRS, PhD. SCD Proiessor, Biomedical Engineering and Medical Physics unit, Faculty or Medicine, Duncan Building, University at Liverpool, Liverpool L69 3BX c. E. H. Bawn CBE, FRS Springllelds, Stoodleigh, Tlverton, Devon EX16 BPT J. K. Gillham PhD Prolessor, Polymer Materials Program Department or Chemical Engineering Princeton University, Princeton, NJ 05540, USA F, D. Hartley MA Professor, Department at Polymer and Fibre Science, UMIST, PO Box 88, Sackvllle Street, Manchester M60 1 OD M. Hirooka Senior Research Associate, Central Research Laboratory. Sumltomo Chemical Company. 240, Tsukahaia, Takatsukl, Osaka 569, Japan Associate Editor, Japan Y. lmanishi Prolesscri, Department at Polymer chemistry, Kyoto University, Kyoto 506, Japan 3. R. Jennings Proressor oi Physics, Brunel University, Uxbiidge, Mlddlesex UE5 3PH US Associate Editor of POLYMER and POLYMER CDMMUN/CA 7/ONS R. K. Eby PhD Cltiel Polymer Science and Standards Division, National Bureau ol Standards, Washington DC 20234, USA Telephone laoli 3213734 H. Kawai Piolessor oi Polymer Chemistry, Department or Polymer Cherrttsiry. Kyoto University, Kyoto 606, Japan A. Ladwith DSc, PhD Depanment or lPl Chemistry, University or Liverpool. P 0 Box in, Liverpool L69 35x bl W. McCall PhD Director, Chemical Research Laboratory, Bell Laboratories, Murray Hill, NJ 07974, US/1 A. Peterlin PhD Polymer Science and Standards. Naticlnal Bureau OI Standards. Washington DC 20234, USA J. C. Salamone Prolessor or Chemistry, Dean College ol Pure and Applied Science, University ol Lowell, Lowell, Massachusetts 01854, USA 0. Vogl PhD Herman F. Mark Frolessoi OI Polymer Science. Polytechnic Institute ol New York, New York ll20l, USA I. M. Ward FRS, DPhi|, FPRI, Flnst P Professor at Physics, University at Leeds, Leeds LS2 SJT J. G, Williams DSc(Eng), PhD, FEng. FPRI Professor cl Polymer Engineering, Department or Mechanical Engineering, lrnpeilal College, London SW7 ZBX INTERNATIONAL ADVISORY BOARD s. L Aggarwal PhD General Tile and Rubber Company, Akron Dhto 44329, USA M. C. Benoit PhD Direcleur, Centre de Recrietcries sut Ies Macromolecules, CNRS, 67083 Strasbourg, France 5. ivwater PhD National Research Council, Ottawa KIA OHS, Canada F, Danusso PhD Dipartlrtlerlto dl chtmtca lndustriala ad lngegneiia Chlmltz del Polltecnicc, ZOI33 Mllano, ltaly K. L, Devrias PhD Department ol Mechanical and Industrial Engineering, University ol Utah, Salt Lake CiIYt Utah sailz, USA D. liailtens Laboratory ai Polymer Technology Elndhoverl Llntyerstty ol Technology, The Netherlands M. Morton PhD Director, Institute DI Polymer Science, university ol Akron. Akron, Ohio 44325, USA A. M. Not-tit FRSE, Pho. Dsc Asian institute ol Technology, Bangkok, Thialand N. Ringsdort lnstitut iur Oigarllscne chemtc, Johannes eutenperquniyersitat, D-S500 Malriz, West Germany M. Szwart: FFIS, PhD I176 Santa Lousa Drive, solana Beach, Calilornla 92075. 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