Synthesis of High-Molecular Weight Poly(Vinyl Alcohol) of Various Tactic Contents Through Photo-Emulsion Copolymerization of Vinyl Acetate and Vinyl Pivalate
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Polymer Journal, Vol. 24, No. I, pp 115-119 (1992) Synthesis of High-Molecular Weight Poly(vinyl alcohol) of Various Tactic Contents through Photo-Emulsion Copolymerization of Vinyl Acetate and Vinyl Pivalate Tohei YAMAMOTO, Ryohei FuKAE,* Tomoaki SAso, Osamu SANGEN, Mikiharu KAMACHI,** Toshiaki SATo,*** and Yoshiharu FUKUNISHI*** Faculty of Engineering, Himeji Institute of Technology, Shosha, Himeji 671-22, Japan * Himeji Junior College, Shinzaikehonmachi, Himeji 670, Japan **Faculty of Science, Osaka University, Machikaneyama, Toyonaka 560, Japan ***Central Research Laboratories, KURARA Y Co., Ltd., Sakazu, Kurashiki 710, Japan (Received July 2, 1991) ABSTRACT: Photo-emulsion copolymerizations of vinyl acetate (VAc) and vinyl pivalate (VP) were carried out without initiator at ooc, and copolymers giving high molecular weight poly( vinyl alcohol) (PYA) with various tacticities were obtained. The tacticities could be controlled between 22.3-12.8% for the isotactic triad and 27.7-38.3% for the syndiotactic triad by varying feed monomer composition. KEY WORDS Control of Tacticity I Poly( vinyl alcohol) I Photo-Emulsion Copolymerization I Vinyl Acetate I Vinyl Pivalate I Saponification 1 High molecular weight poly(vinyl alcohol) obtained through radical polymerization. 3 As (PV A) is expected to be useful as hydrophilic some investigators reported that bulky ester material such as fiber, film, and gel. However, group of monomer yielded high syndiotactic it is difficult to obtain a high molecular weight PV A, 4 - 6 the highest syndiotacticity was due PV A, because frequent chain transfer reactions to the steric hindrance oft-butyl group of VP. occur in the radical polymerization of vinyl The physical properties of PVA with high acetate (VAc) to prepare poly(VAc) as the syndiotacticity were different from those of precursor of PVA. To suppress the chain usual PVA, 7 and we were interested in the re transfer reactions, we carried out photo lations between physical properties of PV As emulsion polymerization of vinyl esters at low and their tacticities. In order to investigate the temperature in the absence of initiator, and relation, we tried to obtain PVAs with various high molecular weight poly( vinyl ester)s giving tacticity. This paper presents the synthesis high molecular weight PYAs were obtained. 1 •2 of high molecular weight PVAs with various The triad tacticities of PVA from poly(vinyl tacticities through photo-emulsion copolym acetate) (PVAc) for isotactic (I), heterotactic erizations of V Ac and VP. (H), and syndiotactic (S) were 22.3, 50.0, and 27.7%, respectively, and the PVA was almost EXPERIMENTAL atactic. On the other hand the tacticity of PVA from poly(vinyl pivalate) (PVP) for I, H, and Materials S was 12.8, 48.9, and 38.3%, respectively, and VAc and VP were purified by washing with the syndiotacticity was the highest for PVA an aqueous solution of NaHS03 , drying over 115 T. YAMAMOTO et a/. Table I. Effect of LWZ on photo-emulsion Table II. Results of photo-emulsion copolymerization copolymerization of VAc and VP without of VAc and VP at ooc without initiator' initiator at 0°C' ---- ---- -- - Yield Copolymer VAc mol% VAc VP LWZ Yield ---··· ['l]b in feed ··--·- [ 'l]b g C% VAc mol% mol% mol% ml g ---·-· ------ ------ 100 3.813 100 4.25 100 0 0.1 3.209 4.86 86.5 2.602 59.1 74.3 5.18 0.3 3.222 4.25 70.5 1.350 59.4 71.4 5.06 0.5 3.813 4.25 61.6 1.285 60.8 57.9 4.97 0.7 3.843 3.97 51.7 1.692 60.6 60.3 5.73 ------ -··- 28.6 2.036 63.1 33.0 5.30 86.5 13.5 0.2 0.176 4.56 15.2 1.954 63.4 29.2 5.51 0.3 1.602 4.62 0.0 2.414 0.0 3.36 0.5 2.602 5.18 0.7 1.809 4.21 a Total feed monomers, 5ml; LWZ amount, 0.5ml; --·- .. irradiation, 20 h. 51.7 48.3 0.2 0.837 5.22 b Determined in benzene at 30"C. 0.3 1.291 5.53 0.5 1.692 5.73 0.7 2.421 4.87 mer was reprecipitated from methanol and ---- water, and dried under vacuum at 60°C. 0 100 0.2 0.944 3.27' 0.3 1.427 3.59' Copolymer composition was determined by 0.5 2.414 3.76' measuring carbon content with a Yanagimoto 0.7 1.166 3.36' Model MP-11 element analyzer. ' Total feed monomers, 5 ml; irradiation, 20 h. h Determined in benzene at 30oC. Saponification of Copolymer ' Determined in acetone at 25oC. Copolymers were saponified by the usual method for PV Ac and by a method developed 8 anhydrous CaC1 2 and distilling under nitrogen for PVP. In a 300 ml separable flask equipped atmosphere at reduced pressure. Distilled with a reflux condenser and a dropping funnel water was used as a medium. Polyoxyethyl 2.0 g of copolymer were dissolved in 200 ml of enenonylphenylether sodium sulfate (LWZ; tetrahydrofuran. Then the solution and 20 ml Kao Co.) was used as an emulsifier without of 25% KOH methanol solution were flushed further purification. with nitrogen. With stirring, the KOH solu tion was added gradually to the copolymer Copolymerizations solution and the mixture was kept at 60oC for In a 30 ml Pyrex Kjeldahl flask fixed 15 min under nitrogen atmosphere. Then the amounts of V Ac, VP, and LWZ, and I 0 ml of precipitate was filtered, washed with methanol water were charged. The mixture was degassed and dried under vacuum. and the flask was sealed under vacuum. The flask was placed in a water-ethylene glycol Acetylation of PVA bath at 0°C, and the mixture was stirred with In a three necked flask were placed I g a Teflon bar and irradiated with a high of PV A, 2 ml (25 mmol) of pyridine, 20 ml pressure mercury lamp for 20 h. Then the (0.2 mol) of acetic anhydride, and 20 ml (0.35 mixture was poured into 150ml of water and mol) of acetic acid and the mixture was stirred Na2 S04 was added gradually with stirring at I oooc for 72 h. Then the mixture was until the emulsion was broken and the polymer poured into cold water to precipitate PV Ac. was precipitated. After filtration, the copoly- The PV Ac was filtered, purified by repeating 116 Polym. 1., Vol. 24. No. I, 1992 Control of Tacticity of PV A lOOr-----------. H20 Q_ 0 • CH 2 u • .f.; • • O:so0 E u :§; • 0 ppm Figure 2. 1 H NMR spectrum of PV A obtained from VAc mol% in feed VAc-VP copolymer by saponification with NaOH in methanol for 5 h at room temp. Figure I. Composition diagram for the photo-emulsion copolymerization of V Ac with VP at O"C. reprecipitation from methanol and water, and HzO DMSO dried under vacuum. Determination of Pn and Tacticity P" of PV A from the copolymer was calcu lated on the molecular weight of acetylated PV A which was determined from the intrinsic viscosity measured in benzene at 30oC. The 1 H NMR spectra of PV As from Figure 3. 1 H NMR spectrum of PVA obtained from copolymers were measured by a JEOL JNM VAc -VP copolymer by saponification with KOH in GX-400. The triad tacticity, and degree of tetrahydrofuran for 15min at 60'C. saponification were determined from the spectra. copolymers have large P", and PYAs of a high RESULTS AND DISCUSSION molecular weight are expected to be derived from them. Effect of L WZ on the Copolymerization Plots of copolymer composition against Mixtures ofVAc, VP, LWZ, and water were monomer composition are shown in Figure I, irradiated using a high pressure mercury lamp and it is found that random copolymerization at ooc for 20 h, and copolymers were obtained takes place. in all runs (Table 1). When 0.2 ml of L WZ was added, ['7] was large enough, but yield was Saponification of Copolymer very small with 86.5 and 51.7mol% of feed All copolymers were dissolved in methanol V Ac. When 0.5 ml of L WZ was added, both and then treated with aquaous NaOH solution yield and ['7] were large enough. With 0.7ml for 5 h at room temperature. White gelatinous ['7] became smaller. So further copolymeriza products were obtained, filtered, washed with tions were carried out with 0.5 ml of LWZ. methanol and dried under vacuum. A typical example of 1 H NMR spectra of the products Photo-Emulsion Copolymerization is shown in Figure 2. From the figure, it is Copolymers of V Ac and VP were obtained found that all V Ac units were saponified in good yields (Table II). Large values ( ==; 5) but VP units are not saponified completely. of ['7] of the copolymers indicate that the Although we could not saponify copolymers Polym. J., Vol. 24, No. I, 1992 117 T. YAMAMOTO et a/. Table III. OS, P •• and tacticity of PV As obtained from copolymers of V Ac and VP' ------------- OS Triad/% Diad/% VAc mol% P. in feed % I H s s 100 99.7 12400 22.3 50.0 27.7 47.3 52.7 93.5 99.4 21.5 50.3 28.2 46.6 53.4 86.5 99.3 18.5 51.4 30.1 44.2 55.8 70.5 99.9 8300 18.1 51.5 30.4 43.9 56.1 61.6 99.7 5400 16.3 50.9 32.8 41.8 58.2 51.7 99.8 6000 14.2 51.6 34.2 40.0 60.0 40.8 99.7 12.9 51.8 35.3 38.8 61.2 28.6 98.9 12000 12.9 52.1 35.0 38.9 6l.l 0.0 99 18000 12.8 48.9 38.3 37.2 62.8 ' Copolymerization conditions: see Table II.