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Synthesis of New Linear Polymers Containing Thiocarbonyl Groups: Polyaddition of Dicarbothioic Acid to Diolefins

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Synthesis of New Linear Polymers Containing Thiocarbonyl Groups: Polyaddition of Dicarbothioic Acid to Diolefins Polymer Journal, Vol. 26, No. 1, pp 49-59 (1994) Synthesis of New Linear Polymers Containing Thiocarbonyl Groups: Polyaddition of Dicarbothioic Acid to Diolefins Eiichi KOBAYASHI,* Kazuyoshi TENDO, Masato KATO, and Sadahito AoSHIMA Department of Industrial Chemistry, Faculty of Science and Technology, Science University of Tokyo, Noda, Chiba 278, Japan (Received May 24, 1993) ABSTRACT: The polyaddition of 1,4-benzenedicarbothioic acid to 1,4-divinylbenzene or 1,4-diisopropenylbenzene was carried out at 70°C in toluene under a nitrogen atmosphere by radical mode such as by addition of AIBN or UV irradiation. Both diolefin compounds gave polymers in a 90% yield. The polymer obtained from I ,4-diisopropenylbenzene was soluble in chloroform, and the molecular weight of the polymer (Mw) was 40000. On the other hand, the polymer obtained from 1,4-divinylbenzene was partly soluble in conventional organic solvents, possibly due to a cross linkage formation by a pendant vinyl group. The model addition reaction of thiobenzoic acid to styrene gave a by-product ca. 8% being the I : 2 adduct with respect to thiobenzoic acid and styrene. Alkali hydrolysis of both polymers was investigated to confirm the cross linkage structures in the polymers. KEY WORDS Polyaddition / Polythioester / Addition Reaction/ Hydrolysis / 1,4-Benzenedicarbothioic Acid / 1,4-Divinylbenzene / 1,4-Diisoprope­ nylbenzene / Thiobenzoic Acid/ Styrene/ oc-Methylstyrene / Addition reactions of carbothioic acids to (nb8 = 1.81) and exhibited the reversible phase olefins occur easily and are used to prepare transition by heat mode. various thioesters or polythioesters. For CH2=CH-<Q)--CH=CH2 + HS-<Q)--SH R or UV example, Ipatieff et al. 1 and Crouch et al. 2 synthesized thioesters by radical addition reaction of thioacetic acid to olefins. Marvel et (1) al. reported the syntheses of various poly­ thioesters by radical polya_ddition of di­ The authors synthesized new saturated carbothioic acids to diolefins. 3 polymers containing the thioester bond instead Recently, the authors investigated the radical of the thioether bond. The introduction of polyaddition of 1,4-benzenedithiol to 1,4- carbonyl groups to the poly(thioethers) may divinylbenzene (DVB) as shown in eq 1. 4 •5 It increase intermolecular interactions between took place readily in solution under UV polymers. By variation of the intermolecular irradiation or in the presence of a radical interactions, thermal properties, and liquid initiator such as AIBN. The obtained polymer crystalline properties of the poly( thioethers) had a linear structure with high molecular may be improved. Thus, 1,4-benzenedicar­ weight (Mw=3OOO0-10OOOO). Interestingly, bothioic acid (BDTC) was polymerized with the polymer had a high refractive index DVB or 1,4-diisopropenylbenzene (DIPB) to * To whom all correspondence should be addressed. 49 E. KOBAYASHI et al. obtain new saturated polymers as shown in eq imately 7. It was dried over anhydrous calcium 2. The addition reaction of thiobenzoic acid chloride in vacuo at room temperature for (TBA) to styrene (St) or c,:-methylstyrene (MSt) about 12 h. The product was purified by sub­ was also investigated as a model of the limation at 100°C under 0.1--0.05 mmHg. polyaddition of BDTC to DVB or DIPB. In BDTC was obtained in a 96% yield as a yel­ addition, the hydrolysis of the obtained low solid, mp 127.5-127.7°C (lit. 7 127.0- polymers was investigated in order to make 127.50C). DVB was provided by Hokko clear their structures. Chemical Co. DIPB (Mitsui Petrochemical Co.), TBA (Tokyo Chemical Industry Co.), f;l f;l R CH 2=C-<Q)--C=CH2 + HSC-{5\r-SH 11'~ MSt (Nacalai Tesque Inc.), and St (Wako Pure 0 0 Chemical Industries) obtained commercially R R fCH,CHUCHCH,scucst- were purified twice by vacuum distillation 0'08 n under a nitrogen atmosphere before use. R=H,CH3 Benzene and toluene (Nacalai Tesque Inc.) as (2) reaction solvents were distilled over calcium hydride. 2,2'-Azobisisobutyronitrile (AIBN, EXPERIMENTAL Wako Pure Chemical Industries) was used as received. A nitrogen gas was purified as shown Reagents in the literature. 8 The authors applied the synthetic method of For hydrolysis, tetrahydrofuran (THF, TBA 6 to the preparation of 1,4-benzenedi­ Nacalai Tesque Inc.), ethanol (Amakasu carbothioic acid (BDTC) (eq 3). In a Chemical Industries), hydrochloric acid (Naca­ suspension of 12.3 g (0.22 mol) of sodium hy- lai Tesque Inc.), chloroform (Nacalai Tesque Inc.), and ion-exchaged water were distilled to c1cu~ Cl _NaSOH > NaSC fc5'r·SNa _!L,. HSC~·SH U in Et H 11 \_\:::'.ft II I\ exclude oxygen under a nitrogen atmosphere 0 0 O O O 0 before use. And powdery sodium hydroxide (3) (Koso Chemical Industries) was heated at 150 °C in vacuo for 3 h to degas before use. Sodium drosulfide (Nacalai Tesque Inc.) dried over tetrahydroborate (Kishida Chemical Co.) was cone. sulfuric acid in 80 ml of anhydrous used as received. ethanol (Nacalai Tesque Inc.), a solution of 10.2 g (0.05 mol) of terephthalyl chloride Polyaddition (Tokyo Chemical Industry Co.) in 100ml Polyaddition was carried out in the presence of anhydrous diethyl ether was added drop­ of AIBN or with UV irradiation in toluene at wise with stirring at 0-5°C under a nitro­ 70°C under a nitrogen atmosphere as described gen atmosphere. The reaction mixture was in the previous papers.4 •5 A typical example stirred at room temperature for 3 h to com­ was as follows: in a pyrex tube equipped with plete the reaction. 100 ml of water were add­ a three-way stopcock, an equimolar amount of ed in the reaction mixture to dissolve the pro­ BDTC and DVB (1.1 mmol, each) in toluene duct. The aqueous layer was washed five (13 ml, 1.2 x 10 - 1 mol) was charged by a times with 50 ml of diethyl ether to remove medical syringe under a nitrogen atmosphere. a trace amount of by-product, ethyl ester, and The polymerization was initiated at 70°C by then 50 ml of 6N hydrochloric acid were added the addition of AIBN (2.2 x 10- 2 mi:nol) in to the aqueous layer on an ice bath. The toluene or with UV irradiation using a 450 W precipitate was recovered by filtration and high pressure mercury lamp (Ushio Co.). The washed with water until the pH was approx- polymerization was terminated by pouring the 50 Polym. J., Vol. 26, No. I, 1994 Synthesis of New Linear Polymers Containing Thiocarbonyl Groups polymerization mixture into a large amount of drous calcium chloride in vacuo at room methanol, then the polymer precipitated was temperature for about 12 h. Terephthalic acid recovered by a centrifugation. After washing was obtained as a white powder and its amount out residual monomers with methanol, the was determined by alkali titration. polymer was dried in vacuo at room tempera­ The filtrate was extracted with three 15 ml ture for 12 hover anhydrous calcium chloride. portions of chloroform under a nitrogen atmosphere. The chloroform layer was dried Model Addition Reaction over anhydrous sodium sulfate at room The addition reaction of TBA (1.0 mo11- 1) temperature for about 12 h. Thiols were to St (1.0moll- 1) or MSt (l.0moll- 1) as a obtained by evaporating the chloroform layer model of the polyaddition was carried out at and their amounts were determined by GPC. 70°C in benzene by the addition of a benzene solution of AIBN (1.0 x 10- 2 or 5.0 x 10- 2 Measurements mol 1- 1) under a nitrogen atmosphere similarly 1 H NMR spectra were obtained with a JEOL as below (see Figure captions for the reaction PMX-60si spectrometer and a JEOL JNM­ conditions such as the concentrations of the FX90Q spectrometer in CDC1 3 with tetra­ reagents). The course of the reaction was mon­ methylsilane as an internai standard. IR itored by measurement of the concentrations spectra were recorded on a Hitachi 260-50 of both monomers by GC using decane or spectrophotometer by the KBr method. Gel trans-decalin as an inten_rnl reference. The ad­ permeation chromatograms (GPC) were mea­ dition product was obtained by removal of sured in chloroform on a Tosoh CCPD dual benzene from the reaction mixture without pump chromatograph with Tosoh TSKgel pretreatment. GMHxL column and JASCO Tri Rotar HPLC chromatograph with Shodex K-2002 column Hydrolysis equipped with a UV /RI dual-mode detector. The alkali hydrolysis of the polymers of Sulfur contents of the polymers and adducts BDTC-DVB (4.9 x 10- 2 repeating unit mol were determined by the modified Schoeniger's 1- 1) and BDTC-DIPB (4.9 x 10- 2 repeating method.9 •10 Gas chromatograms (GC) were unit mo11- 1) was carried out at 40°C for made on a Shimadzu GC-4BMPF equipped 48 h in 0.76N aqueous sodium hydroxide­ with a flame ionization detector (FID) and THF--ethanol (1 : 1 : 0.4) solution in the prese­ Silicone GE SE-30 column (2 m) at 90°C under nce of sodium tetrahydroborate (0.10 mol a nitrogen carrier gas (3 7 ml min - 1 ). CI mass 1- 1) under a nitrogen atmosphere. Since the spectra were obtained with a JEOL JMS­ produced thiols were oxidized easily, the DX300. reductive condition was maintained in the reaction system by the addition of sodium RESULTS AND DISCUSSION tetrahydroborate. After the reaction, to the reaction mixture 6N hydrochloric acid was Polyaddition of BDTC to DVB or DIPB added on an ice bath until the solution became The polyaddition ofBDTC to DVB or DIPB acidic. was carried out in the presence of a con­ The precipitate was recovered by filtration ventional radical initiator AIBN or by UV ir­ under a nitrogen atmosphere.
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