3 Poly(vinyl ether)s, Poly(vinyl ester)s, and Poly(vinyl halogenide)s Oskar Nuyken and Harald Braun Technische Universita ¨ tMu ¨ nchen, Garching, Germany James Crivello Rensselaer Polytechnic Institute, Troy, New York I. POLY(VINYL ETHER)S A. Introduction 1. Definition and Historical Background Vinyl ethers comprise that class of olefinic monomers which possess a double bond situated adjacent to an ether oxygen. These monomers include those compounds which have various substituents attached to the carbon atoms of the double bond as well as the unsubstituted compounds. Due to the presence of the neighboring oxygen atom, the double bond possesses a highly electronegative character, a feature that dominates both the organic and polymer chemistry of these compounds. The analogous vinyl thioethers are also known [1] and their chemistry closely parallels that of their corresponding vinyl ether counterparts. Beginning with the accident al discovery by Wislicenus [2] that elemental iodine catalyzes the violent exothermic polymerization of ethyl vinyl ether, the polymerization of these monomers has been the subject of many investigations over the years and continues to occupy the attention of investigators today. In particular, the field of the cationic polymerization of vinyl ethers is a very lively field engaging the efforts of academic as well as industrial workers. Apart from the interesting chemistry of these compounds, the chief incentive for these efforts is their versatility in a wide variety of technical applications. Among the many uses of poly(vinyl ethers) and their copolymers are applications such as adhesives, surface coatings, lubricants, greases, elastomers, molding compounds, films, thickeners, anticorrosion agents, fiber and textile finishes, and numerous others. Vinyl ether monomers, and their polymerization and copolymerization, have been the subjects of several excellent past reviews [3–7] and some more recent one [8–10]. These reviews have provided a rich source of background material for the present chapter and the reader is referred to them for specific details concerning such topics as manufacturing methods, economics, toxicity, and special applications of poly(vinyl ether) homopolymers and copolymers. Copyright 2005 by Marcel Dekker. All Rights Reserved. 2. Synthesis of Vinyl Ether Monomers Vinyl ether monomers are accessible by a number of synthetic methods. A comprehensive listing of these monomers, their physical characteristics, and their commercial suppliers may be found in the review article by Lorenz [5]. Given below are brief descriptions of the major synthetic methods for the preparation of these compounds, with special emphasis on those developed in the past few years. The oldest, most versatile, and major commercial method for the synthesis of vinyl ethers is by the base-catalyzed condensation of acetylene with alcohols first described by Reppe and co-workers [11–13]. RÀOH þ HC CH ÀÀÀÀÀÀ! MOH 120À180  C ROÀCH ¼ CH 2 ð1Þ Presumably this reaction proceeds by formation of the metal alcoholate, which undergoes nucleophilic addition to the acetylenic double bond. The resulting adduct then regenerates the alcoholate by proton exchange. Sodium and potassium hydroxides are the most common catalysts employed for this reaction. The oxidative vinylation reaction of ethylene with alcohols in the presence of oxygen has been reported [14,15] to give vinyl ethers in high yields. Like many Wacker-type reactions, this reaction is typically catalyzed by heterogeneous and homogeneous catalysts containing palladium. RÀOH þ H 2 C¼CH 2 þ 1=2O 2 À! PdCl 2 , CuCl, HCl RO À CH ¼ CH 2 þ H 2 O ð2Þ While the direct oxidative vinylation reaction shown above has many advantages over the acetylene route to the preparation of vinyl ethers, it has yet to be commercialized. Acetals can be thermally cracked at temperatures between 250 and 400  C over heterogeneous catalysts such as palladium on asbestos [16], thoria [17], or metal sulfates on alumina [18], as shown in the following equation. ð3Þ It is also possible to prepare vinyl ethers by a transvinylation reaction between an alcohol and a vinyl ether as shown in equatio n (4). The reaction can be catalyzed by palladium(II) complexes [19] and by mercury salts [20–23]. ROÀCHþCH 2 þR 0 ÀOH À! cat: R 0 OÀCH ¼ CH 2 þRÀOH ð4Þ This method is especially recommended for the preparation of vinyl ether monomers bearing functional groups that are sensitive to the basic conditions of the vinylation reaction using acetylene. Transvinylation reactions can also be carried out between alcohols and vinyl acetate, a reaction that has been described by Adelman [24] is also being catalyzed by salts of mercury such as mercuric sulfate. H 3 CÀCO 2 ÀCH ¼ CH 2 þRÀOH À! cat: ROÀCH ¼ CH 2 þH 3 CÀCOOH ð5Þ Copyright 2005 by Marcel Dekker. All Rights Reserved. The dehydrochlorination of 1- and 2-chloroalkyl ethers with sodium or potassium hydroxide provides a simple and direct route to the synthesis of the corresponding vinyl ethers [25,26]. It is the method of choice for the preparation of 2-chloroethyl vinyl ether from 2-dichlorodiethyl ether [27,28]. ðClÀCH 2 CH 2 Þ 2 O þ NaOH À! ClÀCH 2 CH 2 ÀOÀCH ¼ CH 2 þ NaCl þ H 2 O ð6Þ The compound shown above, 2-chloroethyl vinyl ether, undergoes facile nucleophilic displacement reactions and can thus be used as a valuable synthon for a variety of specialized vinyl ether monomers [29–31]. ClÀCH 2 CH 2 ÀOÀCH ¼ CH 2 þROHÀÀÀÀÀ! R 0 4 NBr NaOH ROÀCH 2 CH 2 ÀOÀCH ¼ CH 2 þ NaCl ð7Þ Allylic ethers can be conveniently isomerized to the corresponding vinyl ethers in the presence of potassium t-butoxide [32,33] or such transition metal catalysts as tris(triphenylphosphine)-ruthenium dichloride [34]. RO À CH 2 À CH ¼ CH 2 ÀÀÀÀÀÀÀ! tÀBuOK or ðPh 3 PÞ 3 RuCl 2 RO À CH ¼ CH À CH 3 ð8Þ Finally, there are cyclic vinyl ethers, such as 2,3-dihydrofuran and 3,4-dihydro- 2H-pyran and their derivatives. This types of cyclic vinyl ethers are in the present of academic interest only. 2,3-Dihydrofuran can be synthesized by different ways [35–38]. The first synthesis starts with 1,4-b utandiol and give the ring by the release of water and hydrogen [35]. ð9Þ The other possibility is to start from butadiene, to epoxidize one doublebond , using a new type of silver catalyst [36]. After heating of 1-epoxy-3-butene, 2,5-dihydrofuran is built by changing the ring size. The other possibility to get 2,5-dihydrofuran is, to treat 1,4-Dichloro-but-2-ene with strong bases at high temperatures [37], which yield 2,5-dihydrofuran which can easily be converted into 2,3-dihydrofuran in the presence of isomerization catalysts, such as Fe(CO) 5 , KOC(CH 3 ) 3 or Ru(PPh 3 ) 2 Cl 2 [38]. ∆ ∆ ð10Þ Copyright 2005 by Marcel Dekker. All Rights Reserved. 3. Polymer Synthetic Methods The methods used for the synthesis of poly(vinyl ethers) fall into three major classi- fications; cationic, coordination-cationic, and free-radical polymerizations. Typical examples of cationic agents are Lewis and Bronsted acids and iodine. Ziegler-Natta catalysts comprise agents that initiate coordination-cationic polymerization, whi le azo compounds and peroxides are initiators for free-radical polymerization. In Table 1 are listed various examples of the above types of initiators, together with the conditions under which their polymerizations were carried out. Insofar as was obtainable from the references cited, the table also includes conversion, molecular weight, and tacticity data. Since the literature for the polymerization of vinyl ethers is particularly extensive, no attempt was made to cite every reference available for each initiator. Rather, typical and usually the best and most complete example in the authors’ judgment was selected for inclusion in this table. In the following sections the state of present knowledge about the mechanism and utility of the various methods and initiator types are summarized. For an in-depth discussion of the mechanisms of individual catalyst systems, the reader is referred to the publication of Lal [39] and the review by Gandini and Cheradame [40]. B. Cationic Methods The reactivity of vinyl ethers in cationic polymerization depends not only on the initiator used but also on the structure of the vinyl ether itself. To generalize, it may be said that vinyl ethers possessing highly branched alkyl groups are more reactive than those bearing straight-chain alkyl groups and have a greater tendency toward stereoregularity in the final polymer. Substitution by alkyl groups at either the a or b positions on the vinyl group increases the electron density of the vinyl group and hence, its tendency to polymerize. cis- Propenyl ethers are more reactive than trans-propenyl ethers in nonpolar solvents, whereas in polar solvents their react ivity is comparable [41]. Under cationic conditions, aryl vinyl ethers tend to undergo side reactions leading to rearrangements instead of polymerization [1]. Using simple cationic initiators at elevated temperatures there is, in most cases, no stereochemical control, and atactic polymers result. In contrast, using BF 3 etherate at low temperatures, Schildknecht and his co-workers [42,43] were able to prepare crystalline, isotactic poly(isobutyl vinyl ether) as the first recorded example of a stereoregular polymer. Later studies by Blake and Carlson [44] demonstrated that when these polymerizations are carried out in nonpolar solvents, they proceed from a homogeneous phase to a gel-like phase. Stereoregular polymers are produced from both phases by a mechanism of slow chain propagation. Since that time, ster eoregular polymers have been prepared using a wide variety of catalysts, including metal halides, organometallic halides, metal oxyhalides, metal oxides, metal sulfates, stable carbenium ion salts, and Ziegler– Natta coordination catalysts. Cationic polymerizations of vinyl ethers are subject to the usual chain transfer and termination processes in the presence of hydroxyl-, aldehyde-, and basic-containing impurities that inhibit polymerization and limit and stop chain growth. Due to the propensity for vinyl ethers to hydrolyze in aqueous acidic media, water is usually to be avoided as a solvent in these types of polymerizations [45,46]. 1. Bronsted and Lewis Acids Due to the highly electron-rich character of their double bonds, vinyl ethers are susceptible to cationic polymerization using a variety of Bronsted and Lewis acids as initiators. Bronsted acids as weak as H 2 SO 3 (SO 2 þ H 2 O) and H 3 PO 4 effect the cationic polymerization of Copyright 2005 by Marcel Dekker. All Rights Reserved. these monomers. Reppe and co-workers [47,48] and later Favorskii and Shostokovskii [49] were among the first to employ both protonic and Lewis acids as initiators for the cationic polymerization of vinyl ethers. In the case of protonic acids, direct protonation of vinyl ether may occur as shown in equation (11) to give a carbocation species stabilized by the neighboring ether oxygen. ð11Þ Much work has been done using boron trifluoride complexes as initiators for vinyl ether polymerization, due principally to the use of these catalysts in the industrial production of poly(vinyl ether)s. The nature of the complexing agent has been found to influence the rate of polymerization in the following order: anisole > diisopropyl ether > diethyl ether > n-butyl ether > tetrahydrofuran [39,50]. BF 3 requires a protogen (water, alcohol, etc.) as a coinitiator to initiate polymerization. Protogens may be deliberately added or may be present in the polymerization mixtures due to adventitious moisture or other hydroxylic impurities. Similarly, many other but not all Lewis acids require protogens to initiate polymerization efficiently, and their mechanisms are similar to that given above. Commercial catalysts typically consist of BF 3 complexed with water [51] or diethyl ether [52] and are especially active for the polymerization of lower alkyl vinyl ethers. Polymerizations conducted using these initiator systems have come to be known as flash polymerizations because they are typically carried out at À40 to À79  C in the presence of a low-boiling hydrocarbon. Solvent such as ethane or propane used to control the exotherm of the polymerization by evaporative cooling (flashing off). Conversions are commonly very high, approaching 100%, although the molecular weights tend to be rather low. Flash polymerization is the current method of choice for the preparation of poly(vinyl ethers) on an industrial scale. A variety of other Lewis acids, including AlCl 3 , SnCl 4 , FeCl 3 , MgCl 2 , TiF 4 , ZnCl 2 , EtAlC1 2 ,Et 2 AlCl, and aluminum and titanium alkoxides have also been used to initiate the cationic polymerization of alkyl vinyl ethers. Like polymerizations using BF 3 , these polymerizations are highly exothermic, requiring low temperatures and dilution with solvents to avoid violent runaway polymerizations. Among the most active Lewis acid catalysts, as well as those givin g the best stereochemical control, are EtAlCl 2 and Et 2 AlCl [53–59]. Copyright 2005 by Marcel Dekker. All Rights Reserved. Table 1 Initiator Monomer(s) RO–CH¼CH 2 R¼ Solvent Temp. (  C) Mol. Weight (viscosity) Conversion (%) Physical state tacticity Ref. Protonic acids Al (OR) 3 -HF CH 3 CH 2 Cl 2 /n-heptane 0–25 Z red ¼ 7.2 dL/g 93 crystalline 173 various hydrocarbons 10–120 174 Al 2 (SO 4 ) 3 -3H 2 SO 4 i-C 4 H 9 CS 2 5 Z inh ¼ 1.9 dL/g 14–100 isotactic 175 CH 3 , i-C 3 H 7, C 4 H 9 isotactic 102, 176 i-C 4 H 9 Cr 2 (SO 4 ) 3 -H 2 SO 4 i-C 4 H 9, C 4 H 9 ,CH 3 n-hexane 40 [Z] ¼ 0.7–1.4 dL/g 80–93 crystalline 177 NH 4 ClO 4 various DMF oligomers 178 SO 2 C 4 H 9 , vinyl thioethers bulk À10 31, 179 Lewis acids BF 3 Et 2 O i-C 4 H 9 bulk À78 isotactic 180 i-C 4 H 9 CH 2 Cl 2 /n-haxane À78 [Z] ¼ 0.4–0.8 dL/g isotactic 181 C 4 H 9 propane À45–80 atactic 182 C 4 H 9 propane À50 low atactic 183 i-C 4 H 9 propane À78 high atactic 184 various propane/butane À25 variable 15–100 atactic 185 t-C 4 H 9 CH 2 Cl 2 /H 3 CNO 2 À78 syndiotactic 186 BF 3 2H 2 O various bulk 3–5 9.2–93 atactic 51 SnCl 2 i-C 4 H 9 , i-C 5 H 11 benzene 12 atactic 187 SnCl 4 i-C 4 H 9 CH 2 Cl 2 0 /n-hexane À78 [Z] ¼ 0.9–1.29 dL/g 88 isotactic 181 Et 2 AlCl i-C 3 H 7 , i-C 4 H 9 toluene/propylene À78 isotactic 56 neo-C 5 H 11 C 4 H 9 [Z] ¼ 2.9 dL/g 98 isotactic 55 EtAlCl 2 i-C 4 H 9 toluene/heptane À80 [Z] ¼ 2.2 dL/g 75–85 crystalline 53 i-C 4 H 9 toluene À80 [Z] ¼ 2.2 dL/g TiF 3 i-C 4 H 9 CH 2 Cl 2 /heptane 60 [Z] ¼ 0.2 dL/g 79 crystalline 188 SbCl 5 Allyl toluene À10 22–60000 g/mol 100 isotactic 189 MgCl 2 i-C 4 H 9 bulk 25 Zsp/c ¼ 0.55 dL/g 97 atactic 100 Iodine Copyright 2005 by Marcel Dekker. All Rights Reserved. I 2 C 4 H 9 , c-C 6 H 11 , dietyl ether 25 low atactic 79 i-C 4 H 9 , i-C 4 H 9 , 2-Cl-C 2 H 4 ethylene chloride 30 atactic 80 1,2-Divinyloxyethane CH 2 Cl 2 À5 139 1,2-Divinyloxyethane CHCl 3 0 190 Carbonium salts and cation radicals [Tropylium] þ SbCl À 6 i-C 4 H 9 CH 2 Cl 2 0[Z] ¼ 0.7–0.8 dL/g 100 87,91,186 [Trityl] þ SbCl À 6 i-C 4 H 9 CH 2 Cl 2 0[Z] ¼ 0.8 dL/g 100 87 CH 3 ,C 2 H 5 , i-C 4 H 9 CH 2 Cl 2 À40–0 191 [Trityl] þ X À t-C 4 H 9 CH 2 Cl 2 /toluene À76 M n ¼ 24,500 g/mol 64–90 isotactic 92 [9,10-Diphenyl anthracene] þ ClO À 4 n-C 4 H 9 , i-C 4 H 9 CH 3 CN, C 6 H 5 NO 2 À20–10 93–95 [Pyrene] þ ClO À 4 i-C 4 H 9 CH 3 NO 2 5 oligomers 96 [Rubene] þ ClO À 4 i-C 4 H 9 10–20 100 94,95 [Triphenylene] þ ClO À 4 i-C 4 H 9 CH 2 Cl 2 10–20 94 Grignard reagents C 4 H 9 MgBr C 4 H 9 , i-C 4 H 9 , i-C 3 H 7 bulk 25 high 74–90 crystalline 192 i-C 4 H 9 n-hexane 60–70 M w ¼ 280.000–900000 g/mol 43–49 crystalline 99 CH 3 ,C 2 H 5 ,C 4 H 9 , cyclohexane 80 [Z] ¼ 3.9 dL/g 47 crystalline 98 i-C 4 H 9 Metal oxyhalides AlOCl, AlOBr, AlOI i-C 4 H 9 CH 2 Cl 2 À78 Z red ¼ 0.14–0.31 dL/g 79–100 isotactic 193 CrO 2 Cl 2 i-C 4 H 9 pet. ether 0–20 Z red ¼ 2.62 dL/g 99 isotactic 100 VOCl 2 i-C 4 H 9 pet. ether 0–20 Z red ¼ 1.26 dL/g 30 atactic 193 WO 2 Cl 2 i-C 4 H 9 pet. ether 0–20 Z red ¼ 0.54 dL/g 25 atactic 193 Metal sulfates Fe 2 (SO 4 ) 3 H 2 SO 4 3-4 H 2 O C 2 H 5 , i-C 3 H 7 pentane À20 Z inh ¼ 1.7 –3.5 dL/g 14–95 crystalline 102 Fe 2 (SO 4 ) 3 , VOSO 4 , V(SO 4 ) 2 i-C 4 H 9 bulk 25–30 crystalline 194 Al(O-I-Pr) 3 þ H 2 SO 4 i-C 3 H 7 CH 2 Cl 2 25 Z sp ¼ 4.1 dL/g 70 195 TiO(SO 4 ), VO(SO 4 ), Cr(SO 4 ) 2 CH 3 , I-C 3 H 7 C 4 H 9 t-C 4 H 9 CH 2 Cl 2 25 crystalline 196 (continued ) Copyright 2005 by Marcel Dekker. All Rights Reserved. Table 1 Continued Initiator Monomer(s) RO–CH¼CH 2 R¼ solvent Temp. (  C) Mol. Weight (viscosity) Conversion (%) Physical state tacticity Ref. Fe 2 (SO 4 ) 3 , NiSO 4 , Al(O-i-Pr) 3 , Al 2 (SO 4 ) 3 H 2 SO 4 , MgSO 4 H 2 SO 4 , Cr 2 (SO 4 ) 3 H 2 SO 4 i-C 4 H 9 hexane 25 [Z] ¼ 1–2 dL/g 60–80 isotactic 197 Metal oxides Fe 2 O 3 i-C 4 H 9 toluene 25 Z sp ¼ 0.21–0.41 dL/g 43 isotactic 104 Cr 2 O 3 i-C 4 H 9 toluene 80 Z sp ¼ 2.14 dL/g 32 isotactic 103 MoO 2 i-C 4 H 9 bulk 25 Z sp ¼ 0.56 dL/g 62 atactic 100 V 2 O 3 i-C 4 H 9 bulk 25 Z sp ¼ 0.22 dL/g 22 atactic 100 NiO 2 i-C 4 H 9 bulk 25 Z sp ¼ 0.14 dL/g 36 atactic 100 SiO 2 i-C 4 H 9 bulk 25 Z sp ¼ 0.26 dL/g 71 atactic 100 Ziegler–Natta (coordination catalysts) VCl 3 AlCl 3 þ Al(i-C 4 H 9 ) 3 þ THF CH 3 ether 30 Z red ¼ 2.5 dL/ 79 crystalline 130 TiCl 3 þ Al(i-C 4 H 9 ) 3 CH 3 ether/n-heptene 30 10 amorphous 130 TiCl 4 þ Al(i-C 4 H 9 ) 3 i-C 4 H 9 bulk À78 [Z] ¼ 2–7 dL/g cristalline 198 allyl bulk À78 low 198 TiCl 4 þ Al(C 2 H 5 ) 3 C 2 H 5 benzene À40–100 low amorphous 199 (C 6 H 5 ) 2 Cr þ TiCl 4 i-C 4 H 9 toluene 25 10 crystalline 200 Photochemical (UV) Initiators (C 6 H 5 ) 2 I þ BF À 4 (C 6 H 5 ) 2 I þ PF À 4 (C 6 H 5 ) 2 I þ AsF À 6 (C 6 H 5 ) 2 I þ SbF À 6 2-Cl-C 2 H 4 CH 2 Cl 2 25 (hv 5 s) [Z] ¼ 0.15 dL/g 74 atactic 201 Copyright 2005 by Marcel Dekker. All Rights Reserved. (4-t-C 4 H 9 - C 6 H 4 )(C 6 H 5 ) 2 S þ AsPF À 6 2-Cl-C 2 H 4 CH 2 Cl 2 25 92 atactic 202 Electrochemical Initiation i-C 4 H 9 CH 2 Cl 2 /(Bu) 4 N þ BF À 4 25 80–90 203 C 4 H 9 CH 3 CN/NaClO 4 0 low 45–72 93 CH 3 CN/(Bu) 4 N þ ClO 4 À 0 3500–7000 g/mol 70–80 93 i-C 4 H 9 1,2-dichloroethane/ (Bu) 4 N þ I À 3 25 40–50 128 i-C 4 H 9 CH 3 CN/di-isopropyl ether/(Bu) 4 N þ ClO À 4 25 6400 g/mol 129 Free-radical initiators Di-t-butyl peroxide Cumene hydroperoxide t-Butyl hydroperoxide C 2 H 5 , i-C 4 H 9 cyclohexane 159 low 78 131 2,2 0 -Azobisisobutyronitrile aryl vinyl ethers bulk 75 530–743 g/mol 22 134, 204 Azo compounds various bulk, DMF 75 low 94 205 NaHSO 3 /(NH 4 ) 2 S 2 O 8 2-Cl-C 2 H 4 bulk 50 133 Miscellaneous initiators Sulfur various bulk 20–80 high 206 Molecular sieves i-C 4 H 9 benzene 30 [Z] ¼ 0.02–0.07 dL/g 90 207 ZnCl 2 þ t-BuCl CH 3 bulk À20–30 [Z] ¼ 0.2–1.3 dL/g 208 Al(Et) 3 þ POCl 3 þ SOCl 2 þ V 2 O 5 þ t-BuCl i-C 4 H 9 bulk 30 10–91 101 Carbon (channel back) i-C 4 H 9 CCl 4 20 84 180 a Coupled means that both processes occur in the same space; decoupled means that both processes occur in separate spaces. Copyright 2005 by Marcel Dekker. All Rights Reserved. 2. Hydrogen Iodide-Iodine (Living/Controlled Cationic Polymerization) The synthesis of polymers with controlled end groups, molecular weight distribution, and the preparation of well-characterized block polymers requires polymerization methods in which the growing chain end is well defined and undergoes chain growth in the absence of termination and chain transfer. Until recently, these conditions have been observed only in certain anionic polymerizations and were unknown although highly sought after in cationic polymerizations. In 1984, workers at Kyoto University [60] described the first example of a living cationic polymerization consisting of vinyl ethers employing the initiator system HI/I 2 . Since that time, a number of additional papers have appeared by this same group of researchers which describe in some details the characteristics of this particular initiator system [61]. Various well-characterized functional polymers and block polymers were prepared using this new initiator [62]. The absence of termination and transfer using the HI/I 2 initiator system was attributed to a tight association of the stabilization of the growing carbocationic end group by the counterion. ð12Þ In the first step, HI adds to the vinyl ether monomer to give a 1:1 adduct. Next, the carbon-iodide bond of the adduct is activated by iodine, allowing insertion of the incoming monomer at the end of the chain. In this mechani sm, I 2 behaves as a weak electrophile that activates the C–I bond of the vinyl ether-HI adduct by association. Accordingly, the Highashimura group has termed HI the initiator and I 2 the activator. Another mechanism that perhaps better explains the living character of the HI/I 2 – vinyl ether system has been put forth by Matyjaszewski [63] and involves the polymerization occurring through a six-membered transition state involving the C–I chain end, I 2 , and the incoming vinyl ether monomer. ð13Þ In addition to the HI/I 2 initiator system described above, the Kyoto group [64–66] have described several new initiators that also display living character in the pol ymerization of vinyl ether monomers. They report that isobutyl vinyl ether may be polymerized in the Copyright 2005 by Marcel Dekker. All Rights Reserved. [...]... 80–100 80–100 [34 2 34 4] [34 2] [34 2] [34 2] [34 2 ,34 3] [34 2 ,34 3] [34 2 34 4] [34 2] [34 2 ,34 3] [34 2] [34 3] [34 2] [34 3 ,34 4] [34 2] [34 3 ,34 4] [34 2 34 4] [34 4] [34 4] [34 3 ,34 4] [34 2 34 4] [34 4] [34 2] [34 2] [34 2] [34 2 34 4] [34 2 ,34 3] [31 1] [34 2 ,34 3] Many authors [30 7 ,30 9 ,34 0 ,35 3 35 5] have investigated the dependence of the molecular weight of polymers produced in bulk on the initiator concentration, type of initiator,... only for the polymerization of small masses of monomer Because of the rapidity of vinyl acetate polymerizations, its high heat of polymerization, and the poor heat-transfer characteristics of the polymer, bulk polymerization of large masses of monomer can result in runaway conditions leading to partial decomposition of the polymer that is formed For these reasons, bulk polymerizations of vinyl acetate... the polymers obtained from polymerization of ethylene glycol divinyl ether using AIBN and iodine ð29Þ Copyright 2005 by Marcel Dekker All Rights Reserved The related monomers divinyl formal (30 a), acetal (30 b), and dimethylketal (30 c) also undergo facile free-radical polymerization to give mainly soluble polymers [140–145] 30 Þ Detailed NMR analysis of the polymers produced by the polymerization of. .. preparation of poly(vinyl acetate) [265] D Controlled Radical Polymerization Methods Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization using xanthanes and dithiocarbamates is described [266] Narrow polydispersities and good control of molecular weight for polymers of Mn < 30 000 are achieved for these polymers The living nature of RAFT polymerization allows the synthesis of block copolymers,... stereospecifity, and crystallinity is the polymerization temperature C Radical Polymerization: Procedures 1 Polymerization in Bulk The bulk polymerization of VC is the third important manufacturing process for PVC [291 ,33 4 33 6] The advantage of bulk polymerization is, in contrast to the more common suspension or emulsion polymerization, that products are free of protective colloids, suspending agents,... pyrolysis of ethylidine diacetate obtained from acetaldehyde (38 ) [219,220] CH3 CHO þ ðCH3 COÞ2 O À CH3 CHðOOCCH3 Þ2 ! 37 Þ ! CH3 CHOðOOCCH3 Þ2 À CH3 COOHþH2 C ¼ CHÀOOCCH3 38 Þ Vinyl esters of carboxylic acids, which are not amenable to preparation by other synthetic techniques, are readily prepared by transvinylation As depicted in equation (39 ), Copyright 2005 by Marcel Dekker All Rights Reserved a... polymerization of divinyl ether proceeds to give a polymer that incorporates tetrahydrofuran, vinyloxy, and dioxabicyclo [3. 3.0]octane units [ 137 , 138 ]: ð28Þ Work by Nishikubo et al [ 139 ] showed that the polymerization of divinyl ethers derived from aliphatic diols gave polymers with different structures, depending on whether cationic or free-radical initiators were used Shown in equation (29) are the structures of. .. a short overview of the polymerization of VC The most common method is polymerization by free radicals [30 5] According to the ease of homolytic splitting of the p bond in the monomer, radical polymerization takes place in the presence of suitable initiation systems In general, there are three methods for producing radicals available for the polymerization of VC: (A) thermal cleavage of azo or peroxo... free polymerization of VC in a precipitating medium exhibits an accelerating rate from the beginning of reaction up to high conversion [30 7] This behavior is called autoacceleration and is typical for heterogeneous polymerization of halogenated vinyls and acrylonitrile [30 8] Detailed studies of polymerization mechanism and analysis of microstructure have been carried out [291 ,30 9] Primary structure of. .. co-workers [165,166] observed that divinyl ether itself forms a soluble, high-molecular weight 1:2 copolymer The structure of the copolymer has been elucidated by a number of authors [167–170] and appears to consist of the combination of (32 a) and (32 b), due to cyclopolymerization 32 Þ This copolymers have a variety of biological and physiological properties, ranging from antifungal, bacteriostatic, and most . temperatures [37 ], which yield 2,5-dihydrofuran which can easily be converted into 2 ,3- dihydrofuran in the presence of isomerization catalysts, such as Fe(CO) 5 , KOC(CH 3 ) 3 or Ru(PPh 3 ) 2 Cl 2 [38 ]. ∆ ∆ ð10Þ Copyright. tetrahydrofuran, vinyloxy, and dioxabicyclo [3. 3.0]octane units [ 137 , 138 ]: ð28Þ Work by Nishikubo et al. [ 139 ] showed that the polymerization of divinyl ethers derived from aliphatic diols gave polymers. 202 Electrochemical Initiation i-C 4 H 9 CH 2 Cl 2 /(Bu) 4 N þ BF À 4 25 80–90 2 03 C 4 H 9 CH 3 CN/NaClO 4 0 low 45–72 93 CH 3 CN/(Bu) 4 N þ ClO 4 À 0 35 00–7000 g/mol 70–80 93 i-C 4 H 9 1,2-dichloroethane/ (Bu) 4 N þ I À 3 25 40–50 128 i-C 4 H 9 CH 3 CN/di-isopropyl ether/(Bu) 4 N þ ClO À 4 25