Living cationic polymerization of dihydrofuran and its derivatives

Cationic polymerization of 2,3‐dihydrofuran (DHF) and its derivatives was examined using base‐stabilized initiating systems with various Lewis acids. Living cationic polymerization of DHF was achieved using Et_1.5AlCl_1.5 in toluene in the presence of THF at 0 °C, whereas it has been reported that only less controlled reactions occurred at 0 °C. Monomer‐addition experiments of DHF and the block copolymerization with isobutyl vinyl ether demonstrated the livingness of the DHF polymerization: the number–average molecular weight of the polymers shifted higher with low polydispersity as the polymerization proceeded after the monomer addition. Furthermore, this base‐stabilized cationic polymerization system allowed living polymerization of ethyl 1‐propenyl ether and 4,5‐dihydro‐2‐methylfuran at ?30 and ?78 °C, respectively. In the polymerization of 2,3‐benzofuran, the long‐lived growing species were produced at ?78 °C. The obtained polymers have higher glass transition temperatures compared to poly(acyclic alkyl vinyl ether)s. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4495–4504, 2008     

Star‐shaped cyclopolymers: A new category of star polymer with rigid cyclized arms prepared by controlled cationic cyclopolymerization and subsequent microgel formation of divinyl ethers

The combination of living/controlled cationic cyclopolymerization and crosslinking polymerization of bifunctional vinyl ethers (divinyl ethers) was applied to the synthesis of core‐crosslinked star‐shaped polymers with rigid cyclized arms. Cyclopolymerization of 4,4‐bis(vinyloxymethyl)cyclohexene ( 1 ), a divinyl ether with a cyclohexene group, was investigated with the hydrogen chloride/zinc chloride (HCl/ZnCl₂) initiating system in toluene at 0 °C. The reaction proceeded quantitatively to give soluble poly( 1 )s in organic solvents. The content of the unreacted vinyl groups in the produced polymers was less than ～3 mol%, and therefore, the degree of cyclization of the polymers was determined to be ～97%. The number‐average molecular weight (M_n) of the polymers increased in direct proportion to monomer conversion and further increased on addition of a fresh monomer feed to the almost completely polymerized reaction mixture, indicating that living cyclopolymerization of 1 occurred. The chain linking reactions among the formed living cyclopolymers with 1,4‐bis(vinyloxy)cyclohexane ( 3 ) as a crosslinker in toluene at 0 °C produced core‐crosslinked star‐shaped cyclopoly( 1 )s [star‐poly( 1 )s] in high yield (100%). Dihydroxylation of the cyclohexene double bonds of star‐poly( 1 ) gave hydrophilic water‐soluble star‐shaped polymers with rigid arm structure [star‐poly( 1 )‐OH] with thermo‐responsive function in water. T_gs of star‐poly( 1 ) and star‐poly( 1 )‐OH were 135 °C and 216 °C, respectively; these values are very high as vinyl ether‐based star‐shaped polymers. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1094–1102     

Synthesis of biocompatible and biodegradable block copolymers of polyvinyl alcohol‐block‐poly(ε‐caprolactone) using metal‐free living cationic polymerization

Applications of metal‐free living cationic polymerization of vinyl ethers using HCl · Et₂O are reported. Product of poly(vinyl ether)s possessing functional end groups such as hydroxyethyl groups with predicted molecular weights was used as a macroinitiator in activated monomer cationic polymerization of ε‐caprolactone (CL) with HCl · Et₂O as a ring‐opening polymerization. This combination method is a metal‐free polymerization using HCl · Et₂O. The formation of poly(isobutyl vinyl ether)‐b‐poly(ε‐caprolactone) (PIBVE‐b‐PCL) and poly(tert‐butyl vinyl ether)‐b‐poly(ε‐caprolactone) (PTBVE‐b‐PCL) from two vinyl ethers and CL was successful. Therefore, we synthesized novel amphiphilic, biocompatible, and biodegradable block copolymers comprised polyvinyl alcohol and PCL, namely PVA‐b‐PCL by transformation of acid hydrolysis of tert‐butoxy moiety of PTBVE in PTBVE‐b‐PCL. The synthesized copolymers showed well‐defined structure and narrow molecular weight distribution. The structure of resulting block copolymers was confirmed by ¹H NMR, size exclusion chromatography, and differential scanning calorimetry. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5169–5179, 2009     

Living cationic polymerization of vinyl ethers in the presence of a strong base: Poisonous or helpful?

A quite small dose of a poisonous species was found to induce living cationic polymerization of isobutyl vinyl ether (IBVE) in toluene at 0 °C. In the presence of a small amount of N,N‐dimethylacetamide, living cationic polymerization of IBVE was achieved using SnCl₄, producing a low polydispersity polymer (weight–average molecular weight/number–average molecular weight (M_w/M_n) ≤ 1.1), whereas the polymerization was terminated at its higher concentration. In addition, amine derivatives (common terminators) as stronger bases allow living polymerization when a catalytic quantity was used. On the other hand, EtAlCl₂ produced polymers with comparatively broad MWDs (M_w/M_n ～ 2), although the polymerization was slightly retarded. The systems with a strong base required much less quantity of bases than weak base systems such as ethers or esters for living polymerization. The strong base system exhibited Lewis acid preference: living polymerization proceeded only with SnCl₄, TiCl₄, or ZnCl₂, whereas a range of Lewis acids are effective for achieving living polymerization in the conventional weak base system such as an ester and an ether. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6746–6753, 2008     

Cationic addition polymerization of 1,4‐dioxene using gacl3 as lewis acid catalyst: Long‐lived species‐mediated polymerization

Effective cationic addition polymerization of 1,4‐dioxene, a six‐membered cyclic olefin with two oxygen atoms adjacent to the double bond, was performed using a simple metal halide catalyst system in dichloromethane. The polymerization was controlled when the reaction was conducted using GaCl₃ in conjunction with an isobutyl vinyl ether–HCl adduct as a cationogen at –78°C to give polymers with predetermined molecular weights and relatively narrow molecular weight distributions. The long‐lived properties of the propagating species were further confirmed by a monomer addition experiment and the analyses of the product polymers by ¹H NMR and MALDI–TOF–MS. Although highly clean propagation proceeded, the apparent rate constant changed during the controlled cationic polymerization of 1,4‐dioxene. The reason for the change was discussed based on polymerization results under various conditions. The obtained poly(1,4‐dioxene) exhibited a very high glass transition temperature (T_g) of 217°C and unique solubility. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Living cationic polymerization of vinyl ethers with a urethane group

To study the possibility of living cationic polymerization of vinyl ethers with a urethane group, 4‐vinyloxybutyl n‐butylcarbamate ( 1 ) and 4‐vinyloxybutyl phenylcarbamate ( 2 ) were polymerized with the hydrogen chloride/zinc chloride initiating system in methylene chloride solvent at ?30 °C ([monomer]₀ = 0.30 M, [HCl]₀/[ZnCl₂]₀ = 5.0/2.0 mM). The polymerization of 1 was very slow and gave only low‐molecular‐weight polymers with a number‐average molecular weight (M_n) of about 2000 even at 100% monomer conversion. The structural analysis of the products showed occurrence of chain‐transfer reactions because of the urethane group of monomer 1 . In contrast, the polymerization of vinyl ether 2 proceeded much faster than 1 and led to high‐molecular‐weight polymers with narrow molecular weight distributions (MWDs ≤ ～1.2) in quantitative yield. The M_n's of the product polymers increased in direct proportion to monomer conversion and continued to increase linearly after sequential addition of a fresh monomer feed to the almost completely polymerized reaction mixture, whereas the MWDs of the polymers remained narrow. These results indicated the formation of living polymer from vinyl ether 2 . The difference of living nature between monomers 1 and 2 was attributable to the difference of the electron‐withdrawing power of the carbamate substituents, namely, n‐butyl for 1 versus phenyl for 2 , of the monomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2960–2972, 2004     

Living cationic polymerization of n‐butyl propenyl ether

Cationic polymerization of n‐butyl propenyl ether (BuPE; CH₃CH CHOBu, cis/trans = 64/36) was examined with the HCl–IBVE (isobutyl vinyl ether) adduct/ZnCl₂ initiating system at −15 ∼ −78 °C in nonpolar (hexane, toluene) and polar (dichloromethane) solvents, specifically focusing on the feasibility of its living polymerization. In contrast to alkyl vinyl ethers, the living nature of the growing species in the BuPE polymerization was sensitive to polymerization temperature and solvent. For example, living cationic polymerization of IBVE can be achieved even at 0 °C with HCl–IBVE/ZnCl₂, whereas for BuPE whose β‐methyl group may cause steric hindrance ideal living polymerization occurred only at −78 °C. Another interesting feature of this polymerization is that the polymerization rate in hexane is as large as in dichloromethane, much larger than in toluene. A new method in determining the ratio of the living growing ends to the deactivated ones was developed with a devised monomer‐addition experiments, in which IBVE that can be polymerized in a living fashion below 0 °C was added to the almost completely polymerized solution of BuPE. The amount of the deactivated chain ends became small in hexane even at −40 °C in contrast to other solvents. Thus hexane turned out an excellent solvent for living cationic polymerization of BuPE. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 229–236, 2000     

Aldol‐type group‐transfer polymerization of silyl vinyl ethers using silyl perfluoroalkaneimides as nonmetal catalysts

We investigated the catalytic activity of bis(nonafluorobutanesulfonyl)imide (Nf₂NH), acting as a Brønsted acid, and its silylated imide, t‐butyldimethylsilyl nonafluorobutanesulfonylimide (Nf₂NTBDMS), acting as a Lewis acid, for aldol‐type of group‐transfer polymerization (Aldol‐GTP) of silyl vinyl ethers. Aldol‐GTPs of t‐butyldimethylsilyl vinyl ether (VOTBDMS) and triethylsilyl vinyl ether (VOTES) proceeded in dichloromethane at 0 °C with benzaldehyde as the initiator. Nf₂NH catalyzed the polymerization of VOTBDMS although the product poly(VOTBDMS) had a molecular weight of 2510, which was considerably smaller than that predicted by the ratio of the initial monomer to initiator concentrations, and the smaller molecular weight was a consequence of desilylation of VOTBDMS before the polymerization step. Conversely, when Nf₂NTBDMS was used as the catalyst, poly(VOTBDMS) with molecular weight >16,000 was obtained. The Nf₂NTBDMS‐catalyzed polymerization was more rapid than polymerizations that used t‐butyldimethylsilyl trifluoromethanesulfonylimide, t‐butyldimethylsilyl hexafluorocycropropanesulfonylimide, or zinc bromide as the catalyst, even though the ratio of Nf₂NTBDMS to the monomer was the smallest used. With VOTES as the monomer, and Tf₂NTBDMS as the catalyst, a poly(VOTES) with a syndiotactic tendency (mm:mr:rr = 9:44:47) was produced. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3516–3522     

Living/controlled cationic cyclopolymerization of divinyl ether with a cyclic acetal moiety: Synthesis of poly(vinyl ether)s with high glass transition temperature based on incorporation of cyclized main chain and cyclic side chains

Cationic cyclopolymerization of 2‐methyl‐5,5‐bis(vinyloxymethyl)‐1,3‐dioxane ( 1 ), a divinyl ether with a cyclic acetal group, was investigated with the HCl/ZnCl₂ initiating system in toluene and methylene chloride at ?30 °C. The reaction proceeded quantitatively to give gel‐free, soluble polymers in organic solvents. The number‐average molecular weight (M_n) of the polymers increased in direct proportion to monomer conversion, and further increased on addition of a fresh monomer feed to the almost completely polymerized reaction mixture, indicating that the polymerization proceeded in living/controlled manner. The contents of the unreacted vinyl groups in the produced soluble polymers were less than ～3 mol %, and therefore, the degree of cyclization was determined to be ～97%. In contrast, the pendant cyclic acetal groups remained intact in the polymers under the present cationic polymerization conditions. These facts show that cyclopolymerization of 1 almost exclusively occurred and the poly(vinyl ether)s with the cyclized repeating units and cyclic pendant acetal rings were obtained. Glass transition temperature (T_g) and thermal decomposition temperature (T_d) of poly( 1 ) (M_n = 7870, M_w/M_n = 1.57) were found to be 166 and 338 °C, respectively, indicating that poly( 1 ) had high T_g and high thermal stability. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 952–958, 2010     

Rapid living cationic polymerization of vinyl ethers by a single‐molecular initiating system

Initiated by an organic molecule trifluoromethanesulfonimide (HNTf₂) without any Lewis acid or Lewis base stabilizer, cationic polymerization of isobutyl vinyl ether (IBVE) takes place rapidly and the polymerization is proved to be in a controlled/living manner. The conversion of IBVE could easily achieve 99% in seconds. The product poly(isobutyl vinyl ether) is narrowly distributed and its molecular weight increases linearly with time and fits well with the corresponding theoretical value. This single‐molecular initiating system also works well in the living cationic polymerization of ethyl vinyl ether. HNTf₂ is considered playing multiple roles which include initiator, activator, and stabilizer in the polymerization. It is quite different from the hydrogen halide‐catalyzed polymerizations of vinyl ethers. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1373‐1377     

Cationic cyclopolymerization of new divinyl ethers: The effect of ether and ester neighboring functional groups on their cyclopolymerization tendency

The cationic polymerization of two new divinyl ethers, 1‐(2‐vinyloxyethoxy)‐2‐[(2‐vinyloxyethoxy)carbonyl]benzene ( 2 ) and 1,2‐bis[(2‐vinyloxyethoxy)carbonyl]benzene ( 3 ), as well as 1,2‐bis(2‐vinyloxyethoxy)benzene ( 1 ), with BF₃OEt₂ in CH₂Cl₂ at 0 °C at low initial monomer concentrations ([M]₀ = 0.15 and 0.075 M) gave soluble polymers with relatively high molecular weights and broad molecular weight distributions (MWDs), whereas reactions with the HCl/ZnCl₂ initiating system yielded soluble polymers with relatively narrow MWDs (weight‐average molecular weight/number‐average molecular weight ? 1.6) under similar reaction conditions. An NMR structural analysis of the HCl/ZnCl₂‐mediated polymers from the divinyl ethers showed that poly( 1 ) had virtually no unreacted vinyl ether groups throughout the polymerization (monomer conversion = 28–98%), whereas poly( 2 ) and poly( 3 ) possessed some amount of unreacted vinyl ether groups in the initial stage of the polymerization; the content of the vinyl groups of poly( 2 ) was 18 mol % at a 15% monomer conversion, and the content of the vinyl groups of poly( 3 ) was 31 mol % at an 18% monomer conversion. Therefore, divinyl ether 1 underwent cyclopolymerization exclusively to give almost completely cyclized polymers [degree of cyclization (DC) ～ 100%], whereas divinyl ethers 2 and 3 exhibited a lower cyclopolymerization tendency [DC for poly( 2 ) = 82%; DC for poly( 3 ) = 69%]. The differences in the cyclopolymerization tendencies among the divinyl ethers can be explained by the differences in the solvation powers of the neighboring functional groups adjacent to the vinyl ether moiety with the active center: the ether oxygen of the ether neighboring group solvates intramolecularly with the active center to accelerate the intramolecular propagation, but such an interaction is less effective with the more electron‐deficient oxygen attached to the carbonyl group of the ester neighboring group. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 281–292, 2003     

Cationic cyclopolymerization of divinyl ethers with norbornane‐, norbornene‐, or adamantane‐containing substituents: Synthesis of cyclopoly(divinyl ether)s with bulky rigid side chains leading to high glass transition temperature

Cationic cyclopolymerizations of 2,2‐bis(vinyloxymethyl)bicyclo[2.2.1]heptane ( 1 ), 5,5‐bis(vinyloxymethyl)‐2‐bicyclo[2.2.1]heptene ( 2 ), and 2,2‐bis(vinyloxymethyl)tricyclo[3.3.1.1]^{3, 7}decane ( 3 ), divinyl ethers with a norbornane, norbornene, or adamantane unit, respectively, were investigated with the HCl/ZnCl₂ initiating system in toluene and methylene chloride at ?30 °C. All the reactions proceeded quantitatively to give gel‐free, soluble polymers in organic solvents. The number‐average molecular weight (M_n) of the polymers increased in direct proportion to monomer conversion and further increased on addition of a fresh monomer feed to the almost completely polymerized reaction mixture. The contents of the unreacted vinyl groups in the produced soluble polymers were less than ～10 mol %, and therefore, the degree of cyclization of the polymers was determined to be over ～90%. These facts show that cyclopolymerization of 1 , 2 , and 3 exclusively occurred and the poly(vinyl ether)s with the cyclized repeating units and polycyclic pendants were obtained with their molecular weights being regulated. BF₃OEt₂ initiator also caused cyclopolymerization of 1 , 2 , and 3 to give the corresponding high‐molecular‐weight cyclopolymers quantitatively. Glass transition temperatures (T_g's) of poly( 1 ) and poly( 2 ) were 165–180 °C, and T_g's of poly( 3 ) were 211–231 °C; these values are very high as vinyl ether polymers. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2445–2454     

Living cationic polymerization of amide‐functional vinyl ethers: Specific properties of SnCl4‐based initiating system

Living cationic copolymerization of amide‐functional vinyl ethers with isobutyl vinyl ether (IBVE) was achieved using SnCl₄ in the presence of ethyl acetate at 0 °C: the number–average molecular weight of the obtained polymers increased in direct proportion to the monomer conversion with relatively low polydispersity, and the amide‐functional monomer units were introduced almost quantitatively. To optimize the reaction conditions, cationic polymerization of IBVE in the presence of amide compounds, as a model reaction, was also examined using various Lewis acids in dichloromethane. The combination of SnCl₄ and ethyl acetate induced living cationic polymerization of IBVE at 0 °C when an amide compound, whose nitrogen is adjacent to a phenyl group, was used. The versatile performance of SnCl₄ especially for achieving living cationic polymerization of various polar functional monomers was demonstrated in this study as well as in our previous studies. Thus, the specific properties of the SnCl₄ initiating system are discussed by comparing with the Et_xAlCl_3?x systems from viewpoints of hard and soft acids and bases principle and computational chemistry. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6129–6141, 2008     

Synthesis of end‐functionalized polymers and copolymers of cyclopentadiene with vinyl ethers by cationic polymerization

A series of cyclopentadiene (CPD)‐based polymers and copolymers were synthesized by a controlled cationic polymerization of CPD. End‐functionalized poly(CPD) was synthesized with the HCl adducts [initiator = CH₃CH(OCH₂CH₂X)Cl; X = Cl ( 2a ), acetate ( 2b ), or methacrylate] of vinyl ethers carrying pendant functional substituents X in conjunction with SnCl₄ (Lewis acid as a catalyst) and n‐Bu₄NCl (as an additive) in dichloromethane at −78 °C. The system led to the controlled cationic polymerizations of CPD to give controlled α‐end‐functionalized poly(CPD)s with almost quantitative attachment of the functional groups (F_n ∼ 1). With the 2a or 2b /SnCl₄/n‐Bu₄NCl initiating systems, diblock copolymers of 2‐chloroethyl vinyl ether (CEVE) and 2‐acetoxyethyl vinyl ether with CPD were also synthesized by the sequential polymerization of CPD and these vinyl ethers. An ABA‐type triblock copolymer of CPD (A) and CEVE (B) was also prepared with a bifunctional initiator. The copolymerization of CPD and CEVE with 2a /SnCl₄/n‐Bu₄NCl afforded random copolymers with controlled molecular weights and narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight = 1.3–1.4). © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 398–407, 2001     

Synthesis of fluorine‐containing star‐shaped poly(vinyl ether)s via arm‐linking reactions in living cationic polymerization

Various types of fluorine‐containing star‐shaped poly(vinyl ether)s were successfully synthesized by crosslinking reactions of living polymers based on living cationic polymerization. Star polymers with fluorinated arm chains were prepared by the reaction between a divinyl ether and living poly(vinyl ether)s with fluorine groups (C₄F₉, C₆F₁₃, and C₈F₁₇) at the side chain using cationogen/Et_1.5AlCl_1.5 in a fluorinated solvent (dichloropentafluoropropanes), giving star‐shaped fluorinated polymers in high yields with a relatively narrow molecular weight distribution. The concentration of living polymers for the crosslinking reaction and the molar feed ratio of a bifunctional vinyl ether to living polymers affected the yield and molecular weight of the star polymers. Star polymers with block arms were prepared by a linking reaction of living block copolymers of a fluorinated segment and a nonfluorinated segment. Heteroarm star‐shaped polymers containing two‐ or three‐arm species were synthesized using a mixture of different living polymer species for the reaction with a bifunctional vinyl ether. The obtained polymers underwent temperature‐induced solubility transitions in various organic solvents, and their concentrated solutions underwent sol–gel transitions, based on the solubility transition of a thermoresponsive fluorinated segment. Furthermore, a slight amount of fluorine groups were shown to be effective for physical gelation when those were located at the arm ends of a star polymer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Thermosensitive polyalcohols: Synthesis via living cationic polymerization of vinyl ethers with a silyloxy group

Thermosensitive homopolymers and copolymers with hydroxy groups were synthesized via the living cationic polymerization of Si‐containing vinyl ethers. The cationic homopolymerization and copolymerization of five vinyl ethers with silyloxy groups, each with a different spacer length, were examined with a cationogen/Et_1.5AlCl_1.5 initiating system in the presence of an added base. When an appropriate base was added, the living cationic polymerization of Si‐containing monomers became feasible, giving polymers with narrow molecular weight distributions and various block copolymers. Subsequent desilylation gave well‐defined polyalcohols, in both water‐soluble and water‐insoluble forms. One of these polyalcohols, poly(4‐hydroxybutyl vinyl ether), underwent lower‐critical‐solution‐temperature‐type thermally induced phase separation in water at a critical temperature (T_PS) of 42 °C. This phase separation was quite sensitive and reversible on heating and cooling. The phase separation also occurred sensitively with random copolymers of thermosensitive and hydrophilic or hydrophobic units, the T_PS values of which in water could be controlled by the monomer feed ratio. The thermal responsiveness of this polyalcohol unit made it possible to prepare novel thermosensitive block and random copolymers consisting solely of alcohol units. One example prepared in this study was a 20 wt % aqueous solution of a diblock copolymer consisting of thermosensitive poly(4‐hydroxybutyl vinyl ether) and water‐soluble poly(2‐hydroxyethyl vinyl ether) segments, which transformed into a physical gel above 42 °C. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3300–3312, 2003     

Catalytic effect of dimethyl sulfoxide in the Cu(0)/tris(2‐dimethylaminoethyl)amine‐catalyzed living radical polymerization of methyl methacrylate at 0–90 °C initiated with CH3CHClI as a model compound for α,ω‐di(iodo)poly(vinyl chloride) chain ends

A variety of conditions, including catalysts [CuCl, CuI, Cu₂O, and Cu(0)], ligands [2,2′‐bipyridine (bpy), tris(2‐dimethylaminoethyl)amine (Me₆‐TREN), polyethyleneimine, and hexamethyl triethylenetetramine], initiators [CH₃CHClI, CH₂I₂, CHI₃, and F(CF₂)₈I], solvents [diphenyl ether, toluene, tetrahydrofuran, dimethyl sulfoxide (DMSO), dimethylformamide, ethylene carbonate, dimethylacetamide, and cyclohexanone], and temperatures [90, 25, and 0 °C] were studied to assess previous methods for poly(methyl methacrylate)‐b‐poly(vinyl chloride)‐b‐poly(methyl methacrylate) (PMMA‐b‐PVC‐b‐PMMA) synthesis by the living radical block copolymerization of methyl methacrylate (MMA) initiated with α,ω‐di(iodo)poly(vinyl chloride). CH₃CHClI was used as a model for α,ω‐di(iodo)poly(vinyl chloride) employed as a macroinitiator in the living radical block copolymerization of MMA. Two groups of methods evolved. The first involved CuCl/bpy or Me₆‐TREN at 90 °C, whereas the second involved Cu(0)/Me₆‐TREN in DMSO at 25 or 0 °C. Related ligands were used in both methods. The highest initiator efficiency and rate of polymerization were obtained with Cu(0)/Me₆‐TREN in DMSO at 25 °C. This demonstrated that the ultrafast block copolymerization reported previously is the most efficient with respect to the rate of polymerization and precision of the PMMA‐b‐PVC‐b‐PMMA architecture. Moreover, Cu(0)/Me₆‐TREN‐catalyzed polymerization exhibits an external first order of reaction in DMSO, and so this solvent has a catalytic effect in this living radical polymerization (LRP). This polymerization can be performed between 90 and 0 °C and provides access to controlled poly(methyl methacrylate) tacticity by LRP and block copolymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1935–1947, 2005     

Cationic RAFT Polymerization Using ppm Concentrations of Organic Acid

A metal‐free, cationic, reversible addition–fragmentation chain‐transfer (RAFT) polymerization was proposed and realized. A series of thiocarbonylthio compounds were used in the presence of a small amount of triflic acid for isobutyl vinyl ether to give polymers with controlled molecular weight of up to 1×10⁵ and narrow molecular‐weight distributions (M_w/M_n<1.1). This “living” or controlled cationic polymerization is applicable to various electron‐rich monomers including vinyl ethers, p‐methoxystyrene, and even p‐hydroxystyrene that possesses an unprotected phenol group. A transformation from cationic to radical RAFT polymerization enables the synthesis of block copolymers between cationically and radically polymerizable monomers, such as vinyl ether and vinyl acetate or methyl acrylate.     

Stereochemistry in cationic polymerization of alkenyl ethers. II. Formation of poly(ß-substituted vinyl ether)s with erythro-meso structures

The formation of polymers with erythro-meso structures, which could not be obtained from propenyl ethers with BF₃O(C₂H₅)₂, was studied by ¹³C-NMR spectroscopy on poly(ß-substituted vinyl ether)s obtained under a variety of conditions of polymerization. It was established that poly(cis-ethyl propenyl ether) obtained with Al₂(SO₄)₃–H₂SO₄ complex in toluene at 0°C was a highly stereoregular polymer with an erythro-meso structure. Cis-2-chlorovinyl ethyl ether and cis-methyl and ethyl butenyl ethers also yielded polymers with erythro-meso structures under the same conditions. In addition, with BF₃O(C₂H₅)₂ at ?78°C these three cis isomers produced amorphous polymers with threo-meso, racemic, and, in a few cases, erythro-meso structures, whereas cis-ethyl propenyl ether produced polymers with only threo-meso and racemic structures by the same catalyst. On the other hand, all trans isomers produced stereoregular polymers with threo-meso structures with BF₃O(C₂H₅)₂ at ?78°C, regardless of their ß-substituents; no erythro-meso structures were found in the polymers obtained.     

Living cationic polymerization of vinyl ethers with a naphthyl group: Decisive effect of the substituted position on naphthalene ring

Living cationic polymerization of a vinyl ether with a naphthyl group [2‐(2‐naphthoxy)ethyl vinyl ether, βNpOVE] was achieved using base‐assisting initiating systems with a Lewis acid. The Et_1.5AlCl_1.5/1,4‐dioxane or ethyl acetate system induced the living cationic polymerization of βNpOVE in toluene at 0 °C. The living nature of this reaction was confirmed by a monomer addition experiment, followed by ¹H NMR and matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) analyses. In contrast, the polymerization of αNpOVE was not fully controlled; under similar conditions, it produced polymers with broad molecular weight distributions. The ¹H NMR and MALDI‐TOF‐MS spectra of the resultant poly(αNpOVE) revealed that the products had undesirable structures derived from Friedel–Crafts alkylation. The higher reactivity of αNpOVE in electrophilic substitution reactions, such as the Friedel–Crafts reaction, was attributable to the greater electron density of the naphthyl ring, which was calculated based on frontier orbital theory. The naphthyl groups significantly affected the properties of the resultant polymer. For example, the glass transition temperatures (T_g) of poly(NpOVE)s are higher by approximately 40 °C than that of poly(2‐phenoxyethyl vinyl ether). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012