Effect of central spacer chain structure on cationic cyclopolymerization tendency of divinyl ethers

To clarify the effects of the central spacer chain structure of divinyl ethers on their cationic cyclopolymerization tendencies, 1,4‐bis[(2‐vinyloxy)ethoxy]benzene ( 1 ), 1,4‐bis[(2‐vinyloxy)ethoxy]butane ( 2 ), 1,6‐bis[(2‐vinyloxy)ethoxy]hexane ( 3 ), 1,8‐bis[(2‐vinyloxy)ethoxy]octane ( 4 ), and 1,4‐bis[(4‐vinyloxy)butoxy]butane ( 5 ) were polymerized with the hydrogen chloride/zinc chloride (HCl/ZnCl₂) initiating system in methylene chloride (CH₂Cl₂) at 0 °C at low initial monomer concentration ([M]₀ = 0.15 M). The polymerizations of divinyl ethers 2 and 3 gave soluble polymers quantitatively. In contrast, the polymerizations of divinyl ethers 1 , 4 , and 5 underwent gel formation at high monomer conversion. The content of the unreacted vinyl groups of the obtained soluble polymers was measured by ¹H NMR spectroscopy. Judging from the relatively low vinyl contents of the polymers produced even in the early stage of the polymerization (monomer conversion < ～20%), the cyclopolymerization occurred to some extent for 2 , 3 , and 4 . On the contrary, the polymers produced from 1 and 5 exhibited the relatively high vinyl content, indicating that the cyclopolymerization tendencies of 1 and 5 were lower than those of 2 , 3 , and 4 . These results are discussed in terms of the structural variety of the spacer chains: (1) the presence of benzene ring ( 1 vs 2 ), (2) their length ( 2 vs 3 and 4 ), and (3) the position of ether oxygen ( 4 vs 5 ). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4002–4012, 2002     

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     

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     

Gel formation in cationic polymerization of divinyl ethers. III. Effect of oligooxyethylene chain versus oligomethylene chain as central spacer units

Cationic polymerizations of two series of divinyl ethers were carried out to clarify the effects of their central spacer chain structure on their crosslinking polymerization behavior. One series of the monomers involves divinyl ethers with an oligooxyethylene central spacer chain: diethylene glycol divinyl ether ( O‐3 ), triethylene glycol divinyl ether ( O‐4 ), tetraethylene glycol divinyl ether ( O‐5 ), pentaethylene glycol divinyl ether ( O‐6 ), and heptaethylene glycol divinyl ether ( O‐8 ) (see Scheme 1 ). The other series includes divinyl ethers with an oligomethylene central spacer chain: 1,4‐butanediol divinyl ether ( C‐4 ), 1,6‐hexanediol divinyl ether ( C‐6 ), and 1,8‐octanediol divinyl ether ( C‐8 ). Cationic polymerizations of these monomers were carried out with the hydrogen chloride/zinc chloride (HCl/ZnCl₂) initiating system in methylene chloride (CH₂Cl₂) at ?30 °C ([Monomer]₀ = 0.15 M; [HCl]₀ = 5.0 mM; [ZnCl₂]₀ = 0.5 mM). The polymerizations of the oligomethylene‐based divinyl ethers C‐6 and C‐8 caused gel formation at high monomer conversions (～90%), whereas C‐4 formed soluble polymers even at almost 100% monomer conversion. The oligooxyethylene‐based divinyl ethers O‐3 , O‐4 , O‐5 , and O‐6 underwent gel‐free polymerizations up to 100% monomer conversion and O‐8 did so at least up to ～80% conversion. The content of unreacted pendant vinyl groups of the obtained soluble polymers was measured by ¹H NMR spectroscopy. In the polymerizations of the oligomethylene‐based divinyl ethers ( C‐4 , C‐6 , and C‐8 ), the vinyl contents of the polymers decreased monotonously with increasing monomer conversion, and their number‐average molecular weights (M_n's) and polydispersity ratios (M_w/M_n's) increased considerably just before the gelation occurred. On the contrary, the vinyl contents of the polymers obtained from the oligooxyethylene‐based divinyl ethers ( O‐3 , O‐4 , O‐5 , O‐6 , and O‐8 ) decreased steeply even in the early stage of the polymerizations and almost all the pendant vinyl ether groups were consumed in the soluble polymers at the final stage of the polymerizations. The oligooxyethylene spacer units adjacent to the pendant unreacted vinyl ether groups may solvate intramolecularly with the carbocationic active center to accelerate frequent occurrence of intramolecular crosslinking reactions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3729–3738, 2004     

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     

Living cationic polymerization of α‐methyl vinyl ethers using SnCl4

Cationic polymerization of α‐methyl vinyl ethers was examined using an IBEA‐Et_1.5AlCl_1.5/SnCl₄ initiating system in toluene in the presence of ethyl acetate at 0 ～ ?78 °C. 2‐Ethylhexyl 2‐propenyl ether (EHPE) had a higher reactivity, compared to corresponding vinyl ethers. But the resulting polymers had low molecular weights at 0 or ?50 °C. In contrast, the polymerization of EHPE at ?78 °C almost quantitatively proceeded, and the number‐average molecular weight (M_n) of the obtained polymers increased in direct proportion to the EHPE conversion with quite narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight ≤ 1.05). In monomer‐addition experiments, the M_n of the polymers shifted higher with low polydispersity as the polymerization proceeded, indicative of living polymerization. In the polymerization of methyl 2‐propenyl ether (MPE), the living‐like propagation also occurred under the reaction conditions similar to those for EHPE, but the elimination of the pendant methoxy groups was observed. The introduction of a more stable terminal group, quenched with sodium diethyl malonate, suppressed this decomposition, and the living polymerization proceeded. The glass transition temperature of the obtained poly(MPE) was 34 °C, which is much higher than that of the corresponding poly(vinyl ether). This poly(MPE) had solubility characteristics that differed from those of poly(vinyl ethers). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2202–2211, 2008     

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     

Antithetic function of alcohol in living cationic polymerization: From terminator/inhibitor to useful initiator

We employed alcohols as initiators for living cationic polymerization of vinyl ethers and p‐methoxystyrene, coupled with tolerant Lewis acid, borontrifluoride etherate (BF₃OEt₂), although they were known to be poisonous reagent to bring about chain‐breaking such as chain transfer/termination rather than such beneficial one for propagation and polymerization‐control. As well known, without assistance of additive, ill‐defined polymers with broad molecular weight distributions (MWDs) were produced. Even addition of conventional oxygen‐based bases, for example, ethyl acetate (AcOEt), 1,4‐dioxane (DO), tetrahydrofran (THF), and diethyl ether (Et₂O) was less efficient in this system to control molecular weights and MWDs (M_w/M_n > 2.0). In contrast, by addition of dimethyl sulfide (Me₂S), MWDs of the resultant polymers became much narrower (M_w/M_n < 1.23) and the number‐average molecular weight (M_n) increased in direct proportion to monomer conversion in agreement with the calculated values assuming that one alcohol molecule generates one polymer chain. Studying changed feed‐ratio of alcohol to monomer and structural analyses with NMR and MALDI‐TOF‐MS indicated that quantitative initiation from alcohol giving alkoxide counteranion. This system opens a new way to use a variety of alcohols as initiators, which would allow us to design variety of structures and functions of counteranion. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4194–4201, 2009     

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     

Expanding vinyl ether monomer repertoire for ring-expansion cationic polymerization: Various cyclic polymers with tailored pendant groups

Herein, we clarified the ring-expansion cationic polymerization with a cyclic hemiacetal ester (HAE)-based initiator was versatile in terms of applicable vinyl ether monomers. Although there was a risk that higher reactive vinyl ethers may incur β-H elimination of the HAE-based cyclic dormant species to irreversibly give linear chains, the polymerizations were controlled to give corresponding cyclic polymers from various alkyl vinyl ethers of different reactivities. Functional vinyl ether monomers were also available, and for instance a vinyl ether monomer carrying an initiator moiety for metal-catalyzed living radical polymerization in the pendant allowed construction of ring-linear graft copolymers through the grafting-from approach. Furthermore, ring-based gel was prepared via the addition of divinyl ether at the end of the ring-expansion polymerization, where multi HAE bonds cyclic polymers or fused rings were crosslinked with each other. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3082–3089     

Vinyl ether end‐groups in poly(ethylene glycol)s from the Na2CO3‐promoted degradation of 1,3‐dioxolan‐2‐one polymers

The Na₂CO₃‐promoted polymerization of 1,3‐dioxolan‐2‐one (I) to afford poly(ethylene glycol) III was reinvestigated. The reaction appeared to involve a nucleophilic attack against the carbonyl and methylene groups of I to afford poly(carbonate) II with poly(ethylene glycol) linkages and ethylene oxide IV as a side product (10–22%). As the reaction progressed, poly(carbonate) II decreased and poly(ethylene glycol) III increased. Under some conditions, poly(ethylene glycol)s V and VI with vinyl ether terminal groups were formed unexpectedly. The formation of unsaturated products during the polymerization of I/EO (ethylene oxide) has not been reported in the literature. We believe that vinyl ethers were formed from the degradation of poly(carbonate)s and were accompanied by a reduction in molecular weight. The structures of vinyl ethers V and VI were confirmed by hydrogenation of the double bond into the ethyl ether group in VII and VIII, respectively. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 152–160, 2000     

Novel copolymer networks via the combination of polyaddition and anionic polymerization

A two‐step synthetic route to novel copolymer networks, consisting of polymethacrylate and polyacetal components, was developed by combining the polyaddition and anionic polymerization techniques. The functional polymethacrylates containing hydroxyl or vinyloxyl side groups were used as crosslinkers. They were anionically synthesized as follows: the copolymer of 2‐hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA) was prepared by the anionic copolymerization of 2‐(trimethylsiloxy)ethyl methacrylate and MMA, followed by hydrolysis. The copolymer poly(HEMA‐co‐MMA) thus obtained possessed a hydroxyl group in each of its HEMA units. Another kind of vinyloxyl‐containing (co)polymer was prepared by the anionic homopolymerization of 2‐(vinyloxy)ethyl methacrylate (VEMA) or its copolymerization with MMA. The resulting (co)polymer possessed reactive vinyloxyl side groups. The copolymer networks were obtained by reacting each of the above‐mentioned (co)polymers with a polyacetal prepared via the polyaddition between a divinyl ether and a diol. Three divinyl ethers (ethylene glycol divinyl ether, 1,4‐butanediol divinyl ether, and 1,6‐hexanediol divinyl ether) and three diols (ethylene glycol, 1,4‐butanediol, and 1,6‐hexanediol) were employed as monomers in the polyaddition step, and their combinations generated nine kinds of polyacetals. When a polyaddition reaction was terminated with a divinyl ether monomer, a polyacetal with two vinyloxyl end groups was obtained, which could further react with the hydroxyl groups of poly(HEMA‐co‐MMA) to generate a copolymer network. On the other hand, when a diol was used as terminator in the polyaddition, the resulting polyacetal possessed two hydroxyl end groups, which could react with the vinyloxyl groups of poly(VEMA) or poly(VEMA‐co‐MMA), to generate a copolymer network. All the copolymer networks exhibited degradation in the presence of acids. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 117–126, 2001     

Relative thermodynamic stabilities of allyl vinyl and propenyl vinyl ethers

The relative thermodynamic stabilities of a number of isomeric allyl vinyl and propenyl vinyl ethers were determined by chemical equilibration in DMSO solution with KOBu-t as catalyst. From the temperature dependence of the values of the equilibrium constant the parameters G _m , H _m and S _m of isomerization at 298.15 K were evaluated. Propenyl vinyl ethers, owing to their low enthalpy contents, are much more stable than the isomeric allyl vinyl ethers. It appears that in the parent propenyl vinyl ether, the Me group attached to C- of the divinyl ether skeleton has a strong stabilizing effect, comparable to that of alkyl groups in ordinary olefins, on the unsaturated system. In more heavily alkyl-substituted divinyl ethers, however, the stabilizing effects of alkyl groups are less prominent, being comparable to the low stabilization energies of alkyl groups in vinyl ethers, and depend moreover, on the pattern of substitution.     

Living cationic polymerization of vinyl ethers with a functional group. VII. Polymerization of vinyl ethers with a silyloxyl group and synthesis of polyalcohols and related functional polymers

Living cationic polymerizations of two silicon-containing vinyl ethers, 2-(t-butyldimethyl-silyloxyl)ethyl vinyl ether (tBuSiVE) and 2-(trimethylsilyloxyl)ethyl vinyl ether (MeSiVE), have been achieved with use of the hydrogen iodide/iodine (HI/I₂) initiating system in toluene at ?15 or ?40°C, despite the existence of the acid-sensitive silyloxyl pendants. The living nature of the polymerizations was demonstrated by linear increases in the number-average molecular weights (M?_n) of the polymers in direct proportion to monomer conversion and by their further rise upon addition of a second monomer feed to a completely polymerized reaction mixture. The polymers obtained in these experiments all exhibited very narrow molecular weight distributions (MWD) with M?_w/M?_n around or below 1.1. Desilylation of the polymers under mild conditions (with H⁺ for MeSiVE and F^? for tBuSiVE) gave poly(2-hydroxyethyl vinyl ether), a water-soluble polyalcohol with a narrow MWD. The living processes also permitted clean syntheses of amphiphilic AB block copolymers and water-soluble methacrylate-type macromonomers, all of which bear narrowly distributed segments of the polyalcohol derived from the silicon-containing vinyl ethers.     

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 cationic polymerization of 2‐adamantyl vinyl ether

Living cationic polymerization of 2‐adamantyl vinyl ether (2‐vinyloxytricyclo[3.3.1.1]^3,7decane; 2‐AdVE) was achieved with the CH₃CH(OiBu)OCOCH₃/ethylaluminum sesquichloride/ethyl acetate [CH₃CH(OiBu)OCOCH₃/Et_1.5AlCl_1.5/CH₃COOEt] initiating system in toluene at 0 °C. The number‐average molecular weights (M_n's) of the obtained poly(2‐AdVE)s increased in direct proportion to monomer conversion and produced the polymers with narrow molecular weight distributions (MWDs) (M_w/M_n = ～1.1). When a second monomer feed was added to the almost polymerized reaction mixture, the added monomer was completely consumed and the M_n's of the polymers showed a direct increase against conversion of the added monomer. Block and statistical copolymerization of 2‐AdVE with n‐butyl vinyl ether (CH₂?CH? O? CH₂ CH₂CH₂CH₃; NBVE) were possible via living process based on the same initiating system to give the corresponding copolymers with narrow MWDs. Grass transition temperature (T_g) and thermal decomposition temperature (T_d) of the poly(2‐AdVE) (e.g., M_n = 22,000, M_w/M_n = 1.17) were 178 and 323 °C, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1629–1637, 2008     

From linear side-chain functionalized poly(vinyl ether)s to functional macrocycles

This paper deals with the synthesis of functional polymers of controlled chain dimensions and architecture from poly(chloroalky1 vinyl ether)s. The living polymerization of chloroalkyl vinyl ethers initiated by HX/ZnX₂ systems, and the chemical substitution of the pendant chlorines by various organic functions and groups, in order to generate specific polymer properties are first discussed. Also based on the living character of the polymerizations, the preparation of poly(chloroethyl vinyl ether) with monomacrocyclic and plurimacrocyclic architectures as well as their characterization are then reported. Some evidence for specific host–guest interactions between large organic molecules and polymacrocycles is also presented.     

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     

Radical copolymerization of 2‐trifluoromethylacrylic monomers. II. Kinetics,monomer reactivities,and penultimate effect in their copolymerization with norbornenes and vinyl ethers

Radical copolymerizations of electron‐deficient 2‐trifluoromethylacrylic (TFMA) monomers, such as 2‐trifluoromethylacrylic acid and t‐butyl 2‐trifluoromethylacrylate (TBTFMA), with electron‐rich norbornene derivatives and vinyl ethers with 2,2′‐azobisisobutyronitrile as the initiator were investigated in detail through the analysis of the kinetics in situ with ¹H NMR and through the determination of the monomer reactivity ratios. The norbornene derivatives used in this study included bicyclo[2.2.1]hept‐2‐ene (norbornene) and 5‐(2‐trifluoromethyl‐1,1,1‐trifluoro‐2‐hydroxylpropyl)‐2‐norbornene. The vinyl ether monomers were ethyl vinyl ether, t‐butyl vinyl ether, and 3,4‐dihydro‐2‐H‐pyran. Vinylene carbonate was found to copolymerize with TBTFMA. Although none of the monomers underwent radical homopolymerization under normal conditions, they copolymerized readily, producing a copolymer containing 60–70 mol % TFMA. The copolymerization of the TFMA monomer with norbornenes and vinyl ethers deviated from the terminal model and could be described by the penultimate model. The copolymers of TFMA reported in this article were evaluated as chemical amplification resist polymers for the emerging field of 157‐nm lithography. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1478–1505, 2004     

Reversible addition-fragmentation chain transfer cyclopolymerization of dimethacryloyl open-cage silsesquioxane

We recently reported a bifunctional methacrylate monomer having a side-opened cage-silsesquioxane as a scaffold. Although free-radical polymerization proceeded mainly through cyclopolymerization, cross-linking structures were included. In this work, we have optimized the reaction conditions for reversible addition-fragmentation chain transfer cyclopolymerization using 2-cyano-2-propyl dithiobenzoate. As a result, polymers with relatively low polydispersity indices were successfully obtained. After removal of dithiobenzoate end groups, the transparency was high (>98%) in the range of visible range (400–800 nm). The content of the unreacted dangling vinyl groups, which was controlled by monomer concentration, affected the thermal stability of the resulting polymers. In addition, the bifunctional cage-silsesquioxane monomer can be readily copolymerized with methyl methacrylate without cross-linking.