Synthesis of end-functionalized polymers by living cationic polymerization of isobutyl vinyl ether with EtAlCl2

Summary A series of end-functionalized polymers (4), carrying a hydroxyl, carboxyl, or primary amino terminal group Y, were obtained by living cationic polymerization of isobutyl vinyl ether. The initiating systems of choice consisted of EtAlCl₂ and the trifluoroacetate [2; X-CH₂CH₂OCH(CH₃)OOCCF₃; X = OOCCH₃, CH(COOC₂H₅)₂, N(COOC(CH₃)₃)₂] obtained from a vinyl ether with a protected functional pendant group. In the presence of 1,4-dioxane, the 2/EtAlCl₂ systems invariably induced a well-defined living polymerization of isobutyl vinyl ether in n-hexane at 0 to +40°C to give polymers, the -end group (X) of which was derived from the initiator 2. Subsequent de-protection of X of these polymers led to 4, all of which were shown to have a very narrow molecular weight distribution (¯M_W/¯M_n = 1.07–1.18), a number-average molecular weight (¯M_n = 10³-10⁴) controllable by the monomer/2 molar feed ratio, and one terminal function Y per chain.     

Synthesis of a novel comb-like poly(vinyl ether) with isopropylnaphthoxy pendant by cationic polymerization

Summary A novel comb-like polymer having isopropylnaphthoxy pendant with the controlled molecular structure was synthesized by the cationic polymerization of 2-(6-isopropyl-2-naphthoxy)ethyl vinyl ether with AlEtCl₂ catalyst. Although the polymer's molecular weight (Mn: 4,000–17,000) could be controlled by the reaction conditions (sovent polarity, temperature and initial monomer concentration), the steric structure was not affected by them at all, giving almost the same amount of the meso and racemic diads irrespective of the conditions. The polymer showed only an amorphous character (Tg: 22–45 °C) but not any liquid crystalline phase.     

Living cationic polymerization of isobutyl vinyl ether (II): Photoinduced living cationic polymerization in a mixed solvent of toluene and diethyl ether

A new method of preparation of living cationic polymer of isobutyl vinyl ether via photoinduced polymerization in the presence of diphenyliodonium iodide (DPII, initiator) and zinc iodide in a mixed solvent of toluene/diethyl ether, which was irradiated at ?78°C for short period, was completed within 15 min. The reaction was allowed for further reaction in the dark until monomer was fully consumed. It was found that increase in the conversion of monomer to polymer during the irradiation is very limited. Confirmation of the linear dependence of number‐average molar mass of resulting polymer on % conversion together with the fact that polymerization proceeds until monomer consumption, and controllability of number‐average molar mass of resulting polymer, depending on the molar ratio of monomer and initiator, strongly suggests the living nature of this polymerization, unless reaction temperature becomes higher than 0°C, i.e., the absence of chain breaking process. The narrow molar mass distribution, whose polydispersity index values are less than 1.2, reveals that the rate of initiation where irradiation is usually completed within 15 min is much faster than that of propagation in cationic nature in this system. Effect of some major factors, such as solvent polarity and temperature, on the living nature of the polymerization was also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3581–3586, 2006     

Block copolymers of poly(vinyl ethers) and poly(ethylene glycol) by means of the living cationic polymerization of vinyl ethers

Summary If living poly(vinyl ethers) are terminated with a large excess of methanol, containing aqueous ammonia, well-defined products are obtained. If only a slight excess of methanol is used, aldehydes and coupling products are formed. However, termination with an excess of a hydroxy terminated polymer is cumbersome. According to a given reaction scheme, the termination with methanol in the presence of an anhydrous organic base, should give better results. With two equivalents of triethylamine with respect to the initiator only two equivalents of methanol are needed to give a clean reaction. With this recipe block copolymers of poly(vinyl ether) and poly(ethylene glycol) are prepared.     

Synthesis of sulfonated poly(phthalazinone ether sulfone)s by direct polymerization

Sulfonated poly(phthalazinone ether sulfone)s with high molecular weight were directly prepared by polycondensation of 4-(4-hydroxyphenyl) phthalazinone with various ratios of disodium 5.5′-sulfonylbis(2-fluoro-benzenesulfonate) to 4-fluorophenyl sulfone. The resulting ionomers with high IEC showed low swelling. The low swelling originates from intermolecular hydrogen bonds, which is confirmed by variable temperature IR spectroscopy. The membranes show very good perspectives in PEMFC applications.     

Highly isotactic poly(vinyl alcohol). III: Heterogeneous cationic polymerization of tert-butyl vinyl ether

We studied the polymerization of tert-butyl vinyl ether (tBVE) and benzyl vinyl ether with heterogeneous catalysts, that is, modified Ziegler type (Vandenberg type) catalysts and metal sulfate-sulfuric acid complexes.Vandenberg type catalysts gave high molecular weight and highly isotactic poly(tBVE)s with relatively narrow molecular weight distribution at high temperature, and then the resultant poly(tBVE)s were converted into the stereoregular poly(vinyl alcohol)s (PVAs). With titanium based Vandenberg type catalyst, a relative high isotactic PVA, which has 52% triad isotacticity, was obtained from the poly(tBVE) polymerized at 30 °C. It was found from NMR study that the content of the triad tacticity of PVAs derived from poly(tBVE) catalyzed by titanium based catalysts agreed with the value calculated from the chain-end control model (Bovey's model). This fact suggests that the steric structure of the adding monomer in this system is determined by same mechanism to homogeneous BF₃ complexes catalysts system. On contrast to that, the metal sulfate-sulfuric acid complexes show significantly low activity to tBVE polymerization.     

Photochemically initiated free radical promoted living cationic polymerization of isobutyl vinyl ether

A new photoinitiating system for living cationic polymerization of vinyl ethers such as isobutyl vinyl ether (IBVE) has been reported. The photoinitiating system comprises free radical photoinitiators such as 2,2-dimethoxy-2-phenyl acetophenone (DMPA), benzophenone or thioxanthone, together with an onium salt, such as diphenyliodonium chloride and zinc bromide. In the first step, photochemically generated free radicals are oxidized to the corresponding carbocations which subsequently react with vinyl ether monomer to yield an adduct. In the presence of zinc salt, this adduct initiates living cationic polymerization of IBVE.     

Synthesis of well‐defined poly(vinyl ether)‐based macromonomers having pendant glycerols via living cationic polymerization and their application to the preparation of core−shell polymer particles

A new vinyl ether monomer bearing a glycerol pendant moiety protected with an isopropylidene group (2‐(2,2‐dimethyl‐[1,3]dioxolan‐4‐ylmethoxy)‐ethyl vinyl ether, IpGEVE) was designed as the precursor of a novel type of hydrophilic poly(vinyl ether) containing glycerol pendants. It was found that the polymerization of IpGEVE proceeded in a controlled manner, and the protecting groups of isopropylidene moieties could be cleaved with trifluoroacetic acid. Living cationic polymerization of IpGEVE with an initiator bearing a methacryloyl group (VEM‐HCl) and subsequent deprotection of the pendant isopropylidene groups of the resultant precursor afforded a glycerol‐substituted hydrophilic macromonomer MA‐PGEVE. Nearly monodispersed polymer particles in the submicron size range were successfully obtained via dispersion copolymerization of MA‐PGEVE with styrene.© 2013 Society of Chemical Industry     

Synthesis of polyvinyl alcohol stereoblock copolymer via the combination of living cationic polymerization and RAFT/MADIX polymerization using xanthate with vinyl ether moiety

Different types of novel xanthates containing a vinyl ether moiety, S-benzyl O-2-(vinyloxy)ethyl carbonodithioate (Xanthate 1) and S-1-(ethoxycarbonyl)ethyl O-2-(vinyloxy)ethyl carbonodithioate (Xanthate 2) were synthesized. In particular, the Xanthate 2 enabled to design polyvinyl alcohol (PVA) stereoblock copolymer via the combination of living cationic vinyl polymerization and RAFT/MADIX polymerization. For cationic polymerization of isobutyl vinyl ether (IBVE) and tert-butyl vinyl ether (TBVE), the polymerizations were conducted under Xanthate 1-HCl adduct/SnCl₄ and Xanthate 1 or 2-CF₃COOH adduct/EtAlCl₂ initiating system in the presence of ethyl acetate. Both systems proceeded in living polymerization fashion because the calculated M_n of both poly(IBVE) and poly(TBVE) matches with the M_n polymerized assuming that one polymer chain is formed per one molecule of the Xanthate 1 or 2. The resulting poly(TBVE) had a high number average α-end functionality as determined by MALDI-TOF-MS spectrometry. Xanthate 2 is more efficient for the following RAFT/MADIX polymerization of vinyl acetate (VAc). The RAFT/MADIX polymerization of vinyl acetate (VAc) using azobis(isobutyronitrile) (AIBN) at 60 °C was conducted using either poly(IBVE) or poly(TBVE) macro-CTA. The poly(TBVE) macro-CTAs synthesized from the Xanthate 2 were able to polymerize VAc smoothly via RAFT/MADIX polymerization, to prepare well-defined diblock copolymer, poly(TBVE)-b-poly(VAc). The resulting block copolymer was then hydrolyzed using KOH in methanol and followed by acid hydrolysis using HBr gas bubbling. The resulting polymer is inherently stereoblock like copolymer, isotactic rich PVA-b-atactic PVA (iPVA-b-aPVA). From the DSC measurement, the iPVA-b-aPVA has one glass transition at 69.5 °C and two melting points according to iPVA and aPVA at 237.9 and 198.1 °C, respectively. Thus, it can be suggested that the obtained PVA has two different geometries by the combination of living cationic polymerization and RAFT/MADIX polymerization.     

Synthesis of poly(vinyl alcohol)s with narrow molecular weight distribution from poly(benzyl vinyl ether) precursors

Summary A series of poly(benzyl vinyl ether)s of low molecular weight (5000 to 15000 g mol^-1) and narrow molecular distribution ( ) have been synthesisedvia the cationic polymerisation of benzyl vinyl ether. Acetylation with acetic anhydride/tin (IV) chloride leads to poly(vinyl acetate), which can be hydrolysed to near-monodisperse water-soluble poly(vinyl alcohol) with an isotacticity of approximately 47%. This polymer was re-acetylated and its molecular weight distribution assessed to confirm that hydrolysis gives minimal chain scission.     

水相微悬浮聚合法氯醚树脂的合成及表征

以氯乙烯(VC)和乙烯基异丁基醚(VIBE)为单体,过氧化十二酰为引发剂,羟丙基纤维素、聚乙烯醇和十二烷基苯磺酸钠为微悬浮分散剂,通过水相微悬浮聚合法合成了氯醚树脂,研究了反应参数对聚合反应的影响,并用傅里叶变换红外光谱、核磁共振氢谱、差示扫描量热分析和热重分析对产物的结构进行了表征。结果表明,在VC∶VIBE(质量比)为1.5∶1.0、引发剂用量为单体质量的0.75%、聚合温度为70～75℃的最佳合成条件下,可制得含氯质量分数为43.63%的氯醚树脂;产物中的VC∶VIBE(摩尔比)为5.68∶1,玻璃化转变温度为-18℃,熔点为53℃,熔融热为5.34 J/g;氯醚树脂的最佳干燥温度为40℃。     

Thermal characterization of poly(vinyl chloride) samples prepared by living radical polymerization: Comparison with poly(vinyl chloride) prepared by free radical polymerization

Poly(vinyl chloride) (PVC) samples were synthesized by a living radical polymerization (LRP) method and compared with commercial PVC prepared by the conventional free radical polymerization (FRP). The differences were assessed, for the first time, in terms of viscosimetry parameters and thermal analysis. The LRP method used to prepare the PVC‐LRP samples is the only one available to obtain this polymer free of structural defects, being of commercial interest in a view of preparing a new generation of PVC‐based polymer with outstanding performance. The polymerization temperature selected (35°C) to prepare the LRP samples is currently used in the industry to prepare PVC‐FRP grades with moderate to high molecular weight. Since the thermal stability is a direct consequence of the polymer structure, this study is of vital importance to understand the potential of new PVC‐LRP. The thermoanalytical measurements demonstrate an enhanced thermal stability of PVC‐LRP when compared with its FRP counterpart. The PVC‐LRP sample with very low molecular weight reveals a higher thermal stability than the most stable PVC‐FRP sample. It is the first report dealing with thermal analysis of PVC prepared by LRP. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of poly(vinyl alcohol) combs via MADIX/RAFT polymerization

Poly(vinyl acetate) combs have been prepared via macromolecular design via interchange of xanthate (MADIX)/reversible addition-fragmentation chain-transfer (RAFT) polymerization using xanthate functionalized polymer cores. The comb backbones were prepared using well-defined poly(vinyl alcohol) PVA polymers with a degree of polymerization of 20, 100 and 170, respectively. Functionalization with xanthates via R-group or a Z-group approach resulted in the formation of macromolecular MADIX agents. While Z group designed macromolecular xanthate agents appeared to inhibit the polymerization of vinyl acetate (VAc), R group designed macromolecular xanthate agents achieved to mediate efficiently the bulk polymerization of VAc affording PVAc combs. However, the growth of the combs was accompanied at low conversions by the formation of linear polymer chains as a result of the constant initiation (AIBN) and shoulders, which can be attributed to intermolecular coupling reactions. The proportions of single chains and termination products were observed to increase with the degree of polymerization of the macromolecular MADIX agents broadening the molecular weight distribution. As a result of a stable ester link between the branches and the PVA backbone, the branched PVAc architectures were finally hydrolyzed to afford poly(vinyl alcohol) combs.     

Preparation of ester terminated poly(alkyl vinyl ether) oligomers and block copolymers using a combination of living cationic and group transfer polymerization

Summary This paper reports the synthesis and characterization of new, functionalized poly(alkyl vinyl ether) oligomers, and block copolymers containing poly(alkyl vinyl ether) and poly(methyl methacrylate). Using the HI/ZnI₂ initiating system in nonpolar solvents (hexane, toluene) at -15 °C, both monofunctional and difunctional poly(alkyl vinyl ether) oligomers of predicted molecular weights precisely terminated with ester end groups have been prepared. Novel diblock copolymers comprised of poly(methyl methacrylate) and poly(alkyl vinyl ether) have also been synthesized using a combination of living cationic and living group transfer polymerization (GTP) techniques.     

Synthesis of hydrophilic poly(vinyl ether)s and their application for separation media design

Poly(2-acetoxyethyl vinyl ether (AcOVE)) and poly(2-acetoxyethyl vinyl ether-co-2-vinyloxyethyl phthalimide) were synthesized by traditional cationic polymerization, typically at −20°C in toluene with BF₃O(C₂H₅)₂ as initiator, to give polymers with degrees of polymerization (Dp) in the range of 600–1100. In addition, poly(AcOVE) was polymerized by controlled cationic polymerization at 0°C with molecular weights in a predetermined fashion. The Dp's were calculated from Dp = [M]₀/[I]₀ and typical values were 5, 10, 100 and 200. The molecular weight values obtained for a theoretical Dp = 200, were for poly(2-acetoxyethyl vinyl ether), M_n = 19,200, M_w = 22,700 and POLYDISPERSITY = 1.2, as determined by GPC. The deprotected hydrophilic polymers, poly(2-hydroxyethyl vinyl ether) and poly(2-hydroxyethyl vinyl ether-co-2-aminoethyl vinyl ether), were used for the preparation of novel gel filtration media as well as new anion exchangers. In the case of gel filtration, poly(2-hydroxyethyl vinyl ether) was attached to a beaded agarose matrix (34 μm), i.e. Sepharose® HP. It was shown that the attachment of the poly(vinyl ether) affected the selectivity. In gel filtration of selected biomolecules, the poly(vinyl ether) modified agarose matrix showed performance characteristics comparable to the reference used, i.e. Superdex® 30 prep grade. In addition the poly(vinyl ether)s were shown to be stable in a wide pH-range. The stability was confirmed by the conclusion that no changes in molecular weight were observed after treatment with 0.1 M HCl (pH = 1) or 0.01 M NaOH (pH = 12) for six weeks at 40°C. For the preparation of anion-exchanger media, the beads containing poly(2-hydroxyethyl vinyl ether) was further modified with a quaternary ammonium group, to produce a separation media having a high dynamic binding capacity for bovine serum albumin (BSA).     

Radiopaque iodinated ethers of poly(vinyl iodobenzyl ether)s: Synthesis and evaluation for endovascular embolization

Leachable‐free radiopaque iodinated polymers were designed as long‐lived embolization materials visible by X‐ray tomography. This is a definite improvement over liquid embolics incorporating either radiopaque inorganic particles or iodinated polymers having hydrolysable ester bonds. Grafting 4‐iodobenzyl or 2,3,5‐triiodobenzyl groups to poly(vinyl alcohol) (PVAL) yields iodobenzyl ethers of PVAL having iodine contents in the range 40–70 wt %. Their solubility in solvents accepted for medical devices (DMSO and NMP), viscosity of concentrated solutions, precipitation behavior, radiopacity, and stability with respect to sterilization and hydrolysis were assessed. The solvent NMP allows the preparation of concentrated solutions of suitable viscosity for their application as liquid embolics. Precipitation in water yields a cohesive mass of material that can plug vascular malformations. A rationale to the properties is given in terms of the Hansen contributions to the Hildebrand solubility parameters. Iodobenzyl ethers of PVA resist hydrolysis whereas their corresponding iodobenzoyl esters leach iodinated fragments. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41791.     

Synthesis of end-group functionalized poly(octadecyl vinyl ether)

The cationic polymerization of octadecyl vinyl ether (ODVE) initiated by trimethylsilyl iodide and 1,1-diethoxyethane in the presence of ZnI₂ in toluene at 0°C and 10°C has been investigated. For molecular weights lower than 6000, a linearity of M̄_n with conversion was observed, but for higher molecular weights a strong deviation from calculated values, assuming a living mechanism, was found. Kinetic analysis of the polymerization and the variation of molecular weight as a function of conversion was in agreement with a transfer to monomer with k_tr/k_p ≌ 0.006 at 10°C. Analysis of the polymers obtained by termination with methanol provided evidence that the alkenyl ether end-groups formed by the transfer reaction lead to the same acetal end-groups as the active species. As a consequence, it is possible to prepare functionalized polyODVE polymers by end-capping with alcohols. This was confirmed by the synthesis of polyODVE macromonomers by end-capping with 2-hydroxyethyl methacrylate.     

Synthesis of dendritic poly(arylene ether)s from a linear polymer core

Three generations of dendritic poly(arylene ether)s with terminal 4-fluorophenylthio- or 4-fluorophenylsulfonyl groups have been synthesized. A new relatively high molecular weight bisphenol containing two pendent 4-fluorophenylthio groups was converted to a poly(arylene ether sulfone) to act as the dendritic core. A divergent approach with an activation/condensation sequence was used. The pendent 4-fluorophenylthio groups in the base polymer were oxidized with H₂O₂ in formic acid to give 4-fluorophenylsulfonyl groups in which the fluoride groups are then activated toward nucleophilic displacement reactions. The condensation step involved the reaction of a phenol containing two pendent 4-fluorophenylthio groups with the activated core polymer in the presence of Cs₂CO₃. Reiteration of these steps gave the subsequent generations. The polymers have high thermal stabilities by TGA analysis (5% weight loss>500 °C).     

Synthesis of novel sulfonium salts and cationic polymerization of epoxides and vinyl ether

Novel 1‐methoxycarbonylethylmethylphenylsulfonium salts with nonnucleophilic anions, namely, hexafluorophosphate, hexafluoroantimonate, and tetrafluoroborate, were synthesized by the reaction of 1‐methoxycarbonylethylphenylsulfide and dimethyl sulfate followed by anion exchange with potassium hexafluorophosphate, sodium hexafluoroantimonate, and sodium tetrafluoroborate, respectively. The cationic polymerization (photopolymerization and thermal polymerization) of epoxy and vinyl ether monomers was carried out to demonstrate the applicability of the newly synthesized sulfonium salts. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3157–3163, 2007