Perfluorinated polymer film with functional group prepared by radiation-induced grafting

A perfluorinated vinyl ether monomer, 2-bromotetrafluoroethyl trifluorovinyl ether (BrTFF) was grafted into crosslinked poly(tetrafluoroethylene) (cPTFE) films by γ-rays irradiation under different conditions. The irradiation with absorbed doses more than 550 kGy gave the poly(BrTFF) grafted cPTFE membranes with grafting yields of more than 20%. FTIR spectra and SEM-EDS testified that BrTFF was successfully grafted into cPTFE films homogeneously in the film perpendicular direction. TGA analysis of the grafted films indicated that the perfluorinated poly(BrTFF) grafts were phase-separated from the PTFE region due to the crosslinked structure of the cPTFE based film, but the grafted films still had high thermal stability (above 300 °C). DSC measurements showed the decrease of melting temperature, but the increase of both heat of fusion and degree of crystallinity in cPTFE film after grafting. The grafted film, a new kind of perfluorinated polymer with bromine active groups and good mechanical properties, is expected to be modified for new applications.     

Radical copolymerization behavior of a highly fluorinated cyclic olefin with vinyl ether

The copolymerization of a highly fluorinated cyclic monomer, octafluorocyclopentene (OFCPE, M₁), with ethyl vinyl ether (EVE, M₂) was investigated with a radical initiator in bulk. Despite the poor homopolymerizability of each monomer, the copolymerization proceeded successfully, and the molecular weights of the copolymers reached up to more than 10,000. Incorporation of the OFCPE units into the copolymer led to an increase in the glass‐transition point. The copolymer composition was determined from ¹H NMR spectra and elemental analysis data. The molar fraction of the OFCPE unit in the copolymer increased and approached but did not exceed 0.5. The monomer reactivity ratios were estimated by the Yamada–Itahashi–Otsu nonlinear least‐squares procedure as r_1,OFCPE = ?0.008 ± 0.010 and r_2,EVE = 0.192 ± 0.015. The reactivity ratios clearly suggest that the copolymerization proceeds alternatively in the case of an excessive feed of OFCPE. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1151–1156, 2002     

Synthesis of silicon-containing vinyl ether monomers and oligomers and their photoinitiated polymerization

Silicon-containing divinyl ether monomers were synthesized by the addition reaction of glycidyl vinyl ether ( 1 ) with various silyl dichlorides using tetra-n-butylammonium bromide (TBAB) as a catalyst. The reaction of 1 with diphenyl dichlorosilane gave bis-[1-(chloromethyl)-2-(vinyloxy)-ethyl]diphenyl silane ( 3a ) in 89% yield. Polycondensations of 3a with terephthalic acid were also carried out using 1,8-Diazabicyclo[5.4.0]-7-undecene (DBU) to afford silicon-containing polyfunctional vinyl ether oligomers ( 5 ). A multifunctional Si-monomer with both vinyl ether and methacrylate groups ( 7 ) was prepared by the reaction of 3a with potassium methacrylate using TBAB as a phase transfer catalyst. Photoinitiated cationic polymerizations of these vinyl ether compounds proceeded rapidly using the sulfonium salt, bis-[4-(diphenyl-sulfonio)phenyl]sulfide-bis-hexafluorophoshate (DPSP), as the cationic photoinitiator in neat mixtures upon UV irradiation. Multifunctional monomer 7 with both vinyl ether and methacrylate groups showed “hybrid curing properties” using both DPSP and the radical photoinitiator, 2,4,6-trimethylbenzoyl diphenylphoshine oxide (TPO). © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3217–3225, 1997     

Study of the selective retention of fluorinated compounds on perfluorinated stationary phases

Summary The basis of the selective retention of perfluorinated compounds on perfluorinated bonded phases is examined. It is shown that the selective retention increases dramatically by increasing chain length and strand multiplicity.     

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     

Identification and quantification of polyethylene glycol types in polyethylene glycol methyl ether and polyethylene glycol vinyl ether

Quantitative determination of polyethylene glycol (PEG) impurities in two monofunctional polyglycol types, PEG methyl ether (M-PEG) and PEG vinyl ether (V-PEG), has been carried out by reversed-phase liquid chromatography with evaporative light scattering detection (ELSD). In addition to optimizing the resolution between PEG and monofunctional PEG peaks, the major focus has been to determine the molecular weights of PEG impurities in M-PEG and V-PEG of diverse molecular weights. The latter is achieved by examining liquid chromatography–mass spectrometry (LC–MS) mass spectra of both monofunctional PEG and PEG in several cases, and matching peak retention times with those of available PEG standards for all M-PEG and V-PEG sample types. This information is helpful in selecting the appropriate PEG standard to determine PEG content in each sample type. ELSD response factors for various PEG standards have also been compared. It has been found that PEG standards with molecular weights from 1000 Da to 8000 Da show responses that are within 10% of each other. However, a low molecular weight PEG such as PEG 400, provides approximately 30% less response compared to its higher molecular weight counterparts.     

A theoretical approach to the polymerization of N-pyrrolyl ethyl vinyl ether

The oligomerization mechanism of N-pyrrolyl ethyl vinyl ether is studied for two different routes of polymerization by using quantum mechanical calculations. Model compounds for oligomerization between monomers and monomer-pyrrole systems are optimized fully via semiempirical methods. By comparing the enthalpy changes of these two processes, it is found that generally the binding of pyrrole groups on the carbon backbone is favoured; however, the self-polymerization is also thermodynamically competitive. These results support the previous experimental evidence.     

Synthesis and characterization of amphiphilic diblock copolymers of methyl tri(ethylene glycol) vinyl ether and isobutyl vinyl ether

Water-soluble diblock copolymers of methyl tri(ethylene glycol) vinyl ether (hydrophilic block) and isobutyl vinyl ether (hydrophobic block) of different molecular weights and composition were synthesized by living cationic polymerization. The molecular weight and comonomer composition of these copolymers were determined by GPC and ¹H NMR spectroscopy, respectively. Aqueous solutions of the copolymers were characterized in terms of their micellar behavior using dynamic light scattering, aqueous GPC, and dye solubilization. All the copolymers formed aggregates with the exception of a diblock copolymer with only two hydrophobic monomer units. The micellar hydrodynamic size scaled with the 0.61 power of the number of hydrophobic units, in good agreement with a theoretical exponent of 0.73. An increase in the length of the hydrophobic block at constant hydrophilic block length or an increase in the overall polymer size at constant block length ratio both resulted in lower critical micelle concentrations (cmcs). The cloud points of 1% w/w aqueous solutions of the polymers were determined by turbidimetry. An increase in the length of the hydrophobic block at constant hydrophilic block length caused a decrease in the cloud points of the copolymers. However, an increase in the overall polymer size at constant block length ratio led to an increase in the cloud point. © 1996 John Wiley & Sons, Inc.     

N+离子注入聚对苯乙炔衍生物的非线性光学性能

以对甲氧基苯酚和溴代异戊烷为原料,用脱氯化氢反应制备可溶性聚[2-甲氧基-5-(3'-甲基)丁氧基]对苯乙炔(MMB-PPV),通过核磁氢谱(1HNMR)和红外光谱(FTIR)对产物分子的结构进行表征.用能量为15keV、剂量为3.8×1015～9.6×1016ions/cm2的氮正离子(N+)对MMB-PPV薄膜进行注入改性.紫外-可见吸收光谱(UV-Vis)显示,注入离子在MMB-PPV薄膜内部引入杂质能级,破坏了分子的共轭结构.随着注入剂量增加,吸收边逐渐向长波方向移动,且分子激发态和基态间的光学带隙由2.12eV减小至1.81eV.用简并四波混频(DFWM)技术研究了离子注入MMB-PPV薄膜的三阶非线性光学性能.结果表明,未注入薄膜的三阶非线性极化率(χ(3))值为7.1×10-10esu,随着注入剂量的增加,χ(3)值逐渐增大,当注入剂量达到3.8×1016ions/cm2时,χ(3)值提高到9.3×10-9esu,继续增加注入剂量,χ(3)值开始下降,当注入剂量为9.6×1016ions/cm2时,χ(3)值降低到1.5×10-10esu.对离子注入MMB-PPV薄膜χ(3)值变化的机理进行了探讨.     

Living cationic polymerization of isobutyl vinyl ether by the carboxyl group of the carbon black/zinc chloride initiating system

The effect of zinc chloride (ZnCl₂) on the cationic polymerization of isobutyl vinyl ether (IBVE) initiated by carboxyl groups on a carbon black surface was investigated. Although the polymerization of IBVE was initiated by carboxyl groups on the surface, the rate of polymerization was small and the molecular weight distribution (MWD) of poly IBVE was very broad. The rate of the polymerization was found to be drastically increased, and 100% monomer conversion was achieved in a short time by the addition of ZnCl₂. The number-average molecular weights (M_n) of the polyIBVE were directly proportional to monomer conversion in the polymerization initiated by the carbon black/ZnCl₂ system. By addition of the monomer at the end of the first-stage polymerization, the added monomer was smoothly polymerized at the same rate as in the first stage. The M_n of the polymer was in excellent agreement with the calculated value, assuming the polyIBVE chain forms per unit carboxyl group on the surface and MWD was narrow (M_w/M_n = 1.2 ～ 1.3). Based on the results, it is concluded that carbon black/ZnCl₂ system has an ability to initiate the living cationic polymerization of IBVE. Furthermore, it was found that polyIBVE was grafted onto the carbon black surface after the quenching of the living polymer with methanol. © 1995 John Wiley & Sons, Inc.     

Temperature-sensitive poly(vinyl methyl ether) hydrogel beads

Temperature-sensitive hydrogel beads were prepared by radiation crosslinking of poly(vinyl methyl ether) PVME spheres wrapped in Ca-alginate. The obtained gel beads have diameters in the sub-millimeter or millimeter range (depending on the PVME concentration). They were characterized by sol-gel analysis, swelling measurements, and differential scanning calorimetry. The gel content g increases with increasing radiation dose D. The swelling degree Q_v decreases with increasing PVME concentration c_p and increasing D. In comparison to PVME bulkgels the phase-transition temperature of the synthesized PVME gel beads is a little decreased.     

Synthesis of perfluorinated cation exchange membranes by preirradiation grafting of acrylic acid onto ethylene-tetrafluoroethylene films

Hydrophilic carboxyl-containing fluoromembranes were obtained by preirradiation grafting of acrylic acid onto ethylene-tetrafluoroethylene film. The dependence of the grafting reaction on temperature, monomer concentration, nature and concentration of inhibitor, crosslinking agent, solvent, and on the preirradiation dose was investigated. The grafting rates increase with temperature, whereas the saturation degree of grafting (SDG) decreases. Addition of inhibitor minimizes homopolymerization and at the same time hinders the grafting reaction. The SDG increases markedly with monomer concentration until it reaches a maximum and thereafter decreases. The grafting rates increase with preirradiation dose. Addition of crosslinking agent initially decreases the SDG, and thereafter increases. The highest grafting rates are obtained using water as solvent followed by methanol and ethanol. The results are discussed on the basis of various parameters: interaction between monomer diffusibility and the viscosity of the monomer bath, the mutual reactivity of monomer, and the crosslinking agent. An agreement is observed between the values of the electrical resistance and the saturation degree of grafting. © 1996 John Wiley & Sons, Inc.     

Heck reaction with an acyl synthon: new coupling reaction between α-halo vinyl ether and alkene

α-Halo vinyl ethers were successfully applied to palladium-catalyzed Heck reaction. Reactions of α-halo vinyl ether with alkenes under various Heck conditions form a new carbon-carbon bond along with a vinyl ether functionality, which can be further manipulated. This is the first synthetic methodology for the coupling of an acyl synthon with alkene employing Heck reaction.     

Synthesis,UV-curing behavior and surface properties of fluorine-containing vinyl ether polymers

Five fluorine-containing vinyl ether monomers were prepared by the reaction between 2-vinyloxy ethanol, a fluorinated alcohol and hexafluorobenzene in the presence of sodium hydride in dimethylformamide. Two representative properties of these monomers, UV-curing behavior initiated by a cationic photo-initiator PAG 201 and surface free energy of coating films, were investigated. Photo-polymerization proceeded both rapidly and completely with a high double-bond conversion （〉 90%） and a fast curing rate （maximum curing time 〈 21 s） for three monomers. The surface energies of the monomers and the resulting polymer films were then investigated. The minimum surface free energy of the UV-cured homopolymer films reaches 7.1 mJ/m2. X-ray photoelectron spectroscopy data show that the low surthce tension is influenced by fluorine content in the soft segments and fluorinated chains＇ migration to the surface. The five monomers exhibit low viscosity, low surface energy, good thermal stability and good photo-polymerization properties, which make them great candidates for UV coating and photoresist applications.     

Role of grafting in the emulsion polymerization of vinyl acetate with poly(vinyl alcohol) as an emulsifier. I. Effect of the degree of blockiness on the kinetics and mechanism of grafting

The role of grafting in particle nucleation during the emulsion polymerization of vinyl acetate with partially hydrolyzed poly(vinyl alcohol) (PVA) as an emulsifier and potassium persulfate as an initiator was investigated. The polymerizations were carried out in batch with a low solids (10%) recipe. An automated reaction calorimeter (Mettler RC1) was used for the direct monitoring of the kinetics of emulsion polymerizations with three medium molecular weight PVAs differing in their degrees of blockiness (Poval 217EE > 217E > 217). Smith–Ewart case 1 kinetics (average number of free radicals per particle < 0.5) were followed in all cases, and no constant rate in interval II was observed. Contrary to what was expected, a nonlinear relationship was observed between the rate of polymerization (R_p) and the number of particles (N_p). At R_{p max,} N_p (217E) > N_p (217EE) > N_p (217), and the final N_p was independent of the degree of blockiness of PVA. The particle size distributions were broad (particle diameter = 20–100 nm) and bimodal. On the basis of these data, we concluded that particle nucleation was continuous and was accompanied by extensive limited aggregation during the particle growth stages. The evolution of the amounts of grafted PVA and poly(vinyl acetate) (PVAc) were determined in polymerizations employing the two PVAs differing the most in blockiness (Poval 217EE and 217). The grafted PVAc followed similar profiles, increasing with conversion, particularly near the end of the two reactions. The amounts of grafted PVAc were about the same in the final latexes (37–39%). In contrast, the grafting of PVA was nearly complete by the time monomer droplets had disappeared in each reaction (25% conversion). However, the extent of grafting differed significantly, with the blockier PVA having about one‐third the grafting of the more random PVA (～10% vs ～30%). In these low solids recipes, grafting appeared to be primarily a solution event, occurring predominantly in the aqueous phase and not at the particle/water interface, as was previously speculated. The PVAc grafts grew until the molecules became water‐insoluble and precipitated, forming polymer particles. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3633–3654, 2001     

Living carbocationic polymerization of isobutyl vinyl ether and the synthesis of poly[isobutylene-b-(isobutyl vinyl ether)]

The MeCH(O-i-Bu)Cl/TiCl₄/MeCONMe₂ initiating system was found to induce the rapid living carbocationic polymerization (LC^⊕Pzn) of isobutyl vinyl ether (IBuVE) at ?100°C. Degradation by dealcoholation which usually accompanies the polymerization of alkyl vinyl ethers by strong Lewis acids is “frozen out” at this low temperature and poly(isobutyl vinyl ether)s (PIBuVEs) with theoretical molecular weights up to ca. 40,000 g/mol (calculated from the initiator/monomer input) and narrow molecular weight distributions (M?_w/M?_n ≤ 1.2) are readily obtained. According to ¹³C-NMR spectroscopy, PIBuVEs prepared by living polymerization at ?100°C are not stereoregular. The MeCH(O-i-Bu)Cl/TiCl₄ combination induces the rapid LC^⊕Pzn of IBuVE even in the absence of N,N-dimethylacetamide (DMA). The addition of the common ion salt, n-Bu₄NCl to the latter system retards the polymerization and meaningful kinetic information can be obtained. The kinetic findings have been explained in terms of TiCl₄. IBuVE and TiCl₄ · IBuVE and TiCl₄ · PIBuVE complexes. The HCl (formal initiator)/TiCl₄/DMA combination is the first initiating system that can be regarded to induce the LC^⊕Pzn of both isobutylene (IB) and IBuVE. Polyisobutylene (PIB)–PIBuVE diblocks were prepared by sequential monomer addition in “one pot” by the 2-chloro-2,4,4-trimethylpentane (TMP-Cl)/TiCl₄/DMA initiating system. Crossover efficiencies are, however, below 35% because the PIB^⊕ + IBuVE → PIB-b-PIBuVE^⊕ crossover is slow. © 1993 John Wiley & Sons, Inc.     

Synthesis of ABA‐triblock and star‐diblock copolymers with poly(2‐adamantyl vinyl ether) and poly(n‐butyl vinyl ether) segments: New thermoplastic elastomers composed solely of poly(vinyl ether) backbones

ABA‐type triblock copolymers and AB‐type star diblock copolymers with poly(2‐adamantyl vinyl ether) [poly(2‐AdVE)] hard outer segments and poly(n‐butyl vinyl ether) [poly(NBVE)] soft inner segments were synthesized by sequential living cationic copolymerization. Although both the two polymer segments were composed solely of poly(vinyl ether) backbones and hydrocarbon side chains, they were segregated into microphase‐separated structure, so that the block copolymers formed thermoplastic elastomers. Both the ABA‐type triblock copolymers and the AB‐type star diblock copolymers exhibited rubber elasticity over wide temperature range. For example, the ABA‐type triblock copolymers showed rubber elasticity from about ?53 °C to about 165 °C and the AB‐type star diblock copolymer did from about ?47 °C to 183 °C with a similar composition of poly(2‐AdVE) and poly(NBVE) segments in the dynamic mechanical analysis. The AB‐type star diblock copolymers exhibited higher tensile strength and elongation at break than the ABA‐type triblock copolymers. The thermal decomposition temperatures of both the block copolymers were as high as 321–331 °C, indicating their high thermal stability. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Mechanistic study on radiation-induced grafting into fluorinated polymer solid films using a swelling-induced detachment of grafted polymers

The radiation-induced graft polymerization (RGP) of styrene into poly(ethylene-co-tetrafluoroethylene) films was performed at various monomer concentrations and solvents at 60 °C. The grafted polystyrene (g-PS) was isolated using the swelling-induced detachment phenomenon, and the number-averaged molecular weight (Mn) and the number of g-PS (Np) were determined using gel permeation chromatography. The Mn increased consistently with an increase in the grafting time up to 2–3 hours, indicating very low termination rates, which was a result of the “gel effect”. This is the first direct evidence of the gradual Mn increase over time using RGP in thermally and chemically stable polymer films such as fluorinated polymers. When the Mn and Np were plotted as a function of the degree of grafting (DOG), sudden Np drops along with rapid Mn increases were observed in the DOG region of 80–90%, indicating negligible initiation and propagation; however, a recombination termination between two propagating g-PS radicals dominated the later part of the grafting process. Further increases in both Mn and Np were observed subsequently, implying that reinitiation and propagation events were triggered by morphological changes, as observed by small- and ultrasmall-angle X-ray scattering experiments, which liberated the dormant radicals from the lamellar crystals.