Polymer In Tetrahydrofuran Research Articles

Pervaporation of benzene/cyclohexane mixtures through supramolecule containing poly(vinyl acetal) membranes

Poly(vinyl acetal) PVAc was synthesized by the acid-catalyzed acetalisation of poly(vinyl alcohol). Three different morphologically modified variants of the polymer were prepared by the addition of supramolecules; namely α and β cyclodextrins (CD) and butyl calixerene (calix) to the PVAc sol. 20% (w/v) of the solution of the polymers in tetrahydrofuran (THF) was used to cast the membranes. These membranes were characterized using spectroscopic and thermoanalytical techniques, and also tested for their chemical resistance and mechanical strength. The pervaporative behaviour of modified membranes vis-à-vis PVAc for the separation of a wide composition of benzene (Bz)/cyclohexane (Chx) mixtures was evaluated. Addition of αCD or calix to PVAc reduced the overall flux while dispersion of βCD favoured an enhanced flux especially in the Bz-lean and azeotropic region.

Synthesis and Characterization of Polymer Networks and Star Polymers Containing a Novel, Hydrolyzable Acetal-Based Dimethacrylate Cross-Linker

An acid-labile dimethacrylate acetal cross-linker, di(methacryloyloxy-1-ethoxy)methane (DMOEM), was synthesized by the reaction of 2-hydroxyethyl methacrylate and paraformaldehyde using p-toluenesulfonic acid and toluene as catalyst and solvent, respectively. Group transfer polymerization was employed to use this cross-linker in the preparation of nine hydrolyzable polymer structures: one neat cross-linker network, one randomly cross-linked network of methyl methacrylate (MMA), and seven star-shaped polymers of MMA. Gel permeation chromatography (GPC) in tetrahydrofuran (THF) confirmed the narrow molecular weight distributions of the linear polymer precursors to the stars and demonstrated the increase in molecular weight upon the addition of cross-linker for the formation of star-shaped polymers. Characterization of the star polymers in THF using static light scattering and GPC showed that the molecular weights and the number of arms of each star polymer increased with an increase in the molar ratio of cross-linker to initiator and with a decrease in the molar ratio of monomer to initiator. The star polymers with DMOEM cores bore a smaller number of arms than those cross-linked with the non-hydrolyzable commercial cross-linker ethylene glycol dimethacrylate due to the bulkier structure of DMOEM. All DMOEM-containing polymer networks and star polymers were completely hydrolyzed within 48 h using hydrochloric acid in THF.

Organic Crystal Rings Formed in Template Polymer Pores by Evaporation of Solvent

AbstractSummary: The fabrication of organic crystals into useful forms might play an important role in future electronics technology. A method for fabricating organic crystal rings has been developed. The self‐assembly of six‐armed poly(methyl methacrylate) with a triphenylene core leads to the formation of pores homogeneously distributed in the polymer film. Because the solubility of this polymer in tetrahydrofuran (THF) is lower than that of 2,3,6,7,10,11‐hexamethacrylate triphenylene (HMTP), the holes initially formed and distributed in the polymer film are filled with a THF solution of HMTP. Crystallization nucleation occurs at the edge of holes and HMPT crystals grow at the contact line to form organic crystal rings.Schematic illustration of crystal‐ring formation.imageSchematic illustration of crystal‐ring formation.

Synthesis and optical properties of novel blue‐light‐emitting poly(p‐phenylene vinylene) derivatives with pendant oxadiazole or cyano groups

AbstractTwo novel poly(p‐phenylene vinylene) polymers, which carried side substituents with cyano groups or 1,3,4‐oxadiazole, were synthesized by Heck coupling. They consisted of alternating conjugated segments and nonconjugated aliphatic spacers. The polymers had moderate molecular weights, were amorphous, and dissolved readily in tetrahydrofuran and halogenated organic solvents. They were stable up to approximately 340 °C in N2 and 290 °C in air, and the anaerobic char yield was around 60% at 800 °C. The polymer with cyano side groups emitted blue light in solutions and thin films with identical photoluminescence (PL) maximum at 450 nm; this supported the idea that chain interactions were hindered even in the solid state. The PL maximum of this polymer in thin films was blueshifted upon annealing at 120 °C, indicating a thermochromic effect as a result of conformational changes in the polymer backbone. The polymer containing side substituents with oxadiazole rings emitted blue light in solutions with a PL maximum at 474 nm and blue‐greenish light in thin films with a PL maximum at 511 nm. The PL quantum yields of the polymers in tetrahydrofuran were 0.13–0.24. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1768–1778, 2004

Effect of Metal Oxides on Thermal Degradation of Poly(vinyl acetate) and Poly(vinyl chloride) and Their Blends

The role of metal oxides on the thermal decomposition of poly(vinyl chloride) (PVC) and poly(vinyl acetate) (PVAC) and their blends was investigated by thermogravimetry (TGA). While the degradation of PVAC was mildly affected by the presence of metal oxides, the degradation of PVC was greatly influenced by metal oxides. Both polymers followed a two-step degradation mechanism involving chlorine or acetate radical removal followed by polyolefinic backbone breakage. The isokinetic temperatures and rate determined from the compensation plots indicated that the mode of olefinic backbone breakage is the same for both the polymers. FTIR studies after the first stage showed the disappearance of the C-Cl of PVC and C=O and C-O groups of PVAC, suggesting the formation of a polyolefinic chain. Blends of PVC-PVAC were obtained by solution blending by dissolving the polymers in tetrahydrofuran. Scanning electron microscopy and TGA showed complete miscibility of polymers in the blend. The first-stage degradation of the blend was greatly influenced by the presence of PVC and metal oxides, suggesting that hydrogen chloride liberated from PVC influenced the decomposition behavior of PVAC. The second-stage degradation (olefinic breakage) of the blends was mildly affected by the metal oxides and the breakage was similar to that of pure polymers.

Polymerization of pyrrole and processing of the resulting polypyrrole as blends with plasticised PVC

AbstractPolypyrrole was synthesized by chemical oxidation of pyrrole in water containing various sulphonic acids like toluene sulphonic acid (TSA), sulphosalicylic acid (SSA), and camphor sulphonic acid (CSA), as well as a combination of each sulphonic acid with sodium dodecyl benzene sulphonate (NaDBS) to investigate the effect of doping on conductivity, yield, and processability of the conducting polymer. Free‐standing blend films of polypyrrole and plasticized polyvinyl chloride (PVC) were obtained by casting an homogeneous suspension of the two polymers in tetrahydrofuran. The maximum conductivity of the blend film is ∼ 0.3 S/cm, corresponding to a weight fraction of 0.16 w/w polypyrrole. The blend film is semiconducting in the range 300–10 K. A TG‐DTA scan indicates the blend film to be amorphous with a stepwise decomposition process similar to pristine PVC. The choice of a dual dopant system during synthesis and the plasticised polymer during subsequent processing were keys to obtaining homogeneous high‐quality films. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1544–1548, 2001

Determination of Molecular Weight of PDPS Modified Copolymers

AbstractMolecular weight (MW) determinations of polydiphenylsiloxane‐co‐polydimethylsiloxane (PDPS/PDMS), polydiphenylsiloxane‐co‐polymethylphenylsiloxane (PDPS/PMPS) and polydiphenylsiloxane‐co‐polymethyl(3,3,3‐trifluoropropyl)siloxane (PDPS/PMFPS) statistical copolymers by gel permeation chromatography (GPC), GPC coupled differential viscometer (GPC‐DV) and light scattering (LS) techniques have been compared and discussed. The MW obtained by GPC‐DV in the PDPS/PDMS and the PDPS/PMPS series agreed with that obtained by LS very well. In PDPS/PDMS copolymers, it was found that the MW obtained by GPC was much lower than that obtained by GPC‐DV and LS, as Ph2SiO) content is higher than 50 mol%. In PDPS/PMFPS copolymers, the MW obtained by GPC was far different from that obtained by GPC‐DV and the deviation decreased with increasing Ph2SiO) mol%. The α values of the copolymers can be explained by the structure of the polymer in tetrahydrofuran (THF). Based on the relatively soluble copolymers, not only the differential refractive index increments (dn/dc) of PMPS, PDMS and PMFPS homopolymers but also that of the PDPS homopolymer in THF could be calculated by their corresponding copolymers.

Development and application of latent hydrosilylation catalysts [2]—Control of catalytic activity of platinum catalyst by polystyrene derivatives having propargyl moieties

A new thermal latent hydrosilylation catalyst on the basis of H2PtCl6 and polystyrene derivatives having propargyl moieties is described. The polystyrene derivatives having various propargyl moieties were obtained by the reaction of propargyl alcohols with poly(p-chloromethylstyrene) or its copolymer with styrene. The polymer-supported platinum catalysts were prepared by aging H2PtCl6 with these polymers in tetrahydrofuran at 30 °C for 12 h. In the presence of the polymers, the hydrosilylation activity of H2PtCl6 was found to be controlled thermally in the model reaction of trimethylsilane and triethylvinylsilane. Effective control of the crosslinking reaction of silicone resin was also achieved by using these latent catalyst systems. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 35–42, 2000

Polymerization of Methacrylic Esters Using Metal Alkoxides Containing Lanthanoids

Polymerization of methyl methacrylate (MMA) was promoted by the clusters of lithium isopropoxide containing lanthanoid(III) isopropoxides [La(O i-Pr)3 (1) and Ce(O i-Pr)3 (2)], prepared from the corresponding lanthanoid(III) chlorides according to the Kagan’s method. The initiators provided an isotactic poly(MMA) in a good yield, although lithium isopropoxide afforded no polymer in toluene at 0°C. While lithium isopropoxide also gave no polymer in tetrahydrofuran at 0°C, syndiotactic poly(MMA) was obtained even at −40°C using the cerium triisopropoxide (2) in 91% yield. The polymerization was confirmed to be initiated through Meerwein–Ponndorf–Verley (MPV) reduction.

Photocrosslinking of azidated poly(vinyl chloride) coated onto plasticized PVC surface: Route to containing plasticizer migration

AbstractThe migration of phthalate esters which are commonly employed for plasticizing poly(vinyl chloride) (PVC) is a significant problem in PVC‐based medical devices as well as in packaging used for food stuffs and pharmaceuticals. Medical‐grade PVC resin was treated with sodium azide in dimethylformamide (DMF) to prepare the azide polymer. The polymeric azide was coated onto the surface of plasticized PVC sheets by dipping in a solution of the polymer in tetrahydrofuran (THF). Crosslinking of the azide polymer was accomplished by irradiating the surface using a 125 W UV lamp for various lengths of time. Migration of the plasticizer di 2‐(ethylhexyl phthalate) (DEHP) from coated and uncoated samples was examined in n‐hexane at 30°C. It was found that 50–80% reduction in migration of DEHP could be effected from plasticized PVC in comparison with the controls in 72 h by this technique depending on the concentration of the coating solution, coating thickness, azide concentration, and irradiation dose. © 1995 John Wiley & Sons, Inc.

Syntheses and kinetics of piperazine-modified poly(vinyl chloride)s for use as fixed-site proton carrier membranes

Analytical-grade piperazine was dissolved in methanol and reacted with commercial-grade poly(vinyl chloride) powders over a range of temperatures from 25 to 64°C and times from 0.17 to 49 days. The products were aminated polymers that also contained conjugated double bonds. Chemical analysis of the resulting powders showed that up to 1.6 wt% N was possible in this solid-liquid heterogeneous reaction, although insolubility of the aminated polymer in tetrahydrofuran was always realized by 0.8 wt% N content. In those polymer formulations that were soluble, membranes were cast from solution using o-nitrophenyloctyl ether and potassium tetrakis(p-chlorophenyl)borate as the plasticizer and negatively charged sites, respectively. After conditioning, many of these fixed-site proton carrier membranes showed Nernstian pH sensitivity in potentiometric cells, independent of synthesis parameters. The nitrogen content of the aminated PVC and the pH sensitivity of the membrane correlated below a limiting nitrogen content, where Nernstian behaviour was generally observed over a range from 0.4 to 0.8 wt% N content. A three-dimensional plot over the soluble region of the polymer predicted the overall dependence of the reaction parameters, from which an activation energy (17 kcal mol−1) was determined for the substitution process. A time-temperature correspondence was demonstrated that allowed the construction of a master curve of amination in which the shift factor was of the same form as either the Williams-Landel-Ferry equation or a rearranged Doolittle equation. This format was extended to three dimensions, where the pH sensitivity is shown as a function of both the weight percentage N content and the shift factor.

Photon harvesting vinylphenanthrene-methacrylic acid polymers: singlet-state migration and trapping

Random and alternating copolymers of 9-vinylphenanthrene and methacrylic acid have been prepared. These polymers have been doped with low mole fractions of anthryl energy traps. The photophysics of these polymers with and without these traps have been studied as a function of phenathryl content in tetrahydrofuran (THF) and water. The fluorescence properties of the alternating polymers indicate an absence of excimer-forming sites in THF but not in water. Significant singlet energy migration has been implicated by fluorescence quenching methods. The quantum efficiency of anthracene sensitization has been found to be ca. 0.4 for the alternating polymer in THF and water. There is a very strong dependence of the photophysical properties of the random copolymers on pH, which is reflected in the energy-transfer efficiency.

Reaction rate of crosslinkings by using metallated polymer. I. Grafting and intramolecular crosslinkings at the first stage

AbstractLithium‐metallated styrene–p‐benzylstyrene copolymer was reacted with chlorine‐terminated polystyrene as a crosslinker polymer in tetrahydrofuran (THF) at 25°C. The rate constant was estimated from the changes in the concentration of metallated polymer by using photometrical measurements. The various reaction conditions were chosen and it became clear that the rate constants of grafting (k1) and intramolecular crosslinkings (k2intra) were gotten separately at the first stage. As a result, k2intra showed larger values than k1 and decreased with increasing degree of polymerization of crosslinker polymers.

Rheology of polyphosphazene melts and solutions—some surprises

AbstractRheological tests are reported for two types of polyorganophosphazenes, one being a fluorinated alkoxy terpolymer (PNFT) and the other an aryloxy copolymer (PAP). Non‐Newtonian viscosity η(\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document}) and complex viscosity components η′(ω) and η″(ω) were measured as functions of shear rate \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document} and oscillatory frequency ω, using a Weissenberg rheogoniometer, and a limited amount of normal stress data was also obtained. Solutions of both polymers in tetrahydrofuran were tested, over a concentration range 0‐22 percent for PNFT and 0‐35 percent for PAP. Melts of PNFT were examined for temperatures 50‐178°C, and melts of PAP at 210°C even though they were not truly fluid at this temperature. Solution and melt data are shown to obey conventional superposition principles to give master curves. For solutions, superposition is achieved by using the Bueche relaxation time as a concentration reducing factor with no adjustable parameters, and the Spriggs model also proves useful in predicting normal stress and shear stress results. For PNFT melts, master curves are fitted by the new WS2H2 model which incorporates detailed molecular weight distribution (MWD) information and extracts the entanglement length Me from the data. Temperature shift factors aT show Arrhenius behavior and the corresponding activation energies Ere are reported. Results for PNFT melts were complicated by lack of agreement between two samples of nominally the same composition; η′(ω) shapes and levels and Ere values differed widely. This is interpreted in terms of detailed MWD information and the possibility of mesomorphic phase transitions occurring in these nominally amorphous materials.

Partial Alkali Metalation of Poly(p-hydroxystyrene) and Poly(p-hydroxystyrene-co-styrene) and the Solubility of the Resulting Polymer in Tetrahydrofuran

The partial alkali metalation of poly(p-hydroxystyrene) (PHS) and poly(p-hydroxystyrene-co-styrene) P(HS-co-S) with alkali metal naphthalene (M-Naph) was carried out to obtain a solution of the metalated polymer. The value for {[OM]/[OH]0}tur was determined as the ratio of pendant metal phenolates (OM; M=Li, Na, and K) to the initial pendant phenols when the titration of a PHS or P(HS-co-S) solution with M-Naph begins to give a turbid solution and/or a polymer precipitation. The value of {[OM]/[OH]0}tur was found to depend on the counter cation (M+); i.e., the solubility of partially-metalated P(HS-co-S) was in the order OK≍ONaO}tur vs. the concentration of P(HS-co-S) was linear and “intrinsic” {[ONa]/[OH]O}tur was found to be 0.70. These results can be interpreted in terms of solubility parameter. The polymer which was once precipitated at a high [OM]/[OH]O ratio became soluble again by hydrolysis with acid or by dilution with a THF solution of PHS or P(HS-co-S).

Stability of “live” polymers in tetrahydrofuran in the presence of α-methylstyrene

IR spectroscopy was used to investigate the stability of “live” polymers (disodium tetramer of α-methylstyrene) at 20° in pure tetrahydrofuran and in the presence of α-methylstyrene. Rate constants were determined of the disappearance of absorption bands at 1585, 1000, 1330 and 965 cm −1, characterizing the main structure of the live polymer. It was found that the decomposition of live polymers slows down suddenly in the presence of α-methylstyrene in low concentrations ( m 0 ⩽ 0·7 mole/dm 3). Results were examined assuming the formation of donor-acceptor complexes of monomer with an α-methylstyrene disodium tetramer, these complexes being more stable than the initial live polymer.

Heterotactic Polymers of α-Substituted Acrylic Acid Esters

Polymerizations of various methacrylates and α-(p-substituted phenyl)acrylates were studied in toluene and tetrahydrofuran by several anionic initiators. The polymerization with octylpotassium in tetrahydrofuran was found to be the most suitable for the formation of the heterotactic polymer, defined as the polymer containing more than 50% heterotactic triads. Methacrylic acid esters of the primary alcohol gave the heterotactic polymers, whose heterotactic contents increased with an increase in the bulkiness of the ester group. Methacrylic esters of secondary alcohol generally gave heterotactic polymers with octylpotassium in tetrahydrofuran. In the polymerizations of methacrylic acid esters of tertiary alcohol, the heterotactic contents decreased with an increase in the bulkiness of the ester group. A perfectly atactic polymer was obtained in the polymerization of methyl α-phenylacrylate with butyllithium in tetrahydrofuran, but it gave the heterotactic polymer when initiated with octylpotassium in tetrahydrofuran. Methyl α-p-chlorophenylacrylate produced the heterotactic polymer in tetrahydrofuran with butyllithium as well as with octylpotassium. In the case of methyl α-p-bromophenylacrylate, the heterotactic polymer was obtained even in the polymerization in toluene with butyllithium. These results indicate that the acrylic acid ester having the bulkier substituent tends to give the heterotactic polymer more easily by anionic initiator.

The preparation and properties of BAB block copolymers based on polyethylene sulphide and polyisoprene

Block copolymers of ethylene sulphide (B) and isoprene (A) have been prepared by anionic synthesis using alkali metal complexes of naphthalene as initiator. Two series of block copolymers have been synthesized, one (based on sodium naphthalenide as initiator) having high molecular weights and the other (based on lithium naphthalenide) having low molecular weights. Physical properties of the block copolymers as a function of composition, molecular weight and polyisoprene microstructure have been studied. Polymers containing high molecular weight polyethylene sulphide sequences were difficult to process without degradation. By lowering the molecular weight of the polyethylene sulphide segment, block copolymers of improved processibility were obtained. The centre block polyisoprene microstructure has been varied from 100% 1,2/3,4 configuration to 80% 1,4 configuration by preparing a “seed” polymer in tetrahydrofuran followed by solvent removal and replacement by hexane. Changes in microstructure affect low temperature flexibility, resilience and tensile strength of the block copolymer. The BAB block copolymers are biphasic and exhibit elastomeric properties with improved network stability compared with polystyrene-polybutadiene-polystyrene ABA block copolymers.

Measurement of molecular weight of poly(vinyl chloride)

AbstractMolecular weights of six bulk‐process and five suspension‐process PVC samples have been measured as part of a study aimed at developing a technique for gel permeation‐chromatographic analysis of this polymer in tetrahydrofuran at room temperature. Osmometric M̄n values measured in cyclohexanone appear to be valid; the results are insensitive to thermal history or ultrasonic irradiation of the solution. Corresponding measurements in tetrahydrofuran changed with measurement temperature and indicated the presence of stable supermolecular PVC aggregates in this solvent. Such aggregates can be dispersed by ultrasonic treatment of the solution for brief periods. Simultaneous degradation of PVC molecules appears to be prevented by addition of small concentrations of nonionic surfactant to the tetrahydrofuran solutions. Treated solutions are suitable for GPC analyses at ambient temperatures. The results of osmometry, light scattering, and GPC agreed well.

Polymerization of α‐methylstyrene by living polymer in tetrahydrofuran

AbstractKinetics of polymerization of α‐methylstyrene by poly‐α‐methylstyrylsodium (a “living” polymer) has been studied in tetrahydrofuran at −78°C. Complex dependences were established: that of the conversion X on reduced time φ and that of the apparent rate constant for the polymer chain propagation on conversion X and on the concentration of living polymers and monomer. The experimental data obtained were explained by assuming a coordination mechanism of anionic polymerization including the following elementary reaction: (a) generation of active polymerization centers (K1) by interaction of the living polymer with the monomer; (b) propagation of the polymer chains (K2); (c) monomolecular (K31) and bimolecular (K32) reactions of isomerization of active centers resulting in the formation of high molecular weight living polymers capable of again becoming active centers of polymerization. Approximate derivation of kinetic equation was carried out and the constants of elementary reactions were determined (K1 = 0.15, K2 = 24, K32 = 14.1./mole‐min and K31 = 0.05 min−1). The coincidence of the expected dependencies X = F(τ; φ) Kp = F(X; n0−1/2); dx/dτ = F(n0) with the experimental ones was followed with the aid of computers. The expected change in the values of X and Kp depending on the contribution of each elementary reaction to the overall polymerization process was analyzed.