Poly Vinyl Methyl Ether Research Articles

Cytotoxicity, calcium release, and pH changes generated by novel calcium phosphate cement formulations

Few published studies describe the biological properties of calcium phosphate cements (CPCs) for dental applications. We measured several biologically relevant properties of 3 CPCs over an extended (8 wk) interval. Monocalcium phosphate, calcium oxide, and synthetic hydroxyapatite were combined with either modified polyacrylic acid, light-activated modified polyalkenoic acid, or 35% w/w polymethyl vinyl ether maleic acid to obtain Types I, II, and III CPCs, respectively. Set cements were placed in direct contact with L929 fibroblasts for up to 8 weeks. Media Ca(+2) and pH were determined by atomic absorption spectroscopy and pH electrode respectively. Cell mitochondrial function was measured by MTT assay. Type I cements suppressed mitochondrial activity > 90% (vs. Teflon controls), but significantly (p < 0.05) improved to control levels over 8 weeks. Type II cements suppressed mitochondrial activity > 90% at all times. Type III cements elevated mitochondrial activity significantly after 7 wks. The pH profiles approached neutrality by 24 h, and all cements released calcium into the storage medium at all periods (24 h - 8 wk). We concluded that several types of cements had long-term biological profiles that show promise for dental applications.

Reverse Osmosis Membrane Treatment Improves Salt-Rejection Performance

This study systematically investigated applying rejection-enhancing agents (REAs) that can plug or seal defects on flat-sheet polyamide (PA) membrane surfaces to improve salt rejection with minimum flux reduction. Polyvinyl methyl ether (PVME) and tannic acid (TA) were used as REAs on low-pressure reverse osmosis (LPRO) membranes. Treatment of an unused LPRO membrane (membrane A) with REAs in the range of 10–30 ppm PVME followed by 10–30 ppm TA significantly improved membrane salt-rejection performance with a concomitant flux reduction less than 20 percent. However, similar treatment of another new membrane (membrane B1), which exhibited good initial salt-rejection performance, did not produce any further improvements. A used membrane B2 was also treated with PVME and TA and showed significant salt-rejection improvement with modest flux reduction. In addition, when the initial salt rejection of a sample from this membrane was relatively small, possibly due to severe degradation, the coating application resulted in significant salt-rejection improvement. Successful testing with injecting REAs online, without interrupting pilot plant operation, suggests that the process is attractive for practical applications. Recommendations are provided for implementing the process in RO desalination plants.

Thermal Response of Surface Grafted Two-Dimensional Polystyrene (PS)/Polyvinylmethylether (PVME) Blend Films

This work shows that phase separations in 2D polymer films can be tuned by employing entropically constraining grafting points. We present experimental results on surface-grafted 2D polystyrene (PS)/polyvinylmethylether (PVME) blended films using surface-anchored benzophenone derivates. In contrast with 2D films that have not been grafted, it was possible to raise the blended lower critical solution temperature (LCST) above room temperature by using low grafting point densities. Highly constrained films did not show polymer−polymer phase separation. In addition to the in situ structural analysis performed with surface probe microscopy (SPM), μ-beam-sized grazing incidence small-angle X-ray scattering (μ-GISAXS), and μ-X-ray reflectivity (μ-XRR), surface stress investigations performed using nanomechanical cantilever sensor (NCS) arrays gave detailed insight into the phase separation mechanism. Phase separations were shown to result in dominating attractive entropic spring mechanisms with opposing repulsiv...

Comparative study of biocompatibility of newly developed calcium phosphate‐based root canal sealers on fibroblasts derived from primary human gingiva and a mouse L929 cell line

To determine biocompatibility of three calcium phosphate cement (CPC) sealers, and to compare the cytotoxic response of human gingival fibroblasts (HGF) and one mouse fibroblast cell line (L929) to these materials. Monocalcium phosphate, calcium oxide and synthetic hydroxyapatite were combined with one of three aqueous solutions: modified polyacrylic acid, glass-ionomer liquid or 35% w/w polymethyl vinyl ether maleic acid to obtain Types I, IIa and III CPCs, respectively. Commercial Ca(OH)(2) sealer was used as a control. The materials were packed into Teflon molds (5.5 x 3 mm), and cellular function was assessed using MTT assay. The specimens were placed immediately in contact with cells, then evaluated at (24 h, 1 week, 2 week, 3 week, 4 week, 5 week). All materials showed significant cytotoxicity for both L929 and HGF cells at 24 h except for Type III. Type I was severely toxic initially, but improved significantly (P < 0.05) over the 5 week evaluation. Types II and Ca(OH)(2) were both cytotoxic over the 5 weeks. Type III CPC was equivalent to Teflon the entire time. The results showed the same rank of cytotoxicity in both cultures. The cytotoxic response decreased in the order of Type II > Ca(OH)(2) > Type I > Type III overtime. L929 cells were generally more sensitive than HGF cells to the calcium hydroxide-based sealer (Acroseal). Types I and III have acceptable biologic properties for endodontic applications.

Role of polymer–clay interactions and nano-clay dispersion on the viscoelastic response of supercritical CO2 dispersed polyvinylmethylether (PVME)–Clay nanocomposites

Clay dispersion and polymer–clay interactions play a key role in producing property enhancements in nanocomposites; yet characterizing them in complex polymer–clay systems is often a challenge. Rheology can offer insights into clay dispersion and clay–polymer interactions. We have investigated the viscoelastic response for a series of supercritical CO 2 (scCO 2 ) processed polyvinylmethylether (PVME)/clay nanocomposites with varying polymer–clay interactions and nano-clay dispersion. PVME is used in this study because it is highly swellable in scCO 2 , thereby enabling processing of PVME/clay mixtures without the presence of a co-solvent. Since PVME and natural clay are water-soluble, highly dispersed PVME-clay nanocomposites were prepared using water, followed by lyophilization in the presence of polymer. In this ‘weakly interacting’, but highly dispersed systems, with clay loadings above the percolation threshold, terminal behavior was observed in the linear viscoelastic moduli (i.e. no low frequency plateau is observed). When the nanocomposites were processed in scCO 2 , with 15 wt% of 30B and I.30P, the WAXD patterns of the resultant nanocomposites were largely comparable, indicating partial dispersion, with intercalation peaks. However, the rheology of these two nanocomposites were significantly different despite similar inorganic volume loading (4 vol%). Even with less dispersion compared to the water-based system, the low-frequency moduli were significantly more enhanced, accompanied by a plateau, and a cross-over frequency shift. Neglecting the small differences in the actual clay content between these clays (4–5 vol% of inorganic matter), this suggests that rheology may be sensitive to strong interactions between the clay surfactant and the polymer. Therefore, polymer–clay interactions and clay–clay interactions may both be important in the ability to sustain a “so-called” percolated network, rather than just clay dispersion.

Picosecond time-resolved fluorescence study of poly vinyl methyl ether aqueous solution

Picosecond time-resolved fluorescence spectroscopy was carried out for the aqueous solution of poly vinyl methyl ether (PVME) at two different temperatures by using a fluorescent probe molecule. The dehydration of coiled PVME, which is the initial process of coil-to-globule phase transition, was observed below the low critical solution temperature (LCST), whereas two hydrophobic environments were found inside and outside PVME fine particles above LCST.

X‐ray photoelectron and carbon Kα emission measurements and calculations of O‐, CO‐, N‐, and S‐containing substances

AbstractX‐ray fluorescence measurements for O‐containing [polyethylene oxide, polyvinyl alcohol, polyvinyl methyl ether], CO‐containing [polyvinyl methyl ketone, polyethylene terephthalate], N‐containing [poly‐4‐vinylpyridine (P4VP), polyaniline oligomer (PAO)], and S‐containing [polyphenylene sulfide] substances are presented. Carbon Kα X‐ray emission spectra (XES) and X‐ray photoelectron spectra (XPS) are compared with our DFT calculations performed with the Amsterdam density functional (ADF) program. The combined analysis of valence XPS and carbon Kα XES allows us to determine the individual contributions from pσ‐ and pπ‐bonding molecular orbitals of the polymers. The ΔSCF calculations yield the accurate C1s core‐electron binding energies (CEBEs) for all carbon sites of the organic compound. We calculate all CEBEs of the model molecules using the ΔEKS approach. Our simulated C1s photoelectron and C Kα emission spectra are in good agreement with our measurements. We also obtain WD (work function and the other energies) values for the polymers and PAO from the difference between calculated (gas‐phase) and measured (solid) CEBE values. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 162–172, 2007

Effect of triclosan/copolymer‐containing toothpaste on the association between plaque and gingival bleeding: a randomized controlled clinical trial

To study longitudinal associations between plaque and gingival bleeding and multilevel variance/covariance structures after introducing triclosan-containing toothpaste. A 10-week, randomized, two-arm, double-masked, controlled clinical trial was conducted in 34 healthy, non-smoking females with plaque-induced gingivitis. Clinical periodontal examinations were repeated every other week. At week 4, test toothpaste containing 0.24% sodium monofluorophosphate, 0.3% triclosan, and 2% polyvinyl-methyl ether maleic acid; or control toothpaste containing 0.76% sodium monofluorophosphate and 0.1% sodium fluoride, were randomly distributed. Multivariate multilevel models indicated that, after introducing experimental toothpastes, subject random error was reduced from 0.6 to below 0.2. The odds ratio (OR) of bleeding on probing (BOP) was about 30% less in the test than in the control group (p<0.01). At the end of the experiment, ORs for BOP and plaque index scores 1-3 (reference 0) were 2.1-2.4 in the control group, but 1.1-1.9 in the test group (p<0.05). No effects on plaque levels and calculus were observed. Multivariate multilevel modelling allows the study of fixed and random effects of experimental toothpastes on gingival inflammation in small sample. Triclosan appears to attenuate the causal association between supragingival plaque and gingival bleeding in gingivitis.

Thermally-Activated Non-Reversible Response of Polystyrene/ Polyvinyl Methyl Ether (PS/PVME) Sandwich Sample Under Small-Amplitude Oscillatory Shear Flow

Small amplitude oscillatory shear modulus was measured for a sandwich type assembly made of polystyrene (PS) and polyvinyl methyl ether (PVME) as a function of time at constant temperature and as a function of temperature at constant frequency. Diffusion coefficient in the miscible region was obtained from the time sweep experiments. The obtained mutual diffusion coefficient was found to be in agreement with the value determined using attenuated total reflection-infrared spectroscopy measurements. A peculiar non-reversible behavior was observed when the sandwich sample was heated and cooled between 40 and 160°C. Such a behavior was associated with the difference in kinetics between phase segregation and phase homogenization of the PS/PVME blend.

The effect of a polyhexamethylene biguanide mouthrinse compared with a triclosan rinse and a chlorhexidine rinse on bacterial counts and 4‐day plaque re‐growth

For various clinical applications, polyhexamethylene biguanide hydrochloride (PHMB) has been used for many years as an antiseptic in medicine. Recently, a 0.04% and a 0.12% PHMB mouthwash were shown to inhibit plaque re-growth and to reduce oral bacterial counts. In this study, a 0.2% PHMB mouthrinse (A) was compared with a positive control 0.12% aqueous chlorhexidine solution (B), a commercially available 0.3% triclosan/2.0% polyvinyl methyl ether maleic acid copolymer mouthrinse (Colgate Total Plax) (C), and a negative control placebo rinse (10% ethanol, flavour) (D). The controlled clinical study was a double blind, randomized, four replicate cross - over design. Plaque re-growth was assessed with the Turesky et al. (1970) modification of the Quigley & Hein (1962) plaque index. The antibacterial effect was assessed by taking bacterial counts on the tooth surface (smears from the buccal surface of 16/26) and mucosa (smears from the buccal mucosa in opposite of area 16/26) after the professional prophylaxis and after the first rinse with the preparations on day 1 and prior to the clinical examination on day 5. Sixteen volunteers participated and, on day 1 of each study period were rendered plaque-free, ceased toothcleaning, and rinsed twice daily with the allocated mouthrinse. On day 5, plaque was scored and smears were collected according to the protocol. A 10-day wash-out period was carried out between each rinse evaluation. Data were analysed using ancova with Bonferroni HSD adjustment for multiple comparisons (colony forming units per sample) with a significance level alpha=0.05. The 0.2% PHMB mouthrinse (A) was significantly better at inhibiting plaque than the placebo (D), but significant less effective than the 0.12% aqueous chlorhexidine solution (B). There is no significant difference between A and the 0.3% triclosan/2.0% copolymer mouthrinse (C). Bacterial count reductions (tooth surface and mucosa) with PHMB (A) were significantly greater compared with the placebo (D) and triclosan (C), but significantly lower compared with chlorhexidine (B) (tooth surface) and equally effective compared with chlorhexidine (B) (mucosa). Consistent with previous studies, a PHMB mouthrinse was shown to inhibit plaque re-growth and to reduce oral bacterial counts, indicating that PHMB could be an alternative to established mouthrinses in preventive applications.

O10 The technology behind Colgate® TotalTM toothpaste

In the early 1990s, a break‐through toothpaste, known as Colgate® Total™, was launched with documented long‐lasting activity against plaque, gingivitis, calculus, tooth decay and bad breath. The technology behind this toothpaste is the combination of triclosan, a polyvinyl methyl ether maleic acid (PVM/MA) copolymer and sodium fluoride (TCF). The function of the copolymer is to ensure optimal oral retention and prolonged release of the antibacterial triclosan. Effective levels of triclosan have been measured in the oral cavity 12 h after brushing the teeth. This allows prolonged control of oral bacteria that can lead to the formation of dental plaque and gingivitis and bad breath. Similarly, the retention of triclosan to oral surfaces during 2 years regular use of the product has led to a significant reduction in incremental coronal caries compared to an ADA‐approved anti‐cavity fluoride toothpaste. Furthermore, significantly less calcium phosphate has been shown to be present in dental plaque after brushing the teeth with the triclosan/copolymer toothpaste, and this has resulted in the reduced formation of tartar. A new variant of the triclosan/copolymer/fluoride toothpaste, having the numerous therapeutic and aesthetic benefits of the original formula, has been made available to consumers. The new dentifrice, which contains an impactful breath freshening flavor, has been documented to be significantly better (P &lt; 0.05) than a control toothpaste in providing sustained control of bad breath over 12 h. After 12 h, breath odor was reduced from 51% compared to the control. The long term retention and subsequent release of triclosan by the copolymer in the TCF formula provide consumers protection against plaque, gingivitis, tartar, caries and bad breath.

Alkyl (C10, C12, C14 and C16) triphenyl phosphonium bromide influenced cloud points of nonionic surfactants (Triton X 100, Brij 56 and Brij 97) and the polymer (Polyvinyl methyl ether)

The clouding points (CP) of the nonionic surfactants p-tert-octyl phenyl polyoxyethylene ether (Triton X 100), Brij-56 and Brij-97, and the water soluble polymer polyvinylmethylether (PVME) have been measured in the presence of the ionic surfactants alkyl (C10, C12, C14 and C16) triphenyl phosphonium bromides (ATPBs). The threshold additive concentrations required for efficient CP enhancement of the systems that were studied have been determined. Considering CP as the threshold state of phase separation, the energetics of the process at different additive concentrations has been evaluated. The spontaneity of free energy of the clouding process (ΔG c 0 ) at the transition concentrations followed the order PVME > TX 100 ≈ Bj 56 > Bj 97. The clouding process has been found to be energetically endothermic with fairly large enthalpy and entropy changes that nicely compensate each other. The compensation temperature has been evaluated and compared with different types of the clouding agents.

Enhanced generation of fast protons from a polymer-coated metal foil by a femtosecond intense laser field

The results of generation of fast protons from 5-μm-thick copper foil targets by 60fs laser irradiation at 1.5×1017W∕cm2 are presented. Both polyvinylmethylether (PVME)-coated and uncoated copper foil targets are examined. Fast protons are measured using a Thomson mass spectrometer and maximum proton energies are 570 and 280keV for the PVME-coated and the uncoated target, respectively. The intensity of fast protons with energy of 160keV from the PVME-coated target is approximately 80-fold higher than that from the uncoated target.

FTIR Imaging of Polymeric Materials under High-Pressure Carbon Dioxide

A novel application of FTIR imaging to study polymers subjected to high-pressure CO2 was demonstrated. FTIR images of polymer blends under high-pressure CO2 were obtained in situ using a single reflection ATR diamond accessory combined with a high-pressure cell. Two systems, a polystyrene (PS)/poly(vinyl methyl ether (PVME) blend and a poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) system, have been studied to demonstrate the feasibility and principles of this new approach. Using this approach, the CO2-induced phase separation of an initially homogeneous PS/PVME blend was observed at a CO2 pressure of 60 bar and temperature of 40 °C. FTIR imaging allowed us to identify formation of distinct domains that are PS- and PVME-rich. The size of these domains was ca. 200 μm. In a second high-pressure imaging experiment, the interfacial region between PEO and PMMA was studied. Sorption of high-pressure CO2 in both polymers was studied simultaneously. The effect of temperature and pressure on the solub...

Dynamic properties of polyvinylmethylether near the glass transition

Dielectric spectroscopy, encompassing 13 decades of frequency, was used to investigate local segmental relaxation in polyvinylmethylether (PVME). Measurements were obtained over a 110 degree range of temperatures, at pressures up to 725 MPa. At atmospheric pressure, time-temperature superpositioning is valid; however, application of pressure changes the shape of the dielectric spectrum. Similarly, the relaxation times and dc-conductivity have the same temperature dependence at ambient pressure, while a breakdown of the Debye–Stokes–Einstein relation is observed at elevated pressures. The pressure dependence of the relaxation times is weak, corresponding to an activation volume about equal in magnitude to the molar volume of the PVME repeat unit. The pressure coefficient of the glass transition temperature (Tg=247.5 K at ambient pressure) is small, 177 K/GPa. From the ratio of the isochronic and isobaric expansivities, =2.2, thermal energy is found to have a stronger effect on the relaxation times than does the volume, although the contribution from the latter is significant. A comparison was made of the relaxation properties of PVME to those of the structurally similar polyvinylacetate. Distinct, qualitative differences are noted at both ambient and elevated pressure.

Effect of shear flow on the phase‐separation behavior in a blend of polystyrene and polyvinyl methyl ether

AbstractThe phase behavior and phase‐separation dynamics of polystyrene/polyvinyl methyl ether (PS/PVME) blend with a critical composition of 70 vol % PVME were examined with a light scattering technique under a shear‐rate range of 0.1–40 s−1. If the shear rates were less than 8 s−1 and the starting temperatures of the measurement were 343 and 383 K, respectively, two cloud points were observed, whereas after the shear rate was higher than 8 s−1, only one cloud point existed, 20 K higher than that of the static state of the blend. Investigation of the phase‐separation dynamics at 443 K suggested that in the vorticity direction the phase‐separation behavior at the early stage and the later stage can be explained by Cahn–Hilliard linearized theory and the exponent growth law, respectively. Phase separation occurs after a shearing time, which was called a delay time τd. The delayed time τd, the apparent diffusion coefficient, and the exponent term of the blend show strong dependence on shear rates. A theoretical prediction of the phase behavior of PS/PVME under a shear flow field by introducing an elastic energy term into Flory's equation‐of‐state theory was made, and the prediction was consistent with the experimental results. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 661–669, 2003

Influence of Hydrotropes and Glycols on the Clouding Behavior of Surfactants (TritonX 100 and Brij 56) and Polymers (Polyvinylmethyl Ether and Triblock Co-Polymer, Pluronic 85)

Nonionic surfactants and water-soluble polymers undergo phase transition and clouding at elevated temperature. The process can be influenced by the presence of additives. In this work, we have studied the clouding of the surfactants, TritonX 100 and Brij 56 as well as the polymers, polyvinylmethylether and a triblock co-polymer, Pluronic 85 in the presence of a number of hydrotropes, glycols and polyethylene oxides. The clouding temperatures with the additive concentration have been determined and the energetics of the process has been estimated. It has been found that the enthalpic behavior of TritonX 100 was different from that of polyvinylmethylether and Pluronic 85. The enthalpy and entropy have nicely compensated each other. The clouding of Brij 56 and TX 100 have a direct dependence on the number of ethylene groups in the glycols and the molar mass of the polyethylene oxides. The hydrotropes, on the whole, have decreased the cloud point of TX 100, polyvinylmethylether and Pluronic 85. Sodium cholate and sodium salicylate have increased the cloud point. But a correlation of the cloud points with the chemical nature of the hydrotropes is difficult to ascertain.

Gas transport and thermodynamic properties of PMMA/PVME blends containing PS-b-PMMA as a compatibilizer

Gas transport and thermodynamic properties of polymethylmethacrylate (PMMA) blended with polyvinylmethylether (PVME) containing diblock copolymer of styrene and methylmethacrylate (PS-b-PMMA) as a compatibilizer were studied. Phase separation temperatures of PVME blends with styrenic random copolymer containing various amounts of methyl methacrylate (MMA) were determined to calculate the interaction energies of the binary pairs involved in this system using lattice fluid theory combined with the binary interaction model. The separated phase structure of the blend that is related to interaction energy was controlled with an interfacial agent, i.e. PS-b-PMMA. The average diameter of the dispersed particles in PMMA/PVME blend was decreased for the blends containing PS-b-PMMA from 0 to about 5 parts per hundred (phr) and then leveled off at a fixed value. Accordingly, oxygen and nitrogen gas permeability coefficients of the blend membrane increased with compatibilizer content, until it reached 5 phr and then leveled off. A trade-off between permeability and selectivity for blends containing various amount of compatibilizer was observed. The continuous path from top to bottom of membrane formed by reducing the dispersed particle size might cause an increase of gas permeability at the same blend composition.

Secondary effects of antioxidant on PS/PVME blends

Interactions between the antioxidant Santonox (4,4′-thiobis(6-tert-butyl-m-cresol)) and the LCST polymer blend of polystyrene (PS) and polyvinylmethylether (PVME) were examined. The presence of the antioxidant caused inhomogeneities in blend films cast from toluene solutions at antioxidant compositions greater than 0.25wt% of the PVME. Also, the cloud-point of the blend decreased linearly with antioxidant content with a slope of 21°C/wt%. As expected, the ability of the antioxidant to prevent degradation of the PVME within the blend was found to increase with increasing Santonox composition. Based on these results, an antioxidant composition of no more than 0.10wt% is recommended in the studies of PS/PVME blends.

Phase ordering in blend films of semi-crystalline and amorphous polymers

A combination of optical and atomic force microscopy (AFM) is used for probing changes in the morphology of polymer blend films that accompany phase ordering processes (phase separation and crystallization). The phase separation morphology of a “model” semi-crystalline (polyethyleneoxide or PEO) and amorphous (polymethylmethacrylate or PMMA) polymer blend film is compared to previous observations on binary amorphous polymer blend films of polystyrene (PS) and polyvinylmethylether (PVME). The phase separation patterns are found to be similar except that crystallization of the film at high PEO concentrations obscures the observation of phase separation. The influence of film defects (e.g., scratches) and clay filler particles on the structure of the semi-crystalline and amorphous polymer films is also investigated.