Gas transport in poly(vinyl benzoate)

The transport parameters of nine gases (O₂, N₂, CO₂, He, Ne, Ar, Kr, Xe) through poly(vinyl benzoate) (PVB) have been measured by the time lag method above and below the glass transition temperature, T_g The results are compared with the related data of poly(vinyl acetate) (PVAc) by Meares and discussed as the effect of replacement of the methyl group by a phenyl group in the side chain of PVAc. Small molecules, such as H₂, He, and Ne, diffuse more easily through PVAc than PVB, but the tendency is reversed for the larger gases. The activation energy for diffusion is proportional to the squares of the Lennard–Jones diameters of the gases below the T_g. On the other hand, above the T_g, linear relation is obtained to the cubes of the diameters. Solubility behavior is discussed by comparing the heats of solution for PVB and PVAc.     

Gas transport in poly(vinyl-p-isopropylbenzoate): Comparison and correlation with some other poly(vinyl esters)

Gas permeability in poly(vinyl-p-isopropylbenzoate) (PVp-i-PrB) was determined by a timelag method. The transport properties were discussed from comparison with the permeability data of other poly(vinyl esters), which were studied previously. All these polymers are structurally related, and the size of a side group or the position of its substituent was changed systematically. The isopropyl group of PVp-i-PrB is attached at the para position of a phenyl ring and is the largest in size. As a result gas diffusivity and therefore permeability were increased. The effect of the substituent on gas diffusivity was explained as it increases the interchain and intrachain distances. The discussion was supported from the comparison of the density data between PVp-i-PrB and other poly(vinyl esters). The diffusion coefficients of six glassy poly(vinyl esters) were correlated at their T_g and good correlations were shown to the free volume and its fraction. On the other hand, gas solubility was little affected by the change of an alkyl group on a phenyl ring. The solubility data of PVp-i-PrB and poly(vinyl benzoate) were shown to be clearly correlated with the critical properties of the penetrants. © 1995 John Wiley & Sons, Inc.     

Noble gas transport in poly(methyl vinyl ketone) and poly(methyl vinyl ether)

A systematic study and interpretation of the transport parameters characterizing the permeation of the noble gases, He, Ne, Ar and Kr through poly(methyl vinyl ketone) and poly(methyl vinyl ether) are presented. The results and correlations are compared with related measurements on poly(methyl acrylate) and poly(vinyl acetate). In general the measurements were conducted above the glass transition temperatures of the respective polymers. The results are interpreted in terms of the systematic variations in the physicochemical parameters of these closely related polymers. Free volume and dipoledipole interactions appear to dominate the observed behaviour and the composite results may be explained in these terms. The size distribution of the fluctuating free volume elements and chain stiffness are also to be considered.     

Gas transport in poly(alkoxyphosphazenes)

The permeability of four structurally related poly(alkoxyphosphazenes), three isomers of poly(dibutoxyphosphazenes) (PBuP), and poly(di-neopentyloxyphosphazene) (Pneo-PeP), to 13 gases has been determined by the time-lag method. Systematic variations in chemical structure have shown a large effect of side chains on permeabilities and permselectivities. The permeability of poly(di-n-butoxyphosphazene) (Pn-BuP) is of the order of 10^?8 cm³ (STP) cm/(cm² s cmHg) for many gases, and the value for a large gas is higher than that for a smaller one. For small gases such as He and H₂, poly(di-sec-butoxyphosphazene) (Ps-BuP) is as permeable as Pn-BuP, but its diffusivities for larger gases such as Xe and C₃H₈ are about one order lower than those of Pn-BuP. While the permselectivity of Pn-BuP is determined by the solubility, that of Ps-BuP depends on both the diffusivity and solubility factors. The property of poly(diisobutoxyphosphazene) (Pi-BuP) is intermediate between them. These polymers are constitutionally identical, and the only difference is the arrangements of carbons in the side groups. As the side chains become bulky, the permeability decreases, whereas the permselectivity increases. Further decreases of diffusivity and then permeability are observed for Pneo-PeP, whose side groups have one more methyl group than does Pi-BuP. But the solubility data are not much different from other three polymers and the diffusivity factor becomes more significant in permselectivity. The diffusivity depends on the polymer structure much more than does the solubility. The relationships between chemical structure and gas diffusivity and solubility are discussed.     

Gas transport properties of poly(3-hydroxyoxetane)

Gas transport properties for poly(3-hydroxyoxetane) (PHO) were measured for five gases at 35°C. While PHO has very low gas permeability coefficients, they are larger than those reported for polyacrylonitrile (PAN), poly(vinyl alcohol) (PVA1) and copolymers of ethylene / vinyl alcohol (EVAL) for all gases tested except He. The permeability coefficients for PHO and EVAL are well correlated with the density of hydroxyl groups along the chain. Extrapolations to PVA1 give values that agree well with those estimated by Salame using the Permachor method. It is suggested that some of the reported experimental values for PVA1 are in error. © 1993 John Wiley & Sons, Inc.     

Preparation,structure, and transport properties of ultrafiltration membranes of poly(vinyl chloride) and poly(vinyl pyrrolidone) blends

Ultrafiltration (UF) membranes based on poly(vinyl chloride) and poly(vinyl pyrrolidone) blends were prepared by the phase inversion method, and the factors governing membrane properties were investigated. The membranes were characterized by scanning electron microscopy and atomic force microscopy. The fouling characteristics of the membranes were determined by UF of aqueous solutions of bovine serum albumin (BSA) over a pH range of 2–9 and varying salt concentrations. The maximum adsorption of the protein on the membrane surface occurred near the isoelectric point (pI 4.8) of BSA, and the presence of the salts increased the fouling of the membrane. The results can be explained in terms of the nature of the membrane polymer and the effect of different ionic environments on the permeability of the deposited protein layer. The net charge on the BSA molecules appears to be a dominant factor in determining the flux of water through the blend membranes. The UF flux is correlated by a model based on the membrane resistance, adsorbed protein resistance, and time dependent resistance of the concentration polarization layer near the membrane surface. The ζ potentials of the membranes were also determined before and after UF to characterize the surface potential of the membrane. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2606–2620, 2000     

Synthesis of poly(vinyl benzal) from poly(vinyl alcohol) in nonaqueous medium

Poly(vinyl alcohol) (PVA) is soluble only in water and so some important derivatives like esters cannot be prepared from PVA. The 100% conversion of PVA to acetal is also elusive as there is strong intermolecular and intramolecular hydrogen bonding. However, PVA can be dissolved in a nonaqueous medium in the presence of a small amount of C₂H₅NO₃ · DMSO(EN · DMSO) and so a maximum extent of conversion may be possible. Here, we report the preparation of poly(vinyl benzal) (PVB) by acid-catalyzed homogeneous acetalization of PVA with benzaldehyde in a nonaqueous medium. The formation of PVB was confirmed by IR and ¹H-NMR spectra. The molecular mass of the polymer was determined by the GPC method. The PVB prepared had a degree of acetalization of 95 mol%. The glass transition temperature, T_g was measured from differential scanning calorimetric (DSC) thermograms. Thermal stabilities were checked by thermogravimetric analysis (TGA) and differential thermogravimetry (DTG). A possible mechanism of three-step thermal decomposition of PVB is proposed. © 1996 John Wiley & Sons, Inc.     

Compatibility of nylon 6 with poly(vinyl alcohol), hydroxylated poly(vinyl acetate) and poly(vinyl acetate)

Summary The compatibility of nylon 6 with poly(vinyl acetate)(PVAc) and poly(vinyl alcohol)(PVA) was investigated in terms of the melting-temperature depression. In order to vary the compatibility systematically, a hydroxylated poly(vinyl actate)(m-PVAc) was prepared by hydrolyzing PVAc with KOH in CH₃OH. It was found that the compatibility with nylon 6 is better in the systematic order PVA> m-PVAc> PVAc.     

Gas transport in poly[bis(trifluoroethoxy)phosphazene]

The gas transport parameters of 14 gases in poly[bis(trifluoroethoxy)phosphazene] were determined at temperatures ranging from about 12 to 45°C by the time-lag method. The phosphazene polymer demonstrated a high diffusivity; rather high crystallinity was expected, though. The permeation data determined were between polydimethylsiloxane and low-density polyethylene. The most interesting characteristic shown over the course of experimentation is that poly[bis(trifluoroethoxy)phosphazene] has significantly high solubility for CO₂, as compared to other gases. The polar side groups—i.e., the electron-withdrawing trifluoroethoxy parts—which should contribute specific interaction with CO₂, were shown to be stronger than their interaction with the polar N₂O molecule. The sorption behavior is compared with those of other rubbery polymers, while phosphazene polymer characteristics are also discussed.     

Miscibility in poly(vinyl chloride)/chlorinated poly(vinyl chloride) blends,and blends of different chlorinated poly(vinyl chlorides)

Blends of poly(vinyl chloride) with chlorinated poly(vinyl chloride) (PVC), and blends of different chlorinated poly(vinyl chlorides) (CPVC) provide an opportunity to examine systematically the effect that small changes in chemical structure have on polymer-polymer miscibility. Phase diagrams of PVC/CPVC blends have been determined for CPVC's containing 62 to 38 percent chlorine. The characteristics of binary blends of CPVC's of different chlorine contents have also been examined using differential calorimetry (DSC) and transmission electron microscopy. Their mutual solubility has been found to be very sensitive to their differences in mole percent CCl₂ groups and degree of chlorination. In metastable binary blends of CPVC's possessing single glass transition temperatures (T_g) the rate of phase separation, as followed by DSC, was found to be relatively slow at temperatures 45 to 65° above the T_g of the blend.     

Solvent-free generation of poly(vinyl acetals) directly from poly(vinyl acetate)

The simultaneous methanolysis and butryalization of poly(vinyl acetate) was conducted via the reaction of methanol and butyraldehyde with polyvinyl acetate under batch conditions at temperatures from 70°C to 90°C at the vapor pressure of the reactants. It was found that use of an acid catalyst allowed for the methanolysis to be the rate limiting step of a simultaneous methanolysis-butyralization reaction, minimizing the buildup of alcohol repeat units in the polymer during the reaction. As such, use of an excess of aldehyde was counterproductive in that it served to dilute both the methanol and the acetate groups in the polymer phase, lowering the overall rate of the reaction. With 20% stoichiometric excesses of methanol and butyraldehyde, it was possible to produce poly(vinyl butyral) directly from poly(vinyl acetate) with very low residual acetate and overall conversions equivalent to commerical samples. Further, carbon dioxide was evaluated as a reversible plasticizer for polyvinyl acetate during methanolysis. Results at various pressures were consistent with the expectation that the presence of CO₂ would lower the reaction rate, primarily because of dilution of reactants in the CO₂-swollen polymer phase. Finally, it was shown that the simultaneous reaction procedure can be used to generate polyvinyl acetals from a variety of aldehydes.     

Characterization of associating hydrogels of poly(vinyl alcohol) and poly(vinyl pyrrolidone)

In this study, hydrogels were prepared from blends of poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP). The miscibility of the polymers was confirmed with differential scanning calorimetry with the appearance of a single glass‐transition temperature. Additionally, a negative Flory–Huggins interaction parameter further verified the interaction between PVA and PVP. We evaluated the stability of the hydrogels by swelling the gels in phosphate‐buffered saline solutions at pH 7.4. With attenuated total reflectance‐Fourier transform infrared spectroscopy, it was determined that, during swelling, PVP dissolved out of the gel over time and the equilibrium gel content of PVP was nearly identical in all of the samples investigated. After the dissolution of PVP, the equilibrium water content of the gels ranged from 64 to 76 wt %. Additionally, rubber elasticity studies were performed to elucidate information about the physically crosslinked network structure. As determined from rubber elasticity experiments, the mesh size of the physically crosslinked hydrogels ranged from 90 to 230 Å. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Poly(vinyl chloroformate) and its derivatives: 5. New poly(vinyl carbamates) and poly(vinyl thiocarbonates)

New poly(vinyl carbamates) and poly(vinyl thiocarbonates) have been prepared either by free radical polymerization of monomers or by chemical modification of poly(vinyl chloroformate) with appropriate amines and thiols using phase transfer catalysis. The structure of these polymers has been examined by i.r. and ¹³C n.m.r. spectroscopy and their thermal behaviour has been studied.     

Thermal characteristics of poly(ethylene terephthalate) fiber grafted with poly(vinyl acetate) and poly(vinyl alcohol)

Poly(ethylene terephthalate) (PET) fibers were grafted with poly(vinyl acetate) (PVAc) and poly(vinyl alcohol) (PVA). The effects of graft copolymers PVAc and PVA on morphological properties of PET were evaluated by differential thermal analysis, differential scanning calorimetry, and thermogravimetric analysis. Melting temperature, heat of fusion, and mass fractional crystallinity of PET was not affected by graft PVAc and PVA. No individual glass transition and melting points corresponding to the graft PVAc and PVA were observed, indicating thereby that graft copolymer mainly exists in the form of free chains inside the PET matrix. Poly(vinyl alcohol) graft copolymer degraded at much lower temperatures than poly(vinyl alcohol) in powder form. Thermal stability of PET fiber was not affected by graft PVAc, where as PET–g–PVA showed an additional degradation point at 360°C.     

An overview of poly(vinyl alcohol) and poly(vinyl pyrrolidone) in pharmaceutical additive manufacturing

Recently, drug personalization has received noticeable attention. Problems arising from standard generalized drug treatments have aroused over the years, particularly among pediatric and geriatric patients. The growing awareness of the limitations of the “one-size-fits-all” approach has progressively led to a rethinking of the current medicine's development, laying the basis of personalized medicine. Three-dimensional printing is a promising tool for realizing personalized therapeutic solutions fitting specific patient needs. This technology offers the possibility to manufacture drug delivery devices with tailored doses, sizes, and release characteristics. Among additive manufacturing techniques, fused deposition modeling (FDM) is the most studied for oral drug delivery device production due to its high precision and cheapness. By playing with factors such as drug loading method, filament production, and printing parameters, the medication release profile of a drug delivery device produced by 3D printing can be tailored depending on the patient's requirements. This review focuses on the applications of FDM in drug fabrication using poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) as drug-loaded matrices. The authors aim to provide an overview of the current trends in this research field, with special attention to the effect of the printing parameters, tablet shape, and drug distribution and concentration on drug customization and personalized drug release.     

Miscibility enhancement on the immiscible poly (vinyl pyrrolidone) and poly (ethyl methacrylate) with poly (vinyl phenol)

The miscibility behavior of ternary blends of poly (vinyl phenol) (PVPh)/poly (vinyl pyrrolidone) (PVP)/poly (ethyl methacrylate) (PEMA) was investigated mainly with calorimetry. PVPh is miscible with both PVP and PEMA on the basis of the single T_g observed over the entire composition range. FTIR was used to study the hydrogen bonding interaction between the hydroxyl group of PVPh and the carbonyl group of PVP and PEMA at various compositions. Furthermore, the addition of PVPh is able to enhance the miscibility of the immiscible PVP/PEMA and eventually transforms it into a miscible blend, especially when the ratio between PVP/PEMA is 3:1, probably because of favorable physical interaction. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1205–1213, 2006     

Characterization of polymeric biocomposite based on poly(vinyl alcohol) and poly(vinyl pyrrolidone)

Biocompatible and easily available materials from dairy production waste were used for modification of water‐soluble polymeric blends of Poly(vinyl alcohol) (PVA) and Poly(vinyl pyrrolidone) (PVP). The resulting biocomposites of PVA/PVP with various concentrations of lactose (L) or calcium lactate (CL) (0, 5, 15, 25, 35 wt%) were prepared by using a solvent cast technique and then characterized by optical microscopy, tensile test, water content determination, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy equipped by attenuated total reflectance device, and also tested for biodegradability. The films were transparent with a smooth surface. The results confirm that L and CL work as fillers in polymeric matrix. The tensile investigations showed enhanced Young's modulus (E) and tensile strength for low‐filled of composite materials (up to 5 wt% L and 15 wt% CL). The biodegradation test in aquatic conditions revealed improved biodegradability of modified blends. Both L and CL seem to be suitable for the modification of polymers, which can be convenient from economical and environmental point of view. POLYM. COMPOS., 27:147–152, 2006. © 2006 Society of Plastics Engineers.     

The solubility of vinyl chloride in poly(vinyl chloride)

The solubility of vinyl chloride monomer (VCM) in PVC powders has been studied by equilibrium vapor pressure and microbalance gravimetric techniques at temperatures from 30 to 110°C. At temperatures and VCM concentrations above the glass transition, the solubility closely follows the Flory-Huggins equation with χ = 0.98 and is independent of temperature and of the PVC type, molecular weight, or history. In the glassy state, the VCM solubility is higher than the Flory-Huggins value and shows pronounced dependence upon time and the PVC history. These results have been interpreted through the dual-mode sorption concept of Michaels, Vieth, and Barrie: Normal dissolution follows the Flory-Huggins relation, and the additional glassy-state solubility represents the contribution of a hole-filling process. Changes in solubility with time and sample history parallel well-known volume relaxation processes, indicating that vapor solubility measurements offer a direct and sensitive measure of the free-volume state of glassy polymers.