Darzen's glycidic ester condensation reaction on poly(N-vinyl pyrrolidone)

About 38% conversion of carbonyl groups into epoxy functions in the molecular chain of poly(N-vinyl pyrrolidone) using chloracetamide results in the decreased viscosity of the product. De-epoxidation of the epoxy groups introduced shows the most contributing factor towards decreased viscosity is epoxy function.     

Miscible blends of poly(N-vinyl pyrrolidone) with some hydroxyl-containing polymers

Summary Poly(N-vinyl pyrrolidone) (PVPr) forms miscible binary blends with poly(hydroxyethyl methacrylate), poly(hydroxypropyl methacrylate) and two styrene/allyl alcohol copolymers, as shown by their glass transition behavior. However, PVPr is immiscible with poly(ethyl methacrylate), poly(n-propyl methacrylate) and polystyrene. The results indicate the importance of hydroxyl groups in achieving miscibility.     

The glass transition temperature of poly(N-vinyl pyrrolidone) by differential scanning calorimetry

Previously a wide range of values have been reported for the glass transition temperature, T_g, of poly(N-vinyl pyrrolidone), PVP, and it was suggested that lower values are due to variable uptakes of water caused by the hygroscopic nature of the polymer. Now it has been found that there are large variations in T_g, even in carefully dried specimens of PVP. Other factors found to influence T_g are residual monomer and the molecular weight of PVP. Polymers prepared by bulk polymerization, either by γ-irradiation or by heating with 2-azobisisobutyronitrile, have much lower values of T_g than dried ones prepared containing 30% water. The difference is mainly due to depression of T_g by residual monomer which, in the absence of water during polymerization, fails to react completely because of conversion to a glassy state. An unexplained observation is that even when all residual monomer has been removed, polymers prepared by bulk polymerization still have a lower T_g than would be expected from their molecular weight.     

Synthesis of well-defined functional macromolecular chimeras based on poly(ethylene oxide) or poly(N-vinyl pyrrolidone)

By using either NH₂-functionalized linear/4-arm star poly(ethylene oxide) or NH₂-TEMPO initiator, the following novel polymer/polypeptide hybrids (macromolecular chimeras) of poly(ethylene oxide), PEO and poly(N-vinyl pyrrolidone), PNVP, were synthesized: PEO-b-(PBLG or PBLL), PEO-b-PBLL-b-PBLG, 4-arm star copolymer (PEO-b-PBLG)₄, PNVP-b-PBLG-b-PBLL, where PBLG is poly(γ-benzyl-l-glutamate) and PBLL, poly(tert-butyloxycarbonyl-l-lysine). The amino-groups are used for the ring opening polymerization (ROP) of α-amino acid carboxyanhydrides (NCAs), while TEMPO was employed for the polymerization of NVP. Molecular characterization revealed the high molecular weight and compositional homogeneity of the macromolecular chimeras prepared. The success of the synthesis was based on the recently developed living ROP of NCAs and controlled/living TEMPO polymerization, using high vacuum techniques.     

Pressure-sensitive adhesion in the blends of poly(N-vinyl pyrrolidone) and poly(ethylene glycol) of disparate chain lengths

Adhesive behavior in blends of high molecular weight poly(N-vinyl pyrrolidone (PVP) with a short-chain, liquid poly(ethylene glycol) (PEG) has been studied using a 180° peel test as a function of PVP-PEG composition and water vapor sorption. Hydrophilic pressure-sensitive adhesives are keenly needed in various fields of contemporary industry and medicine, and the PVP-PEG blends, pressure-sensitive adhesion has been established to appear within a narrow composition range, in the vicinity of 36 wt% PEG, and it is affected by the blend hydration. Both plasticizers, PEG and water, behave as tackifiers (enhancers of adhesion) in the blends with glassy PVP. However, PEP alone is shown to account for the occurrence of adhesion, and the tackifying effect of PEG is appreciably stronger than that of sorbed water. Blend hydration enhances adhesion for the systems that exhibit an apparently adhesive type of debonding from a standard substrate (at PEG content less than 36 wt%), but the same amounts of sorbed water are also capable of depressign adhesion in the PEG-overloaded blends, where a cohesive mechanism of adhesive joint failure is typical. The PVP-PEG blend with 36% PEG couples both the adhesive and cohesive mechanisms of bond rupture (i.e., the fibrillation of adhesive polymer under debonding force and predominantly adhesive locus of failure). Blend hydration effect on adhesion has been found to be reversible. The micromechanics of adhesive joint failure for PVP-PEG hydrogels involves the fibrillation of adhesive polymer, followed by fibrils stretching and fracturing as their elongation attains 1000-1500%. Peel force to rupture the adhesive bond of PVP-PEG blends increases with increasing size of the tensile deformation zone, increasing cohesive strength of the material, and increasing tensile compliance of the material, obeying the well-known Kaelble equation, derived originally for conventional rubbery pressure-sensitive adhesives. The major deformation mode upon peeling the PVP-PEG adhesive from a standard substrate is extension, and direct correlations have been established between the composition behaviour of peel strength and that of the total work of viscoelastic strain to break the PVP-PEG films under uniaxial drawing. As a result of strong interfacial interaction with the PET backing film, the PVP-PEG adhesive has a heterogeneous two-layer structure, where different layers demonstrate dissimilar adhesive characteristics.     

Rheological investigation of poly(vinyl alcohol)/poly(N-vinyl pyrrolidone) mixtures in aqueous solution and hydrogel state

Rheological behavior of poly(vinyl alcohol) (PVA) and poly(N-vinyl pyrrolidone) (PVP) mixtures in aqueous solutions and hydrogel state was investigated. The complex dependence of the viscosity on PVA/PVP mixture composition could be attributed to cumulative effects of electrostatic interactions, hydrogen bonding or association phenomena. Physical hydrogels were prepared by freezing/thawing method and their viscoelastic properties were followed as a function of number of cryogenic cycles and aging time at 37 °C. From swelling experiments, it was observed that the diffusion of water molecules into the hydrogel pores is Fickian (for low number of cryogenic cycles) and it becomes pseudo-Fickian as the sample is submitted to more than 10 freezing/thawing cycles. PVA/PVP hydrogels obtained by physical interactions present a high degree of tailorability and they are suitable candidates for biomedical applications.     

Cell patterning on a poly(N-vinyl pyrrolidone)-patterned polystyrene substrate by using ion implantation

In this study, a simple strategy for micropatterning of cells was developed by using ion implantation that does not require any harsh chemicals and complicated processes. Thin poly(vinyl pyrrolidone) (PVP) films spin-coated on a nonbiological polystyrene Petri dishes were implanted with accelerated proton ions through a pattern mask and then developed with water to generate the patterns of the PVP. The results of the ATR-FTIR and XPS analysis revealed that the chemical compositions of the PVP were not significantly changed by ion implantation and thus the intrinsic biocompatibility of the PVP can be preserved. The in vitro cell culture on the patterned PVP showed selective alignment of cells on the PVP regions of the patterns and thus well-defined 100 μm patterns of the cells were obtained. These results revealed that this strategy is biocompatible and simple to use for biomolecular patterning, which can be used in further biological applications.     

Reaction-induced microphase separation in polybenzoxazine thermosets containing poly(N-vinyl pyrrolidone)-block-polystyrene diblock copolymer

Poly(N-vinyl pyrrolidone)-block-polystyrene diblock copolymer (PVPy-b-PS) was synthesized via sequential reversible radical-fragmentation transfer polymerization with S-1-phenylethyl O-ethylxanthate as a chain transfer agent. The block copolymer was incorporated into polybenzoxazine to access the nanostructures in the thermosets. The nanostructures in the thermosets were investigated by means of transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). It was found that disordered and/or ordered PS nanophases were formed in the PBa thermosets. It is judged that the formation of nanophases followed the mechanism of reaction-induced microphase separation in terms of the miscibility of the subchains of the diblock copolymer (viz. PVPy and PS) with polybenzoxazine after and before curing reaction.     

Dipole moments of poly(allyl methacrylate) prepared by group transfer polymerization

Dipole moments of poly(allyl methacrylate) prepared by group transfer polymerization and of allyl methacrylate were determined from dielectric constant, refractive index increment and density measurements performed on their dilute benzene and carbon tetrachloride solutions within a temperature range of 25–60°C. Dipole moments ratios and temperature coefficient, d ln〈μ²〉/dT, where 〈μ²〉 is the mean-square dipole moment of the chain, were calculated. These results are compared with earlier results.     

Crystal growth inhibition of tetrahydrofuran hydrate with poly(N-vinyl piperidone) and other poly(N-vinyl lactam) homopolymers

Poly(N-vinyl pyrrolidone) (PVP) containing the 5-ring lactam and poly(N-vinyl caprolactam) (PVCap) containing the 7-ring lactam are well-known kinetic hydrate inhibitors (KHIs). For the first time we have synthesised and studied the performance of poly(N-vinyl piperidone) (PVPip), containing the 6-ring lactam, as a kinetic hydrate inhibitor. In the first part of the study we have investigated the ability of PVPip to inhibit the growth of tetrahydrofuran SII hydrate crystals. The results are compared to those of PVP and PVCap. Various polymer molecular weights have been investigated at varying subcoolings. PVPip shows an intermediate growth inhibition performance compared to PVP and PVCap at similar polymer molecular weights. In addition, the weight percentage concentration of polymer needed to achieve complete THF hydrate crystal growth inhibition increases as the polymer molecular weight decreases.     

Investigation on the interpenetrating polymer networks (ipns) of polyvinyl alcohol and poly(N-vinyl pyrrolidone) hydrogel and its in vitro bioassessment

Poly(vinyl alcohol) (PVA) and poly(N-vinyl pyrrolidone) (PVP) composite hydrogel with interpenetrating polymer networks (IPNs) was prepared by in situ polymerization and compared with pure PVA hydrogel. The prepared IPN hydrogel was characterized by infrared spectroscopy (IR), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy. The mechanical property and cell culture were also tested. The results show that PVP can chemically bond with PVA and form uniform blend hydrogel. The content of PVP can affect the structure, crystallinity, glass transition temperature (T_g), and mechanical property of the hydrogel. The T_g of the PVA hydrogel is 2.7°C while the T_g of the IPN hydrogel is −37°C. The IPN hydrogel has lower glass transition temperature, corresponding to better elastic properties, and has better mechanical performance on stretch and compression than PVA hydrogel. The crystallinity (X_c) of PVA hydrogel and IPN hydrogel is 65.3 and 26.3%, respectively. The DMA curves and XPS analysis suggest that PVA and PVP are well miscible on a molecular level in the IPN hydrogel. The cell proliferation trend demonstrates that the addition of PVP has a positive influence on the cell growth and the IPN hydrogel may be used as a promising biomaterial for artificial cartilage substitute. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Co(III) acetylacetonate-complex-initiated grafting of N-vinyl pyrrolidone on cellulose in aqueous media

The graft copolymerization of N-vinyl pyrrolidone (N-VP) onto cellulose was carried out with a cobalt acetylacetonate complex Co(acac)₃ as an initiator under a nitrogen atmosphere at 50 ± 0.1°C. The graft yield percentage (%G) obtained as a function of the concentrations of N-VP and Co(acac)₃ and the temperature was used to calculate various other grafting parameters and the grafting rate dependence on the concentrations of monomer, Co(acac)₃ and reaction temperature. The energy of activation (ΔE_a) for the grafting of N-VP onto cellulose was 22.7 kJ/mol within 40–60°C. The molecular weights of the grafted chains and homopolymers were determined viscometrically with a Ubbelohde-type viscometer. Graft yield (%G) in the presence of various additives such as sodium lauryl sulfate, cetyltrimethylammonium bromide, and methanol was studied, and the results are suitably explained. On the basis of the experimental results, a reaction scheme for graft copolymerization is proposed, and a kinetic rate expression is presented. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2286–2296, 2001     

Conformational characteristics of poly(ethylene oxide) (PEO) in methanol

The conformational characteristics of poly(ethylene oxide) (PEO) in methanol at 25 °C were investigated by static light scattering and viscometry for high molar mass (M_w) PEO fractions covering M_w = 3.42 × 10⁵-5.05 × 10⁶ g mol⁻¹. No trace of downturn in the plot of angular dependence of Kc/R_θ at low angle was found. Experimental scaling laws for the second virial coefficient (A₂), the third virial coefficient (A₃), the radius of gyration and the intrinsic viscosity ([η]) were determined. The exponents characterizing these scaling laws confirmed that the PEO chain in methanol has a flexible conformation with relatively large excluded volume, but methanol is not as good solvent as water. On the other hand, the low value of interpenetration function (Ψ) and the relatively higher order of the dimensionless parameter Π are considered to be an indication of local chain stiffness. All the results obtained in this study allow us to conclude that the overall chain conformation of PEO assumed in methanol is basically a random coil, but is intermittently mixed with helical structure.     

Preparation of polyacrylonitrile nanoparticles via dispersion polymerization of acrylonitrile using a poly(N-vinyl pyrrolidone)-cobalt complex in an aqueous system

Monodisperse spherical polyacrylonitrile (PAN) nanoparticles were successfully prepared for the first time by dispersion polymerization of acrylonitrile (AN) in water using well-defined poly(N-vinyl pyrrolidone) (PVP) that was end-capped by a cobalt(II) acetylacetonate (Co(acac)₂) complex (PVP-Co(acac)₂) as both a macroinitiator and a colloidal stabilizer. The well-defined PVP-Co(acac)₂ (M_n = 14,000 g/mol, PDI = 1.25) was synthesized by the bulk cobalt-mediated radical polymerization of N-vinyl pyrrolidone at 20 °C using 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) as an initiator and Co(acac)₂ as a regulating agent. The PVP macroradicals generated at 30 °C by the homolytic cleavage of the C–Co bonds in PVP-Co(acac)₂ initiated the dispersion polymerization of AN, as well as successfully stabilized the growing PAN particles. The average diameters of PAN nanoparticles synthesized with 20, 30, 40, and 50 wt% of PVP-Co(acac)₂ at 30 °C for 24 h were 263.5, 163.1, 157.3, and 143.5 nm, respectively. The PAN nanoparticles had a slightly crumpled spherical appearance, and the degree of crystallinity of the PAN nanoparticles prepared using 30 wt% of PVP-Co(acac)₂ was 31.2%. The mol% of VP units in the PAN nanoparticles was about 6 mol%, and the PVP chains were present on the surface of the PAN nanoparticles as a stabilizing layer. The PVP hairy chains could successfully stabilize very small Ag nanoparticles on the surface of the PAN nanoparticles.     

Thermal behavior of poly(acrylic acid)–poly(vinyl pyrrolidone) and poly(acrylic acid)–metal–poly(vinyl pyrrolidone) complexes

Thermal analysis (TGA and DTA) of samples of PAA, PVP, PAA–PVP complexes, containing different weight fractions of PAA and ternary polymer–metal–polymer complexes, were studied. The activation energy parameters for the thermal degradation were also calculated. The study of the effect of FeCl₃, NiCl₂, and Ni(NO₃)₂ on the TGA and DTA curves of the complexes showed that the decompositions are dependent on the concentrations and the nature of the metal ions. The DTA traces of PAA–PVP complex containing FeCl₃, NiCl₂, and Ni(NO₃)₂ showed that the treatment of the complex with these metal ions causes considerable changes in the thermal decomposition of PAA–PVP complex. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4049–4057, 2006     

Removal of anionic dyes from aqueous solution using poly [N-vinyl pyrrolidone/2-(methacryloyloxyethyl) trimethyl ammonium chloride] superswelling hydrogels

Summary A superswelling poly [N-vinyl pyrrolidone/2-(methacryloyloxyethyl)trimethyl ammonium chloride], poly(NVP/METAC) hydrogels were prepared by free radical polymerization using ethylene glycol dimethacrylate as crosslinker. The hydrogels were characterized by FT-IR spectroscopy and their surface morphology was determined using Scanning Electron Microscope (SEM). The influence of feed composition of both the monomers and crosslinker on equilibrium swelling and dye adsorption properties of the hydrogels were examined. The equilibrium swelling ratio and binding ratio of the hydrogel/dye systems greatly depends on the METAC and crosslinker concentration in the gels. The effects of pH of the medium and initial dye concentration on the adsorption were also studied. The binding ratio of the hydrogel/dye system increases in the following order: OR-II>RO-14>RO-13.     

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     

Characterization and properties of poly(ethylene oxide) and its blends with poly (N-vinyl carbazole)

The calorimetric properties and dynamic mechanical behaviour of pure poly(ethylene oxide) (PEO) and its blends with poly(N-vinyl carbazole) (PNVK) have been examined as a function of composition in the range 50-100% PEO. Thermomechanical measurements indicate the presence of a phase separation in this blend. Using the Hoffman-Weeks plot no equilibrium melting point depression was found in any of the blends studied. Some kinetic interfacial effects were detected in the crystallization processes. For all blend compositions, the Avrami exponent is close to that obtained for pure PEO. The DMTA and DTA results suggest an incompatibility in this system.