Solvent effect on the formation of poly(methacrylic acid)-poly(N-vinyl-2-pyrrolidone) complex through hydrogen bonding

An interpolymer complex can be obtained by mixing the solutions of poly(methacrylic acid) and poly(N-vinyl-2-pyrrolidone). Three phase changes were observed on increasing the initial polymer concentration: namely, a homogeneous solution, a precipitate, and a gel. Such interpolymer complex formations were examined in several protic and aprotic solvents. The obvious relationship between the complex formation and the dielectric constant of the solvent was eludicated. The effect of hydrophobic interactions on the complex formation was also discussed as well as the role of the α-methyl group of poly(methacrylic acid).     

Complexation of poly(monobenzyl itaconate) and poly(N-vinyl-2-pyrrolidone) in dilute solution

Upon mixing dilute solutions (10^?4 – 10^?2 mol/l) of poly(monobenzyl itaconate) (PMBI) and poly(N-vinyl-2-pyrrolidone) (PVP) in methanol, soluble polycomplex particles are formed. Here we report on the spectrophotometric determination of the turbidity of different solutions of PVP and PMBI as a function of polymer concentration and PVP molecular weight. Viscosity measurements were also performed. The polycomplex is weak. Polycomplex particles are more compact and much larger than separated chains of polyacid and polybase. No definite stoichiometry is observed and a microgel-like structure is proposed.     

Miscibility of mixtures from partially hydrolyzed poly(vinyl acetate) and poly(N-vinyl-2-pyrrolidone)

Polymers with different compositions of vinyl alcohol and vinyl acetate units (P(VA-VAc)), obtained by alcoholysis of poly(vinyl acetate) with sodium methoxide, were mixed with poly(N-vinyl-2-pyrrolidone) (PVP). The miscibility was studied observing glass transition temperatures by differential scanning calorimetry (DSC). The calorimetric results indicate that for vinyl alcohol unit contents in P(VA-VAc) of roughly 70 wt.-% or more, P(VA-VAc)/PVP blends are fully miscible, whereas blends obtained from P(VA-VAc) with vinyl alcohol contents lower than the above mentioned values are only partially miscible or even immiscible. The miscibility is attributed to hydrogen bond interactions between hydroxyl groups in P(VA-VAc) and the carbonyl group of PVP.     

Studies of crosslinked poly(N-vinyl-2-pyrrolidone) by calorimetry and by NMR

Aqueous solutions of poly(N-vinyl-2-pyrrolidone) are converted to gels by reaction with potassium peroxydisulfate K₂S₂O₈. The degree of crosslinking in the gel fractions depends on the amount of persulfate used. The degree of crosslinking is related to the amount of non-freezing bound water in the gels by means of differential scanning calorimetry in the temperature range from −50°C to + 170°C. The chemical nature of the bonds formed during gelation is studied by ¹H and ¹³C NMR Spectroscopy and by swelling tests. NMR measurements point to the formation of aliphatic sidechains as well as crosslinks in the gelation. The swelling tests give low values for the number of crosslinks, hence the formation of branched chains strongly influences the properties of the gels. In contrast to what was expected no carboxyl groups are found in the gels.     

Molecular association in aqueous solutions of high molecular weight poly(N-vinyl-2-pyrrolidone)

A viscosimetric method was used to investigate the molecular association in aqueous solutions of poly(N-vinyl-2-pyrrolidone), (PVP), of molecular weight 700 000. Limiting viscosity numbers [η] and Huggins constants k_H of the polymer solutions were observed to decrease upon addition of denaturing agents such as thiourea and guanidinium sulfate. Guanidinium sulfate was found to be even more effective in its denaturing action as compared to urea and thiourea. The decrease in [η] and k_H values increased with increasing concentrations of the denaturing agents. This behaviour was explained on the basis of the rupture of bridges formed by water molecules among different PVP chains, hydrogen bonding being responsible for these intermolecular associations. While no change in the [η] values was observed for PVP in 2 M thiourea solutions upon increasing the temperature from 25°C to 35 and 45°C, for the same increase in temperature the [η] values of aqueous PVP solutions showed substantial decreases. This is also attributed to the breaking of hydrogen bonds existing between PVP molecules.     

Investigations of poly(vinyl alcohol)/poly(N-vinyl-2-pyrrolidone) blends, 1. Compatibility

Blends of crystallizable poly(vinyl alcohol) (PVA) with poly(N-vinyl-2-pyrrolidone) (PVP) made from aqueous solutions appear to be miscible in the whole composition range according to DSC results. A large negative value of the interaction parameter between the two polymers was found from melting point depressions. IR spectroscopy evidenced compatibility of the two polymers on a molecular level. DSC, density and IR results all show a proportion of pure PVA crystallites in blends, which decreases with increasing PVP content and becomes nil at about 50 wt.-% of PVP. However, close examination of the hydroxyl stretching region of the blends indicates the presence of organized regions of PVA beyond this limit. According to IR results, the sequence of decreasing hydrogen-bonding power should be the following: multiple hydroxyl-hydroxyl bonding in organized PVA regions, hydroxyl-carbonyl bonding between the two polymers, and simple hydrogen-hydrogen bonding in amorphous PVA regions. It appears that the PVA component can be held in the amorphous state by hydrogen bonding with the PVP component when there is a sufficient amount of the latter in the blend. The amorphous part of PVA is compatible with PVP, but the crystallizable part is not in its most stable form.     

Swelling behaviour of a non-ionic poly(N-vinyl-2-pyrrolidone) gel in a linear poly(acrylic acid) solution

The swelling behaviour of a non-ionic poly(N-vinyl-2-pyrrolidone) hydrogel in a linear poly-(acrylic acid) solution upon the influence of chain length, pH, ionic strength, and water/dimethyl sulfoxide composition was studied. The sharp shrinkage of the gel volume within a narrow range of polyacid concentration takes place as a result of the formation of an intermacromolecular gel-polymer complex on the base of hydrogen bonding. According to X-ray diffraction this complex is amorphous. The formation of the gel-polymer complex is a long term process and the system reaches equilibrium within 48 h. The swelling behaviour strongly depends on the chain length of the polyacid whereas it does not depend on the ionic strength. With increasing pH value and changing water/dimethyl sulfoxide composition the gel reswelling is induced. The complex formation with poly(acrylic acid) occurs in the same way for linear and crosslinked poly(N-vinyl-2-pyrrolidone).     

Study of the miscibility of poly(N-vinyl-2-pyrrolidone) with poly[styrene-co-(4-hydroxystyrene)]

Poly(N-vinyl-2-pyrrolidone) (PVP) was blended with poly[styrene-co-(4-hydroxytyrene)] (PSH) which was obtained from the random copolymer poly[styrene-co-(4-acetoxystyrene)] (PSA). The miscibility of PVP/PSH blends in a composition 1 : 1 by weight was evaluated by differential scanning calorimetry (DSC), non-radiative energy transfer (NET) and Fourier transform infrared (FTIR) spectroscopy. It was found that the blends become miscible when the hydroxystyrene units (HS) in PSH exceed 11 mol-%. The driving force of miscibility may be attributed to hydrogen bonding between ? OH in PSH and in PVP. The experimental results of miscibility were compared with that estimated from a “miscibility parameter” (MP) concept, and we found that the general trend of MP values is in agreement with the experimental results.     

Platelet interactions with plasma-polymerized ethylene oxide and N-vinyl-2-pyrrolidone films and linear poly(ethylene oxide) layer

Dimethyldichlorosilane (DDS)-treated glass (DDS-glass) was modified with either poly(ethylene oxide) (PEO) films or poly(N-vinyl-2-pyrrolidone) (PNVP) films by plasma polymerization. The thickness of the plasma polymerized films was varied between 40 and 700 nm. The results showed that the hydrophilic plasma polymerized PEO and PNVP films on DDS-glass did not prevent platelet adhesion and activation. The film thickness had only marginal influence on the prevention of platelet activation. In contrast, platelet adhesion was prevented on DDS-glass adsorbed with a PEO-containing block copolymer (Pluronic® F-108 surfactant) even at a calculated thickness of the PEO layer of less than 40 nm. This study shows that surface hydrophilization is not sufficient for prevention of platelet adhesion and activation. The contrasting results in platelet adhesion between cross-linked plasma polymers and linear PEO-containing block copolymers may be explained qualitatively by a steric repulsion mechanism that is achieved by the conformational freedom of the linear PEO chains interacting with water.     

Investigation of poly(vinyl alcohol)/poly(N-vinyl-2-pyrrolidone) blends, 3. Permeation properties of polymer blend membranes

Dense membranes made of poly(vinyl alcohol) (PVA) and poly(N-vinyl-2-pyrrolidone) (PVP) blends of different compositions were studied in gas-sweeping permeation of a water-ethanol mixture containing 10 wt.-% of water. When the PVP content increases, the steady-state permeation flux and the water content in the permeate show sudden changes at ca. 30–40 wt.-% of PVP in the membrane: the flux increases drastically, while the water selectivity of the membrane falls to a much lower level. The diffusion coefficients of both water and ethanol, as determined from the permeation flux changes in the transient regime, exhibit a large increase when the PVP content exceeds 30 wt.-%, and this accounts for the flux increase. The fall in the permeation selectivity is shown to be due to a strong decrease in the sorption selectivity. The threshold of the change corresponds approximately to the PVP content at which PVA crystallites no longer exist in the blend. A further study on the states of water in the blend membranes by differential scanning calorimetry made it possible to relate these changes with a change in the interactions of water with hydrophilic sites in the polymer blend when the PVP content changes.     

Glass transition temperatures in blends of poly(N-vinyl-2-pyrrolidone) with a copolymer of bisphenol A and epichlorohydrin or with poly(vinyl butyral)

Blends of poly(vinyl butyral) (PVB) and of a copolymer of bisphenol A and epichlorohydrin (Phenoxy) with poly(N-vinyl-2-pyrrolidone) (PVP) were prepared by solution casting. The glass transition temperatures T_g for different compositions of the blends were measured by differential scanning calorimetry (DSC). The T_g behaviour of PVB/PVP blends suggests the existence of a single phase for blends containing less than 50 wt.-% PVP, and of two phases in blends containing more than 50 wt.-% PVP. Phenoxy/PVP blends showed to be miscible over the entire composition range. It was found that the Gordon-Taylor equation predicts adequately the T_g-composition dependence with a K parameter equal to 0,5 and 1,25 for PVB/PVP and Phenoxy/PVP blends, respectively.     

Embolized crospovidone (poly[N-vinyl-2-pyrrolidone]) in the lungs of intravenous drug users.

Crospovidone is an insoluble polymer of N-vinyl-2-pyrrolidone that is used as a disintegrant in pharmaceutical tablets. It can potentially embolize to the lung when aqueous tablet suspensions are injected intravenously. In this report, we identified embolized crospovidone in autopsy-derived lung tissue from three adult IV drug users, 1 man and 2 women, whose ages respectively were 27, 38, and 40 years. Suspected crospovidone was compared with pharmaceutical-grade crospovidone by means of histochemical stains, transmission electron microscopy, and infrared spectroscopy. Similar particles were also observed by light microscopy in a 4-mg tablet of hydromorphone, a preparation prescribed to two of the patients. Two patients had sickle cell disease and were taking methadone and/or hydromorphone for pain management; the third was receiving parenteral hyperalimentation after small bowel resection. Crospovidone appeared as deeply basophilic, coral-like particles within pulmonary arteries and in extravascular foreign-body granulomas. Intrapulmonary crospovidone stained similarly to the pure substance, including intense staining with mucicarmine, Congo red, and Masson trichrome. With Movat pentachrome stain, both intravascular and purified crospovidone appeared orange-yellow, whereas most interstitial particles associated with giant cells stained blue-green. Alcian blue failed to stain intravascular or purified crospovidone but strongly decorated some phagocytized particles. Ultrastructurally, both purified powder and tissue deposits of crospovidone appeared as irregular, electron dense, laminated, and finely granular material. Intrapulmonary crospovidone was associated with inflammatory cells and exhibited degenerative changes. By infrared spectroscopy, crospovidone in tissue had the same spectral characteristics as pharmaceutical grade crospovidone and the library reference, polyvinylpyrrolidone (PVP). We conclude that crospovidone contributes to pulmonary vascular injury in some persons who illicitly inject pharmaceutical tablets. It is readily identifiable histologically and distinguishable from other tablet constituents, such as cornstarch, talc, and microcrystalline cellulose. The variable staining with Alcian blue and Movat suggests that crospovidone is altered in vivo by the inflammatory response.     

Investigations of poly(vinyl alcohol)/poly(N-vinyl-2-pyrrolidone) blends, 2. Influence of the molecular weights of the polymer components on crystallization

Blends of crystallizable poly(vinyl alcohol) (PVA) and poly-(N-vinyl-2-pyrrolidone) (PVP) of different molecular weights were prepared from aqueous solutions by evaporation and studied by Fourier-transform IR spectroscopy. When the molecular weight of one of the polymer components increases, the PVP content at which crystallinity in PVA is no longer observed decreases. The wide band representing hydroxyl stretching splits into four components at welldefined frequencies which are assigned to (1) multiple hydroxyl-hydroxyl bonding in organized PVA regions, (2) hydroxyls which are simply bonded to carboxyl, (3) hydroxyls doubly bonded to two carbonyls or to one carbonyl and one hydroxyl, and (4) simple hydrogen-hydrogen bonding in amorphous PVA regions. When the PVP content increases, the relative intensity of the bond of di-hydrogen-bonded hydroxyls remains quasi-invariant, while that of multiple hydrogen bonds in PVA decreases, and that of simple hydroxyl-carbonyl bonds increases correspondingly. It appears that the higher the molecular weight, the more effective the hindrance of PVP crystallization. An explanation of the mechanism leading to the formation of different structures in the blends is proposed on the basis of these results. It stresses the importance of the role of chain dynamics in an entangled chain network, which greatly affects the kinetics of crystallization of PVA during the drying step.     

Radiation synthesis of poly(N-vinyl-2-pyrrolidone)-kappa-carrageenan hydrogels and their use in wound dressing applications. I. Preliminary laboratory tests

Poly(N-vinyl-2-pyrrolidone)-kappa-carrageenan hydrogels (PVP-KC) were prepared by irradiating the mixtures of aqueous solutions of PVP, KC, potassium chloride, and poly(ethylene glycol) by gamma-rays at different doses. Their preliminary laboratory tests were evaluated to identify their usability in wound dressing applications. For investigation of the effect of components on the gelation of PVP, sol-gel analyses were made and gel fractions of the hydrogels were determined. Mechanical experiments were conducted for both unirradiated and irradiated samples. For investigation of the fluid uptake capacity of the hydrogels, swelling experiments were performed in pseudo-extracellular fluid solution at various temperatures. Acidity/alkalinity (pH) and electrical conductivity tests were achieved from aqueous extracts of hydrogels, and bioadhesion strength of the hydrogels was investigated on human skin.     

Synthesis of water-soluble biologically active phenol (or catechol) containing copolymers of N-vinyl-2-pyrrolidone

Water-soluble N-vinyl-2-pyrrolidone (VP) copolymers containing phenol (or catechol) groups in the side chains were synthesized by reactions of copolymers of VP and crotonic acid (CA) with p-aminophenol and by reaction of p-nitrophenyl ester groups containing VP-CA copolymers with dopamine. It was established that phenol (or catechol) containing multiunit VP copolymers (which were characterized by GPC, viscometry, UV, IR and ¹H NMR spectroscopy) exhibit immunostimulating activity. In addition, the phenol-containing copolymers exhibit antitumor activity. The VP-CA-p-crotonoylaminophenol terpolymer can be used as a macromolecular carrier in the synthesis of a carcinogen-polymer antigen: a polymeric azo derivative of ß-naphthylamine.     

Synthesis and molecular weight characterization of end-functionalized N-vinyl-2-pyrrolidone oligomers

New oligomers of N-vinyl-2-pyrrolidone, functionalized at one end with hydroxy functions, were obtained by radical polymerization in the presence of a hydroxylated compound, namely 2-isopropoxyethanol, acting as chain-transfer agent. The oligomeric samples obtained were characterized in terms of molecular weight and molecular weight distribution by means of analytical size exclusion chromatography (SEC). To this purpose, a calibration curve for a set of SEC columns had been determined, making use of poly(N-vinyl-2-pyrrolidone) standards purposely prepared. The chain transfer constant C_T of 2-isopropoxyethanol towards N-vinyl-2-pyrrolidone was determined from the knowledge of the cumulated number-average degree of polymerization X?_n and monomer conversion Y_t of the samples during the reaction.     

Raman spectroscopic study on water in aqueous solutions of temperature-responsive polymers: Poly(N-isopropylacrylamide) and poly[N-(3-ethoxypropyl)acrylamide]

A Raman spectroscopic study on property changes of water in the course of a temperatureresponsive solution-aggregate transition phenomenon of aqueous poly(N-isopropylacrylamide) and poly[N-(3-ethoxypropyl)acrylamide] solutions was carried out. Upon the transition of polymers from coil to globule followed by the aggregation of individual polymer chains, the height ratio of the the peaks at 3250 and 3 400 cm^?1, corresponding to the O? H stretching of water molecules, was drastically changed. Contribution of small water domains included in polymer aggregates (so-called interstitial water) to the change in the Raman spectra was suggested. Effects of polymer concentration and molecular weight of polymers on the spectra were also examined.     

Release of gentamicin sulphate from a modified commercial bone cement. Effect of (2-hydroxyethyl methacrylate) comonomer and poly(N-vinyl-2-pyrrolidone) additive on release mechanism and kinetics

The influence of the (2-hydroxyethyl methacrylate) (HEMA) monomer addition as a comonomer to the cement liquid component and of a polymer, poly(N-vinyl-2-pyrrolidone) (PVP) to the solid component of a standard CMW-1 bone cement on gentamicin sulphate (GS) on its drug release properties have been studied. The addition of HEMA modifies the habit of the delivery curves. The incorporation of PVP into the cement matrix, apparently, did not very much modify the shape of the HEMA modified cement release curves, but led to a remarkable increase of the maximum amount of GS released. This effect was proportional to the PVP concentration incorporated. From the matrix composition and SEM data, a model based on the morphology of the matrix has been proposed. The cumulative amount of GS released by each slab Mt is most adequately fitted and represented by the equation Mt = c + at 1/2 + b[1 - exp(-nt)], which corroborates that the release occurs according to the model proposed. by means of three discrete mechanisms, namely: (i) a short-term initial elution due to the imperfections in the poly(methyl methacrylate) covering of the most external GS beads, burst effect by the buffer solution; (ii) followed by a fracture by stress cracking in an active media of the coated GS beads located on the external surface of the matrix where water molecules enter to dissolve GS molecules releasing them into the buffer solution by a diffusion-controlled process; and (iii) a third process in which the buffer solution penetrates into the internal voids and cracks creating a series of channels in a labyrinthic structure, which may facilitate the access of water molecules to the plastic-coated GS beads within the bulk matrix. This third process is enhanced by the incorporation of PVP beads as dissolved molecules within the matrix. This water-soluble additive is leachable, generating a highly porous structure in the cement. This HEMA and PVP modified cement may be used as a drug delivery system to modulate the GS release rate.     

Poly(N-vinyl-2-pyrrolidone) elution from polysulfone dialysis membranes by varying solvent and wall shear stress

Some dialysis patients are treated with post-hemodiafiltration (HDF); the blood viscosity of the patients who undergo post-HDF is higher than that of the patients who undergo conventional hemodialysis. This study aims to evaluate poly(N-vinyl-2-pyrrolidone) (PVP) elution from PSf dialysis membranes by varying solvents and high wall shear stress caused by blood viscosity. We tested three commercial membranes: APS-15SA (Asahi Kasei Kuraray), CX-1.6U (Toray) and FX140 (Fresenius). Dialysate and blood sides of the dialyzers were primed with reverse osmosis (RO) water and saline. RO water, saline and dextran solution (2.9 and 5.8 mPa s) were circulated in the blood side. The amount of eluted PVP was determined by 0.02 N iodometry. The hardness and adsorption force of human serum albumin (HSA) on the membrane surfaces were measured by the atomic force microscope. When wall shear stress was increased using dextran, the amount of PVP eluted by the 2.9 mPa s solution equaled that eluted by the 5.8 mPa s solution with APS-15SA and CX-1.6U sterilized by gamma rays. The amount of PVP eluted by the 5.8 mPa s solution was higher than that eluted by the 2.9 mPa s solution with FX140 sterilized by autoclaving. The wall shear stress increased the PVP elution from the surface, hardness and adsorption force of HSA. Sufficient gamma-ray irradiation is effective in decreasing PVP elution.     

Resonance Raman spectroscopic studies on dehydrochlorinated stretched poly(vinyl chloride)

Resonance Raman spectroscopy has been used to assess the effect of streching on the formation of conjugated polyenes during the thermal dehydrochlorination of poly(vinyl chloride). Two samples, a commerical mass polymer and a material prepared at ?30°C, have been examined, unplasticised and plasticised, at different draw ratios. Stretching prior to dehydrochlorination leads to an increase in the length of the polyene sequences, the effect being more marked with the low temperature polymer and with increasing draw ratio. Stretching after dehydrochlorination has no significant effect on the polyene distribution. These observations are consistent with the occurrence of chain orientation and alignment during stretching; this reduces the incidence of cross-linking between polyene sequences in adjacent chains and leads to an increase in the average sequence length.