N-vinyl Pyrrolidinone Research Articles

Synthesis of poly(propylene fumarate)-polyurethane urea composite with kartogenin-modified chitosan for cartilage tissue engineering

In this research, we explored the development of a cross-linked polymer composite, poly(propylene fumarate)-polyurethane urea (PPFUU), designed to foster the differentiation of human adipose-derived mesenchymal stem cells (hADMSCs) into chondrocytes. PPFUU was synthesized using PPF-diol, 1,6-diisocyanatohexane, and putrescin, which served as the soft section, hard section, and chain extender, respectively. To optimize its characteristics, PPFUU was integrated with a chitosan-kartogenin conjugate (CS-KGN) at varying weight fractions. The blend underwent chemical crosslinking via free radical polymerization, with benzoyl peroxide as the initiator and N-vinyl pyrrolidinone as the crosslinking agent. The resulting composites were rigorously analyzed for different properties, including thermal behavior, hydrophilicity, compressive strength, biocompatibility, and more. Significantly, the introduction of CS enhanced glycosaminoglycan formation. Furthermore, hADMSCs, when cultured in chondrogenic media on the CS-KGN-integrated PPFUU composite, exhibited upregulated SOX9 and aggrecan expression. Based on these in vitro results, the CS-KGN-conjugated PPFUU composite presents a promising avenue for cartilage tissue regeneration.

Tuning Hydrogel Adhesivity and Degradability to Model the Influence of Premetastatic Niche Matrix Properties on Breast Cancer Dormancy and Reactivation.

Dormant, disseminated tumor cells (DTCs) can persist for decades in secondary tissues before being reactivated to form tumors. The properties of the premetastatic niche can influence the DTC phenotype. To better understand how matrix properties of premetastatic niches influence DTC behavior, three hydrogel formulations are implemented to model a permissive niche and two nonpermissive niches. Poly(ethylene glycol) (PEG)-based hydrogels with varying adhesivity ([RGDS]) and degradability ([N-vinyl pyrrolidinone]) are implemented to mimic a permissive niche with high adhesivity and degradability and two nonpermissive niches, one with moderate adhesivity and degradability and one with no adhesivity and high degradability. The influence of matrix properties on estrogen receptor positive (ER+ ) breast cancer cells (MCF7s) is determined via a multimetric analysis. MCF7s cultured in the permissive niche adopted a growth state, while those in the nonpermissive niche with reduced adhesivity and degradability underwent tumor mass dormancy. Complete removal of adhesivity while maintaining high degradability induced single cell dormancy. The ability to mimic reactivation of dormant cells through a dynamic increase in [RGDS] is also demonstrated. This platform provides the capability of inducing growth, dormancy, and reactivation of ER+ breast cancer and can be useful in understanding how premetastatic niche properties influence cancer cell fate.

Reactivity of Phosphino‐naphtholate Nickel Complexes and Their Catalysis of Copolymerization with Polar Monomers

AbstractCoordination‐insertion copolymerization of ethylene with polar monomers can directly provide value‐added functionalized polyolefins. Studies on the reactivity of catalysts toward polar monomers can help understand the copolymerization process and then tune the polymerization strategically. In this contribution, the reactivity picture of 2‐diphenylphosphonyl‐8‐phenylnaphthol nickel complex toward fundamental polar monomers was explored by stoichiometric reactions. The insertion rates are in the order of methyl acrylate (MA)>n‐butyl acrylate (BA)>N, N‐dimethylacrylamide (DMAA)>methyl methacrylate (MMA)>vinyl triethoxysilane (VTEoS)>N‐vinyl‐pyrrolidinone (NVP). Acrylic derivatives of MA, BA and DMAA with electron‐withdrawing group favor 2,1‐fashion while non‐acrylic NVP with electron‐donating group prefers 1,2‐fashion. Notably, the 1,1‐disubstituted MMA and bulky VTEoS perform a preferential 1,2‐insertion accompanying by 2,1‐insertion in the percentage of 82 : 18 and 62 : 38, respectively, because of the stronger steric effect. These insights correlate to the copolymerization of polar monomers with ethylene. Linear functional polyethylene with in‐chain and terminal incorporation of BA, DMAA or VTEoS is afforded at a high activity.

Synthesis of methacrylate pendant polyelectrolyte as water-soluble multifunctional cross-linker

A new cationic polyelectrolyte, constituting with quaternary poly(4-vinyl pyridine) (PVPy) backbone and methacrylate pendant groups was prepared by spontaneous polymerization methodology. Thus, action of 2-bromoethyl methacrylate (BEMA) on 4-vinyl pyridine resulted in spontaneous polymerization of vinyl pyridine monomer, without initiator, while methacrylate double bonds remaining unreacted. The resulting water-soluble polymer (QMEP); poly(2-methacryloyloxyethyl 4-vinyl pyridinium bromide) was demonstrated to undergo rapid gelation in concentrated aqueous solutions via self-crosslinking of the methacrylate pendant groups by radical polymerization (The abbreviation QMEP stands for quaternary methacrylate functional polymer). Crosslinking densities of QMEP hydrogels estimated by “Phantom Network Model” using equilibrium swelling values, revealed 62.5% of the residual methacrylate double bonds. QMEP was also employed as multifunctional crosslinker for synthesis of highly swelling hydrogels derived from a set of monomers, such as acrylic acid, acrylamide, N-vinyl formamide and N-vinyl pyrrolidinone.

Preparation and characterization of protein-resistant hydrogels for soft contact lens applications via radical copolymerization involving a zwitterionic sulfobetaine comonomer

We aimed to introduce hydrophilic sulfobetaine-type zwitterionic groups to macromolecular chains of copolymers to construct novel copolymer hydrogels with anti-protein-fouling performance that could be used as soft contact lens (SCL) materials. Using hydroxyethyl methacrylate (HEMA), N-vinyl pyrrolidinone (NVP) and sulfobetaine methacrylate (SBMA) as comonomers, several copolymer hydrogels with different SBMA contents, poly(HEMA-NVP-SBMA), are synthesized via radical copolymerization in an aqueous phase. Surface chemistry, structural morphologies, water contact angle (WCA), equilibrium water content (EWC), visible light transmittance and tensile mechanical properties are investigated. The prepared hydrogels exhibit a closed-type porous structure. With increasing SBMA content in the comonomer mixture, the prepared copolymer hydrogel pore size gradually increases up to the micron level, WCA tends to decrease, EWC tends to increase, and visible light transmittance slightly increases, but their tensile mechanical properties decline. The amounts of protein Lyz and BSA adsorbed on the copolymer hydrogels and on commercially available EASY DAY® SCLs as a control are also determined by protein adsorption tests. The amount of protein adsorbed on the copolymer hydrogel decreases with increasing SBMA content. For the hydrogel prepared using the comonomer mixture with 5.0 wt % SBMA, the amount of adsorbed Lyz is 0.91 μg/cm2, which corresponds to only 56.8% of the amount adsorbed on EASY DAY® SCLs. Thus, novel SCL materials with high water content and excellent anti-protein-fouling performance were efficiently constructed by introducing sulfobetaine-type zwitterionic groups into a traditional polymer hydrogel system.

Poly(N-vinylpyrrolidinone) microgels: preparation, biocompatibility, and potential application as drug carriers.

The biocompatible poly(N-vinylpyrrolidinone) (PNVP) microgels were synthesized via surfactant free emulsion polymerization with N-vinylpyrrolidinone (NVP) as the monomer and ethylene glycol dimethacrylate (EGDMA) as the cross-linker at 60 °C. The obtained PNVP microgels are spherical in shape with hydrodynamic diameter of approximately 200 nm and narrow size distribution. The PNVP microgels show rough surfaces due to the different reaction rates of monomer NVP and cross-linker EGDMA. The obtained PNVP microgels could well disperse in phosphate-buffered saline (PBS) solution with long-term stability, which make them candidates for bioapplications. The results of 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide (MTT) tests indicated that the PNVP microgels are biocompatible with low toxicity even at a concentration of 1000 μg/mL. By labeling the PNVP microgels with fluorescein comonomer, it was demonstrated that the PNVP microgels could be uptaken by human embryonic kidney 293 (HEK-293) cells. The experimental results indicated that the release of isoniazid (INH, the hydrophilic model drug) could be well described by a Fickian release, whereas the microgels exhibited burst release for 5-fluorouracil (5-fu, the hydrophobic model drug).

A Robust and Versatile Photoinduced Living Polymerization of Conjugated and Unconjugated Monomers and Its Oxygen Tolerance

Controlled/living radical polymerization techniques have transformed polymer chemistry in the last few decades, affording the production of polymers with precise control over both molecular weights and architectures. It is now possible to synthesize almost an infinite variety of macromolecules using nonspecialized equipment, finding applications in high-tech industry. However, they have several shortcomings. Until recently, living radical polymerizations could not be controlled by an external stimulus, such as visible light, pH, mechanical, chemical, etc. Moreover, they are usually sensitive to trace amounts of oxygen in the system. In this Article, we report a photoinduced living polymerization technique, which is able to polymerize a large range of monomers, including conjugated and unconjugated monomers, using ultralow concentrations of an iridium-based photoredox catalyst (typically 1 ppm to monomers) and a low energy visible LED as the light source (1-4.8 W, λ(max) = 435 nm). The synthesis of homopolymers with molecular weights ranging from 1000 to 2,000,000 g/mol was successfully achieved with narrow molecular weight distributions (M(w)/M(n) < 1.3). In addition, chain extensions of poly(methacrylate)s, poly(styrene), poly(N-vinyl pyrrolidinone), poly(vinyl ester)s, and poly(acrylate)s were performed to prepare diblock copolymers. The reusability of the catalyst was demonstrated by the synthesis of a decablock polymer by multiple chain extensions. Most importantly, this process was employed to prepare well-defined polymers and multiblock copolymers in the presence of air.

Glucomannan-poly(N-vinyl pyrrolidinone) bicomponent hydrogels for wound healing

Polysaccharides interact with cells in ways that can be conducive to wound healing. We have recently reported that konjac glucomannan (KGM) which is comprised of d-mannose and d-glucose linked by β-1,4 glycosidic chains, stimulates fibroblast proliferation. The aim of this study was to produce a range of crosslinked KGMs and bicomponent KGM containing hydrogels and to examine their potential for wound healing. Two types of KGM hydrogel were synthesized, biodegradable from crosslinked KGM and non-biodegradable by forming semi-IPNs and graft-conetworks with a second synthetic component, poly(N-vinyl pyrrolidinone-co-poly(ethyleneglycol)diacrylate) (P(NVP-co-PEGDA)), which was produced by UV initiated radical polymerization. Crosslinked KGM was formed by bimolecular termination of macro-radicals formed by oxidation with Ce(iv). Semi-IPNs were formed by copolymerization of NVP and PEGDA in the presence of KGM and in the graft-conetworks the KGM was also crosslinked using the Ce(iv) procedure. The hydrogels had different swelling properties and differences could be observed in their chemical structure using 13C solid state NMR, DSC and FTIR. Both forms were cytocompatible but only the graft-conetworks had the ability to stimulate fibroblast metabolic activity and to stimulate the migration of both fibroblasts and keratinocytes. In conclusion a form of KGM hydrogel has been produced that could benefit wound healing.

In Vitro Studies of Composite Bone Filler Based on Poly(Propylene Fumarate) and Biphasic α-Tricalcium Phosphate/Hydroxyapatite Ceramic Powder

While many different filler materials have been applied in vertebral augmentation procedures, none is perfect in all biomechanical and biological characteristics. To minimize possible shortages, we synthesized a new biodegradable, injectable, and premixed composite made from poly(propylene fumarate) (PPF) and biphasic α-tricalcium phosphate (α-TCP)/hydroxyapatite (HAP) ceramics powder and evaluated the material properties of the compound in vitro. We mixed the PPF cross-linked by N-vinyl pyrrolidinone and biphasic α-TCP/HAP powder in different ratios with benzoyl peroxide as an initiator. The setting time and temperature were recorded, although they could be manipulated by modulating the concentrations of hydroquinone and N,N-dimethyl-p-toluidine. Degradation, cytocompatibility, mechanical properties, and radiopacity were analyzed after the composites were cured by a cylindrical shape. We also compared the study materials with poly(methyl methacrylate) (PMMA) and PPF with pure HAP particles. Results showed that lower temperature during curing process (38-44°C), sufficient initial mechanical compressive fracture strength (61.1±3.7MPa), and gradual degradation were observed in the newly developed bone filler. Radiopacity in Hounsfield units was similar to PMMA as determined by computed tomography scan. Both pH value variation and cytotoxicity were within biological tolerable limits based on the biocompatibility tests. Mixtures with 70% α-TCP/HAP powder were superior to other groups. This study indicated that a composite of PPF and biphasic α-TCP/HAP powder is a promising, premixed, injectable biodegradable filler and that a mixture containing 70% α-TCP/HAP exhibits the best properties.

Modification of polyethersulfone membrane by blending semi-interpenetrating network polymeric nanoparticles

The present methodology provides a simple approach to prepare semi-interpenetrating network (semi-IPN) polymeric nanoparticles for the modification of polyethersulfone (PES) membranes. The PES/poly (N-vinyl pyrrolidinone) (PVP) semi-IPN nanoparticles were synthesized by cross-linking VP on PES chains via solution polymerization; the size of the nanoparticles ranged from 38 to 820 nm determined by dynamic light scattering (DLS), scanning electron microscope (SEM) and transmission electron microscope (TEM). The polymeric nanoparticles could be directly used to prepare membranes, and the membranes were characterized by SEM, elemental analysis etc. The water contact angles of the PES membranes decreased from 74° to 53°, and the adsorbed protein amount decreased from 9.5 μg/cm 2 to 0.7 μg/cm 2; meanwhile the water flux and protein anti-fouling property of the membranes increased significantly. The activated partial thrombin time (APTT) of the modified membrane was prolonged. All these results indicated the hydrophilicity and the blood compatibility of the modified PES membranes were improved.

Ameliorating Soil Sodicity Using Calcium Salt Incorporated Hydrogels

The potential of using hydrogels encapsulated with a water-soluble calcium salt, Ca(NO3)2 for the remediation and management of sodic soil, a degenerate soil condition associated with irrigation of recycled water was investigated. Environmentally friendly hydrogel, poly(2-hydroxyethyl methacrylate) (PHEMA) was synthesised from the monomer, 2-hydroxyethyl methacrylate (HEMA). HEMA was also used to copolymerise with another monomer, N-vinyl pyrrolidinone (NVP) to form a more hydrophlic hydrogel. Starch and glucose were incorporated in certain hydrogels with the intention of evaluating their biodegradability in soils since starch and glucose would serve as nutrients for microbials in soils. Delivery of calcium ions embedded in hydrogels were investigated on sodic and non-sodic clay loam under saturated condition. It was found that the optimum hydrogel for this application was the copolymer that contained HEMA and NVP in equal mole ratio.

Effects of Composite Formulation on Mechanical Properties of Biodegradable Poly(Propylene Fumarate)/Bone Fiber Scaffolds

The objective of our study was to determine the effects of composite formulation on the compressive modulus and ultimate strength of a biodegradable, in situ polymerizable poly(propylene fumarate) (PPF) and bone fiber scaffold. The following parameters were investigated: the incorporation of bone fibers (either mineralized or demineralized), PPF molecular weight, N-vinyl pyrrolidinone (NVP) crosslinker amount, benzoyl peroxide (BP) initiator amount, and sodium chloride porogen amount. Eight formulations were chosen based on a resolution III two level fractional factorial design. The compressive modulus and ultimate strength of these formulations were measured on a materials testing machine. Absolute values for compressive modulus varied from 21.3 to 271 MPa and 2.8 to 358 MPa for dry and wet samples, respectively. The ultimate strength of the crosslinked composites varied from 2.1 to 20.3 MPa for dry samples and from 0.4 to 16.6 MPa for wet samples. Main effects of each parameter on the measured property were calculated. The incorporation of mineralized bone fibers and an increase in PPF molecular weight resulted in higher compressive modulus and ultimate strength. Both mechanical properties also increased as the amount of benzoyl peroxide increased or the NVP amount decreased in the formulation. Sodium chloride had a dominating effect on the increase of mechanical properties in dry samples but showed little effects in wet samples. Demineralization of bone fibers led to a decrease in the compressive modulus and ultimate strength. Our results suggest that bone fibers are appropriate as structural enforcement components in PPF scaffolds. The desired orthopaedic PPF scaffold might be obtained by changing a variety of composite formulation parameters.

Vitamin B12 diffusion and binding in crosslinked poly(acrylic acid)s and poly(acrylic acid-co- N-vinyl pyrrolidinone)s

The diffusion mechanism of vitamin B12 in two types of crosslinked hydrogels, poly(acrylic acid) (cPAA) and copolymers of acrylic acid and N-vinyl pyrrolidinone (cP(AA-NVP)) was studied. The PAA and P(AA-NVP) synthesized by three different degrees of crosslinking have limited water absorption capabilities ranging from 3% to 18%. In the copolymers permeability of B12 is controlled by both intramolecular and intermolecular hydrogen-bonding between the pyrrolidinone and carboxylic acid side chains. The diffusion kinetic data in two types of polymers were best described by Peppas models instead of Higuchi models. Permeation from both crosslinked PAA and P(AA-co-NVP) copolymers followed a Super Case II transport mechanism, most likely driven by macromolecular chain relaxation and swelling of hydrophilic polymers. A special FTIR spectroscopic method for drug binding study, FTIR difference spectroscopy, is used to probe the strong interactions between vitamin B12 and the side chains of the hydrogels. The FTIR differential spectra of B12 in PAA hydrogels revealed dramatic changes of the spectral marker bands of B12 after binding in the crosslinked gels, indicating significant interactions occurring in the amide and phosphate moieties of B12. Such interactions retard the diffusion of vitamin B12.

Crosslinking property of an oligomeric unsaturated phosphoester used as a potential injectable biomaterial

An unsaturated polyphosphoester (UPPE) that has double bonds in repeatable units could crosslink with a vinyl monomer. A study of how the crosslinking temperature, setting time and mechanical properties are affected by the UPPE molecular weight, N-vinyl pyrrolidinone (NVP)/UPPE ratio and benzoyl peroxide (BPO)/UPPE ratio was conducted. The results of the study indicated that the maximum crosslinking temperature is between 41.1 °C and 82.3 °C, which is lower than the 97 °C of poly(methyl methacrylate) bone cement. The BPO concentration strongly affected the maximum temperature and setting time. High concentration of BPO gives a rapid polymerization rate, causing reaction heat to be released immediately. The compressive strength and compressive modulus will be enhanced with an increase in the NVP/UPPE ratio, the UPPE molecular weight and the BPO concentration. For all formulations, the compressive strength values are between 3.3 MPa and 11.0 MPa and the compressive modulus values are between 4.9 MPa and 101.9 MPa. These initial studies suggest that UPPE is one kind of potential injectable bone tissue engineering scaffold material.

Hydrolysis-induced aqueous gelcasting for near-net shape forming of ZTA ceramic composites

A new near-net shape forming process called “hydrolysis-induced aqueous gelcasting” (GCHAS) is reported in this paper for the consolidation of ZTA composites, ZTA-30 (70 wt.% Al 2O 3 + 30 wt.% ZrO 2) and ZTA-60 (40 wt.% Al 2O 3 + 60 wt.% ZrO 2). For comparison purposes, ceramics having the same chemical compositions were also consolidated by hydrolysis-assisted solidification (HAS). All the starting suspensions contained a solids loading of 50 vol.%. In the precursor powder mixtures, 1–5 wt.% of Al 2O 3 was replaced by equivalent amounts of AlN to enhance or promote or co-promote the consolidation of suspensions by HAS or by GCHAS, respectively. The suspensions for GCHAS were prepared by dispersing the ZTA powder precursor mixtures in a premix solution of 20 wt.% MAM (methacrylamide), MBAM (methylenebisacrylamide) and NVP ( n-vinylpyrrolidinone) in 3:1:3 ratio in de-ionized water. Ceramics consolidated via GCHAS exhibited superior mechanical properties after consolidation and after sintering for 1 h at 1600 °C in comparison to those consolidated by HAS.

Poly(propylene fumarate)/(calcium sulphate/β-tricalcium phosphate) composites: Preparation, characterization and in vitro degradation

This study aimed to prepare a poly(propylene fumarate)/(calcium sulphate/β-tricalcium phosphate) (PPF/(CaSO4/β-TCP)) composite. We first examined the effects of varying the molecular weight of PPF and the N-vinyl pyrrolidinone (NVP) to PPF ratio on the maximum cross-linking temperature and the composite compressive strength and modulus. Then the in vitro biodegradation behaviour of PPF/(CaSO4/β-TCP) composites was investigated. The effects of varying the molecular weight of PPF, the NVP/PPF ratio and the CaSO4/β-TCP molar ratio on the weight loss and the composite compressive strength and modulus were examined. The cross-linking temperature, which increased with increasing molecular weight of PPF and NVP/PPF ratio, ranged from 41 to 43°C for all formulations. The mechanical properties were increased by a decrease in the NVP/PPF ratio. For all formulations, the compressive strength values fell between 12 and 62MPa, while the compressive modulus values fell between 290 and 1149MPa. The weight loss decreased either with increasing molecular weight of PPF or with decreasing NVP/PPF ratio and CaSO4/β-TCP molar ratio during degradation. The compressive strength and modulus increased with decreasing NVP/PPF ratio or decreasing CaSO4/β-TCP ratio. The greatest weight loss over 6 weeks was 14.72%. For all formulations, the compressive modulus values fell between 57 and 712MPa and the compressive strength fell between 0.5 and 21MPa throughout 6 weeks degradation. Scanning electron microscopy and X-ray diffraction analysis of the PPF/(CaSO4/β-TCP) composites demonstrated that hydroxyapatite was deposited on the surface of CaSO4/β-TCP granules during degradation.

NMR and Texture Analyses in Relation to Swelling Kinetics of 2‐Hydroxyethyl Methacrylate/N‐Vinylpyrrolidinone Hydrogels

AbstractThis study investigates the relationship between swelling kinetics and the relative stress relaxation (SR) values from texture analysis, as well as the relaxation times from proton NMR analysis of photopolymerized 2‐hydroxyethyl methacrylate (HEMA)/N‐vinyl pyrrolidinone (NVP) hydrogels with varying HEMA and NVP contents. Swelling tests in Milli‐Q water at 37 °C showed that hydrogels of higher NVP content displayed non‐Fickian diffusion kinetics. Texture analysis indicated the existence of a trend between SR values and diffusion kinetics with the hydrogels that displayed non‐Fickian diffusion having significantly lower SR values. Proton NMR analysis showed that the hydrogel with higher NVP content (non‐Fickian diffusion kinetics) displayed substantially longer relaxation times, which indicated slower exchange of water molecules between different sites within the meshes of the polymer matrix, attributable probably to hydrogen bonding and hydrophilic attraction between polymer and the water molecules. A relationship appeared to exist for the hydrogels understudy with hydrogels exhibiting non‐Fickian diffusion kinetics displaying lower SR values and longer relaxation times.

Vascular endothelial growth factor and dexamethasone release from nonfouling sensor coatings affect the foreign body response

Vascular endothelial growth factor (VEGF) and dexamethasone (DX) release from hydrogel coatings were examined as a means to modify tissue inflammation and induce angiogenesis. Antibiofouling hydrogels for implantable glucose sensor coatings were prepared from 2-hydroxyethyl methacrylate, N-vinyl pyrrolidinone, and polyethylene glycol. Microdialysis sampling was used to test the effect of the hydrogel coating on glucose recovery. VEGF-releasing hydrogel-coated fibers increased vascularity and inflammation in the surrounding tissue after 2 weeks of implantation compared to hydrogel-coated fibers. DX-releasing hydrogel-coated fibers reduced inflammation compared to hydrogel-coated fibers and had reduced capsule vascularity compared to VEGF-releasing hydrogel-coated fibers. Hydrogels that released both VEGF and DX simultaneously also showed reduced inflammation at 2 weeks implantation; however, no enhanced vessel formation was observed indicating that the DX diminished the VEGF effect. At 6 weeks, there were no detectable differences between drug-releasing hydrogel-coated fibers and control fibers. From this study, hydrogel drug release affected initial events of the foreign body response with DX inhibiting VEGF, but once the drug depot was exhausted these effects disappeared.

The influence of N-vinyl-2-pyrrolidinone in polymerization of holographic polymer dispersed liquid crystals (HPDLCs)

Holographic polymer dispersed liquid crystals (HPDLCs) are targeted for application in a wide range of devices as dynamically switchable transmission or reflection diffraction gratings tunable through the visible spectra. The inclusion of N-vinyl pyrrolidinone (NVP) has been shown to reduce liquid crystal (LC) droplet size in HPDLC gratings and subsequently improve HPDLC performance. In this work, the influence of NVP on HPDLC polymer/LC morphology is examined and correlated to the influence of NVP on HPDLC photopolymerization kinetics and LC phase separation. As in other photopolymer systems, NVP significantly increases the rate of polymerization in HPDLC photopolymerization. In all the HPDLC formulations studied, NVP is completely incorporated into the polymer network while less than half of acrylate double bonds react. Furthermore, as the highly cross-linked polymer network forms, the small mono-vinyl NVP appears to react preferentially with acrylate double bonds, facilitating additional conversion of pendant double bonds otherwise trapped in the polymer network. NVP also induces a delay in the onset of reaction diffusion termination and extends the range of conversions for which reaction diffusion is observed. Interestingly, NVP also impacts polymer/LC morphology by delaying LC phase separation to higher double bond conversions. Together, the influence of NVP on the polymerization kinetics and LC phase separation alters HPDLC morphology by limiting LC droplet size, consequently resulting in improved HPDLC performance.

Pervaporation properties of polypyrrolidinone‐based membranes for EtOH/ETBE mixtures separation

AbstractThe separation of ethanol/ethyl‐tertiobutylether mixtures by pervaporation was studied with new membranes prepared from N‐vinyl‐pyrrolidinone (NVP) and N‐[3‐(trimethylamoniopropyl)]methacrylamidemethylsulfate) (TMA). The pervaporation results showed that highly EtOH selective membranes could be obtained from PVP blends and from pyrrolidinone‐based crosslinked copolymers. The influences of the polymer blend composition and the role of the polymer microstructures on the membrane properties were investigated. Whatever the exact NVP/TMA composition used, the membranes strongly favored the pervaporation of ethanol. The ethanol selectivity was higher for the lower PVP/TMA ratio. On the one hand, these results were ascribed to the high pyrrolidinone residues content, which is responsible of the enhanced EtOH sorption affinity. The observed permeation selectivity was in agreement with the swelling data also recorded with the different polymers, showing higher affinity for ethanol with PVP‐enriched materials compared with TMA ones. This is a direct consequence of the Lewis base feature of pyrrolidinone sites towards EtOH molecules. On the other hand, the TMA residues improved the overall stability and selectivity of the membranes thanks to crosslinking reactions, which were induced by thermal treatment. A close comparison made between polymer blend and copolymer pervaporation results helped to clarify the TMA role of the membrane transport properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99:3622–3630, 2006