Tough Semi-interpenetrating Polyvinylpyrrolidone/Polyacrylamide Hydrogels Enabled by Bioinspired Hydrogen-bonding Induced Phase Separation

Semi-interpenetrating(semi-IPN)hydrogels formed by the continuous interpenetration of cross-linked polymer network and linear non-crosslinked polymer with multifunctionality are widely used in biomedical and other fields.However,the negative impact of linear polymer on the homogeneity of the cross-linked network often leads to a decrease in the mechanical properties of semi-IPN hydrogels and severely limits their applications.Herein,a bioinspired hydrogen-bonding induced phase separation strategy is presented to construct the tough semi-IPN polyvinylpyrrolidone/polyacrylamide hydrogels(named PVP/PAM hydrogels),including the linear polymer polyvinylpyrrolidone(PVP)and cross-linked polyacrylamide(PAM)network.The resultant PVPx/PAM hydrogels exhibit unique phase separation induced by the hydrogen bonding between PVP and PAM and affected by the amount of substance of PVP.Meanwhile,the phase separation of PVPx/PAM hydrogels results in excellent mechanical properties with a strain of 2590%,tensile strength of 0.28 MPa and toughness of 2.17 MJ/m^(3).More importantly,the hydrogen bonding between PVP and PAM firstly disrupts to dissipate energy under external forces,so the PVPx/PAM hydrogels exhibit good self-recovery properties and outperform chemically cross-linked PAM hydrogels in impact resistance and damping applications.It is believed that the PVPx/PAM hydrogels with hydrogen-bonding induced phase separation possess more potential application prospects.

Polyvinylpyrrolidone-based bioink:influence of bioink properties on printing performance and cell proliferation during inkjet-based bioprinting

Among the different bioprinting techniques,the drop-on-demand(DOD)jetting-based bioprinting approach facilitates contactless deposition of pico/nanoliter droplets ofmaterials and cells for optimal cell–matrix and cell–cell interactions.Although bioinks play a critical role in the bioprinting process,there is a poor understanding of the influence of bioink properties on printing performance(such as filament elongation,formation of satellite droplets,and droplet splashing)and cell health(cell viability and proliferation)during the DOD jetting-based bioprinting process.An inert polyvinylpyrrolidone(PVP360,molecular weight=360 kDa)polymerwas used in this study to manipulate the physical properties of the bioinks and investigate the influence of bioink properties on printing performance and cell health.Our experimental results showed that a higher bioink viscoelasticity helps to stabilize droplet filaments before rupturing from the nozzle orifice.The highly stretched droplet filament resulted in the formation of highly aligned“satellite droplets,”which minimized the displacement of the satellite droplets away from the predefined positions.Next,a significant increase in the bioink viscosity facilitated droplet deposition on the wetted substrate surface in the absence of splashing and significantly improved the accuracy of the deposited main droplet.Further analysis showed that cell-laden bioinks with higher viscosity exhibited higher measured average cell viability(%),as the presence of polymer within the printed droplets provides an additional cushioning effect(higher energy dissipation)for the encapsulated cells during droplet impact on the substrate surface,improves the measured average cell viability even at higher droplet impact velocity and retains the proliferation capability of the printed cells.Understanding the influence of bioink properties(e.g.,bioink viscoelasticity and viscosity)on printing performance and cell proliferation is important for the formulation of new bioinks,and we have demonstrated precise DOD deposition of living cells and fabrication of tunable cell spheroids(nL–μL range)using multiple types of cells in a facile manner.

Oxidation of Partially Hydrolyzed Polyacrylamide from Polymer Flooding Processes Using Fenton Reagents

The degradation of partially hydrolyzed polyacrylamide(HPAM) found in alkaline/surfactant/polymer flooding sewage was investigated using Fenton-type reagents. Different Fenton reagent treatments for HPAM degradation were compared. The effects of pH, hydrogen peroxide(H_(2)O_(2)), ferrous ion(Fe^(2+)), and tartaric ion(C_(4)H_(4)O_(6)^(2-)) concentrations were studied. The degradation reaction occurred within a wide range of pH(3–9). The HPAM degradation performance of photo-Fenton processes using solar light and UV were compared with that of the Fenton process. The degradation rate was found to be strongly dependent on the H_(2)O_(2)/Fe^(2+)/C_(4)H_(4)O_(6)^(2-)molar ratio. The HPAM degradation efficiency was 90%, and the chemical oxygen demand removal efficiency was 85%. HPAM could be degraded into a compound with a lower molecular weight, but it was difficult to achieve complete mineralization to CO_(2). The presence of intermediate products hindered further oxidation in the Fenton process.

A review of complications of polyacrylamide hydrogel injection

Once a popular injectable filler,polyacrylamide hydrogel(PAAG)has been banned in China since 2006 due to its unclear safety and long-term complications.However,it is still being used worldwide because of its huge commercial profit,leading to emerging complications and an urgent need for standardized clinical management.This review aimed to assess the properties,safety,and complications of PAAG and treatment strategies for its removal.

Synthesis and Flocculation of Polyacrylamide with Low Water Absorption for Non-dispersible Underwater Concrete

The polyacrylamide which is directly added into concrete shows strong water absorption property.Thus the construction of underwater constructure would demand high amount of water,resulting in poor workability of concrete and strength shrinkage after hardening.Herein,a kind of anionic polyacrylamide(APAM)grafted with water reducing functional group(-COOH)was synthesized at low temperatures by partial factor design and response surface design.The structure and morphology of APAM were characterized by UV,FTIR and SEM methods.The experimental results show that the molecular weight of the synthesized APAM could reach 11 million,under the condition that the temperature was 35℃,the pH value was 8,the monomer concentration was 27wt%,the initiator dosage was 0.6wt%,and the monomer ratio(n(AM):n(AA))was 3.When the APAM was applied into the underwater slurry,it presented good flocculation and low water demand.When the dosage was 1%of the mass of the cement,the water demand increased by 12%,which could meet the self-leveling and anti-dispersity of the underwater slurry at the same time.This technology provides technical guidance for the large-scale industrial production of polyacrylamide for underwater concrete construction while achieving environmental protection during production.

Selective removal of Cr(Ⅵ)using polyvinylpyrrolidone and polyacrylamide co-modified MoS_(2) ccomposites by adsorption combined with reduction

Cr(Ⅵ),one of the most hazardous metal pollutants,poses significant threats to the environment and human health.Herein,a novel MoS_(2) composite(MoS_(2)/PVP/PAM)modified by polyvinylpyrrolidone(PVP)and polyacrylamide(PAM)was synthesized to enhance the removal of Cr(Ⅵ).Characterization analysis including SEM,XRD,FTIR,and XPS indicated that PVP and PAM could increase the interlayer spacing and the dispersibility of MoS_(2),and introduce pyrrolic N and amino functional groups.The batch experiments showed that MoS_(2)/PVP/PAM represented excellent Cr(Ⅵ)removal performance over a wide p H range,and exhibited a significantly higher maximum Cr(Ⅵ)adsorption capacity(274.73 mg/g,at p H 3.0,and 298 K)than pure MoS_(2).The adsorption of Cr(Ⅵ)followed Langmuir and pseudo-second-order kinetic model,which was a homogeneous monolayer chemisorption process.MoS_(2)/PVP/PAM showed stable removal of Cr(Ⅵ)in the presence of humic acid(HA),interfering cations and anions at different concentrations.Moreover,it had excellent selectivity for Cr(Ⅵ)(K_(d) value of 1.69×10^(7)m L/g)when coexisting with a variety of competing ions.Multiple characterization revealed that Cr(Ⅵ)was reduced to low toxicity Cr(Ⅲ)by Mo^(4+)and S^(2-),and then chelated on the surface of the adsorbent by pyrrolic N.This research expanded the design concept for MoS_(2) composites by demonstrating the potential of MoS_(2)/PVP/PAM as a promising material for selective elimination of Cr(Ⅵ)in water.

Study on the Effects of Polyacrylamide on Phosphorus Adsorption and Desorption Characteristics of Soil Aggregates

[Objective]The research aimed to provide scientific reference for reasonable utilization of polyacrylamide(PAM).[Method]After PAM treatment,the soil aggregates were classified through dry sieve analysis and the adsorption capacity and desorption capacity of all soil aggregates to phosphorus at different phosphorus concentrations were analyzed.[Result] The phosphorus adsorption and desorption of soil sample treated by PAM declined. The amount of phosphorus adsorption increased with the increase of phosphorus concentration and this increase was fast in low phosphorus concentration area but slow in high phosphorus concentration area.At different phosphorus concentrations,adsorption showed a へ shape changing trend.The phosphorus adsorption was related to phosphorus concentration and the 2-3 mm aggregate had the highest desorption rate while 0.1-0.25 mm aggregate and 0.45-1 mm aggregate had lowest desorption rate.[Conclusion]The PAM treatment generated significant influence on phosphorus adsorption and analytic features of aggregate in all size fractions.

Preparation,physicochemical characterization and cyctotoxicity of solid dispersion of paclitaxel and polyvinylpyrrolidone

The objective of this study was to prepare and characterize paclitaxel-polyvinylpyrrolidone （PTX-PVP） solid dispersions with the intention of improving its solubility and dissolution properties. The PTX-PVP solid dispersion systems were prepared by solvent method. The release rate ofpaclitaxel was determined from dissolution studies and the physicochemical properties of solid dispersion were investigated by differential scanning calorimetry （DSC）, powder X-ray diffraction （PXRD） and scanning electron microscopy （SEM）. The cytotoxicities ofpaclitaxel in solid dispersion to the SKOV-3 cells were assayed by a SRB staining method. The results showed that the solubility and dissolution rate of paclitaxel were significantly improved in solid dispersion system compared with that of the pure drug and physical mixture. The results of DSC and PXRD showed that the paclitaxel in solid dispersion was amorphous form. No paclitaxel crystals in the solid dispersions was found during SEM analysis. Cytotoxicity study suggested that the inhibitory rates of PTX-PVP solid dispersion to SKOV-3 cells were higher than that of pure paclitaxel. The solubility and dissolution of paclitaxel were improved by solid dispersion technique. In vitro cytotoxicity of paclitaxel in solid dispersion was higher than that of pure drug.

Improvement of Polyacrylamide Gel Electrophorus in Phytophthora infeatans SSR Marker

[Objective] The paper was to improve polyacrylamide gel electrophorus in Phytophthora infeatans SSR Marker.[Method] With the disease sample of P.infeatans collected from Guyuan in Ningxia Province in 2009 as test material,its DNA was extracted and amplified with PCR,and its products were carried out polyacrylamide gel electrophoresis.[Result] 12% polyacrylamide gel electrophoresis was used to detect primers D13,G11 and PI02,and 8% polyacrylamide gel electrophoresis was used to detect primers PI4B,PI63,SSR4,SSR8 and SSR11,then 0.1% silver nitrate was used to stain,and an ideal electrophoresis and staining effect was obtained.[Conclusion] The electrophoresis and staining method suitable for P.infeatans SSR Marker established in the study had the characteristics of high sensitivity,simple operation and clear bands,which was an effective,simple and quick detection method.

Optimization of SSR-PCR Non-denatured Polyacrylamide Gel Electrophoresis Conditions in Kernelled Apricot

[Objective] The aim was to optimize the SSR-PCR non-denatured polyacrylamide gel electrophoresis conditions in kernelled apricot.[Method]25 accessions of kernelled apricot and three accessions of edible apricot were selected as experimental materials to screen the repeatable SSR loci with high polymorphism by the use of SSR markers combined with non-denatured polyacrylamide gel electrophoresis.And the effect of different factors on electrophoresis conditions was compared to explore the optimal SSR-PCR non-denatured polyacrylamide gel electrophoresis conditions in kernelled apricot.[Result]The optimal non-denatured polyacrylamide gel electrophoresis conditions for SSR-PCR were established as follows：polyacrylamide gel concentration 6%,the ratio of acrylamide to bisacrylamide 29∶1,electrophoresis at 1 000 V for 2-3 h,and staining for 15 min within 0.1% AgNO3.[Conclusion]The optimum electrophoresis system has provided some technical foundations to further study the phylogenetic relationship of kernelled apricots by SSR markers.

Preparation and physicochemical characterization of solid dispersion of quercetin and polyvinylpyrrolidone

Aim The objective of this study was to prepare and characterize quercetin-polyvinylpyrrolidone （Qurc-PVP） solid dispersion with the intention of improving its dissolution properties, Methods Qurc-PVP sclid dispersion was prepared by solvent method. The release rate of quercetin was determined from dissolution studies and the physicochemical properties of solid dispersion were investigated by differential scanning calorimetry （DSC）, infrared spectroscopy （IR）, powder X-ray diffraction （PXRD） and scanning electron microscopy （SEM）. Results The results showed that the dissolution rate of quercetin was significantly improved by solid dispersion compared to that of the pure drug and physical mixture, Solubility studies revealed a markedly increase in the solubility of quercetin. The results of DSC and PXRD showed that the quercetin in solid dispersion was amorphous form. From SEM analysis, there was no quercetin crystal observed in the solid dispersions. Conclusion The solubility and dissolution of quercetin were improved by solid dispersion technique.

Drag reduction behavior of hydrolyzed polyacrylamide/xanthan gum mixed polymer solutions

Partially hydrolyzed polyacrylamide（HPAM）as the main component of slickwater fracturing fluid is a shear-sensitive polymer,which suffers from mechanical degradation at turbulent flow rates.Five different concentrations of HPAM as well as mixtures of polyacrylamide/xanthan gum were prepared to investigate the possibility of improving shear stability of HPAM.Drag reduction（DR）measurements were performed in a closed flow loop.For HPAM solutions,the extent of DR increased from 30%to67%with increasing HPAM concentration from 100 to1000 wppm.All the HPAM solutions suffered from mechanical degradation and loss of DR efficiency over the shearing period.Results indicated that the resistance to shear degradation increased with increasing polymer concentration.DR efficiency of 600 wppm xanthan gum（XG）was 38%,indicating that XG was not as good a drag reducer as HPAM.But with only 6%DR decline,XG solution exhibited a better shear stability compared to HPAM solutions.Mixed HPAM/XG solutions initially exhibited greater DR（40%and 55%）compared to XG,but due to shear degradation,DR%dropped for HPAM/XG solutions.Compared to 200 wppm HPAM solution,addition of XG did not improve the drag reduction efficiency of HPAM/XG mixed solutions though XG slightly improved the resistance against mechanical degradation in HPAM/XG mixed polymer solutions.

Study on purification technology of polyacrylamide wastewater by non-thermal plasma

In this work, non-thermal plasma has been applied to treat polyacrylamide（PAM） wastewater.We have investigated the influence of the rule of PAM wastewater initial pH, solution concentration and discharge time, discharge voltage on chemical oxygen demand（COD）degradation rate. At the same time, the effect of pH and discharge time on the viscosity removal rate of PAM solution was also studied. Then, the effect of pH on the viscosity removal rate of1.0 gl-1 PAM solution was studied separately. Through orthogonal test, the factors affecting the COD degradation rate of PAM wastewater were determined as follows: discharge time > discharge voltage > solution concentration > wastewater initial pH. The COD highest removal rate of PAM wastewater reached 85.74%, when the optimal conditions are as follows:discharge voltage 40 k V, discharge time 5 h, solution concentration 1.0 gl-1, pH 1.5. This research provides some basic data and new theoretical basis for PAM wastewater purification.

MONODISPERSE MICRON-SIZED POLYACRYLAMIDE PARTICLES SYNTHESIZED BY DISPERSION POLYMERIZATION

Monodisperse micron-sized polyacrylamide （PAM） particles with a regular shape have been successfully prepared through dispersion polymerization of the monomer using a rotary reactor. FTIR and NMR spectroscopic results demonstrated the formation of PAM. POM and TEM observations revealed that PAM particles had a regular shape and good dispersity. A thick layer of surfactant （PVP） still existed on PAM particles after multiple centrifugation and ultrasonic re-dispersion in ethanol, which indicates a strong interaction between PVP and PAM. The effects of various polymerization factors on the average size of PAM particles have also been studied.

Preparation of cationic polyacrylamide microsphere emulsion and its performance for permeability reduction

In this paper, cationic polyacrylamide microspheres （CPAM） were synthesized using acrylamide （AM） and methacryloyloxyethyl trimethyl ammonium chloride （TMAEMC） as monomers, ammonium sulfate as dispersant, poly（acryloyloxyethyl trimethyl ammonium chloride） （PAETAC） as dispersion stabilizer, and ammonium persulfate as initiator. The synthetic method was dispersion polymerization. The effects of monomer ratio （AM/TMAEMC）, dispersant concentration, and dispersion stabilizer dosage on dispersion polymerization were systematically studied to determine the optimal preparation conditions. The structure and viscosity of the synthesized polymer were characterized by FTIR and capillary viscometry, respectively, and the particle sizes and distribution of the polymer microspheres were characterized by microscopy and dynamic light scattering, respectively. Finally, flow tests were conducted to measure the permeability reduction performance of the microspheres at various concentrations in sand packs with different permeability. Results show that CPAM emulsion of a solids content of 1 wt% has excellent performance in low-to-medium permeability formations （〈 1,000 mD）, and the efficiency may reach above 90%.

Rheological Properties of Hydrophobically Associating Polyacrylamide Solution

A temperature-resistant, salt-tolerant polyacrylamide, hydrophobically associating polymer （HAP）, was synthesized in the State Key Laboratory of Heavy Oil Processing. The rheological behavior of HAP solution was investigated by means of flow experiments in porous media and by using a HAAKE RS600 rheometer. The results of Nuclepore membrane filtration showed that filtration time increased sharply when the critical association concentration was reached. Shear rate had a greater impact on viscosity and shear stress with increasing HAP concentration. The HAP solution with a concentration of 100 mg/L （salinity 32,868 mg/L） exhibited negative thixotropy. However, at the same salinity the HAP solution showed thixotropy and its viscosity became greater when the polymer concentration increased to 1,500 mg/L. The flow experiments in cemented core samples indicated that the resistance factor and residual resistance factor of the HAP solution were 31.8 and 12 when polymer concentration and salinity were 1,500 mg/L, 32,868 mg/L at 85℃ respectively, which is favorable for flooding application. Such factors of partially hydrolyzed polyaerylamide 3530S were merely 3.14 and 1.71, so it could not be applied to polymer flooding in the oilfield with high temperature and high salinity.

Treatment of Wastewater Containing Polyacrylamide Using Three Dimensional Electrodes

A method using three-dimensional electrode is applied to treat wastewater in oil fields, which contains polyacrylamide （PAM）, for analogue. A best condition for electrolysis （I= 1.0 A, t=90 min, c=0.1%, m=980 g,φ=5 mm, d=5.0 cm） has been determined, under which the COD removal efficiency reached 96.0%, COD containing in wastewater reduced to 64.3 mg/L from 1 622.9 mg/L, the figure before treatment. Three categories of PAM-containing wastewater in production practice have been treated with the COD removal ratios being 87.5%, 82.4% and 84.7% respectively. Presence of H2O2 and ·OH are detected by means of Ti（IV）-5-Br-PADAP technique and colorimetry respectively. The concentration is positively proportional to the COD removal ratio and increases in accordance with increment of time of electrolysis and current.

Molecular Simulations of the Effect of Hydrated Montmorillonite on the Viscosity of Polyacrylamide under Confined Shear

Our researches are based on the fact that the systems composed of polyacrylamide and montmorillonite under a kind of shear state often appear in some important practical processes like drilling well etc. The viscosity of polyacrylamide is usually the most important one among the characteristics to decide if the practical processes succeed or not. Therefore, we studied the effect of hydrated montmorillonite on the viscosities of polyacrylamide with temperature and shear rate varying under confined shear by molecular simulation method. Adopting the condition of confined shear in the research could make our simulations and the practical processes as similar as possible. First, the model of one polyacrylamide polymer chain with 20 monomers linearly linking surrounded by water molecules between two of montmorillonite layers was constructed. Then canonical ensemble （NVT） MD simulations were carried out for the built model at different temperatures and shear rates. From the gained simulation results, we calculated the polymer＇s structural property-radius of gyration, which was directly related to the viscosity property of polyacrylamide polymer. It was found that the viscosity of the polyacrylamide polymer between hydrated clay layers decreased with the temperature increasing from 298 to 343 K under the condition of confined shear. The variation trend of viscosity from simulation results was also confirmed by our experiments. Besides, the viscosity of the polyacrylamide between hydrated clay layers decreased with the shear rate increasing within the range of higher shear rates.

Determination of the Structure of Polyacrylamide/Aluminum Citrate Colloidal Dispersion Gel System

1 INTRODUCTIONIn recent years,colloidal dispersion gel(CDG)have been attracting more and more in thefield of enhanced oil recovery on account of the cost-effectiveness and high efficiency ofblocking formation.Compared with bulk gel(BG),CDG exhibits lower polymer concentra-tion,undefined shape and selective blocking formation characteristics.The characteris-tics of CDG and BG are related to structure.In the bulk gel a continuous network of polymermolecules is formed predominant through intermolecular cross-linkages.The

Preparation of Dysprosium Ferrite/Polyacrylamide Magnetic Composite Microsphere and Its Characterization

Using the technique of microemulsion polymerization with nano-reactor, dysprosium ferrite/polyacrylamide magnetic composite microsphere was prepared by one-step method in a single inverse microemulsion. The structure, average particle size, morphology of composite microsphere were characterized by FTIR, XRD, TEM and TGA. The magnetic responsibility of composite microsphere was also investigated. The results indicate that the magnetic composite microsphere possess high magnetic responsibility and suspension stability.