Fen Ran

Biocompatibility of modified polyethersulfone membranes by blending an amphiphilic triblock co-polymer of poly(vinyl pyrrolidone)-b-poly(methyl methacrylate)-b-poly(vinyl pyrrolidone).

An amphiphilic triblock co-polymer of poly(vinyl pyrrolidone)-b-poly(methyl methacrylate)-b-poly(vinyl pyrrolidone) (PVP-b-PMMA-b-PVP) was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The block co-polymer can be directly blended with polyethersulfone (PES) using dimethylacetamide (DMAC) as the solvent to prepare flat sheet and hollow fiber membranes using a liquid-liquid phase separation technique. The PVP block formed a brush on the surface of the blended membrane, while the PMMA block mingled with the PES macromolecules, which endowed the membrane with permanent hydrophilicity. After adding the as-prepared block co-polymer the modified membranes showed lower protein (bovine serum albumin) adsorption, suppressed platelet adhesion, and a prolonged blood coagulation time, and thereby the blood compatibility was improved. Furthermore, the modified PES membranes showed good cytocompatibility, ultrafiltration and protein anti-fouling properties. These results suggest that surface modification of PES membranes by blending with the amphiphilic triblock co-polymer PVP-b-PMMA-b-PVP allows practical application of these membranes with good biocompatibility in the field of blood purification, such as hemodialysis and bioartificial liver support.

Improved blood compatibility of polyethersulfone membrane with a hydrophilic and anionic surface

In this study, a novel triblock copolymer of poly (styrene-co-acrylic acid)-b-poly (vinyl pyrrolidone)-b-poly(styrene-co-acrylic acid) (P(St-co-AA)-b-PVP-b-P(St-co-AA)) is synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization, and used for the modification of blood contacting surface of polyethersulfone (PES) membrane to improve blood compatibility. The synthesized block copolymer can be directly blended with PES to prepare PES membranes by a liquid-liquid phase separation technique. The compositions and structure of the PES membranes are characterized by thermogravimetric analysis (TGA), ATR-FTIR, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM); the surface charge density of the modified PES membrane was measured by Zeta-potential; the blood compatibility of the PES membranes was assessed by detecting bovine serum albumin (BSA) and bovine serum fibrinogen (BFG) adsorption, platelet adhesion, activated partial thromboplastin time (APTT), platelet activation, and thrombin-antithrombin III (TAT) generation. The results indicated that the blood compatibility of the modified PES membrane was improved due to the membrane surface modification by blending the amphiphilic block copolymer and the surface segregation of the block copolymer.

Heparin‐Like Macromolecules for the Modification of Anticoagulant Biomaterials

A heparin-like structured macromolecule (HLSM) is synthesized by RAFT polymerization using carboxyl-terminated trithiocarbonate as the RAFT agent. The HLSM can be directly blended with PES in DMAC to prepare flat-sheet membrane by means of a liquid-liquid phase separation technique. The synthesized polymeric material retard blood clotting and the modified membrane exhibits good anticoagulant ability due to the existence of the important functional groups SO(3) H, COOH and OH. The anionic groups on the membrane surface may bind coagulation factors and thus improve anticoagulant ability. The results indicate that the HLSM has potential to improve the anticoagulant properties of biomaterials and to be applied in blood purification including hemodialysis and bioartificial liver supports.

Direct synthesis of heparin-like poly(ether sulfone) polymer and its blood compatibility.

In this study, heparin-like poly(ethersulfone) (HLPES) was synthesized by a combination of polycondensation and post-carboxylation methods, and was characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance hydrogen spectrum and gel permeation chromatography. Owing to the similar backbone structure, the synthesized HLPES could be directly blended with pristine PES at any ratios to prepare PES/HLPES membranes. After the introduction of HLPES, the microscopic structure of the modified PES membranes was changed, while the hydrophilicity was significantly enhanced. Bovine serum albumin and bovine serum fibrinogen adsorption, activated partial thromboplastin time, thromb time and platelet adhesion for the modified PES membranes were investigated. The results indicated that the blood compatibility of the PES/HLPES membranes was significantly improved compared with that of pristine PES membrane. For the PES/HLPES membranes, obvious decreases in platelet activation on PF-4 level, in complement activation on C3a and C5a levels, and in leukocytes activation on CD11b levels were observed compared with those for the pristine PES membrane. The improved blood compatibility of the PES/HLPES membrane might due to the existence of the hydrophilic groups (-SO3Na, -COONa). Furthermore, the modified PES membranes showed good cytocompatibility. Hepatocytes cultured on the PES/HLPES membranes presented improved growth in terms of SEM observation, MTT assay and confocal laser scanning microscope observation compared with those on the pristine PES membrane. These results indicate that the PES/HLPES membranes present great potential in blood-contact fields such as hemodialysis and bio-artificial liver supports.

Toward a highly hemocompatible membrane for blood purification via a physical blend of miscible comb-like amphiphilic copolymers

Comb-like amphiphilic copolymers (CLACs) consisting of functional chains of poly(vinyl pyrrolidone) and polyethersulfone-based hydrophobic chains were firstly synthesized by reversible addition-fragmentation chain transfer polymerization. The CLAC can be used as an additive to blend with polyethersulfone (PES) at any ratio due to the excellent miscibility, and then a surface segregation layer with permanent hydrophilicity could be obtained. The surfaces of the CLAC modified PES membranes were characterized using X-ray photoelectron spectroscopic analysis, Fourier transform infrared and water contact angle measurements. The surfaces are self-assembled with numerous functional branch-like -PVP chains, which can improve the hemocompatibility. The root-like -PES chains (the hydrophobic part) are embedded in the membranes firmly, which greatly reduces the elution during the membrane preparation procedure and repeated usage, and makes the membranes have a permanent stability. The PES-based hydrophobic chains have the same structure as the membrane bulk material, which makes the miscibility of the additive and the membrane material good to ensure the intrinsic properties of the membrane. The modified membranes showed suppressed platelet adhesion and prolonged blood coagulation time (activated partial thromboplastin time, APTT); thus, the blood compatibility of the membranes was highly improved. The strategy may be extended to synthesize other PES-based functional copolymers and to prepare a modified PES dialysis membrane for blood purification.

Synthesized negatively charged macromolecules (NCMs) for the surface modification of anticoagulant membrane biomaterials

A series of negatively charged macromolecules (NCMs) including poly (sulfonated styrene-co-methyl methacrylate) (P(SS-co-MMA)), poly (acrylic acid-co-methyl methacrylate) (P(AA-co-MMA)) and poly (sulfonated styrene-co-acrylic acid-co-methyl methacrylate) (P(SS-co-AA-co-MMA)) are synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization using carboxyl-terminated trithiocarbonate as a RAFT agent. Activated partial thromboplastin time (APTT) tests indicate that the NCMs can retard blood clotting due to the negatively charged groups. The synthesized NCMs can be blended with polyethersulfone (PES) in dimethylacetamide (DMAC) to prepare membranes by means of a liquid-liquid phase separation technique. The prepared membranes were regular and smooth, except P(AA-co-MMA) modified membranes which were crude and rough due to the poor miscibility of AA segment and PES. The NCM modified PES membranes exhibited good anticoagulant ability due to the existence of the large density of the negative charges on the membrane surface, which induced a strong electrostatic repulsion with the negatively charged blood constituents. Therefore, the P(SS-co-AA-co-MMA) was designed and prepared with appropriate proportions of SS, AA and MMA for better membrane performance. The results indicated that the P(SS-co-AA-co-MMA) had potential to improve the anticoagulant property of biomaterials and to be applied in blood purification.

A dandelion-like carbon microsphere/MnO2 nanosheets composite for supercapacitors

This article reported the electrochemical performance of a novel cabon microsphere/MnO2 nanosheets (CMS/MnO2) composite prepared by a in situ self-limiting deposition method under hydrothermal condition. The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that MnO2 nanosheets homogeneously grew onto the surface of CMS to form a loose-packed and dandelion-like core/shell microstructure. The unique microstructure plays a basic role in electrochemical accessibility of electrolyte to MnO2 active material and a fast diffusion rate within the redox phase. The results of cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectrometry indicated that the prepared CMS/MnO2 composite presented high capacitance of 181 F·g−1 and long cycle life of 61% capacity retention after 2000 charge/discharge cycles in 1 mol/L Na2SO4 solution, which show strong promise for high-rate electrochemical capacitive energy storage applications.

A simple method to prepare modified polyethersulfone membrane with improved hydrophilic surface by one-pot: The effect of hydrophobic segment length and molecular weight of copolymers.

A simple method to prepare modified polyethersulfone (PES) membrane by one-pot is provided, and the method includes three steps: polymerization of vinyl pyrrolidone (VP), copolymerization of methyl methacrylate (MMA) and blending with PES. The effect of the PMMA segment length and molecular weight of the copolymer (PVP-b-PMMA-b-PVP, as an additive) on the structures and properties of the modified membranes was investigated. Activated partial thromboplastin time (APTT) tests indicated that with the increase of the poly(methyl methacrylate) (PMMA) segment length in the chains of the copolymers and with the increase of the molecular weight of the copolymers, the APTTs of the modified membranes increased to some extent, since less of the additives were lost during liquid-liquid phase separation process. Therefore, the copolymer was designed and prepared with appropriate ratio of poly(vinyl pyrrolidone) (PVP) to MMA and with appropriate molecular weight for better membrane performance. When the copolymer was blended in the membrane, the water permeance, protein anti-fouling property and sieving coefficients for PEG-12000 increased obviously. The simple, credible and feasible method had the potential to be used for the modification of membranes with improved blood compatibility, ultrafiltration and antifouling properties of biomaterials and for practical production.

A hierarchical porous carbon membrane from polyacrylonitrile/polyvinylpyrrolidone blending membranes: Preparation, characterization and electrochemical capacitive performance

Abstract Novel hierarchical porous carbon membranes were fabricated through a simple carbonization procedure of well-defined blending polymer membrane precursors containing the source of carbon polyacrylonitrile (PAN) and an additive of polyvinylpyrrolidone (PVP), which was prepared using phase inversion method. The as-fabricated materials were further used as the active electrode materials for supercapacitors. The effects of PVP concentration in the casting solution on structure feature and electrochemical capacitive performance of the as-prepared carbon membranes were also studied in detail. As the electrode material for supercapacitor, a high specific capacitance of 278.0 F/g could be attained at a current of 5 mA/cm 2 and about 92.90% capacity retention could be maintained after 2000 charge/discharge cycles in 2 mol/L KOH solution with a PVP concentration of 0.3 wt% in the casting solution. The facile hierarchical pore structure preparation method and the good electrochemical capacitive performance make the prepared carbon membrane particularly promising for use in supercapacitor.

Super long-life supercapacitor electrode materials based on hierarchical porous hollow carbon microcapsules

Remarkable supercapacitor electrodes with a high specific supercapacitance and a super long cycle life were achieved by using hierarchical porous hollow carbon microcapsules (HPHCMs) as active materials. HPHCMs were prepared by a facile chemical route based on pyrolysis of a soft sacrificial template involving a non-crosslinked core of poly(styrene-r-methylacrylic acid) and a crosslinked shell of poly(styrene-r-divinylbenzene-r-methylacrylic acid), which were synthesized by using traditional radical polymerization and emulsion polymerization. The results of scanning electron microscopy, transmission electron microscopy and Brunauer–Emmett–Teller characterizations revealed that HPHCM possessed the desired pore structure with apparent macro-/meso- and micropores, which not only provided a continuous electron-transfer pathway to ensure good electrical contact, but also facilitated ion transport by shortening diffusion pathways. As electrode materials for supercapacitor, a high specific capacitance of 278.0 F g−1 was obtained at the current density of 5 mA cm−2. Importantly, after 5000 potential cycles in 2 M KOH electrolyte at the discharge current density of 20 mA cm−2, the capacitance actually increased from 125 to 160 F g−1 and then remained 151 F g−1, corresponding to a capacitance retention of 120%, likely due to electrochemical self-activation.