60Co γ-ray irradiation modified poly(4-methyli-pentene) membrane for oxygenator

Multiphase separated polymers are of great interest owing to unique characteristics such as high mechanical strengths, surface functionality and blood compatibility. It was well known that surface consisting of poly(styrene-b-HEMA) showed an excellent blood compatibility [1]. While, it was found that poly[4-{bis(trimethylsilyl)methyl}styrene](BSMS) membrane had fairly high oxygen permeability among vinyl polymers owing to its high Si-content and fairly high free space in the membrane [2]. So, we synthesized new silicon-containg block copolymer based on BSMS with HEMA, possessing the hydrophobic and hydrophilic segments. The block copolymer membranes were prepared by the different two methods. Thus obtained block copolymer surface showed microphase separated structures in spite of membrane preparation methods. However, the membranes obtained by the deprotection in matrix was found numerous pores. On the other hand, no pore was shown in the membrane prepared by another method. Moreover, even in the membrane having pores on the surface, a significant degree of platelets adhesion and deformation was surpressed. In this paper, we report on synthesis of poly(BSMS- b-HEMA) and their properties.

Poly(ester urethane) (PU) with functional groups (amide, hydroxyl, carboxyl) on surfaces were prepared by grafting monomers such as acrylamide (AAm), hydroxyethyl acrylate (HEA), and methacrylic acid (MAA) onto the PU membranes. Grafting copolymerization was carried out by the combined use of photooxidization and UV irradiation grafting. The PU membrane was photooxidized in hydrogen peroxide solution under UV light to yield hydroperoxide groups on the surface and then irradiation grafting with monomer in water. The ATR-FTIR spectrum, X-ray photoelectron spectroscopy characterized the grafted copolymers and verified the occurrence of grafting copolymerization. The results showed that the content of hydroperoxide groups yielded was dependent on the photooxidization time and reached maximum at about 8 h. Grafting copolymerization was enhanced when irradiating by UV light. The degree of grafting was increased with the increase of content of hydroperoxide groups, irradiation time, and monomer concentration. The grafting copolymerization was enhanced when an appropriate amount of ferrous ions was added. After grafting, the wettability of PU and the water absorption percentage increased with the degree of grafting. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2505–2512, 2000

Poly(ester urethane) (PU) with functional groups (amide, hydroxyl, carboxyl) on surfaces were prepared by grafting monomers such as acrylamide (AAm), hydroxyethyl acrylate (HEA), and methacrylic acid (MAA) onto the PU membranes. Grafting copolymerization was carried out by the combined use of photooxidization and UV irradiation grafting. The PU membrane was photooxidized in hydrogen peroxide solution under UV light to yield hydroperoxide groups on the surface and then irradiation grafting with monomer in water. The ATR-FTIR spectrum, X-ray photoelectron spectroscopy characterized the grafted copolymers and verified the occurrence of grafting copolymerization. The results showed that the content of hydroperoxide groups yielded was dependent on the photooxidization time and reached maximum at about 8 h. Grafting copolymerization was enhanced when irradiating by UV light. The degree of grafting was increased with the increase of content of hydroperoxide groups, irradiation time, and monomer concentration. The grafting copolymerization was enhanced when an appropriate amount of ferrous ions was added. After grafting, the wettability of PU and the water absorption percentage increased with the degree of grafting. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2505–2512, 2000

Blood filtration requires a high removal ratio of leukocytes and with simultaneous high recovery ratio of platelets and other beneficial components. Problems are often encountered with blood filter materials in terms of high platelet loss. Zwitterions such as phosphorylcholine, sulfobetaine and carboxybetaine show effective resistance against protein adsorption and platelet adhesion. The study reported was aimed at achieving surface modification of poly(butylene terephthalate) non‐woven fabric (PBTNF) using UV radiation‐induced graft copolymerization of a zwitterionic sulfobetaine,N‐(3‐sulfopropyl)‐N‐methacroyloxyethyl‐N,N‐dimethylammonium betaine (SMDB), in order to improve the wettability and platelet recovery ratio of the PBTNF. Attenuated total reflection Fourier transform infrared and X‐ray photoelectron spectroscopy results showed that SMDB was successfully grafted onto the PBTNF. Photoinitiator concentration, monomer concentration and UV irradiation time affected markedly the degree of grafting. Critical wetting surface tension, water wetting time and hemolysis tests showed an improvement in wettability and blood compatibility as a result of graft copolymerization of SMDB. A blood filter material composed of SMDB‐modified PBTNF reduced platelet adhesion and had higher platelet recovery compared to poly(acrylic acid)‐modified PBTNF. It was found that SMDB monomer was successfully grafted onto PBTNF using UV radiation. The degree of grafting of SMDB could be controlled by varying the photoinitiator concentration, monomer concentration and UV irradiation time. SMDB‐modified PBTNF showed significant improvement in wettability and blood compatibility. The zwitterionic structure of SMDB is resistant to platelet adhesion. The SMDB‐modified PBTNF could be a candidate for a blood filter material and in other medical applications. Copyright © 2010 Society of Chemical Industry

Formaldehyde aqueous solution can act as an effective photoinitiating system for water‐borne photografting. The photografting of acrylic acid (AA) and methacrylic acid (MAA) onto high‐density polyethylene (HDPE), low‐density polyethylene (LDPE) and polypropylene (PP) initiated by formaldehyde aqueous solutions has been reported. The effects of formaldehyde content and monomer concentration on grafting varied with the polymeric substrates and monomers used. For the grafting of AA onto HDPE, the extent of grafting increased with increasing formaldehyde content in the solution, monomer concentration had a little effect on grafting. Whereas for the grafting of MAA onto HDPE, the grafting performed in 8% formaldehyde aqueous solution lead to the highest extent of grafting, the extent of grafting increased with monomer concentration till 2.5 mol/L. MAA was easier to be grafted onto the polyolefins than AA. The easiness of grafting occurring on the polyolefins was in a decreasing order of LDPE > HDPE > PP. Qualitative and semi‐quantitative Fourier transform infrared (FTIR) characterizations of the grafted samples were performed. For both grafted LDPE and PP samples, at the same irradiation time, the carbonyl index of the samples grafted with MAA was higher than that grafted with AA. The FTIR results are in accord with the results obtained by gravimetric method. The water absorbency of the grafted samples increased almost linearly with the extent of grafting. The PE films grafted with AA adsorbed more water than those grafted with MAA. This study had broadened the water‐borne initiating system for photografting. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

With the aim of developing a high-performance membrane-type artificial lung, a novel silicon-containing hydrophilic-hydrophobic block copolymer was prepared using a living anionic polymerization technique. To introduce high oxygen permeability, poly(4-[bis (trimethylsilyl)methyl)styrene]) [poly(BSMS)] was employed for the hydrophobic segment. Poly(2-hydroxyethyl methacrylate) [poly(HEMA)] segment was chosen as a counterpart to maintain high blood compatibility. A poly(BSMS-block-HEMA) [BH(X), where X denotes the mole fraction of BSMS in the copolymer] membrane showed a clear separation of microphase structure when the mole fraction X was more than 30% (cast from toluene solution), while BH(10) showed no marked phase separation, when the respective polymer was cast from a dimethylformamide (DMF) solution. It should be noted that DMF is a poor solvent for the poly(BSMS) segment. From a dynamic light scattering measurement of a DMF solution of BH(10) (0.1% w/v), submicron-sized particles were observed. The BH(10) surface prepared from this DMF solution containing submicron particles showed unique characteristics. The wettability of the BH(10) membrane was much higher than that of the poly(HEMA) surface, despite the introduction of the hydrophobic polymer segment. The equilibrium water content of the BH(10) was also higher than that of poly (HEMA). This may be explained by the supramolecular structure of the BH(10) membrane derived from the particle-casting technique. Also surprising was that the BH(10) surface showed extremely high blood compatibility. Indeed, the rate of adhesion and activation of rabbit platelets on the surface was much lower than on poly(styrene-block-HEMA), which we have shown to have fairly high blood compatibility. From these results, it can be concluded that BH(10) is a promising candidate for a novel blood-compatible material for use in such applications as an artificial lung and as a nonthrombogenic coating material.

Graft copolymers of acrylic monomers with cotton cellulose were obtained. The dependence of the degree and efficiency of grafting of acrylic acid and methyl methacrylate to cellulose on the concentration of monomer and initiator was investigated. Pre-adsorption of the initiator in the macromolecules of cellulose leads to an increase in the efficiency of the grafting. The efficiency of grafting is higher in those systems in which the initiator used is insoluble in the monomer solvent. Absorption of cellulose with an aqueous solution of the initiator - potassium persulfate, followed by removal of water was done. The advantage of using a water-soluble initiator is that during subsequent processing with a solution of monomer in an organic solvent, the desorption of the active centers does not occur. An increase in the concentration of theinitiator leads to an increase in the degree of grafting, a slight increase in the efficiency of the grafting, a significant decrease in the degree of polymerization and the molecular weight of the graft chains. In a heterogeneous process, an increase in the efficiency of grafting with an increase in the concentration of theinitiator is promoted by the additional adsorption interaction of the initiator molecules with the surface of cellulose. With an increase in the concentration of monomers, the overall degree of conversion slightly increases, the efficiency of grafting slightly decreases, the degree of grafting and the molecular weight of the graft chains increase significantly. The mechanism of graft copolymerization was investigated by comparative analysis of the IR and PMR spectra of cellulose, potassium persulfate, acrylic monomers and products of their interaction. Due to the results of spectroscopic studies, a scheme of graft copolymerization reactions has been proposed. The active centers of graft copolymerization are formed as a result of the reductive interaction of potassium persulfate, water and cellulose macromolecules.

The polymerization of methyl methacrylate in bulk initiated by azoisobutyronitrile has been studied to high conversions at a range of initiator concentrations ([AIBN] = 0.0125 - 0.2 mol dm-3) and polymerization temperatures (45 - 80°C), with the aim of evaluating the rate parameters for polymerization across the entire conversion range.Conversion-time data were obtained using modern spectroscopic techniques such as Raman, nuclear magnetic resonance and Fourier-transform near infrared spectroscopy to follow the decrease in monomer concentration during polymerization in situ. A novel technique for estimating conversion, by indirectly measuring the change in dielectric constant during in situ polymerization in an electron spin resonance (ESR) spectrometer, was also developed.The propagating radical concentration was measured continuously throughout polymerization by ESR spectroscopy. A cryogenic, quenching technique was used to measure the low radical concentrations in the steady-state region of polymerization below the gel transition.Combination of the radical concentration-time and conversion-time dependences enabled the calculation of the rate constants for propagation, kp, and termination, kt. It has been possible to obtain these rate parameters at high conversions for the first time, as well as at low conversions. For the polymerization of methyl methacrylate at 60°C, kp = 500 ± 100 dm3mol-1s-1, and kt = 2.1 ± 0.2 x 107 dm3mol-1s-1 in the steady-state region. At higher conversions, kp and kt decrease; the decline in kp occurs after the glass transition point, while kt decreases by several orders of magnitude during the gel effect. In the glass region, for polymerizations at 60°C, kp ≃ 10 ± 5 dm3mol-1s-1, while kt ≃ 1 - 10 dm3mol-1s-1. The decrease in initiation efficiency, f, has also been estimated; at high conversions f ≃ 10-4 - 10-3.The study was extended to a brief examination of the homopolymerizations at 45°C of methacrylic acid and acrylic acid, which are heterogeneous. The concentrations of methacrylic acid propagating radical observed by ESR spectroscopy were an order of magnitude larger than those measured for the polymerization of methyl methacrylate under similar conditions. It was possible to estimate termination rate constants and initiation efficiencies for the homopolymerization of methacrylic acid at high conversion; kt ≃ 0.1 dm3mol-1s-1, and f ≃ 0.1 .The γ-radiolysis of two water-soluble polymers, poly(methacrylic acid) and poly(acrylic acid), has also been investigated. Radical intermediates were identified by ESR spectroscopy. The major reaction is decarboxylation; volatile products detected by gas chromatography comprised mainly carbon dioxide and carbon monoxide, with G(CO2) + G(CO) ≃ 12 for poly(acrylic acid). The yields of these gases from the polymers were considerably larger than yields measured for aliphatic and dicarboxylic acids.It has been demonstrated that scission and crosslinking yields (G(S) and G(X)) can be determined from the dose-dependences of weight- and z-average molecular weights. An advantage of the proposed procedure is the sensitivity of the z-average molecular weight to crosslinking, which allows G(S) and G(X) to be obtained from studies of samples exposed to low radiation doses. The procedure was shown to be applicable to a wide range of initial molecular weight distributions and G(S)/G(X) ratios.Scission and crosslinking yields for poly(acrylic acid) and poly(methacrylic acid) were determined from the dose-dependences of weight- and z-average molecular weights obtained by sedimentation equilibrium measurements using an analytical ultracentrifuge. Poly(acrylic acid) was shown only to crosslink, whereas poly(methacrylic acid) undergoes scission.

Photoinitiated surface grafting of acrylic monomers has been carried out onto high strength polyethylene (HSPE) yarn by means of a continuous process. The grafting reaction is initiated by UV irradiation of the yarn after presoaking in an acetone solution of initiator and monomer. Four initiators, benzophenone (BP), 4‐chlorobenzophenone (4‐CBP), 2‐hydroxy‐2‐cyclohexylacetophenone (HHA), and 2,2‐dimethoxy‐2‐phenylacetophenone (DMPA), and two monomers, acrylic acid (AA) and acrylamide (AM), have been used. After short irradiation time (10 to 20 s) successful grafting is obtained, as shown by ESCA and IR‐ATR spectra, dye adsorpotion from aqueous solution, and measurements of adhesion of single filaments to epoxy resin. Grafting efficiency of 74% has been reached for AA as monomer (26% is homopolymer). The tensile strength and modulus of the HSPE yarn are retained in the grafting process. The degree of surface grafting is mainly a function of structure and concentration of monomer and photoinitiator in the presoaking solution and of the irradiation conditions used. Increasing irradiation time gives increasing amounts of grafted polymer up to a certain limiting value. The reactivities of the four initiators have been compared showing the highest grafting yields of AA with BP and of AM with 4‐CBP as photoinitiator. AA grafted HSPE yarn can be dyed to rather deep color by dipping in an aqueous solution of Crystal Violet. Increased dye absorption by a factor of up to seven has been measured for yarn grafted with AA to the maximum level obtained. The filaments of the grafted yarn show increased adhesion to epoxy resin by a factor of up to five compared with the ungrafted filaments.

Metals and metal alloys are widely used in medical devices that contact blood and/or tissue, and various coating materials for the metal parts have been proposed to improve surface properties such as biocompatibility. This study aims to understand the performance of new coating materials, copolymers of methyl acrylate and acrylic acid, in terms of their biocompatibility and adhesive strength to a metal surface. Blood compatibility was investigated through platelet and coagulation system responses. Cytocompatibility was studied in three cell-line types (endothelium, smooth muscle, and fibroblasts) in terms of cell viability and morphology; these tests showed that compatibility depended on the cell types and acrylic acid content of the copolymers. Because of their blood compatibility and adhesion strength, the methyl acrylate and acrylic acid copolymers containing 10–24 mol% acrylic acid were found to be excellent candidates as potential coating materials for devices contacting blood.

The permeabilities of carbon dioxide, nitrous oxide and oxygen and their mixtures through silicone rubber and cellulose acetate membranes

Utilizing the factors of degradation and crosslinking of TPX polymer and high O2/N2 selectivity of MMA, the performances of MMA homografted TPX membrane are efficiently improved compared to those of pure TPX membrane. The degradation and crosslinking of TPX polymer solution with or without dissolved oxygen during irradiation were observed and proved in existence by the gas permeability, mechanical, and viscosity change study. High O2/N2 permeability ratio of 7.6 and fairly high oxygen permeability of 28 × 10−10 cm3 cm/cm2 s cm Hg of the membrane which was cast from the degassing polymer solution, with 20% degree of MMA grafting, can be obtained. Also the membrane for high oxygen permeability of 63 × 10−10 cm3 cm/cm2 s cm Hg with an O2/N2 permeability ratio of 4.5, which was cast from the polymer solution with dissolved oxygen, can be obtained under the condition of 60 h irradiation time and about 7% degree of grafting. O2/N2 selectivity of TPX membrane can be improved by homografting method with lower MMA grafting degree than that of heterografting method.

Optimization of acrylic acid grafting onto polypropylene using response surface methodology and its biodegradability

Heat transfer for laminar slip flow of a rarefied gas in a parallel-plate channel or a circular tube with uniform wall temperature : Inman, Robert M., Lewis Research Center, Cleveland, Ohio, NASA TN D-2213, November 1964, 38 p, graphs and tables

Acrylic polymer-grafted polypropylene sutures for covalent immobilization or reversible adsorption of vancomycin