Low-pressure plasma surface modification of polyurethane films with chitosan and collagen biomolecules

Polyurethane (PU) was synthesized using castor oil and a trade grade of hexamethylene diisocyanate, and then PU films were prepared for wound dressing applications. The PU films were then plasma treated with the low-pressure nitrogen plasma to functionalize with peroxide and hydroperoxide groups in order to attach with acrylic acid monomers. Therefore, the polyacrylic acid polymer branches were formed on the film surfaces. Carboxylic acid groups were activated by N-(3-dimethylaminopropyl)-N′-ethyl carbodiimide hydrochloride/N-hydroxysuccinimide and bonded with chitosan and collagen biomolecules. Untreated, nitrogen plasma treated, polyacrylic acid grafted, and finally chitosan and collagen-immobilized PU films were characterized by several tests. The tests included the attenuated total reflectance Fourier transform infrared spectroscopy, static contact angle, atomic force microscopy, scanning electron microscopy, fibroblast L929 cell culture, and antibacterial activity assay to evaluate their in vitro cytocompatibility. The results confirmed that chitosan and collagen were immobilized successfully on the PU surfaces. The chitosan-immobilized PU and collagen-immobilized PU improved the adhesion and proliferation of fibroblast cells compared to untreated PU films. The chitosan-modified PU films exhibit the best antibacterial properties. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47567.     

Simple method for the layer-by-layer surface modification of multiwall carbon nanotubes

A simplified method for the surface modification of multiwall carbon nanotubes (MWCNTs) using the layer-by-layer (LbL) technique is proposed. In this approach, the minimum polyelectrolyte content was added to the solution in order to eliminate the tedious centrifugation step. The one pot LbL deposition of poly (diallyldimethylammonium chloride) (PDADMAC), and poly (sodium 4-styrenesulfonate), (PSS) is presented. UV–Vis spectroscopy and zeta potential measurements were used to determine the minimum PDADMAC and PSS concentration needed for the deposition of each polyelectrolyte layer. The deposition cycle was repeated until six layers of PDADMAC/PSS were deposited. The film growth was confirmed by transmission electron microcopy and was found to increase as a function of the number of deposited layers with a final thickness of 18 nm. Evidence of the alternate deposition of oppositely charged polyelectrolytes was further investigated by measurement of the zeta potential values which were found to reverse from positive to negative as a function of the number of deposited layers thus confirming the overcompensation of the surface charge at each adsorption step. This simple method could be useful for the fast preparation of large volumes of MWCNTs solutions in a single batch without the need for centrifugation step.     

Properties of polyethersulfone ultrafiltration membranes modified by polyelectrolytes

This study reports on the surface modification of ultrafiltration membranes using the layer-by-layer (LbL) technique. The novelty of this work resides in the LbL assembly of charged polyelectrolytes by electrostatic adsorption directly onto the ultrafiltration membranes without any prior treatment of the surface. Polyethersulfone ultrafiltration membranes have been employed for the deposition of branched poly(ethyleneimine) and poly(sodium 4-styrene sulfonate) to create a thin polyelectrolyte film on their surface. The modified membranes are characterized by their permeability and molecular weight cut-off (MWCO) value. Experiments show that the deposited polyelectrolyte layer causes a decrease in the permeability due to the additional resistance of the layers. However, the MWCO value is shifted meaning a better rejection of the dextran solution is achieved. Thus, the LbL assembly of polyelectrolyte multilayers on the surface of the membrane makes it possible to convert a membrane with open structure to a membrane with denser active layer.     

Preparation of collagen–polyurethane composite film and its subcutaneous implantation in rats: The improvement of tissue compatibility

This paper reports a safe, easy, effective, and one‐step process to introduce a collagen layer onto a polyester‐urethane surface for improving its biocompatibility and reducing acute inflammatory reaction. Collagen gel (COL) was spread onto the plasma‐treated polyurethanes (PU) film to make PU–COL composite film by lyophilization. In this process, collagen on the interface was covalently immobilized to PU surface. Density of immobilized collagen molecules was examined to find the optimal experiment condition. The surface properties of the immobilized film were characterized by attenuated total reflection infrared spectrum and X‐ray photoelectron spectroscopy to determine the efficiency of collagen immobilization. The results indicated that collagen chains had been grafted on PU surface because of plasma activation. To see if collagen modification can deduce acute inflammatory reaction and improve tissue guide regeneration, PU and PU–COL composite film were implanted subdermally in rats to analyze the effect of collagen immobilization. The reaction interface of PU–COL composite film and rat's tissue was observed by transmission electron microscope to analyze biocompatibility of PU–COL; unmodified PU film was used as control. The result showed that acute inflammatory reaction induced by PU–COL composite film had vanished gradually after 7 days and the material was embedded by tissue, almost forming a capsule. The capsule's wall thinned out gradually in the following days. Although the control group's inflammatory reaction did not vanish in 1 month and PU film embed in rat's tissue incompletely, PU implant migrated easily from the implant site. As a result, PU–COL composite film had most advantage in tissue guide regeneration and compatibility. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99:1832–1841, 2006     

Functionalization of multiwalled carbon nanotubes with uniform polyurea coatings by molecular layer deposition

In this study, we demonstrate a flexible method for functionalizing multiwalled carbon nanotubes (MWCNTs) with polyurea (PU) coatings using molecular layer deposition (MLD). Uniform and conformal PU films can be deposited on the surface of pristine MWCNTs without any surface treatment. The PU shell thickness and wrapping amount are precisely tunable by changing the number of MLD cycles. The present MLD functionalizing treatment provides better dispersion of the MWCNTs in highly polar solvents such as N,N-dimethylformamide, dimethyl sulfoxide, and 1-methyl-2-pyrrolidinone. Furthermore, the PU layers improve the compatibility between MWCNTs and the polyurethane matrix. Significant increases in tensile strength and modulus are obtained, resulting in greatly enhanced mechanical properties of PU-functionalized MWCNT/polyurethane composites.     

Hemocompatibility evaluation of polyurethane film with surface‐grafted poly(ethylene glycol) and carboxymethyl‐chitosan

To improve the hemocompatibility and biocompatibility of polyurethanes (PUs), PU surface was firstly modified by poly(ethylene glycol) PEG through acryloyl chloride and subsequently grafted on carboxymethyl‐chitosan (CMCS). Attenuated total reflection Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy analysis confirmed that carboxyl‐chitosan was grafted onto PUs surface. The surface properties of unmodified and modified PU films were determined and compared by water contact angle assessment. After PEG and CMCS grafting, the surface energy of the PU film was increased. Furthermore, the hemocompatibility of the modified PU films was systematically evaluated by bovine serum albumin (BSA) adsorption, the dynamic blood clotting test, the platelet adhesion test, and the hemolytic test. It appears that BSA adsorption and platelet adhesion were significantly curtailed for the modified PU films. Therefore, the obtained results showed the modified PU film has better hemocompatibility. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Collagen immobilization on poly(ethylene terephthalate) and polyurethane films after UV functionalization

An attractive alternative method to add new functionalities such as biocompatibility due to the micro- and nanoscaled modification of surfaces is offered by UV-modified polymers. The aim of this study was to evaluate the effect of the UV light functionalization on two polymers, poly(ethylene terephthalate) (PET) and polyurethane (PU) films, by means of atomic force microscopy (AFM), Fourier transform infrared–attenuated total reflectance (FTIR–ATR), and contact angle measurements. Thus, the UV-irradiation activates the polymers surface by breaking some chemical bonds and generation of new functional groups on the surface. This process can be controlled by the irradiation time. The topography provides the formation of superposed ‘nap’ and ‘wall-type’ structures on both untreated and treated samples. The surface parameters were found to depend on the polymer films before and after irradiation. The immobilization of collagen on PET surface was confirmed by X-ray photoelectron spectroscopy measurements and for PU surface was proved by FTIR–ATR. First technique suggests an increase of the nitrogen content at longer UV exposure time, and the second one reveals the appearance of the protein Amide I band. Supplementary, AFM measurements clearly revealed the presence of collagen attached on the polymer surface. Thus, these new UV-irradiated polymers are promising materials in our further attempts to obtain new biofunctionalized surfaces.     

Layer-by-layer approach to enable polyamide formation on microporous supports for thin-film composite membranes

Polyamide thin-film composite (PA-TFC) membranes make large-scale desalination effective. Interfacial polymerization (IP) is used to make PA-TFC membranes, but it may limit the range of monomers that can be used, which hinders progress toward advanced membranes. Layer-by-layer (LbL) sequential deposition could circumvent kinetic and thermodynamic limitations of the conventional IP process to facilitate incorporation of different co-monomers into the membrane. The selective layer needs to be deposited onto a microporous support, but depositing LbL coatings on microporous supports often results in defective membranes. Using a poly(vinyl alcohol) (PVA) primer between the support and the LbL polyamide layer may prevent defect formation. The water permeance and salt rejection of a three layer, PVA-primed, LbL-based PA-TFC membrane are discussed and compared to a membrane made without the PVA primer and a commercially available membrane. Mass transfer resistances are analyzed using a series resistance model and appear to be small or even negligible compared to that of the polyamide layer. Incorporation of a sulfonated co-monomer into the polyamide via LbL is reported. The combination of a PVA primer layer and LbL sequential deposition may expand the range of co-monomers that could be used relative to polyamide membranes prepared by the conventional IP process.     

Fabrication of a new type of organic-inorganic hybrid superlattice films combined with titanium oxide and polydiacetylene

We fabricated a new organic-inorganic hybrid superlattice film using molecular layer deposition [MLD] combined with atomic layer deposition [ALD]. In the molecular layer deposition process, polydiacetylene [PDA] layers were grown by repeated sequential adsorption of titanium tetrachloride and 2,4-hexadiyne-1,6-diol with ultraviolet polymerization under a substrate temperature of 100°C. Titanium oxide [TiO₂] inorganic layers were deposited at the same temperatures with alternating surface-saturating reactions of titanium tetrachloride and water. Ellipsometry analysis showed a self-limiting surface reaction process and linear growth of the nanohybrid films. The transmission electron microscopy analysis of the titanium oxide cross-linked polydiacetylene [TiOPDA]-TiO₂ thin films confirmed the MLD growth rate and showed that the films are amorphous superlattices. Composition and polymerization of the films were confirmed by infrared spectroscopy. The TiOPDA-TiO₂ nanohybrid superlattice films exhibited good thermal and mechanical stabilities.     

Physical properties of water‐borne polyurethane blended with chitosan

Water‐borne polyurethanes based on 4,4‐diphenylmethane diisocyanate, poly(butylene adipate), and chain extender N‐methyldiethanolamine (MDEA) that provided tertiary amine groups were synthesized. The polyurethane–chitosan (PU/CS) blends can be dissolved in the acetic acid and cast into films. The mechanical properties including tensile strength and elongation, as well as the water absorption and thermal properties of the PU/CS films were evaluated. The tensile strength increased with the increased amount of chitosan, but the elongation decreased accordingly. The chitosan in the blends promoted the water absorption. Chitosan was more thermally‐stable than PU, as shown in the thermal gravity analysis. Chitosan also had higher crystallinity, as demonstrated by differential scanning calorimetry. The blends were partial compatible mixtures, based on the data obtained from a dynamic mechanical analysis. Biocompatibility test was conducted utilizing immortalized rat chondrocytes (IRC). After IRC were seeded onto the PU/CS films for 1.5 and 120 h, the number of cells was counted and the morphology of cells was observed by light microscopy and scanning electron microscopy. Blends containing 30% chitosan had more cells attached initially. However, the blends containing more than 70% chitosan appeared to promote the cell proliferation. IRC were round on PU/CS films with more PU, but spread when the chitosan content in blends was higher. Overall, PU/CS films with more chitosan had better mechanical properties as well as biocompatibility. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2683–2689, 2007     

Effects of polydimethylsiloxane grafting on the calcification,physical properties,and biocompatibility of polyurethane in a heart valve

Segmented polyurethane (PU) has proven to be the best biomaterial for artificial heart valves, but the calcification of polyurethane surfaces causes serious problems in long‐term implants. This work was undertaken to evaluate the effects of polydimethylsiloxane (PDMS) grafting on the calcification, biocompatibility, and blood compatibility of polyurethane. A grafted polyurethane film was compared with virgin polyurethane surfaces. Physical properties of the samples were examined using different techniques. The hydrophobicity of the polyurethane films increased as a result of silicone modification. The effects of surface modification of polyurethane films on their calcification and fibroblast cell (L 929) and platelet behavior were evaluated in vitro. Fourier transform infrared spectroscopy indicated the direct involvement of the polyether soft segments of the polymer in the calcification process. Scanning electron microscopy of films indicated that grafting of silicone rubber to the surface of polyurethane successfully prevented the calcification process. The morphology of fibroblast cells that adhered to the PU films and modified films was similar to that of controls and showed the same proliferation. On the other hand, grafting PDMS onto PU did not affect the amount of platelets that adhered to the polyurethane surfaces. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 758–766, 2005     

Correlation between topographic structures and local field emission characteristics of graphene-sheet films

In an early report, some of us have demonstrated that graphene-sheet films prepared by electrophoretic deposition (EPD) method have great potential as high-performance field emission cathode. We report that the field emission performance from such graphene-sheet films may be enhanced. We have investigated the correlation between topographic structures and local field emission characteristics of graphene-sheet films, prepared with changing EPD deposition time. Detailed experiments show that samples prepared with longer deposition time have better field emission performance. Both scanning electron microscopy and high resolution transmission electron microscopy images show that the topographic structure of the surface layer of the samples deposited with longer time is formed with higher density of graphene sheets with shorter length and fewer graphene layers, in comparison with those with shorter deposition times. Such topographic structure is found experimentally to give large field enhancement. Computer simulation further confirms that a thinner graphene sheet will give more significant geometrical field enhancement at the corner of graphene sheet. Theoretical analysis shows that in an EPD process, longer-length graphene sheets will be deposited before shorter ones, explaining why with longer deposition time, the topographic structure of surface layer consists of shorter-length graphene sheets.     

Fabrication of amorphous calcium carbonate composite particles‐polymer multilayer films by a layer‐by‐layer method

Organic–inorganic hybrid multilayer films were prepared on a precoated cationic glass substrate by using a layer‐by‐layer (LbL) electrostatic self‐assembly technique with poly(diallyldimethylammonium chloride) as a polycation and submicron‐sized stable amorphous calcium carbonate (ACC) composite particles. The ACC composite particles (ACP) stabilized with poly(acrylic acid) were obtained by a carbonate controlled‐addition method. The average particles size of ACP was (1.8 ± 0.4) × 10² nm. An ethanolic dispersion of ACP was used for the LbL electrostatic self‐assembly technique on the precoated substrate due to instability of ACP in water. The deposition of the particles was confirmed by SEM analysis. The film thickness of the multilayer assembly increased from 230 to 710 nm with increasing the deposition layers. The FTIR spectra of scratched multilayer samples showed characteristic broaden peaks of ACC. The amorphous phase was stable after the LbL assembly process as well as after 2 months in a dry film state. POLYM. COMPOS., 36:330–335, 2015. © 2014 Society of Plastics Engineers     

Surface Modification of Titania Nanoparticles Using Ultrathin Ceramic Films

Surface modification of titania nanoparticles was achieved by coating them with ultrathin alumina films using atomic layer deposition. The coating process was performed in a fluidized bed reactor at low pressure and under mechanical vibration. Films were deposited using self-limiting, sequential surface reactions of trimethylaluminum and water. The composition of alumina-coated particles was verified using infrared spectroscopy. The deposited films had an average growth rate of 0.2 nm/coating cycle and were highly uniform and conformal as demonstrated by transmission electron microscopy and X-ray spectroscopy. Deposited alumina films were amorphous as verified through X-ray diffraction and high-resolution electron microscopy. The coating process did not promote particle sintering as validated via particle size and surface area analysis.     

Fabrication of superhydrophobic polylactide films with ultraviolet-shielding properties

ZnO is a useful material with stable physical and chemical properties for introducing surface roughness and UV-blocking properties. However, to inhibit ZnO particles’ photocatalytic degradation of peripheral organic materials, we conducted layer-by-layer (LbL) deposition with poly(sodium 4-styrenesulfonate) and poly(diallyl dimethyl ammonium chloride) to fabricate ZnO particles with an SiO₂ shell with tetraethyl orthosilicate. Polylactide (PLA) films were prepared by compression molding and treated with a weak alkali solution for 0.5, 1.0, 1.5, and 2.0 h to induce hydroxyl and carboxyl groups. The LbL deposition of polyelectrolytes on the PLA film was performed to induce electrical interactions between the PLA films and ZnO composite particles. ZnO composite particles were deposited onto the surface of the PLA films with dip coating, and a stable superhydrophobic surface was developed after hexadecyl trimethoxysilane treatment via a reduction in the surface energy. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47760.     

Nano polyurethane based surface modification on the anti-felting functionalization of wool fabrics

Nano polyurethane (Nano PU) was used for the fabrication of multilayer nanocomposite film deposition on wool fabrics by electrostatic self-assembly to improve the anti-felting properties. Oppositely charged cationic poly (diallyldimethylammonium chloride) (PDDA) and anionic Nano PU were alternately deposited on the surface of wool fabrics. 8, 12 and 16 multilayer films of PDDA/Nano PU were deposited on the wool fabric surfaces using a padder. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (FTIR-ATR) and Scanning Electron Microscopy (SEM-EDX) were used to verify the presence of deposit nanolayers. Breaking strength, whiteness and yellowness value analysis was performed on the fabrics before and after the treatment with Nano PU by the electrostatic self-assembly method. The build-up of the multilayer films and the level of colour strength (K/S) achieved are discussed after the acid dyeing process. To examine the anti-felting properties of the multilayered fabrics, the fabric shrinkage after washing was determined.     

Chain extension studies of water-borne polyurethanes from methyl ethyl ketoxime/-caprolactam-blocked aromatic isocyanates

A series of water-based blocked aromatic polyurethane dispersions (BPUDs) were prepared by prepolymer mixing process, using toluene 2,4-diisocyanate (TDI), 4,4′-di-p-phenylmethane diisocyanate (MDI), poly (oxytetramethylene) glycol (PTMG), dimethylol propionic acid (DMPA), methyl ethyl ketoxime (MEKO) and -caprolactam (CL). Particle size, viscosity, pH, molecular weight, storage stability, and de-blocking temperature of the BPUDs were measured and compared. Chain extension of BPUD was carried out with three types of chain extenders, hexamethylene diamine (HMDA), isophorone diamine (IPDA) and tetraethylene pentamine (TEPA), at various de-blocking temperatures. Tensile and thermal properties of the chain extended BPUD films were investigated and results confirmed that MEKO-BPUDs de-blocked at lower temperature than -caprolactam-BPUDs. The T_g values of the chain extended BPUDs were higher than those of the BPUDs and pure PTMG. Improvement in the thermal stability confirmed the de-blocking and chain extension reaction of blocked PU prepolymers.     

Use of anionic polysaccharides for the preparation of insulin-containing layer-by-layer films and their pH stability

Insulin-containing layer-by-layer (LbL) thin films were prepared by an alternate deposition of insulin and anionic polysaccharides (heparin, ??-carrageenan, and fucoidan) through an electrostatic force of attraction between positively charged insulin and anionic polysaccharides at pH 3.0. The loading of insulin in the LbL films increased with the increasing number of layers (or the film thickness), depending on the polysaccharide type. LbL films composed of ??-carrageenan contained higher amount of insulin than in heparin- and fucoidan-based films. The LbL films were fairly stable in acidic media, while insulin was released from the films in weakly acidic and neutral solutions as a result of loss of net positive charge in insulin. The released insulin retained its original structure.     

Improved biocompatibility of parylene‐C films prepared by chemical vapor deposition and the subsequent plasma treatment

The purpose of this study is to prepare the thin film of C‐type parylene (C‐type polyxylylene, parylene‐C) with improved biocompatibility for the biomedical applications, since in spite of the popularity, the parylene‐C has been known to have the less biocompatibility than the N‐type or D‐type parylene. To prepare the well‐designed parylene films through the chemical vapor deposition (CVD) process and the subsequent plasma surface treatment, the parameters of deposition and surface modification were controlled to obtain optimized physical and surface properties. Using CVD, the thin films of parylene‐C as thick as 5 μm were prepared under different deposition pressures. When increasing the deposition rate of parylene film or the deposition pressure, the tensile strength of film increased, whereas the properties such as the surface contact angle and permeability, and the elongation decreased. The deposition rate could be controlled to optimize the physical and physiochemical properties of films. The hydrophilicity of the parylene‐C film increased after plasma surface treatment by showing the larger water contact angle than untreated one. When the radio frequency power was above 100 W in the plasma process, the thin film obtained reveals an excellent cytotropism. It shows the improved biocompatibility with living cells. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of metallic seed layers on the properties of nanocrystalline diamond films

Three metallic films (Mo, Ti and W) were sputtered on Si substrates and ultrasonically seeded in diamond powder suspension. Nanocrystalline diamond (NCD) films were deposited using a dc arc plasma jet CVD system on the seeded metallic layers and, for comparison, a seeded Si without any metallic layer. The effect of metallic seed layers on the nucleation, microstructure, composition and mechanical properties of NCD films was investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and nanoindentation. We found that the metallic seed layers were transformed into metallic carbide or/and metallic silicide during the deposition of NCD films at high temperature. Adding metallic seed layers had no obvious effect on the bonding structure of the NCD films but significantly improved their surface roughness and mechanical properties. The NCD film deposited on W seed layer displays the lowest root-mean-square roughness of 19 nm while that on Ti seed layer has the highest compactness, hardness and elastic modulus.