Surface Hydrophilicity Of Films Research Articles

Evaluation of the Modification Effects of Heparin/Dalteparin on Silk Fibroin Structure and Physical Properties for Skin Wound Healing.

We have developed a functionalized silk fibroin (BSF) that can serve as an improved fundamental material for dressings by specifically capturing growth factors secreted during the healing process and supplying them to cells accumulated in the wound area to enhance the tissue regeneration efficiency. When considering the design of heparin-modified BSF, there is a difficulty with binding to high-molecular-weight polysaccharides without disrupting the hydrophobic crystalline structure of the BSF. In this study, a low-molecular-weight pharmaceutical heparin, dalteparin, was selected and cross-linked with the tyrosine residue presence in the BSF non-crystalline region. When targeting 3D porous applications like nanofiber sheets, as it is crucial not only to enhance biological activity but also to improve handling by maintaining stability in water and mechanical strength, a trade-off between improved cell affinity and reduced mechanical strength depending on crystalline structure was evaluated. The use of dalteparin maintained the mechanical strength better than unfractionated heparin by reducing the effect on disturbing BSF recrystallization. Film surface hydrophilicity and cell proliferation induction were significantly higher in the dalteparin group. For BSF functionalization, using purified heparin was an effective approach that achieved a balance between preserving the mechanical properties and induction of tissue regeneration, offering the potential for various forms in the future.

Effect of treatment time and radio frequency power on roughness and wettability of oxygen plasma-etched Cadmium Telluride thin films

The thermal evaporated Cadmium Telluride (CdTe) on Indium tin oxide substrates was etched using Oxygen plasma at various treatment times and radio frequency (RF) power. The roughness and wettability parameters were calculated using atomic force microscopy and contact angle (CA) analysis. The morphology evolution increases the interface width w and the lateral correlation length ξ with etching time and RF power. The local roughness exponent near-0.5 shows the self-affine of the surface during the etching process. The obtained experimental exponents in the present work introduce the universality class of the scaling exponents. The surface hydrophilicity of films was studied using the measurement of the two droplets CA on the film surface and the surface energy. The physical and chemical structure of the surface affected by oxygen plasma causes the surface to become more rough and hydroxyl group formation. Infra-Red spectra of the untreated and etched films using Fourier transform infrared spectroscopy confirmed the presence of the CdTe bond and a hydroxyl group. The wettability behavior of the etched films demonstrated the transition from the Cassie-Baxter state to the Wenzel state. Results show surface energy of the etched films increases, and theirs become hydrophilic.

EVALUATION OF POLY(VINYL ALCOHOL) ADDITION EFFECT ON NANOFIBRILLATED CELLULOSE FILMS CHARACTERISTICS

ABSTRACT In this study, based on the mechanical shear treatment, the cellulosic pulp was fibrillated in nanofibrils dispersed in aqueous suspension. Nanofibrillated Cellulose (NFC) matrix - Polyvinyl Alcohol (PVA) nanocomposite films’ were prepared by casting from NFC/PVA suspension mixtures. The thermal and mechanical properties of the obtained films were evaluated. Low levels (2, 5 and 10 wt%) of PVA were used as an additive in a nanofibrillated cellulose (NFC) matrix. The predominant use of NFC, with superior properties due to its purity, with an efficient and environmentally friendly method, has allowed the production of NFC-based biodegradable materials with enhanced properties for high-level applications. The addition of PVA to the NFC matrix produced positive results, as it causes little aesthetic interference, without changes in surface brightness. After the addition of PVA the films showed a great gain in mechanical strength, increasing by 24% in Young’s modulus with the addition of 10% PVA. Even after addition, the samples’ chemical composition remains unchanged and the mixture shows a decrease in the film surface hydrophilicity when compared to pure NFC. Composite material thermal analysis indicates that thermal degradation temperatures remain unchanged after the addition of PVA. Although PVA is not very temperature resistant, in the proportions used, NFC thermal resistance is preserved.

Synthesis of a dripping agent based on lauric acid diethanolamide and delaying its migration in LLDPE films

ABSTRACTPolymeric films are increasingly used in greenhouse cultivation because dripping agents can improve the hydrophilicity of film surface. Here, we summarize a way to a new reactive type dripping agent, lauric acid diethanolamide monoacrylate (AAL), which was synthesized by using acrylic and lauric acid diethanolamide as main starting materials. As-prepared AAL was separately grafted onto linear low-density polyethylene (LLDPE-g-AAL) and layered double hydroxides (LDHs-g-AAL) to prevent it from migrating. Accelerated dripping experiment results showed that the dripping time of LLDPE/LDHS-g-AAL and LLDPE-g-AAL films at 60°C was prolonged to 16 and 12 days from 8 days of ungrafted one, respectively.

Incorporation of essential oils into pumpkin oil cake-based materials in order to improve their properties and reduce water sensitivity

Biopolymer-based materials present good alternatives for synthetic materials. However, their high water sensitivity may limit their usage for food products packaging. Addition of hydrophobic components into the material formulation could improve this property. In this work 3, 4 and 5 % (v/v) of Satureja montana or Ocimum basilicum essential oil was incorporated into biopolymer films based on pumpkin oil cake. The obtained materials were analyzed regarding mechanical, physicochemical, barrier and structural properties. Incorporation of the essential oils increased the thickness of the pumpkin oil cake film. Significant reductions in moisture sensitivity, related to physicochemical properties and water vapor transmission rate (almost for 30 %), were observed (p < 0.05). Improvement of light barrier properties was also observed so that the visible light transmission was decreased for around 50 % while the UV light transmission was lower than 1 %. The obtained FTIR spectra confirmed the presence of added essential oils in pumpkin oil cake films, as well as their influence on the reduction in the film surface hydrophilicity. However, mechanical properties, tensile strength and elongation at break, decreased significantly (p < 0.05). These results suggest that incorporation of Satureja montana or Ocimum basilicum essential oil improved barrier properties of pumpkin oil cake-based films and reduced the film affinity toward water.

Hybrid sol–gel thin films doped with a pH indicator: effect of organic modification on optical pH response and film surface hydrophilicity

Optical sensors for application in innovative wearable sensing systems such as textile-integrated systems and wireless sensor platforms rely on the development of low-cost multifunctional materials compatible with standard fabrication technologies. We are developing optically responsive pH sensitive sol–gel coatings for integration with a mobile wireless smart tag sensing system. For this application, we have fabricated a range of thin pH sensitive films using bromocresol green (BCG) indicator immobilised in inorganic–organic silica hybrid matrices prepared by a sol–gel method and deposited by spin-coating onto glass substrates. The surface hydrophilicity of the films were varied by using the inorganic sol–gel precursor tetraethoxysilane together with either methyltriethoxysilane, ethyltriethoxysilane, phenyltrimethoxysilane or glycidoxypropyltrimethoxysilane as organically modified sol–gel precursors, co-polymerised in different ratios. Spectral characterisation of the films was performed using visible absorption spectroscopy. The shift in absorption maxima and other spectral changes of the different matrices have been identified, and the apparent pK app values of the immobilised BCG pH indicator determined. The surface wettability properties of the films have been studied by measuring the contact angle of water, formamide and diiodomethane which has allowed the estimation of the surface free energy (SFE) using three different models: Owens–Wendt, Wu and van Oss-Chaudhury-Good. It is shown that the SFE of the hybrid films is directly related to the type and the degree of organic modification, which in turn has a significant effect on the pH response-time of these sensing films.

Surface modification of plasma‐pretreated expanded poly (tetrafluroethylene) films by graft copolymerization

A two‐step process based on a low‐pressure helium plasma treatment followed by acrylic acid‐grafting copolymerization was used for the surface modification of expanded polytetrafluoroethylene (ePTFE) films. The effects of plasma treatment power and treatment time on the hydrophilicity of the film surface were investigated. The wettability of the ePTFE film surface was characterized by water contact angle, and the surface compositions of the untreated and treated ePTFE samples were evaluated by atomic force microscopy and XPS. Contact angle measurements revealed that the hydrophilicity of the ePTFE film surface was greatly enhanced by the combined actions of the plasma treatment and acrylic acid grafting, and the contact angle decreased from 145° to 66°. Atomic force microscopy analyses showed that the surface roughness increased after the plasma treatment. XPS analyses showed substantial increase in the concentration of carbon and oxygen atoms and a decrease in the concentration of fluorine atoms at the film surface. T‐peel strength showed an improved bonding strength between the film and an adhesive tape after the treatment. Copyright © 2012 John Wiley & Sons, Ltd.

Plasma graft polymerization of Acrylic Acid and immobilization of Heparin to improve blood compatibility of Polyethylene terephthalate (PET).

ABSTRACTPolymeric materials have been attracted the attention of researchers in various R&D applications. In this research, attempts were made to evaluate the changes in blood compatibility of polyethylene terephthalate (PET) by grafting acrylic acid (AAc) and immobilizing heparin by employing two-step plasma treatment. The PET surface was modified by using a novel method named “two-step plasma treatments” (TSPT). While first plasma is creating active sites for grafting, the second plasma polymerizing pre-adsorbed reactive monomer onto the surface of films. Finally, heparin immobilization was performed in the presence of 1-ethyl-3-(dimethylaminopropyl) carbodiimide. All films were characterized by attenuated total reflection Fourier transformed infrared (ATR-FTIR) spectroscopy and scanning electron microscopy (SEM). The surface hydrophilicity of films was studied by water contact angle test and blood compatibility evaluated by Lactate dehydrogenase method (LDH Test). In vitro studies based on LDH results demonstrared that platelet adhesion onto the modified surfaces with heparin was drastically reduced in comparison with unmodified PET.

Surface modification of poly(tetrafluoroethylene) films via plasma treatment and graft copolymerization of acrylic acid

For surface modification of poly(tetrafluoroethylene) (PTFE), a two-step procedure based on a low-pressure plasma treatment followed by acrylic acid (AAc) grafting copolymerization was used. The influences of AAc concentration and grafting temperature on the hydrophilicity of film surface were studied. The wettability of the PTFE membrane surface was characterized by water contact angle, and the surface microstructures and compositions of the AAc-modified PTFE film were characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Contact angle measurements revealed that the hydrophilicity of the PTFE film surface was greatly enhanced by the grafting of the AAc chains, and the surface contact angle decreased from 126° to 64.8° after 6-h grafting of AAc under the condition of 30% (v/v) AAc at 70°C. The PTFE surface with a low contact angle was very effective in immobilization of chitosan. The amount of chitosan covalently immobilized on the carboxylic acid group-grafted PTFE was 64.5 μg/cm 2 membrane as determined with the ninhydrin method and the water contact angle further decreased with the immobilization of chitosan.

Electropolymerized Films Formed from the Amphiphilic Decyl Esters of d- and l-Tyrosine Compared To l-Tyrosine Using the Electrochemical Quartz Crystal Microbalance

Using the electrochemical quartz crystal microbalance (EQCM), we compared thin films formed on Pt by electropolymerization of l-tyrosine to that of the amphiphilic monomers, decyl esters of d- and l-tyrosine (DEDT and DELT). Mass build-up and film properties were determined as a function of monomer concentration via frequency, f, motional resistance, R, and charge passage, Q, measurements. Films were found to occur by a combination of monomer electropolymerization and adsorption for DEDT and DELT, but only by electropolymerization for l-tyrosine. This difference in film formation process for the monomers is reflected in the net mass build-up for each film, as represented by calculated df/dQ values. For the adsorbing monomers DEDT and DELT, films possessed concentration dependent df/dQ values, more than 100-fold greater than that for l-tyrosine film formation under equivalent electropolymerization conditions. During the entire film growth process, all three films exhibited no significant energy dissipation properties (DeltaR invariant). Concentration dependent adsorption of significant levels of unpolymerized but self-assembled DEDT and DELT monomers account for the subsequent time dependent mass loss observed from the films maintained in buffer in the absence of monomer. Contact angle measurements demonstrated a pH dependent increase in the surface hydrophilicity of films electropolymerized from the DEDT, DELT, and l-tyrosine monomers but not films formed from phenol and 3-nitrophenol monomers. This behavior is consistent with the monomers' known changes in titration/charge state properties with increasing pH. This study provided insight into the film formation, stability, and surface hydrophilicity resulting from electropolymerization of these related tyrosine based monomers. This information is critical to assessing the utility these films may have in the development of new biomaterials and as biological macromolecule or cell immobilization strategies in biosensors.