Natural rubber latex LbL films: Characterization and growth of fibroblasts

The recent biomedical applications of natural rubber (NR) latex, mostly in dry membranes, have motivated research into novel, more noble uses of this low-cost biomaterial. In this article, we provide the first report on the fabrication of layer-by-layer (LbL) films of NR alternated with the polyelectrolytes polyethylenimine (PEI) and polyallylamine hydrochloride (PAH). Stable (PAH/NR)_n and (PEI/NR)_n LbL films displayed similar physicochemical properties, but differed in terms of film morphology according to atomic force microscopy (AFM) and scanning electron microscopy (SEM) data. Most significantly, (PEI/NR)₅ LbL films were made of smaller and flattened particles, which were not efficient for the growth and proliferation of normal human fibroblasts (NHF). In contrast, efficient NHF proliferation could be obtained with (PAH/NR)_n LbL films, with the fibroblasts exhibiting the expected elongated morphology. Furthermore, cell growth did not occur for cast films of NR, thus demonstrating the suitability of the LbL method for this biologically related application. The differences between the two polyelectrolytes illustrate the importance of the film architecture and morphology, which open the way for exploiting the molecular control inherent in the LbL technique for further applications of NR-containing films. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The effect of side chains on the reactive rate and surface wettability of pentablock copolymers by ATRP

The reactive rate and surface wettability of three pentablock copolymers PDMS‐b‐(PMMA‐b‐PR)₂ (R = 3FMA, 12FMA, and MPS) obtained via ATRP for coatings are discussed. Poly(dimethylsiloxane) (PDMS) is used as difunctional macroinitiator, poly(methyl methacrylate) (PMMA) as the middle block, while poly(trifluoroethyl methacrylate) (P3FMA), poly(dodecafluoroheptyl methacrylate) (P12FMA) and poly(3‐(trimethoxysilyl)propyl methacrylate) (PMPS) as the end block, respectively. Their reactive rates obtained by gas chromatography (GC) analysis indicate that 3FMA gains 8.053 × 10^?5 s^?1 reactive rate and 75% conversion, higher than 12FMA (4.417 × 10^?5 s^?1, 35%), but MPS has 1.9389 × 10^?4 s^?1 reactive rate and 96% conversion. The wettability of pentablock copolymer films is characterized by water contact angles (WCA) and hexadecane contact angles (HCA). The PDMS‐b‐(PMMA‐b‐P12FMA)₂ film behaves much higher advancing and receding WAC (120° and 116°) and HCA (60° and 56°) than PDMS‐b‐(PMMA‐b‐P3FMA)₂ film (110° and 106° for WAC, 38° and 32° for HAC) because of its fluorine‐rich surface (20.9 wt % F). However, PDMS‐b‐(PMMA‐b‐PMPS)₂ film obtains 8° hysteretic contact angle in WAC (114°–106°) and HAC (32°–24°) due to its higher surface roughness (138 nm). Therefore, the fluorine‐rich and higher roughness surface could produce the lower water and oil wettability, but silicon‐rich surface will produce lower water wettability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40209.     

Synthesis and properties of polyurethane‐urea‐based liquid bandage materials

To obtain ideal liquid bandage polymer materials, a series of polyurethane‐urea dispersions were synthesized from 4,4′‐diisocyanato dicyclohexylmethane (H₁₂MDI) and ethylene diamine with different molar ratio of polyol blend [polyethylene glycol (PEG, M_n = 2000 g/mol)/hydroxy terminated poly(dimethylsiloxane) (PDMS, M_n = ～ 550 g/mol)] and acetone/ethanol as a solvent. The effect of PDMS content in PEG/PDMS on the viscosity, mechanical properties, water contact angle/surface energy, insolubility in water (%), water absorption (%), equilibrium water content (%), and water vapor transmission rate (g m^?2 day^?1) of polyurethane‐urea films was investigated. As PDMS content increased, the water contact angle, insolubility in water, and tensile strength/elastic recovery of film sample increased; however, the surface energy, water absorption (%), equilibrium water content (%), and water vapor transmission rate (g m^?2 day^?1) of film sample decreased. By a wound‐healing evaluation using a full‐thickness rat model experiment, it was found that a wound covered with a typical polyurethane‐urea liquid bandage film (PD2 sample) was filled with new epithelium without any significant adverse reactions. These results suggest that the polyurethane‐urea‐based liquid bandages (samples: PD2 and PD3) prepared in this study may have high potential as new wound dressing materials, which provide and maintain the adequate wet environment required to prevent scab formation and dehydration of the wound bed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of block copolymers from PDMS macroinitiators

The synthesis of polystyrene‐b‐polydimethylsiloxane‐b‐polystyrene (PSt‐b‐PDMS‐b‐PSt) copolymers is described. Commercially available difunctional PDMS containing vinylsilyl terminal species was reacted with hydrogen bromide resulting in the PDMS macroinitiators. The terminal alkyl bromide groups were then used as initiators for atom transfer radical polymerization (ATRP) to produce block copolymers. Using this technique, triblock copolymers consisting of a PDMS centre block and polystyrene terminal blocks were synthesized. ATRP of St from those macroinitiators showed linear increases in M_n with conversion, demonstrating the effectiveness of ATRP to synthesize a variety of inorganic/organic polymer hybrids. Copyright © 2004 Society of Chemical Industry     

Morphology of poly(styrene‐block‐dimethylsiloxane) copolymer films

The morphologies of poly(styrene‐block‐di‐methylsiloxane) (PS‐b‐PDMS) copolymer thin films were analyzed via atomic force microscopy and transition electron microscopy (TEM). The asymmetric copolymer thin films spin‐cast from toluene onto mica presented meshlike structures, which were different from the spherical structures from TEM measurements. The annealing temperature affected the surface morphology of the PS‐b‐PDMS copolymer thin films; the polydimethylsiloxane (PDMS) phases at the surface were increased when the annealing temperature was higher than the PDMS glass‐transition temperature. The morphologies of the PS‐b‐PDMS copolymer thin films were different from solvent to solvent; for thin films spin‐cast from toluene, the polystyrene (PS) phase appeared as pits in the PDMS matrix, whereas the thin films spin‐cast from cyclohexane solutions exhibited an islandlike structure and small, separated PS phases as protrusions over the macroscopically flat surface. The microphase structure of the PS‐b‐PDMS copolymer thin films was also strongly influenced by the different substrates; for an asymmetric block copolymer thin film, the PDMS and PS phases on a silicon substrate presented a lamellar structure parallel to the surface at intervals. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1010–1018, 2007     

Sodium Dodecyl Sulfate (SDS)-Loaded Nanoporous Polymer as Anti-Biofilm Surface Coating Material

Biofilms cause extensive damage to industrial settings. Thus, it is important to improve the existing techniques and develop new strategies to prevent bacterial biofilm formation. In the present study, we have prepared nanoporous polymer films from a self-assembled 1,2-polybutadiene-b-polydimethylsiloxane (1,2-PB-b-PDMS) block copolymer via chemical cross-linking of the 1,2-PB block followed by quantitative removal of the PDMS block. Sodium dodecyl sulfate (SDS) was loaded into the nanoporous 1,2-PB from aqueous solution. The SDS-loaded nanoporous polymer films were shown to block bacterial attachment in short-term (3 h) and significantly reduce biofilm formation in long-term (1 week) by gram-negative bacterium Escherichia coli. Tuning the thickness or surface morphology of the nanoporous polymer films allowed to extent the anti-biofilm capability.     

Morphological and electrochemical properties of “polyelectrolyte multilayer films” made from polyaniline and ZnO nanoparticles: Deposition as films or as clusters?

Deposits made by the alternated deposition of polyaniline (PANI) and ZnO nanoparticles may offer interesting applications as nonvolatile memory devices owing to the specific properties of each constituent. The rectifying ratio of such devices may strongly depend on the PANI/ZnO interface and on the morphology of the (PANI/ZnO)_n or (PANI/ZnO)_n‐PANI films. In this article we show that even if the morphology of the PEI/PSS‐(PANI/ZnO)_n or of the PEI/PSS‐(PANI/ZnO)_n‐PANI films seems very heterogeneous on the basis of scanning electron micrographs, the deposits consist of clusters deposited on a continuous film. In addition, the deposits become impermeable to ferrocyanide anions after the deposition of n = 10 alternated deposition cycles, confirming the existence of a continuous and impermeable film below the observed clusters. Such deposits may find interesting properties as a nonvolatile memory device. POLYM. COMPOS. 34:1333–1341, 2013. © 2013 Society of Plastics Engineers     

Hydrophilic modification of a polyimide film surface

The surface of a polyimide [poly(biphenyl 3,3′,4,4′-dianhydride-p-phenylene diamine)] film was modified with an O₂ glow plasma and subsequent treatment with polyethyleneimine (PEI) and poly(maleic anhydride-co-vinyl methyl ether) (PMAVM). The density of peroxide groups formed on the surface after O₂ plasma exposure was determined with 1,1-diphenyl-2-picrylhydrazyl and was found to level off to 1.2 nmol/cm² within the plasma exposure time of 20-60 s. The peroxide groups formed were utilized to immobilize PEI covalently onto the plasma-treated polymer film. After that, PMAVM was immobilized on the surface through the formation of amide bonds between the amino groups of PEI and the anhydride groups of PMAVM. The water contact angle on the modified films showed that the hydrophilic durability of the PMAVM-PEI-modified polyimide film was superior to that of the polyimide film treated by O₂ plasma alone.     

Synthesis of novel poly(diphenylacetylene)s with both trimethylsilyl and alkyl groups: The effect of desilylation on gas permeability

Diphenylacetylenes having both a trimethylsilyl group and an alkyl group at para positions [Me₃SiC₆H₄CCC₆H₄R; R = Et (1a), n-Bu (1b), t-Bu (1c), n-C₈H₁₇ (1d)] and having only an alkyl group [PhCCC₆H₄R; R = n-Bu (1B), n-C₈H₁₇ (1D)] were synthesized and then polymerized with TaCl₅/n-Bu₄Sn catalyst to provide the corresponding poly(diphenylacetylene)s (2a, 2b, 2c, 2d, 2B, and 2D). The formed polymers except 2c afforded tough free-standing membranes by casting from toluene solutions. Desilylation reaction of the Si-containing polymer membranes (2a, 2b, 2d) was carried out with trifluoroacetic acid, and the desilylated polymer membranes (3a, 3b, 3d) were obtained. The permeability to O₂, N₂, and CO₂ were determined for the obtained polymer membranes. All the desilylated membranes showed lower gas permeability than the Si-containing counterparts. To clarify the effects of the desilylation further, CO₂ diffusivity, CO₂ solubility, and fractional free volume (FFV) of the polymer membranes were investigated. The FFV and CO₂ diffusivity decreased upon desilylation, while CO₂ solubility hardly varied.     

Langmuir and Langmuir-Blodgett (LB) films of poly[(2-methoxy,5-n-octadecyl)-p-phenylenevinylene] (OC1OC18-PPV)

A PPV derivative, poly(2-methoxy,5-(n-octadecyl)-p-phenylenevinylene) (OC₁OC₁₈-PPV), has been synthesized via the Gilch route and used to fabricate Langmuir and Langmuir-Blodgett (LB) films. True monomolecular films were formed at the air/water interface, which were successfully transferred onto different types of substrate. Using UV-visible absorption, FTIR, fluorescence and Raman scattering spectroscopies we observed that the polymer molecules were randomly distributed in the LB film, with no detectable anisotropy. This is in contrast to the anisotropic LB films of a previously reported PPV derivative, poly(2-methoxy-5-n-hexyloxy)-p-phenylenevinylene (OC₁OC₆-PPV), which is surprising because the longer chain of OC₁OC₁₈-PPV investigated here was expected to lead to more ordered films. As a consequence of the lack of order, LB films of OC₁OC₁₈-PPV exhibit lower photoconductivity and require higher operating voltage in a polymer light-emitting diode (PLED) in comparison with LB films of OC₁OC₆-PPV. This result confirms the importance of molecular organization in the LB film to obtain efficient PLEDs.     

Chain packing and phase transition of N-hexacosylated polyethyleneimine comb-like polymer: A combined investigation by synchrotron X-ray scattering and FTIR spectroscopy

In this paper, the chain packing and phase transition of comb-like polymer has been deeply analyzed with N-hexacosylated polyethyleneimine (PEI26C) as a template, fabricated through the reaction between n-hexacosyl bromide and PEI in a homogenous solution. The effect of long alkyl groups on the chain packing and phase transition of PEI26C was systematically investigated by synchrotron X-ray scattering and variable-temperature FTIR spectroscopy. PEI26C comb-like polymer exhibited an interesting structure-evolution process, and phase transformation from orthorhombic (β_O), monoclinic (β_M), to hexagonal (α_H) phase, and finally to amorphous state was demonstrated, indicating that large alkyl domains induced the complicated structures. Size-depended phase transition behavior provides an insight into the formation of metastable structure during the early stage of polymer crystallization.     

Laser Desorption Ionization Time‐of‐Flight Mass Spectrometry of Glasses and Amorphous Films from Ge–As–Se System

Laser Desorption Ionization Time‐of‐Flight Mass Spectrometry was exploited for the characterization of Ge–As–Se chalcogenide glasses and corresponding thin films fabricated using pulsed laser deposition. Main achievement of the paper is the determination of laser generated clusters’ stoichiometry. The clusters observed were As_b⁺ (b = 1–3), Se₂^?, binary As_bSe⁺ (b = 1–3), As_bSe_c^? (b = 1–3, c = 1–4), Ge₂Se_c^? (c = 2–3), As₃Se₂⁺, Ge₂As_b^? (b = 2–3), Ge₃As_b^? (b = 1–2), Ge₃Se₄^?, As₅Se_c^? (c = 4–5), GeAsSe₄^?, Ge_aAsSe₅^? (a = 1–4), GeAs₂Se₃^?, GeAs₃Se₂^?, Ge₂As₂Se₂^?, Ge₂AsSe_c^? (c = 6–7), and GeAs₃Se_c^? (c = 5–6) (in positive as well as in negative ion mode). The stoichiometries of identified species are compared with the structural units of the glasses/thin films revealed via Raman scattering spectra analysis. Some species are suggested to be fragments of bulk glass as well as thin films. Described method is useful also for the evaluation of the contamination of chalcogenide glasses or their thin films.     

Preparation and characterization of new nanocomposite polymer films containing NiO nanofillers

Nanocomposite solid polymer films based on the poly(exo‐N‐phenyl‐7‐oxanorbornene‐5,6‐dicarboximide) (PPhONDI)/LiClO₄/NiO system have been designed, and the effect of inorganic NiO nanofiller in different amounts on the film properties has been examined. The exo‐PPhONDI/LiClO₄/NiO polymer system is the first solid nanocomposite polymer electrolyte film example based on a ring‐opening metathesis polymerization (ROMP) host polymer. The NiO nanoparticles were prepared by two‐step chemical syntheses, and the thermoplastic host polymer, exo‐PPhONDI, was synthesized via ROMP. Composite polymer films were prepared by the solution‐casting method. The amount of nanoparticles was varied from 1 to 15 wt % of NiO. The conductivity of the nanocomposite solid polymer systems was influenced by the NiO nanofiller concentration. The composite films based on exo‐PPhONDI ROMP polymer with the highest conductivity were achieved for the composition with 8 wt % of NiO nanofiller and 10 wt % of LiClO₄ dopant. The prepared films were characterized using X‐ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy (SEM). The SEM results showed that the filler was well distributed in the polymer matrix. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45938.     

Effect of Cu2O thin film on Cu–Sn alloy coated steel surface in promoting interfacial adhesion with rubber

In the present study, effect of Cu₂O film deposited via successive ionic layer adsorption and corresponding chemical reaction (SILAR method) on Cu–Sn coated steel substrate was explored for the purpose of improving the adhesion of steel with rubber. The effect of the relative alkali concentration in the oxide film deposition bath and the number of immersion cycles on the interfacial adhesion affecting the nature of oxide film deposited, its thickness and surface coverage were investigated. In the current study, Cu–Sn coated steel bead wire with coated surface roughness (R_a) around 2 μm showed an improvement of 33% in adhesion (in terms of pull out force) with an optimum alkali/Cu ion concentration of 25:1 with single dipping cycle attributed to an optimum oxide coating thickness of ~70 nm. Surface morphology study exhibited formation of thicker coating with increase in number of dipping cycles. Satisfactory thermal stability of the Cu₂O film was confirmed as no re-oxidation of the Cu₂O film to CuO was observed in the 200 °C heat treated samples.     

Influence of Substrate Properties on the Dewetting Dynamics of Viscoelastic Polymer Films

We studied the dewetting process of thin polystyrene (PS) films on silicon substrates, coated with a thin, irreversibly adsorbed polydimethylsiloxane (PDMS) layer, by optical microscopy and atomic force microscopy. Besides demonstrating the exceptional potential of dewetting for a sensitive characterization of rheological properties of PS thin films, characterized by a stress-relaxation time, τ₁, we focused on the influence of the frictional behaviour (energy dissipation mechanism) at the interface between the PDMS-coated silicon wafer and the PS film on the dewetting process. Our results show that the initial stages of dewetting depend sensitively on the thickness and the way the PDMS layer was adsorbed. The maximum width of the dewetting rim at τ₁ increased with increasing PDMS layer thickness, which can be interpreted as an increase of the effective, velocity-dependent slippage length. Interestingly, τ₁ was found to be almost independent of the substrate properties. Our results demonstrate that dewetting is a really powerful approach for rheological and frictional studies of thin polymer films.     

Improved High-Temperature Energy Storage Performance of PEI Dielectric Films by Introducing an SiO2 Insulating Layer

Polymer dielectrics have the advantages of flexibility, good insulation, high power density, etc., which are widely used in the fields of pulsed power and power electronics. However, the conduction loss increases sharply at elevated temperature, which leads to the severely degraded energy storage performances and limits the polymer dielectric films to be used at elevated temperature. To address this issue, the SiO₂ layer is grown on both side of polyetherimide (PEI) films by magnetron sputtering technology, the SiO₂/PEI/SiO₂ composite films with a sandwiched structure are successfully constructed. The results show that by growing a wide band gap SiO₂ layer between the PEI film and the metal electrode can improve the height of the potential barrier at the electrode/dielectric interface, thus effectively reducing the conduction loss. The maximum discharge energy density is 2.96 J cm⁻³ when the charge–discharge efficiency is above 90%, which outperforms the reported dielectric polymers and composites. In addition, combining with the cycling charging/discharging results, SiO₂/PEI/SiO₂ composite films are demonstrated to have significant long-term reliability and excellent discharging capability at elevated temperature.     

Phase separation of poly(ether sulfone imide) modified epoxy resin

Poly(ether sulfone imide)s (PEI) with molecular weight M_n ∼ 10⁴ were synthesized from 3,3′,4,4′-benzophenone tetracarboxylic dianhydride and amine terminated poly(ether sulfone) having molecular weights ranging from M_n ∼ 400 to M_n ∼ 4000. Thus, the PEIs had the same molecular weight but various imide and ether sulfone contents. The PEIs were mixed with a stoichiometric mixture of diglycidyl ether bis-phenol-A (DGEBA)/diamino diphenyl sulfone (DDS). The effect of PEI on the curing reaction of DGEBA/DDS and the morphology of the polymer blend were studied by differential scanning calorimetry (DSC) and optical microscopy. In the DGEBA/DDS/PEI blend with a fixed PEI molecular weight and PEI concentration but with various imide content, the experimental data revealed the PEI with a higher content of ether sulfone had a lower T_g and a better compatibility with solvents and epoxy resins; the curing reaction rate of DGEBA/DDS/PEI was faster for PEI with a higher imide content; the DSC data of cured DGEBA/DDS/PEI showed two T_gs, indicating phase separation between PEI and cured epoxy resins; and the data of optical microscopy showed that the compatibility of PEI with epoxy resins increased with the content of ether sulfone in PEI. © 1996 John Wiley & Sons, Inc.     

Surface characterization of polyethersulfone by inverse gas chromatography

Summary In this work, the surface properties of polyethersulfone (PES) were analyzed by inverse gas chromatography (IGC). Five n-alkanes (n-C₆, n-C₇, n-C₈, n-C₉, and n-C₁₀) were chosen as apolar probes to characterize the surface dispersive free energy at different temperatures. Acetone (Acet), dichloromethane (DCM) and tetrahydrofuran (THF) were chosen as polar probes to detect the Lewis acid-base parameters, i.e. the Lewis acidic number K_a and Lewis basic number K_b. It was found that the surface dispersive free energy was 32.09, 30.41, 28.52, and 27.21 mJ/m² at 60, 70, 80, and 90 °C, respectively. The Lewis acidic number K_a is 0.086 and Lewis basic number K_b is 1.523. Compared with other polymers characterized by IGC, the PES belongs to a strong basic polymer material.     

Optimization of high temperature energy storage properties of PEI-based composite dielectric based on rapid in-situ growth of inorganic functional layer

The serious deterioration of the energy density of polymer energy storage dielectrics in high temperature environment is the main reason to curb the in-depth application of dielectric film capacitors in the field of modern electrical and electronic engineering. Here, aiming at the problem of low dielectric constant of polymer dielectric, a simple, low-cost method is proposed to grow inorganic polar functional layer on surface of polymer film in situ, which effectively improves the polarization characteristics of polymer dielectric at high temperature. The in situ growth of Ti(OH)₄ inorganic polar functional layer on surface of polyetherimide (PEI) film noteworthy to improve the energy storage performance of dielectric film. The energy storage density of 4.59 J/cm² is obtained at 150°C and 600 MV/m, which is 1.18 times that of PEI film under the same condition. The significant enhancement of high temperature energy storage density can be attributed to introduction of functional layer, which effectively improves the dielectric properties and polarization intensity of dielectric film. Furthermore, the facile preparation method provided in this paper can be applied to various thin films under the premise of controllable cost, which is of great significance to improve the high temperature energy storage characteristics of polymer dielectric.