Plasma-induced Graft Polymerization Research Articles

Plasma-Induced Graft Polymerization for the In Situ Synthesis of Cross-Linked Nanocoatings

Plasma-Induced Graft Polymerization for the In Situ Synthesis of Cross-Linked Nanocoatings

TPU with outstanding wettability and hydrophilic stability is obtained by plasma-induced graft polymerization

Hydrophilic thermoplastic polyurethane (TPU) is applicable in the fields of packaging, oil–water separation, and biomedical. Nevertheless, the process of its preparation is still a great challenge. The objective of this study is to develop TPU with excellent wettability and hydrophilic stability by surface modification. Four methods were evaluated: coating with PVP (polyvinylpyrrolidone) solution, immersion in PVP solution, N2/Ar plasma treatment, and N2/Ar plasma-induced graft polymerization with PVP. Finally, the results indicate that the sample called TPU-g-PVP, which utilizes plasma-induced grafting, exhibits the best performance. The water contact angle (WCA) reduces from 109° to 9.2°, and maintains within 20° after 80 days under atmospheric conditions. Its surface energy (72.4 mN/m) is increased by 2.8 times than untreated TPU. The surface morphology and roughness are almost unchanged when compared to the original TPU. Some characteristic peaks (–OH and C = O) of PVP on the TPU-g-PVP were found by infrared spectroscopy. X-ray photoelectron spectroscopy (XPS) examination revealed a reduction in C on the TPU surface as the content of N and O increases. Experiments on biocompatibility showed that the PVP deposited substrates improved cell adherence without generating new cytotoxicity.

Antibacterial Modification of Cotton Fabric Through Argon Plasma-Induced Grafting Polymerization

Antibacterial Modification of Cotton Fabric Through Argon Plasma-Induced Grafting Polymerization

Femtosecond laser texturing assisted cold plasma hydrophilization of polytetrafluoroethylene surface

Polytetrafluoroethylene (PTFE) is one of the most widely used engineering polymers, but PTFE-based bonding pairs are prone to failure due to its natural hydrophobicity induced weak interfacial bonding strength. Herein, we propose to improve the hydrophilicity of PTFE surface by femtosecond laser texturing assisted cold plasma modification. Specifically, PTFE surface is firstly textured by femtosecond laser ablation, and then modified by either direct cold plasma treatment or cold plasma induced graft polymerization of acrylic acid. The synergetic treatment roughens the PTFE surface on both micro and nano scales and introduces a large amount of oxygen-containing groups, making the treated surface hydrophilic (water contact angle < 30°). The hierarchically rough and hydrophilic PTFE surface favors its bonding with Cu by forming a mechanically interlocked and robust adhesive interface, and the maximum shearing strength and peeling strength of the bonding pairs were measured to be 2.75 MPa and 6.37 N/mm, respectively. The laser texturing assisted plasma modification enables durable surface hydrophilization and adhesive property improvement for PTFE compared with other previously reported methods, and thereby offers new insights into the fabrication of high-performance PTFE-based bonding components, as well as other functional units that require high-efficiency surface hydrophilization and robust bonding.

Preparation of a poly(2-acrylamido-2-methyl-1-propanesulfonic acid)-grafted polyurethane sponge using atmospheric pressure plasma-induced graft polymerization and its catalytic properties for the acetalization of glycerol to solketal

Poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (poly(AMPS)) bearing a sulfo group was grafted onto a polyurethane sponge by an argon atmospheric-pressure plasma treatment and subsequent graft polymerization. Thus, a novel poly(AMPS)-grafted polyurethane sponge was developed as a heterogeneous acid catalyst for organic synthesis. The average grafting amount was 0.0277 kg-polymer/kg-substrate. The surface properties of the polyurethane sponge changed considerably, from hydrophobic to hydrophilic. The poly(AMPS)-grafted sponge successfully catalyzed the acetalization of glycerol with acetone to produce the desired solketal. The reaction rate was analyzed using a pseudo-first-order kinetic model, and the apparent reaction rate constant, k, and apparent activation energy were determined. The k value for the poly(AMPS)-grafted sponge was one order of magnitude larger than that for the EDGA-co-AMPS gel (EDGA: ethoxy diethyleneglycol acrylate). The poly(AMPS)-grafted sponge with interconnected submillimeter-sized macropores and high porosity (98%) exhibits excellent diffusional permeability. In addition, the structural features of the sponge provide advantages such as a negligible pressure drop and easy handling during the reaction process. This study provides a strategy for the use of polymers grafted onto sponges as catalysts.

Fabrication of asymmetric wettability silk fabrics with plasma-induced grafting polymerization of octamethylcyclotetrasiloxane

Most superhydrophobic surfaces contain fluorine, which is very harmful to the environment. So, it is necessary to change the situation. This paper explains that a simple and fluorine-free plasma technology for superhydrophobic modification of silk fabrics by using one-sided protection method and low-temperature plasma induced grafting polymerization of octamethyl-cyclotetrasiloxane (D4) to form the superhydrophobic films. Treated silk and pristine silk fabrics were measured using field emission scanning electron microscopy(FESEM), Fourier-transform infrared spectroscopy(FTIR), X-ray photoelectron spectroscopy(XPS), and water contact angle measurement. The test results showed that the polymer films could be successful coated on the silk fibers surface via the low-temperature plasma. In addition, it has good durability, thermal stability, and a water contact angle of 152°.

Calcium Sulfate and Calcium Carbonate Scaling of Thin-Film Composite Polyamide Reverse Osmosis Membranes with Surface-Tethered Polyacrylic Acid Chains.

The gypsum and calcite scaling propensities of the thin-film composite polyamide (PA-TFC) reverse osmosis (RO) membrane, modified with a tethered surface layer of polyacrylic acid (PAA) chains, was evaluated and compared to the scaling of selected commercial RO membranes. The tethered PAA layer was synthesized onto a commercial polyamide membrane (i.e., base-PA) via atmospheric pressure plasma-induced graft polymerization (APPIGP). The PAA nano-structured (SNS) base-PA membrane (SNS-PAA-PA) was scaled to a lesser degree, as quantified by a lower permeate flux decline and surface imaging, relative to the tested commercial membranes (Dow SW30, Toray SWRO, and BWRO). The cleaning of gypsum-scaled membranes with D.I. water flushing achieved 100% water permeability recovery for both the SNS-PAA-PA and Dow SW30 membranes, relative to 92-98% permeability restoration for the Toray membranes. The calcium carbonate scaling of SNS-PAA-PA membranes was also lower relative to the commercial membranes, but permeability recovery after D.I. water cleaning was somewhat lower (94%) but consistent with the level of surface scale coverage. In contrast, the calcite and gypsum-scaled membrane areas of the commercial membranes post-cleaning were significantly higher than for the SNS-PAA-PA membrane but with 100% permeability recovery, suggesting the potential for membrane damage when mineral scaling is severe.

Plasma-Induced Graft Polymerization of Polyethylenimine onto Chitosan/Polycaprolactone Composite Membrane for Heavy Metal Pollutants Treatment in Industrial Wastewater

The present study manifests an innovative and green approach to graft metal ion adsorbent, polyethylenimine (PEI), onto an electrospun chitosan (CS)/polycaprolactone (PCL) composite membrane via atmospheric pressure nitrogen plasma grafting polymerization. FTIR absorption peak at around 1690 cm−1 was attributed to the bending vibration of N-H from PEI. Since the plasma exposure time is a dependent factor of –NH bond formation, an increased nitrogen content up to 3.3% was observed with an extensive reaction time under plasma treatment. In addition, N1s spectra showed a clear PEI dominating characteristic at 401.7 eV, which suggested a successful grafting of PEI onto the CS/PCL membrane. According to the EDX analysis, a significant amount of copper ions was detected in PEI-CS/PCL membranes. This study showed that a greener wastewater treatment can be realized with the developed plasma synthesis technology.

A thermoresponsive valve to control fluid flow in microfluidic paper-based devices

Microfluidic paper-based analytical devices (μPADs) have recently attracted the attention of researchers and industry owing to their various advantages. However, µPADs lack a way to control fluid flow; therefore, it is difficult to perform complex immunoassays that use multiple reagents and replace the reagents from the analytical area. We developed a controllable thermoresponsive valve for μPADs by functionalizing a polyvinylidene difluoride porous membrane with plasma-induced graft polymerization of poly(N-isopropylacrylamide) (PNIPAAm), which is a thermoresponsive polymer that changes its hydrophilic properties near the lower critical solution temperature (LCST; 32 °C). Surface analysis by attenuated total reflectance Fourier transform infrared spectroscopy confirmed that the fabricated thermoresponsive valves coated with PNIPAAm. The valve performance was evaluated by sandwiching the thermoresponsive valve between two paper microchannels stacked in a T-shaped paper microfluidic device. The thermoresponsive valve fabricated with a monomer concentration ranging from 2.3 to 3.0 wt% and a polymerization time of 5 h or 2.0 wt% and 20–22 h showed good valve performances. These valves were able to stop the flow at room temperature, and allow the flow by opening within 20 s after heating was initiated using a Peltier element located just under the valve. The valve was successfully closed, thereby stopping the flow, and opened by heating. Although a detailed evaluation of the fluid behavior is necessary, we have demonstrated that our thermoresponsive valve can be opened and closed reversibly by temperature control. We believe that this thermoresponsive valve could potentially be used to control the flow of multiple reagents in µPADs.

Scale up of polyamide reverse osmosis membranes surface modification with tethered poly(acrylic acid) for fabrication of low fouling spiral-wound elements

Scale up of atmospheric pressure plasma-induced graft polymerization (APPIGP) was demonstrated for surface nano-structuring (SNS) of a base polyamide (PA) reverse osmosis (RO) membrane with tethered poly(acrylic acid) (PAA) chains. Large SNS-PAA-PA membrane sheets, measuring 76.2 cm × 60.9 cm, were synthesized and used to fabricate small spiral-wound low fouling seawater RO elements (2.5 in. × 21 in.). The SNS-PAA-PA membrane sheets were of high spatial uniformity with respect to both water permeability and salt rejection. Lower SNS-PAA-PA membrane fouling propensity, relative to commercial membranes, was demonstrated in BSA and sodium alginate fouling tests of both membrane coupon and spiral-wound elements. Permeability recovery, upon water flushing of the fouled SNS-PAA-PA spiral-wound membrane elements was complete. Complete permeability recovery was also achieved for the sodium alginate fouled Dow SW30 element upon water flushing; however, permeability recovery was lower (91.6%) for the BSA fouled element, thus suggesting the need for added chemical cleaning. The study results suggest that APPIGP process scale up is feasible for fabrication of commercial-scale low fouling spiral-wound RO elements. However, further scale up toward continuous APPIGP will be required for larger size elements and automated element fabrication should be employed to minimize membrane and element construction imperfections.

Reversible Thermo-Responsive Valve for Microfluidic Paper-Based Analytical Devices.

Fluid control on a paper channel is necessary for analysis with multiple reagents, such as enzyme-linked immunosorbent assay (ELISA) in microfluidic paper-based analytical devices (µPADs). In this study, a thermo-responsive valve was fabricated by polymerizing N-isopropylacrylamide on a PVDF porous membrane by plasma-induced graft polymerization. The polymerized membrane was observed by scanning electron microscopy (SEM), and it was confirmed that more pores were closed at temperatures below 32 °C and more pores were opened at temperatures above 32 °C. Valve permeability tests confirmed that the proposed polymerized membrane was impermeable to water and proteins at temperatures below 32 °C and permeable to water at temperatures above 32 °C. The valve could also be reversibly and repeatedly opened and closed by changing the temperature near 32 °C. These results suggest that plasma-induced graft polymerization may be used to produce thermo-responsive valves that can be opened and closed without subsequent loss of performance. These results indicate that the thermo-responsive valve fabricated by plasma-induced graft polymerization could potentially be applied to ELISA with µPADs.

Enhanced osteogenic activity and antibacterial performance in vitro of polyetheretherketone by plasma-induced graft polymerization of acrylic acid and incorporation of zinc ions.

Polyetheretherketone (PEEK) has been widely used in the fields of orthopedics and trauma, but weak osteointegration and bacterial infection affect its long-term stability and repair effects. Surface modification is an effective way to improve the osteogenic and antibacterial activity of PEEK implants. In the present study, a layer of acrylic acid (AA) polymer coating loaded with zinc ions (Zn2+) was constructed on the surface of PEEK (PEEK-AA-Zn) using a strategy of combining plasma-induced graft polymerization with a chemical immersion technique. Successful construction of the AA coating remarkably enhanced the hydrophilicity of PEEK, and effectively loaded and released Zn2+. In vitro cell culture using MC3T3-E1 preosteoblasts showed that the Zn2+ released from PEEK-AA-Zn promoted cell proliferation and elevated gene expression levels of alkaline phosphatase (ALP), osteocalcin (OCN) and bone sialoprotein (BSP). Antibacterial tests revealed that PEEK-AA-Zn efficiently inhibited the proliferation of Staphylococcus aureus (S. aureus). These results suggest that the combined method of graft polymerization and ion incorporation endows PEEK with excellent osteogenic and antibacterial activity, which provides a wide range of possibilities for developing PEEK implants with multifunctional properties for bone tissue repair.

Durable Flame-Resistant and Ultra-Hydrophobic Aramid Fabrics via Plasma-Induced Graft Polymerization

A durable flame-resistant and ultra-hydrophobic phosphorus–fluoride coating on aramid fabrics was achieved by plasma-induced graft polymerization. The aramid fabrics were activated and roughed through the low-pressure plasma firstly, which involves the sequential coating of a mixture of phosphorus–fluoride emulsion copolymer. When potentially exposed to flame or water, such a surface produces a dual effect in which it is intumescent and waterproof, successfully giving the coated fabrics flame-resistant ultra-hydrophobic bifunctional properties. Thus, adhesive coatings provide a convenient way to resolve the issue of washing durability of the coatings. The as-prepared fabrics last for 10 repeatable washing cycles without losing their flame resistance and superhydrophobicity, suggesting future applications as advanced multifunctional textiles. Compared to an untreated coating, its char length was less than 1 cm with no measurable after-flame or after-glow times, and its static water contact angle remained stable above 170°. Meanwhile, the control sample was unable to extinguish the fire with a damage length of 10.6 cm and a water contact angle of 100°. All the results indicate that plasma-reactive polar groups interact between phosphorus and fluorine elements, leading to an increased relative atom ratio P and F through Energy-Dispersive Spectrometer (EDS) spectra and XPS analysis, which inhibits the flammability and wettability.

Surface tailoring for poly(ester-urethane) scaffold via plasma radiation-induced graft polymerization of N-hydroxyethyl acrylamide

The synthesis of the poly(ester-urethanes) using poly(3-hydroxybutyrate) has gained increasing interest as scaffolds for use in tissue engineering despite their moderate hydrophobicity and biocompatibility. However, it is not yet known if the grafting of poly(N‐hydroxyethyl acrylamide) is suitable to improve the degree of hydrophilicity of the surface. This study aims to tailor the surface of these biopolymers by plasma-induced graft polymerization of N‐hydroxyethyl acrylamide. The synthesized specimens are characterized by Fourier-transform infrared spectroscopy, scanning electron microscope, atomic force microscope, and contact angle measurements. The cell viability and cytotoxicity of the samples are assessed through MTT and live/dead viability/cytotoxicity kit assays with pancreatic islet cells. Our findings suggest that the plasma-induced surface grafting increase the roughness and the wettability, and also improve the cell viability of the starting substrate.

Plasma-induced graft polymerization on the surface of aramid fabrics with improved omniphobicity and washing durability

Durable superomniphobic surfaces are desirable for their practical applications, including self-cleaning, non-fouling, protective clothing and the separation of liquids. The plasma-induced polymerization of environmentally friendly C6 from a perfluoralkyl methlacrylate copolymer emulsion, AG-E081, was performed and a durable omniphobic fabric was achieved. C6 is an ecological alternative to C8 (eight CF2 groups) fluorinated compounds, and it was thereafter successfully incorporated into aramid fabric to achieve a durable superomniphobic surface. The fabric became water and oil repellent with an extremely high water contact angle of 180°. As tested by the water spray AATCC test and hydrocarbon resistance test, the as-prepared fabric gained 100° (ISO 5) and grade number 4 respectively. Furthermore, the fabrics also showed significantly improved washing durability after ten washing cycles. By scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) tests, it is indicated that the durable superomniphobicity can be attributed to the roughness and activation of the aramid surface by the plasma pre-treatment, which induces more adsorption and chemical graft of the C6 copolymer.

Heparin molecularly imprinted polymer thin flm on gold electrode by plasma-induced graft polymerization for label-free biosensor

Heparin, a highly sulfated glycosaminoglycan, is an important biomaterial having biological and therapeutic functionalities such as anticoagulation, regeneration, and protein stabilization. This study addresses a label-free quartz crystal microbalance (QCM) biosensor for heparin detection based on a macromolecularly imprinted polymer (MIP) as an artificial recognition element. We demonstrate the novel strategy for MIP in the form of thin film on a gold (Au) electrode with the plasma-induced graft polymerization (PIP) technique. The procedure of PIP is as follows: (i) Hexamethyldisiloxane plasma-polymerized thin film (PPF) as a pre-coating scaffold of active species for PIP (post-polymerization) is deposited on an Au electrode. (ii) The PPF/Au electrode is soaked in an water solution containing heparin (template), (2-(methacryloxy)-ethyl)trimethylammonium chloride acrylamide (functional monomer), acrylamide, and N,N-methylenebisacrylamide (crosslinker). Double bonds of monomer and crosslinker attacked by residually active species in pre-coating PPF cause radical chain reaction. Consequently, a growing polymer network of 20 nm thickness of PIP-MIP thin film is formed and grafted on the PPF/Au surface. (iii) The PIP-MIP/PPF/Au is washed by sodium chloride solution so as to remove the template. Non-imprinted polymer (NIP) is carried out like the same procedure without a template. The AFM, XPS, and QCM measurements show that the PIP process facilitates macromolecularly surface imprinting of template heparin where the template is easily removed and is rapidly rebound to PIP-MIP without a diffusional barrier. The heparin-PIP-MIP specifically binds to heparin compared with heparin analog chondroitin sulfate C (selective factor: 4.0) and a detectable range of heparin in the presence of CS (0.1 wt%) was 0.001-0.1 wt%. The PIP-NIP does not show selectivity between them. The evaluated binding kinetics are association (ka = 350 ± 100 M−1 s−1), dissociation (kd = (5.0 ± 2.0) × 10−4 s−1), and binding (KD = 1.3 ± 0.6 μM) constants, demonstrating that the PIP-MIP as a synthetic antibody can be applied to analytical chemistry.

Fabrication of superhydrophobic cotton fabrics through wrapping silica with plasma-induced grafting polymerization

Cotton fabric is commonly used in daily life, but it is easily wetted and contaminated by liquid. Herein, we present a simple and environmentally friendly plasma technology for hydrophobic modification of cotton fabric. In order to endow superhydrophobicity to cotton fabric, helium plasma inducing graft polymerization of 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (D4Vi) was utilized to wrap SiO2 particles on cotton fabrics. Cotton fabrics were successively dipped in silica sol and D4Vi, then treated by plasma. Cotton fabrics before and after modification were characterized by using field emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and water contact angle measurement. The experimental results showed that the cotton-SiO2-D4Vi consisted of nanoscale SiO2 protrusions and low-surface-energy film polymerized by D4Vi. In addition, the one wrapped SiO2 of 161 nm presented excellent hydrophobicity, washing durability, and repellency toward different types of liquids with a water contact angle of 152°.

Construction and surface/interface behavior of bio-functional surface layer by microwave-excited Ar/H2O plasma-induced polyethylene glycol polymerization

Ar/H2O microwave-excited surface-wave plasma-induced grafting-polymerization and crosslinking technique was presented to construct a bio-functional surface layer. Optical emission spectroscopy was used to diagnose Ar/H[Formula: see text]O plasma. The surface/interface behavior especially the aging effect of hydroxyl groups over the grafted PEG spacer layer was investigated by measuring water contact angle and X-ray photoelectron spectroscopy. The results demonstrate that the addition of water vapor into Ar plasma can optimize the concentration of hydroxyl functional groups on surface; grafted PEG spacer layer can provide a long-term hydrophilicity of PU films, and alleviate the aging effect of hydroxyl functional groups.

Structural changes in HDPE produced by in-line plasma-pretreated reactive extrusion

Structure of high density poly ethylene (HDPE) was changed after Plasma-induced graft polymerization of methyl methacrylate (MMA) monomer onto HDPE. Continuous polymerization of monomer wetted HDPE pellets was carried out sequentially via in-line plasma pretreatment followed by reactive extrusion. It was influenced by plasma pretreatment times between 15 s and 120 s on degree of grafting and molecular structure of the extrudate. Maximum degree of grafting was limited to 6% after 30 s plasma pretreatment. The addition of dicumyl peroxide (DCP) increased the degree of grafting to 10% after 15 s of plasma treatment. Gel formation to levels in the range 3–5% was detected, increasing with plasma pretreatment time. The formation of long chain branched (LCB) architecture, of the extruded PMMA-g-HDPE, was confirmed by rheological test in oscillatory shear, which results in increases in low frequency storage and loss moduli and melt viscosity than that of neat HDPE, especially after DCP addition. Finally, formation of a fully crosslinked structure was observed after annealing at 210 °C for 1 h as evidenced by a change in rheological properties at lowest frequencies to solid-like behaviour. Such extensive crosslinking could be useful in producing high strength adhesive joints between HDPE and other materials.

Fabrication of pH-responsive hydrophilic/hydrophobic Janus cotton fabric via plasma-induced graft polymerization

Stimulus-response unidirectional liquid transportation has important applications in the field of smart membrane materials. However, existing materials capable of unidirectional liquid transportation are rare and lack of intelligent controller. A novel pH-responsive hydrophilic/hydrophobic fluorine-free Janus cotton fabric was successfully fabricated via two steps plasma-induced graft polymerization. The smart wetting behavior of this Janus cotton fabric was evaluated by the water contact angle (WCA) measurement. Moreover, the coated cotton fabric was found to exhibit unidirectional and pH-responsive liquid transportation properties.