The surface characterization of mulberry silk grafted with acrylamide by plasma copolymerization

The effects of plasma-induced graft copolymerization and simultaneous plasma-treated graft copolymerization with acrylamide (AAm) on the structure of mulberry silk are investigated. Through scanning electron microscopy, transmission infrared (IR), and attenuated total reflectance-IR and x-ray photoelectron spectroscopy (XPS) studies, changes of the surface morphology, structure, and composition are observed. The results show that plasma-induced graft copolymerization has more influence on the original structure of silk than does simultaneous plasma-treated graft copolymerization. The former brings the AAm branch polymer into the main chain of silk by the initiation of some kind of oxygen and nitrogen groups formed by the plasma, but the latter directly forms the AAm branch or cross-linking polymers with oxygen and nitrogen groups on the silk surface. This is the reason for the high elastic recovery angle of silk fabric modified by the two plasma graft copolymerizations. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1713–1717, 1997     

Chemical grafting of curcumin at polyethylene terephthalate woven fabric surface using a prior surface activation with ultraviolet excimer lamp

Durable curcumin‐treated antibacterial polyethylene terephthalate (PET) fabrics (against Staphylococcus aureus) were produced by dyeing with curcumin after surface activation using vacuum ultraviolet excimer lamp at 172 nm. Surface change properties of the exposed fabrics were characterized by surface analysis methods such as wettability, atomic force microscopy, and X‐ray photoelectron spectroscopy. Results show an increase in surface hydrophilicity with a water contact angle of the PET fabric reaching 24° after 10 min excimer irradiation, which could be attributed to an increase in carboxyl group formation as confirmed by X‐ray photoelectron spectroscopy measurements. Varying concentrations of curcumin were immobilized onto untreated and vacuum ultraviolet‐irradiated PET samples using diffusion method at 90°C, and the treated fabrics characterized using K/S (color strength) values at 440 nm. K/S values increased when the PET surface was subjected to a prior excimer irradiation, because of grafting of curcumin at the PET surface. Increased excimer irradiation time increased grafting of curcumin because the inner fabric fiber surfaces were also more thoroughly treated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Study of unsaturated polyester and vinylester morphologies using excimer laser surface treatment

A technique based on the use of an ArF excimer laser (193 nm) to analyze the morphology of the unsaturated polyester and vinylester networks has been developed. This method is based on the use of the differences between the thresholds at which ablation of the various constituent phases of the materials occurs. After having determined the ablation threshold of a polystyrene, various surface treatments using excimer lasers fluence around this threshold were applied to unsaturated polyesters and vinylester. In the latter case, a two-phase structure consisting of microgels in a polystyrene phase was shown by scanning electron microscopy observations, allowing us to conclude that the mechanisms by which vinylester and unsaturated polyester networks are formed are similar. We also observed that the two-phase structure of the vinylester matrixes, unlike that of the unsaturated polyesters, is organized rather than random-structured, which could represent a major parameter contributing to the very good hydrolysis stability of these materials. In the event of degradation by osmotic mechanisms, the organized structure network would enable limiting of the development of the osmotic pressures by distributing the forces within the material, thus avoiding crazing. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1703–1714, 1997     

X‐ray photoelectron spectroscopic study of silk fibroin surface

X‐ray photoelectron spectroscopy (XPS) has been used to probe the nature of silk fibroin surface, in particular the tyrosine content and sulfur species on the surface. The iodine labelling treatment of silk, followed by XPS surface analysis, reveals that silk fibroin has a tyrosine‐enriched surface, and that there are sulfur‐containing amino acids present on the surface, mainly occurring in the S⁶⁺ component. UV/ozone treatment modifies/removes the surface tyrosine‐ and sulfur‐containing species. © 2002 Society of Chemical Industry     

Polymer surface modification due to excimer laser radiation—Chemical and physical changes in the surface structure of poly(ethylene terephthalate)

The effects on chemical and physical properties of PET (poly(ethylene terephthalate)) film surfaces as a result of microstructuring induced by KrF-laser (248 nm) radiation were investigated. On irradiation, the properties of film surfaces changed in proportion to radiation flux intensity. Close to threshold values, bulbous swellings appeared on the surface, which showed hydrophilic properties. At the threshold and above, regular rippling was seen, and the surface showed hydrophobic properties. Excimer laser irradiation induced chemical modification of the surface, decrease in the O/C ratio, dissociation of ester binding and amorphism as observed by X-ray-induced photoelectron spectroscopic and Fourier-transform infrared analysis.     

Micropatterning of polymethacrylates by single‐ or two‐photon irradiation using π‐conjugated o‐nitrobenzyl ester phototrigger as side chains

A new single‐/two‐photon sensitive monomer, (E)‐5‐(4‐ethoxystyryl)?2‐nitrobenzyl methacrylate (ENbMA), was synthesized and copolymerized with methyl methacrylate (MMA) to form a series of photosensitive copolymers P(ENbMA–MMA)s that were well characterized by ¹H NMR and GPC. The photochemical and photophysical properties of both photosensitive monomer and copolymers upon visible light irradiation were studied by UV–Vis, FTIR, and HPLC spectra, which confirmed that 5‐(4‐ethoxystyryl)‐2‐nitrobenzyl ester can be photolyzed effectively with generation of the corresponding 5‐(4‐ethoxystyryl)‐2‐nitrosobenzaldehyde and carboxylic acid groups. The successful photocleavage endowed the optimized copolymers with excellent micropatterning property due to the effective generation of alkaline‐soluble carboxylic acid groups. Moreover, the high two‐photon absorption cross‐sections (over 20 GM at 800 nm) and the comparable photolysis upon two‐photon NIR light irradiation of the chromophores provided the copolymers with significant application in two‐photon microfabrication. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4099–4106, 2013     

Polyimide surface modification by pulsed ultraviolet laser irradiation with low fluence

Surface modification on a polyimide film by pulsed ultraviolet (UV) laser irradiation with a fluence below its ablation threshold was studied by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and UV-vis spectroscopy. It was observed that a photochemical reaction occurred and hydrophilic groups, such as —OH and —COOH, formed on the polyimide surface after irradiation. In addition, a ripple microstructure formed on the surface when the angle of incidence of the laser beam was 20–50^o. The contact angle of the polyimide surface with water decreased and the adsorption ability of the surface to a water-soluble dye clearly increased after laser irradiation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2739–2743, 2001     

Optimization of ultrasound-assisted extraction of anthocyanins from mulberry, using response surface methodology

Mulberry is one of the most widely used traditional Chinese medicines. Anthocyanins are the main bioactive components of mulberry, and possess important biological activities, such as antimicrobial, anti-inflammatory and antioxidant activities. This study investigated the ultrasound-assisted extraction (UAE) of anthocyanins from mulberry by using response surface methodology (RSM). The extraction conditions associated with anthocyanin yield, including extraction solvent, liquid-to-solid rate, temperature and extraction time, are discussed. The optimal conditions obtained by RSM for UAE from mulberry include 63.8% methanol contains 1% (v/v) trifluoroacetic acid (TFA), 43.2 °C temperature, 23.8 (v/w) liquid-to-solid ratio, and 40 min time for the maximum yield (64.70 ± 0.45 mg/g). The results indicated that the UAE can be an effective method for the extraction of some active components from plant materials.     

响应曲面法优化再生丝素蛋白/多壁碳纳米管共混水溶液静电纺丝工艺

再生丝素蛋白/多壁碳纳米管共混水溶液静电纺纤维毡可应用于组织工程支架。提高纤维毡的孔隙率即减小纤维的横截面尺寸有利于细胞的粘附和增殖,从而提高材料的应用性能。该文采用响应曲面法(RSM)优化再生丝素蛋白/多壁碳纳米管共混水溶液静电纺丝工艺,以减小纤维横截面尺寸。     

镀层表面形貌的分形维数定量表征

为了定量表征镀层表面的形貌特征,应用当代非线性科学新理论--分形几何学方法,研究了几种镀层的表面形貌,用表面分形维数定量表征了其表面形貌特征.结果表明,用像素点覆盖法计算的表面分形维数介于1～2之间,覆盖法计算的则介于2～3之间,后者较接近表面形貌的真实分形维数;两者计算的相关系教都大于0.99,说明镀层具有分形结构.该方法可为进一步研究镀层表面形貌及优化电镀工艺参数提供一种新的定量依据.     

Enhanced glycerol dehydration of pervaporation cross-linked PVA membranes modified by VUV/UV-C treatments

The high glycerol miscibility in water needs more efficient processes to decrease the cost of dehydration. Water stable poly(vinyl alcohol) based membranes cross-linked with 15% w/w of maleic acid were used for dehydrating glycerol-water mixtures using pervaporation (PV). The membranes were characterized using water contact angle, profilometry, Fourier transformed infrared spectroscopy-attenuated total reflectance, x-ray photoelectron spectroscopy, water stability, swelling tests, and PV. Membranes were treated using dry methods with vacuum ultraviolet (VUV; 162 nm) or ultraviolet (UV)-C (254 nm) radiation and exposed to O₂ or acrylic acid vapors, respectively. The VUV and UV-C treatments improve PV performances, increasing the water separation selectivity more than 4 and 8.5 times, respectively. UV-C treatments exhibit a water flux (kg m⁻² h⁻¹), selectivity and PSI (kg m⁻² h⁻¹) of 0.3, 250, and 87.4 respectively. Highly hydrophilic functional groups grafted onto the surface of the membranes after irradiation favor the selective transfer of water through the membrane. Overall, the VUV or UV-C membrane treatments show great PV prospect in glycerol dehydration.     

Influence of surface photocrosslinking on properties of thermoplastic starch sheets

The surface of glycerol plasticized thermoplastic starch (TPS) sheets was modified by photocrosslinking under ultra violet (UV) irradiation. Sodium benzoate was selected as photosensitizer and induced onto sheet surface layer by soaking the sample sheets in photosensitizer aqueous solution. The effects of concentration of the photosensitizer aqueous solution, soaking time and moisture content in sheets before UV irradiation on the photocrosslinking were investigated. Water contact angle, moisture absorption, and mechanical properties were measured to characterize the influence of the surface photocrosslinking modification on the properties of TPS sheets. The obtained results showed that the surface photocrosslinking treatments markedly reduced the water sensitivity of TPS sheets and enhanced their tensile strength and Young's modulus but decreased the elongation at break. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of laser polishing on surface quality and mechanical properties of PLA parts built by fused deposition modeling

Fused deposition modeling (FDM) produces parts through layer by layer on the top of each other, making it almost impossible to obtain smooth printed parts. Hence, there is a huge demand for the postprocessing of the FDM-printed parts. Laser polishing is a novel technique that can be used to polish products to obtain a smoother surface. The aim of this work was to explore the feasibility of surface-finishing FDM-printed polylactic acid (PLA) parts by laser polishing. The surface roughness, surface morphology, dynamic mechanical analysis (DMA), and tensile properties were investigated. The results indicated that the lower laser power and the bigger laser beam diameter within a certain range could facilitate the formation of smoother surface. With optimized parameters, the surface roughness was reduced by 90.4%. DMA showed that the storage modulus (E’) and glass transition temperature of PLA specimens were significantly improved due to the decrease of molecular mobility of denser structures. Moreover, the tensile strength and Young's modulus of the PLA specimen were also significantly increased after laser polishing. The fracture morphologies were observed, and the possible strengthening mechanism was also discussed. These results indicated that laser polishing could be an efficient method for surface polishing of FDM parts. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48288.     

Photochromic films prepared by solid state processing of disentangled ultrahigh molecular weight polyethylene and photochromic dyes composites

Disentangled ultrahigh molecular weight polyethylene (DPE) is a special grade of polyethylene (molecular weight, >10⁶ Da) which can be processed by an environment friendly solid state process on counter rotating two roll mill (TRM) below the melt temperature of the polymer. This unique processing property of DPE was utilized to develop smart DPE photochromic films. Photochromic dye like 'Spirooxazine' or 'Spiropyran' has been mixed with DPE resin powder prior to film formation without altering the DPE properties. These films could change their optical appearances on exposure to UV-light of wavelength 365 nm and the color change phenomenon of the films could also be replicated by sunlight. The color change observed is found to be reversible, that is, films could return to colorless form either spontaneously in dark or by thermal stimuli. Such smart property was imparted to DPE even at very low concentration (2,000 ppm) of photochromic dyes. Spectrophotometric studies were used to measure the rate of forward reaction with UV radiation and the rate of backward reaction in dark. In fact, DPE powder and photochromic dye composite was used to produce the compression molded disc to understand the color change phenomena. Moreover, it was observed that the photo-degradation rate of dye, could be retarded ~30% by using amphoteric Zinc phthalate salt. TGA and DSC studies confirmed that the characteristics of DPE film remained almost unaltered even after with preparation of film photochromic dyes.     

Regeneration of Bombyx mori silk by electrospinning. Part 2. Process optimization and empirical modeling using response surface methodology

The response surface methodology was used to model and optimize the electrospinning parameters for the spinning of regenerated nanoscale silk fibers from domestic silkworm, Bombyx mori. Electric field and silk concentrations were chosen as variables to control fiber diameter at different spinning distances. Fiber diameter was correlated to these variables by using a second order polynomial function. The predicted fiber diameters were in agreement with the experimental results. Response surfaces were constructed to identify the processing window suitable for producing nanoscale fibers.     

Modification of Polydimethylsiloxane Coatings by H2 RF Plasma,Xe2* Excimer VUV Radiation,and Low‐Energy Electron Beams

The crosslinking of thin liquid PDMS layers by three different technically relevant processes, H₂ radio‐frequency plasma treatment, Xe₂* excimer VUV irradiation, and low‐energy electron beam processing is investigated. The modifications to the layers due to the processing are monitored by means of RAIRS. Plasma processing of liquid PDMS leads to a direct conversion to a SiO_x‐like material of the topmost layers, whereas a gradual transition from PDMS to the same product is observed upon VUV irradiation. Electron exposure does not induce oxidation. The initiating steps of the conversion induced by the interaction with VUV photons, low‐energy electrons, or their combined effect with ions and H atoms in the plasma are discussed. The latter creates a high density of damage sites.

     

Enhanced piezoelectric properties of randomly oriented and aligned electrospun PVDF fibers by regulating the surface morphology

Harvesting energy has been attracting the attention of researchers in recent years. This work comprehensively reports the fabrication and characterization of poly(vinylidene fluoride) fiber webs with comparable diameters and diversified surface morphologies (wrinkled, smooth, and porous) based on randomly oriented and aligned fiber webs which are used as active layers to directly make a piezoelectric nanogenerator (PENG). The results show that wrinkled fibers are preferable fiber webs for the PENG owing to their outstanding properties represented by high fibers friction, supreme β phase content (F[β]), and interior pores. Furthermore, we found that the electrical outputs of the PENG based on aligned fiber webs are higher than those based on randomly oriented fiber webs due to the increase in the friction area. The electrical outputs of the PENG based on the aligned wrinkled fiber webs are able to run microelectronic devices when it subjected to a mechanical impact. We believe that our study may inspire the research area for future energy harvesting applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47049.     

Effect of MWCNTs irradiation grafting treatment on the surface properties of PBO fiber

The aim of this article is improved the surface properties of Poly[p‐phenylenebenzobisoxazole] (PBO) fiber with epichlorohydrin hybridized carboxylic multi walled carbon nanotubes (MWCNTs‐Ecp) grafting by using γ‐ray irradiation technology. The surface chemical properties, the surface morphology, the amount of the grafted MWCNTs on PBO fiber and the surface free energy of PBO fibers have been analyzed. The results show that MWCNTs‐Ecp have been grafted on the surface of PBO fiber by γ‐ray irradiation treatment. The surface chemical inertness and the surface smoothness of PBO fiber are significantly improved by grafting MWCNTs‐Ecp chains, the amount of the grafted MWCNTs on PBO fiber is about 11.9%, and the surface free energy of PBO fiber has an increase of 42.6% by generating some active groups such as ? COOH, ? OH, and ? C? Cl on the surface of PBO fiber. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Enhancement of the field emission properties of low-temperature-growth multi-wall carbon nanotubes by KrF excimer laser irradiation post-treatment

Multi-wall carbon nanotube (CNT) films were fabricated by microwave plasma chemical vapor deposition at low temperatures ( 500 °C). The films when properly post-treated by laser irradiation exhibited a factor of 2–3 enhancement in the emission current, while the turn-on field (E_on) was reduced from 4.89–5.22 to 2.88–3.15 V/μm. The introduction of excessive oxygen during laser irradiation, however, degrades the performance of field emission properties drastically. Raman spectroscopy measurements revealed the intimate correlation between the parameter I_D/I_G (intensity ratio between the two representative Raman peaks seen in carbon nanotubes) and the field emission performance. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses showed that the irradiation-induced modification of the tube morphology and crystallinity might be responsible for the observations.     

Influence of surface morphology on oxide growth in porous alumina

The formation of aluminium oxide layers on surfaces with different morphologies prepared by various structuring methods has been analyzed. Different growth rates and thus different oxide thicknesses have been observed under the same reaction parameters on planar surfaces in contrast to convex and concave surfaces with different radii in the curvature. The stronger the curvature of the concave or convex surface, the more the growth rates differ from the growth rates on planar surfaces. The influence of the electrical field strength on those differences is discussed in a simple model.