Design and fabrication of thin polymer coating on cotton fabric surface to impart hydrophobicity: An admicellar polymerization approach

The fluorinated poly(trifluoroethylmethacrylate) thin polymers were successfully prepared through free radical initiating admicellar polymerization approach using fluorosurfactant and 2,2,2-trifluoroethylmethacrylate (TFEM, monomer) system, which was initiated with potassium persulfate (KPS) initiator. The structure of the resultant polymer and morphology of the modified cotton fabric surfaces were confirmed by SEM and EDX analysis. The surface wettability of the modified cotton fabric was characterized by a water drop stay time and contact angle (CA) measurement. The coated cotton fabric exhibited excellent hydrophobicity with a water contact angle of 137.79°.     

The effect of phosphorus content on the thermal and the burning properties of cotton fabric coated with an ultrathin film of a phosphorus-containing polymer

The effect of phosphorus content on thermal degradation and burning behavior of poly(acryloyloxyethyl diethyl phosphate) or PADEP-coated cotton was studied. The results showed that PADEP-coated cotton prepared by admicellar polymerization using hexadecyltrimethylammonium bromide (HTAB) as a surfactant has higher amounts of phosphorus than that prepared using dodecyltrimethylammonium bromide (DTAB). Higher phosphorus content led to lower decomposition temperatures and greater amounts of char formation after thermal degradation. The effectiveness of the amount of phosphorus on the burning behavior of the treated cotton was investigated by an ASTM flammabilty test. In the case of PADEP-coated cotton prepared with DTAB, the flame spread slowly and extinguished with char formation on the fabric. For untreated cotton however, the flame spread quickly and burned the fabric entirely without char formation. Cotton coated with PADEP using HTAB exhibited self-extinguishing behavior after removing the ignition source. Decrease in decomposition temperature, increase in char formation and the burning behavior of PADEP-coated cotton are all consistent with phosphorus content on the treated fabric.     

Self-extinguishing cotton fabric with minimal phosphorus deposition

The phosphorus-containing acrylate monomer, 2-acryloyloxyethyl diethyl phosphate (ADEP), was synthesized and applied to cotton fabric by using the admicellar polymerization technique. A cationic surfactant (cetylpyridinium chloride, CPC) was used as the surfactant for admicellar polymerization. Results from FTIR-ATR and SEM showed that PADEP polymer film was successfully formed on the cotton fabric surface. TGA and DTG analyses showed that the phosphorus-containing PADEP lowered the decomposition temperature of the treated fabric resulting in a higher char yield than in the case of untreated cotton. The flammability tests showed that PADEP-coated cotton with the phosphorus content 4.18 mg/g cotton was self-extinguishing, with the flame extinguishing right after the removal of the ignition source leaving a small area of char formation.     

Empirical study and prediction of liquids retention on structured polymer surfaces

Liquids' contact angle hysteresis and critical retention volumes on five commonly used plastics with surface structures were studied. The chevron‐like groove structures, which are orthogonally arranged, make the liquid–solid contact line elongated while the droplet found staying in the Wenzel state. Various dimensions of surface structures were represented by contact length ratio σ. Advancing and receding contact angles of liquids on polymer surfaces with various conditions were reported. Reduced hysteresis H, which links between advancing and receding contact angles, was also studied and found to extend its availability on structured surfaces. The research found that surface structures have linear effects on liquids' advancing contact angles in the range of σ = 1.0 to 1.42. Linear regression analysis was hence proposed to predict advancing contact angles, and the results indicate that approximate 80% of data points have less than 6% error. An empirical model, which adopts liquid–solid surface tension as the source of liquids' retention force, was proposed to estimate liquids' critical retention volumes on inclined surfaces. The proposed model found good agreements with existing experiment data and demonstrated its superiority over previous ones. The present model provides an approach to predict liquids' storage/repellency on structured surfaces when the advancing contact angles are predictable. Copyright © 2016 John Wiley & Sons, Ltd.     

Irreversible electrowetting on thin fluoropolymer films

A study was conducted to investigate electrowetting reversibility associated with repeated voltage actuations for an aqueous droplet situated on a silicon dioxide insulator coated with an amorphous fluoropolymer film ranging in thickness from 20 to 80 nm. The experimental results indicate that irreversible trapped charge may occur at the aqueous-solid interface, giving rise to contact angle relaxation. The accumulation of trapped charge was found to be related to the applied electric field intensity and the breakdown strength of the fluoropolymer. On the basis of the data, an empirical model was developed to estimate the amount of trapped charge in the fluoropolymer as well as the voltage threshold for the onset of irreversible electrowetting.     

Mucin coating on polymeric material surfaces to suppress bacterial adhesion

Mucin, a group of large glycoproteins, constitutes one of the major components of mucous which covers the lumenal surfaces of epithelial organs and serves as a physical barrier between the extracellular milieu and the plasma membrane. The molecules have a generic structure consisting of a thread-like peptide backbone with densely packed carbohydrate side chains. Protein and carbohydrate contents are about 30 and 50%, respectively. On hydrophobic materials in aqueous environments the naked parts of mucin’s protein backbone will adhere due to their hydrophobicity, while the carbohydrate side chains are thought to orient themselves away from the surface. This gives the mucin molecules their unique properties as surfactants, i.e. they tend to adsorb to hydrophobic surfaces via protein-surface interactions while they hold water molecules via their hydrophilic oligosaccharide clusters. In the present work, bovine submaxillary gland mucin (BSM) is purified by SEC and subsequently characterized with PAGE. Four polymeric materials, PMMA, silicone, Tecoflex® polyurethane and polystyrene, are selected as coating targets. Contact angle measurements show significant changes in these materials after coating with BSM. Surface concentrations of adsorbed BSM are determined by amino acid analysis and found to correlate well with observed reductions in contact angle. Both Staphylococcus aureus and CNS S. epidermidis are used to contaminate uncoated and BSM coated surfaces of all four materials, demonstrating a correlation between suppression of bacterial adhesion and surface concentration of BSM. Thus, bacterial counts on the coated PMMA, PS, PU and silicone specimens amount to ≈3, 10, 8 and 30% of the counts found on their uncoated counterparts. These results suggest that mucin coatings could profitably be employed to reduce the risk of microbial infections on polymeric biomaterials.     

Morphology and microstructure of core-shell hybrid latexes containing fluoropolymer and acrylic copolymer

Novel core-shell hybrid latex composed by two immiscible polymers has been prepared. For the first time, we utilized fluoropolymer (FKM-40) as the core while polyacrylates as the shell in this latex, leading two immiscible components mixable under micro-molecular scale. To determine the chemical structure, in particular the miscibility between the core and the shell in this hybrid, transmission electron microscopy (TEM), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and FTIR imaging have been performed. All experiments indicate that FKM-40 mixed well with polyacrylates, particularly FTIR image demonstrated unambiguously that FKM-40 dispersed, under micro-molecular scale, in continuous polyacrylates at a concentration of 20%. Further morphology (X-ray diffraction) investigations suggest that the hybrid latex had a less crystalline domain for samples with a lower concentration of FKM-40. Interestingly, we found that the water contact angle and the water absorption of the core-shell hybrid can be readily adjustable by varying the proportion of each species during copolymerization. Finally it is worth mentioning that the core-shell methodology as demonstrated herein is superior to physical blending with regard to its capability of achieving copolymer system under micro-molecular miscibility.     

Characteristics and durability of fluoropolymer thin films

The use of plasma-polymerised fluoropolymer (CF_xO_y) thin films in the manufacture of microelectromechanical systems (MEMS) devices is well-established, being employed in the passivation step of the deep reactive ion etching (DRIE) process, for example. This paper presents an investigation of the effect of exposure to organic and aqueous liquid media on plasma-polymerised CF_xO_y thin films. Atomic force microscopy (AFM), scanning electron microscopy (SEM), ellipsometry, X-ray photoelectron spectroscopy (XPS) and dynamic wetting measurements were all employed as characterisation techniques. Highly basic aqueous solutions, including known silicon etchants, were found to cause delamination via degradation of the countersurface below the CF_xO_y thin film. Films were found to be stable in organic solvents, acidic aqueous solutions and slightly basic aqueous solutions.     

A New Green Thermoplastic Polymer with Improved Hydrophobic Character

Summary: A green thermoplastic polymer based on wheat flour was modified by the addition of a natural crosslinker genipin. Films of the polymer modified with different composition of genipin were prepared by extrusion. Free surface energy using contact angle method, moisture absorption test and hardness test were used to characterize the products. From moisture absorption and contact angle measurements, it was seen that for genipin amounts higher than 0.2% w/w, a hydrophobic character is achieved. Results obtained indicate enhancement in hydrophobic properties of the films.     

含氟聚合物(PPFGs)的制备及其构筑疏水棉布的性能研究

采用五氟苯乙烯(PFS)和甲基丙烯酸缩水甘油酯(GMA)为原料,调控PFS和GMA摩尔比例制备了一系列含氟聚合物(PPFGs),利用PPFGs支链末端环氧基团与基体棉布表面羟基发生化学反应来提高棉布的疏水性能及其耐久性能.通过对PPFGs处理棉布的接触角和形态形貌分析测试表明,含氟聚合物PPFG2化学键合处理的棉布不仅...     

New fluorinated oxazoline block copolymer lowers the adhesion of platelets on polyurethane surfaces

We have prepared an amphiphilic oxazoline block copolymer of hydrophilic poly(2-methyl-2-oxazoline) and hydrophobic poly[2-(2-perfluorooctyl)ethyl-2-oxazoline] chains. By controlling the length and composition of polymer chains, we found that this fluorinated block copolymer can be readily dissolved in water. Furthermore, we can achieve a stable surface coating of the fluorinated block copolymer by dissolving the copolymer in water, then coating the aqueous copolymer solution onto surfaces of nonwater-soluble polymers. This is a simple and useful method of modifying the surface character of polymer substrates. We have found that the polyether urethane (PEU) coated by block copolymer has a different surface chemistry and biological reactivity than the uncoated PEU. From XPS analysis, we found the fluorinated copolymer was coated on PEU (atomic % of F: 31.3 on coated PEU, 0.3 on uncoated). The two surfaces have different affinities for biological molecules. Specifically, the fibrinogen adsorption on the fluorinated copolymer-coated PEU was 62 ± 39 ng/cm², compared to a value of 156 ± 99 ng/cm² for uncoated PEU. In an ex vivo evaluation of platelet adhesion, the surface of coated PEU attached a few white cells while uncoated PEU was covered with activated platelets. © 1994 John Wiley & Sons, Inc.     

Synthesis and characterization of novel polyimides containing stilbene unit in the side chain and their controllability of nematic liquid crystal alignment on the rubbed surfaces

Four polyimides containing hexylene spacer and a fluorostilbene unit in the side chains were prepared in thin‐film form by two‐step condensation of 3,3′‐bis[(4′‐fluoro‐4‐stilbenyl)oxyhexyloxy]‐4,4′‐biphenyldiamine (FS6B) with pyromellitic dianhydride (PMDA), benzophenone‐3,3′,4,4′‐tetracarboxylic dianydride (BTDA), 4,4′‐oxydi(phthalic anhydride) (ODPA), and 4,4′‐hexafluoroisopropylidenedi(phthalic anhydride) (6FDA), respectively, and their controllability of liquid crystal (LC) alignment on rubbed surfaces was investigated. Pretilt angles of LCs were achieved in the 2–9° range, depending on the rubbing density and backbone structures. The effect of the mesogenic stilbene group on the pretilting of LCs was distinctive in FS6B‐PMDA. Contact‐angle measurements on thin films annealed at 120 °C revealed that FS6B‐PMDA potentially had the better alignment stability than FS6B‐6FDA. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3622–3632, 2001     

Surface behavior and film formation analysis of sisal fiber coated by poly(methyl methacrylate) ultrathin film

Admicellar polymerization was used to modify a sisal fiber surface with poly(methyl methacrylate) (PMMA) in order to improve the compatibility between the sisal fiber and the surrounding polymeric matrix in a composite. The effect of the amount of monomer (methyl methacrylate) and initiator (sodium persulfate) on the hydrophobicity behavior and PMMA film formation of the admicellar-treated sisal surface was studied. The increase in the hydrophobicity of the admicellar-treated sisal fiber was examined by flotation testing, moisture absorption, and electrostatic charge or zeta (ζ) potential. The amount of PMMA film formed on the sisal surface was investigated by the weight loss of the admicellar-treated sisal extracted by acetone and chloroform; and the thermal degradation was studied by thermogravimetric analyses. The admicellar-treated sisal could float on the surface of water for longer than half an hour, and its moisture absorption decreased. The ζ potential of its surface also showed a significant change compared to the untreated sisal. The results from the weight loss indicated that the amount of PMMA formed on the sisal fiber surface depended on the amount of monomer and initiator. The Fourier transform infrared spectrum of the admicellar-treated sisal showed the characteristic peaks of PMMA and the scanning electron micrograph of the treated sisal was clearly different from the untreated sisal, confirming that there was a thin film coating on the admicellar-treated sisal fiber.     

含氟接枝共聚物为助稳定剂的苯乙烯细乳液聚合反应

以含氟接枝共聚物(PSG)单独作为助稳定剂,十二烷基硫酸钠(SDS)为乳化剂,过硫酸钾(KPS)为引发剂引发苯乙烯(St)的细乳液聚合。考察了聚合温度、乳化剂用量、引发剂用量和PSG用量对细乳液聚合转化率的影响。结果表明,以PSG单独作为助稳定剂,细乳液聚合过程较稳定,起始单体液滴数目与成核粒子数目几乎相等。最终转化率随着乳化剂用量和反应温度的提高而增加,引发剂用量影响不明显。在相同的反应条件下,分别以相同用量(w.t.%=0.091%时,占单体和水的总质量)的PSG和十六醇为助稳定剂用于苯乙烯细乳液聚合,反应290min后,PSG体系的聚合转化率达到87.2%,而十六醇体系的聚合转化率只有78.2%。     

Adsorption of polyamides and polyamide–silane mixtures at glass surfaces

The individual and combined adsorption behavior of polyamides and two different silanes to multicomponent glass surfaces was probed with a combination of x‐ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and static contact angle measurements. Samples were analyzed with and without solvent rinsing to separate the weakly bound (physisorbed) and more strongly bound (chemisorbed) species. High‐resolution XPS on N 1s revealed that the polyamides adsorb to the glass surfaces via protonated amine species at the acidic (OH) sites on the glass surface. Angle‐resolved XPS confirmed this by showing that the alkyl portion of the polymer is oriented away from the glass interface. In competitive coadsorption studies it was found that amino‐terminated silanes preferentially adsorb to the glass surface, relegating the polyamide to a physisorbed outer layer. When mercaptoterminated silanes were competitively coadsorbed the polyamide was preferentially adsorbed even when present at a concentration twenty times less than that of the silane. Altogether, this work reveals the strong interaction between surface silanols and amino‐functionalized organics. Copyright © 2003 John Wiley & Sons, Ltd.     

Studies of the wetting kinetics of liquid drops on solid surfaces

The viscosity _L and the surface tension _L of the liquid as well as the equilibrium contact angle _e are essential parameters governing the wetting kinetics of liquids on solids. By means of a contact angle apparatus with video image digitization, the dynamic contact angle and the radiusr of the contact area of sessile drops on solid surfaces have simultaneously been determined in dependence on time after drop application between about 3·10^–2 s and long times.The measurements were performed with series of liquids: polydimethylsiloxanes with different molecular masses and solutions of polyisobutylene in decalin and polyacrylic acid in water, covering a wide range of concentrations. The liquids in each series have a constant surface tension, but viscosities ranging over about four orders of magnitude, allowing the influence of _L and _L to be studied independently. Solids such as glass, polyethylene and polytetrafluoroethylene were chosen so that the cases of complete wetting (spreading) and partial wetting ( _e) could be studied.The curves of cos andr/R ₀ vs. time for the different liquids of a series can be superimposed to a master curve by plotting them against _L·t _L·R ₀, whereR ₀ is the radius of the original drop. All these master curves coincide at small wetting times, with exception of the data for the polysiloxanes. That means that the early stage of the wetting process is determined only by the properties of the wetting liquid. The influence of the solid surface, characterized by the equilibrium contact angle _e becomes significant only at the end of the wetting process.Dedicated to Professor Dr. H. Willersinn on the occasion of his 65^th birthday     

Bioinspired construction on aluminum alloy surfaces with stable super‐hydrophobicity and their resulting wettability

The bioinspired leaf‐like super‐hydrophobic surfaces on aluminum alloy were fabricated by means of a facile method using anodic oxidation. The surface morphologies, compositions, and wettability were investigated with SEM, XPS, and contact angle measurement, respectively. The SEM showed hierarchical microstructures and nanostructures, the static contact angle was about 167.7 ± 1.2°, and sliding angle was 5°. The super‐hydrophobic phenomenon of the prepared surface was analyzed with Cassie theory, and it is found that only about 3% of the water surface is contacted with the metal substrate and the remaining 97% is contacted with the air cushion. Copyright © 2011 John Wiley & Sons, Ltd.     

(甲基)丙烯酸氟烷基酯的“活性”/可控聚合

带氟烷基侧链的(甲基)丙烯酸氟烷基酯聚合物是一类具有独特表面性能和光学特性的氟聚合物,传统的自由基共聚合由于无法调节聚合物的微细结构和氟原子的分布,限制了该类聚合物在更广领域的应用.活性聚合为聚合物分子设计和合成提供了一个有效方法,利用活性聚合方法可以获得预期结构和性能的含氟嵌段聚合物材料.由于引入了氟烷基侧链,(甲基)丙烯酸氟烷基酯的活性聚合又有其特殊性,本文针对它的活性阴离子聚合、基因转移聚合、活性自由基聚合等方面作一综述.