Low surface energy films based on partially fluorinated isocyanates: the effects of curing temperature

Self-stratification strategy can be used to prepare films in which both bulk and surface properties can be optimized. By using this approach, only a very small quantity of fluorinated species is needed to generate a surface with low surface energy. When cross-linking is involved during film formation, we are dealing with a competition behavior between the diffusion of fluorinated species and the formation of cross-linked network. In this study low surface energy polymeric films were prepared on the basis of partially fluorinated polyisocyanates, in combination with hydroxyl-end-capped three-armed solventless liquid oligoesters and modified hyperbranched polyesters. At a fluorine concentration of only 0.5 wt.%, contact angles of water and hexadecane can reach 120° and 80°, respectively. A surface energy as low as 10–15 mN/m can be obtained upon the addition of less than 1 wt.% of fluorine in the films. It was shown, from real time ATR-FTIR and contact angle measurements, that the curing temperatures demonstrated significant effects on the cross-linking rate as well as on the wettability of the films.     

Low surface energy coatings covalently bonded on diamond-like carbon films

In the present work, a chemical treatment with perfluorinated peroxides is proposed to obtain protective layers covalently linked to a diamond-like carbon (DLC) surface. The lubricant properties of perfluorinated compounds and the stability of the chemical modification of DLC surface simultaneously cooperate in this technical approach. Each fluorinated layer is deposed on an bare DLC surface by a dip coating application technique and the covalent linkage of the fluorinated layers is obtained by the thermal decomposition of the peroxidic moieties of the perfluorinated peroxides. Reactive perfluorinated radicals are generated close to the sp² sites of the DLC surface, allowing the formation of covalent bonds. The fluorinated peroxides used in this work belong to the class of the PFPE peroxides and to the class of the perfluorodiacyl (PFDA) peroxides. The effect of the fluorinated coatings on the DLC surface is studied using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), with contact angle (CA) measurements and, in particular, the friction forces are evaluated by means of lateral force microscopy (LFM).     

A novel fluorinated polymeric product for photoreversibly switchable hydrophobic surface

A new chemical product, that is, photoreversibly switchable hydrophobic surface coating, was synthesized by atom transfer radical polymerization and graft‐from method based on molecular design. Focusing on the strategy of new product development from the chemical product engineering perspective, the product characterization, switching mechanism analysis, performance evaluation, and model interpretation were carried out to confirm the new product manufacture and to ensure the product application with a following aging test. The results show that the product enables surfaces to have reversibly switchable wettability and excellent stability after a month‐long test with eight irradiation cycles. Additionally, the wetting behavior of silicon surface can be tuned between hydrophilicity and hydrophobicity based on blank sample using the surface engineering technique (decorated with functional film and surface roughening). The product presented here can be utilized for constructing a hydrophobic surface with photo‐induced controllable wettability in moisture‐resistance, and it also offers a new technique for the manipulation of liquids in microfluidic devices. © 2014 American Institute of Chemical Engineers AIChE J 60: 4211–4221, 2014     

含氟丙烯酸酯共聚物涂膜表面润湿性的研究

以甲基丙烯酸甲酯(MMA)、丙烯酸丁酯(BA)、甲基丙烯酸β–羟乙酯(HEMA)、(甲基)丙烯酸高级酯(AAs)、含氟(甲基)丙烯酸酯(Fs)等单体为原料,HDI三聚体为固化剂,通过改变共聚物组成、氟碳链长、(甲基)丙烯酸高级酯烷烃链长等因素,合成了一系列的含氟丙烯酸酯共聚物。采用水、煤油和液压油接触角以及水滴滚动距离,表征了共聚物涂膜的表面润湿性,并探讨了其影响因素。结果表明,共聚物组成和结构、烷烃链长对水的接触角影响不大,而对水的滚动性能具有较大影响;氟碳链长以及氟单体的添加方式对油水接触角和水的滚动性能有较大影响;烷烃侧链的柔顺性对油的接触角影响较大,而对水几乎没有影响。     

含氟硅聚苯并噁嗪材料的制备及其表面性能

本文合成了含氟硅氧烷苯并噁嗪单体,在采用光学显微镜等考察水解沉积条件对单体在羟基化基片表面化学成膜的影响的基础上,考察了温度、时间等对聚苯并噁嗪成膜后表面能的影响,并对聚苯并噁嗪材料在不同热处理温度（100℃-350℃）下表面能的热稳定性能进行了研究。结果表明用pH=2的盐酸溶液调节沉积液所得单体膜最均一完整,聚合物的表面能随着固化时间的增加先降低后升高,固化温度越高,达到完全固化所需要的固化时间越短,在160℃,190℃,220℃,240℃下固化所得聚合物最低表面能分别是15.6 mJ?m-2 (4 h),15.0 mJ?m-2 (1 h),15.3 mJ?m-2 (15 min),15.5 mJ?m-2 (5 min),均低于Teflon的表面能（22.0 mJ?m-2）。聚合物膜表面能在低于200℃的温度下处理其表面能可基本保持不变,可以作为抗粘材料应用于纳米压印技术中。     

Formation of deformed honeycomb-patterned films from fluorinated polyimide

Fabrication of honeycomb-patterned films from one of the soluble fluoro-polyimides in a humid atmosphere was reported in this paper. This polyimide was synthesized from 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 4,4′-methylene dianiline (MDA) by two-step method. The obtained polyimide kept excellent rigidity and thermal stability, and especially, exhibited good solubility both in strong bipolar solvents and in common organic solvents. By blowing airflow across the surface of the deposited solution horizontally, the pores locating at the windward side of the film could change their morphologies from circle to ellipse, while the pores at the leeward side were almost kept their shapes. A detailed research about the pore deformation on various regions in a same film was carried out. At last, the differences in pattern formation between dynamic and static environment were tested, and the results showed that pores fabricated under flowing atmosphere were smaller and more regular than those formed under static condition.     

Adhesion performance and surface characteristics of low surface energy psas fluorinated by UV polymerization

Acrylic pressure sensitive adhesives (PSAs) have a range of applications in industry, such as medical products, aircraft, space shuttles, electrical devices, optical products, and automobiles, etc. In this study, acrylic PSAs with fluorinated groups were synthesized using 2,2,2‐trifluoroethyl methacrylate (TFMA) under UV radiation. The surface properties and adhesion strength were measured. The results showed that the addition of TFMA reduced the surface energy of the PSAs and improved the adhesion strength. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers     

Magnetic properties of double-side partially fluorinated graphene from first principles calculations

Density functional theory calculations were used to study the structural, electronic, and magnetic properties of double-side partially fluorinated graphene. Both even and uneven fluorinated structures examined. It is found that midgap states and magnetic moments only appear in the uneven double-side fluorinated graphene. The magnetic moments mainly come from the carbon atoms at the edge of the fluorinated region in unevenly double-side fluorinated graphene. The dependence of magnetic moments on external tensile strain was also examined, which shows that the induced magnetic moments can be significantly increased by increasing the tensile strain.     

Preparation of microporous carbon films from fluorinated aromatic polyimides

Pyrolysis and carbonization behaviors of fluorinated aromatic polyimide films synthesized from fluorinated dianhydrides and diamines were investigated by thermogravimetric and mass spectrometric measurements. Evolution of fluorine compound gases and related species was observed during the pyrolysis in the temperature range from 450 to 700 °C, in addition to the evolution of CO and CO₂ due to the imide ring degradation. By the carbonization of these fluorinated polyimides at 600-1000 °C, highly microporous carbons were obtained without any activation process, of which adsorption/desorption isotherm of N₂ gas was typical type I and pore size distribution was sharp at around 0.55 nm in width. Surface area increased with increasing fluorine content in the repeating unit of fluorinated polyimide: the polyimide with the highest fluorine content of 31.3 mass% gave a high microporous surface area of 1342 m² g⁻¹ and micropore volume of 0.44 mL g⁻¹.     

Effect of crosslinking on the surface free energy and surface reorganization of waterborne fluorinated polyurethane

To endow waterborne fluorinated polyurethanes (WFPUs), films with stable lower surface free energy and lower surface reorganization after the films contacted with water, a series of crosslinked WFPUs (CWFPUs) emulsions were prepared by adjusting the content of aziridine (AZ). The effect of crosslinking on the surface free energy, glass-transition temperature (T _g), water absorption, and surface composition of dry/hydrated WFPUs and CWFPUs films were studied by CAs test, dynamic mechanical analysis, water absorption measurements, and X-ray photoelectron spectroscopy. When the fluorine content was 0.5%, the surface free energy of the CWFPUs films modified by 0.4% AZ content (CWFPU-6-0.5-CK0.4) reached to the lowest value of 15.76 mN m⁻¹ which almost equaled to the surface free energy (15.45 mN m⁻¹) of the dry uncrosslinked films (WFPU-6-0.5). With the increasing of AZ content, the T _{g, hard} of hard segments of the CWFPUs films increased and the water absorption of the CWFPUs films decreased, which suggested the formation of the crosslinked network structures. The studies of the surface elements and groups composition of dry/hydrated WFPUs and CWFPUs both confirmed that the surface reorganization and the migration of fluorinated side chains were restricted by the crosslinked network structures. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47167.     

Transmission of mechanical energy through polymeric liquid crystals and their blends

Molecular composites, also called polymeric liquid crystals (PLC), are contrasted with the traditional composites; the name heterogeneous composites is proposed for the latter. Advantages of blending PLCs with ordinary engineering polymers are discussed. Results reported for blends of poly(ethylene terepthalate) (PET) with a PLC containing sequences of PET and p-hydroxybenzoic acid (PHB) include thermophysical properties, melt rheology, mechanical properties of solid blends, and scanning electron microscopy of fracture surfaces. A model called the island model was developed to explain the results: One assumes that the lines of force as well as propagating cracks tend to concentrate in the phase rich in the more flexible engineering polymer, avoiding the islands rich in the liquid-crystalline phase. This prevails until the phase inversion occurs. Predictions from the model are fully confirmed by the experimental evidence.     

Using field theory to measure surface resistivity of high-resistance polymeric films

Theoretical expressions based on Ohm's law for field theory were derived to measure surface resistivity of high-resistance polymer films using parallel plate and concentric circular electrodes. Experimental measurements of resistivity were compared to experimental measurements using conventional expressions based on Ohm's law for circuit theory. Expressions based on Ohm's law for circuit theory were found to be inadequate for measuring surface resistivity. The surface resistivity of high-resistance films can be accurately measured if electric field theory is used to include the effects of electrode structure, if relative humidity (RH) and temperature are controlled, if the level of applied voltage is limited, and if the measuring system is shielded from extraneous electric and magnetic fields. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2856–2862, 2001     

Novel partially bio-based fluorinated polyimides from dimer fatty diamine for UV-cured coating

A series of novel partially bio-based fluorinated polyimides with double-bond end groups (BGPIs) from 4,4′-(hexafluoroisopropylidene) diphthalic anhydride, 4,4′-(hexafluoroisopropylidene) dianiline, Priamine 1074, 4-aminobenzoic acid, and glycidyl methacrylate were synthesized via a copolycondensation method in m-cresol. The chemical structure and performances of BGPIs were fully characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, gel permeation chromatography, solubility test, X-ray diffraction, and differential scanning calorimetry. It was determined that the prepared BGPIs were in the amorphous phase and readily soluble in conventional aprotic polar solvents. Additionally, the properties of as-prepared UV-cured coatings based on BGPIs were also evaluated by real-time Fourier transform infrared, thermogravimetric analysis, UV–Vis spectroscopy, and so on. Results revealed that all coatings exhibited satisfactory curing, higher adhesion, lower water uptakes, outstanding optical transparency, and fairly favorable thermal stability under a high content of biomass up to 48.9%. Therefore, these bio-based polymers could be considered as a potential sustainable candidate for high-temperature UV-curable coatings in the microelectronic field.     

Synthesis of sulfonyl fluorinated macro emulsifier for low surface energy emulsion polymerization application

Fluorinated acrylate emulsions have been extensively applied for hydrophobic surface coatings. To obtain fluorinated emulsions of low surface energy, amphiphilic sulfonyl macro emulsifiers consisting of 2‐(perfluorohexyl) ethyl acrylate (PFHEA) and 2‐acrylanmido‐2‐methylpropanesulfonic acid (AMPS) were designed via radical polymerization and subsequently used for the emulsion copolymerization of PFHEA, methyl methacrylate (MMA), and methyl butyl acrylate (MBA). Under optimum synthesis conditions, the emulsifier displayed superior emulsification properties such as high monomer conversion, small particle size, and excellent stability compared with conventional emulsifiers. The corresponding emulsions with sulfonyl macro emulsifiers exhibited extreme low surface energy (9.8 mN/m) and outstanding hydrophobicity due to high contents of fluorinated chains, as well as thimbleful hydrophilic sulfonyl groups, which shows the great potential in water repellent modification application. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44921.     

Foam formation from fluorinated polyphosphazenes by liquid CO2 processing

Three dimensional foams of fluorinated polyphosphazenes were prepared using liquid CO₂ to solvate polymer films, which were then expanded by volatilization of liquid CO₂ within the polymer matrix. The polymers dissolved in CO₂ at 1.5 × 10⁷ Pa (2200 psi) and room temperature. Materials were examined using Raman spectroscopy before and during high pressure CO₂ exposure. The solubility in liquid CO₂ is attributed to interactions between the solvent and the fluorine atoms in the polymer side groups. Fluoroalkoxy polyphosphazenes are known for their hydrophobicity and fire retardant properties, and these characteristics are retained in the foams. Scanning electron microscopy, water swelling, and preliminary fire retardance tests were conducted to determine the morphology and properties of the foams. These materials are possible candidates for a number of different engineering applications. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

梯度表面能材料上液滴运动机理

通过显微测量技术获得了梯度表面能材料表面的微观结构,分析了经扩散控制的硅烷化处理的硅基材料表面上表面能梯度形成的机制和影响因素。通过可视化实验,并从能量转换关系和液滴受力分析上探讨了液滴在梯度表面能材料上的快速运动机理,研究了液滴运动过程,及薄膜润滑对液滴运动速度的影响。     

Surface energy inducing asymmetric phase distribution in films of a bynary polymeric blend

The phase morphology of blends of low density polyethylene (PE) with low molecular weight copolyamide (CPA) was investigated in films having 50-100 μm thickness. Films were prepared by compression moulding between two surfaces with different polarity, namely teflon and aluminium sheets, in a parallel plate heating press. The film surface characterization and surface energy deduction were performed by FT-IR/ATR spectroscopy and contact angle measurements, respectively. Moreover, the morphology and phase distribution were investigated by scanning electron microscopy both on the surfaces and on the cryogenic section of the films.The copolyamide resulted to be the dispersed phase in all compositions (90/10, 95/5, 97.5/2.5 and 99/1 PE/CPA) and the shape, dimension and distribution of the domains depending on temperature, pressure, time and nature of the surfaces used during the compression stage.The experimental evidences were discussed with respect to the different surface energies of the type of moulding material during the film preparation and related compatibility of the components.     

含氟丙烯酸酯共聚物的合成及其涂膜表面疏水、疏油性能研究

以单体甲基丙烯酸甲酯、丙烯酸丁酯、丙烯酸、含氟(甲基)丙烯酸酯为原料,通过改变氟碳链长度、氟单体含量以及添加方式等因素,合成了一系列的含氟丙烯酸酯共聚物。利用表面接触角测试仪、红外光谱仪和多功能光电子能谱仪表征了共聚物涂膜的表面疏水、疏油性能以及表面化学成分,探讨了其影响因素。结果表明,共聚物涂膜表面疏水、疏油性能与其表面化学成分密切相关;使用长氟碳链的氟单体、增加氟单体用量以及采用在反应后期一次性加入氟单体的方法均有利于提高涂膜表面的疏水、疏油性能;当全氟辛基乙基甲基丙烯酸酯的质量分数为25%时,所得涂膜表面的氟元素质量分数达到44.284%,对水、对正十六烷的接触角分别达到127°和65°。     

Low surface temperature synthesis and characterization of diamond thin films

Polycrystalline diamond films are deposited on p-type Si(100) and n-type SiC(6H) substrates at low surface deposition temperatures of 370–530 °C using a microwave plasma enhanced chemical vapor deposition (MPECVD) system. The surface temperature during deposition is monitored by an IR pyrometer capable of measuring temperature between 250 and 600 °C in a microwave environment. The lower deposition temperature is achieved by using an especially designed cooling stage. The influence of the deposition conditions on the growth rate and structure of the diamond film is investigated. A very high growth rate up to 1.3 μm/h on SiC substrate at 530 °C surface temperature is attributed to an optimized Ar-rich Ar/H₂/CH₄ gas composition, deposition pressure, and microwave power. The structure and microstructure of the films are characterized by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. A detailed stress analysis of the deposited diamond films of grain sizes between 2 and 7 μm showed a net tensile residual stress and predominantly sp³-bonded carbon in the deposited films.     

Honeycomb-like polymeric films from dendritic polymers presenting reactive pendent moieties

In this paper we describe the fabrication of honeycomb-shaped polyurethane films from dendritic side-chain polymers presenting reactive pendent units. Two novel functional polyurethanes, poly(urethane-co-acylurea) (PU-PACY) and polyurethane-co-azetidine-2,4-dione containing polyurethane (PU-PAZ), were synthesized. The waxy dendrons featured focal urea/malonamide linkages favorable for hydrogen bonding and peripheral alkyl chains. These intermolecular forces caused two functional PUs to undergo phase separation and self-assembly. This resulted in honeycomb-like films with well-controlled surface roughness characterized in terms of the ratio of rim width (W) to the pore size (D), i.e. W/D. The PU-PAZ film had a higher contact angle (CA) and a lower value of W/D than did the PU-PACY analogue, due to the presence of relatively more hydrophobic azetidine-2, 4-dione functionalities in the former film. Subsequent chemical modification of the PU-PAZ films through reaction with a hydrophobic poly(oxyalkylene)amine enhanced the CA from 113 to 134°. Further physical modification through a peeling-off process rendered the film surface with a three-dimensional (3D) rod-co-valley-structure having feature dimensions on a submicrometer scale. The 3D rod-co-valley–like film exhibited superhydrophobicity with a CA of 151°. The films also displayed excellent solvent-resistance after crosslinking with a diamine. Through hydrophobic or hydrophilic chemical modification, we could readily manipulate the surface properties of these honeycomb-like films with controllable surface roughnesses and reactive functionalities.