采用XPS与接触角法研究氟聚合物表面结构与性能

本文采用接触角和变角XPS方法对FA共聚物的表面能、 表面微相结构做了进一步的研究.     

Preparation and surface properties of latexes with fluorine enriched in the shell by silicon monomer crosslinking

A series of core-shell acrylic copolymer latexes containing fluorine enriched in the shell have been prepared by emulsion polymerization of a variety of hydrocarbon monomers with (perfluoroalkyl)methyl methacrylate and vinyltriethoxysilicone. In the presence of a reactive anionic and a long chain anionic-nonionic emulsifier, the core-shell latexes were prepared and characterized by transmission electron microscopy (TEM) and tapping-mode atomic force microscopy (AFM). From AFM and contact angle measurements, it was observed that the resulting fluorine and silicon-containing acrylic copolymers with surface energy as low as 15.5 mN/m formed a dense and gradient film containing a surface layer with high a fluorine content, and that the fluorinated particles can be fixed on the surface due to the crosslinking reaction of multi-functional silicon monomer even though the fluorinated carbon number was not enough to crystallize.     

Effect of sequence structure on wetting behaviors of fluorinated methacrylate polymers based on perfluorohexylethyl methacrylate and stearyl acrylate

Due to the non-crystalline properties of short chain perfluoroalkyl groups,using short chain perfluoroalkyl to stabilize low surface free energy polymers has been a challenging task.In this study,we prepare a series of random copolymers poly(perfluorohexylethyl methacrylate)-co-poly(stearyl acrylate) (P13FMA-co-PSA) and block copolymers poly(perfluorohexylethyl methacrylate)-b-poly(stearyl acrylate) (P13FMA-b-PSA),and systematically investigate the effects of the sequence structure and the content of 13FMA of the fluorinated copolymers on surface free energy and surface reorganization.Static/dynamic contact angle goniometry and water/oil repellency analyses demonstrate that the random polymer P13FMA-co-PSA could not achieve low surface free energy and low surface reorganization at the same time.In contrast,for the block copolymer P13FMA-b-PSA,both low surface free energy and low surface reorganization are acquired simultaneously.The results of X-ray photoelectron spectroscopy (XPS),dynamic contact angle goniometry and differential scanning calorimetry (DSC) reveal the above-mentioned properties.The consecutive 13FMA segments improve the surface fluorine density,while the consecutive SA chains enhance the crystallinity of the SA segments,and further hinder the surface reorganization of the perfluoroalkyl groups.Therefore,P13FMA-b-PSA exhibits a higher utilization efficiency of fluorine atoms and a better structural stability than P13FMA-co-PSA.     

Surface characterization of flat and rough films of perfluoromethacrylate-methylmethacrylate statistical copolymers synthesized in CO2-expanded monomers

Statistical copolymers of perfluoroalkyl ethyl methacrylate (Zonyl-TM) and methylmethacrylate were synthesized in CO₂-expanded monomer mixture at a low pressure of 10–13 MPa for the first time. M _w of the copolymers was found to decrease with the increase of Zonyl-TM content. Flat films of these copolymers were obtained by dip coating from their chloroform solutions and were characterized using contact angle measurements, optical microscopy, and 3D profilometry. The increase in the Zonyl-TM content of the copolymers resulted in a decrease of the total surface free energy. Superhydrophobic and oleophobic rough copolymer films were also prepared by applying a phase-separation process where THF was used as the solvent and ethanol as the non-solvent. Surface roughness increased with the increase in the nonsolvent ratio resulting in an increase in the water contact angle from 103° to 151° and hexadecane contact angle from 49° to 73°.     

原子转移自由基聚合合成甲基丙烯酸丁酯与丙烯酸全氟烷基乙酯两嵌段共聚物及其性能的研究

通过原子转移聚合合成了大分子引发剂PBMA Br及系列含氟两嵌段共聚物P(BMA b FAEM) ,并利用1 H NMR、F EA、GPC、FTIR对其结构进行了表征 .所合成的含氟嵌段共聚物膜具有低临界表面张力 .本文通过接触角的测定研究了含氟两嵌段共聚物的憎水、憎油性能与共聚物的含氟量 ,热处理温度 ,热处理时间的关系 ,结果表明含氟嵌段PFAEM具有向空气 聚合物界面富集的倾向 ,在共聚物中引入含氟嵌段可以明显提高共聚物的憎水、憎油性 .当含氟嵌段达 7 6wt%时 ,临界表面张力 (γc =18 7mN m)已与聚四氟乙烯相当 (γc=18 5mN m) ,显示出明显的低表面能特征     

Self‐emulsification and surface modification effect of fluorinated amphiphilic acrylate graft copolymers

We report on self‐emulsification and surface modification effect of novel fluorinated amphiphilic graft copolymers prepared with perfluoroalkyl acrylate and 2‐dimethylaminoethyl methacrylate using simple macromonomer technique and radical copolymerization. The interfacial properties of amphiphilic graft copolymers were characterized with light scattering, contact angle measurement, and X‐ray photoelectron spectroscopy. The preparation of fluorinated amphiphilic graft copolymer was verified using nuclear magnetic resonance and Fourier transform infrared spectroscopy. It was observed that the fluorinated amphiphilic graft copolymer has both strong hydrophobic and hydrophilic properties and shows self‐emulsification ability without addition of external surfactants. The graft copolymer shows very low surface energy even though the copolymer has low content of hydrophobic segment and better performance than random copolymer for low‐energy surface modification. The addition of small amount of the graft copolymer (0.1 wt %) into the base poly(methyl methacrylate) was sufficient to lower the surface energy less than that of poly(tetrafluoroethylene). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis and characterization of a new fluorinated macroinitiator and its diblock copolymer by AGET ATRP

A new fluorinated macroinitiator of poly 2,2,3,4,4,4-hexafluorobutyl methacrylate-Br (PHFMA-Br) was prepared via activator generated by electron transfer atom transfer radical polymerization (AGET ATRP), and then a series of fluorinated block copolymers with different fluorine content were successfully synthesized from the macroinitiator by the second step AGET ATRP. GPC, FTIR and ¹H NMR data obtained verified the synthesis. Contact angle measurement indicated that proper fluorine content could decrease the surface energy and increase the contact angle of the copolymer films. XPS characterization showed that the large difference in surface energy between the block and random copolymer film resulted from the difference of the fluorine content on the surface, although the fluorine content of the two copolymers in bulk was similar. The self-assembly behavior of the fluorinated block copolymer in selective solvents was evaluated by the TEM study, and the stable micelles with a core-shell structure were observed when the copolymer content was about 1 wt%.     

Control through monomer placement of surface properties and morphology of fluoromethacrylate copolymers

The arrangement of monomers and morphology of fluorinated copolymers of methyl methacrylate (MMA) were found to be important for controlling the surface energy of the materials when formed into thin films. Novel copolymers of MMA and 2,2,3,3,4,4,4‐heptafluorobutyl methacrylate (F3MA) were prepared with different monomer placement, namely statistical and block arrangements of the monomer units. The surface energies decreased with increasing incorporation of F3MA, in a manner consistent with previous reports for similar copolymers; however, the surface energies of the block copolymers were consistently lower than the statistical copolymers. This was interpreted as arising from conformational restriction of presentation of the fluoromonomers to the surface in the statistical copolymers, and formation of phase‐separated domains at the surface of the block copolymers. The morphology of the block copolymers was confirmed by small angle X‐ray scattering measurements, which allowed calculation of a solubility parameter for the fluorinated segments. The results have implications for the design of more environmentally acceptable materials with ultra‐low surface energies. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2633–2641     

Effect of block length on the self-assembly of end-capping perfluoroalkyl moieties on the polymer surface

Most research on copolymers with fluorinated monomers has focused on the relationship between fluorinated monomer content and the corresponding surface structure. However, the influence of the non-fluorinated block on the surface structure of the copolymer film is unknown. Various molecular weight poly(butyl methacrylates) (PBMA) end-capped with 2-perfluorooctylethyl methacrylate (FMA) units (PBMA-ec-FMA) have been synthesized by atom transfer radical polymerization (ATRP). The effect of the PBMA block length on the surface structure and properties of the polymers both in the solid state and in solution was investigated using various techniques. X-ray photoelectron spectroscopy (XPS), sum frequency generation (SFG) vibrational spectroscopy and X-ray diffraction (XRD) analyses indicated that longer PBMA blocks enhanced both the enrichment of the fluorinated moieties and the order of the packing orientation of the perfluoroalkyl side chains on the surface. This enhancement was attributed mainly to the molecular aggregate structure of the end-capped polymers with long PBMA blocks in the solution and to the interfacial structure at the air/liquid interface, which favors the -(CF₂)₇CF₃ moieties self-assembling on the polymer surface during film formation. This observation suggests that the polyacrylate block structure in fluorinated diblock copolymers, in addition to the fluorinated monomer content, plays an important role in structure formation on the solid surface.     

紫外光引发LDPE膜接枝含氟丙烯酸酯的研究

通过紫外光引发表面接枝聚合反应的方法 ,把含氟丙烯酸酯单体R 5 6 1 0引到LDPE薄膜上 .对经丁酮抽提后的接枝膜进行FTIR、ESCA、SEM和DSC等表征 ,证实含氟聚合物以化学键的方式接枝在LDPE基体膜上 .在一定范围内 ,增加紫外光强、引发剂和单体浓度以及反应温度等均有利于提高接枝率 .经计算R 5 6 1 0的紫外光引发接枝聚合反应总活化能为 5 4 2kJ mol.接枝膜的接触角随着接枝率的提高逐步增大 ,直至趋于恒定 .作者提出接枝膜存在一个在接触角测定时影响基体膜与探测水滴相互作用过程的边界层 .当接枝率较低、接枝层厚度小于边界层临界厚度时 ,基体LDPE影响接触角的大小 ,但随着接枝率提高 ,接枝层逐渐变厚 ,氟聚合物层对接触角的贡献逐渐占优势 ,导致接触角随之增大 .当接枝率超过一定值以后 ,接枝层厚度超过边界层临界厚度 ,接枝层对接枝膜的接触角起全部贡献 ,接触角测定值随之稳定     

Comparison of surface properties of random, block, and graft copolymers having perfluoroalkyl and silicone-containing side chains

Fluorosilicone copolymers of random, block, and graft with both perfluoroalkyl and silicone-containing side chains were synthesized, and their surface properties and surface modification effects on PVC film were compared. It can be confirmed that the fluorosilicone copolymers of random, block, and graft exhibit very low surface free energies of 9-13 dyn/cm, depending on the perfluoroalkyl group content and their molecular structure. The inherent surface free energies of the fluorosilicone copolymers are significantly influenced by their molecular structure and perfluoroalkyl group content. It can also be found that the fluorosilicone copolymers are very effective for lowering surface free energy. The surface free energy of a copolymer/PVC blend strongly varies with perfluoroalkyl group content as well as molecular structure. The molecular structure of a fluorosilicone copolymer is as important as the perfluoroalkyl group content for their inherent surface free energies and surface modification of other polymers.     

含氟高分子/SiO_2杂化疏水材料的制备及涂层表面性质

采用自由基溶液聚合与溶胶-凝胶法相结合的方法制备了含氟高分子/SiO2杂化疏水材料.通过甲基丙烯酸十二氟庚酯(FA)与乙烯基三乙氧基硅烷(VTES)共聚合成了含氟硅共聚物(PFAS),进一步通过原硅酸乙酯(TEOS)与PFAS共聚物溶液共水解缩聚制备了具有含氟侧基的碳碳主链高分子和硅氧网络的含氟高分子/SiO2杂化疏水材料.研究结果表明,SiO2组分含量提高可以显著增加杂化材料薄膜的涂敷厚度,改善其耐久性能,而对杂化材料疏水性能的影响不大.     

Structure and surface properties of fluorinated organic–inorganic hybrid films

Fluorinated organic–inorganic hybrid films were prepared by sol–gel process from tridecafluoroctyltriethoxysilane (PFAS), 3-glycidoxypropyltrimethoxysilane, and tetraethoxysilane (TEOS). It has been found that the fluorinated hybrid films possessed fluorinated side chains originating from PFAS as top layer, and silica network as bottom layer, which had very low surface energy and could be used as water repellent functional coatings. The outermost layer of the water-repellent film may be fully covered by the perfluoroalkyl side chains as the molar ratio of PFAS/TEOS increases up to about 0.005:1. The addition of BPA can enhance the cross-link density of fluorinated hybrid films, and make more perfluoroalkyl groups enriching at the coating film-air interface to lower the surface free energy. However, the improvement of the cross-link density of fluorinated hybrid films tends to exhibit brittleness and micro-cracks. Consequently, it can be concluded that a small BPA additive content is preferred for the formation of fluorinated hybrid films with a smooth surface and less detectable cracks.     

The lower surface free energy achievements from ladder polysilsesquioxanes with fluorinated side chains

The surface free energy of non-F and F-containing ladder polyepoxysilsesquioxanes was calculated by two- and three-liquid methods based on contact angle measurements. These ladder polyepoxysilsesquioxanes exhibited lower surface free energy (<17 mJ/m²) because of their main chain packing on the surface of the films where the side chain alignment was promoted by their ladder structure. And the surface free energy of the polyepoxysilsesquioxanes could be reduced further by the incorporation of perfluoroalkyl group into the side chains (∼13 mJ/m²). The X-ray diffraction results revealed that the F-containing side chain lead to the ladder main chain much more flattening on the surface of the films, explaining the contributions of side and main chain arrangements to the surface free energy.     

Layer structure estimation of three‐dimensional crystal and two‐dimensional molecular film for fluorinated comb copolymers

Comb copolymers containing both hydrogenated and fluorinated side‐chains were prepared by copolymerization using acrylic or methacrylic monomers in several ratios. The crystal structures of these copolymers and layer structures of their organized molecular films were investigated by wide‐angle X‐ray diffraction (WAXD), small‐angle X‐ray scattering (SAXS), and out‐of plane X‐ray diffraction. Further, to selectively estimate the regularity of shorter fluorocarbon side‐chains, organized molecular films of copolymers were investigated by polarized near‐edge X‐ray adsorption fine structure (NEXAFS) spectroscopy. From the results of these measurements, it was inferred that these copolymers formed highly ordered layer structures, and a long spacing was predominantly determined by the arrangement of hydrogenated side‐chains, except in copolymers having extremely high fluorocarbon contents. In the case of the organized molecular films, the fluorinated side‐chains of methacrylate copolymers cannot form a highly ordered arrangement, whereas those of acrylate copolymers were oriented on monolayers. However, in both cases, the hydrogenated side‐chains predominantly formed layer structures in the organized films, and the fluorinated side‐chains did not contribute to the formation of the layer structures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 534–546, 2008     

含氟丙烯酸酯共聚物制备超疏水表面及其形成机理的研究

以丙烯酸全氟烷基乙基酯和甲基丙烯酸甲酯为共聚单体, 分别以用微乳液聚合法和溶液聚合法制备的无规共聚物和用可逆加成-断裂链转移制备的嵌段共聚物作为成膜共聚物, 并以1,1,2-三氟三氯乙烷作为溶剂, 采用溶剂挥发成膜法可以直接制备出超疏水膜, 聚合物膜对水的接触角可达160°. 改变聚合物结构和成膜条件, 探讨了该类超疏水膜的形成机理和影响因素. 发现膜的表面形貌和疏水性与共聚物的组成、结构、分子量以及成膜条件密切相关, 随着共聚物中氟含量的增大, 膜的表面形貌都趋于平滑; 而且, 无规共聚物比嵌段共聚物更易形成粗糙度好的膜; 同时, 较大的聚合物分子量和适宜的高的成膜温度都对形成粗糙结构有利.     

含氟丙烯酸酯聚合物乳胶膜表面性质

采用XPS和界面张力仪分别测定了含氟丙烯酸酯聚合物乳胶膜表面的组成及水在其表面的动态接触角, 并用状态逼近方程模型计算了含氟聚合物乳胶膜的表面张力, 考察了温度对乳胶膜润湿性的影响. 结果表明, 含氟聚合物乳胶膜表层较深处的F 1s信号强度比近表面要弱, 乳胶膜表面张力随表面氟原子浓度增加在一定程度上呈现线性下降；含氟侧链(Rf)较长(碳原子数n＞6)的含氟聚合物, 其表面张力随Rf单元含量增加而下降的趋势显著高于Rf较短(n≤6)的含氟聚合物, 而水在含氟聚合物乳胶膜表面上的后退接触角θr随n增大出现急剧上升, n≥10 时, θr值几乎恒定不再随n增大而改变. 此外, 参与共聚的非氟丙烯酸酯酯基碳链较短时, 水在共聚物乳胶膜表面的θr随氟单元含量增加而增加的趋势更显著；温度超过40 ℃后, 水对聚合物乳胶膜的润湿性随温度上升略有改善.     

成膜溶剂与氟化嵌段共聚物膜的表面富集行为

利用接触角、XPS、SFG、AFM等技术研究了环己酮、甲苯和三氟甲苯为成膜溶剂所得聚甲基丙烯酸甲酯-b-聚（甲基丙烯酸-2-全氟辛基乙酯）（PMMA—b—PFMA）嵌段共聚物膜的表面结构与性能．发现浇铸成膜时成膜溶剂对聚合物氟化组分向表面富集程度的影响相对较小,而旋涂成膜时溶剂的影响很大．不管以何种形式成膜,三氟甲苯溶剂最有利于氟化组分向表面富集,甲苯次之,环己酮最差．这一现象与溶剂的挥发速度无关．聚合物在溶液中的聚集结构、气／液界面结构是造成成膜方式对聚合物表面结构与性能产生巨大影响的主要原因．当聚合物在溶液中形成以PFMA为核、PMMA为冠的胶束结构时,在溶液固化过程中氟化组分向表面富集需要较长的时间,这时由于成膜方法直接影响溶液的固化速度,造成其对氟化组分向表面富集的程度影响很大．当聚合物在溶液中以单分子或松散聚集体存在,在溶液固化过程中氟化组分向表面富集的速度很快,这时成膜方法对氟化组分向表面富集的程度影响很小．以上结果无论对理论研究还是应用研究都具有重要意义．     

Hydrophobic Properties of Thin Films of Comb-Shaped Perfluorohexylethyl Methacrylate-Polydimethylsiloxane Copolymers Deposited from Supercritical Carbon Dioxide Solutions

Comb-shaped copolymers of perfluorohexylethyl methacrylate and methacryloxypropyl-terminated polydimethylsiloxane are synthesized by radical polymerization in supercritical carbon dioxide, solubility of the copolymers in supercritical carbon dioxide is studied, and hydrophobic properties of thin films obtained via precipitation of the copolymers from trifluorotrichloroethane and supercritical carbon dioxide solutions on substrates are examined. On the basis of water and dimethyl sulfoxide contact angle measurements, the specific free surface energy of the formed films is calculated. It is shown that the thin films of the copolymers have a lower surface energy and are characterized by a smaller water contact angle hysteresis than the films based on homopolymer poly(perfluorohexylethyl methacrylate). A comparative testing of coatings based on the homopolymer and copolymer deposited from solutions in supercritical carbon dioxide on the surface of nylon fabrics is performed. It is found that copolymer-coated fabrics have on average higher water contact angles.     

自交联型含氟丙烯酸酯共聚物的合成与表征

含氟丙烯酸酯;自交联;无皂乳液;接触角滞后