Studies on the effects of the alkyl group on the surface segregation of poly(n-alkyl methacrylate) end-capped 2-perfluorooctylethyl methacrylate films

The effects of the alkyl group on the surface segregation of poly(n-alkyl methacrylate) end-capped with various numbers of units of 2-perfluorooctylethyl methacrylate (FMA) (PnAMA-ec-PFMA) were investigated by differential scanning calorimetry, angle-resolved XPS analysis, contact angle measurements, and X-ray diffraction (XRD). The results show that with similar numbers of FMA units at the polymer chain end the extent of fluorine segregation (Q) increased with increasing the number of carbon atoms in the side n-alkyl chains of poly(n-alkyl methacrylate). The surface fluorine content within 5 nm deep of the film of poly(n-octadecyl methacrylate) end-capped with one FMA unit (PODMA(160)-ec-PFMA(1.0)) was 208-fold higher than that of the bulk level. These observed differences in Q values were found due to the aggregate structure of the end-capped polymers in the solution, the flexibility, and the crystallinity of the n-alkyl side chains. When the nonfluorinated block was completely amorphous, the molecular aggregate structure of the end-capped polymers in the solution played an important role in the surface segregation of the fluorinated moieties on the resulting film. However, when the nonfluorinated block was crystalline, crystallinity would enhance greatly the segregation of the fluorinated moieties.     

B段选择性成膜溶剂对 ABC 型氟化三嵌段共聚物氟化组分表面富集行为的影响

利用ATRP技术合成聚甲基丙烯酸甲酯-b-聚甲基丙烯酸丁酯(或聚甲基丙烯酸十八烷基酯)-b-聚(甲基丙烯酸2-全氟辛基乙酯)(PMMA230-b-PBMA12(或PODMA12)-b-PFMAn)嵌段共聚物.通过X射线光电子能谱(XPS)、X射线衍射(XRD)、动态光散射(DLS)等技术研究了中间段选择性成膜溶剂对氟化...     

Surface active semifluorinated diblock copolymers prepared by group transfer polymerization

Diblock copolymers consisting of poly(methyl methacrylate) and poly(2-perfluorobutylethyl methacrylate) with narrow molecular weight distribution have been synthesized by group transfer polymerization. Different ratios of the PMMA block to the fluorinated block have been prepared. It was found that all polymers are surface active. Critical micelle concentrations are not dependent on the fluorinated block length. Critical surface tensions, extrapolated from Zisman plots and the dispersion force component of the surface energies extrapolated from Girifalco-Good-Fowkes-Young plots were decreasing with increasing length of the fluorinated block.     

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．     

Self-assembly of pODMA-b-ptBA-b-pODMA triblock copolymers in bulk and on surfaces. A quantitative SAXS/AFM comparison

The phase state of a series of poly(n-octadecyl methacrylate)-b-poly(tert-butyl acrylate)-b-poly(n-octadecyl methacrylate) (pODMA-b-ptBA-b-pODMA) triblock copolymers, synthesized through atom transfer radical polymerization, has been investigated in bulk and on surfaces using small-angle X-ray scattering and atomic force microscopy, respectively. The mean-field theory was employed to construct the bulk phase diagram. Excellent agreement was found between the bulk and surface morphologies as well as for the domain spacing (domain spacing scaled as d approximately equal to N(0.64)), suggesting that the strong polymer-polymer interactions in bulk are also the dominant interactions on surfaces.     

Solvent effect on the film formation and the stability of the surface properties of poly(methyl methacrylate) end-capped with fluorinated units

The surface structure and stability (the resistance to surface reconstruction) of end-capped poly(methyl methacrylate) films were greatly affected by the solvents used for film preparation. Films of end-capped PMMA with about four 2-perfluorooctylethyl methacrylate units cast with benzotrifluoride solution exhibited excellent stability and resistance to polar environments compared with those cast with cyclohexanone and toluene solutions. The observed difference in stability between these fluorinated surfaces is attributed to their surface microstructures formed during the film formation processes, which are closely related to the associative behavior of the end-capped PMMA in the solution. A relatively perfect close-packed and well-ordered structure of the perfluoroalkyl side chains at the surface of the PMMA(857)-ec-FMA(3.3) film was formed when the film was cast with benzotrifluoride solution, in which only unimers existed. This study indicates that such a solvent effect may be used to promote the formation of a well-ordered packing structure of the fluorinated moieties at the film surface. The ordering of the packing structure is to a certain extent more important than the content of the fluorinated moieties at the surface for improving the surface stability.     

A facile method of forming nanoscale patterns on poly(ethylene glycol)-based surfaces by self-assembly of randomly grafted block copolymer brushes

Poly(oligo(ethylene glycol) methacrylate) (POEGMA) block poly(methyl methacrylate) (PMMA) brushes were synthesized on the silicon wafer surfaces by the surface-initiated atom transfer radical polymerization (ATRP) method. Atomic force microscopy, ellipsometry, and water contact angle methods were employed to study the surface morphology and stimulus-response behavior. It was found that simple solvent treatments could induce phase segregation of the POEGMA and PMMA segments thus introducing nanoscale patterns. The feature size could be less than 10 nm and was tunable on the nanoscale. Various patterns including spherical aggregates, wormlike aggregates, stripe patterns, perforated layers, and complete overlayers were obtained through adjusting the upper block layer thickness. These patterns could switch between the different morphologies reversibly after the treatment with selective solvents.     

Surface segregation of poly(2-methoxyethyl acrylate) in a mixture with poly(methyl methacrylate)

Poly(2-methoxyethyl acrylate) (PMEA) exhibits excellent blood compatibility. To understand why such a surface functionality exists, the surface of PMEA should be characterized in detail, structurally and dynamically, under not only ambient conditions, but also in water. However, a thin film of PMEA supported on a solid substrate can be easily broken, namely it is dewetted. Our strategy to overcome this difficulty is to mix PMEA with poly(methyl methacrylate) (PMMA). Differential scanning calorimetry and cloud point measurements revealed that the PMEA/PMMA blend has a phase diagram with a lower critical solution temperature. The blend surface was also characterized by X-ray photoelectron spectroscopy in conjunction with microscopic observations. Although PMEA is preferentially segregated over PMMA at the blend surface due to its lower surface free energy, the extent of segregation in the as-prepared films was not sufficient to cover the surface. Annealing the blend film at an appropriate temperature, higher than the glass transition temperature and lower than the phase-separation temperature of the blend, enabled us to prepare a stable and flat surface that was perfectly covered with PMEA.     

低能量链端对聚苯乙烯薄膜铺展和润湿行为的影响

通过低能量功能端基的表面富集作用,研究了聚苯乙烯（ＰＳ）薄膜在聚甲基丙烯酸甲酯（ＰＭＭＡ）表面上的铺展和润湿动力学．用光学显微镜跟踪了ＰＳ薄膜的润湿行为,并对高分子熔体膜中非连续部分尺寸的增大速率进行了测定．分别用ＸＰＳ和ＡＦＭ对ＰＳ薄膜的表面组成和ＰＳ液滴的平衡接触角进行了测定．发现具有低表面能的氟碳端基在薄膜表面富集使ＰＳ薄膜的表面张力下降,并使ＰＳ液滴在ＰＭＭＡ表面上的平衡接触角减小,从而使高分子熔体膜中非连续部分尺寸的增长速率下降,得到了与液液界面铺展和润湿理论一致的实验结果．     

Preparation and applications of novel fluoroalkyl end‐capped vinyltrimethoxysilane oligomer/hydroxyapatite nanocomposites

Novel fluoroalkyl end‐capped vinyltrimethoxysilane oligomer/hydroxyapatite (HAp) nanocomposites were prepared by the reaction of calcium nitrate tetrahydrate and phosphoric acid in the presence of the corresponding oligomer. These fluorinated oligomer/HAp composites thus obtained are nanometer size‐controlled fine particles (83–173 nm), and were found to exhibit good dispersibility in methanol, ethanol, and isopropyl alcohol. These fluorinated HAp nanocomposites were applied to the surface modification of glass and poly(methyl methacrylate) (PMMA) to exhibit good hydro‐ and oleophobic characteristics imparted by fluorine on their surface. In addition, the surface structural changes of the modified polyethylene terephtalate and PMMA films treated with these fluorinated nanocomposites before and after soaking in a simulated body fluid (SBF) were analyzed by using SEM, XRD, and EDX to observe the formation of spherical HAp deposits on the surface. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation and applications of novel fluoroalkyl end-capped oligomers/calcium carbonate nanocomposites

Calcium chloride reacted with sodium carbonate in the presence of a variety of self-assembled molecular aggregates formed by fluoroalkyl end-capped acrylic acid, 2-methacryloyloxyethane sulfonic acid, dimethylacrylamide, and acryloylmorpholine oligomers in aqueous solutions to afford the corresponding fluorinated oligomers/calcium carbonate composites in excellent to moderate isolated yields. These fluorinated calcium carbonate composites thus obtained were shown to have a good dispersibility not only in water but also in traditional organic media including fluorinated solvents. Dynamic light scattering measurements (DLS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that these fluorinated composites are nanometer-size-controlled particles and well dispersed in these media. Cross-linked fluoroalkyl end-capped acrylic acid co-oligomer containing poly(oxyethylene) units was also applied to the preparation of new cross-linked fluorinated calcium carbonate nanocomposites under similar conditions. The obtained cross-linked fluorinated calcium carbonate nanocomposites were found to have an extremely higher dispersibility in aqueous and organic media including fluorinated solvents, compared to that of the corresponding fluoroalkyl end-capped oligomer nanocomposites. In particular, it was verified that these fluorinated calcium carbonate nanocomposites are applicable to the dispersion above poly(methyl methacrylate) (PMMA) film surface. Interestingly, field-emission SEM (FE-SEM) images of the cross-section of the modified PMMA films showed that calcium carbonate particles dispersed into these PMMA films could be arranged regularly above the modified film surface. More interestingly, cross-linked fluorinated oligomeric aggregates were able to provide suitable host moieties for the crystallization of calcium carbonate.     

A FACILE APPROACH FOR THE SURFACE MODIFICATION OF POLY(VINYLIDENE FLUORIDE) MEMBRANE VIA SURFACE-INITIATED ATOM TRANSFER RADICAL POLYMERIZATION

A novel approach for the surface modification of poly(vinylidene fluoride)(PVDF)membrane was successfully realized through alkaline treatment,UV-induced bromine addition,and followed by surface-initiated atom transfer radical polymerization(ATRP)of methyl methacrylate(MMA).Chemical changes on the PVDF membrane before and after modification were analyzed with attenuated total reflectance Fourier transform infrared spectroscopy(ATR/FT-IR)and X-ray photoelectron spectroscopy(XPS).Primary kinetic study revea...     

Atom transfer radical polymerization directly from poly(vinylidene fluoride): Surface and antifouling properties

The direct preparation of grafting polymer brushes from commercial poly (vinylidene fluoride) (PVDF) films with surface‐initiated atom transfer radical polymerization (ATRP) is demonstrated. The direct initiation of the secondary fluorinated site of PVDF facilitated grafting of the hydrophilic monomers from the PVDF surface. Homopolymer brushes of 2‐(N,N‐dimethylamino)ethyl methacrylate (DMAEMA) and poly (ethylene glycol) monomethacrylate (PEGMA) were prepared by ATRP from the PVDF surface. The chemical composition and surface topography of the graft‐functionalized PVDF surfaces were characterized by X‐ray photoelectron spectroscopy, attenuated total reflectance/Fourier transform infrared spectroscopy, and atomic force microscopy. A kinetic study revealed a linear increase in the graft concentration of poly[2‐(N,N‐dimethylamino)ethyl methacrylate] (PDMAEMA) and poly[poly(ethylene glycol) monomethacrylate] (PPEGMA) with the reaction time, indicating that the chain growth from the surface was consistent with a controlled or living process. The living chain ends were used as macroinitiators for the synthesis of diblock copolymer brushes. The water contact angles on PVDF films were reduced by the surface grafting of DMAEMA and PEGMA. Protein adsorption experiments revealed a substantial antifouling property of PPEGMA‐grafted PVDF films and PDMAEMA‐grafted PVDF films in comparison with the pristine PVDF surface. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3434–3443, 2006     

Facile hydrophobic modification of hybrid poly(urethane-urea)methacrylate aqueous dispersions and films through blending with novel waterborne fluorinated acrylic copolymers

Aqueous dispersions of fluorinated particles (PBF) based on copolymers of butyl acrylate with 2-(perfluorononenyloxy)ethyl methacrylate (FNEMA), 2,2,3,3-tetrafluoropropyl acrylate, and 2,2,3,3,4,4,5,5-octafluoropentyl acrylate, respectively, were synthesized by emulsion polymerization in the presence of unfluorinated and fluorinated anionic surfactant binary mixtures. These fluorinated dispersions showed good to excellent colloidal stability, as determined by freeze–thaw, centrifugation, and critical coagulation concentration measurements. Blending of small amounts (1–10 wt.%) of PBF latex particles with a waterborne hybrid poly(urethane-urea)-methacrylate (PUUA) resulted in a series of slightly fluorinated modified PUUA with good film-forming properties and low surface energy. The precursor PUUA had been synthesized separately by simultaneous chain extension of a poly(ester-urethane)-diisocyanate with ethylenediamine and soapless free radical polymerization of methyl methacrylate swelling the resulting branched or slightly cross-linked poly(urethane-urea) self-dispersible ionomer particles. The results of dynamic light scattering and zeta potential measurements suggest that the merging of PUUA and PBF particles and either engulfing or interdiffusion of the incompatible macromolecular phases occurred to some extent already in the colloidal state. Highly hydrophobic films with surface energy as low as 17 mJ/m² were obtained upon the hybridization of PUUA with the FNEMA copolymer. Thermal annealing allowed minimizing the effects of fast surface dynamics, leading ultimately to water absorption, and promoting synergistic enhancement of the resulting hybrid film hardness, as required for coating applications.     

Preparation of Super-Water-Repellent Fluorinated Inorganic-Organic Coating Films on Nylon 66 by the Sol-Gel Method Using Microphase Separation

We have prepared super-water-repellent fluorinated inorganic-organic coating films on nylon 66 substrate from poly(methyl methacrylate) (PMMA), tetraethoxysilane (TEOS), and 2-perfluorooctylethyltriethoxysilane (17F) by the sol-gel method. The contact angle for water of the film was 149°. The fluorinated inorganic-organic film including PMMA particles exhibits the super-water-repellence on nylon 66 and the high ultrasonics-resistance in spite of the low 17F content of the molar ratio of 0.001 per mol of TEOS. The surfaces of the films were characterized by using XPS and SEM in combination with the surface roughness data. It was considered that the fluorinated component was segregated to form separated microphase regions, appropriate surface roughness being resulted to develop high water-repellence.     

A FACILE APPROAC0H FOR THE SURFACE MODIFICATION OF POLY(VINYLIDENE FLUORIDE)MEMBRANE VIA SURFACE-INITIATED ATOM TRANSFER RADICAL POLYMERIZATION

A novel approach for the surface modification of poly(vinylidene fluoride)(PVDF)membrane was successfully realized through alkaline treatment,UV-induced bromine addition,and followed by surface-initiated atom transfer radical polymerization(ATRP)of methyl methacrylate(MMA).Chemical changes on the PVDF membrane before and after modification were analyzed with attenuated total reflectance Fourier transform infrared spectroscopy(AIR/Fr-IR)and X-ray photoelectron spectroscopy(XPS).Primary kinetic study revealed that the chain growth of poly(methyl methacrylate)(PMMA)from the PVDF surface is consistent with a"controlled"process.     

The outermost atomic layer of thin films of fluorinated polymethacrylates

In this paper, we investigate the surface properties of a series of copolymers of perfluoroalkyl methacrylate (CH2 = C(CH3)COOCH2CnF(2n + 1), n = 1, 6, or 10) and methyl methacrylate (MMA) and of blends of perfluorooctyl-end-capped poly(methyl methacrylate) (PMMA) and pure PMMA. The introduction of perfluoroalkyl groups significantly lowers the polymer surface energy as determined by the acid-base approach. X-ray photoelectron spectroscopy (XPS) confirms a higher fluorine concentration in the surface region (the outer 3.8 nm) as compared to in the bulk. The fluorine density in the outermost atomic layer is quantitatively determined by low-energy ion scattering (LEIS). A linear relationship is found between the fluorine density in the outermost atomic layer and the surface energy of the partially fluorinated polymethacrylates, irrespective of the length of the perfluoroalkyl chain. This linearity confirms Langmuir's "principle of independent surface action". Deviation from this linear relationship exists for both highly and sparsely fluorinated polymethacrylates and can be ascribed to the local (surface) ordering of the fluorinated tails and MMA units, respectively. This study may offer one further step toward a deeper understanding of the correlations between macroscopic surface properties and microscopic surface chemical composition.     

Crystallization,morphology, structure and miscibility of poly(ethylene oxide) based blends

Results of an investigation on the morphology, structure, isothermal crystallization, thermal behaviour and miscibility of poly(ethylene oxide) (PEO) based binary blends are reported. In particular poly(vinyl acetate)(PVAc), poly(methyl methacrylate) (PMMA) at different tacticity and poly(ethyl methacrylate) (PEMA) were added to PEO. It was found that with the only exception of isotactic poly(methyl methacrylate) (IPMMA), the addition of the above cited components causes a depression in both the spherulite growth rate and the overall kinetic rate constant. The experimental G and Kn were analyzed by means of the latest kinetic theory in order to determine the influence of composition on the process of surface secondary nucleation. The optical microscopy of thin films of the sample revealed that the blends crystallized with volume filling crystals at least up to 50/50 blend composition. The small angle X-ray scattering curves were analyzed using a recently developed methodology. The structural properties of the blends were attributed to the presence of the non crystallizable material in the interlamellar or interfibrillar regions of PEO. From the glass transition temperature it has been deduced that an homogeneous amorphous phase is present for all the blends except for the PEO/IPMMA amorphous system. For the system PEO/atactic poly(methyl methacrylate) (APMMA) the miscibility was also predicted by theoretical approaches.     

Study of bulk morphology of polymer latex films using laser confocal fluorescence microscopy

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Directional Self‐Assembly of Fluorinated Star Block Polymer Thin Films Using Mixed Solvent Vapor Annealing

We demonstrate the directional alignment of perpendicular‐lamellae domains in fluorinated three‐armed star block polymer (BP) thin films using solvent vapor annealing with shear stress. The control of orientation and alignment was accomplished without any substrate surface modification. Additionally, three‐armed star poly(methyl methacrylate‐block‐styrene) [PMMA‐PS] and poly(octafluoropentyl methacrylate‐block‐styrene) were compared to their linear analogues to examine the impact of fluorine content and star architecture on self‐assembled BP feature sizes and interdomain density profiles. X‐ray reflectometry results indicated that the star BP molecular architecture increased the effective polymer segregation strength and could possibly facilitate reduced polymer domain spacings, which are useful in next‐generation nanolithographic applications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1663–1672