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1.
Hsiang‐Wei Lu Jennifer L. Logan A. E. Hosoi Shenda M. Baker 《Journal of Polymer Science.Polymer Physics》2011,49(2):136-143
Spreading amphiphilic diblock copolymers on a two‐dimensional liquid interface has been observed to produce nanoscale features via self‐assembly. Here, we develop a model that incorporates the effects of polymer entanglement and surface diffusion in polymer blends to quantitatively predict the size of experimentally observed structures. Simulations show that different polymers in the blend cooperate to self‐assemble into nanoscale features of varying sizes. Characteristic nanoscopic dimensions can be tuned by adjusting two easily controllable macroscopic quantities: the blend composition and the initial surface concentration. Theoretical predictions are in agreement with experimentally measured feature dimensions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 相似文献
2.
Sambhy V Peterson BR Sen A 《Langmuir : the ACS journal of surfaces and colloids》2008,24(14):7549-7558
We demonstrate a versatile methodology combining both covalent surface anchoring and polymer cross-linking that is capable of forming long-lasting coatings on reactive and nonreactive surfaces. Polymers containing reactive methoxysilane groups form strong Si-O-Si links to oxide surfaces, thereby anchoring the polymer chains at multiple points. The interchain cross-linking of the methoxysilane groups provides additional durability to the coating and makes the coatings highly resistant to solvents. By tailoring the chemical structure of the polymer, we were able to control the surface energy (wetting) of a variety of surfaces over a wide range of water contact angles of 30-140 degrees . In addition, we synthesized covalently linked layer-by-layer polymeric assemblies from these novel methoxysilane polymers. Finally, antibacterial agents, such as silver bromide nanoparticles and triiodide ions, were introduced into these functional polymers to generate long-lasting and renewable antiseptic coatings on glass, metals, and textiles. 相似文献
3.
Robert P. Sebra Kristi S. Anseth Christopher N. Bowman 《Journal of polymer science. Part A, Polymer chemistry》2006,44(4):1404-1413
Surface modification using living radical polymerization (LRP) chemistry is a powerful technique for surface modification of polymeric substrates. This research demonstrates the ability to use LRP as a polymer substrate surface‐modification platform for covalently grafting polymer chains in a spatially and temporally controlled fashion. Specifically, dithiocarbamate functionalities are introduced onto polymer surfaces using tetraethylthiuram disulfide. This technique enables integration of LRP‐based grafting for the development of an integrated, covalent surface‐modification method for microfluidic device construction. The unique photolithographic method enables construction of devices that are not substrate‐limited. To demonstrate the utility of this approach, both controlled fluid flow and cell patterning applications were demonstrated upon modification with various chemical functionalities. Specifically, poly(ethylene glycol) (375) monoacrylate and trifluoroethyl acrylate were grafted to control fluidic flow on a microfluidic device. Before patterning, surface‐functionalized samples were characterized with both goniometric and infrared spectroscopy to ensure that photografting was occurring through pendant dithiocarbamate functionalities. Near‐infrared results demonstrated conversion of grafted monomers when dithiocarbamate‐functionalized surfaces were used, as compared to dormant control surfaces. Furthermore, attenuated total reflectance/infrared spectroscopy results verified the presence of dithiocarbamate functionalities on the substrate surfaces, which were useful in grafting chains of various functionalities whose contact angles ranged from 7 to 86°. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1404–1413, 2006 相似文献
4.
Flow‐coated, two‐dimensional polymer ribbon structures undergo a shape‐transformation into a three‐dimensional helix upon their release into a solution. Driven by surface forces and due to geometric asymmetry, the helix radius and spring constant depend upon the ribbon cross‐section dimensions, surface energy, and material elastic modulus. Such spring‐like microhelices offer multiple functionalities combined with mechanical stretching and shape recovery. Fabricating such microhelices requires a sequence of processing steps, beginning with flow‐coating of ribbons on a substrate, followed by etching of a “scum layer” to allow for an independent release into a solution, upon which shape‐transformation occurs. During the deposition‐etch‐release sequence, various control parameters influence the nanoribbon size and geometry, hence the helix properties. The experimental study presented here focuses on the influence of meniscus height, substrate velocity, substrate surface energy, and etch time on nanoribbon size (height and width), scum layer thickness, and helix radius. The results show that meniscus height and contact angle dictate flux toward the meniscus edge and volume available for spatial assembly, allowing control over the aspect ratio of ribbons. We vary the aspect ratio by two orders of magnitude, while maintaining geometric asymmetry needed for helix shape‐transformation. We provide robust scaling for the nanoribbon size and geometry and report the advantages and disadvantages of different parameters, in the control of polymer nanoribbon and helix fabrication. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1270–1278 相似文献
5.
Shaofeng Duan Shuang Cai Yumei Xie Taryn Bagby Shenqiang Ren M. Laird Forrest 《Journal of polymer science. Part A, Polymer chemistry》2012,50(13):2715-2724
Functionalized polymeric nanocarriers have been recognized as drug delivery platforms for delivering therapeutic concentrations of chemotherapies. Of this category, star‐shaped multiarm polymers are emerging candidates for targeted delivery of anticancer drugs, due to their compact structure, narrow size distribution, large surface area, and high water solubility. In this study, we synthesized a multiarm poly(acrylic acid) star polymer via macromolecular design via the interchange (MADIX)/reversible addition fragmentation chain transfer (MADIX/RAFT) polymerization and characterized it using nuclear magnetic resonance (NMR) and size exclusion chromatography. The poly(acrylic acid) star polymer demonstrated excellent water solubility and extremely low viscosity, making it highly suited for targeted drug delivery. Subsequently, we selected a hydrophilic drug, cisplatin, and a hydrophobic nitric oxide (NO)‐donating prodrug, O2‐(2,4‐dinitrophenyl) 1‐[4‐(2‐hydroxy)ethyl]‐3‐methylpiperazin‐1‐yl]diazen‐1‐ium‐1,2‐diolate, as two model compounds to evaluate the feasibility of using poly(acrylic acid) star polymers for the delivery of chemotherapeutics. After synthesizing and characterizing two poly(acrylic acid) star polymer‐based nanoconjugates, poly(acrylic acid)–cisplatin (acid–Pt) and poly(acrylic acid–NO (acid–NO) prodrug, the in vitro drug release kinetics of both the acid–Pt and the acid–NO were determined at physiological conditions. In summary, we have designed and evaluated a polymeric nanocarrier for sustained‐delivery of chemotherapies, either as a single treatment or a combination therapy regimen. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
6.
Markus Gahleitner Johannes Wolfschwenger Joachim Fiebig Wolfgang Neißl 《Macromolecular Symposia》2002,185(1):77-87
The interaction between the type of nucleating agent and base polymer was investigated for a combination of three commercial nucleants and polypropylenes each. Both the crystallisation behavior under DSC conditions and the mechanical and optical properties were determined for all materials. For both the influences of the nucleant and of the base polymer, the present study has provided qualitative indications as to the triggered crystal morphology and shear-induced superstructure. Especially the latter can be related to the differences between optical and mechanical effects of the nucleation process. 相似文献
7.
Antoine Bousquet Emmanuel Ibarboure Francisco J. Teran Leire Ruiz María Teresa Garay José Manuel Laza José Luis Vilas Eric Papon Juan Rodríguez‐Hernández 《Journal of polymer science. Part A, Polymer chemistry》2010,48(14):2982-2990
We report the preparation of nanostructured adaptive polymer surfaces by diffusion of an amphihilic block copolymer toward the interface. The surface segregation of a diblock copolymer, polystyrene‐block‐poly(acrylic acid) (PS‐b‐PAA), occurred when blended with high molecular weight polystyrene employed as a matrix. On annealing, the polymer surfaces changed both the chemical composition and the hydrophilicity depending on the environment and pH, respectively. By exposure to either water vapor or air, the surface wettability varied between hydrophilic and hydrophobic. In addition, surface enrichment on diblock copolymer by water vapor annealing led to self‐assembly occurring at the interface. Hence, nanostructured domains can be observed by AFM in liquid media. Moreover, the PAA segments placed at the interface respond to pH and can switch from an extended hydrophilic state at basic pH values to a collapsed hydrophobic state in acidic media. Accordingly, the surface morphology changed from swelled micelles to nanometer size holes. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2982–2990, 2010 相似文献
8.
We experimentally study the dissolution of carbon dioxide bubbles into common liquids (water, ethanol, and methanol) using microfluidic devices. Elongated bubbles are individually produced using a hydrodynamic focusing section into a compact microchannel. The initial bubble size is determined based on the fluid volumetric flow rates of injection and the channel geometry. By contrast, the bubble dissolution rate is found to depend on the inlet gas pressure and the fluid pair composition. For short periods of time after the fluids initial contact, the bubble length decreases linearly with time. We show that the initial rate of bubble shrinkage is proportional to the ratio of the diffusion coefficient and the Henry's law constant associated with each fluid pair. Our study shows the possibility to rapidly impregnate liquids with CO(2) over short distances using microfluidic technology. 相似文献
9.
Md. Wali Ullah Naoki Haraguchi 《Journal of polymer science. Part A, Polymer chemistry》2019,57(12):1296-1304
A variety of polymer microspheres were successfully synthesized by the surface‐initiated atom transfer radical polymerization (SI‐ATRP) of monomers by using monodisperse polymer microsphere having benzyl halide moiety as a multifunctional polymeric initiator. First, a series of monodisperse polymer microsphere having benzyl chloride with variable monomer ratio (P(St‐DVB‐VBC)) were synthesized by the precipitation polymerization of styrene (St), divinylbenzene (DVB), and 4‐vinylbenzyl chloride (VBC). Next, hairy polymer microspheres were synthesized by the surface‐initiated ATRP of various monomers with P(St‐DVB‐VBC) microsphere as a multifunctional polymeric initiator. The hair length determined by the SEC analysis of free polymer was increased with the increase of M/I. These hairy polymer microspheres were characterized by SEM, FT‐IR, and Cl content measurements. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1296–1304 相似文献
10.
Wu Daming Meng Qingyun Liu Ying Ding Yumei Chen Weihong Xu Hong Ren Dongyun 《Journal of Polymer Science.Polymer Physics》2003,41(10):1051-1058
An in situ bubble‐stretching (ISBS) model has been proposed on the basis of an analysis of the dispersion process of inorganic additives in polymers. The ISBS model is applicable to a dispersion of solid granular aggregates in polymer melts because the dispersed phase itself serves as a nucleation agent, giving rise to bubbles that expand at the surface of the microgranules and their aggregates. In terms of bidirectional stretching, the ISBS process can increase the degrees of freedom of granule dispersion, which favors more homogeneous dispersion. According to theoretical predictions and indirect experimental estimations of the dispersion of nanoscale CaCO3 and nanoscale hydrotalcite in high‐density polyethylene (HDPE), when the bubble expands, the stretching rate of the polymer melt on the bubble wall can reach 105–106 s?1. The field emission scanning electron microscopic images indicated that the granular size of dispersed CaCO3 and hydrotalcite in HDPE with the ISBS method is about 60–80 nm, two orders of magnitude smaller than that attained with a shearing rate of 103 s?1 in a capillary rheometer. It is also predicted that elastic bubble oscillations may be generated through suitable control of process parameters and that their oscillatory frequency can be in the ultrasound range. This type of bubble oscillation can also promote dispersion. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1051–1058, 2003 相似文献
11.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(42):13093-13098
We describe single‐chain polymer nanoparticles (SCNPs) possessing intramolecular dynamic covalent crosslinks that can transform into polymer films through a molecular recognition‐mediated crosslinking process. The SCNPs utilise molecular recognition with surface‐immobilised proteins to concentrate upon a substrate, bringing the SCNPs into close spatial proximity with one another and allowing their dynamic covalent crosslinkers to undergo intra‐ to interpolymer chain crosslinking leading to the formation of polymeric film. SCNPs must possess both the capacity for specific molecular recognition and a dynamic nature to their intramolecular crosslinkers to form polymer films, and an investigation of the initial phase of film formation indicates it proceeds from features which form upon the surface then grow predominantly in the xy directions. This approach to polymer film formation presents a potential method to “wrap” surfaces displaying molecular recognition motifs—which could potentially include viral, cellular and bacterial surfaces or artificial surfaces displaying multivalent recognition motifs—within a layer of polymer film. 相似文献
12.
用自组装技术在金(纯金和经阳极氧化的金)表面上获得了新型两亲聚合物PAMC_(16)S的有序膜。用接触角测试,XPS谱和电化学分析等方法对自组装膜进行了表征。根据膜表面的润湿性,金表面的自组装膜是疏水的,亲水的磺酸基团连于金表面,而疏水的碳氢链从表面伸展出。XPS实验结果支持金表面上单层膜的疏水结构。聚合物单层膜复盖的金电极起到含有针孔缺陷的阻膈型电极的作用。单层膜在法拉第反应中显示很强的吸附稳定性,说明聚合物LB膜在潜在应用中有其特有的特点。 相似文献
13.
Nonadhesive and water-repellent surfaces are required for many tribological applications. We study mechanisms of wetting of patterned superhydrophobic Si surfaces, including the transition between various wetting regimes during microdroplet evaporation in environmental scanning electron microscopy (ESEM) and for contact angle and contact angle hysteresis measurements. Wetting involves interactions at different scale levels: macroscale (water droplet size), microscale (surface texture size), and nanoscale (molecular size). We propose a generalized formulation of the Wenzel and Cassie equations that is consistent with the broad range of experimental data. We show that the contact angle hysteresis involves two different mechanisms and how the transition from the metastable partially wetted (Cassie) state to the homogeneously wetted (Wenzel) state depends upon droplet size and surface pattern parameters. 相似文献
14.
Dr. Zhuang Xie Yu Zhou James L. Hedrick Peng‐Cheng Chen Shu He Dr. Mohammad M. Shahjamali Shunzhi Wang Prof. Zijian Zheng Prof. Chad A. Mirkin 《Angewandte Chemie (International ed. in English)》2015,54(44):12894-12899
The concept of using cantilever‐free scanning probe arrays as structures that can modulate nanoscale ink flow and composition with light is introduced and evaluated. By utilizing polymer pen arrays with an opaque gold layer surrounding the base of the transparent polymer pyramids, we show that inks with photopolymerizable or isomerizable constituents can be used in conjunction with light channelled through the pyramids to control ink viscosity or composition in a dynamic manner. This on‐tip photo‐modulated molecular printing provides novel chemically and mechanically controlled approaches to regulating ink transport and composition in real time and could be useful not only for rapidly adjusting feature size but also for studying processes including photoreactions and mass transport at the nanoscale, self‐assembly, and cell–material interactions. 相似文献
15.
Surface and interfacial segregation of polyethersulfone deuterated chain ends determined by neutron reflectivity
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Katrina M. Knauer Joel Pollino Jonathan Schwartz Levi M. J. Moore Sarah E. Morgan 《Journal of Polymer Science.Polymer Physics》2017,55(3):293-301
The surface localization of polymer chain ends has been shown to be an effective method for surface composition control in amorphous polymer films. This work determines chain end distribution in thin polyethersulfone (PESU) films end‐capped with deuterated compounds of varying size and composition. Neutron reflectivity revealed the preferential localization of chain ends to the PESU‐air interface, independent of chain end identity. The length scale of the chain end concentration gradient was determined to differ from that predicted for flexible chain polymers. Atomic force microscopy and contact angle analysis demonstrated that chain end localization allows for improved control of nanoscale and macroscale surface properties of PESU films. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 293–301 相似文献
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17.
Low‐rate dynamic contact angles of 12 liquids on a poly(methyl methacrylate/ethyl methacrylate, 30/70) P(MMA/EMA, 30/70) copolymer were measured by an automated axisymmetric drop shape analysis‐profile (ADSA‐P). It was found that five liquids yield nonconstant contact angles, and/or dissolve the polymer on contact. From the experimental contact angles of the remaining seven liquids, it is found that the liquid–vapor surface tension times cosine of the contact angle changes smoothly with the liquid–vapor surface tension (i.e., γl|Kv cos θ depends only on γl|Kv for a given solid surface or solid surface tension). This contact angle pattern is in harmony with those from other methacrylate polymer surfaces previously studied.45,50 The solid–vapor surface tension calculated from the equation‐of‐state approach for solid–liquid interfacial tensions14 is found to be 35.1 mJ/m2, with a 95% confidence limit of ± 0.3 mJ/m2, from the experimental contact angles of the seven liquids. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2039–2051, 1999 相似文献
18.
Pia Winterwerber Sean Harvey David Y. W. Ng Tanja Weil 《Angewandte Chemie (International ed. in English)》2020,59(15):6144-6149
Temporal and spatial control over polydopamine formation on the nanoscale can be achieved by installing an irradiation‐sensitive polymerization system on DNA origami. Precisely distributed G‐quadruplex structures on the DNA template serve as anchors for embedding the photosensitizer protoporphyrin IX, which—upon irradiation with visible light—induces the multistep oxidation of dopamine to polydopamine, producing polymeric structures on designated areas within the origami framework. The photochemical polymerization process allows exclusive control over polydopamine layer formation through the simple on/off switching of the light source. The obtained polymer–DNA hybrid material shows significantly enhanced stability, paving the way for biomedical and chemical applications that are typically not possible owing to the sensitivity of DNA. 相似文献
19.
A convection–diffusion porous media model for moisture transport in polymer composites: Model development and validation
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Liangbiao Chen Hsing‐Wei Chu Xuejun Fan 《Journal of Polymer Science.Polymer Physics》2015,53(20):1440-1449
Moisture may cause many detrimental effects to polymers and their composites, thus inhibiting the applications of polymeric materials in hot and humid environments. In this article, a convection–diffusion porous media model is derived to better characterize rapid moisture transport in polymer composites at high temperatures. The model considers both continuum diffusion in solid and high‐pressure convection taking place in the pore network. Coupling of convection and diffusion is achieved by combining the law of conservation of mass, Darcy's law, the liquid–vapor chemical equilibrium, and the ideal gas law. The presented model is validated by conducting experimental tests on an epoxy compound. It is found that the proposed convection–diffusion model is more effective than diffusion‐only and convection‐only models for interpreting rapid desorption tests at high temperatures. A numerical study is also performed to predict maximum vapor pressure during a rapid heating process. Vapor pressure is found to be as high as 6.5 MPa at a heating rate of 10 K/s. It is concluded that the convection–diffusion model is able to capture both vapor dynamics and diffusion mechanism in porous polymeric materials, and can be potentially used to further investigate polymer‐moisture interactions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1440–1449 相似文献
20.
Pruthesh H. Vargantwar Kristen E. Roskov Tushar K. Ghosh Richard J. Spontak 《Macromolecular rapid communications》2012,33(1):61-68
Ionic polymer–metal composites (IPMCs) represent an important class of stimuli‐responsive polymers that are capable of bending upon application of an electric potential. Conventional IPMCs, prepared with Nafion and related polyelectrolytes, often suffer from processing challenges, relatively low actuation levels and back relaxation during actuation. In this study, we examine and compare the effects of fabrication and solvent on the actuation behavior of a block ionomer with a sulfonated midblock and glassy endblocks that are capable of self‐organizing and thus stabilizing a molecular network in the presence of a polar solvent. Unlike Nafion, this material can be readily dissolved and cast from solution to yield films that vary in thickness and exhibit enormous solvent uptake. Cycling the initial chemical deposition of Pt on the surfaces of swollen films (the compositing process) increases the extent to which the electrodes penetrate the films, thereby improving contact along the polymer/electrode interface. The maximum bending actuation measured from IPMCs prepared with different solvents is at least comparable, but is often superior, to that reported for conventional IPMCs, without evidence of back relaxation. An unexpected characteristic observed here is that the actuation direction can be solvent regulated. Our results confirm that this block ionomer constitutes an attractive alternative for use in IPMCs and their associated applications. 相似文献