Shear‐Controlled Micro/Nanometer‐Scaled Super‐Hydrophobic Surfaces with Tunable Sliding Angles from Single Component Isotactic Poly(propylene)

Summary: With the proper selection of shear and thermal conditions, super‐hydrophobic polymeric surfaces (contact angle > 150°) with tunable sliding angles (from less than 1° to higher than 90°) can be prepared from pure isotactic poly(propylene) (iPP) without any further modification with low‐surface‐energy components under ambient atmosphere. The formed surfaces have naturally good thermal properties, chemical and moisture resistance, low density, and potentially low manufacturing cost.

SEM images of formed super‐hydrophobic surfaces and related two extreme sliding angles (contact angles of these surfaces are higher than 150°).     

Stimuli‐responsive antifouling polyisobutylene‐based biomaterials via modular surface functionalization

This article demonstrates a new, modular approach to surface functionalization that harnesses chain entanglement. A layer of functionalized polyisobutylene, (PIB)‐ω, where ω = ‐OH, ‐thymine (T), ‐hexaethylene glycol (HEG), poly(ethylene glycol) (‐PEG‐OH), methoxy‐functionalized poly(ethylene glycol) (‐PEG‐OCH₃), and ‐tetraethylene glycol‐α‐lipoate (TEG‐αL) was adhered to PIB‐based thermoplastic elastomer (TPE) surfaces. X‐ray photoelectron spectroscopy (XPS) at angles ranging from 20° to 75° showed decreasing polar group concentration with increasing penetration depth, confirming segregation of polar groups toward the surface. Water contact angle (WCA) of the PIB‐based TPE dropped from 95° to 79°?83° upon coating, and soaking in water for 24 h further decreased the WCA. Dynamic WCA measurements showed 40–30° receding angles, showing that stimulus from an aqueous environment elicits enrichment of polar groups on the surface. Fibrinogen (Fg) adsorption on the various surfaces was quantified using surface plasmon resonance (SPR). Static and dynamic WCA did not vary significantly among TPE + PIB‐ω surfaces, but there were dramatic differences in Fg adsorption: 256 ng/cm² was measured on the native TPE, which dropped to 40 and 22 ng/cm² on PIB‐PEG‐OCH₃ and PIB‐PEG‐OH‐coated surfaces. PIB‐TEG‐αL‐coated surfaces presented the lowest Fg adsorption with 14 ng/cm². © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1742–1749     

Adsorption of bovine serum albumin at solid/aqueous interfaces

Adsorption of soluble serum proteins on hydrophilic and hydrophobic solid surfaces is important for biomaterials and chromatographic separations of proteins. The adsorption of bovine serum albumin (BSA) from aqueous solutions was studied with in situ ATR-IR spectroscopy, and with ex situ ATR-IR, ellipsometry, and water wettablity measurements. The results were used to quantitatively determine the adsorbed film thickness and surface density of BSA on hydrophilic silicon oxide/silicon surfaces, and on these surfaces covered with a hydrophobic lipid monolayer of dipalmitoylphosphatidylcholine (DPPC). The water contact angles were 5° for silicon oxide, 47° ± 1° for the DDPC monolayer, and 53° ± 1° for the BSA monolayers. At 25 °C, and with 0.01–1 wt% BSA in water, the surface densities range from Γ = 2.6–5.0 mg/m², and the film thicknesses range from d = 2.0–3.8 nm, on the assumption that the film is as dense as bulk protein. These results, and certain changes in the IR amide I and II bands of the protein, indicate that the protein adsorbs as a side-on monolayer, with some flattening due to unfolding or denaturation. The estimated -helical content for protein in buffer solutions is 15% higher than for solutions in water. The adsorption density reaches a steady-state value within 10 min for the lowest concentration, but does not appear to reach a steady-state value after 3 h f‘or the higher concentrations. Adsorption of BSA on a silicon oxide surface covered with a monolayer of DPPC leads to an adsorbed protein film of about half the thickness and surface density than on silicon oxide, but the same contact angle, indicating more protein unfolding on the hydrophobic than on the hydrophilic surface.     

Synthesis of well‐defined star‐shaped poly(ε‐caprolactone)/poly(ethylbene glycol) amphiphilic conetworks by combination of ring opening polymerization and “click” chemistry

Well‐defined star‐shaped hydrophobic poly(ε‐caprolactone) (PCL) and hydrophilic poly(ethylene glycol) (PEG) amphiphilic conetworks (APCNs) have been synthesized via the combination of ring opening polymerization (ROP) and click chemistry. Alkyne‐terminated six arm star‐shaped PCL (6‐s‐PCLx‐C?CH) and azido‐terminated PEG (N₃‐PEG‐N₃) are characterized by ¹H NMR and FT‐IR. The swelling degree of the APCNs is determined both in water and organic solvent. This unique property of the conetworks is dependent on the nanophase separation of hydrophilic and hydrophobic phases. The morphology and thermal behaviors of the APCNs are investigated by SEM and DSC respectively. The biocompatibility is determined by water soluble tetrazolium salt reagents (WST‐1) assay, which shows the new polymer networks had good biocompatibility. Through in vitro release of paclitaxel (PTX) and doxorubicin (DOX), the APCNs is confirmed to be promising drug depot materials for sustained hydrophobic and hydrophilic drugs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 407–417     

Control over wettability of polyethylene glycol surfaces using capillary lithography

We demonstrate that wettability of poly(ethylene glycol) (PEG) surfaces can be controlled using nanostructures with various geometrical features. Capillary lithography was used to fabricate PEG nanostructures using a new ultraviolet (UV) curable mold consisting of functionalized polyurethane with acrylate group (MINS101m, Minuta Tech.). Two distinct wetting states were observed depending of the height of nanostructures. At relatively lower heights (< 300 nm for 150 nm pillars with 500 nm spacing), the initial contact angle of water was less than 80 degrees and the water droplet easily invaded into the surface grooves, leading to a reduced contact angle at equilibrium (Wenzel state). At relatively higher heights (> 400 nm for 150 nm pillars with 500 nm spacing), on the other hand, the nanostructured PEG surface showed hydrophobic nature and no significant change in contact angle was observed with time (Cassie state). The presence of two wetting states was also confirmed by dynamic wetting properties and contact-angle hysteresis. The wetting transition from hydrophilic (bare PEG surface) to hydrophobic (PEG nanostructures) was described by the Cassie-Baxter equation assuming that enhanced hydrophobicity is due to the heterogeneous wetting mediated by an air pocket on the surface. The measured contact angles in the Cassie state were increased with increasing air fraction, in agreement with the theoretical prediction.     

Modification of wetting properties of laser-textured surfaces by depositing triboelectrically charged Teflon particles

Hydrophilic laser-textured silicon wafers with natural oxide surfaces were rendered hydrophobic by depositing electrostatically charged submicrometer Teflon particles, a process termed as triboelectric Teflon adhesion. Silicon surfaces were micro-textured (～5 μm) by laser ablation using a nanosecond pulsed UV laser. By varying laser fluence, micro-texture morphology of the wafers could be reproduced and well controlled. Wetting properties of the triboelectrically charged Teflon-deposited surfaces were studied by measuring apparent static water contact angles and water contact angle hysteresis as a function of substrate roughness and the amount of Teflon deposited. A similar study was also performed on various micro-textured silicon carbide surfaces (sandpapers). If the average substrate roughness is between 15 and 60 μm, superhydrophobic surfaces can be easily formed by Teflon deposition with water contact angle hysteresis less than 8°. This environmentally benign solvent-free process is a highly efficient, rapid, and inexpensive way to render contact-charged rough surfaces hydrophobic or superhydrophobic.     

Tailored surface properties of monodispersed polymer particles with PCL hairy chains synthesized by hydroxyl‐initiated ring‐opening polymerization

Polymeric particles with hydrophobic PCL hairy chains were prepared by ring‐opening polymerization (ROP) from hydrophilic core particles, which were prepared by soap‐free emulsion polymerization of styrene, 2‐hydroxyethyl methacrylate, and divinylbenzene. Due to the incorporation of 2‐hydroxyethyl methacrylate in the core particles, hydroxyl groups on the surface of core particles could be obtained, and in the following ROP of ε‐caprolactone, the hydroxyl groups on the surface of the particles could effectively initiate the polymerization. Various reaction conditions were evaluated to produce hairy particles with optimal grafting efficiency. The presence of hydrophobic polymeric hairs on the surface of particles led to a dramatic improvement in their dispersibility in oil phase. By controlling the grafting amount of PCL on the surface of hydrophilic core particles, the surface properties of the hairy particles could be well tailored, represented the change of water contact angles from 75.0° to 114.6°. The prepared hairy particles were characterized by thermogravimetric analysis, scanning electron microscopy, differential scanning calorimetry, and Fourier transform infrared analysis. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4552–4563, 2007     

Amphiphilic fluorous random copolymer self‐assembly for encapsulation of a fluorinated agrochemical

Amphiphilic self‐folding random copolymers exhibit different solution behaviors depending on the identity of the hydrophobic/hydrophilic units. Herein, it is demonstrated that changing the hydrophilic unit from poly(ethylene glycol) to the sugar trehalose causes increased discrepancy in the polarity difference with a fluorinated hydrophobic segment and changes the aggregation state of the polymer in water. The PEG‐fluorinated and trehalose/PEG‐fluorinated amphiphilic random copolymers were the most efficient at encapsulating a fluorinated agrochemical. The small‐molecule agrochemical exerts a strong influence on the self‐assembly of the polymers, demonstrating that fluorous interactions result in not only intramolecular self‐folding behavior but also intermolecular polymer association to form well‐defined nanoparticles. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 352–359     

Temperature‐Responsive Mixed‐Shell Polymeric Micelles for the Refolding of Thermally Denatured Proteins

We have fabricated a mixed‐shell polymeric micelle (MSPM) that closely mimics the natural molecular chaperone GroEL? GroES complex in terms of structure and functionality. This MSPM, which possesses a shared PLA core and a homogeneously mixed PEG and PNIAPM shell, is constructed through the co‐assembly of block copolymers poly(lactide‐b‐poly(ethylene oxide) (PLA‐b‐PEG) and poly(lactide)‐b‐poly(N‐isopropylacryamide) (PLA‐b‐PNIPAM). Above the lower critical solution temperature (LCST) of PNIPAM, the MSPM evolves into a core–shell–corona micelle (CSCM), as a functional state with hydrophobic PNIPAM domains on its surface. Light scattering (LS), TEM, and fluorescence and circular dichroism (CD) spectroscopy were performed to investigate the working mechanism of the chaperone‐like behavior of this system. Unfolded protein intermediates are captured by the hydrophobic PNIPAM domains of the CSCM, which prevent harmful protein aggregation. During cooling, PNIPAM reverts into its hydrophilic state, thereby inducing the release of the bound unfolded proteins. The refolding process of the released proteins is spontaneously accomplished by the presence of PEG in the mixed shell. Carbonic anhydrase B (CAB) was chosen as a model to investigate the refolding efficiency of the released proteins. In the presence of MSPM, almost 93 % CAB activity was recovered during cooling after complete denaturation at 70 °C. Further results reveal that this MSPM also works with a wide spectrum of proteins with more‐complicated structures, including some multimeric proteins. Given the convenience and generality in preventing the thermal aggregation of proteins, this MSPM‐based chaperone might be useful for preventing the toxic aggregation of misfolded proteins in some diseases.     

Novel combination of hydrophilic/hydrophobic surface for large wettability difference and its application to liquid manipulation

This paper reports a novel combination of hydrophilic/hydrophobic materials for the evolution of liquid manipulation. Droplet generation based on a hydrophilic/hydrophobic mechanism is a promising method for highly accurate liquid manipulations. Although several droplet manipulation devices utilizing hydrophilic/hydrophobic patterns have been reported, it has been difficult to split fluid into droplets solely through hydrophilic/hydrophobic patterns in a microchannel. In this study, a material combination for fabricating hydrophilic/hydrophobic patterns was investigated and their wettability difference was enhanced for droplet generation. To improve hydrophilicity, we attempted to increase the surface area of silicon oxide through pulsed plasma chemical vapor deposition (PPCVD). To improve hydrophobicity, the damage to the hydrophobic patterns in the fabrication process was reduced. We successfully enhanced the difference in contact angles from 54.3° to 86.6° by combining the developed hydrophilic material and hydrophobic material. The developed material combination could successfully split fluid into a quantitative droplet of 14.1 nL in a microfluidic chip. Because the developed hydrophilic/hydrophobic combination enables the formation of a droplet with desirable shape in microchannels, the developed hydrophilic/hydrophobic combination is a promising component for lab-on-a-chip applications.     

Carpetlike dense‐layer formation in a polyelectrolyte brush at the air/water interface

A carpetlike dense‐layer formation between a hydrophobic layer and a polyelectrolyte brush layer has been found in the monolayers of an ionic amphiphilic diblock copolymer, poly(1,1‐diethylsilacyclobutane)_m‐block‐poly(methacrylic acid)_n, on a water surface by an X‐ray reflectivity technique. By detailed analysis, we have found that the hydrophilic layer under the water is not a simple layer but is divided into two layers, that is, a carpetlike dense methacrylic acid (MAA) layer near the hydrophobic layer and a polyelectrolyte brush layer. We have also confirmed that a well‐established polyelectrolyte brush is formed only for the m:n = 43:81 polymer monolayer: For m:n = 40:10 and m:n = 45:60 polymer monolayers, only a dense MAA layer is formed. This dense‐layer formation should be the origin of the interesting hydrophobic‐layer thickness variation previously reported; The hydrophobic‐layer thickness takes a minimum as a function of the hydrophilic chain length at any surface pressure studied. An overview of the data for three samples with different chain lengths (m:n = 40:10, 45:60, or 43:81) has shown that the thickness of this dense layer is 10–20 Å and is independent of the surface pressure and polymerization degree of poly(methacrylic acid) (PMAA) in the range studied. This dense‐layer formation is explained by the reasonable speculation that contact with PMAA is thermodynamically more stable than direct contact with water for the diethylsilacyclobutane (Et₂SB) layer on water. In this sense, the dense layer acts like a carpet for the hydrophobic Et₂SB layer, and a 10–20‐Å thickness could be a critical value for the carpet. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1921–1928, 2003     

Wettability of poly(styrene‐co‐acrylate) ionomers improved by oxygen‐plasma source ion implantation

The surfaces of poly(styrene‐co‐acrylic acid) copolymers and their Na‐ and Cs‐neutralized ionomers were modified by O₂‐plasma source ion implantation (PSII) treatment to improve the surface wettability. The changes in the surface wettability, composition, and structure upon the PSII treatment were examined with contact‐angle measurements and X‐ray photoelectron spectroscopy. The untreated surfaces of the acid copolymers and ionomers exhibited different surface energies; this implied clearly that the type of ion species affects the surface hydrophilicity. Also, the PSII treatment induced oxygen‐containing groups to reside on the surface and ionic groups to come out toward the surface; this made the surfaces of the ionomers more hydrophilic as compared with that of the acid copolymers. The ionomers also showed slow hydrophobic recovery. Thus, it was suggested that the reduced mobility of the polymer chain because of the presence of ionic aggregates results in restricted reorientation of oxygen‐containing groups. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1791–1797, 2003     

Superamphiphilic Silicon Wafer Surfaces and Applications for Uniform Polymer Film Fabrication

Silicon wafers have been widely used in the semiconductor industry for many decades. Over the past decades, with the development of organic optoelectronic materials, silicon-based organic–inorganic hybrid devices have received more and more interest in fundamental and applied research. To obtain uniform organic films for hybrid devices, superamphiphilic surfaces, on which both water and oil can spread completely, show great advantages. Herein, we prepared superamphiphilic silicon wafer surfaces with contact angles (CAs) near 0° for both water and typical organic liquids. Interestingly, lateral force mode (LFM) atomic force microscopy (AFM) images indicate that the superamphiphilicity is induced by alternating hydrophilic and hydrophobic nanodomains. By making use of these superamphiphilic silicon wafer surfaces, uniform polypyrrole (PPy) films were generated in both water and cyclopentanone, providing a versatile and effective way for the integration of organic optoelectronic materials with inorganic microelectronic devices.     

Synthesis of end‐functionalized AB copolymers. II. Synthesis and characterization of carboxyl‐terminated poly(ethylene glycol)–poly(amino acid) block copolymers

AB block copolymers composed of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic poly(amino acid) with a carboxyl group at the end of PEG were synthesized with α‐carboxylic sodium‐ω‐amino‐PEG as a macroinitiator for the ring‐opening polymerization of N‐carboxy anhydride. Characterizations by ¹H NMR, IR, and gel permeation chromatography were carried out to confirm that the diblock copolymers were formed. In aqueous media this copolymer formed self‐associated polymer micelles that have a carboxyl group on the surface. The carboxyl groups located at the outer shell of the polymeric micelle were expected to combine with ligands to target specific cell populations. The diameter of the polymer micelles was in the range of 30–80 nm. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3527–3536, 2004     

Ideal tetrafunctional amphiphilic PEG/PDMS conetworks by a dual‐purpose extender/crosslinker. I. Synthesis

The synthesis of a new type of amphiphilic conetwork (APCN) consisting of well‐defined hydrophilic poly(ethylene glycol) (PEG) and hydrophobic polydimethylsiloxane (PDMS) segments is described. The conetwork is ideal (the lengths of each PEG and PDMS chain segments, respectively, are identical) and tetrafunctional (exactly four chains emanate from each crosslink site). The synthesis of the conetworks was achieved by the use of a novel dual‐purpose extender/crosslinker Y (bis [(dimethylsilyl)oxy]‐[(etoxydimethylsilyl)oxy]phenylsilane, (SiPh(SiH)₂OEt)), in two steps: (1) Synthesis of a new linear random multiblock copolymer (MBC) (AY)_n(BY)_m, where A is the hydrophilic PEG and B is the hydrophobic segment, and (2) Crosslinking the multiblocks by catalytic condensation of the SiOEt groups in the Y units. The extender/crosslinker fulfills two totally different functions: First, it extends two incompatible hydrophilic and hydrophobic prepolymers (PEG and PDMS) to a random MBC, and, subsequently, it cross‐links the multiblocks to the target APCN. The synthesis and characterization of the extender/crosslinker is also presented. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4953–4964, 2005     

Polymer micromixers bonded to thermoplastic films combining soft‐lithography with plasma and aptes treatment processes

Over the past few years, a growing interest on covalent bonding of polydimethylsiloxane (PDMS) microfluidic devices to thermoplastic films has developed due to reduced costs, biocompatibility, and flexibility. The silane reagent, 3‐aminopropyltriethoxysilane (APTES) has been applied to create this bonding. Here, we report on the fabrication of replica PDMS micromixer devices from a silicon mold using soft lithography that is rapid, facile, and cost‐effective to manufacture. After replica molding, the PDMS micromixer devices were bonded to the APTES‐activated thermoplastic films of polyimide, polyethylene terephthalate, and polyethylene naphthalate. Characterization of these thermoplastic surfaces was analyzed by contact angle measurement, surface free energy, and X‐ray photoelectron spectroscopy. To demonstrate the functionality of this technology, we have analyzed the PDMS micromixers by a peel test, nonleakages, and mixing with the injection of inks, a surfactant, and varying pH solutions. To our knowledge, this is the first reported example in literature of the PDMS–APTES–thermoplastic films preparation that integrates a complex micromixer device. Here, we have established that the hydrophobicity of both sealed polymers required alteration in order for dispersion of a polar liquid in the mixing loops. The application of a polar solvent before injection can remedy this ill effect formulating a hydrophilic micromixer. These preliminary results demonstrate the feasibility of the fabrication technology, bonding technique, and application of the micromixer that, once optimized, can eventually integrate more components to formulate a lab‐on‐a‐chip with the fabrication of gold microelectrodes for biological analysis of blood or plasma. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Self‐assembled silane monolayers: an efficient step‐by‐step recipe for high‐quality,low energy surfaces

Organosilane self‐assembled monolayers (SAMs) are commonly used for modifying a wide range of substrates. Depending on the end group, highly hydrophobic or hydrophilic surfaces can be achieved. Silanization bases on the adsorption, self‐assembly and covalent binding of silane molecules onto surfaces and results in a densely packed, SAM. Following wet chemical routines, the quality of the monolayer is often variable and, therefore, unsatisfactory. The process of self‐assembly is not only affected by the chemicals involved and their purity but is also extremely sensitive to ambient parameters such as humidity or temperature and to contaminants. Here, a reliable and efficient wet‐chemical recipe is presented for the preparation of ultra‐smooth, highly ordered alkyl‐terminated silane SAMs on Si wafers. The resulting surfaces are characterized by means of atomic force microscopy, X‐ray reflectometry and contact angle measurements. Copyright © 2015 John Wiley & Sons, Ltd.     

μ‐Phthalocyaninato‐bis(triphenylphosphinoxidnatrium): Synthese und Kristallstruktur

μ‐Phthalocyaninato‐bis({triphenylphosphine oxide}sodium): Synthesis and Crystal Structure Blue μ‐phthalocyaninato‐bis({triphenylphosphine oxide}sodium) ( 1 ) is prepared by heating triphenylphosphine oxide with disodium phthalocyaninate at 160 °C. 1 is centrosymmetric (space group P1). The Na atom is located in a tetragonal pyramid co‐ordinating four isoindole N atoms at a distance varying between 2.409(2) and 2.438(2) Å, and one O atom at 2.198(2) Å. The Na–Na distance is 2.823(5) Å, and the Na–O–P angle is 145.5(1)°.     

Synthesis of poly(p‐phenylenediamine‐ co‐o‐aminophenol)/multi‐walled carbon nanotube composites by emulsion polymerization

Organic–inorganic composites composed of electrically conducting copolymer p‐phenylenediamine‐ co‐o‐aminophenol and carboxylic acid functionalized multi‐walled carbon nanotubes [poly(pPD‐co‐oAP)/c‐MWNTs] were prepared via in situ emulsion pathway using sodium dodecyl sulphate (SDS) as an emulsifier and potassium persulphate as an oxidant. Acid functionalized MWNTs were used as cores in the formation of tubular shells of the composites. TEM and FESEM analysis showed that a tubular layer of coated copolymer film of several nanometer thicknesses is present on the c‐MWNTs surfaces. FT‐IR spectra endorsed the formation of composites. TGA results indicated that the decomposition temperatures of composites were higher than the bare copolymer. UV‐visible absorption spectra of diluted colloidal dispersion of composites were similar to those of the bare copolymer. The composites were also confirmed by XRD and XPS. Room‐temperature conductivity increases with an increasing fraction of c‐MWNTs. Copyright © 2009 John Wiley & Sons, Ltd.