Low-pressure plasma chlorination of styrene-butadiene block copolymer for improved adhesion to polyurethane adhesives

Studies concerning plasma-surface chlorination of a styrene-butadiene block copolymer (SBS), improving its adhesion to polyurethane adhesives (PU), are presented in this paper. The plasma was generated by an RF discharge (13.56 MHz, plate electrode reactor) in CCl₄ under low pressure. The 180°-peel test, contact angle measurements and XPS spectroscopy were utilized to investigate the SBS surface. A drastic increase in the adhesion (the peel strength 5-7 times higher than that for the non-treated surface) was observed after only a few seconds of the plasma treatment. It was shown that CCl, COH and >CO are the most important functional groups formed as a result of the plasma treatment and they play the crucial role in the chemical bonding between the SBS surface and the adhesive. H₂O molecules strongly attached to the SBS surface were also found. It was determined, however, that they reduce the gluing power. A very good correlation between the concentration of the functional groups and the peel strength was established. On the other hand, no correlation between the peel strength and the surface free energy (estimated from the contact angle measurements) was observed. It indicates that the thermodynamic adhesion is unimportant in this case and confirms the dominant role of the chemical adhesion.     

Hierarchical Nanoporous Structures by Self‐Assembled Hybrid Materials Based on Block Copolymers

Hierarchical nanoporous structures are fabricated by adsorption of micelles of diblock copolymer‐templated Au‐nanoparticles onto a hydrophilic solid substrate. Gold nanoparticles are prepared using micelles (19 nm) of polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) as nanoreactors. Deposition of thin films of the micellar solution, modified with a non‐selective solvent (THF), on hydrophilic surfaces leads to the formation of hierarchical nanoporous morphologies. The thin films exhibit two different pore diameters and a total pore density of 15 × 10⁸ holes per cm². The structure was analyzed in terms of topography and chemical composition using AFM, TEM and XPS measurements. The PS‐b‐P4VP template was subsequently removed by oxygen plasma etching, to leave behind metallic nanopores that mimic the original thin film morphology.

     

Are the Interactions between Recombinant Prion Proteins and Polymeric Surfaces Related to the Hydrophilic/Hydrophobic Balance?

New non‐fouling tubes are developed and their influence on the adhesion of neuroproteins is studied. Recombinant prion proteins are considered as a single component representative of hydrophobic proteins. Samples are stored for 24 h at 4 °C in tubes coated with two different coatings: poly(N‐isopropylacrylamide) as a hydrophilic surface and a plasma‐fluorinated coating as a hydrophobic one. The protein adhesion is monitored by ELISA tests, XPS and confocal microscopy. It appears that the highest recovery of recombinant prion protein in the liquid phase is obtained with the hydrophilic surface while the hydrophobic character of the storage tube induces an important amount of biological loss. However, the recovery is not complete even for tubes coated with poly(N‐isopropylacrylamide).

     

Dual Redox and Thermoresponsive Double Hydrophilic Block Copolymers with Tunable Thermoresponsive Properties and Self‐Assembly Behavior

The synthesis, tunable thermoresponsive properties, and self‐assembly of dual redox and thermoresponsive double hydrophilic block copolymers having pendant disulfide linkages (DHBCss) are reported. Well‐defined DHBCss composed of a hydrophilic poly(ethylene oxide) block and a dual thermo‐ and reduction‐responsive random copolymer block containing pendant disulfide linkages are synthesized by atom transfer radical polymerization. Their lower critical solution temperature (LCST) transitions are adjusted through modulating pendant hydrophobic–hydrophilic balance with disulfide–thiol–sulfide chemistry. Further, these DHBCss derivatives are converted to disulfide‐crosslinked nanogels at temperatures above LCST through temperature‐driven self‐assembly and in situ disulfide crosslinking. They exhibit enhanced colloidal stability and further reduction‐responsive degradability, thus demonstrating versatility of dual thermo‐ and reduction‐responsive smart materials.

     

Radiofrequency Plasma Polymers Containing Ionic Phosphonate Groups: Effect of Monomer Structure and Carrier Gas on Properties and Deposition Rate

Radiofrequency (RF) plasma polymers prepared from perfluoroallylphosphonic acid (PAPA) are hydrophilic and have ionic properties. Unfortunately, deposition rates are low. The current study focuses on RF plasma polymers prepared from PAPA and pentafluoroallyldiethylphosphonate (PADP) with and without argon carrier gas. Plasma polymerized PADP films were similar in composition, structure, and properties to plasma polymerized PAPA films, but were deposited at much higher rates. The addition of argon to the PAPA discharges resulted in a decrease in mean deposition rate from 41.7 Å/min to less than 20 Å/min, while the deposition rate of plasma polymerized PADP increased significantly with the addition of argon to the discharge. PADP derived plasma polymer deposition rates ranged from 136 Å/min to 390 Å/min, depending on position in the reactor and presence or absence of argon carrier gas. PAPA-derived plasma polymers exhibited deposition rates and properties that were uniform throughout the reactor, while PADP-derived plasma polymers had maximum deposition under the upstream induction coil and linearly decreasing deposition rate with downstream distance in the reactor. Additionally, the PADP-derived plasma polymers exhibited downstream changes in atomic composition, structure, and physical properties, such as wettability and hardness. These changes were attributed to a getter effect upstream in the reactor in which ablated hydrogen species scavenge etching fluorine species in the plasma phase.     

Hydrophilization of PVC Surfaces by Argon Plasma Immersion Ion Implantation

Commercial polyvinylchloride (PVC) sheets were treated by plasma immersion ion implantation, PIII. Samples were immersed in argon glow discharges and biased with 25 kV negative pulses. Exposure time to the bombardment plasma changed from 900 to 10,800 s. Through contact angle measurements, the effect of the exposure time on the PVC wettability was investigated. Independent of t, all samples presented contact angles, , equal to zero after the treatment. However, in some cases, surface hydrophilization was not stable, as revealed by the temporal evolution of . Samples bombarded for shorter periods recovered partially or totally the hydrophobic character while the one exposed for the longest time stayed highly hydrophilic. These modifications are ascribed to the Cl loss and O incorporation as shown by XPS measurements. Furthermore, the mobility of surface polar groups and the variation in the cross-linking degree can also affect the PVC wettability.     

Microspheres Assembled from Chitosan‐Graft‐Poly(lactic acid) Micelle‐Like Core–Shell Nanospheres for Distinctly Controlled Release of Hydrophobic and Hydrophilic Biomolecules

To simultaneously control inflammation and facilitate dentin regeneration, a copolymeric micelle‐in‐microsphere platform is developed in this study, aiming to simultaneously release a hydrophobic drug to suppress inflammation and a hydrophilic biomolecule to enhance odontogenic differentiation of dental pulp stem cells in a distinctly controlled fashion. A series of chitosan‐graft‐poly(lactic acid) copolymers is synthesized with varying lactic acid and chitosan weight ratios, self‐assembled into nanoscale micelle‐like core–shell structures in an aqueous system, and subsequently crosslinked into microspheres through electrostatic interaction with sodium tripolyphosphate. A hydrophobic biomolecule either coumarin‐6 or fluocinolone acetonide (FA) is encapsulated into the hydrophobic cores of the micelles, while a hydrophilic biomolecule either bovine serum albumin or bone morphogenetic protein 2 (BMP‐2) is entrapped in the hydrophilic shells and the interspaces among the micelles. Both hydrophobic and hydrophilic biomolecules are delivered with distinct and tunable release patterns. Delivery of FA and BMP‐2 simultaneously suppresses inflammation and enhances odontogenesis, resulting in significantly enhanced mineralized tissue regeneration. This result also demonstrates the potential for this novel delivery system to deliver multiple therapeutics and to achieve synergistic effects.

     

Effect of cold atmospheric plasma treatment on hydrophilic properties of fluorosilicone rubber

Vulcanized fluorosilicone rubber for aviation was treated by argon and oxygen cold atmospheric plasma (CAP) in order to modify its hydrophilic properties. The sample's chemical composition was analyzed by X‐ray photoelectron spectroscopy (XPS). The static contact angle, surface free energy, and adhesion strength were used to indicate the hydrophilic properties. Additionally, the surface morphologies of the specimens were observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results showed that the contact angle declined from 101.5° to 22°, and the surface energy rose from 21.3 to 71.2 mJ/m² after they were treated by argon plasma. Alternatively, the water contact angle decreased to 25.5°, and the surface energy increased to 70.6 mJ/m² after they were treated by oxygen plasma. In addition, the SEM and AFM images of the samples illustrate that the treated surface of fluorosilicone rubber becomes rougher than the non‐treated surface. The concentrations of carbon (C) and fluorine (F) elements of the material' surface decreased and the contents of O element greatly enriched after plasma treatment. Additionally, chemical group C―O and C―OH appeared after the treatment. However, the hydrophilic effect of the plasma treatment is aged after the specimens were stored for 8–12 h. Copyright © 2016 John Wiley & Sons, Ltd.     

Multi‐Compartment Unimolecular Micelles from (ABC)n Multi‐Arm Star Triblock Terpolymers

Four linear and four star equimolar terpolymers based on non‐ionic hydrophilic methoxy hexa(ethylene glycol) methacrylate, ionizable hydrophilic 2‐(dimethylamino)ethyl methacrylate and neutral hydrophobic methyl methacrylate were synthesized using group transfer polymerization and investigated in aqueous dilute solutions. It was found that the (ABC)_n multi‐arm star terpolymers formed unimolecular micelles comprising three centrosymmetric compartments. The position of each compartment could be determined by the block sequence (ABC, ACB or BAC) at will. On the other hand, the ABC linear counterparts formed loose associates with very low aggregation numbers. It was shown that the polymer architecture (linear versus star) greatly affected the micellization phenomena of the terpolymers in selective media.

     

Extending the Capabilities of the Thermodynamic Simulation of Thermochemical Processes in Inductively Coupled Plasma Discharge

The capabilities of the equilibrium thermodynamic simulation of thermochemical processes in inductively coupled plasma discharge are considered. Using a quasi-equilibrium model, the formation efficiencies of singly and doubly charged ions of 84 elements are calculated within the temperature range 4000–10000 K with a step of 500 K. The results of the calculations can be used for improving the performance characteristics of semiquantitative analysis in inductively coupled plasma mass spectrometry. The main trends in investigations on further extending the capabilities of thermodynamic simulations in inductively coupled plasma atomic emission and mass spectrometries are outlined.OAO Ekaterinburgskii zavod po obrabotke tsvetnykh metallov     

Fluorescent Vesicles Consisting of Galactose‐based Amphiphilic Copolymers with a π‐Conjugated Sequence Self‐assembled in Water

Fluorescent vesicles considered as a mimic of natural primitive cells are prepared from poly(3‐hexylthiophene)‐block‐poly(3‐O‐methacryloyl‐D‐galactopyranose) P3HT‐b‐PMAGP copolymers. The unique characteristic of such vesicular nanostructures is their architecture, which comprises a hydrophobic π‐conjugated P3HT wall stabilized by a hydrophilic PMAGP interface featuring glucose units. The results of this work offer a very efficient and straightforward method for engineering well‐controlled fluorescent nanoparticles (without the addition of dyes), which provide an excellent support to the study of carbohydrate‐protein interactions.

     

Chemistry and Structure of Diterpene Compounds of the Kaurane Series: VI. Isosteviol Esters

Esterification with alcohols and diols of (4,8,13)-13-methyl-16-oxo-17-norkaurane-18-carboxylic acid chloride prepared by treatment of the acid (isosteviol) with thionyl chloride yields the corresponding esters. The molecular and crystal structures of a series of esters were determined by single crystal X-ray diffraction. The diethylene glycol diester in the crystal has a tweezer structure with an intramolecular cavity. The supramolecular structure of some isosteviol derivatives in the crystal is characterized by alternation of lipophilic and hydrophilic regions.     

Gas-Chromatographic Studies of the Interaction between Water and Methanol Molecules and the Surface of Carbon Materials

The gas-chromatographic method is used to study the interaction of water and methanol molecules with active hydrophilic centres existing at the surface of thermally exfoliated graphite and graphitized thermal carbon black. The concentration of carboxyl and phenol hydroxyl groups at the surface of these sorbents is determined, and heats of adsorption of the studied molecules are shown to be and 28−25 kJ/mol, respectively. It is also shown that adsorption of water at the hydrophilic centres at lowest relative pressure values takes place with formation of clusters consisting of n = 2 water molecules.     

pH/Thermosensitive Hydrogels Formed at Low pH by a PMMA‐PAA‐P2VP‐PAA‐PMMA Pentablock Terpolymer

A poly(methyl methacrylate)‐block‐poly(acrylic acid)‐block‐poly(2‐vinyl pyridine)‐block‐poly(acrylic acid)‐block‐poly(methyl methacrylate) (PMMA‐PAA‐P2VP‐PAA‐PMMA), pentablock terpolymer has been synthesized by anionic polymerization with sequential addition of monomers and studied in aqueous media at low pH. The system exhibits combined properties and adopts the behavior of ‘telechelic’ polyelectrolytes and that of double hydrophilic polyampholytes. This complex behavior leads to the pentablock terpolymer forming a pH and temperature sensitive reversible hydrogel at very low polymer concentration.

     

Hydrophilic Conjugated Polymers with Large Bandgaps and Deep‐Lying HOMO Levels as an Efficient Cathode Interlayer in Inverted Polymer Solar Cells

Two hydrophilic conjugated polymers, PmP‐NOH and PmP36F‐NOH, with polar diethanol­amine on the side chains and main chain structures of poly(meta‐phenylene) and poly(meta‐phenylene‐alt‐3,6‐fluorene), respectively, are successfully synthesized. The films of PmP‐NOH and PmP36F‐NOH show absorption edges at 340 and 343 nm, respectively. The calculated optical bandgaps of the two polymers are 3.65 and 3.62 eV, respectively, the largest ones so far reported for hydrophilic conjugated polymers. PmP‐NOH and PmP36F‐NOH also possess deep‐lying highest occupied molecular orbital levels of −6.19 and −6.15 eV, respectively. Inserting PmP‐NOH and PmP36F‐NOH as a cathode interlayer in inverted polymer solar cells with a PTB7/PC₇₁BM blend as the active layer, high power conversion efficiencies of 8.58% and 8.33%, respectively, are achieved, demonstrating that the two hydrophilic polymers are excellent interlayers for efficient inverted polymer solar cells.

     

Fine Tuning of Vesicle Assembly and Properties Using Dual Hydrophilic Triblock Copolypeptides

The design, synthesis, and self‐assembly of the first dual hydrophilic triblock copolypeptide vesicles, ${\rm R}_{m}^{{\rm H}} {\rm E}_{n} {\rm L}_{o} $ and ${\rm K}_{m}^{{\rm P}} {\rm R}_{n}^{{\rm H}} {\rm L}_{o} $ , is reported. Variation of the two distinct hydrophilic domains is used to tune cellular interactions without disrupting the self‐assembled structure. The aqueous self‐assemblies of these triblock copolypeptides in water are characterized using microscopy and DLS. Cell culture studies are used to evaluate cytotoxicity as well as intracellular uptake of the vesicles. The ability of polypeptides to incorporate ordered chain conformations that direct self‐assembly, combined with the facile preparation of functional, multiblock copolypeptide sequences of defined lengths, allow the design of vesicles attractive for development as drug carriers.

     

Identification and Quantitation of Malonic Acid Biomarkers of In-Born Error Metabolism by Targeted Metabolomics

Malonic acid (MA), methylmalonic acid (MMA), and ethylmalonic acid (EMA) metabolites are implicated in various non-cancer disorders that are associated with inborn-error metabolism. In this study, we have slightly modified the published 3-nitrophenylhydrazine (3NPH) derivatization method and applied it to derivatize MA, MMA, and EMA to their hydrazone derivatives, which were amenable for liquid chromatography- mass spectrometry (LC-MS) quantitation. 3NPH was used to derivatize MA, MMA, and EMA, and multiple reaction monitoring (MRM) transitions of the corresponding derivatives were determined by product-ion experiments. Data normalization and absolute quantitation were achieved by using 3NPH derivatized isotopic labeled compounds ¹³C₂-MA, MMA-D₃, and EMA-D₃. The detection limits were found to be at nanomolar concentrations and a good linearity was achieved from nanomolar to millimolar concentrations. As a proof of concept study, we have investigated the levels of malonic acids in mouse plasma with malonyl-CoA decarboxylase deficiency (MCD-D), and we have successfully applied 3NPH method to identify and quantitate all three malonic acids in wild type (WT) and MCD-D plasma with high accuracy. The results of this method were compared with that of underivatized malonic acid standards experiments that were performed using hydrophilic interaction liquid chromatography (HILIC)-MRM. Compared with HILIC method, 3NPH derivatization strategy was found to be very efficient to identify these molecules as it greatly improved the sensitivity, quantitation accuracy, as well as peak shape and resolution. Furthermore, there was no matrix effect in LC-MS analysis and the derivatized metabolites were found to be very stable for longer time.

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Graphical Abstract ?

     

A two‐stage surface treatment for the long‐term stability of hydrophilic SU‐8

The use of SU‐8 photoresist as a structuring material for portable capillary‐flow cytometry devices has been restricted by the near‐hydrophobic nature of the SU‐8 surface. In this work, we evaluate the use of chemical and plasma treatments to render the SU‐8 surface hydrophilic and characterise the resulting surface utilising a combination of techniques including contact angle goniometry, atomic force microscopy and X‐ray photoelectron spectroscopy. In particular, for low‐power plasma treatments, we find that the chemistry of the plasma used to modify the SU‐8 surface and the incorporation of O₂ on that modified surface are paramount for improved surface wettability, whilst plasma‐induced surface roughness is not a necessary requirement. We demonstrate a technique to obtain a hydrophilic SU‐8 surface with contact angle as low as 7° whilst controlling and significantly reducing the level of surface roughness generated via the applied plasma. An additional chemical treatment step is found to be essential to stabilise the activated SU‐8 surface, and incubation of the samples with ethanolamine is demonstrated as an effective second‐stage treatment. Application of the optimised two‐stage surface treatment to cross‐linked SU‐8 is shown to result in a smooth hydrophilic surface that remains stable for over 3 months. Copyright © 2015 The Authors Surface and Interface Analysis Published by John Wiley & Sons Ltd.     

Excitation Frequency Dependence of the Surface Properties and Composition of Plasma Polymers from Aldehyde Monomers

The effect was investigated of varying the plasma excitation frequency in the range 125 to 375 kHz upon the air/water contact angles of plasma polymers prepared from the monomers ethylbutyraldehyde (EBA), acetaldehyde (AA), capronaldehyde (CA), and nonyl aldehyde (NA). The surfaces of EBA, CA, and AA plasma films were more hydrophilic when deposited at lower excitation frequencies whereas little frequency dependence was observed in the case of NA plasma polymers. Lower contact angles correlated with increased amounts of C=O and O–C=O groups measured by FTIR and XPS analyses. The effects of storage (aging) in air at room temperature upon the properties of the plasma polymers were also studied. Contact angles of EBA plasma polymers decreased during aging. The contact angles of NA plasma polymers were stable over a 3 months storage period. In the case of CA plasma polymers, the contact angles decreased on aging for films deposited at higher frequencies, whereas CA films deposited at lower frequencies showed increasing contact angles on storage. This aging behavior is interpreted as a result of competition between post-deposition oxidative reactions with atmospheric oxygen and reorientation of polar polymer segments away from the air interface.     

Study of Cryostructuring of Polymer Systems: 22. Composite Poly(vinyl alcohol) Cryogels Filled with Dispersed Particles of Various Degrees of Hydrophilicity/Hydrophobicity

Composite poly(vinyl alcohol) cryogels formed by the freezing–thawing of aqueous concentrated polymer solutions containing suspended filler were prepared and studied. The particles of unmodified silica gels were used as solid hydrophilic fillers and silica gels with grafted C2, C8, and C18 alkyl groups, as hydrophobic fillers. The granules of cross-linked dextran gel (Sephadex) swollen in water were used as soft hydrophilic fillers and lipophilic Sephadexes modified with propylene oxide groups, as soft hydrophobic fillers. It was shown that the microstructure and mechanical properties of such composites are affected by the presence of hydrophobic dispersed phase, namely, as the hydrophobicity of dispersed particles rises, the rigidity of composites increases with filler concentration at progressively lesser extent.