Isoelectric points of plasma‐modified and aged silicon oxynitride surfaces measured using contact angle titrations

Acid‐base properties of metal oxides and polymers can control adhesion properties between materials, electrical properties, the physical structure of the material and gas adsorption behavior. To determine the relationships between surface isoelectric point, chemical composition and aging effects, plasma‐surface treatment of amorphous silicon oxynitride (SiO_xN_y) substrates was explored using Ar, H₂O vapor, and NH₃ inductively coupled rf plasmas. Overall, the Ar plasma treatment resulted in nonpermanent changes to the surface properties, whereas the H₂O and NH₃ plasmas introduced permanent chemical changes to the SiO_xN_y surfaces. In particular, the H₂O plasma treatments resulted in formation of a more ordered SiO₂ surface, whereas the NH₃ plasma created a nitrogen‐rich surface. The trends in isoelectric point and chemical changes upon aging for one month suggest that contact angle and composition are closely related, whereas the relationship between IEP and composition is not as directly correlated. Copyright © 2010 John Wiley & Sons, Ltd.     

Introduction of Primary Amino Groups on Poly(ethylene terephthalate) Surfaces by Ammonia and a Mix of Nitrogen and Hydrogen Plasma

With the aim of introducing primary amino groups on the surface of poly(ethylene terephthalate) (PET), two methods were compared—the use of ammonia or a combination of nitrogen and hydrogen low-pressure microwave plasma. Several plasma parameters were optimized on the reactor to increase the –NH₂ surface density, which was estimated by colorimetric titration and X-ray photoelectron spectroscopy (XPS). These techniques show that whatever the plasma treatment, almost 2 –NH₂/nm2 are incorporated on PET films. Emission spectroscopy highlighted a correlation between the density of primary amino groups and the ratio between an NH peak intensity and an Ar peak intensity (I_NH/I_Ar). Variation in surface hydrophilicity with aging in air after plasma treatment was monitored with contact angle measurements and showed a hydrophobic recovery. This was confirmed by XPS, which suggests also that surfaces treated by NH₃ plasma are more stable than surfaces treated by N₂/H₂.     

Surface characterization of plasma‐modified poly(ethylene terephthalate) film surfaces

Poly(ethylene terephthalate) (PET) film surfaces were modified by argon (Ar), oxygen (O₂), hydrogen (H₂), nitrogen (N₂), and ammonia (NH₃) plasmas, and the plasma‐modified PET surfaces were investigated with scanning probe microscopy, contact‐angle measurements, and X‐ray photoelectron spectroscopy to characterize the surfaces. The exposure of the PET film surfaces to the plasmas led to the etching process on the surfaces and to changes in the topography of the surfaces. The etching rate and surface roughness were closely related to what kind of plasma was used and how high the radio frequency (RF) power was that was input into the plasmas. The etching rate was in the order of O₂ plasma > H₂ plasma > N₂ plasma > Ar plasma > NH₃ plasma, and the surface roughness was in the order of NH₃ plasma > N₂ plasma > H₂ plasma > Ar plasma > O₂ plasma. Heavy etching reactions did not always lead to large increases in the surface roughness. The plasmas also led to changes in the surface properties of the PET surfaces from hydrophobic to hydrophilic; and the contact angle of water on the surfaces decreased. Modification reactions occurring on the PET surfaces depended on what plasma had been used for the modification. The O₂, Ar, H₂, and N₂ plasmas modified mainly CH₂ or phenyl rings rather than ester groups in the PET polymer chains to form C? O groups. On the other hand, the NH₃ plasma modified ester groups to form C? O groups. Aging effects of the plasma‐modified PET film surfaces continued as long as 15 days after the modification was finished. The aging effects were related to the movement of C?O groups in ester residues toward the topmost layer and to the movement of C? O groups away from the topmost layer. Such movement of the C?O groups could occur within at least 3 nm from the surface. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3727–3740, 2004     

Pyrolysis mass spectrometry and gas chromatography of plasma-polymerized benzene and xylene

Pyrolysis mass spectra and gas chromatograms of plasma-polymerized benzene (PPB) and p-xylene (PPX) have been studied. Both polymers gave mass spectra that indicated the presence of disubstitution in an aromatic ring and of product molecules, such as biphenyl and ethylbenzene, trapped in the polymer matrix. The PPB spectrum showed fragments originating from ? C₆H_{4? n} structures and the PPX spectrum fragments originated from ? CH₂C₆H₄CH_{2? n} structures. Both the pyrolysis mass spectrum and chromatogram contained peaks that distinguished PPX from commercial polystyrene samples. A chain mechanism which involves H abstraction reactions under plasma activation is proposed. The highly crosslinked structures of the polymers are attributed to the subsequent addition of free radicals to the double bonds of a fragmented chain formed as a result of the scission of the C? C aromatic bond(s).     

Thianthrene-containing polyimides with monomer formation via nucleophilic aromatic substitution

Thianthrene-2,3,7,8-tetracarboxylic dianhydride was synthesized via nucleophilic aromatic substitution of N-phenyle-4,5-dichlorophthalimide with thiobenzamide, thioacetamide, and sodium sulfide. This monomer was then polymerized with aromatic diamines by the con-ventional low temperature technique in N,N-dimethylacetamide (DMAc) to yield soluble poly(amic acid)s. Polyimides were obtained by thermal cyclization of the poly(amic acid) films. Polymers obtained formed creasable thin films and had excellent thermal stability in air and nitrogen. The bent thianthrene structure limited crystallization and chain packing, as indicated by x-ray analysis. The amorphous thianthrene-containing polyimides were only soluble in H₂SO₄. © 1995 John Wiley & Sons, Inc.     

Synthesis and characterization of polystyrene–poly(ethylene oxide)–heparin block copolymers

A procedure for the preparation of new block copolymers composed of a hydrophobic block of polystyrene, a hydrophilic spacer-block of poly(ethylene oxide) and a bioactive block of heparin was investigated. Polystyrene with one amino group per chain was synthesized by free radical oligomerization of styrene in dimethylformamide, using 2-aminoethanethiol as a chain transfer agent. This amino group was used in the coupling reaction with amino-telechelic poly(ethylene oxide) to produce an AB type diblock copolymer with one amino group per polystyrene (PSt)–poly(ethylene oxide) (PEO) chain. The amino-semitelechelic oligo-styrene was converted into the isocyanate-semitelechelic oligo-styrene using toluene 2,4-diisocyanate and subsequent coupling with H₂N–PEO–NH₂ afforded AB type block copolymers with terminal amino groups. The coupling of PSt–PEO–NH₂ with heparin was performed in a DMF–H₂O mixture, first by activating the heparin carboxylic groups with EDC at pH 5.1–5.2 and subsequently reacting the activated carboxylic groups with the amino groups of the PSt–PEO–NH₂ at pH 7.5. Depending on the molecular weights of the diblock copolymer used 25–29% w/w heparin was incorporated. These polymers will be further evaluated for their blood-compatibility.     

Electroenzymatic Nitrogen Fixation Using a MoFe Protein System Immobilized in an Organic Redox Polymer

We report an organic redox‐polymer‐based electroenzymatic nitrogen fixation system using a metal‐free redox polymer, namely neutral‐red‐modified poly(glycidyl methacrylate‐co‐methylmethacrylate‐co‐poly(ethyleneglycol)methacrylate) with a low redox potential of ?0.58 V vs. SCE. The stable and efficient electric wiring of nitrogenase within the redox polymer matrix enables mediated bioelectrocatalysis of N₃^?, NO₂^? and N₂ to NH₃ catalyzed by the MoFe protein via the polymer‐bound redox moieties distributed in the polymer matrix in the absence of the Fe protein. Bulk bioelectrosynthetic experiments produced 209±30 nmol NH₃ nmol MoFe^?1 h^?1 from N₂ reduction. ¹⁵N₂ labeling experiments and NMR analysis were performed to confirm biosynthetic N₂ reduction to NH₃.     

Study of the end‐group contribution to ToF‐SIMS and G‐SIMS spectra of poly (lactic acid) using deuterium labelling

In this study, polymeric (MW 50 000) and oligomeric (MW 2000) poly (lactic acid) (PLA), both with and without end‐group deuterium exchange, were analysed using static secondary ion mass spectrometry (SSIMS) to investigate the contribution of end‐group‐derived secondary ions to the SSIMS spectra. By monitoring the SSIMS intensities between the non‐deuterated and deuterated PLA, it is evident that the only significant end‐group‐derived secondary ions are [nM + H]⁺ (n > 1) and C₄H₉O₂⁺. The gentle‐SIMS (G‐SIMS) methodology was employed to establish that deuterated fragments were produced through low energy processes and were not the result of substantial rearrangements. It was noted that end‐group‐derived secondary ions had higher G‐SIMS intensities for oligomeric PLA than polymeric PLA, showing that these secondary ions are simple fragment products that are not the result of rearrangement or degraded product ions. Copyright © 2007 John Wiley & Sons, Ltd.     

The Critical Role of Reductive Steps in the Nickel-Catalyzed Hydrogenolysis and Hydrolysis of Aryl Ether C−O Bonds

The hydrogenolysis of the aromatic C−O bond in aryl ethers catalyzed by Ni was studied in decalin and water. Observations of a significant kinetic isotope effect (k_H/k_D=5.7) for the reactions of diphenyl ether under H₂ and D₂ atmosphere and a positive dependence of the rate on H₂ chemical potential in decalin indicate that addition of H to the aromatic ring is involved in the rate-limiting step. All kinetic evidence points to the fact that H addition occurs concerted with C−O bond scission. DFT calculations also suggest a route consistent with these observations involving hydrogen atom addition to the ipso position of the phenyl ring concerted with C−O scission. Hydrogenolysis initiated by H addition in water is more selective (ca. 75 %) than reactions in decalin (ca. 30 %).     

Supersonic Pulse,Plasma Sampling Mass Spectrometry: Theory and Practice

Supersonic pulse, plasma sampling mass spectrometry is described, with an emphasis on the physical mechanism by which species originally within the plasma are incorporated into the supersonically expanding noble gas pulse. This new method is based on the release of a short burst of noble gas into the high vacuum environment of an ECR-microwave plasma. Upon expansion through the plasma region, species originally present in the plasma become incorporated in the noble gas pulse and are detected by quadrupole mass spectrometry. The mechanism of the incorporation process is investigated through measurement of the time-of-flight velocity distributions of both the noble gas and species incorporated into the pulse. Incorporation is shown to be the result of supercooled noble gas clustering around the incorporated species, which act as nucleation sites for the condensation. It is this unique sampling method which makes this technique capable of providing a chemical snapshot of the plasma composition. Practical applications of this technique include the investigation of the composition of diamond deposition plasmas and the etching of silicon with chlorine. The investigations of diamond plasmas include the observation of a plasma that contains at least 40% of the radical species C ₂ H ₃ .     

Main chain scission reaction of poly(methyl methacrylate) caused by two-photon ionization of dopant

The main chain scission reaction of poly(methyl methacrylate) (PMMA) doped with N,N,N,′,N′-tetramethyl-p-phenylenediamine (TMPD) was examined by ESR spectroscopy and GPC measurement, and the scission mechanism was analyzed. The two-photon ionization of TMPD with excimer laser excitation at 77 K produced an ester radical anion of PMMA (PMMA·m?), which becomes the main chain tertiary radical ? CH₂? C˙(CH₃)? CH₂? after the detachment of the ester side group by annealing of the sample at room temperature. The main chain scission radical ˙C(CH₃)(COOCH₃)? (PMMA˙) which was produced by the β-scission from? CH₂? ˙C(CH₃)? CH₂? showed the 13-line ESR spectrum instead of the ordinary 9-line, due to the fast quenching of the sample to 77 K. The change of the molecular weight distribution was measured by GPC after several irradiation-and-annealing operations. The simulation of the GPC curve confirmed that the scission re-action occurs at random in the PMMA chain in the solid and the main chain scission yield from the ester radical anion, [PMMA˙]/[PMMA·m?], is 0.30. © 1995 John Wiley & Sons, Inc.     

Photochemistry of ring-substituted polystyrenes. II. Photolyses of poly(p-fluoro-, p-chloro-, and p-bromostyrene)s

The photodegradation of thin films of p-fluoro (PPFS), p-chloro (PPCS), and p-bromo (PPBS) styrenes brought about by exposure to 254-nm radiation under high vacuum was studied. Mass spectroscopic measurements indicated that hydrogen and hydrogen halides were the only gaseous products because yields of H₂ and HF from poly(p-fluorostyrene) were much smaller than the corresponding yields of chloro- and bromo-substituted polymers. UV and visible spectra of degraded films indicated the presence of unsaturated species, for the initial rates of formation were comparable in PPFS and PS but considerably greater in PPCS and PPBS. Solubility and molecular weight data indicated simultaneous crosslinking and chain scission; both PPCS and PPBS showed an inordinately high susceptibility to crosslinking. These observations can be rationalized in terms of the energetics of abstraction reactions by H and halogen atoms and in terms of scission of the Ph–Br and Ph–Cl bonds which lead to the participation of radicals in the para position in crosslinking. Some qualitative correspondence between the Hammett parameters of the p-substituents and rates of H₂ formation in the substituted polymers was observed. Quantum yields of gaseous product formation and probabilities of crosslinking and chain scission were also determined for the three polymers. Mechanisms of the various reactions are discussed.     

Plasma reactions of methane in nitrogen and nitrogen/oxygen carriers by matrix isolation FTIR spectroscopy

The plasma-induced reactions of traces of methane in nitrogen and nitrogen/oxygen carriers have been investigated by freezing the products onto a 10 K CsI substrate and performing FTIR analysis on the product mixture. Isotopic substitution studies have been used to assist in identification of reaction intermediates and final products. A combination of low (10 mTorr) and high (2 Torr) pressure discharges has also been used to help in the identification of these products. Oxygen concentration was increased in a stepwise fashion to determine its effect on the reaction product distribution. In the present work, methyl radical was the principal product in low-pressure N₂/CH₄ plasmas, and small amounts of HCN and NH₃ were also produced. In the higher-pressure plasmas, HCN and NH₃ were the principal products. As O₂ was added to the plasmas, CO, H₂O, CO₂, N₂O, NO, O₃, HONO, and HNO₃ were produced in approximately the order shown, i.e., CO was formed in good yield at low oxygen partial pressures, but HNO₃ was produced only in slight yield even at the highest oxygen pressures used in this work. These results are discussed in terms of the development of a plasma device having potential application for destruction of environmentally hazardous materials and how trace organic pollutants might react in such a system.     

Cyclopolycondensation. XIII. New synthetic route to fully aromatic poly(heterocyclic imides) with alternating repeating units

Fully aromatic poly(heterocyclic imides) of high molecular weight were prepared by the cyclopolycondensation reactions of aromatic diamines with new monomer adducts prepared by condensing orthodisubstituted aromatic diamines with chloroformyl phthalic anhydrides. The low-temperature solution polymerization techniques yielded tractable poly(amic acid), which was converted to poly(heterocyclic imides) by heat treatment to effect cyclodehydration at 250–400°C under reduced pressure. In this way, the polyaromatic imideheterocycles such as poly(benzoxazinone imides), poly(benzoxazole imides), poly(benzimidazole imides) and poly(benzothiazole imides) were prepared, which have excellent processability and thermal stability both in nitrogen and in air. The poly(amic acids) are soluble in such organic polar solvents as N,N-dimethyl-acetamide, N-methylpyrrolidone, and dimethyl sulfoxide, and the films can be cast from the polymer solution of poly(amic acids) (η_inh = 0.8–1.8). The film is made tough by being heated in nitrogen or under reduced pressure to effect cyclodehydration at 300–400°C. The polymerization was carried out by first isolating the monomer adducts, followed by polymerization with aromatic diamines. On subsequently being heated, the open-chain precursor, poly(amic acid), undergoes cyclodehydration along the polymer chain, giving the thermally stable ordered copolymers of the corresponding heterocyclic imide structure.     

Synthesis of well‐defined,soluble poly(3‐alkyl‐4‐benzamide) by chain‐growth condensation polymerization

Well‐defined poly(3‐alkyl‐4‐benzamide) was synthesized by means of chain‐growth condensation polymerization of phenyl 3‐octyl‐4‐(4‐octyloxybenzyl(OOB)amino)benzoate ( 1c ) from initiator 2 , followed by removal of the OOB groups on amide nitrogen of poly 1c . Polymerization of 1c with phenyl 4‐(trifluoromethyl)benzoate ( 2b ) in the presence of 1,1,1,3,3,3‐hexamethyldisilazide (LiHMDS) and LiCl in THF at ?10 °C gave poly 1c with a narrow molecular weight distribution (M_w/M_n ≤ 1.08) and a well‐defined molecular weight (M_n = 4480–12,700) determined by the feed ratio of monomer to initiator (from 10 to 30). The OOB groups of poly 1c were removed with H₂SO₄ to give the corresponding N‐unsubstituted poly(p‐benzamide) (poly 1c′ ) with low polydispersity. The solublity of poly 1c′ in polar organic solvents was dramatically higher than that of poly(p‐benzamide), demonstrating that introduction of an alkyl group on the aromatic ring is very effective for improving the solubility of poly(p‐benzamide). © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 360–365     

Die Elektronen- und Infrarotspektren von Hydraten und Clathraten des Nickelcyanids

The infrared and diffuse reflectance spectra in the visible and ultraviolet region of the following compounds have been measured: Ni(CN)₂, 2 H₂O, Ni(CN)₂, 1½ H₂O, Ni(CN)₂, NH₃, ¼ H₂O, Ni(CN)₂, NH₃, R (R = C₆H₆, C₆H₅NH₂, C₆H₅OH). The structural units of these compounds are shown to be the square planar [NiC₄] and the pseudo-octahedral [NiN₄L₂]-group (L = H₂O, NH₃) with Ni-C-N-Ni-bridges. Additional water is present as zeolitic water. The magnetic data give a 1:1 relation of the paramagnetic pseudo-octahedral to the diamagnetic square planar co-ordination polyhedra. The nitrogen of the cyanide ion is close to ammonia in the spectrochemical as well as in the nephelauxetic series, the values of Dq and B being ?1000 and ?900 cm^?1 respectively. The absorption bands of the aromatic molecules in the clathrates are shifted towards lower wave numbers compared to the corresponding solution spectra.     

Surface modification of ethylene‐co‐tetrafluoroethylene films by remote plasmas

The surface modifications of ethylene‐co‐tetrafluoroethylene (ETFE) surfaces by six plasmas (direct H₂, Ar, and O₂ plasmas and remote H₂, Ar, and O₂ plasmas) were investigated with two questions in mind: (1) what plasma could effectively modify ETFE surfaces and (2) which of the CF₂? CF₂ and CH₂? CH₂ components in ETFE was selectively modified? The plasma exposure led to a weight loss from the ETFE surfaces and changes in the chemical composition on ETFE surfaces. The weight‐loss rate showed a strong dependence on what plasma was used for the modification. The remote H₂ plasma led to the lowest rate of weight loss in the six plasma exposures, and the direct O₂ plasma led to the highest rate of weight loss. During exposure to the plasmas, defluorination occurred, and two new C_1s components [? CH₂? CHF? CH₂? and ? CH₂? CH(O? R)? CF_x? , and ? CH₂? CHF? CF₂? , ? CH₂? C(O)? CF_x? , and ? CF_x? C(O)? O? ] were formed on the modified ETFE surfaces. Defluorination was strongly influenced by what plasma was used for the modification. The remote H₂ and Ar plasmas showed high defluorinations of 55 and 51%, respectively. The remote O₂ plasma showed a low defluorination of only 25%. Conclusively, the remote H₂ and Ar plasma exposure effectively modified ETFE surfaces. With the exposure of these surfaces to the remote H₂ plasma, the CF₂? CF₂ component was predominantly modified, rather than the CH₂? CH₂ component. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2871–2882, 2002     

Photolysis of poly(p-isopropyl styrene)

The photodegradation of films of poly(p-isopropyl styrene) with 254 nm radiation at 10^?6mbar and 25±1° has been studied. The principal product is hydrogen but smaller quantities of methane and ethane and a trace of propane are also formed, indicating that the p-substituent also undergoes decomposition. Ultraviolet spectra show rapid changes, particularly in the 230–240 nm region, and a long wave absorption system extending into the visible region also appears. Solubility data indicate the simultaneous occurrence of cross-linking and chain scission, rates of both processes being significantly greater than those for poly(styrene); these results are explicable in terms of the inductive (+I) stabilization (due to the p-C₃H₇ group) of radicals formed on chain scission and of the participation of the p-C₃H₇ group in addition reactions. Quantum yields for the evolution of the gaseous products have been estimated.     

Synthesis,Structure and Noncovalent Interactions Palladium（Ⅱ）Complexes with N—Benzoyl—β—phenylalaniate Dianion and Aromatic Diimine

Two palladium(II) complexes, [Pd(bipy)(BzPhe‐N,O)] and [Pd(phen)(BzPhe‐N,O)]·4H₂O were synthesized by reactions between Pd(bipy)Cl₂ and BzPheH₂ (N‐benzoyl‐β‐phenylalanine), Pd(phen) Cl₂ and BzPheH₂ in water at pH‐9, with their structures determined by X‐ray diffraction analysis. The Pd atom is coordinated by two nitrogen atoms of bipy (or phen), the deprotonated amido type nitrogen atom and one of the carboxylic oxygens of BzPhe (BzPhe = N‐benzoyl‐β‐phenylalaninate dianion). In the complex [Pd(phen) (BzFne‐N,O)] · 4H₂O, the side chain of phenylalanine is located above and approximately parallels to the coordination plane. Both the aromatic‐aromatic stacking interaction between the phenyl ring of phenylalanine and phen, and the metal ion‐aromatic interaction between the phenyl ring of phenylalanine and Pd(II) were observed. [Pd(bipy)(BzPhe‐N,O)] has the phenylalanyl side chain oriented outwards from the coordination plane, which is mainly due to the interaction between the carbonyl oxygen atom of the amido group and the phenyl ring of phenylalanine. The reason for the different orientation of phenylalanyl side chain in the complexes was suggested.     

Surface Interactions of Radicals During Plasma Processing of Polymers

Surface interactions of radical species were investigated using the imaging of radicals interacting with surfaces (IRIS) technique during plasma surface modification of polymers. Three plasma systems were investigated by spatially probing the laser induced fluorescence of individual radical species and determining their surface scattering coefficients, S. The behavior of CF₂ moieties on polymer surfaces was studied using the fluorocarbon plasmas C₂F₆ and hexafluoropropylene oxide (HFPO). Three types of surface interactions were observed, surface generation of CF₂ (S > 1), surface loss of CF₂ (S < 1), and unit scattering (S = 1). Surface loss of CF₂ was seen in HFPO plasmas, while CF₂ was generated in C₂F₆ systems. The differences between these systems is believed to be the result of different overall surface interactions, specifically film deposition in the HFPO system and etching in the C₂F₆ system. Using NH₃ plasmas, the surface interactions of NH₂ radicals with polymers was also investigated. Here, NH₂ is generated at the surface of polyethylene and polytetrafluoroethylene substrates, but is consumed on polyimide substrates. Ion effects were also investigated by placing a grounded mesh in the path of the molecular beam to remove charged species.