Correlation of morphology and barrier properties of thin microwave plasma polymer films on metal substrate

The barrier properties of thin model organosilicon plasma polymers layers on iron are characterised by means of electrochemical impedance spectroscopy (EIS). Tailored thin plasma polymers of controlled morphology and chemical composition were deposited from a microwave discharge. By the analysis of the obtained impedance diagrams, the evolution of the water uptake ?, coating resistance and polymer capacitance with immersion time were monitored and the diffusion coefficients of the water through the films were calculated. The impedance data correlated well with the chemical structure and morphology of the plasma polymer films with a thickness of less than 100 nm. The composition of the films were determined by means of infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The morphology of the plasma polymer surface and the interface between the plasma polymer and the metal were characterised using atomic force microscopy (AFM). It could be shown that, at higher pressure, the film roughness increases which is probably due to the adsorption of plasma polymer nanoparticles formed in the plasma bulk and the faster film growth. This leads to voids with a size of a few tens of nanometers at the polymer/metal interface. The film roughness increases from the interface to the outer surface of the film. By lowering the pressure and thereby slowing the deposition rate, the plasma polymers perfectly imitate the substrate topography and lead to an excellent blocking of the metal surface. Moreover, the ratio of siloxane bonds to methyl-silyl groups increases which implies that the crosslink density is higher at lower deposition rate. The EIS data consistently showed higher coating resistance as well as lower interfacial capacitance values and a better stability over time for the film deposited at slower pressure. The diffusion coefficient of water in thin and ultra-thin plasma polymer films could be quantified for the smooth films. The measurements show that the quantitative evaluation of the electrochemical impedance data requires a detailed understanding of the film morphology and chemical composition. In addition, the measured diffusion coefficient of about 1.5×10⁻¹⁴ cm² s⁻¹ shows that plasma polymers can act as corrosion resistant barrier layers at polymer/metal interfaces.     

The synthesis and evaluation of cyclic olefin sulfone copolymers and terpolymers as electron beam resists

Poly(cyclopentene sulfone) (PCPS) and poly(bicycloheptene sulfone) (PBCHS) copolymers have been evaluated as potential positive electron beam resists which have good thermal properties and which show high sensitivity to ionizing radiation. It was found that thin copolymer films could be processed as resists but that films greater than 3000 Å thick cracked in the solvents used to dissolve the radiation-exposed regions. Incorporation of plasticizing additives did not improve the film properties. Films from low molecular weight polymer fractions cracked less in solvents, but higher radiation doses were required to offset the reduced sensitivity. This resulted in the formation of intractable residues in the exposed regions which appear to be crosslinked polymer. Bicycloheptene monomers with specific functional groups did not improve the properties of the copolymer films. Terpolymerization with α-olefins such as butene-1 and cis-2-butene plasticized these films and reduced their tendency to crack in solvents. Poly(cyclopentene sulfone–co–butene-1 sulfone) films were found to have the best properties, and 1.25-μ resist images could be etched in SiO₂ layers at an exposure dose of 4 × 10^?6 C/cm² at 25KV. However, one important limitation of this terpolymer was the low dissolution rate ratio between the exposed and unexposed regions. Since straight-walled relief images are essential to the formation of high-resolution patterns, the usefulness of this terpolymer as an electron beam resist appears to be hindered by the limited choice of good solvents to maximize the dissolution rate ratio. PBCHS block terpolymers containing methyl methacrylate (MMA) or methacrylic acid (MAA) were synthesized to improve the solubility in solvents and to incorporate the properties of methacrylates. PBCHS–MMA films cracked in solvents after irradiation; PBCHS–MAA polymers were too insoluble to form resist films.     

Study on organosilicon positive resist. III. Organosilicon positive excimer laser resist (OSPR-2016)

A new alkali-developable organosilicon positive excimer laser (KrF) resist (OSPR-2016) has been developed for a bilayer resist system. OSPR-2016 is composed of poly(p-hydroxybenzylsilsesquioxane) and methyl cholate-tris (α-diazoacetoacetate). The ratio is 72.5 : 27.5 w/w. A sample of 0.5-μ thick OSPR-2016 resolved 0.35 μ L&S patterns when exposed to a dose of 320 mJ/cm² from an excimer laser projection printer (NA = 0.37).     

Hydrophobic and superhydrophobic surfaces from polyphosphazenes

Hydrophobic polymers play a crucial role in many biomedical and commercial applications. Hydrophobic polyphosphazenes offer opportunities for the tuning of surface properties that are not found for many conventional hydrophobic materials. Thus, changes in the side groups linked to the polyphosphazene skeleton allow the surface character to be changed from highly hydrophilic to hydrophobic. The hydrophobic side groups range from fluoroalkoxy groups to aryloxy and organosilicon units. Moreover, the polymer architectures can be varied from single‐substituent species to mixed substituent polymers or to block or comb copolymer structures. Superhydrophobicity, with contact angles to water as high as 159°, has been achieved by electrospinning a fluoroalkoxy derivative to nanofiber mats. Copyright © 2006 Society of Chemical Industry     

Organosilicon-functionalized polyolefins,a kind of designable and versatile polymer: From preparation to applications

Functionalization of polyolefins has been a challenging but promising issue since their invention, with the promise of retaining inherent properties and overcoming the low reactivity and poor compatibility. Organosilicons are widely used for polymer modification to improve thermal stability, hydrophobicity, compatibility, and permeability. Since the advent of alkoxysilane-grafted polyethylene in 1960s, organosilicon-functionalized polyolefins (Si-PO) have been extensively prepared, investigated, and developed. The structure of Si-PO is designable due to the flexible chemistry of organosilicons; crosslinked, long chain branched, and star-shaped polyolefins are available after the introduction of alkoxysilanes, chlorosilanes, hyrdosilanes, or alkylsilanes into polyolefins, and generally these polymers are more compatible to fillers than commercial polyolefins due to stronger interaction. In addition, functionalization of polyolefins with stable organosilicon components such as polysiloxane and polysilsesquioxane can improve thermostability, hydrophobicity, gas permeability, and aging resistance; such polyolefins are usually grafted or block polymers. In this review, Si-PO is classified according to the functional organosilicon component, namely alkoxysilane, chlorosilane, hydrosilane, alkylsilane, polysiloxane, and polysilsesquioxane; their preparations are discussed minutely and summarized with manifold examples. Silicon-containing structures impart the unique properties of organosilicons to polyolefins; applications of Si-PO as compatibilizers, processing aids, battery separators, and separating membranes have been widely reported and are discussed here.     

Plasma polymerized membranes and gas permeability. II

Thin films were deposited onto porous substrates by plasma polymerization using three kinds of organosilicic compounds, tetramethylsilane (TMS), hexamethyldisiloxane (M₂), and octamethylcyclotetrasiloxane (D₄). Those composite membranes showed different characteristics of gas permeability. When D₄ was plasma-deposited onto a porous substrate, the composites membrane showed the highest oxygen permeability and the lowest oxygen-to-nitrogen permeability ratio. The composite membrane prepared from TMS showed the permeability characteristics opposite to the membrane obtained from D₄. Infrared spectrum of the polymer from D₄ resembles that of dimethylpolysiloxane. The plasma polymers from TMS and M₂ showed different profiles in Si? O absorption bands in the range 1100–1000 cm^-1 or in absorption bands of SiCH₃ groups in the range 850–750 cm^-1 from respective monomers. X-ray photoelectron spectroscopic observation indicated that all the plasma polymers contained more than two species of Si atom with different oxidation states. The greater part of Si atoms in plasma polymers took the same oxidation states in corresponding monomer. The gas permeability characteristics were closely related to the oxidation states of Si atom in the plasma polymers.     

Hybrid phosphazene-organosilicon polymers: II. High-polymer and materials synthesis and properties

Most of the polymers that have been synthesized and studied over the past 50 years are organic macromolecules. However, many advantages exist for the development of polymers with inorganic backbones. The first major class of inorganic backbone polymers to be developed widely were the polytorganosiloxanes] (silicones), and these now are the subject of broad industrial and fundamental interest. Polyphosphazenes are a relatively new class of inorganic backbone polymers which rival many organic systems in their molecular structural diversity and property variations. They constitute only the second group of inorganic-organic polymers to be developed extensively. An emerging field of research involves an attempt to create a new area of polymer science at the interface between these two subjects, by the synthesis of hybrid organophosphazene organosilicon systems. This review is a summary of recent progress in this new field.     

Plasma-deposited polymer films. II. Transmission and scanning electron microscopy

A transmission electron microscopy (TEM) and scanning electron microscopy (SEM) study of plasma-formed polyethylene and polystyrene is reported. A two-phase structure of spheres embedded in a polymer binder is evident, supporting the predictions of earlier low-angle x-ray scattering data taken of these two plasma-deposited polymers.     

The chemical structure and stability of plasma-deposited thin hydrocarbon layers on polyethylene

AbThe surfaces of polyethylene (PE) films were modified by deposition of layers from acetylene/ethylene monomer gases in a low-pressure radio-frequency plasma. The chemical structure of the plasma-deposited layers and their long-term stability were studied by X-ray photoelectron spectroscopy (XPS), attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, and contact angle measurements. These studies have shown that the plasma-deposited layers consist mainly of amorphous, short-chain, functional C_xH_y structures with aryl units. As the reactive radical centers formed during the plasma process are susceptible to further reaction with atmospheric oxygen and water, the chemical stability of these layers was investigated. This stability is ensured over the long-term, although an increase in the number of functional groups is obtained over time. It was demonstrated that the post-reactions reach a state of equilibrium after a few weeks.     

Properties which influence marine fouling resistance in polymers containing silicon and fluorine

Our research strives to understand and construct polymer surfaces with no inherent power to interact with other materials, especially with the biological polymers used by marine organisms to bind themselves to objects in the sea. During the past 15 years we have synthesized polymers, formulated them into coatings, and measured their resistance to marine fouling in both static and dynamic testing. The polymer surface property which has been most frequently correlated with bioadhesion is critical surface tension (γ_c); in fact, a generalized relationship between γ_c and marine fouling has been known for more than twenty years. However, this behavior is also influenced by other bulk and surface properties of the polymer. This paper presents several alternative interpretations of the relationship between γ_c and bioadhesion, and uses these insights to develop requirements for polymers which refuse or resist strong bonds to other materials.     

Adsorption and desorption dynamics of associative polymers onto particulates of titanium dioxide,alumina and quartz

The authors have been investigating the adsorption and desorption dynamics of nonionic water soluble polymers on inorganic particles. The influence of the nature of polymers with and without associating hydrophobic end groups, the nature of adsorbents [TiO₂, Al₂O₃ (neutral, acid and basic), and SiO₂], polymer concentrations, linear velocity of fluids, and mutual diffusion of polymer molecules on the patterns of adsorption and desorption distribution of polymer concentrations are shown. The model polymer is a nonionic polyurethane polymer based on ethylene oxide. The polymer's structure is R-O-(DI-PEO)₆-DI-O-R (R is C₁₆H₃₃, DI is isophorone diisocyanate, and PEO is CARBOWAX^TM with a molecular weight of 8200). The phenomenological models of association and dissociation kinetics of associative polymers are suggested. The half-lives of clusters into adsorption and desorption layers are estimated. It is shown that heats of desorption of associative polymers are dependent essentially on heats of dissociation of clusters.     

Organosilicium-Chemie: Vom Molekül zum Werkstoff

Organosilicon Chemistry: From Molecules to Materials The transition from basic to applied organosilicon chemistry is described for the research fields that are studied by the author's group: silaethene chemistry, organosilicon polymer chemistry with silacycles and the chemistry of higher coordinated silicon species. Early investigations started with the study of the pyrolysis of silacyclobutanes that yielded silaethenes in the gas phase. However, these investigations are tedious and are of little use for a widespread study of silaethene chemistry. Therefore the generation of silaethenes in solution (from vinylchlorosilanes and tert-butyllithium) is the preferred method. Numerous differently substituted silaethenes have been generated in situ and their reactivity, especially in cycloaddition reactions, has been studied. Silaethenes that have two chlorine substituents at the silicon atom (especially Cl₂SiCHCH₂Bu^t) show an unusual cycloaddition reactivity and yield unexpected products with dienes and trienes (e. g. from [2+2] and [6+2] reactions); some of the silenes with donorfunctional groups at the α-C-atom undergo interesting intramolecular rearrangements. The cycloadducts of Si-dichlorofunctional silenes also show rearrangements when thermolyzed (e. g. [2+2] → [4+2] adducts). The reactivity of these silaethenes and their cyclo-adducts is due to the two chlorine atoms at the silicon atom and their influence can be explained by theoretical models. Silacycles synthesized from silaethenes have been incorporated or have been transformed into silicon containing polymers. Model compounds for nucleophilic substitution reactions at silicon centers and for the hydrolysis of chlorosilanes are higher coordinated silicon species up to coordination number „seven”︁. Some structures that describe such reactions have been characterized by X-ray crystallography.     

A surface silylated single-layer resist based on limited gas permeation

A simple alternative was studied for the tri-layer resist system. One single thick layer of resist polymer was surface silylated to obtain a bilevel structure that functioned similarly to the bilayer resist composed of the Si-containing top imaging and the bottom planalizing layers. A resist or matrix polymer layer containing phenolic – OH groups was silylated by exposing it to hexamethyldisilazane vapor, and Si atoms were effectively incorporated in the surface sublayer by limited gas permeation and reaction with the – OH groups. Oxygen RIE durability of the silylated poly(vinyl phenol) or the positive-working commercial EB resist, RE-5000P, was > 10 times as high as that of PVP or RE-5000P before silylation. The surface silylated single-layer (SSS) resist derived from RE-5000P was flood-exposed through a mesh mask to 11.7°C/cm² of 4 KeV electrons, developed with tetramethylammonium hydroxide in aqueous methanol, and plasma-developed in an O₂ RIE chamber to form a positive-tone relief image.     

Recent progress in negative-working photosensitive and thermally stable polymers

The production of semiconductors, especially for semiconductor large-scale integration (LSI), has been definitely supported by photolithographic technologies using photosensitive polymers in the micro-electronic device industry. Among them, photosensitive and thermally-stable polymers (PSTSPs) provide simpler resist system than the conventional one, in which the resist materials stays after forming a pattern and function as thermally resisting insulators in integrated circuits (ICs) and multi-chip packages (MCPs), eliminating the extra process of resist removal. Recently, negative-working chemical amplification photoresists have started to receive much attention as quite simple and direct network formation systems in polymer films. The recent progress in negative-working PSTSPs based on the chemical amplification system is summarized in this review article, which includes low dielectric constant polymers for LSI, high refractive index polymers for microlens materials in complementary metal oxide semiconductor image sensors, novolac resists for indium tin oxide patterning, and poly(3-hexylthiophene) for organic field-effect transistors.     

Affinity Dialysis–A Method of Continuous,Rapid Metal Ion Separation Using Dialysis Membranes and Selective,Water-Soluble Polymers as Extractants

Abstract

A membrane process utilizing dialysis and selective complexation by water-soluble polymers has been developed. This process, termed affinity dialysis, has been shown to selectively extract and concentrate both cations and anions in a manner similar to ion exchange or solvent extraction. The selective removal of calcium from sodium with selectivity of about 30, removal of chromate ion from dilute streams, and separation of transition metal ions such as Cu/Fe and Cu/Zn have all been successfully demonstrated. Effects of different polymers, polymer concentration, temperature, and flow rates have been studied. The effect of increased polymer concentration is to increase product concentration if appropriate changes in feed, polymer solution, and strip flow rates are made. A continuous polymer solution recycle and regeneration system has been constructed and operated with Cu/Zn and chromate/chloride feed streams. Removal of over 95% of the desired ion in one pass and concentration factors of product over effluent in excess of 100 have been achieved at feed flow rates of 24 gal/d. Product concentrations of greater than 3% from as little as 400 ppm feed have been demonstrated in a continuous process. In addition, the degree of polymer loss to the effluent stream has been shown to be less than 0.01%/d for a typical system. Metal removal from typical feeds is about 0.9 g/m² per 1000 ppm metal in the feed. It is expected that this technique may be useful in the separation of organic and biological materials, as well as for ionic species     

Hybrid phosphazene-organosilicon polymers: I. Background, rationale, and small-molecule model compound chemistry

Most of the polymers that have been synthesized and studied over the past 50 years are organic macromolecules. However, many advantages exist for the development of polymers with inorganic backbones. The first major class of inorganic backbone polymers to be developed widely were the poly(organosiloxanes) (silicones), and these now are the subject of broad industrial and fundamental interest. Polyphosphazenes are a relatively new class of inorganic backbone polymers which rival many organic systems in their molecular structural diversity and property variations. They constitute only the second group of inorganic-organic polymers to be developed extensively. An emerging field of research involves an attempt to create a new area of polymer science at the interface between these two subjects, by the synthesis of hybrid organophosphazene organosilicon systems. This review is a summary of recent progress in this new field.High Polymer and Materials Synthesis and Properties: Part II will appear in the next issue of this journal.     

Organosilicon deep UV positive resist consisting of poly(p-disilanylenephenylene)

A new class of positive deep ultravoilet (UV) resists consisting of poly(p-disilanylenephenylene)s was developed, in which a disilanylene unit and a phenylene unit are connected alternatively in the polymer main chain. These resists had very high etching resistance against oxygen plasma. The lithographic applications of a double-layer resist system in which the poly(p-disilanylenephenylene) film was used as the top imaging layer were examined. As a result, very high resolution and high contrast were attained. The double-layer resist technique using organosilicon deep UV positive resist appears very promising for lithographic applications.     

Proton abstraction as a route to electrically conductive polymers

Proton abstraction with a strong base from relatively acidic doubly allylic and/or benzylic methylene moieties spaced along an otherwise all-conjugated polymer chain has been demonstrated as an alternative route to electrically conductive polymers. Poly(p-phenylene pentadienylene) and its model compound 1,5-diphenylpentadiene, have been prepared via a Wittig reaction sequence. Proton abstraction from the methylene moiety of the model compound to form the delocalized carbanion has been achieved through reaction with n-BuLi and has been confirmed by reaction with methyl iodide. Proton abstraction from poly(p-phenylene pentadienylene) oligomers has been achieved by treatment with n-BuLi to yield a blue-black solid. Preliminary results indicate a conductivity of 10⁻¹−10⁰ S cm⁻¹ for a pressed pellet of the blue-black solid.     

Polyhedral Oligomeric Silsesquioxane and Polyorganosilicon Hybrid Materials and Their Usage in the Removal of Methylene Blue Dye

Polyhedral oligomeric silsesquioxane and organosilicon polymers, which are important classes of inorganic–organic hybrid materials, have emerged as effective adsorbents for the removal of contaminants from the wastewater. In this study, two hybrid materials polyhedral oligomeric silsesquioxane (1-(3-(polyhedraloligomericsilsesquioxane)propoxy)ethane-1,2-diol, POSS-diol) and organosilicon polymer (PGPTS) as adsorbents have been synthesized from 3-glycidyloxypropyltrimethoxysilane (GPTS) monomers by using basic catalyst tetrapropylammonium hydroxide (Pr₄NOH(aq)) and acidic catalyst chlorotinbis[trimethylsilyl)]amide (SnCl(HMDS)), respectively. These hybrid materials POSS-diol and PGPTS were characterized by a few instrumental techniques such as NMR, FTIR, GPC, XRD, BET and then used in the removal of methylene blue (MB) dye from aqueous solutions. These hybrid silicon materials showed an exceptionally high degree of adsorption for MB dye compared to GPTS hydrolyzed with HCl(aq) (POSS-epoxide) and inorganic–organic hybrid materials of Al, Ti, and Zr. The reason for this high adsorption capacity of MB has been tried to be determined mechanically and discussed.

     

Evolution of nanoporosity and electrochemical behavior in organosilicon polymer derived carbon hybrids

Nanoporous carbon hybrids with high specific surface area and pore volume have been prepared from inexpensive commercial precursors, such as nanocarbon and organosilicon polymers. The synthesized carbon hybrids were found to possess specific surface area from 916 to 1798 m² g^?1, pore volume in the range of 0.5–1.2 cc g^?1, and micropore volume up to 0.804 cc g^?1. Cyclic voltammetry in aqueous electrolyte indicated ideal supercapacitive behavior for certain samples. Specific capacitance in the range of 176–333 F g^?1for a moderate voltage scan rate of 20 mV s^?1 was observed for the carbon hybrids. The article explores a simple method for the fabrication of novel carbon hybrids with excellent porosity control and pore volume. The process can open new avenues for the fabrication of a series of novel carbon hybrids, where pore dimensions and specific surface area can be engineered with the careful selection of organosilicon polymers and process conditions.