Hydroxy Styrene Research Articles

Exploration of coating alternatives for the protection of bare steel and brass in scientific-technical artefacts

The development of new alternatives for the protection of metallic heritage aims to improve the performance of the coatings used in recent decades. For this purpose, the performance of three novel or poorly explored coatings in this field of study has been evaluated: Owatrol Oil, TiO2-modified Paraloid B-72 and a hybrid of poly(2-ethyl-2-oxazoline), PEOX and poly(4-hydroxy styrene), PHS as a self-healing coating. These have been compared with coatings widely used in conservation such as: Paraloid B-72, Incralac and microcrystalline wax C80. The coatings were evaluated after accelerated ageing in terms of aesthetic changes (visual observation under stereomicroscope and colour measurements), protective ability (electrochemical impedance spectroscopy) and chemical stability (FTIR). After 500 h of exposure to Xenon-arc lamp, it was observed how the addition of TiO2 to Paraloid B-72 partially reduces photo-oxidation of the polymer, but at the same time harms the protective ability due to the appearance of defects. The self-healing coating is quite stable and can also regenerates superficial scratches of about 100 µm if subjected to 90% RH. On the other side, Owatrol demonstrated a very poor performance. These advantages and disadvantages in their use have been compared with those of B-72, Incralac and C80 microcrystalline wax, identifying in which cases their application for protection on scientific-technical artefacts may be feasible.

Determination of effective attenuation length of slow electrons in polymer films

Slow electrons (with energy below 10 eV) play an important role in nature and technology. For instance, they are believed to initiate solubility change in extreme ultraviolet resists. Depending on their mobility, such secondary electrons can lead to image blur and degradation of patterning resolution. Hence, it is important to characterize the transport of slow electrons by measuring parameters such as the effective attenuation length (EAL). We present a technique that allows for prompt characterization of EAL in polymer films. In this experiment, slow electrons are generated in a substrate upon absorption of x-ray photons. The attenuation of electron flux by a polymer film is measured as a function of film thickness, allowing for the determination of EAL for slow electrons. We illustrate this method with poly(hydroxy styrene) and poly(methyl metacrylate) films. Furthermore, we propose an improvement for this technique that would enable the measurement of EAL as a function of electron kinetic energy.

Synthesis of 4-acetoxystyrene – t-butyl acrylate statistical, block and gradient copolymers, and the effect of the structure of copolymers on their properties

The properties of copolymers are affected greatly by the composition as well as the chain structure of the copolymers. Consequently, gradient copolymers, due to the uniqueness of their structures show significantly different properties than those of the conventional statistical and block copolymers. This study reports the synthesis of 4-acetoxystyrene – t-butyl acrylate (AOST-tBA) statistical copolymers by reversible addition-fragmentation chain-transfer (RAFT) and free radical polymerization (FRP) methods, and also the synthesis of block and gradient copolymers of AOST-tBA by the RAFT method. The gradient structure in the AOST-tBA copolymer was produced by continuously adding a second monomer to the polymerization system to taper the copolymer composition. Differential scanning calorimetry (DSC) analysis found a broad transition for the gradient copolymer, in contrast to a single narrow transition for the statistical copolymer and two narrow transitions for the block copolymer. The acetoxy groups from the AOST-tBA copolymers were de-acetylated to convert the AOST to hydroxystyrene (HOST). Fourier transform infra-red (FTIR) studies revealed that the extent of hydrogen bonding in thin films of the HOST-tBA copolymers is greatly influenced by the copolymer composition as well as the chain structure. However, no significant differences were found for the surface compositions and surface free energies of copolymers. The properties of HOST-tBA copolymers synthesized by RAFT and FRP have also been compared in this study.

A fabrication process of flexible IDE capacitive chemical sensors using a two step lift-off method based on PVA patterning

A versatile, two-step, lift-off method, for the fabrication of flexible capacitive chemical sensors based on interdigitated electrodes (IDEs) is presented. A Polyimide (PI) foil whose one side is coated with a thin Aluminum (Al) film is used as the sensor substrate. The IDEs are then formed on the Al film using conventional semiconductor processes. Precise patterning of the sensor sensing layer, on the surface of the Al IDEs, is achieved using a two-step lift-off process which involves a first lift-off during which a Polyvinyl alcohol (PVA) film is spin-coated and patterned, followed by the deposition or spin coating of the sensing layer and a second lift-off to pattern it on the IDEs area and form the final sensor. The process allows for upscaling when a single sensing layer is deposited and patterned in batch over the whole wafer or for the easy fabrication of chemical sensor arrays when depositing and precisely patterning different sensing layers on an array of IDEs. Showcasing the first approach, PHITA copolymer (a methacrylate tertrapolymer) is deposited and patterned over sensors with varying electrode gaps in order to fabricate simple humidity sensors, while in a following experiment, Poly(2-hydroxyethyl methacrylate) (PHEMA), Epoxy novolac resin (EPN), Poly(methyl methacrylate) (PMMA) and Poly(hydroxy styrene) PHS are patterned on the IDEs in order to form a sensor array. The different sensor configurations realized are evaluated when exposed to water, methanol and ethanol vapors with PHS sensor exhibiting a capacitance change of 44 fF (sensitivity: 1.87 fF / %RH), 7.4 fF and 4.6 fF at 10,000 ppm respectively.

유연한 디스플레이 소자의 보호막용 직접 패턴 형성이 가능한 POSS계 저유전 물질의 제조

The passivation layer, which is located between a pixel electrode and a data elec- trode, must provide sufficiently low parasitic capacitance and sufficient electrical insulation to reduce cross talk and signal distortion. The present demand for passivation materials for next-generation displays has created interest in substitutes with low dielectric constant, high transmittance, thermal stability, and patternability; these requirements cannot be met by the silicon nitride layer and silicon dioxide used currently. To meet these requirements, negative-tone patterning systems containing polyhedral oligomeric silsesquioxane (POSS) were developed by adopting two different approaches: use of POSS in the polymeric matrix and in the crosslinker. The polymeric matrix, poly(methacryl isobutyl POSS-r- hydroxy styrene), showed improved dielectric property and thermal stability. However, the POSS content was limited owing to poor solubility. A POSS crosslinker with epoxy func- tional groups was used along with phenol group containing polymeric matrices; poly(4- hydroxy styrene). It was possible to pattern the POSS crosslinker system by irradiating it with UV light and subjecting it to subsequent thermal treatment. With increasing POSS content, the crosslinked materials showed increased transparency, higher thermal stability, and lower dielectric constant. The system could also be patterned by irradiating it with UV through a patterned mask.

Evaluation of enthalpy of mixing by calorimetric method: effect of hydrogen bonding in poly(4-hydroxy styrene)-based blends

To verify the effect of hydrogen bonding on the polymer mixing, blends of poly(vinyl methyl ether) (PVME) and poly(methyl methacrylate) (PMMA) with poly(4-hydroxy styrene) (PHS), respectively, have been prepared. The effect of hydrogen bond strength on the enthalpy of mixing, ΔHM, was investigated by microcalorimetric measurements and FTIR spectroscopy. Infrared analysis allowed to measure the amount of hydrogen bonding by a curve fitting procedure in PHS/PMMA blends, looking to the change in the characteristic bands of carbonyl group of PMMA. In the case of PHS/PMVE, the hydroxyl-stretching region has been investigated to have only a qualitative estimation of hydrogen bonding. For both PHS/PMVE and PHS/PMMA systems, the measured exothermic (negative) ΔHM decreases with the increase in the PHS content, indicating that the presence of strong specific intermolecular interactions, such as hydrogen bonding, favours the polymer blending.

Self-assembly of an interacting binary blend of diblock copolymers in thin films: a potential route to porous materials with reactive nanochannel chemistry.

Self-assembly of a binary mixture of poly(styrene)336-block-poly(4-vinyl pyridine)25 (PS336-b-P4VP25) and poly(ethylene glycol)113-block-poly(4-hydroxy styrene)25 (PEG113-b-P4HS25) is shown to give rise to a cylindrical morphology in thin films through pyridine/phenol-based hetero-complementary hydrogen bonding interactions between the P4VP and P4HS copolymer segments. Removal of the cylindrical phase (PEG-b-P4HS) allowed access to porous materials having a pore surface decorated with P4VP polymer blocks. These segments could be transformed into cationic polyelectrolytes through quaternization of the pyridine nitrogen atom. The resulting positively charged nanopore surface could recognize negatively charged gold nanoparticles through electrostatic interactions. This work, therefore, outlines the utility of the supramolecular AB/CD type of block copolymer towards preparation of ordered porous thin films carrying a chemically defined channel surface with a large number of reactive sites.

Synthesis and Biocide Activity of Polymers Based on Poly(hydroxy styrene) and Poly(hydroxy styrene-co-2-hydroxyethyl methacrylate)

In the present work new biocidal polymers were synthesized based on linear poly(hydroxy styrene) and poly(hydroxy styrene co-2-hydroxyethyl methacrylate). The polymer and the copolymer were modified by chloroacetylation with chloroacetyl chloride and were further modified by quaternization with triethylamine, triphenylphosphine, and tributylphosphine. The mod- ified polymers, and copolymers were characterized by elemental analyses, IR, and 1 H-NMR. The biocidal activities of the compounds were evaluated against E. coli, Staph. aureus, P. aeruginosa, Serratia sp, Kelbsiella sp. and C. albicans. The modi- fied polymers and copolymers had biocidal activity. The toxicity analysis of the most active polymers or co-polymers to Artemia salina was also determined. It differed according to the polymer or co-polymer and its concentration.

Synthesis and Characterization of High-Throughput Nanofabricated Poly(4-Hydroxy Styrene) Membranes for In Vitro Models of Barrier Tissue

Commercially available permeable supports with microporous membranes have led to significant improvements in the culture of polarized cells because they permit them to feed basolaterally and thus carry out metabolism in a more in vivo-like setting. The porous nature of these membranes enables permeability measurements of drugs or biomolecules across the cellular barrier. However, current porous membranes have a high flow resistance due to great thickness (20-40 μm), low porosity, and a wide pore size distribution with tortuous diffusion paths, which make them low-throughput for permeability studies. Here we describe an alternate platform that is more flexible, allows for more control over physical parameters of the membranes, and is high-throughput. This study reports on the synthesis, nanofabrication, and surface characterization of a 3-μm-thick transparent membrane based on poly(4-hydroxy styrene) (PHOST). The membranes are nanofabricated using electron beam lithography and deep ion plasma etching to achieve an organized array of straight pores from 50 to 800 nm in diameter, with at least 23 times less flow resistance. It also shows for the first time the potential utility of PHOST as a cell culture substrate without cytotoxicity, and suitability for nanofabrication processes due to temperature stability.

Controlled Synthesis of Linear Polymers with Highly Branched Side Chains by "Hypergrafting": Poly(4-hydroxy styrene)-graft-hyperbranched Polyglycerol.

Linear polymers with hyperbranched side chains are unusual macromolecular structures due to their high number of functional groups in the side chains as well as their potential cylindrical conformation in bulk or solution. In a three-step synthesis combining anionic and oxy-anionic polymerization, hyperbranched polyglycerol was "hypergrafted" from linear poly(4-hydroxy styrene) macroinitiators to yield poly(4-hydroxy styrene)-graft-hyperbranched polyglycerol. Successful grafting with control over molecular weight (10-31 kg·mol-1) and low PDIs (<1.4) was shown by various characterization techniques. All polymers have a high side chain density, due to rapid transfer of the initiating functional groups to the linear backbone. DSC studies give insight into the thermal properties of the resulting polymers.

Sputter deposited carbon tested as RIE intermediate for HSQ and its CMP reversed patterns

Sputter deposited carbon has been tested as Reactive Ion Etching (RIE) intermediate, i.e. as second layer in a bi-layer resist system. E-beam written Hydrogen Silsesquioxane (HSQ) patterns or their reversed complementary (silicon) patterns (obtained by Chemical Mechanical Polishing (CMP)) were used as top layer. Using oxygen RIE, features smaller than 50 nm wide have been transferred into the sputtered carbon in both the forwarded and the reversed tone. After oxygen RIE of the reversed bi-layer, however, extensive surface roughness is observed. Auger spectra of our sputtered carbon show predominantly sp 2 bonds, indicating that the sputter deposited material is comparable to the glassy carbon which has been used as sputter target. The etch resistance of this sputtered carbon in many standard etch recipes outperforms Novolak and Poly Hydroxy Styrene (PHS) based resists. The etch rates can be correlated to the normalized average amount of (nearest neighbour) carbon to carbon atom bonds for a carbon atom in the resist, the carbon–carbon neighbour ratio parameter C 2NR.

Effect of water in ambient air on hysteresis in pentacene field-effect transistors containing gate dielectrics coated with polymers with different functional groups

We investigated the effect of water in ambient air on the hysteresis phenomena of pentacene field-effect transistors with polymer/SiO 2 gate dielectrics. The polarity of the polymer surface was controlled by using three different polymers: poly(styrene), poly(4-hydroxy styrene), and poly(4-vinyl pyridine). Water diffusion into the interface between the pentacene and the gate dielectric was driven by the polarity of the polymer surface, resulting in considerable hysteresis and degradation of device performances. The observed hysteresis behaviors can be explained in terms of donor- and acceptor-like trap formation by water molecules that have diffused between the pentacene and the gate dielectric. The different effects of these traps on hysteresis depending on the functional groups at the polymer surface were also investigated.

Fluorine-contained photoacid generators (PAGs) and corresponding polymer resists

A new series of fluorinated anionic photoacid generators (PAGs) (F4-MBS-TPS, F4VBzBS-TPS, F4-IBBS-TPS, CF3 MBS-TPS, MTFBS-TPS and VBzTFBS-TPS), and corresponding PAG bound polymeric resists (HS-EA-PAG) based on hydroxystyrene (HOST) and 2-ethyl-2-adamantyl methacrylate (EA), (GB-EA-PAG) based on γ-butyrolactone methacrylate (GBLMA) and 2-ethyl-2-adamantyl methacrylate (EA) were prepared and characterized. The acid generating efficiency of PAG bound polymers (HS-EA-PAG) series was in the range of 54–81%, which agrees well with the electron withdrawing effect of the substituents. With regard to the referenced F4-PAG bound polymer with 68% acid generating efficiency, and our previously reported EUVL results of F4-MBS-TPS bound polymer photoresists, these new PAG bound polymers should be effective resists for 193 nm or EUV lithography.

Fullerene Grafted Photoacid Generator (PAG) Bound Polymer Resists

Two polymeric fullerene derivatives and corresponding fullerene grafted, PAG bound polymer resists (HS-EM-HM/Fulle-PAG) based on hydroxystyrene (HS), 2-ethyl-2-adamantyl methacrylate (EM), 3-hydroxy-1-admantyl methacrylate (HM) were prepared and characterized. The preliminary lithographic performance of these polymers were conducted with a contact printer, e-beam, and structure-function relationships were also studied. The results demonstrated that the thermostability and glass transition temperatures increased, but sensitivity and resolution decreased. Further investigations about microstructure modification, composition effect, exposure conditions on the lithographic properties will be carried out.

An Efficient Route to Mesoporous Silica Films with Perpendicular Nanochannels

Mesoporous silica films with cylindrical pores oriented normal to the substrate are prepared by selective deposition of silica within the poly(hydroxy styrene) domains of poly(α-methyl styrene-b- hydroxy styrene) template films using supercritical carbon dioxide as a delivery medium. Atomic force microscopy, electron microscopy, and grazing incidence small angle X-ray scattering (see figure) studies confirm the vertical alignment of the cylindrical pores.

New Anionic Photoacid Generator Bound Polymer Resists for EUV Lithography

A new series of functionalized anionic photoacid generators (PAGs) [methacrylate substituted benzene sulfonic PAGs (such as, NO2 PAG, CF3 PAG, and F4 FAG as reference)] and perfluoro alkanesulfonic PAG (MTFB PAG), as well as corresponding PAG bound polymeric resists (HS-EA-PAG) based on hydroxystyrene (HS) and 2-ethyl-2-adamantyl methacrylate (EA), were prepared and characterized. The acid generating efficiency of PAG bound polymers was in the range of 54−81%, which agrees well with the electron withdrawing effect of the substituents. With regard to the referenced F4 PAG bound polymer with 68% acid generating efficiency and our previously reported EUVL results of F4 PAG bound polymer photoresists, these new PAG bound polymers should be effective resists for EUV lithography.

Equilibrium and dynamics of Langmuir monolayers when the interface is a selective solvent: Polystyrene-b-poly(t-butyl acrylate) block copolymers

The surface pressure of monolayers of insoluble diblock copolymers has been measured. One of the blocks is made of poly(t-butyl acrylate) (PtBA), and the other one by polystyrene (PS). The interface is a good solvent for PtBA, while it is a poor solvent for PS. For the sake of comparison, monolayers of a PtBA homopolymer (good solvent conditions) and of poly(4-hydroxy styrene) (P4HS) (poor solvent conditions) have been also measured. It has been found that the relative length of the blocks plays an important role on the shape of the surface pressure Pi versus surface concentration Gamma curves and also on the shape of the equilibrium compressibility versus Gamma curves. However, it does not affect the maximum value of Pi reached at high Gamma's. Surprisingly, the ellipsometric thickness of the copolymer monolayers is almost independent of the relative length of the blocks. The dynamics of the monolayers has been studied by step compression and by surface-light scattering techniques. When M(w,PtBA) >> M(w,PS) single exponential relaxations are observed. However, stretched exponentials are obtained for M(w,PS) > or = M(w,PtBA). The relaxation times decrease with increasing Gamma for all the copolymers studied. This is the behavior usually found for poor solvent conditions (P4HS) and opposite to that found for homopolymers under good solvent conditions [PtBA, poly(vinylacetate)]. This means that the solvent quality of the interface does not determine the pressure dependence of tau. The elasticity modulus of the monolayers in the kilohertz range takes values that are similar to those of the high-frequency limit of the relaxation experiments. This means that the relaxation processes have characteristic frequencies below 1 Hz.

New Pathways for Modifying the Surface of High Density Polyethylene: Chemically Benign Adhesion Promotion and Subsequent Reactivity

The surface of high density polyethylene (HDPE) was modified using a two-step chemical process. HDPE panels were initially immersed in a heated, aqueous hypochlorite solution containing a carboxylic acid promoter and quenched with deionized water at room temperature following a heterogeneous chemical reaction process patented by Beholz (U.S. Patents 6,077,913 and 6,100,343). 1-5 mole percent chlorine heteroatoms were identified on the resulting HDPE surface using ESCA techniques. The surface chlorine concentration was optimized as a function of reaction time, reaction stoichiometry and number of repeated chemical treatments. The chlorinated HDPE surface was subsequently exposed to ultra-violet (UV) light and surface alkene moieties were noted using ATR FT-IR methods along with a concomitant reduction in surface chlorine from ESCA measurements. The photochemically induced free radical surface dehydrochlorination mechanism was observed to follow first-order kinetics and potentially produce a focussed pattern for information storage. Facile subsequent reactivity of the isolated surface alkene groups was demonstrated using electrophilic addition of Br2. Furthermore, poly(4-hydroxy styrene) architectures were covalently tethered to either the chlorinated or unsaturated HDPE surface in an effort to ultimately tailor surface polarity and adhesiveness as well as create laminate poly(α-olefin) containing structures. This economical and benign surface chlorination/photochemical two-step treatment process produced relatively small disposal risks as well as no apparent polymer degradation.

The Effect of Macromolecular Architecture on Functional Group Accessibility: Hydrogen Bonding in Blends Containing Phenolic Photoresist Polymers

An investigation of phenolic functional group accessibility in linear poly(4-hydroxy styrene) (PHS) and novel, branched poly(4-hydroxystyrene) (PHS-B) is presented. The phase behavior and extent of hydrogen bonding in blends of PHS-B with complimentary Lewis base polymers are calculated from glass transition temperature (Tg) enhancements measured using differential scanning calorimetry (DSC) techniques. The fraction of PHS-B hydroxyls accessible for hydrogen bonding were compared to linear PHS chains and small molecular weight analogs to help establish a molecular architecture-functional group accessibility property relationship for use with dissolution inhibition in candidate microlithographic photoresist binders. Design approaches to macromolecular structure and architecture for tailored intermolecular interactions in phenolic systems are discussed with respect to the effects of local steric screening as well as an intriguing thermodynamic competition between inter- and intra-molecular hydrogen bonding via molecular mechanics modeling.

Polyelectrolyte effects in model photoresist developer solutions

We demonstrate that the deprotected photoresist poly(4-hydroxy styrene) is a polyelectrolyte when dissolved in aqueous base solutions. This polyelectrolyte effect manifests itself by the well-known monomer–monomer correlations as measured by small-angle neutron scattering. The correlation peak at the finite wave vector is a function of the solution ionic strength and polymer concentration. The weakening of the polyelectrolyte effects with added salts and excess base is also demonstrated. These studies emphasize the role of salt additives and aqueous base concentration and their influence on equilibrium solution properties such as the second virial coefficient and single chain radius of gyration. The fundamental role of these equilibrium properties with respect to the dissolution process is discussed.