Structure Of PMMA Research Articles

Direct photo-etching of poly(methyl methacrylate) using focused extreme ultraviolet radiation from a table-top laser-induced plasma source

In order to perform material interaction studies with intense extreme ultraviolet (EUV) radiation, a Schwarzschild mirror objective coated with Mo/Si multilayers was adapted to a compact laser-based EUV plasma source (pulse energy 3 mJ at λ=13.5 nm, plasma diameter ∼300 μm). By 10× demagnified imaging of the plasma a pulse energy density of ∼75 mJ∕cm2 at a pulse length of 6 ns can be achieved in the image plane of the objective. As demonstrated for poly(methyl methacrylate) (PMMA), photoetching of polymer surfaces is possible at this EUV fluence level. This paper presents first results, including a systematic determination of PMMA etching rates under EUV irradiation. Furthermore, the contribution of out-of-band radiation to the surface etching of PMMA was investigated by conducting a diffraction experiment for spectral discrimination from higher wavelength radiation. Imaging of a pinhole positioned behind the plasma accomplished the generation of an EUV spot of 1 μm diameter, which was employed for direct writing of surface structures in PMMA.

Atom Transfer Radical Polymerization of MMA Initiated by 2‐(4‐chloromethyl‐phenyl)‐benzoxazole and Fluorescent Property of PMMA

Atom transfer radical polymerization (ATRP) of MMA was conducted using 2‐(4‐chloromethyl‐phenyl)‐benzoxazole as initiator, CuCl as catalyst, and PMDETA as ligand. The results show that the polymerization is a first order reaction with respect to monomer concentration. The polymerization displayed living character as evidenced by a liner increase of monomer weight with conversation and a relatively narrow distribution (Mn/Mw range from 1.30 to 1.45). The structure of PMMA was analyzed by 1H‐NMR and proved the polymerization could be controlled to some degree. The optical property of the initiator was well preserved in the resulting PMMA, and the end‐functionalized PMMA exhibited fluorescent emission at 360 nm whether in DMF solution or in film state.

Poly (dimethyl siloxane) micro/nanostructure replication using proton beam written masters

Proton beam writing (PBW) has been proven to be a powerful tool for fabricating micro and nanostructures with high aspect ratio. However, being a direct-write technique, and therefore, a serial process, PBW is not economic for low cost multiple component production. Techniques for replicating PBW structures with low cost are necessary for applications in for example nanofluidics, tissue engineering and optical devices. We have investigated casting poly (dimethyl siloxane) (PDMS Sylgard 184, Dow Corning Corp.) with PBW structures as masters. First, a 2 MeV focused H 2 + beam was written into a 2 μm thick PMMA layer spin coated onto 50 μm thick Kapton film substrate. Next, these PMMA structures, with details down to 700 nm, were replicated with PDMS. Without any release coating treatment, PDMS circular pillars, 700 nm in diameter were successfully replicated. We also fabricated a nickel master with nanofeature dimensions and 2 μm depth using proton beam writing and sulfamate electroplating. The nickel master was used to successfully replicate a prototype DNA separation chip using PDMS.

Growth of osteoblasts on lithographically modified surfaces

Here we report about preliminary investigations on developing substrates for culturing osteoblasts, the cells responsible for production of mineralised bone, by lithographically modifying the surfaces of several materials. The proton beam writing system at the National University of Singapore was used to fabricate high aspect ratio structures in PMMA, while two-dimensional low aspect ratio structures were fabricated using conventional electron beam lithography (EBL) and UV lithography (UVL) in SU-8. It was found that oxygen plasma treatment of structured SU-8 surfaces changed the surface layer and significantly improved cell attachment and proliferation. Cells grown on patterned thick PMMA exhibit a remarkable geometry-dependent behaviour.

Micro/Nanofabrication by Spin Dewetting on a Poly(Dimethylsiloxane) Mold

ABSTRACTThe process of spin dewetting was used to fabricate polymer micro and nanostructures from poly(methyl methacrylate) (PMMA), poly (propyl methacrylate) (PPMA), and polystyrene (PS). Polymer structures were formed on poly(dimethylsiloxane) (PDMS) molds by dewetting of a polymer solution during spin coating. Features were removed from the mold using heat and pressure to transfer the polymer to silicon or glass substrates. By varying the coating conditions, a variety of different polymer feature morphologies were obtained for a given PDMS mold geometry. In this study, the ability to fabrication polymer micro and nanostructures using spin dewetting was demonstrated on a variety of PDMS mold geometries. The effects of polymer solution concentration and mold feature size on the resulting polymer structures were examined. In addition, microfabricated PMMA structures were used as etch masks for anisotropic etching of silicon in an aqueous solution of tetramethylammonium hydroxide (TMAH).

Morphological and Physical Properties of Triblock Copolymers of Methyl Methacrylate and 2-Ethylhexyl Methacrylate

Triblock copolymers of methyl methacrylate (MMA) and 2-ethylhexyl methacrylate (EHMA) [that is, poly(MMA-EHMA-MMA)] were prepared by an emulsion atom-transfer radical polymerization. The relationships of their structural, morphological, and physical properties were investigated. The latex particles had core-shell morphologies and the block copolymers experienced phase separation. Small latex particles with a low number of cores could deform and wet silicon-wafer surfaces, but the deformation of large latex particles was restricted by the internal two-phase morphology of the particles. Latex casting produced continuous pinholefree films, in which hard poly(MMA) (PMMA) cores of different latex particles merged and provided interparticle connections. The morphology of solution-cast films depended on block composition, solvent type, and film thickness. For all the prepared polymer samples, thick films cast in toluene had poly(EHMA) (PEHMA) materials at air surface, whereas those cast in tetrahydrofuran had a sponge-like PMMA surface structure. Thin toluene-cast films from P(MMA-EHMA-MMA) with the block degrees of polymerization (DP) 200-930-200 showed spherical PMMA domains and those from 380-930-380 yielded a protruded worm-like PMMA structure. The copolymer materials were coated on a glass surface for peeling tests. The films gave good hot-melt adhesion properties when the DP of the PEHMA block was over 600. The peeling strength depended on the lengths of both PEHMA and PMMA blocks. The P(MMA-EHMA-MMA) sample with DPs of 310-930-310 yielded the highest peeling strength of 7.4 kgf·inch -1 . The developed material is demonstrated to be a good candidate for a solvent-free, hotmelt, pressure-sensitive adhesives for special-purpose applications such as medical tapes and labels.

Effect of the medium on the stereostructure of poly(methyl methacrylate) synthesized in ionic liquids

AbstractPoly(methyl methacrylate) (PMMA) was synthesized in different ionic liquids (IL) by free radical polymerization. The average molecular weight and polydispersity of the PMMA were measured by gel permeation chromatography. It is found that ILs have effect not only on the molecular weights but also on the stereostructure of PMMA. From the FTIR and NMR analysis, it was confirmed that the chemical structure of PMMA synthesized in ILs was similar to the one obtained in conventional solvents while the stereostructure was influenced by the different IL used. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2199–2202, 2006

Production of loaded PMMA structures using the supercritical CO 2 phase inversion process

Loaded poly (methyl methacrylate) porous structures have been prepared using a supercritical fluid-phase inversion process in which CO 2 acts as the nonsolvent. We preliminary tested the possibility of producing PMMA porous structures using the supercritical fluid assisted phase inversion process; experiments were performed at various polymer concentrations, temperatures and pressures using two different solvents: dimethylsulfoxide (DMSO) and acetone. Then, we prepared PMMA structures loaded with an antibiotic, amoxicillin, using two different techniques: dissolving it in the same organic solvent used to solubilize the polymer or suspending the drug in the organic solution formed by polymer and solvent. The obtained porous structures, produced at various drug loading, were characterized by SEM, to study the morphology and cells size, and by DSC to analyze the interaction of drug–polymer in the structure. Some drug release rate analysis from the structure was also performed observing very different release behaviors depending on the solution/suspension process adopted.

Polymer-based wide-bandwidth and high-sensitivity micromachined electron tunneling accelerometers using hot embossing

The first PMMA-based membrane tunneling accelerometers were fabricated by hot embossing replication with silicon molds. The silicon molds were prepared by a combinative etching technique involving anisotropic bulk etching and modified plasma dry etching. The constructed molds hold both pyramid pits and positive profile sidewalls with smooth surfaces and steep angles, which were necessary for the hot embossing demolding. After electrodes patterned on embossed PMMA structures, the accelerometers, 8 mm /spl times/8 mm /spl times/1 mm, were packaged and assembled on a measurement circuit board. The exponential relationship between tip currents and applied deflection voltages presented a tunneling barrier height of 0.17 eV. The natural frequency of sensors was about 128 Hz. The bandwidth of the feedback system was 6.3 kHz. The sensitivity of voltage over acceleration was 20.6 V/g, and the resolution was 0.2485 /spl mu/g//spl radic/Hz (g=9.8 m/s/sup 2/).

Fracture investigation of PMMA specimen using coherent gradient sensing (CGS) technology

In this paper, the principle of coherent gradient sensing (CGS) technology in the transmission mode is briefly introduced. Fracture experiments of the PMMA specimens with offset crack under three-point-bending are performed using the CGS optical method. A series of CGS fringe patterns around the crack tip is used to study the fracture characteristics of the cracked specimens, such as the evolution of the crack tip stresses, deformation field and crack initiation, etc. Based on the K-dominance condition, the stress intensity factors at the crack tip are extracted by means of the distribution of CGS fringes, which show good agreement compared with the results from finite element analysis. The influences of the offset distance on fracture characterization are discussed. These results will be useful for evaluating the strength and lifespan of PMMA materials and structures.

Synthesis and morphological characterization of PMMA/polyaniline nanofiber composites

Poly (methyl methacrylate) (PMMA)/Polyaniline nanofibers composite films were prepared by solution casting. Doped polyaniline self-assembled nanofibers (PANFs) were synthesized by interfacial polymerization performed in an aqueous HCl/dichloromethane biphasic system in the presence of ammonium peroxydisulfate as oxidant agent. Sodium dodecyl sulfate (SDS) was added to the organic phase in order to verify possible modification the morphology the nanostrucutures when compared with previous reports. Treatment in an ultrasonic bath of PANFs on butanone resulted in a green dispersion (up to 250mg/dL). Dispersed PANFs were then combined with PMMA/butanone solution. Additional sonication and posterior film cast from solution procedures resulted in slight green PMMA/PANFs 0.15–0.30% (wt/wt) composite films. Film composites were characterized by UV–Vis spectroscopy and Scanning Electron Microscopy (SEM). PANFs powder was investigated by (SEM).An investigation by viscosity method on molecular structure of neat PMMA exposed to ultrasonic irradiation up to 2h showed small change (<5%) in the viscosity-average molar mass, Mv (≈100kg/mol). It suggests that mechanical degradation by cavitation does not occur on PMMA under those conditions. Thus, ultrasonic bath treatment is a simple, accessible method for mitigating solubility problems of PANI doped with inorganic acids and improving quality of low concentration PMMA/PANI composites. Application of these composites relies on the radiolytic stabilization effects of PANI on PMMA matrix.

Study of a core-shell type impact modifier by inverse gas chromatography

Inverse gas chromatography (IGC) has been used to study the Lewis acid–base properties of a technologically and commercially important core-shell type elastomer (MBS rubber). The parameters determined were the dispersive component of the surface tension, the surface free energy, the enthalpy and the entropy of adsorption of polar and apolar probes, the surface Lewis acidity constant ( K a), and the surface Lewis basicity constant ( K b). The results show that the MBS rubber is amphoteric but strongly Lewis basic. It is weakly Lewis acidic. The results are in accord with the analysis of the molecular structure of PMMA, the shell component of this impact modifier (IM). The interactivity of this elastomer with the remaining materials in multicomponent polymeric systems is expected to be strongly influenced by the particular surface energetic properties of the MBS rubber. The results presented would contribute to the interpretation, forecast and optimization of the adhesion properties and phase preferences shown by this impact modifier when incorporated in such complex polymeric systems as polymer blends and composites.

Synthesis and Direct Topology Visualization of High-Molecular-Weight Star PMMA

We report synthesis and direct topology visualization of single molecules of six-arm star poly(methyl methacrylate) (PMMA). We synthesized two hexafunctional initiators, 2,3,6,7,10,11-triphenylene hexa-2-bromo-2-methylpropionate (fused-core initiator) and ethylene glycol bis[3,4,5-tri(2-bromo-2-methylpropionate)] benzoylate (linear-core initiator). Their structures differ in the linking arrangement of the initiating sites. Atom transfer radical polymerizations (ATRP) of methyl methacrylate (MMA) from these initiators using CuCl as the catalyst and 4,4‘-di-n-nonyl-2,2‘-bipyridine as the ligand at 90 °C produced six-arm star PMMAs with very high molecular weight (Mw> 2 million) and narrow molecular weight distribution (polydispersity index ≈ 1.3). A high initiation efficiency (>90%) of the initiating sites is inferred from a good match of the Mw of the star PMMA with the expected value based on Mw of the cleaved arms. SEC-LS analysis confirmed the compact structure of the star PMMA compared to linear PMM...

Structure quality of high aspect ratio sub-micron polymer structures patterned at the electron storage ring ANKA

We describe the fabrication of polymer structures with lateral dimensions in the sub-micron regime using hard x rays (λ≈0.4nm) from the electron storage ring ANKA. PMMA and Novolak resists have been analyzed with respect to development rates and contrast. Films with a thickness from 2μmto11μm have been patterned using a high resolution x-ray mask consisting of 2μm thick gold absorbers on a suspended silicon nitride membrane. The fabrication of those sub-micron x-ray lithography structures is confined by the mask absorber sizes of down to 400nm and by the process conditions. The yield of resist structures with aspect ratios of 9 and above is limited by bending of the structures. An intermediate buffer layer of polyimide enhances the resist adhesion and reduces cracking in the microstructures. Diffraction at mask absorber edges biases the resist feature size on the order of tens of nanometers. It may also result in surface attack of periodic resist structures if the proximity gap between mask and resist chosen is too high. Resist surfaces are subject to rounding which can locally diminish the sidewall verticality. PMMA structures have been successfully used as a template for electroplating of 1μm thick gold to demonstrate the fabrication capability of sub-micron scale metal parts.

Cibacron Blue F3GA incorporated poly(methylmethacrylate) beads for albumin adsorption in batch system

Abstract A new adsorbent was prepared to obtain high albumin adsorption capacity utilizing Cibacron Blue F3GA as a dye ligand. Poly(methylmethacrylate) (PMMA) beads (100–150 μm in diameter) were produced by suspension polymerization. Ester groups in the PMMA structure were converted to imine groups by reacting with poly(ethylene imine) (PEI) in the presence of NaH. Then, dye ligand, Cibacron Blue F3GA, was covalently attached onto PMMA/PEI beads for human serum albumin (HSA) adsorption from both aqueous solutions and human plasma. Cibacron Blue F3GA loading was found to be 95.8 μmol g −1 . HSA adsorption onto PMMA, PMMA/PEI and Cibacron Blue F3GA-attached PMMA/PEI beads was investigated batchwise. The adsorption of HSA onto PMMA was low (6.0 mg g −1 ). Cibaron Blue F3GA attachment onto the beads increased significantly the HSA adsorption (26.0 mg g −1 ). The maximum HSA adsorption was observed at pH 5.0. Higher HSA adsorption was observed from human plasma (64.3 mg HSA g −1 ). Adsorption of other serum proteins were found to be 2.8 mg g −1 for fibrinogen and 5.3 mg g −1 for γ-globulins. The total protein adsorption was determined as 73.1 mg g −1 . Desorption of HSA was obtained using 0.5 M KSCN solution. High desorption ratios (up to 98% of the adsorbed HSA) were observed. It was possible to reuse Cibacron Blue F3GA-attached PMMA/PEI beads without significant decrease in the HSA adsorption capacity.

Synthesis of Nanometer-Sized Poly (methyl methacrylate) Polymer Network by Gold Nanoparticle Template

Gold nanoparticle/polymer composites have been produced using a one-system polymer synthesis. The linear polymer, poly (methyl methacrylate) (PMMA, MW = 15,000 g/mol) is applied for the stabilization of gold nanoparticles. The Fourier transfer infrared (FT-IR) analysis data and transition electron microscopy (TEM) image reveal that the core shell structure of gold/PMMA nanocomposite has been synthesized. The ratio of the concentration of the capping polymer material to the concentration of the gold precursor could control the sizes of gold nanoparticles. With specific concentration of the reductant, the core-shell nanostructure could be fluctuated in order. After heating treatment, the network structure of PMMA capped gold nanoparticles could be synthesized as confirmed by the TEM image. The result indicates that PMMA not only acts as the stabilizer, but also as the bridge of the neighboring gold nanoparticles.

Structures induced in polysilane and thin polysilane layer coated polymer films by irradiation of femto-second laser pulse

We investigated the structures induced in polysilane and polysilane coated thermoplastic bis-phenol A type epoxy (Epoxy) and poly(methyl methacrylate) (PMMA) films by irradiation of near-infrared (NIR) femto-second laser pulse. Long stripe-shaped structures with approximately 200–400 μm length was induced in polysilane bulk. Thin polysilane layer coated Epoxy and PMMA films showed photo-sensitive effect on the formation of stripe-shaped structures in PMMA and Epoxy, whereas no structures were induced in uncoated PMMA and Epoxy films. An ensemble of stripe-shaped structures worked as a diffraction grating. This photo-sensitive effect has potential application to grating structures in optical polymeric fiber (OPF).

Morphology and chemical structure of poly(methyl methacrylate) surfaces and interfaces: restructuring behavior induced by the deposition of SiO 2

The surface morphology, molecular structure, and the surface restructuring behavior after the deposition of a SiO 2 layer on poly(methyl methacrylate) (PMMA) have been investigated by using atomic force microscopy (AFM) in contact mode and sum-frequency generation (SFG) vibrational spectroscopy. AFM images show that the surface of PMMA is quite flat and sporadically contains dendritic features, which are micro-crystalline structures of PMMA. From the SFG measurements, the ester methyl groups of PMMA are pointed away from the surface plane at least in the surface region. By depositing a SiO 2 film, the SFG signal intensity is significantly reduced, indicating that the CO and the ester methyl groups are aligned nearly parallel to the surface plane.

High aspect ratio, 3D structuring of photoresist materials by ion beam LIGA

IB-LIGA (Ion Beam Lithographie, Galvanoformung and Abformung) is a new technique for the 3D structuring of photoresist materials. It is a direct-write (maskless) technique that uses high energy (0.5–3.5 MeV) light ions (protons or helium ions) for the irradiation of photoresist materials. At CAFI (Centre d’Analyse par Faisceau Ionique), the IB-LIGA technique has been implemented. The experimental parameters for irradiation and the subsequent development have been optimised for PMMA. The results obtained so far are presented. These results include irradiations with different beam energies to control the depth, different sample tilt angles to produce sloping structures, and production of walls by moving the sample. Real 3D structures can be obtained in this way as shown in the examples. These examples show that structures in PMMA can be obtained with smooth near 90° side walls and bottom surfaces with low roughness. High aspect ratios have also been obtained, the current maximum is about 40. An ion-beam focussing system has recently been installed at CAFI, to produce ion-beams with sub-micrometer dimensions which can be accurately scanned in an arbitrary pattern over an area of 2.5×2.5 mm.

Manufacturing Aspects of LIGA Technologies

Different concepts for the manufacture of masks for deep X-ray LIGA are presented. The variation in the accuracy of the final mask as a function of the mask manufacture concept (low, medium or high resolution) influences the sidewall roughness of the irradiated PMMA structures considerably. The mask membrane also influences structure quality. Graphite masks, which yield PMMA resist structures with straight sidewalls, have increased surface roughnesses (>2 μm Rz) comopared to beryllium.A design of experiments approach to the optimisation of PMMA for LIGA applications with deep X-ray lithography has been undertaken. For the optimisation, 18 different resist mixtures were produced on the basis of the significant parameters, holding the parameters within values that were experimentally shown to be conducive for PMMA resist production. High ratios of crosslinker in the resist mixture was shown to lead to significant amounts of resist residue between the microstructures; resist development was significantly hindered. Other resists with higher ratios of adhesion promotor in the resist also had significant problems with development. PMMA resist mixtures containing between 2% and 5% adhesion promotor led to microstructures with sufficient adhesion to the substrate surface without any substantial problems with the development step.A variant of the LIGA-process, which involves deep silicon etching for mastering, has successfully been applied for the fabrication of disposable plastic chips for 2-dimensional electrophoresis. The high precision and structure accuracy of the replicated plastic devices as well as the possibility to pattern complex multilevel structures demonstrate the huge potential of LIGA based on silicon micromachining for the realization of microfluidic and biomedical devices