Molecular Weight Poly Methyl Methacrylate Research Articles

Study on Polymer and Process Design in Thermal Nanoimprint Lithography

Rapid process is one of the most important issues for industrial usages in thermal Nanoimprint Lithography (NIL). Detail study on the polymer deformation process time is indispensable to design process conditions and resist polymer characteristics. We experimentally study the dependence of the process time on the resist properties and predict required process time for various molecular weights in Poly- Methyl Methacrylate (PMMA). The time evaluation of the resist profile for various molecular weights (Mw) is observed and obtained the deformation process time in experimentally. According to the measurement of viscosity of polymers and experimental results, the relation between the viscosity and the process time is investigated for various molecular weight of PMMA. The results indicate that the deformation process time T[s] is fairly proportional to the viscosity of the polymer. From this relation, the required process time is predicted in various process temperatures and molecular weights in PMMA.

PMMA-based polymer gel electrolytes containing NH 4PF 6: Role of molecular weight of polymer

The effect of the molecular weight of polymethylmethacrylate (PMMA) on the conductivity and viscosity behavior of proton conducting polymer gel electrolytes containing ammonium hexafluorophosphate (NH 4PF 6) in propylene carbonate (PC) has been studied. The addition of PMMA having molecular weights: 15,000; 120,000; 350,000; 996,000 results in an increase in conductivity and gels with conductivity higher than the corresponding liquid electrolytes have been obtained. The maxima observed in the variation of conductivity with PMMA concentration shifts towards higher concentrations of PMMA with an increase in the molecular weight of PMMA. The increase in conductivity with PMMA addition also depends upon the molecular weight of PMMA and has been found to be more for gels containing PMMA with lowest molecular weight (15,000). The increase in conductivity at low concentrations of PMMA is due to an increase in free ion concentration with the dissociation of ion aggregates, whereas the decrease in conductivity at higher concentrations of PMMA, is due to the exponential increase in viscosity, which lowers mobility and as a result conductivity decreases. These gels show high value of conductivity (∼10 −2 S/cm at 25 °C) which does not vary with time and shows only a small increase over the 20–100 °C temperature range and is desirable for their potential use in applications.

Influence of polymer phase separation on roughness of resist features in UVIII

The origin of feature roughness in a chemically amplified positive resist (UVIII) is investigated using atomic force microscope (AFM) imaging. Although the mechanism for exposure in chemically amplified resist differs from that in conventional resists such as polymethylmethacrylate (PMMA), we find a similar dependence of roughness with exposure dose, suggesting a similar origin. The feature roughness in PMMA has been suggested to be due to polymer phase separation during development, which can occur also during the development of UVIII. However, the maximum extent of the roughness in UVIII is more than one order of magnitude smaller than that found in high molecular weight PMMA, which is attributed to the larger radius of gyration for the latter.

PMMA to SU-8 bonding for polymer based lab-on-a-chip systems with integrated optics

An adhesive bonding technique for wafer-level sealing of SU-8 based lab-on-a-chip microsystems with integrated optical components is presented. Microfluidic channels and optical components, e.g. waveguides, are fabricated in cross-linked SU-8 and sealed with a Pyrex glass substrate by means of an intermediate layer of 950k molecular weight poly-methylmethacrylate (PMMA). Due to a lower refractive index of PMMA (n = 1.49 at λ = 600–900 nm) this bonding technique preserves waveguiding in the cross-linked SU-8 structures (n = 1.59 at λ = 633 nm) in combination with good sealing of the microfluidic channels. The bonding strength dependence on bonding temperature and bonding force is investigated. A maximum bonding strength of 16 MPa is achieved at bonding temperatures between 110 °C and 120 °C, at a bonding force of 2000 N on a 4 inch wafer. The optical propagation loss of multi-mode 10 µm (thickness) × 30 µm (width) SU-8 waveguides is measured. The propagation loss in PMMA bonded waveguide structures is more than 5 dB cm−1 lower, at wavelengths between 600 nm and 900 nm, than in similar structures bonded by an intermediate layer of SU-8. Furthermore 950k PMMA shows no tendency to flow into the bonded structures during bonding because of its high viscosity.

Influence of polymer phase separation on roughness of resist features in UVIII

The origin of feature roughness in a chemically amplified positive resist (UVIII) is investigated using atomic force microscope (AFM) imaging. Although the mechanism for exposure in chemically amplified resist differs from that in conventional resists such as polymethylmethacrylate (PMMA), we find a similar dependence of roughness with exposure dose, suggesting a similar origin. The feature roughness in PMMA has been suggested to be due to polymer phase separation during development, which can occur also during the development of UVIII. However, the maximum extent of the roughness in UVIII is more than one order of magnitude smaller than that found in high molecular weight PMMA, which is attributed to the larger radius of gyration for the latter.

Measurements on the surface glass transition of PMMA from the decay of imprinted surface corrugation gratings: the influence of molecular weight

The near-surface mobility of poly-methylmethacrylate (PMMA) chains is probed by means of optical diffraction. Particularly, we monitor the surface tension-driven decay of shallow surface corrugation gratings. The probe depth of the technique is about 100 nm. We report on quasi-static experiments, in which the sample temperature was ramped slowly from room temperature to a temperature well above the glass temperature, T g. An estimate of the near-surface T g is derived from the temperature at which the decay sets in, T dec. For high molecular weight PMMA this decay temperature is much less than the bulk T g as determined by calorimetry on the same material. For low molecular weight PMMA, this effect is absent.

Investigation into new materials for optical devices: the miscibility and solvent effects of azobenzene derivative blends

AbstractWith the increasing demand for novel devices with optical applications the search for new materials to data store and process becomes a priority. By introducing blends, tailor made properties and low cost give added advantage. Miscibility is an essential requirement for a new material, this research thus involves miscibility studies of poly(4‐(N‐(2‐methacryloyloxyethyl)‐N‐ethylamino)‐4′‐nitroazobenzene)90‐co‐(methyl methacrylate)10, (azobenzene derivative) with polymethyl‐methacrylate (PMMA), polyvinylacetate (PVAc) and polyvinylchloride (PVC) prepared in tetrahydrofuran (THF), and/or dimethylformamide (DMF) and/or dichloromethane (CH2Cl2). The glass transitions, solvent and varying molecular weight effect were investigated, since these all primarily influence the miscibility. THF was found to encourage miscibility at specific compositions of PVAc and PVC blends. However, with CH2Cl2 and DMF immiscibility is encouraged. The Fox–Flory equation was applied to the blends analyzing the PVC blends in DMF as deviations from ideality. Different molecular weights of PMMA were identified as immiscible regardless of solvent. PMMA's lower solubility in THF and CH2Cl2 compared to the azobenzene derivative, displayed the existence of PMMA islands. In all blends the favorable and unfavorable interactions between polymer–solvent–polymer systems are considered. Furthermore, the miscibility effect on increasing the MMA content of the azobenzene derivative was also investigated. Copyright © 2002 John Wiley & Sons, Ltd.

PMMA-based bioactive cement: effect of glass bead filler content and histological change with time.

A new bioactive bone cement (designated GBC), which is a polymethyl methacrylate (PMMA)-based composite consisting of bioactive glass beads as an inorganic filler and high molecular-weight PMMA as an organic matrix, has been developed. The purpose of the present study was to evaluate the effect of the filler content on the mechanical properties and osteoconductivity of GBC, to decide the most suitable filler proportion, and to evaluate the degree of cement degradation with time. The bioactive beads, consisting of MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) glass, were added to the cement in various proportions (40-70 wt %). The bending strength of GBC did not differ among the proportions (approximately 136 MPa), but the elastic modulus of bending of GBC increased as the glass bead filler content increased (approximately 4.1-7.2 GPa). The all types of GBC were packed into the intramedullary canals of rat tibiae to evaluate osteoconductivity, as determined by an affinity index calculated as the length of bone in direct contact with the cement surface expressed as a percentage of the total length of the cement surface. Rats were sacrificed at 4, 8, 25, and 39 weeks after implantation, and the affinity index was calculated for each type of GBC at each time point. Histologically, new bone had formed along the surface of all types of GBC within 4 weeks, even in GBC containing only 40 wt % of glass beads. The affinity indices of GBC tended to increase as the proportion of glass bead filler increased and as the implantation period increased. In GBC containing 60 or 70 wt % of glass beads, significant rapid increases in the affinity indices were found from 4 to 8 weeks, and the high values (approximately 70%) were maintained up to 39 weeks. A sign of glass bead degradation was observed at the bone-cement interface in the rat tibiae at 39 weeks. We conclude that, when mechanical properties and osteoconductivity are both taken into consideration, GBC containing 60 or 70 wt % of glass beads is the most suitable formulation, but that further studies are needed to investigate and overcome the degradation.

Resolution of polymethyl methacrylate: Molecular weights of 950 000 vs 50 000

The work examines the resolution and line-to-line resolution of two molecular weights of polymethyl methacrylate (PMMA), developed in 25%–50% solutions of methylisobutyl ketone in isopropanol. Both PMMA’s exhibited similar minimum linewidths of 15–18 nm. Measured linespread functions showed primary Gaussian standard deviations of 11.7 and 28 nm for the 950 and 50 K molecular weight PMMAs, respectively. Developer strength produced ⩽1 nm difference in the width of the linespread function. Atomic force microscope images of latent grating patterns show the same line-to-line resolution for the two undeveloped resists. Developed gratings show the 950 K PMMA to have superior line-to-line resolution. The results are analyzed through integration of the measured linespread functions.

Novel 2-Dimensionally Periodic Non-Constant Mean Curvature Morphologies of 3-Miktoarm Star Terpolymers of Styrene, Isoprene, and Methyl Methacrylate

The morphology of a family of four 3-miktoarm star terpolymers of polystyrene (PS), polyisoprene (PI), and polymethyl methacrylate (PMMA) was studied. For three of the samples, the molecular weight of the PMMA block was systematically varied while that of the PS and PI blocks were held fixed. In the fourth sample, the PS and PMMA blocks were approximately of the same molecular weight and the PI was the majority component. In all terpolymers, the system displayed a three-phase, two-dimensionally periodic microstructure of an inner PI column with a surrounding PS annulus in a matrix of PMMA. For the two samples with the longer PMMA blocks (218 and 186 kg/mol), the PI−PS and PS−PMMA interfaces were cylindrical, whereas a unique nonconstant mean curvature (non-CMC) concentric diamond prism shape of the PI and PS microdomains occurred for the sample with the lowest molecular weight PMMA block (144 Kg/mol) as well as the polymer with the longer PI block. In these star terpolymers there are three chemically diff...

Atomic force microscope studies of nanolithographic exposure and development of polymethylmethacrylate

Atomic force microscopy was employed to study e-beam exposure and pattern development of polymethylmethacrylate (PMMA) in molecular weights (MWs) of 950 and 50 K. The work focuses on the development of dense high resolution patterns. PMMA was found to have a nodular morphology with an average particle diameter of ∼53 nm. Submersion of unexposed PMMA in both water and mixtures of isopropanol (IPA) and 0–33% methylisobutylketone (MIBK) did not change the surface morphology. IPA mixtures with ⩾50% MIBK roughened the surface. Latent images of exposed resist were consistent with Monte Carlo simulations. The particle size limited the ability to resolve a 40 nm grating. A pillar type morphology was observed between the lines in the 40 nm period grating in 950 K MW PMMA developed in 25% and 50% MIBK. The particle size was not reduced in 50 K MW PMMA. In fact, the ability to define a 40 nm grating in 50 K molecular weight PMMA was worse. Patterns of large pads and 100 nm gratings did not exhibit the pillar morphology nor a difference in morphology between the two molecular weight resists.

Tetraphenylethane iniferters—8. Diphenylmethane diisocyanate-based polyurethane iniferter for “living” radical polymerization of methyl methacrylate

A novel polyurethane iniferter, synthesized from equal moles of 4,4′-diphenylmethane diisocyanate and 1,1,2,2-tetraphenyl-1,2-ethanediol was used to polymerize methyl methacrylate. The rate equation and overall activation energy have been determined using kinetic results. As the polymerization time and conversion increased, molecular weight of the polymethyl methacrylate also increased. Postpolymerization of polymethyl methacrylate in the presence of methyl methacrylate and styrene yields high molecular weight polymethyl methacrylate homopolymers and polymethyl methacrylate-polystyrene block copolymers respectively. Hence, the present polyurethane iniferter acts as a thermal iniferter and follows “living” radical polymerization.

Novel electron beam lithography technique for submicron T-gate fabrication

Submicron T gates have been fabricated using the high resolution electron beam lithography technique. The footprint of the T gate has been written in high molecular weight poly-methyl methacrylate (PMMA), whereas the top of the T gate is defined in AZ PF 514. A 400 nm thick layer of PMMA was first exposed and developed followed by the spinning of AZ PF 514. A wide line defining the top of the T gate was written in this resist which after development gave a T-shaped cross section. As both the bottom and the top of the T gate are dealt with independently, therefore, the technique provides a high degree of control and flexibility in the fabrication process. Moreover, the possibility of shorting of the top of the T gate with the Ohmic metallization is virtually impossible. Consequently, the process is a very good candidate for low-noise GaAs metal-semiconductor field-effect transistors (MESFETs) fabrication in which a narrow drain-to-source gap is required. GaAs MESFETs with T-shaped gates have been fabricated and characterized by dc measurements.

超高分子量ポリメチルメタクリレートのプレス延伸法による二軸延伸成形

超高分子量ポリメチルメタクリレートのプレス延伸法による二軸延伸成形

Reliable fabrication of sub-40 nm period gratings using a nanolithography system with interferometric dynamic focus control

Electron beam nanolithography tools readily permit the fabrication of ultra small structures. However, the disadvantage of such a system is that the depth of field is very small, making it difficult to maintain the focus of the system as the sample is moved due to sample topography, tilt, and stage run out. This presents a serious limitation to nanofabrication. To overcome this problem, we have built and installed a two color, heterodyne common path interferometer on a converted JEOL 100 CXII scanning transmission electron microscope. The interferometer compensates for the very small depth of field of the system by detecting variations in the sample working distance with respect to the electron optical objective lens, and dynamically correcting the lens current. The advantage of this system is that optical access to the sample can be made in a microscope with a very small working distance or sample space. To demonstrate this system, we have fabricated 38 nm period gratings on a silicon substrate. The process was a conventional one using a single 30 nm layer of 350 k molecular weight poly methyl methacrylate resist. The grating was exposed with a linear dose of 1.6 nC/cm and developed in 3:1 IPA:MIBK for 30 s at 23 °C. Patterns were transferred by lift off of an evaporated Ni/Au film. The gratings have a 1:1 mark:space ratio and a line-width variation of 5 nm at 4σ. The stage can be moved over large areas and from chip to chip, and the lithography repeated successfully. This system therefore permits reliable state-of-the-art nanolithography.

Effects of molecular weight on morphology and electrooptical properties of polymethylmethacrylate/liquid crystal composites fabricated by a solvent-induced phase separation method

The relationship between the electrooptical properties, morphology and molecular weight of polymethylmethacrylate (PMMA) in PMMA/liquid crystal composite films is clarified. The LC droplet size has decreased with increasing molecular weight of PMMA. The threshold voltage has increased with increasing molecular weight of PMMA in good agreement with a equation of Doaneet al, qualitatively. Electrooptical response characteristics have included fast and slow mode. Thermal motion of PMMA at the interface between PMMA and LC seems to affect response time.

Fabrication of high aspect ratio silicon pillars of <10 nm diameter

We report the fabrication of high aspect ratio, sub-10 nm size, structures in silicon without involving any wet chemical etching. A 50 nm thick double layer of low and high molecular weight polymethylmethacrylate resist was exposed with an 80 kV electron beam of diameter smaller than 5 nm. After exposure the resist was developed in 3:7 cellusolve: methanol with ultrasonic agitation during development. A 5 nm thick AuPd film was deposited by ionized beam evaporation and a metal pattern was obtained by liftoff. Sub-10 nm AuPd dots were recorded with a scanning electron microscope. The AuPd pattern was then used as a mask on the Si substrate which was etched with reactive ion etching. Silicon nanocolumns with diameters ranging from 5 to 7 nm and an aspect ratio of height to diameter of about 7:1 were obtained.

Analysis of Low Molecular Weight Polymers with Gel Permeation Chromatography

Abstract Intrinsic viscosities and gel permeation chromatography (GPC) elution times were determined in toluene on commercially available standards of polystyrene (PSTY) and polymethyl methacrylate (PMMA) having Mn in the range of 103 to 105 and 104 to 106, respectively. In addition, elution times were determined on the discrete GPC peaks of dimer, trimer, tetramer, etc. as seen in lower molecular weight PSTY and PMMA. Intrinsic viscosities of oligomers were estimated by extrapolation of the Mark-Houwind-Sakurada equations determined from our data, and the results were used to establish a universal calibration curve over a wide range of molecular weights. A similar approach was taken by using literature data for the intrinsic viscosities of PSTY and PMMA in tetra-hydrofuran. It was verified by proton NMR that the universal calibration curve so constructed is useful at Mn, values as low as 300. No correction was necessary for chain length dependence of the detector response.

Phase separation dynamics of polycarbonate/polymethyl methacrylate blends. II. Temperature jumps above an immiscibility loop

Blends of polycarbonate (PC) and moderately low molecular weight polymethyl methacrylate (PMMA) reveal an immiscibility loop in which an upper critical solution temperature (UCST) is located above a lower critical solution temperature (LCST). Temperature jump (T jump) experiments were conducted on a 40/60 PC/PMMA composition from a single phase (150 °C) to two-phase temperatures above the immiscibility loop (205–241 °C). Phase separation first occurs, then is accompanied by phase dissolution. The early stage of phase separation is explicable in terms of the linearized Cahn–Hilliard theory. The late stage of SD follows the power-law relationship with the exponents of −1/3 and 1 as predicted by the cluster theory of Binder and Stauffer. The universal curve was established with dimensionless variables of Qm and τ. The late stage data were analyzed in accordance with the recent scaling laws of Furukawa. Time evolution of structure function exhibits universality in the late stages of spinodal decomposition. The shape of the structure function can be scaled with slopes of 2 and −6 for q<qm and q>qm regions, respectively. At a later time, phase dissolution takes place and the system returns to a single phase.

In vitro evaluation of iris chafe protection afforded by hydrophilic surface modification of polymethylmethacrylate intraocular lenses

An in vitro iris chafe test was developed to evaluate possible differences in abrasive interaction of various intraocular lens (IOL) materials with the posterior surface of the iris. The materials that were compared in initial tests with rabbit irides were high molecular weight polymethylmethacrylate (PMMA), the primary IOL material in current use, and surface-modified PMMA, which had a permanent, chemically bound, hydrophilic, polymer surface. Scanning electron microscopy, light microscopy, and examination of histological sections were used to assess tissue damage. A “window defect” type of abrasive damage was observed by light microscopy for PMMA lenses and is very similar in appearance to that seen for iris abrasion by human implants when viewed in vivo in slitlamp examinations. Results for both pigmented and albino rabbit irides indicate a reduction in abrasive insult to the external iris basement membrane and underlying pigment epithelium by the hydrophilic surface modification of PMMA. These results are consistent with our observation of a major reduction in corneal endothelium damage on contact with the hydrophilic surface-modified PMMA as compared with PMMA itself. This in vitro iris abrasion test, therefore, appears to be a useful technique for future evaluation of IOL surface properties.