PMMA surface

Figure 7.7 Abrasion resistance (haze) dependence on GPS A1(OBu)3 molar ratio for hybrid-coated PMMA surfaces compared to uncoated PMMA. PMMA substrate is corona treated followed by a 2.5% 3-aminopropyl-triethoxysilane treatment prior to the application of GPS Al(OBu)3 hybrid solutions. Coating thickness 4 mm coatings were cured at 80 °C for 4 h. (Reproduced from ref. 5, with permission.)...

The effect of constraints introduced by confining diblock copolymers between two solid surfaces was examined by Lambooy et al. (1994) and Russell et al. (1995). They studied a symmetric PS-PMMA diblock sandwiched between a silicon substrate, and silicon oxide evaporated onto the top (homopolymer PMMA) surface. Neutron reflectivity showed that lamellae formed parallel to the solid interfaces with PMMA at both surfaces. The period of the confined multilayers deviated from the bulk period in a cyclic manner as a function of the confined film thickness, as illustrated in Fig. 2.60. First-order transitions were observed at t d0 = (n + j)d0, where t is the film thickness and d0 is the bulk lamellar period, between expanded states with n layers and states with (n + 1) layers where d was contracted. Finally, the deviation from the bulk lamellar spacing was found to decrease with increasing film thickness (Lambooy et al. 1994 Russell et al. 1995). These experimental results are complemented by the phenomenologi-... 

EOF can be suppressed by coating the channel surface with methylhydroxy-ethylcellulose (MHEC) [631], orphotopolymerized polyacrylamide [415]. Reversal of EOF was also achieved, e.g., the PMMA surface was modified with N-lithioethylenediamine or N-lithiodiaminopropane [1063] or the PDMS surface was coated by hydrophobic interaction with TBA+ [302]. 

CZE separation of sugar isomers in a PMMA chip was enhanced by using a phosphate-based, rather than a borate-based buffer. The resolution enhancement may be caused by a rapid carbohydrate-phosphate complex formation process, as compared to a slow carbohydrate-borate complex formation process. To reduce adsorption of the labeled sugar isomers to the PMMA surface, 0.5% methylcel-lulose (viscosity of 2% aqueous solution at 20°C, 4000 cP) was added to the run buffer [560],... 

Enzymatic conversion of NBD-labeled ArgOEt to NBD-Arg was monitored in a PMMA microchannel. The enzyme, trypsin, was immobilized via the reactive ester groups on a phospholipid polymer adsorbed on the PMMA surface [ 1059]. 

Other than proteins, the immobilized enzyme was also used to digest DNA. For instance, the restriction endonuclease enzyme HaeJR was immobilized on an amine-modified PMMA surface to digest DNA [1063]. 

Kessler and coworkers immobilized RGD peptides to a PMMA surface via a spacer incorporating an azobenzene unit [ 187]. The molecules were arranged in such a way that the RGD motifs were accessible to cells approaching the surface when the azo unit was in the E-form, and were hidden from the cells when the azo unit was in the Z-form. This enabled the reversible modulation of mouse osteoblast adhesion by irradiation with visible or UV light. However, the difference between on and off states is not very pronounced. Possibly, the accessibility of the RGD motif is not... 

Figure 2. Wear pattern of PMMA against carbon black-reinforced polybutadiene rubber of 70 Shore A hardness. Left PMMA surface (X50) Right PMMA rolls on rubber surface (X100).

Chang CC, Merritt K. Microbial adherence on poly(methyl methacrylate) (PMMA) surfaces. J Biomed Mater Res 1992 26(2) 197-207. 

At this point of our understanding, the question arises whether one ean modify interfaeial traps of a polymer insulator surfaee in sueh a way that one gains eontrol over the electron transport in a transistor, e.g. by the introduction of -OH groups to an otherwise -OH free PMMA surface. Following earlier publications on modification of polymer surfaces, one can introduce keto and hydroxyl groups by exposing a PMMA dielectric to UV radiation in ambient atmosphere [42, 43]. Therefore, for the following experiments, the PMMA dielectric layer is exposed to 254 nm radiation for a time frame of 10 minutes and an optical power of 15 mW/cm prior to the pentacene deposition. 

Not surprizingly, in view of the preceding preference for hydrophobic surfaces, PAn can also be deposited by the in situ method on supports such as low-density polyethylene (LDPE).35 Modification of the LDPE surface by grafting with acrylic acid promotes the growth and adhesion of the PAn films. Conducting PAn coating may be similarly deposited on PVC and PMMA surfaces through chemical oxidative polymerization.36... 

When this chapter was written, there were only limited fluorescence lifetime data for single chromophores available, which had been measured with a near-field probe. The systems were similar to dye molecules dispersed either on a silica surface or on a PMMA surface. Of major concern was the perturbation of the fluorescence process by the presence of the metalized probing tip, which can lead to an alteration of the emission lifetime, to fluorescence quenching, and ultimately may limit the detection sensitivity and the spatial resolution of near-field fluorescence microscopy. The results are partly controversial, and more systematic work is required to explore the sensitivity limits, the resolution limits, and to elucidate the underlying physical processes. 

This result simply due to the dielectric boundary conditions imposed on the radiated field of a molecule at the interface. Here 1/Tnr and 1/Tril<1 are the non-radiative and the radiative rates, respectively. The quantity in the brackets accounts for the proximity of the interface at a distance z from the molecule. Algebraic expressions for the weighting functions L zyL and LyfylL are known [114] and depend on z and the refractive index ratio of the two materials that form the interface. The parameter 6t is the angle enclosed between the emission dipole moment and the surface normal. The weighting functions approach unity for z > A. For a molecule adsorbed on a PMMA surface in air, the lifetime should be 2.7 times longer when its emission dipole moment is perpendicular to the interface than when it lies in the surface. Also, the fluorescence quantum yield, defined as = 1 — (t/ rnr), is affected by the location and orientation of the molecule. 

Figure 35. Fluorescence lifetime versus peak emission wavelength /p for car-bocyanine dye molecules spin coated on a PMMA surface. In (a), the sample was overcoated with several micrometers of PMMA (crosses) or refractive index matching immersion oil (circles). The solid line is a fit of the radiative lifetime, Trad, to the upper bound of the data points. In (B) the molecules are at the PMMA-air interface the solid lines are calculated lifetimes for different polar orientations 6t of the emission dipoles and nonradiative decay rates l/tnr. (Adopted from [115].)...

Soper et al. [211] presented the fabrication of DNA microarrays onto PMMA surfaces using a UV modification protocol as shown in Fig. 11. Briefly, the PMMA surface was first activated via exposure to UV irradiation, which produced carboxylic acid functional groups onto its surface. EDC/NHS coupling chemistry was then used to facilitate the formation of succinimidyl ester intermediates on the surface, which allowed for the covalent attachment of amine-terminated... 

In many studies of wettability Zisman and coworkers have used the contact angles of a series of n-alkanes as a convenient means for determining for low energy solid surfaces [5,6,13,20]. In Figure 2 are plotted the cos 9 vs. 7lv° curves for the n-aUtanes on PMMA surfaces containing 0.5% additive I and 1.0% additive II. The critical surface tensions with additives I and n were 19 and 20 dynes per cm., respectively, representing a decrease of about 20 dynes per cm. from the value of obtained with the additive-free surface. Since the y values of 19 and 20 dynes per cm. are very close to that of 18 dynes per cm. reported by Fox and Zisman [l3] for the n-alkanes on poly-tetrafluoroethylene surfaces, it is apparent that a number of perfluoro-alkane groups are present in the outermost part of the surface phase with the principal axis of each carbon-carbon chain parallel to the surface. 

The substrate must be clean and free from particulate matter. Adhesion to acrylic plastics is normally excellent. We have found that the combination of isopropanol and acetic acid will gently attack and swell a polymethylmethacrylate (PMMA) surface and is more aggressive as the molecular weight of the PMMA is decreased. Excellent adhesion to polycarbonate can be obtained by heating the polycarbonate for two hours at 125°C before the coating is applied. 

Spherical porous Ti02 particles 1 to 50 xm in diameter have been created from colloidal PMMA particles having PDMS grafted to the PMMA surface. A mixture of... 

FIGURE 10.11 Microchip CE of EITC-BSA. (a) Polyethylene glycol (PEG)-grafted and (b) nntreated chip. Peaks la, lb, and Ic are the three main components of the BSA sample. The PEG was grafted onto the PMMA surface using an atom-transfer radical polymerization. (Reprinted from Liu, J. et al., Analytical Chemistry 76, 6953, 2004. With permission.)... 

Examples HA/autogenous bone surface-active glass ceramics/ poly(methyl methacrylate) (PMMA) surface-active glass/ metal fibers polylactic acid (PLA)Zcarbon fibers PLA/HA PLA/calcium/phosphorus-based glass fibers Tissue attachment Depends on materials... 

The PMMA surface was first imaged before rubbing, as shown in Fig. 7.20. The image on the left shows the topography, while the one on the right shows the NC EFM signal. 

Fig. 7.22. Topography (left) and NC EFM image (right) of the PMMA surface rubbed ten times [86].

The effect of rubbing the sample in two different directions was also investigated. The images in Fig. 7.25 show a PMMA surface rubbed once in one direction and then once in another direction forming about 45 degrees with respect to with the first one. The results show that the initial orientation of the charge domains induced by the first rubbing direction are not erased. 

Figure 10.1.3. Intensity ratio vs DN and AN. [Adapted, Figure 10.1.4. PMMA surface content vs. intensity ratio, by permission, from M L Abel, M M Chehimi, [Data fiorn M L Abel, M M Chehimi, 5yntAe

The leaks between the relatively even PMMA surface and the glass chip were of capillary nature. The capillary leaks were filled immediately upon filling of the system and did not disturb the flow characteristics of the channel. They could only be observed under the microscope and... 

One of the earliest methods for modification of a PMMA surface for medical applications is based on chemical conversion of the wall rather than on addition of a new layer [9]. The conversion of PMMA consists of reesterificatitMi of PMMA with polyfunctional hydroxyl compounds, such as ethylene glycol, glycerol, mannitol, or saccharose. First, the PMMA surface is covered with ethylene glycol or another polyalcohol, which is allowed to diffuse inside the polymer body. Then the surface is treated with hot sulfuric acid to perform reesterification and replace the methanol in PMMA with ethylene glycol. After neutralization with sodium bicarbonate, a hydrophilic, transparent layer is formed on the surface of the PMMA. 

---