PMMA thin film

Okubo et al. have used Stark spectroscopy to study the unusual trinuclear complex salt (76) which has pseudo D3h symmetry and contains tetrahedral Cu1 centers and a symmetrical hexa-azatriphenylene-derived radical anionic ligand.139 The x responses of PMMA thin films doped with (76) are enhanced by an intense, broad MLCT transition which has a maximal absorbance in the NIR region.139... 

Fig. 2.11 Absorption spectrum of a DH6/PMMA thin film after it is exposed to DNT vapor at 65°C for various periods of time. The peak at about 630 nm is the characteristic absorption peak of the chromophore. Reprinted from Ref. 33 with permission. 2008 American Chemical Society...

Fig. 2.13 Comparison of the absorption spectra of two DH6/PMMA thin films redissolved in cyclopentanone. One is a pristine film without being exposed to DNT and the other is a film that has been exposed to DNT and has changed color. After they are redissolved in solvent, the absorption spectra of both samples have the same peak wavelength and shape. The difference in the height of the peak is due to the difference in the concentration of the two polymer solutions, and is not important in the comparison. Reprinted from Ref. 33 with permission. 2008 American Chemical Society...

Fig. 28 Temperature dependence of the strain to craze for PMMA thin films at a strain rate of 2 x 10-3 s-1...

Previous studies on paraffins, rhodamine dyes, and l,3-bis(N-carbozoyl) propane excimers have concluded that there is a relationship between km and polymer viscosity and free volume [103-105], Indeed, this dependence has been investigated in the context of decreasing free volume during methyl methacrylate polymerization [83,84], It has been shown that the nonradiative decay processes follow an exponential relationship with polymer free volume (vf), in which kra reduces as free volume is decreased [see Eq. (5)]. Here, k. represents the intrinsic rate of molecular nonradiative relaxation, v0 is the van der Waals volume of the probe molecule, and b is a constant that is particular to the probe species. Clearly, the experimentally observed changes in both emission intensity and lifetime for/ac-ClRe(CO)3(4,7-Ph2-phen) in the TMPTA/PMMA thin film are entirely consistent with this rationale. 

ClRe(CO)3(4,7-Ph2-phen) in the 1 1 (by weight) acrylate-based TMPTA/PMMA 0.25-mm thin film as a function of UV-irradiation time (A) with and ( ) without added acetophenone photoinitiator. Excitation wavelength is 420 nm. (b) Plot of normalized area of acrylate monomer infrared ATR band at 808 cm-1 as a function of UV-irradiation time in the TMPTA/PMMA thin film. (From Ref. 100.)... 

Figure 21 depicts emission spectra recorded from the same composition of TMPTA/PMMA thin film at 293 K following excitation at 400 nm. Prior to UV irradiation, the characteristic dual 3MLCT emission features of W(CO)4-(4-Me-phen) are observable at 520 and 750 nm, and the spectrum is similar to that determined in fluid solution (see Fig. 3). However, after UV irradiation for 60 s the two 3MLCT emission bands become almost equivalent in intensity and their maxima have moved to 525 and 715 nm, respectively. Without addition of the W(CO)4(4-Me-phen) complex, the unirradiated thin film gives rise to no detectable emission in the 450 to 800-nm region. Following UV irradiation, however, substantial scattered light is observed in the 420 to 620-nm region.

Recently spin-coated PMMA thin films with a thickness of 0.45 pm on silicon wafer were irradiated with various ion beams (H+, He+, N+, Ni3+). Ion beam energy regions are from 300 keV to 4 MeV. Irradiated PMMA films were developed by isopropyl alcohol in these experiments. After the irradiation by ion beams on PMMA in a vacuum, the thickness of the films were measured both before and after development. Various radiation effects on PMMA films such as ablation (sputtering), main chain scission, and positive-negative inversion were observed as shown in Fig. 11. These phenomena are very different from those in 60 Co gamma-ray or electron beam irradiation. Large LET effects are considered to be due to high density excitation by ion beams. 

Two methods could be used to prepare the disk samples. One is spin coating. Compound 96 and poly (methyl methacrylate) (PMMA) were dissolved in cyclohexanone and the solution spun coated onto the disk substrate to prepare a photosensitive PMMA thin film on the disk doped with compound 96. The second method is direct evaporation of pure compound 96 to the disk under high vacuum conditions. The structure of the photochromic optical disk sample is shown in Figure 4.3. 

Figure 7.12. (a) TEM images of a MWCNT-containing PMMA thin film taken at different times (i) t = 0, (ii) t = 4, and (iii) t=10 min and (b) SEM image of the g-MWCNT-PMMA composite. Reprinted with permission from Wiley VCH (69). 

FIG- 12.8 THG in the DRl-PMMA thin film pumped by the fundamental beam as a function of time. The average intensity of the pumping beam is shown in each diagram. 

Song R., Chiang, M.Y.M., Crosby, A. J., Karim, A. and Amis, E. J., The combinatorial Measurement on the Adhesion of PMMA Thin Film in Nano Range, in preparation. 

Fig. 2.35 AFM height images and corresponding cross sectional analyses of a PMMA thin film on silicon that was partially removed in the vertical direction (a raw data b d planefitted data, details see text)...

Yu et al. [36] have reported applications of pyrryl fulgides with respect to optical data storage. More than 500 UV-irradiation and photobleaching (He-Ne laser, 632.8 nm) cycles of an optical disk coated with PMMA thin film doped with pyrryl fulgide without fatigue resistance of formation photodecomposed species were demonstrated. 

The photoisomerization of the push-pull azobenzene derivative disperse red 1 (DRl) has also been shown recently to occur efficiently in poly-(methyl metacrylate) (PMMA) thin films at room temperature [23,24]. DRl is a pseudo-stilbene type azobenzene molecule, as classified by Rau. This means that the high-energy n-n transition is overlapping the low energy n-n transition, which leads to a large structureless band in the trans isomer and... 

FIG. 10.8 Photoswitehing of SHG signal (upper curve) in photochrome doped PMMA thin films (previously poled). UV irradiation is performed at 355 nm and visible irradiation at 514 nm. Optical density (lower curve) is measured within the absorption band of the colored isomer (532 nm) to follow the photo-reaction. No electric field is applied during these experiments, (a) %>iroRrran (nicro-BIPS, Figure 10.3) 25% w/w and (b) Furylfulgide (Aberchrome 540 ) 10% w/w. (Reprinted from ref. 73 by permission of Taylor Francis Ltd. http //www.tandf.co.uk/loumals). 

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