Thickness of the residual film

If allowance is made for the thickness of the residual film t, the relevant radius for the first group of pores would be = X -1- tj-... 

Fig. 2.7 Annealing time dependence of the thickness of the residual film, h esidue obtained from PS/H-Si (solid symbols) and bare H-Si (open symbols). The annealing was carried out at 150 °C in air. The PS has = 44.1 kg/mol and initial thickness, hg = 200 nm (Reproduced with permission from Ref. [33])...

Solvent Casting. The polymer is mixed with the plasticizer in the required proportion and dissolved in methylene chloride to form a 10% solution. Films are cast from this solution on a glass plate using a Gardner knife. The films are allowed to dry overnight at room temperature, and any residual solvent is removed by heating for 10 hours in an oven at 110°C. The thickness of the dry film should be about 100 n. 

Blends of sPP/POE were prepared by dissolving these polyolefins in xylene at about 100°C (at a polymer concentration of 2-3 wt%) and stirred thoroughly for about 1 day. Film specimens were prepared by solvent casting on optical microscope glass slides. To ensure complete removal of the solvent, the glass slides were immersed in distilled water (nonsolvent) for 1 h and then dried at the ambient temperature. Subsequently, the samples were further dried in a vacuum oven at room temperature for another 2 days. All samples were heated to 160°Cfor lOminto provide the blend with a thermal history similar to the melt-mixed samples and to further remove any residual solvent. The thickness of the blend films used for microscopy was approximately 10 pm (31). 

This is a relationship which can be applied to the estimate ofthe residual porosity ofsol-gel films. Their volume fraction of porosity, Vp, can be estimated from the film thickness, obtained for example by ellipsometry or mechanical profilometry and from the so-called infrared thickness (Almeida et al., 1994), determined from their IRspectra. The infrared thickness of the porous film is the thickness which it will exhibit after ftill densification this thickness, which is independent of the initial film porosity, is always less than the one measured for the porous film. As densification occurs at increasing temperatures, the IR thickness remains constant, but the experimentally determined, profilometer (or ellipsometer) thickness decreases (Almeida et al., 1994). This is due to the fact that the volume percent porosity decreases with the temperature and time ofheat treatment, but the amount of solid material remains basically the same. 

As shown in Table 5, in the mode I test, the thicknesses of the residual adhesive layer on the failure surfaces were about 250 xm for all the specimens with different surface preparations, which indicated that the failures all occurred in the middle of the adhesive layer in the test regardless of the surface preparation method since the total thickness of the adhesive of the specimens was 0.5 mm. When the phase angle increased as in the asymmetric DCB test with h/H = 0.75, which contains 3% of mode II fracture component, a layer of epoxy film with a thickness of around SO xm was detected on the failure surfaces of all the specimens. Although the failure was still cohesive, the decrease in the film thickness on the metal side of the failure surfaces indicated that the locus of failure shifted toward the interface due to the increase in the mode mixity. On the other hand, because the failure was still cohesive, no significant effect of interface properties on the locus of failure was observed. When the mode mixity increased to 14% as in the asymmetric DCB test with h/H = 0.5, where the mode mixity strongly forced the crack toward the interface, the effect of interface properties on the locus of failure became pronounced. In the specimen with adherends prepared with acetone wipe, a 4-nm-thick epoxy film was detected on the failure surfaces in the specimen with adherends treated with base/acid etch, the film thickness was 12 nm and in the P2 etched specimen, a visible layer of film, which was estimated to be about 100 nm, was observed on the failure surfaces. This increasing trend in the measured film thickness from the failure surfaces suggested that the advanced surface preparation methods enhance adhesion and displace failure from the interface, which also confirmed the indications obtained from the XPS analyses. In the ENF test, a similar trend in the variation of film thickness was observed. 

Here, we discuss any discernible influence of the adsorbed layer formation process on our dynamic measurement. As noted above, the viscosity of thick PS-SiOx with ho > 4Rg is the same as bulk viscosity [2]. This shows that the polymer chains constituting the adsorbed layer should make insignificant contribution to the total mobility of the films. In that experiment [2], the steady-state effective viscosity qeff.o was established within 1 h at 150 °C for M = 44 to 393 kg/mol. We notice from Fig. 2.7 that this duration is of the same order as the duration of the initial rapid development of the residue film noted above for the same temperature. The fact that the steady-state effective viscosity is established... 

The presence and the thickness of irreversibly adsorbed layer were studied according to a procedure defined by Guiselin [5]. A spin coated polymer film is washed for several minutes in the same solvent used for the initial solution so that the non-adsorbed chains are removed and only those irreversibly adsorbed remain on the substrate. The thickness of the residual layer was measured via the analysis of AFM tapping mode images performed with the same instrument as for LDS measurements. 

Here, we found that the thickness of the residual layer is about 0.5 Rg for the used molecular weight of PVAc (Rg = 12 nm), but there is evidence that these values refer to adsorbed layers that are not yet at the equilibrium state. The presence of irreversibly adsorbed layer on hard surfaces was already observed for polystyrene films supported on Si and hydrogen-passivated Si substrates after a long annealing time at Tg + 50 K [63]. In these two cases the thickness of the residual layer after long annealing was 0.5 Rg and 0.8 Rg, where the latter value was... 

Sample Preparation. Samples for mechanical studies were made by compression molding the polymers at 150°C between Teflon sheets for 15 minutes followed by rapid quenching to room temperature in air. These will be referred to as PQ (press-quenched or simply quenched) samples. The thickness of the PQ samples was around 10 mils (0.25 mm). The thermal history of all of the PQ samples (HBIB, HIBI, and LDPE) were essentially the same. They were used within one week after they were pressed. Samples for morphology, SALS and SEM studies were prepared from toluene solutions. These films were cast on a Teflon sheet at 80 C from a 1% (by weight) solution in toluene. These films were about 5 mils in thickness. When the polymer films had solidified (after 5 hrs), they were stored in a vacuum oven at 80°C for two days to remove residual solvent. These samples will be designated by TOL (solution cast from toluene). 

Ti incorporation was also found to be a function of the background (residual) pressure in the GFC. Table I lists Ti incorporations for 3 different m-cresol novolac polymers that were treated with TiCLt f°r 1 min. after evacuation of the reaction cell to 110 and 220 mtorr. The polymers that were treated at 220 mtorr had 1.5 times more Ti than those treated at 110 mtorr. Similar experiments conducted with HB-HPR 206 films show a linear relationship between the residual pressure in the GFC and thickness of the resulting Ti02 layer. 

Figure 5a is a p ttern in a film cured for 1 hour at 100°C and exposed at 2yC/cm, the residual film thickness being about a third of a micron. Figure 5b is the same film after being heated for 20 minutes at 175 C and the edge detail appears to be unchanged after this treatment. Figures 6a and 6b are patterns in a PMMA film which is also one third of a micron thick after development and has been heated in the same way (Figure 6b). The flow of the polymer film is much more extensive and has destroyed all the detail in the pattern edges.

In our first experiments, we had to find the size gf collagen peptide most amenable to the Quadrol program. The upper limit of the size of a peptide is determined by the amount of peptide that can be introduced into the spinning cup. Thickness of the film resulting from application of more than 10 mg of protein will interfere with the procedures of dissolving, reaction, extraction, and drying. However, the degradation should be started with approximately 300 nM of protein in order that the reaction can be extended to 40—60 identifiable residues. 

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