8.2 Solvent-Induced Surface Reorientation of PS-b-PtBA Films
151
by XPS (surface coverage χ(PtBA) ~ 0.60, see Chap. 3). Similarly, the hydrolysis
kinetics (see also Chap. 3) were in favorable agreement with the interpretation that in
the cyclohexane-treated films both blocks are exposed at the surface and that PtBA
is located inside the nanodomains seen in Fig. 8.2.
8.3 Domain-Selective Coupling on Solvent-Treated
Polymer Films
The results of Sect. 8.2 indicate that PtBA is exposed in the form of isolated islands
(nanodomains) in a matrix of chemically inert PS. This film morphology would
imply that it is in principle possible to perform surface chemical reactions inside
these domains.
8.3.1 Global Characterization of Domain-Selective Coupling
Domain-selective hydrolysis reactions of PS 690 -b-PtBA 1210 films have been already
characterized on a global level by using infrared spectroscopy and contact angle
measurements (Chaps. 3 and 5). Here we will focus on the domain-selective
coupling of amino-functionalized molecules to hydrolyzed and subsequently NHS
ester-activated PS 690 -b-PtBA 1210 films.
PS 690 -b-PtBA 1210 polymer films were first hydrolyzed using trifluoroacetic acid
and then activated with NHS/EDC. After coupling of fluoresceinamine, fluorescence
microscopy was used to assess the coverage of fluorescent adsorbate. As shown in
Fig. 8.3, the neat film exhibited more intense fluorescence emission compared to the
solvent-treated film. From the corresponding intensity histograms, it can be seen that
the fluorescence emission intensity of the solvent-treated film is lower by a factor of
3/5 compared to the neat block copolymer films. This result is in good agreement
with the surface coverages assessed based on XPS investigations (Chap. 3), as well
as the AFM data shown above. The surface coverages do not appear to have changed
significantly during the wet chemical derivatization reactions.
However, these results should not be over-interpreted as there may be several
factors that could cancel each other, such as film restructuring (leading to increased
exposed surface areas) vs. incomplete chemical derivatization reactions (activation
with NHS and/or fluoresceinamine coupling). In addition, due to lack of spatial
resolution of the methods applied, little is known about the homogeneity of the
reactions on the length scale defined by the dimensions of the domains.
151
by XPS (surface coverage χ(PtBA) ~ 0.60, see Chap. 3). Similarly, the hydrolysis
kinetics (see also Chap. 3) were in favorable agreement with the interpretation that in
the cyclohexane-treated films both blocks are exposed at the surface and that PtBA
is located inside the nanodomains seen in Fig. 8.2.
8.3 Domain-Selective Coupling on Solvent-Treated
Polymer Films
The results of Sect. 8.2 indicate that PtBA is exposed in the form of isolated islands
(nanodomains) in a matrix of chemically inert PS. This film morphology would
imply that it is in principle possible to perform surface chemical reactions inside
these domains.
8.3.1 Global Characterization of Domain-Selective Coupling
Domain-selective hydrolysis reactions of PS 690 -b-PtBA 1210 films have been already
characterized on a global level by using infrared spectroscopy and contact angle
measurements (Chaps. 3 and 5). Here we will focus on the domain-selective
coupling of amino-functionalized molecules to hydrolyzed and subsequently NHS
ester-activated PS 690 -b-PtBA 1210 films.
PS 690 -b-PtBA 1210 polymer films were first hydrolyzed using trifluoroacetic acid
and then activated with NHS/EDC. After coupling of fluoresceinamine, fluorescence
microscopy was used to assess the coverage of fluorescent adsorbate. As shown in
Fig. 8.3, the neat film exhibited more intense fluorescence emission compared to the
solvent-treated film. From the corresponding intensity histograms, it can be seen that
the fluorescence emission intensity of the solvent-treated film is lower by a factor of
3/5 compared to the neat block copolymer films. This result is in good agreement
with the surface coverages assessed based on XPS investigations (Chap. 3), as well
as the AFM data shown above. The surface coverages do not appear to have changed
significantly during the wet chemical derivatization reactions.
However, these results should not be over-interpreted as there may be several
factors that could cancel each other, such as film restructuring (leading to increased
exposed surface areas) vs. incomplete chemical derivatization reactions (activation
with NHS and/or fluoresceinamine coupling). In addition, due to lack of spatial
resolution of the methods applied, little is known about the homogeneity of the
reactions on the length scale defined by the dimensions of the domains.