3.2 Ultrathin PNHSMA Polymer Films
49
Fig. 3.3 a Transmission FTIR spectra of films of PNHSMA on SiO 2 following hydrolysis at 21 °C
for the indicated reaction time; b integrated absorbance for succinimide carbonyl band (ν (C = O),
1737 cm −1 ) normalized to the absorbance of the C–O stretching vibration (ν (C–O), 1205 cm −1 )
Fig. 3.4 a Comparison of the early stages of the hydrolysis as probed by CA measurements and
FTIR spectroscopy at 21 °C. The coverage of NHS groups was calculated from the CA data by
applying the Cassie equation [17]: cosθ exp = χ NHS cosθ NHS + χ COOH cosθ COOH where χ NHS and
χ COOH are the surface coverages of the two components and θ NHS and θ COOH are 60° and 35°,
respectively. b Linearization of the kinetic data shown in Fig. 3.4a for short reaction times according
to pseudo-first-order kinetics. The solid lines correspond to linear least squares fits of the IR and
CA data, respectively
in part by the presence of deprotonated carboxyl groups in the surface region of the
film that may repel diffusing hydroxide ions.
The course of the reaction can be quantified by analyzing the changes in
absorbance of the succinimidyl carbonyl band. The absence of possible carboxylate was confirmed in the region of 1540–1560 cm
−1 , and the presence of
dimeric carboxylic acids (1704 cm
−1 ) is not pronounced [15]. The absorbance
of monomeric acid (1710–1720 cm
−1 ), as measured in addition to the mentioned
dimeric carboxylic acids (1704 cm
−1 ) in independent IR experiments on spincoated films of poly(methacrylic acid), would overlap partially with the succinimidyl
49
Fig. 3.3 a Transmission FTIR spectra of films of PNHSMA on SiO 2 following hydrolysis at 21 °C
for the indicated reaction time; b integrated absorbance for succinimide carbonyl band (ν (C = O),
1737 cm −1 ) normalized to the absorbance of the C–O stretching vibration (ν (C–O), 1205 cm −1 )
Fig. 3.4 a Comparison of the early stages of the hydrolysis as probed by CA measurements and
FTIR spectroscopy at 21 °C. The coverage of NHS groups was calculated from the CA data by
applying the Cassie equation [17]: cosθ exp = χ NHS cosθ NHS + χ COOH cosθ COOH where χ NHS and
χ COOH are the surface coverages of the two components and θ NHS and θ COOH are 60° and 35°,
respectively. b Linearization of the kinetic data shown in Fig. 3.4a for short reaction times according
to pseudo-first-order kinetics. The solid lines correspond to linear least squares fits of the IR and
CA data, respectively
in part by the presence of deprotonated carboxyl groups in the surface region of the
film that may repel diffusing hydroxide ions.
The course of the reaction can be quantified by analyzing the changes in
absorbance of the succinimidyl carbonyl band. The absence of possible carboxylate was confirmed in the region of 1540–1560 cm
−1 , and the presence of
dimeric carboxylic acids (1704 cm
−1 ) is not pronounced [15]. The absorbance
of monomeric acid (1710–1720 cm
−1 ), as measured in addition to the mentioned
dimeric carboxylic acids (1704 cm
−1 ) in independent IR experiments on spincoated films of poly(methacrylic acid), would overlap partially with the succinimidyl