Patterned and switchable surfaces for biomaterial applications

Andrew Hook – Patterned and switchable surfaces for biomaterial applicationsTo further characterise the chemical functionality of the plasma polymer films,ALAPP films were analysed by FT-IR. A typical spectrum for an ALAPP filmdeposited on a KBr disk is shown in Figure 2.5. The large width of adsorption bandsis characteristic of the highly cross-linked plasma polymer [183]. An assignment ofpeaks is given in Table 2.3. Of significance are the large amine signals observed at1100 cm -1 and 3040-3500 cm -1 whilst the minimal imide and amide signal seen at1550-1750 cm -1 and the absence of a nitrile signal at 2100 cm -1 , suggesting that thenitrogen present with the ALAPP is predominantly in an amine form. However,conclusive quantitative results for FT-IR results are difficult due to the uncertainty ofabsorbance coefficients, thus, although FT-IR does further confirm the presence ofamine functionality, it does not conclusively show the extent to which imine andamide functionalities can be found on the ALAPP film. A much lower imine, amideand nitrile signal is reported compared to previously reported studies [180, 185, 186].Significant differences between the present procedure and previously usedprocedures include an alteration in the radio-frequency used to generate the plasma,200 kHz as compared with 13.56 MHz, and a much lower input power of 20 W ascompared with 200 W. This may result in less fragmentation of the monomer and agreater preservation of functional groups as well as the reduced production ofreactive species that can result in post-deposition alterations to the film.2-79