(a) i) Provide and explain the Sauerbrey relationship at a temperature of 302K. ii) Specify types of multilayer films this relationship does not apply to. (3 marks) (3 marks) (b) Formation of the chitosan (Chi) - polyacrylic acid (PAA) complexes at an ionic strength of 0.15M and a temperature of 25C was studied for two types of PAA of different molecular weights (MW): PAA2 (MW 2kDa ) and PAA20(MW20kDa ). The equilibrium constants for the complex formation () were calculated according to the chemical equation below: Chi0+PAA+3H+Chi(PAA)H32+ i) Provide the equation for the equilibrium constant ( ) of the complex formation. (3 marks) ii) Which complex (Chi-PAA or Chi-PAA A20 ) is more stable? Explain your answer. (3 marks) (c) The in-situ cross-linking of a (poly-L-lysine/hyaluronan), or for short (PLL/HA)7 multilayer film is monitored by quartz crystal microbalance. Figure below shows the evolution of the frequency shifts (f) and the dissipation (D) as a function of time. These changes started to be monitored after the film has been put in contact with the crosslinking agent. The arrows indicate the injection of the crosslinking agent. Explain the observed changes in f and D after injection of the crosslinking agent. (6 marks) (d) Give two examples how one can make a polyelectrolyte multilayer film stiffer? (3 marks) (e) i) Give the definition of the transition point for the growth of a multilayer film and explain why this occurs? (5 marks) ii) How does the salt concentration and temperature affect the position of the transition point? Explain your answer. (4 marks) Continued overleaf