AVS 52nd International Symposium
    Biomaterial Interfaces Tuesday Sessions
       Session BI2-TuA

Paper BI2-TuA4
Pulsed RF Plasma Polymerisation of N-isopropylacrylamide (NIPAAm)

Tuesday, November 1, 2005, 3:00 pm, Room 312

Session: Surface Modification
Presenter: R. Talib, University of Sheffield, UK
Authors: R. Talib, University of Sheffield, UK
A.G. Shard, University of Sheffield, UK
S.L. McArthur, University of Sheffield, UK
Correspondent: Click to Email
There is a growing interest in the development of responsive polymer coatings for applications as diverse as tissue engineering and microfluidic devices. Plasma polymerization affords a convenient, one step route to generate such coatings. Previous studies have shown that continuous wave (CW) plasma polymerization of N-isopropylacrylamide (NIPAAm) is able to produce thermally responsive coatings on a variety of substrates. These CW studies have demonstrated that control of the deposition power and temperature is critical for the retention of functionality, but that too little power or too lower temperature will result in unstable coatings. In this study we investigate the use of pulsed power cycles as a means for both improving coating stability and controlling the thermal response of the coatings. We have investigated the influence of power, on- and off-times and reactor temperature on the coating chemistry, stability and thermal response. The role of the plasma parameters has been monitored using a capacitive probe. The probe enables accurate measurement of the duty cycle and clearly demonstrates that in certain regimes both the power and ratio of on/off time set by the pulse generator can result in significant delays in the striking of the plasma. In some instances, we demonstrate that the plasma actually fails to ignite during the majority of individual pulses. Accurate measurement of duty cycles enables direct comparison of coatings produced under pulsed power with those produces with equivalent CW powers. X-ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS) and captive bubble have been used to measure the resulting coating properties and compare the mechanisms of NIPAAm polymerization under CW and pulsed plasma conditions.