Features of ultra thin poly(N-isopropylacrylamide) grafted onto glass cover slips

Ultra thin temperature responsive polymer, poly(N-isopropylacrylamide) (PIPAAm) grafted layer exhibits cell attachment and detachment properties in response to temperature change. Such properties are dependent on thickness and amount of the grafted PIPAAm, and are observed for extremely ultra thin thickness (for example, 20 nm thickness for tissue culture poly styrene and 5 nm for glass cover slips). Although this phenomenon was not demonstrated clearly, we have proposed a mechanism. Namely, thinner PIPAAm layer are subjected to dehydration of the PIPAAm chains in the vicinity of basal surfaces. The dehydration progressively promotes dehydration of the grafted PIPAAm chains toward to the outermost regions. In this presentation, we tried to demonstrate the proposed mechanism by investigating the dynamic alternation of thickness of PIPAAm layer in response to temperature. The alternation was measured undere aqueous conditions above and below LCST, using AFM. As a result, thickness of thinner PIPAAm layer was not altered between under atmospheric and aqueous conditions, while thicker layer was done. This difference strongly support the proposed mechanism.