Utilization of P-NIPAM polymeric brushes in the development of thermo-responsive catalytic systems: A study of the effects of self-regulating polymers on molecular transport and reaction kinetics

This thesis presents a proof of concept of self-regulating mechanism by a heterogeneous catalyst in combination with stimuli responsive polymer. These polymers have the unique ability to reversibly change conformation from a swollen to a collapsed state in response to an environmental stimulus (e.g. temperature or pH). The conformation change of the
polymer could allow to locally adjust the molecular diffusion of reactants, thereby changing the catalytic activity autonomously. Since the reaction will be intrinsically manipulated, implementing this concept to industrial processes will potentially alleviate the need for using external measures to control the reaction rate, such as passive cooling or using inert dilutants.

Thus far, the self-regulating mechanism using stimuli responsive polymers has never been demonstrated for heterogeneous catalysis. Instead, an external stimulus is applied to alter the catalyst activity depending on the polymer conformational state when polymeric brushes are coated on a nano cluster. In the presence of a thermo-responsive polymer, such as poly(n-isopropylacrylamide) (p-NIPAM), the increase of temperature causes the polymeric brushes to collapse after surpassing a certain temperature, the so called Lower Critical Solution Temperature (LCST). Consequently, the change in conformation resulted in a decrease on the reaction rate, due to the partial blockage of the diffusion path of the reactants. These idealized systems demonstrate that thermo-responsive materials can be used to control molecular transport of reactants. However, there is still a significant research gap concerning the development of more practical catalysts that can have this stimulus-responsive behaviour under industrially relevant condition.