Thermo-responsive release of rhodamine B in the pore-selective poly(N-isopropylacrylamide) immobilized honeycomb-patterned porous film

A new type of thermo-responsive polymer film is fabricated by the immobilization of poly(N-isopropylacrylamide) (PNIPAAm) to the pore-selectively carboxyl group functionalized honeycomb-patterned porous polystyrene film. To check the smartness of the film to the temperature change, the thermo-responsive release of rhodamine B (RB) above the lower critical solution temperature (LCST) (similar to 32.5 degrees C) of the PNIPAAm was studied together with the change in morphology of the pore surface by the scanning electron microscopy (SEM). The thermo-responsive release was monitored by the UV-vis absorbance at a fixed wavelength of lambda(max) of RB similar to 553 nm. The absorbance of lambda(max) in the equilibrium state significantly increased with the increase in temperature above the LCST of PNIPAAm. The result of the SEM image showed a higher rugged surface morphology with a temperature above the LCST which indicates that the change in the pore surface from the coil to globule state supports the thermo-responsive swell and de-swelling state of PNIPAAm. Temperature-dependent RB release kinetics was performed at 25-40 degrees C. The result showed pseudo-first-order kinetics by the Korsmeyer-Peppas model. The transport exponent (n) is higher than 1 as similar to 6.66 above the LCST region which is indicating the temperature responsive release by the change in PNIPAAm morphology. [GRAPHICS] .