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Salt-Mediated Tuning of the Cononsolvency Response Behavior of PNIPMAM Thin Films

Year: 2024

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide The development of tuning parameters to influence the response behavior of polymer-based nanodevices is investigated by the addition of NaClO 4 or Mg(ClO 4 ) 2 to adjust the swelling degree of poly( N -isopropylmethacrylamide) thin films under different vapor atmospheres. By leveraging the cononsolvency effect of the polymer in a mixed vapor of water and acetone, a contraction of the preceding water-swollen films is induced. The relation between the macroscopic and the molecular processes is elucidated by static and time-resolved time-of-flight neutron reflectometry, as well as by in situ Fourier transform infrared spectroscopy. It is found that the addition of NaClO 4 strongly enhances the film thickness response for swelling and contraction, which, therefore, allows the tuning of the film toward stronger responses. Mechanistically, D 2 O–amide bonds are formed during swelling and become perturbed upon vapor exchange. Thereby, the D 2 O–amide interactions are reduced continuously, while acetone–amide interactions develop, accompanied by increasing amide–amide interactions during the film contraction.

Source: Macromolecules

DOI: 10.1021/acs.macromol.4c02053