2015/11/23 by Siddhartha Varma, Varma, Siddhartha, Lionel Bureau +3 · 1 citation
Biochemistry, Genetics and Molecular Biology · Engineering · Materials Science · Physics and Astronomy · #Advanced Materials and Mechanics #FOS: Physical sciences #Hydrogels: synthesis, properties, applications #Polymer Surface Interaction Studies #Soft Condensed Matter (cond-mat.soft) #cond-mat.soft
paper · pdf · doi:10.48550/arxiv.1511.07391
Revised version. To appear in Langmuir (in press)
openalex publication_date 2015/11/23 · arxiv created 2016/03/24 · arxiv updated 2016/03/25 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We describe a microscope-based optical setup that allows us to perform space-and time-resolved measurements of the spectral reflectance of transparent substrates coated with ultrathin films. This technique is applied to investigate the behavior in water of thermosensitive polymer brushes made of poly(N-isopropylacrylamide) grafted on glass. We show that spectral reflectance measurements yield quantitative information about the conformation and axial structure of the brushes as a function of temperature. We study how molecular parameters (grafting density, chain length) affect the hydra-tion state of a brush, and provide one of the few experimental evidence for the occurrence of vertical phase separation in the vicinity of the lower critical solution temperature of the polymer. The origin of the hysteretic behavior of poly(N-isopropylacrylamide) brushes upon cycling the temperature is also clarified. We thus demonstrate that our optical technique allows for in-depth characterization of stimuli-responsive polymer layers, which is crucial for the rational design of smart polymer coatings in actuation, gating or sensing applications.