Local Disorder Facilitates Chain Stretching in Crowded Polymer Brushes

Abstract

Intermolecular crowding of densely tethered polymers promotes chain extension and anisotropy that induces many unique properties. In this study, we used conformation-sensitive infrared spectroscopy to determine that chain extension in a polymer brush is associated with local conformation rearrangements, i.e., contraction of side groups and increased proportion of gauche twists in the backbone, which served to increase molecular disorder at or below the segmental scale. This conformational transition points to a particular molecular mechanism for chain extension in densely tethered polymers, wherein increased local disorder facilitates global chain ordering (i.e., chain extension) and therefore supplements our current understanding of chain orientation at a molecular level.

Ultrastable Glassy Polymer Films with an Ultradense Brush Morphology

“…Infrared reflection absorption spectroscopy spectra (IRRAS) of PS spin-cast films and brushes was performed using a KSV NIMA system atop a thin gold-layer-covered Si substrate, as previously reported. 57 The incoming IR beam with an incidence angle of 76°interacted with the film and brushes at the substrate surface. The reflected beam was then guided into a detector to obtain the IR spectra.…”

Polymer Adsorbed Layer Promotes Dipole Ordering in Gate Dielectrics for Organic Field-Effect Transistors

“…As can be seen in Figure a, the adsorption bands in the two regions of 1400–1500 and 1100–1300 cm –1 exhibit notable changes depending on the adsorption time. The intensity variation of the former region is related to the bond orientation or bond rotation mobility rather than the conformational state, according to previous studies. − For the region of 1100–1300 cm –1 , on the contrary, the intensity variation of peaks is closely related to the conformational changes in the adsorbed PMMA chains. − To gain more insights into this spectral region, the complex band at 1100–1300 cm –1 was resolved into five elementary component bands by the Lorentzian curve fitting in the manner of previous studies. , The fitting details of the peaks are shown in the Supporti ng Inf ormatio n, and the relevant parameters are summarized in Table S2. These five elementary component bands are designated as ν 1 , ν 2 , ν 3 , ν 4 , and ν 5 according to diminishing frequency (as shown in Figures b–d and S2).…”

“…52−54 To gain more insights into this spectral region, the complex band at 1100−1300 cm −1 was resolved into five elementary component bands by the Lorentzian curve fitting in the manner of previous studies. 52,53 The fitting details of the peaks are shown in the Supporting Information, and the relevant parameters are summarized in Table S2. These five elementary component bands are designated as ν 1 , ν 2 , ν 3 , ν 4 , and ν 5 according to diminishing frequency (as shown in Figures 2b−d and S2).…”

Relaxations of Entropically Stressed Polymer Glasses

“…This evaluation is based on the principle that different rotational positions of the chemical groups, which correspond to the various conformational states, yield different force constants and hence different IR bands. − The backbone and side-group motion were thus detected by measuring the intensity changes of the conformation-sensitive IR bands. Infrared reflection absorption spectroscopy (IRRAS) was used to collect the IR spectra of the films.…”