In situ particle film ATR FTIR spectroscopy of poly (N-isopropyl acrylamide) (PNIPAM) adsorption onto talc

Abstract

The adsorption of poly(N-isopropyl acrylamide) (PNIPAM) onto talc from aqueous solutions has been studied using the in situ methodology of particle film attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy. PNIPAM was observed to adsorb significantly onto the talc particle film at a temperature below its lower critical solution temperature (LCST). Peak shifts were seen in the adsorbed layer FTIR spectrum that match those observed when PNIPAM solution is heated above its LCST. This observation indicates that adsorption causes a conformational re-arrangement similar to that seen when PNIPAM undergoes a coil-to-globule transition, in this case presumably induced by hydrophobic interactions between PNIPAM and the talc basal plane surface. The kinetics of adsorption are seen to be complex, with potential influences of conformational rearrangement and differential adsorption kinetics for the two dominant surface regions of talc particles. The adsorbed PNIPAM was seen to be exceptionally resistant to removal, with no desorption occurring when a background electrolyte solution was flowed over the adsorbed layer. Spectra acquired of the adsorbed polymer layer heated above the LCST reveal that a further conformational rearrangement takes place for the adsorbed layer, finalizing the transition from coil-to-globule that was initiated by the interaction with the mineral surface.

Synthesis of silver nanoparticles using aqueous extracts of Pterodon emarginatus leaves collected in the summer and winter seasons

“…So, in the extract of the leaves collected in the summer season, prominent peaks were observed in the region of 1626 and 1057 cm −1 , while in the winter extract, the peaks were in the region of 1628 and 1072 cm −1 . The presence of peaks in the regions of 1626 and 1628 cm-1 can be attributed to the vibrations of the bonds of the amide functional group I [22,23] or the carbonyl groups (1620-1636 cm −1 ), probably polyphenols [24], while peaks 1057 and 1072 cm −1 indicate C-O-type bonds, such as esters, ethers, alcohols or carboxylic acid [25].…”

A Temperature‐Responsive Boronate Core Cross‐Linked Star (CCS) Polymer for Fast and Highly Efficient Enrichment of Glycoproteins

“…After the further polymerization with NIPAM, St, and Bis, the obtained P(AAPBA‐AM@NIPAM‐St) CSS polymer showed new peaks at about 2880 and 2980 cm −1 , which is assigned to isopropyl CH 3 symmetric and asymmetric stretch, respectively. In addition, the C–H deformation region has peaks at about 1460 cm −1 (asymmetric deformation of isopropyl CH 3 ), 1385, and 1368 cm −1 (both symmetric deformation of isopropyl CH 3 ) . The above results indicate the introduction of isopropyl groups in the CCS polymer and the successful incorporation of NIPAM moieties.…”

Xylan-Modified-Based Hydrogels with Temperature/pH Dual Sensitivity and Controllable Drug Delivery Behavior

“…The bands at 1736 and 1170 cm −1 are assigned to carbonyl stretching vibrations of C=O in anhydride groups and the C–O vibration in MAH, respectively [19], indicating the successful attachment of MAH onto xylan [23,26]. In the spectrum of gel-3, the bonds at 1635 cm −1 and 1560 cm −1 are assigned to stretching vibration of –N–H in NIPAm [24,38,39,40]. The bonds at 1452 cm −1 and 1382 cm −1 are assigned to the asymmetric absorption peak of COO − and bending vibration of C–H originating from AA, respectively [41].…”