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. 2018 Jun 27;10(7):709.
doi: 10.3390/polym10070709.

In-Situ pH-Sensitive Fibers via the Anchoring of Bromothymol Blue on Cellulose Grafted with Hydroxypropyltriethylamine Groups via Adsorption

Lele Cao  1   2 , Tieqiang Liang  3   4 , Xipeng Zhang  5 , Wenbo Liu  6 , Jian Li  7   8 , Xianxu Zhan  9 , Lijuan Wang  10   11
Affiliations

In-Situ pH-Sensitive Fibers via the Anchoring of Bromothymol Blue on Cellulose Grafted with Hydroxypropyltriethylamine Groups via Adsorption

Lele Cao et al. Polymers (Basel). .

Abstract

In-situ pH-sensitive cellulose fibers (IS-pH-SCF) were prepared by anchoring bromothymol blue (BTB) onto cellulose fibers (CF) modified with hydroxypropyltriethylamine (HPTTL) groups. Fourier transform infrared and X-ray photoelectron spectrum analyses demonstrated that the HPTTL groups were grafted onto the CF. X-ray diffraction proved that cellulose I in the CF transformed into cellulose II after quaternization. Scanning electron microscopy suggested that the quaternized CF (QCF) surface was clean and uniformly ridged. The adsorption of BTB onto QCF was carried out via batch adsorption experiments. A kinetic study illustrated that the adsorption was a spontaneous process and described well by pseudo-second-order, Freundlich and Temkin isotherms. The activation energy for the BTB adsorption onto QCF was 52.89 kJ/mol, which proved that the BTB adsorption onto QCFs was chemically controlled. The pH response demonstrated that the IS-pH-SCF was highly sensitive to pH, with an obvious color change for pH 4 to 8. The release tests showed that BTB was anchored on QCFs and that no BTB was released. IS-pH-SCF has a potential use for indicating pH changes in food.

Keywords: anchoring; bromothymol blue; cationic modification; cellulose fiber; in-situ pH-sensitive.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Structural changes of bromothymol blue in acid and alkaline solutions.
Figure 2
Figure 2
(A) FTIR spectra of CF and QCF; (B) N1s spectrum of QCF; (C) XRD patterns of CF and QCF; (D) SEM photographs of CF ((a) ×500, (b) ×5000) and QCF ((c) ×500, (d) ×5000); and (E) the chemical structure of QCF.
Figure 3
Figure 3
Effects of (a) contact time and (b) QCF dosage on the BTB adsorption onto QCF.
Figure 4
Figure 4
Fitting curves of (a) pseudo-first-order; and (b) pseudo-second-order.
Figure 5
Figure 5
Fitting curves of (a) Langmuir; (b) Freundlich; and (c) Temkin isotherms.
Figure 6
Figure 6
(A) SEM of QCF ((a) ×1000, (b) ×5000)) and IS-pH-SCF ((c) ×1000, (d) ×5000); (B) FTIR spectra of QCF and IS-pH-SCF.
Figure 7
Figure 7
Release tests (a) in distilled water and (b) dropping acid or alkaline solutions.
See this image and copyright information in PMC

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