Homogeneous cellulose thin films by regeneration of cellulose xanthate: properties and characterization

Abstract

The preparation and characterization of cellulose thin films derived from cellulose xanthate is reported. The films are prepared by depositing alkaline aqueous solutions of cellulose xanthate onto silicon wafers, followed by a spin coating step. Depending on the xanthate concentration used for spin coating, films with 50 and 700 nm thickness are obtained. The cellulose xanthate is converted to cellulose by exposing the films to HCl vapors over a period of 20 min. The conversion is monitored by ATR-IR spectroscopy, which allows for tracking the rupture of C-S and C=S bonds during the regeneration process. The conversion is accompanied by a reduction of the film thickness of ca 40% due to the removal of the bulky xanthate group. The films feature a homogenous, but porous morphology as shown by atomic force microscopy. Further, the films were investigated towards their interaction with Bovine Serum Albumin (BSA) and fibrinogen by means of multi-parameter surface plasmon resonance spectroscopy. Similar as other cellulose thin films BSA adsorption is low while fibrinogen adsorbs to some extent at physiological pH (7.4).

Cellulose carbamate derived cellulose thin films: preparation, characterization and blending with cellulose xanthate

“…The slight variations in the SFE values are caused by the changes in the surface roughness of the films since the chemistry of the films is the same. Such deviations in SFEs were also observed for cellulose thin films Scheme 1 Carbamate decomposition induced by the increasing basicity of the system during ongoing spin coating derived from other precursors (Mohan et al 2011;Weißl et al 2018Weißl et al , 2019.…”

“…Strong overlapping bands at 1480, 1420 and 880 cm -1 are characteristic for sodium carbonate and clearly dominate the spectrum, whereas bands caused by cellulose and sodium hydroxide are (Neufeld et al 2002). The intensive sodium carbonate band and the described growth of a crystalline structures after spin coating suggest the expected formation of a sodium carbonate top layer (Weißl et al 2018). After rinsing the substrates, a spectrum matching all the cellulose bands as described by Siroky et al was obtained (Š iroký et al 2010).…”

“…AFM was employed to gain further information about the surface morphology and structure of the CC films. Compared to cellulose thin films from different sources like trimethylsilyl cellulose (TMSC) (Niegelhell et al 2016;Schaub et al 1993) or cellulose xanthate (CX) (Weißl et al 2018), the surface of CC thin films features more aggregates (10-13 nm) concomitant with slightly higher roughness. The AFM images (Fig.…”

“…The slides used as substrates for the films were cleaned by dipping them into piranha acid (H 2 SO 4 :H 2 O 2 = 3:1 (v/ v)) for 30 min (10 min for gold slides) followed by intense rinsing with MilliQ water in advance. The spin coating itself was performed on a Polos Spin 150i (from SPS Europe, Ingolstadt, Germany) with a speed of 4000 rpm and an acceleration of 2500 rpm/s for 60 s as already described in previous work (Weißl et al 2018(Weißl et al , 2019. After spin coating, the films were stored for at least 1 h under ambient conditions before they were rinsed with 10 ml water and dried under nitrogen flow.…”

“…Literature gives many examples, where thin films have been employed to study the influence of certain conditions on the behavior of cellulose and its derivatives, or to observe the interaction of cellulose with biopolymers or proteins (Ehmann et al 2015;Mohan et al 2017;Niegelhell et al 2016;Niinivaara et al 2016). In a previous work, some of us published a method for the processing of cellulose thin films based on the spin coating and following HCl vapor exposure of CX films (Weißl et al 2018). This made us interested in the fundamental suitability of CC solutions to form thin film structures.…”