Effect of controlled drying on the properties of cellulose ester films synthesized in Novel Ionic Liquid [mTBNH][OAc]

doi:10.21203/rs.3.rs-4801036/v1

Download PDF

Research Article

Effect of controlled drying on the properties of cellulose ester films synthesized in Novel Ionic Liquid [mTBNH][OAc]

https://doi.org/10.21203/rs.3.rs-4801036/v1

This work is licensed under a CC BY 4.0 License

You are reading this latest preprint version

Cellulose, as a sustainable raw material, holds a promising future as a thermoplastic material. This work focused on fabricating cellulose ester thin films by using both controlled vacuum oven drying and conventional oven drying by the evaporation induced phase separation method (EIPS). A novel distillable ionic liquid (IL) 5-Methyl-1,5,7-triaza-bicyclo- [4.3.0]non-6-enium acetate [mTBNH][OAc]with high dissolving capability of cellulose along with dimethylsulfoxide (DMSO) as a co-solvent are used. The drying methods were compared to investigate their influence on the Cellulose ester films morphological and wettability properties. Based on the results, with increasing the drying rate in the vacuum oven the films have a smoother surface (with CP having 2.14nm RMS value) than the other samples, also indicating higher contact angles of 124 for CP under vacuum drying conditions with denser films.

solvent casting

vacuum drying

[mTBNH][OAc]

cellulose esters

polymer films

EIPS

Bioplastics are gaining world-wide interest for their numerous applications. Bio-based plastics are typically generated from renewable sources by the action of living organisms, they can be polysaccharides (e.g., regenerated cellulose; pectin, and chitin), lipids etc. (e.g., animal fats) (Bhaladhare and Das 2022). The use of plant-based cellulose could be the key, as cellulose is the most abundant biopolymer formed in nature with high chain stiffness, broad chemical modifying capacity and polyfunctionality (Liu et al. 2021). Cellulose intrinsically is not a thermoplastic, but with chemical modification desired properties can be achieved. The Hyatt manufacturing company in 1870 demonstrated chemical modification of cellulose on an industrial scale (Balser et al. 2004). Chemical modification aims to functionalise and improve processability of cellulose and cellulose esters (CE) are the most popular derivatives of cellulose (Oprea and Voicu 2020)...

Crystallinity of cellulose is an important factor as cellulose is hydrophilic due to the presence of hydroxyl groups and does not actually dissolve in water (Kontturi et al. 2006). Whereas the amorphous cellulose swells up in water since water can penetrate by disrupting the intermolecular hydrogen bonds (Müller et al. 2000). Cellulose derivatives have been investigated extensively to develop new materials with improved chemical, thermal and physical characteristics (Shaghaleh et al. 2018). The esterification of long chain fatty acid cellulose esters is processed in two methods homogeneous and heterogeneous, the conventional method for industrially cellulose esters production is mainly heterogeneous conditions with sulphuric acid acting as catalyst (Hummel 2004) (6). The heterogeneous method of cellulose esters production is laborious and time consuming, as the degradation of cellulose is always present along with the low reactivity of cellulose due to its high crystallinity. Conversely, homogeneous transesterification of cellulose creates possibility to synthesis cellulose esters with a high degree of substitution (DS) and long acyl chains. The film preparation from solvent cast method of cellulose acetate (CA) is a simple method (Yang et al. 2013), the procedure of solvent casting consists of pouring of the solution on to a substrate which is followed by controlled complete or partial evaporation (Lyytikäinen et al. 2021). However, the influence of environmental variables during drying (temperature, pressure etc.) on the film properties have been rarely described from the literature. Recently, (Lyytikäinen et al. 2021) have shown drying temperature influence on the film wetting and barrier properties, affecting the morphology of the films and consequently the barriers properties. Harini and Sukumar (Harini and Sukumar 2019) compared vacuum drying to open air drying for CA films on Petri dishes and found transparent films dried under vacuum and white films formed under open air drying.

The above-mentioned literature pursues the influence of the environment on drying which in turn affect the properties of the film. Vacuum drying is a method that is used to study and compare the results to a conventional oven drying. The sample surface has been studied along with the cross-sectional structure formation. The vacuum drying method should have better film formation with smoother surface that could lead to the film having better hydrophobicity. This study includes the analysis of sample surface topology and the formation of microstructure in the cross section of the films.

In this study, we present the physical characterization (FTIR), morphology (SEM), and thermal properties (TGA) of long-chain cellulose ester films prepared by controlled drying solvent casting technique.

2.1. Materials

The fibrous cellulose was purchased from Carl Roth GMBH (Karlsruhe, Germany). Vinyl laurate and vinyl palmitate with purity > 98% was purchased from Tokyo chemical Industry Co. (Tokyo, Japan). Ionic liquid 5-Methyl-1,5,7-triaza-bicyclo-[4.3.0]non-6-enium acetate [mTBNH][OAC] was not commercially available and was synthesized by Liuotin Group Oy (Porvoo, Finland). The melting point of IL is 15°C; the flash point is more than 220°C. DMSO with a purity of 99.9% was purchased from Fisher Chemical (Pittsburgh, PA, USA). Diethyl phthalate plasticized (24% DEP) cellulose powder supplied by Sigma Aldrich. Pyridine with purity more than 99% purchased from Sigma Adrich

2.2. Cellulose dissolution in the solvent system

Cellulose was dried under vacuum at 105°C for 24 hours before use. 3.5 g of MCC was dissolved in 100 g [mTBNH][OAc] and stirred at 60°C for several hours until the cellulose was completely dissolved to yield 3.5 wt.% solution. To decrease the viscosity which simplifies the processing, a co-solvent DMSO was added in ratio 1:1 to IL. The designed amount of the respective vinyl ester (3 eq./AGU) was added to the cellulose solution in a chemical reactor equipped with a mechanical stirrer and nitrogen flow, and then the reaction was performed at temperature 70°C and reaction time was 3 hours. When the reaction was completed, the obtained cellulose esters were precipitated into 500 ml of water mixed with ethanol (for laurate and myristate) or pure ethanol (for palmitate and stearate). To remove solvent and vinyl ester residuals, the product was washed several times in 100–200 ml of ethanol, next acetone, and finally with hexane. After that the product was dried under a vacuum at 55°C overnight (Table 1), the method of preparation was conducted similarly to our previous paper. (Tarasova et al. 2023).

Table 1

Synthesis parameters for the polymer solution.
Nr	Derivative name	Ester	Sample
1	Cellulose acetate - commercial (C2)	Acetate	CDA
2	Cellulose laurate (C12)	Laurate	CL
3	Cellulose palmitate (C16)	Palmitate	CP

2.3. Solvent casting of cellulose films

A knife blade was used to spread the polymer solution over a flat glass substrate of 100 mm width. The cast solutions were placed at 25°C and at negative 0.45 bar in a vacuum oven over night. After removal from the oven the cast thin films were immersed in distilled water, peeled from the substrate, and further dried in the vacuum over at 25°C for 8 hours.

The final film thickness was dictated by the concentration of the polymer in the solution. Films were cast on laminated glass plates with the blade width of 100 mm (BYK-Gardner GmbH, Germany). With the given knife, the casted thickness of 100 µm was set to achieve the final thickness of 60–80 µm (Kramar et al. 2023; Kallakas et al. 2023).

The above prepared solvent matrix is poured on to a glass substrate (100mm width and 100 micrometre thickness) and was kept in an Memmert universal oven (Memmert GmbH + Co. KG, Germany) at 25°C with a vent open to the ambient room atmosphere (at room pressure), for the evaporation of the solvent.

The solvent matrix solution was casted on a glass substrate (100mm width and 100 micrometre thickness) and was kept in a Tefic biotech DZF – 6090 (China) vacuum oven (at 25°C and negative pressure 0.5 bar) for complete evaporation of the solvent. Fig. shows the vacuum drying chamber setup used for the preparation of the films.

2.4 Characterisation

2.4.1 Fourier Transform Infrared (FTIR) Spectroscopy

The FTIR spectroscopy was carried out on native cellulose and synthesized cellulose esters to evaluate the acetylation process. Measurements were performed using a Interspectrum FTIR spectrometer Shimadzu (Tõravere, Estonia) with KBr disc method between 500 and 4000 \(\:{cm}^{-1}\). 32 scans were taken from each sample with a resolution of 4 \(\:{cm}^{-1}\) in absorbance mode. For comparison, spectra were adjusted to the same baseline.

2.4.2 Contact Angle measurement.

The contact angles were measured on Data physiscs OCA-20 (Riverside, CA, USA), the sessile drop method with a room temperature of 22°C with the relative humidity of 65%, the water drop is placed on the film surface from a micro syringe (Hamilton-Bonaduz). Measurements were made with three and averaged, each measurement was made on a new spot. The contact angles were measured for 40 s for each measurement.

2.4.3 X-ray diffraction analysis (XRD).

The structural analysis of the samples in the powder form was assessed from X-ray diffraction (XRD) measurement using the Ultima IV diffractometer (Rigaku, Tokyo, Japan). The instrument was equipped with a silicon detector, Ni filter, and a Cu Kα irradiation source (λ = 1.540 Å), anode voltage 40 kV, anode current 40 mA, θ-θ regime, step θ = 0.02 deg.

2.4.4 Scanning electron microscopy (SEM)

The cellulose ester films, surface microstructure is understood by Thermo Fisher Phenom XL (Massachusetts, USA) desktop scanning electron microscope (tabletop). Each sample was fixed on a stub using a double-sided adhesive tape after being cryo fractured under liquid nitrogen, the samples were placed at an angle of 90°C.

2.4.5 Atomic force microscopy (AFM)

Atomic force micrographs of the ester films were characterised using a Bruker Dimension Edge (Massachusetts, USA) in Tapping mode. The measurements of the samples were taken for the area of 5x5 µm. The roughness average (Ra) and the root mean square (Rq) were calculated to quantitatively estimate the roughness of the films.

2.4.6 Thermogravimetric Analysis (TGA)

A Setaram Labsys Evo 1600 thermoanalyzer (Caluire, France) was used. The DTG-DTA experiments were carried out under non-isothermal conditions up to 600°C at the heating rate of 10°C min^− 1 in the atmosphere of argon. Standard 100 µL alumina crucibles were used, the mass of the samples was 7.2 ± 0.3 mg, and the gas flow was 20 mL min^− 1.

5.1. Fourier Transform Infrared (FTIR) Spectroscopy

The FTIR spectra of the cellulose films exhibits the absorption bands of the characteristic functional groups of cellulose esters that are dried in the conventional oven and vacuum oven were similar which are shown in the Fig. 1. The strongest evidence of successful acylation is the appearance of an absorption band at 1740 cm^–1 that corresponds to the stretching of the ester carbonyl (> C = O) group, and the band at 720 cm^–1 is characteristic for linearly connected –CH2– groups (–(CH2)4– rocking) (Singh et al. 2014). Peaks at 2924 cm^− 1 and 2854 cm^− 1 show the successful introduction of alkyl chains intensities correspond to asymmetric and symmetric stretching of the methylene group of the fatty long chains. The esterification of the cellulose hydroxyl groups is clearly indicated by the decreasing intensity of the wide peak at 3472 cm^− 1 that corresponds to the stretching vibrations of the OH group, indicates that a large amount of –OH groups were substituted (Crépy et al. 2011). Similar results have been obtained for cellulose esters irrespective of the substituent chain length (Kallakas et al. 2023; Tarasova et al. 2023).

5.2 Contact Angle measurement.

The cellulose ester films were characterised by static contact angle measurement to determine the hydrophobic or the hydrophilic nature, reported in the Table 2. The contact angles for the films dried in the conventional oven ranged between 80° to 121° Fig. 2 and for the vacuum oven dried thin films the contact angles ranged between 85° to 124°, depending on the fatty acid chain length and in addition with the influence of the drying condition. The thin films are considered hydrophobic depending on the fact that the contact angles between water and the cellulosic films are at least 90°(Bhaladhare and Das 2022). Hence, the cellulose ester films are deemed to be hydrophobic. However, the higher contact angles are seen in the vacuum dried cellulosic ester thin films. It is known that long aliphatic side chain is hydrophobic, this is justified with high contact angles of cellulose palmitate and cellulose laurate.

Table 2

Average contact angle measurement of cellulose ester films.
Ester	RO (°)	VO (°)
CDA	80 (± 5)	85(± 8)
CL	106(± 2)	113(± 3)
CP	121(± 2)	124(± 3)

5.3. X-ray diffraction analysis (XRD).

The film structure has been characterised by XRD to detect the structure of the cellulose ester films. The X- ray diffraction profile of all the film samples is shown in Fig. 3. All the samples regardless of the drying condition indicate a peak of 2q = 12°- 24°. The intra and intermolecular hydrogen bonds occur in cellulose through hydroxyl groups, which results in various ordered crystalline arrangements (Sheltami et al. 2012). According to Miller indices, peaks around 2q = 16.5° and 22.5° represent (110), and (200) crystallographic planes of cellulose I, respectively (French and Santiago Cintrón 2013). As seen from Fig. 3 the diffractogram indicates two broad peaks for CDA at 9.32°, and 18.72°. Similarly, the peaks at 9.56°, 19.68°, and 28.69° can be seen for the cellulose esters CL and CP. From the data plot we do not notice any significant effect of the drying conditions on the structure of the films. The peak around 20° is ascribed to (002) of the plane, exhibiting characteristic amorphous phase (Li and Renneckar 2011; Fan et al. 2013). The weak peak at 28.69° of (040) and 9.56° at (101) reflection appear in CL and CP. The peak at 20° of (002) is broad in CDA and narrower in CL and CP indicating a higher degree of crystallinity (Montane et al. 1998). The diffraction peaks that appear around 10° in CDA could be indexed to crystalline peaks of CTA II modification (Sun and Sun 2002; Das et al. 2014). The diffraction peak at 20° is more intense and the relative intensity has increased, this observation could reveal a better-defined crystalline domain. Lateral chain order is indicated by the decrease of the peak width (2theta = 16°-24°) as the side chain increased as seen in the wide-angle region of the diffractogram a better-defined crystalline domain.

5.4 Thermogravimetric Analysis (TGA)

The dynamic thermogravimetric curves of cellulose ester films prepared from [mTBNH][OAc] are given below in Fig. 4. The analysis showed thermal decomposition process involving rapid loss of weight and towards the end the decomposition zone where the constant weight represents the carbonization of the material. The initial decomposition temperature at 5% weight loss (\(\:{T}_{5\%}\)) and the maximum weight loss temperature (\(\:{T}_{d}\)), finally the char residue at 600°C are recorded in the following Table 4. (\(\:{T}_{d1}\)) is the initial step of pyrolysis of volatile compounds.

Table 3

Thermal stabilities of the cellulose fatty chain esters.
Sample		T 5% °C	Td1 °C	Td °C	Char %
CDA	RO	263.2	201.1	360.8	12.2
CDA	VO	245.0	210.6	362.0	15.3
CL	RO	212.5	232.0	369.2	7.9
CL	VO	212.7	230.8	367.3	6.3
CP	RO	303.4	-	360.6	2.6
CP	VO	305.0	-	354.4	0.9

The main degradation range between 250–350°C is due to the crystalline phase degradation of cellulose(Sonia and Priya Dasan 2013). The ester groups caused the formation of a specific mass loss in the range between 140–250°C due to decomposition of the alkyl chains grafted to cellulose laurate (CL) and cellulose di acetate (CDA) but the similar trend is absent in case of cellulose palmitate (CP). Mass loss at 5wt% indicates a noticeable difference in the temperature of CDA with the VO dried sample with the mass loss at 245°C compared to the RO sample at 263°C. The cellulose esters CDA and CL two separate degradation steps with initial pyrolysis peak of CL shifted to higher temperature around 230°C compared to CDA at 200°C. The initial pyrolysis peak could be attributed to the degradation of the grafted fatty acid side chains (Jebrane et al. 2017), the higher peak of CL can be attributed to the longer chain length compared to CDA with a shorter chain length. In all the samples the main degradation peak of cellulose backbone is seen around 360°C (Jandura et al. 2000) (Freire et al. 2006; Uschanov et al. 2011). Similar degradation temperatures have been observed in the literature with functionalised celluloses fatty acid chlorides (Almasi et al. 2015).

5.5. Scanning Electron Microscopy (SEM)

SEM has been characterized to study the film formation and structure. The Fig. 5 shows the cross-sectional images of the cellulose ester thin films. From the images, less structures are observed comparing the VO and RO and surfaces indicate dense structure in the film formation. All the sample indicate a top layer which is exposed to the air. The thickness of the films after drying depends on the thickness of the homogeneous solution during casting. The kinetic phase separation during evaporation indicates a polymer lean and a polymer rich phase. The cross-section images reveal that the samples have a homogeneous film composition, and no significant structures are seen in the films prepared which could also be attributed to the long and controlled evaporation times. As the solvent evaporates from the membrane system, the chains lose mobility and adjust to the configurations(Du et al. 2009). Longer evaporation time leads to formation of asymmetric structures with denser layer.

Table 4

Thickness of cross section of films.
Ester		Thickness
Ester		µm
CDA	RO	116
CDA	VO	115.5
CL	RO	59.5
CL	VO	60
CP	RO	57.5
CP	CO	58

5.6. Atomic Force Microscopy (AFM)

The surface morphology and the roughness values of the cellulose ester films are listed in the table 6. The darker areas as observed are associated with depressions on the surface of the films and the lighter areas are the elevations. Surface morphology is characterised by root mean square (Sq), mean roughness (Sa) and the difference between high peaks and low valleys (Z). Observations from the AFM indicated nodular structure, the polymer-rich phase having less ability to deform and thus merge and cause nodular structure due to chain entanglements, while the polymer poor phase become the cavities/depressions(Zhang et al. 2002). These nodules are the influencing factor for the roughness of the surface. The effect of evaporation environment is depicted clearly by comparing the surface images and the surface roughness parameters.

The average depression size concentration is larger over the area of the films dried in the vacuum oven as compared to the films dried in the conventional oven as seen in the CDA, CP and CL films. The membrane surface, that is the nodule size and distribution could be attributed to the evaporation conditions and environment. The literature reports, with the increase with the nodule size, the surface roughness of the membranes tend to increase(Khulbe et al. 1998). The influence of evaporation environment on the surface morphology of the films with average roughness lower and the concentration of the depression area is marginally higher with the vacuum dried samples.

However, no nodular structure is seen on the surface of CL films in both dried in the vacuum and the conventional oven. But in this case surface roughness cannot be in proportion to the nodule size, but the depression and the elevation regions could account for the surface roughness. CL on the other hand has a noticeable difference between the conventional oven dried sample and the vacuum dried sample, film surface indicates accumulated area of elevation and depressions. The regions elevation is significant in the vacuum dried film, the isolated nodules have distinct boundaries, and the interstitial regions can be clearly identified. It could be possible that polymer chains present in the interstitial regions are randomly distributed compared to polymer chains present in the nodules(Khulbe et al. 1998). Although, a couple of samples indicate circular concentration of peaks which attributed to the released air bubbles during the long drying process.

Table 5 AFM surface roughness values of the cellulose fatty chain esters.

Sample	RMS roughness (Sq)(nm)		Mean roughness (Sa)(nm)		Max Z range (nm)
Drying Method	RO	VO	RO	VO	RO	VO
CDA	8.12	6.55	5.83	4.71	76.39	82.40
CL	3.42	5.50	2.32	2.76	43.24	123.24
CP	3.09	2.14	2.30	1.66	31.07	37.19

The method of drying the films under vacuum conditions and conventional oven conditions were found to be promising with increased evaporation rate, higher hydrophobicity. The vacuum drying created smoother surface with better hydrophobicity values and create denser films. These evaporation conditions indicate a blend of lamellar and finger like microstructure for better packing structure during drying. The thermal characterisation implied that cellulose films remain stable with similar degradation temperatures. AFM 3D image depicts the depth of the film morphology in context of the surface roughness. Considering our study, vacuum drying showed potential for making films smoother and denser with increased hydrophobicity.

Ethical Approval

The author declares no competing interests.

Funding

This study was supported by ERDF and the Estonian Research Council via project RESTA 10.

Author Contribution

All authors contributed to the study conception and design. Material preparation, data collection, and analysis were performed by E.T., T.K., P.A., and H.K. The first draft of the manuscript was written by T.K, and all authors commented on previous versions of the manuscript. Literature research, the analysis, idea of the article, and revision was done by J.K., A.K., P.A, E.T., T.K.,R.L.,A.M., and H.K. All authors have read and agreed to the published version of the manuscript.

Almasi H, Ghanbarzadeh B, Dehghannia J, et al (2015) Heterogeneous modification of softwoods cellulose nanofibers with oleic acid: Effect of reaction time and oleic acid concentration. Fibers and Polymers 16:1715–1722. https://doi.org/10.1007/s12221-015-4294-1
Balser K, Hoppe L, Eicher T, et al (2004) Cellulose Esters. In: Ullmann’s Encyclopedia of Industrial Chemistry. Wiley
Bhaladhare S, Das D (2022) Cellulose: a fascinating biopolymer for hydrogel synthesis. J Mater Chem B 10:1923–1945. https://doi.org/10.1039/D1TB02848K
Crépy L, Miri V, Joly N, et al (2011) Effect of side chain length on structure and thermomechanical properties of fully substituted cellulose fatty esters. Carbohydr Polym 83:1812–1820. https://doi.org/10.1016/j.carbpol.2010.10.045
Das AM, Ali AA, Hazarika MP (2014) Synthesis and characterization of cellulose acetate from rice husk: Eco-friendly condition. Carbohydr Polym 112:342–349. https://doi.org/10.1016/j.carbpol.2014.06.006
Du JR, Peldszus S, Huck PM, Feng X (2009) Modification of poly(vinylidene fluoride) ultrafiltration membranes with poly(vinyl alcohol) for fouling control in drinking water treatment. Water Res 43:4559–4568. https://doi.org/10.1016/j.watres.2009.08.008
Fan G, Wang M, Liao C, et al (2013) Isolation of cellulose from rice straw and its conversion into cellulose acetate catalyzed by phosphotungstic acid. Carbohydr Polym 94:71–76. https://doi.org/10.1016/j.carbpol.2013.01.073
Freire CSR, Silvestre AJD, Neto CP, et al (2006) Controlled heterogeneous modification of cellulose fibers with fatty acids: Effect of reaction conditions on the extent of esterification and fiber properties. J Appl Polym Sci 100:1093–1102. https://doi.org/10.1002/app.23454
French AD, Santiago Cintrón M (2013) Cellulose polymorphy, crystallite size, and the Segal Crystallinity Index. Cellulose 20:583–588. https://doi.org/10.1007/s10570-012-9833-y
Harini K, Sukumar M (2019) Development of cellulose-based migratory and nonmigratory active packaging films. Carbohydr Polym 204:202–213. https://doi.org/10.1016/j.carbpol.2018.10.018
Hummel A (2004) 3.2 Industrial processes. Macromol Symp 208:61–80. https://doi.org/10.1002/masy.200450406
Jandura P, Riedl B, Kokta B V. (2000) Thermal degradation behavior of cellulose fibers partially esterified with some long chain organic acids. Polym Degrad Stab 70:387–394. https://doi.org/10.1016/S0141-3910(00)00132-4
Jebrane M, Terziev N, Heinmaa I (2017) Biobased and Sustainable Alternative Route to Long-Chain Cellulose Esters. Biomacromolecules 18:498–504. https://doi.org/10.1021/acs.biomac.6b01584
Kallakas H, Kattamanchi T, Kilumets C, et al (2023) Tensile and Surface Wettability Properties of the Solvent Cast Cellulose Fatty Acid Ester Films. Polymers (Basel) 15:2677. https://doi.org/10.3390/polym15122677
Khulbe KC, Matsuura T, Noh SH (1998) Effect of thickness of the PPO membranes on the surface morphology. J Memb Sci 145:243–251. https://doi.org/10.1016/S0376-7388(98)00083-0
Kontturi E, Tammelin T, Österberg M (2006) Cellulose—model films and the fundamental approach. Chem Soc Rev 35:1287–1304. https://doi.org/10.1039/B601872F
Kramar A, Rodríguez Ortega I, González-Gaitano G, González-Benito J (2023) Solution casting of cellulose acetate films: influence of surface substrate and humidity on wettability, morphology and optical properties. Cellulose 30:2037–2052. https://doi.org/10.1007/s10570-022-05026-2
Li Q, Renneckar S (2011) Supramolecular Structure Characterization of Molecularly Thin Cellulose I Nanoparticles. Biomacromolecules 12:650–659. https://doi.org/10.1021/bm101315y
Liu Y, Ahmed S, Sameen DE, et al (2021) A review of cellulose and its derivatives in biopolymer-based for food packaging application. Trends Food Sci Technol 112:532–546. https://doi.org/10.1016/j.tifs.2021.04.016
Lyytikäinen J, Morits M, Österberg M, et al (2021) Skin and bubble formation in films made of methyl nanocellulose, hydrophobically modified ethyl(hydroxyethyl)cellulose and microfibrillated cellulose. Cellulose 28:787–797. https://doi.org/10.1007/s10570-020-03557-0
Montane D, Farriol X, Salvadó J, et al (1998) Application of steam explosion to the fractionation and rapid vapor-phase alkaline pulping of wheat straw. Biomass Bioenergy 14:261–276. https://doi.org/10.1016/S0961-9534(97)10045-9
Müller M, Czihak C, Schober H, et al (2000) All Disordered Regions of Native Cellulose Show Common Low-Frequency Dynamics. Macromolecules 33:1834–1840. https://doi.org/10.1021/ma991227l
Oprea M, Voicu SI (2020) Recent advances in composites based on cellulose derivatives for biomedical applications. Carbohydr Polym 247:116683. https://doi.org/10.1016/j.carbpol.2020.116683
Shaghaleh H, Xu X, Wang S (2018) Current progress in production of biopolymeric materials based on cellulose, cellulose nanofibers, and cellulose derivatives. RSC Adv 8:825–842. https://doi.org/10.1039/C7RA11157F
Sheltami RM, Abdullah I, Ahmad I, et al (2012) Extraction of cellulose nanocrystals from mengkuang leaves (Pandanus tectorius). Carbohydr Polym 88:772–779. https://doi.org/10.1016/j.carbpol.2012.01.062
Singh RK, Sharma OP, Singh AK (2014) Evaluation of Cellulose Laurate Esters for Application as Green Biolubricant Additives. Ind Eng Chem Res 53:10276–10284. https://doi.org/10.1021/ie501093j
Sonia A, Priya Dasan K (2013) Chemical, morphology and thermal evaluation of cellulose microfibers obtained from Hibiscus sabdariffa. Carbohydr Polym 92:668–674. https://doi.org/10.1016/j.carbpol.2012.09.015
Sun R, Sun XF (2002) Structural and thermal characterization of acetylated rice, wheat, rye, and barley straws and poplar wood fibre. Ind Crops Prod 16:225–235. https://doi.org/10.1016/S0926-6690(02)00050-X
Tarasova E, Savale N, Krasnou I, et al (2023) Preparation of Thermoplastic Cellulose Esters in [mTBNH][OAC] Ionic Liquid by Transesterification Reaction. Polymers (Basel) 15:3979. https://doi.org/10.3390/polym15193979
Uschanov P, Johansson L-S, Maunu SL, Laine J (2011) Heterogeneous modification of various celluloses with fatty acids. Cellulose 18:393–404. https://doi.org/10.1007/s10570-010-9478-7
Yang Z-Y, Wang W-J, Shao Z-Q, et al (2013) The transparency and mechanical properties of cellulose acetate nanocomposites using cellulose nanowhiskers as fillers. Cellulose 20:159–168. https://doi.org/10.1007/s10570-012-9796-z
Zhang Y, Shao H, Hu X (2002) Atomic force microscopy of cellulose membranes prepared from the N -methylmorpholine‐ N ‐oxide/water solvent system. J Appl Polym Sci 86:3389–3395. https://doi.org/10.1002/app.11344

No competing interests reported.

Download PDF

Editorial decision: Revision requested
29 Sep, 2024
Editor assigned by journal
29 Sep, 2024
Submission checks completed at journal
16 Sep, 2024
First submitted to journal
25 Jul, 2024

You are reading this latest preprint version

Effect of controlled drying on the properties of cellulose ester films synthesized in Novel Ionic Liquid [mTBNH][OAc]

Status:

Version 1

Abstract

Figures

Introduction

Experimental Section

2.1. Materials

2.2. Cellulose dissolution in the solvent system

2.3. Solvent casting of cellulose films

2.4 Characterisation

2.4.1 Fourier Transform Infrared (FTIR) Spectroscopy

2.4.2 Contact Angle measurement.

2.4.3 X-ray diffraction analysis (XRD).

2.4.4 Scanning electron microscopy (SEM)

2.4.5 Atomic force microscopy (AFM)

2.4.6 Thermogravimetric Analysis (TGA)

Results and Discussion

5.1. Fourier Transform Infrared (FTIR) Spectroscopy

5.2 Contact Angle measurement.

5.3. X-ray diffraction analysis (XRD).

5.4 Thermogravimetric Analysis (TGA)

5.5. Scanning Electron Microscopy (SEM)

5.6. Atomic Force Microscopy (AFM)

Conclusions

Declarations

Ethical Approval

Funding

Author Contribution

References

Additional Declarations

Status:

Version 1