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The percentage of carbon O-C]O bonds (fingerprint for CTA, top) and the relative amount of silicon (fingerprint for TMSC, bottom) as a function of the CTA fraction in the original spin coating solution. The CTA fractions 0, 0.5 and 1 correspond to TMSC/CTA blend ratios 1 : 0, 1 : 1 and 0 : 1, respectively. The relative amount of the bond emission and relative atomic concentrations is obtained from the XPS measurements.
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![Fig. 5 The percentage of carbon O-C]O bonds (fingerprint for CTA, top)...](profile/Orlando-Rojas-2/publication/255756454/figure/fig5/AS:670466637328403@1536863111399/The-percentage-of-carbon-O-CO-bonds-fingerprint-for-CTA-top-and-the-relative-amount_Q320.jpg)
The preparation of ultrathin (<100 nm) bicomponent films from hydrophobic polysaccharides with phase-specific poregrowth was demonstrated and the underlying phenomena behind morphology formation were fundamentally investigated. The films were constructed, in a single-step process, by spin coating mixtures of trimethylsilyl cellulose (TMSC) and cell...
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... present only in CTA (binding energy 289.3 eV). Thus the O-C]O bond emission can be solely ascribed to the CTA component. Silicon is present in TMSC and also in the solid support, but considering the analysis depth of XPS, <10 nm, and the typical film thickness (20-80 nm), it is expected that all silicon arises from TMSC in the TMSC/CTA films. In Fig. 5 (top), the percentage of O-C]O bond emission is shown as a function of the fraction of CTA in the initial spin coating solution. With most blend ratios, the amount of a given component in the spin coating solution correlated with the amount of the same component present in the film, as has been found in studies with other polymer blends. ...
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... has been found in studies with other polymer blends. 24,30,34,35 However, ambiguity in XPS analyses is expected due to the non-homoge- neous distribution of the components on the surface of the sample. It is apparent, nevertheless, that both horizontal and vertical phase separation took place during the film formation. The experimental points in Fig. 5 would be linearly aligned had the films exhibited only vertical phase separation. This is clearly not the case here and it also correlates with the observed phase separation patterns in Fig. 2. An interesting further observation from the XPS analysis is that TMSC seemed to be enriched on the surface, especially when applied as the ...
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... would be linearly aligned had the films exhibited only vertical phase separation. This is clearly not the case here and it also correlates with the observed phase separation patterns in Fig. 2. An interesting further observation from the XPS analysis is that TMSC seemed to be enriched on the surface, especially when applied as the majority phase (Fig. 5, ...
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... to a level of neat TMSC (Fig. 6). Thus, a critical, small amount of TMSC was enough to bring the WCA to a value similar to that of neat TMSC. As expected, the conversion of TMSC to cellulose reduced the WCA of the films. This is substantial indication that there is a thin TMSC top-layer on the films and it also correlates with the XPS results (Fig. ...
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... Such cellulose thin films have a tuneable morphology, a defined composition, and can be manufactured with high reproducibility (Aulin et al., 2009;Hoeger et al., 2012;Sampl et al., 2019;Strasser et al., 2016;Taajamaa, Rojas, Laine, & Kontturi, 2011;Weißl et al., 2019;Weißl et al., 2018). It was also reported that depending on the cellulose precursor different contributions to the surface free energies J o u r n a l P r e -p r o o f were realized Weißl et al., 2018), which was shown to be an effect originating from aggregation. ...
Optical brightening agents (OBAs) are commonly used in textile and paper industry to adjust product brightness and color appearence. Continuous production processes lead to short residence time of the dyes in the fiber suspension, making it necessary to understand the kinetics of adsorption. The interaction mechanisms of OBAs with cellulose are challenging to establish as the fibrous nature of cellulosic substrates complicates acquisition of real-time data. Here, we explore the real-time adsorption of different OBAs (di, tetra- and hexasulfonated compounds) onto different cellulose surfaces using surface plasmon resonance spectroscopy. Ionic strength, surface topography, and polarity were varied and yielded 0.76 to 11.35 mg m² OBA on cellulose. We identified four independent mechanisms governing OBA-cellulose interactions. This involves the polarity of the cellulose surface, the solubility of the OBA, the ionic strength during adsorption and presence of bivalent cations such as Ca²⁺. These results can be exploited for process optimization in related industries as they allow for a simple adjustment and experimental testing procedures including performance assessment of novel OBAs.
... TMSC was also used with cellulose acetate, to prepare ultrathin films of two distinct cellulose derivatives (Taajamaa et al., 2011). The resulting morphologies were peculiar with pores emerging that were exclusively in the cellulose acetate phase ( Figure 4C). ...
... AFM images of blend films of cellulose, regenerated from TMSC with other polymers at following ratios: (A) TMSC/PS 2:1, 20 × 20 µm 2 scan as in reference (Reproduced fromKontturi et al., 2005b with permission from American Chemical Society); (B) TMSC/PMMA 1:7, 5 × 5 µm 2 scan (Reproduced from with permission from Royal Society of Chemistry); (C) TMSC/CTA 1:2, 5 × 5 µm 2 scan (Reproduced fromTaajamaa et al., 2011 with permission from Royal Society of Chemistry); (D) same film as in (C) but CTA has been removed with a selective solvent, 5 × 5 µm 2 scan (Reproduced fromTaajamaa et al., 2011 with permission from Royal Society of Chemistry); (E) TMSC/CSE 3:1, 10 × 10 µm 2 scan (Reproduced fromNiegelhell et al., 2017 with permission from American Chemical Society); (F) TMSC/CSE 1:1, 10 × 10 µm 2 scan (Reproduced fromNiegelhell et al., 2017 with permission from American Chemical Society). ...
... AFM images of blend films of cellulose, regenerated from TMSC with other polymers at following ratios: (A) TMSC/PS 2:1, 20 × 20 µm 2 scan as in reference (Reproduced fromKontturi et al., 2005b with permission from American Chemical Society); (B) TMSC/PMMA 1:7, 5 × 5 µm 2 scan (Reproduced from with permission from Royal Society of Chemistry); (C) TMSC/CTA 1:2, 5 × 5 µm 2 scan (Reproduced fromTaajamaa et al., 2011 with permission from Royal Society of Chemistry); (D) same film as in (C) but CTA has been removed with a selective solvent, 5 × 5 µm 2 scan (Reproduced fromTaajamaa et al., 2011 with permission from Royal Society of Chemistry); (E) TMSC/CSE 3:1, 10 × 10 µm 2 scan (Reproduced fromNiegelhell et al., 2017 with permission from American Chemical Society); (F) TMSC/CSE 1:1, 10 × 10 µm 2 scan (Reproduced fromNiegelhell et al., 2017 with permission from American Chemical Society). ...
A literature review on ultrathin films of cellulose is presented. The review focuses on different deposition methods of the films—all the way from simple monocomponent films to more elaborate multicomponent structures—and the use of the film structures in the vast realm of materials science. The common approach of utilizing cellulose thin films as experimental models is therefore omitted. The reader will find that modern usage of cellulose thin films constitutes an exciting emerging area within materials science and it goes far beyond the traditional usage of the films as model systems.
... Other works on blend films being composed of TMSC and cellulose triacetate (CTA) show micrometer-sized pores at ratios of 5:1 and 1:5 TMSC/CTA with the smallest pores at a ratio of 1:1, a property that is suprisingly not observed here, demonstrating the influence of the polymer composition on the phase separation process. 37,38 It could be shown that the polymer phase occupying a larger surface area is TMSC by developing the film with hexamethyldisiloxane (HMDSO) before, or with chloroform (CHCl 3 ) after cleavage of the TMS groups (Supporting Information, Figure S1). It was however not possible to unambiguously distinguish the different polymer phases of cellulose and PCL via energy-dispersive X-ray spectroscopy (data not shown). ...
This work describes the interaction of the human blood plasma proteins albumin, fibrinogen and γ-globulins with micro-and nano-patterned polymer interfaces. Protein adsorption studies were correlated to the fibrin clotting time of human blood plasma and to the growth of primary human endothelial cells (hECs) on these patterns. It was observed that blends of polycaprolactone (PCL) and trimethylsilyl protected cellulose (TMSC) form various thin film patterns during spin coating, depending on the mass ratio of the polymers in the spinning solutions. Vapor phase acid catalyzed deprotection preserves these patterns but yields interfaces that are composed of hydrophilic cellulose domains enclosed by hydrophobic PCL. Mentioned blood plasma proteins are repelled by the cellulose domains allowing for a suggested selective protein deposition on the PCL domains. An inverse proportional correlation is observed between the amount of cellulose present in the films and the mass of irreversibly adsorbed proteins. This results in significantly increased fibrin clotting times and lower masses of deposited clots on cellulose containing films as revealed by quartz crystal microbalance measurements. Cell viability of hECs grown on these surfaces was directly correlated to higher protein adsorption and faster clot formation. The results show that presented patterned polymer composite surfaces allow for a controllable blood plasma protein coagulation and a significant biological response from hECs. It is proposed that this knowledge can be utilized in regenerative medicine, cell cultures and artificial vascular grafts by a careful choice of polymers and patterns.
... Such phase separation is already noticed for the first ALG-CMC layer ( Figure S1). The reports on the phase separation of polymer blends from (organo-soluble) hydrophobic polymers upon spin-coating are manifold (Taajamaa et al., 2011;Strasser et al., 2016). Whereas, no studies on the formation of blend surfaces from spin-coated polysaccharides, which are hydrophilic and water-soluble, can be found to the best of our knowledge. ...
... The segregate phase separation is well-known for water soluble polymers (e.g., proteins-polysaccharides) for several years (Doublier et al., 2000), but not reported for spincoated blend films. Keeping this mind, we believe that the lateral phase separation that occurred in the case of ALG-CMC blend, which stays in one phase in water, is of the segregate type, which can be explained by the transient bilayer theory (Heriot and Jones, 2005;Taajamaa et al., 2011). ...
... With the evaporation of more solvent from the film, the upper layer of the film gets unstable with the formation of holes. The latter is then filled with the lower (liquid phase) layer as it is shown for ALG-CMC coated (first) layer ( Figure S1) (Taajamaa et al., 2011). Interestingly, the phase separation is retained even after the third layer (Figure 1, top row and Figure S2). ...
Chronic wounds not only lower the quality of patient's life significantly, but also present a huge financial burden for the healthcare systems around the world. Treatment of larger wounds often requires the use of more complex materials, which can ensure a successful renewal or replacement of damaged or destroyed tissues. Despite a range of advanced wound dressings that can facilitate wound healing, there are still no clinically used dressings for effective local pain management. Herein, alginate (ALG) and carboxymethyl cellulose (CMC), two of the most commonly used materials in the field of chronic wound care, and combination of ALG-CMC were used to create a model wound dressing system in the form of multi-layered thin solid films using the spin-assisted layer-by-layer (LBL) coating technique. The latter multi-layer system was used to incorporate and study the release kinetics of analgesic drugs such as diclofenac and lidocaine at physiological conditions. The wettability, morphology, physicochemical and surface properties of the coated films were evaluated using different surface sensitive analytical tools. The influence of in situ incorporated drug molecules on the surface properties (e.g., roughness) and on the proliferation of human skin cells (keratinocytes and skin fibroblasts) was further evaluated. The results obtained from this preliminary study should be considered as the basis for the development “real” wound dressing materials and for 3D bio-printing applications.
... As revealed in the AFM images (Figure 1), the microphase separation seemingly proceeds according to the transient bilayer theory, describing the vertical stratification of the two phases, followed by interfacial instabilities, caused by a solvent-concentration gradient troughout the film, leading to lateral phase separation. 22 The final structure of the resulting domains is defined by a variety of factors, such as film thickness, 23,24 relative humidity, 11,25 temperature, 26 the type of substrate, 27 solubility of the blend components in the solvent used, 23,27−29 and surface segregation, 30−32 which is the preferential migration of one component to the interface, depending on surface free energy. This complex interplay of parameters complicates the explanation of the emerging phase structures without evidence from time-resolved, small-angle X-ray scattering or light reflectivity during the spin coating process. ...
The creation of nano- and micropatterned polymer films is a crucial step for innumerous applications in science and technology. However, there are several problems associated with environmental aspects concerning the polymer synthesis itself, crosslinkers to induce the patterns as well as toxic solvents used for the preparation and even more important development of the films (e.g. chlorobenzene). In this paper, we present a facile method to produce micro- and nanopatterned biopolymer thin films using enzymes as so called biodevelopers. Instead of synthetic polymers, naturally derived ones are employed, namely poly-3-hydroxybutyrate and a cellulose derivative which are dissolved in a common solvent in different ratios and subjected to spin coating. Consequently, the two biopolymers undergo microphase separation and different domain sizes are formed depending on the ratio of the biopolymers. The development step proceeds via addition of the appropriate enzyme (either PHB-depolymerase or cellulase) whereas one of the two biopolymers is selectively degraded, while the other one remains on the surface. In order to highlight the enzymatic development of the films, video AFM studies have been performed in real time to image the development process in situ as well as surface plasmon resonance spectroscopy to determine the kinetics. These studies may pave the way for the use of enzymes in lithographic processes, particularly for materials intended to be used in a physiological environment.
... If one's goal is to enhance the cellulosic nature of a surface, then a possible strategy would be to deposit an ultra-thin film of cellulose on that surface. There are numerous accounts on the formation of ultrathin films of cellulose (Song et al. 2009a,b;Taajamaa et al. 2011;Hoeger et al. 2011Hoeger et al. , 2012Csoka et al. 2011Csoka et al. , 2012Martín-Sampedro et al. 2013). The reader is referred to a critical review on the subject, including the methodology of preparation, as well as the applications of the films for fundamental research (Kontturi et al. 2006). ...
Many current and potential uses of cellulosic materials depend critically on the character of their surfaces. This review of the scientific literature considers both well-established and emerging strategies to change the outermost surfaces of cellulosic fibers or films not only in terms of chemical composition, but also in terms of outcomes such as wettability, friction, and adhesion. A key goal of surface modification has been to improve the performance of cellulosic fibers in the manufacture of composites through chemistries such as esterification that are enabled by the high density of hydroxyl groups at typical cellulosic surfaces. A wide variety of grafting methods, some developed recently, can be used with plant-derived fibers. The costs and environmental consequences of such treatments must be carefully weighed against the potential to achieve similar performances by approaches that use more sustainable methods and materials and involve less energy and processing steps. There is potential to change the practical performances of many cellulosic materials by heating, by enzymatic treatments, by use of surface-active agents, or by adsorption of polyelectrolytes. The lignin, hemicelluloses, and extractives naturally present in plant-based materials also can be expected to play critical roles in emerging strategies to modify the surfaces characteristics of cellulosic fibers with a minimum of adverse environmental impacts.
Patterned films are essential to the commonplace technologies of modern life. However, they come at high cost to the planet, being produced from non-renewable, petrochemical-derived polymers and utilising substrates that require harsh, top-down etching techniques. Biopolymers offer a cheap, sustainable and viable alternative easily integrated into existing production techniques. We describe a simple method for the production of patterned biopolymer surfaces and the assignment of each biopolymer domain, which allows for selective metal incorporation used in many patterning applications. Protein and polysaccharide domains were identified by selective etching and metal incorporation; a first for biopolymer blends. Morphologies akin to those observed with synthetic polymer blends and block-copolymers were realised across a large range of feature diameter (200 nm to - 20 μm) and types (salami structure, continuous, porous and droplet-matrix). The morphologies of the films were tuneable with simple recipe changes, highlighting that these biopolymer blends are a feasible alternative to traditional polymers when patterning surfaces. The protein to polysaccharide ratio, viscosity, casting method and spin speed were found to influence the final film morphology. High protein concentrations generally resulted in porous structures whereas higher polysaccharide concentrations resulted in spherical discontinuous domains. Low spin speed conditions resulted in growth of protuberances ranging from 200 nm to 22 μm in diameter, while higher spin speeds resulted in more monodisperse features, with smaller maximal diameter structures ranging from 300 nm to 12.5 μm.
Cellulose triacetate (CTA) membranes occupy much of the gas separation market in natural gas processing. With a high CO2/N2 selectivity, this material may also be prospective for post-combustion carbon capture, if the permeance can be optimised. In capture applications, the impacts of liquid water condensate of variable pH, SOx and NOx on the gas separation performance are of critical interest to ensure maximum membrane lifetime. In this work, dense CTA membranes were aged in pH solutions of 3, 7 and 13 for a total of 60 days. It was found that the plasticisation of the CTA membrane when aged in pH 3 and pH 7 solutions enhanced the permeability of CO2 and N2 by over 30% with little impact on CO2/N2 selectivity. Conversely, the membrane aged at pH 13 failed due to hydrolysis reactions. The membrane was selective for SO2 over CO2 with a SO2 permeability of 20 Barrer. Conversely, NO did not readily permeate, so that the permeate composition was below the level of detection. CTA membranes stored in SO2/N2 and pure N2 for a 120 day period at 22 °C were relatively stable, with a slight loss in permeability due to membrane aging. Conversely, a significant loss in permeability was observed when these membranes were exposed to 0.74 kPa of NO for the same period. The performance loss appeared to relate to reaction of alcohol groups within the cellulose acetate structure with trace levels of NO2 in the gas mixture. The results highlight the possibility for use of CTA membranes in post-combustion capture, if the active layer thickness can be reduced to enhance gas flux.
The development of super-hydrophobic surfaces has been inspired by natural systems and uses a number of novel (nano) technologies. Superhydro-phobicity has stimulated much scientific and industrial interest because of applications in water repellency, self-cleaning, friction reduction, antifouling, etc. Despite its inherent hydrophilicity, cellulose has unparalleled advantages as a substrate for the production of super-hydrophobic materials. This is because of its abundance, biodegradability and unique physical, chemical and mechanical properties that compare advantageously with the non-renewable materials typically used. This review includes a comprehensive survey of the progress achieved so far in the production of super-hydrophobic materials based on cellulose. Emphasis is placed on the effects of cellulose surface chemistry and topography, both of which affect hydrophobicity. Overall, this contribution summarizes some of the aspects that are critical to advance this evolving field of science.
Morphologies featured in bicomponent 2D ultrathin films were reproduced on 3D non-woven microfibre structures. Fibre networks were constructed by electrospinning hydrophobised cellulose derivatives, trimethylsilyl cellulose (TMSC) and cellulose triacetate (CTA), dissolved in a common solvent. Diverse morphologies were obtained depending on the polymer blend ratio: electrospinning of TMSC produced non-continuous micron fibres with shallow dints, TMSC/CTA 5:1 flat micron fibres with regular pore arrays, TMSC/CTA 1:1 wrinkled micron fibres decorated with shallow dints and occasional larger pores, TMSC/CTA 1:5 flat micron fibres with ellipsoidal porous structures and finally, CTA that led to smooth micron and submicron fibres. The fibre mats were ultra-hydrophobic with characteristic water contact angles of ca. 150 degrees. In addition, they were characterised by high contact angle hysteresis, and water droplets adhered to the substrate even after tilting the system upside down. Through conversion of the respective components to cellulose, chemical and adsorption properties of the fibre networks could be tuned without significantly altering the large-scale network morphology.
