Water desorption from a confined biopolymer

Pradipkanti, L.; Satapathy, Dillip K.

doi:10.1039/c7sm02332d

Cited by 13 publications

(17 citation statements)

References 60 publications

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“…Subsequently, the substrates were rinsed thoroughly with Milli-Q water (resistivity of 18.2 MΩ cm) and flushed with dry nitrogen gas, resulting in clean Si substrates with a hydrophilic Si/Si–O surface. Additional details can be found in our earlier work . Several thin films of thicknesses in the range of 35–350 nm were prepared by spin-coating chitosan solutions at different concentrations onto the prepared Si/Si–O substrates at 9000 rpm for 120 s. The prepared films were aged at 80 °C for 12 h to remove the residual solvent.…”

Section: Methodsmentioning

confidence: 99%

“…Chitosan is a versatile biopolymer with multifunctional groups and possesses excellent film forming ability, − biocompatibility, and biodegradability. , As a result, it has been widely used in a range of applications, including biomedicine ,, and food packaging. , Among the various applications of chitosan, its use in bioelectronics has recently generated significant interest. − For instance, chitosan-based thin film transistors offer a route to flexible portable electronics. , Chitosan films have been integrated into lab-on-a-chip microelectromechanical systems that can perform advanced functions such as biorecognition, enzymatic conversion, and controlled drug release . Chitosan, in thin film form, has been used to fabricate photodiodes due to its low cost, easy processability, and compatibility with silicon .…”

Section: Introductionmentioning

confidence: 99%

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Modulation of Optical Anisotropy in Chitosan Thin Films: Role of Swelling

2021

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Thin films of chitosan, a biopolymer, have attracted attention as plausible candidates for several niche applications. Such uses would be better served by a deeper understanding of the physical characteristics of the films and their relationship to polymer confinement. Therefore, we have used spectroscopic ellipsometry to investigate the optical properties of chitosan thin films prepared by spin coating. Thin films of chitosan exhibited uniaxial anisotropy with a higher in-plane refractive index. This suggested that the polymer chains were preferentially oriented in the plane of the thin film. The optical anisotropy, defined as the difference between the in-plane and the outof plane refractive indices, increased upon decreasing the (dry) film thickness and the consequent increase in the one-dimensional confinement of the polymer chains. Upon exposure to solvent vapor, the film thickness increased and was accompanied by an exponential decrease in the optical anisotropy with increasing exposure time. The characteristic time of the exponential decrease was of the order of a few minutes and weakly increased with the dry film thickness. Deswelling experiments suggested that the preparation-induced residual stresses contributed negligibly to the observed optical anisotropy, which, in addition to the initial (dry) film thickness, also depended on the weight fraction of the penetrant in the swollen film. The continued increase in the film thickness, however, indicated that the swelling progressed for several hours before reaching saturation. Assuming the existence of a compact, bound layer of chitosan that could not swell upon exposure to solvent vapor, we defined a time-dependent "effective swelling ratio". The swelling kinetics of chitosan thin films of different initial thicknesses could be described using this single function, which suggested that the swelling process in these films was qualitatively identical.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modulation of Optical Anisotropy in Chitosan Thin Films: Role of Swelling

2021

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“…7−10 Chitosan films have a strong affinity toward water due to the presence of hydrophilic functional groups, and they substantially swell in humid environments. 2 The macroscale actuation characteristics of chitosan films in the presence of water 11 and the desorption kinetics of different kinds of water from the chitosan matrix 12 are recently demonstrated.…”

Section: ■ Introductionmentioning

confidence: 99%

“…On the other hand, its unique characteristics such as biocompatibility, biodegradability, nontoxicity, and natural abundance are fully utilized in industrial-scale applications in food technology, cosmetics, water treatment, and agriculture. − Chitosan films have a strong affinity toward water due to the presence of hydrophilic functional groups, and they substantially swell in humid environments . The macroscale actuation characteristics of chitosan films in the presence of water and the desorption kinetics of different kinds of water from the chitosan matrix are recently demonstrated.…”

Section: Introductionmentioning

confidence: 99%

Penetrant-Induced Glass-like Transition in Thin Chitosan Films

et al. 2021

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We present the water vapor-induced swelling and the emergence of a penetrant-induced glass-like transition in the substrate-supported glassy chitosan thin films. The time evolution of the film thickness under different levels of relative humidity conditions is measured in real-time using a spectroscopic ellipsometer equipped with a humidity cell. In a dry film, the network of chitosan chains is in a glassy state, and upon exposure to water vapor, initially, the film swells by Fickian diffusion of water molecules, which triggers the structural relaxations of the chains. Under higher humidity conditions, a relatively slower evolution of thickness succeeds the initial rapid swelling due to the non-Fickian sorption of water molecules. The swelling characteristics of the polymer films are accounted for by considering the diffusion−relaxation mechanism of chains in the presence of smaller penetrant molecules. The penetrant-induced glass-like transition (P g ), where the polymer film isothermally transits from a glassy to a rubbery state, is determined for pristine and cross-linked chitosan films. P g is determined from the abrupt change in the rate of swelling observed upon increasing the relative humidity. Chemical crosslinking has an evident influence on the penetrant-induced glass-like transition of the chitosan films. P g was found to rise sharply for stiffer films with higher cross-linking density.

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“…Table S4 compares the order of difference in the T g of polystyrene in PS-P-TiO 2 with the bulk states at 120 °C and RT respectively revealing drastic changes in polymer properties with the bulk characteristics. While the fragility index provides a good indication of stress-relaxation behaviour 55 , transition of PS to the fragile state in crystalline PS-P-TiO 2 (in ethanol) from an otherwise ‘strong’ PS configuration of the bulk state (Table S4), mirrors the ‘plasticized’ effect of variable water mobility under confinement of biopolymers 56 . We have discussed previously the tacticity of PS-P-TiO 2 8 a structural regulator in PS likely plays a prominent role in bond selectivity permitting crosslinking molecules and bridging structures.…”

Section: Confinement Uses a ‘Strained-induced’ Growth Mechanism To Bimentioning

confidence: 99%

Quantum scale biomimicry of low dimensional growth: An unusual complex amorphous precursor route to TiO2 band confinement by shape adaptive biopolymer-like flexibility for energy applications

Choi

Sonkaria

Fox

et al. 2019

Sci Rep

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Crystallization via an amorphous pathway is often preferred by biologically driven processes enabling living species to better regulate activation energies to crystal formation that are intrinsically linked to shape and size of dynamically evolving morphologies. Templated ordering of 3-dimensional space around amorphous embedded non-equilibrium phases at heterogeneous polymer─metal interfaces signify important routes for the genesis of low-dimensional materials under stress-induced polymer confinement. We report the surface induced catalytic loss of P=O ligands to bond activated aromatization of C−C C=C and Ti=N resulting in confinement of porphyrin-TiO2 within polymer nanocages via particle attachment. Restricted growth nucleation of TiO2 to the quantum scale (≤2 nm) is synthetically assisted by nitrogen, phosphine and hydrocarbon polymer chemistry via self-assembly. Here, the amorphous arrest phase of TiO2 is reminiscent of biogenic amorphous crystal growth patterns and polymer coordination has both a chemical and biomimetic significance arising from quantum scale confinement which is atomically challenging. The relative ease in adaptability of non-equilibrium phases renders host structures more shape compliant to congruent guests increasing the possibility of geometrical confinement. Here, we provide evidence for synthetic biomimicry akin to bio-polymerization mechanisms to steer disorder-to-order transitions via solvent plasticization-like behaviour. This challenges the rationale of quantum driven confinement processes by conventional processes. Further, we show the change in optoelectronic properties under quantum confinement is intrinsically related to size that affects their optical absorption band energy range in DSSC.

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Water desorption from a confined biopolymer

Cited by 13 publications

References 60 publications

Modulation of Optical Anisotropy in Chitosan Thin Films: Role of Swelling

Modulation of Optical Anisotropy in Chitosan Thin Films: Role of Swelling

Penetrant-Induced Glass-like Transition in Thin Chitosan Films

Quantum scale biomimicry of low dimensional growth: An unusual complex amorphous precursor route to TiO2 band confinement by shape adaptive biopolymer-like flexibility for energy applications

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