Study on the thermoresponsive two phase transition processes of hydroxypropyl cellulose concentrated aqueous solution: from a microscopic perspective

Jing, Ying; Wu, Peiyi

doi:10.1007/s10570-012-9816-z

Cited by 20 publications

(19 citation statements)

References 35 publications

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“…This could potentially be attributed to temperature induced hydrophobicity of the HPC occurring in stages due to different types of water bonding being present in solution. Specifically, water molecules that are hydrogen bonded to OH groups on the HPC chain will dissociate first followed by dissociation of OH groups bonded to methyne, methyl and methylene groups at higher temperatures [27]. The breaking of this latter group of bonds results in hydrophobic interaction of the methyl groups in HPC subsequently then leading to coil-to-globule transition occurring.…”

Section: δ(λ) Is the Wavelength Interval τE(λ) Is The Solar Direct Tmentioning

confidence: 99%

Transmittance and Reflectance Studies of Thermotropic Material for a Novel Building Integrated Concentrating Photovoltaic (BICPV) ‘Smart Window’ System

Connelly

et al. 2017

Energies

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Abstract:A novel Building Integrated Concentrating Photovoltaic (BICPV) Smart Window has been designed and developed as a next generation intelligent window system. In response to climatic conditions, the smart window varies solar light transmission into the building for provision of light and heat with the reflection of light to the photovoltaic (PV) for electricity generation. This unique function is realised using an integrated thermotropic layer in conjunction with embedded PVs. As commercial PVs are readily available, the success of this novel BICPV design depends solely on the performance of the thermotropic material. This study aimed to develop a suitable reflective thermotropic layer for the proposed smart Concentrating Photovoltaic (CPV) system. A Hydroxypropyl cellulose (HPC) polymer was tested for its applicability as a potential reflective thermotropic material for this purpose. HPC concentration was systematically varied from 1 wt. % to 6 wt. % in aqueous solution so as to provide insight into the relationship between transmittance/reflectance properties, the concentration of the thermotropic material and their dependence upon the environmental temperature. The degree of hysteresis of light transmittance upon subjecting HPC to heating and cooling cycles was also investigated. Specifically, for the HPC liquid samples the measured threshold temperature/transition temperature (T s ) was observed to be approximately 40 • C for 6 wt. % HPC, increasing to approximately 44 • C for 1 wt. % HPC. No hysteresis was observed upon heating and cooling HPC samples. Reflectance below the T s was recorded at~10%, increasing up to~70% above the T s for 6 wt. % HPC. Finally, a HPC-based hydrogel membrane sample was developed and exhibited good thermotropic activity therefore demonstrating its suitability for use within the BICPV smart window. This study corroborates that HPC is a suitable thermotropic material in the application of next generation BICPV smart window systems.

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Section: δ(λ) Is the Wavelength Interval τE(λ) Is The Solar Direct Tmentioning

confidence: 99%

Transmittance and Reflectance Studies of Thermotropic Material for a Novel Building Integrated Concentrating Photovoltaic (BICPV) ‘Smart Window’ System

Connelly

et al. 2017

Energies

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“…HPC solutions show thermoreversible phase transition behavior, i.e. an optically transparent HPC solution undergoes phase separation and turns into turbid gel when the solution temperature is above the lower critical solution temperature (LCST), while it returns to a clear solution on cooling (Jing and Wu 2013;Streletzky et al 2008;Vshivkov and Rusinova 2007). This characteristic feature has been extensively studied to understand its mechanism.…”

Section: Introductionmentioning

confidence: 99%

“…Through another methodology, most researchers focus on using instrumental techniques to elucidate the thermodynamic mechanisms involved in the sol-gel transition and/or phase separation. These techniques include turbidity, laser light scattering, viscometry, rheology, differential scanning calorimetry (Arvidson et al 2012;Fairclough et al 2012;Lu et al 2002;Xu et al 2004), and recently by mid/near infrared spectroscopy (Jing and Wu 2013), small-angle neutron scattering combined with cryogenic transmission electron microscopy (cryo-TEM) (Lott et al 2013a, b;McAllister et al 2015). These studies demonstrate that the sol-gel transition is a spinodal process (Takeshita et al 2010) or a nucleation and growth mechanism (Arvidson et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Thermal inverse phase transition of azobenzene hydroxypropylcellulose in aqueous solutions

Zhang

Liu

2016

Cellulose

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Water soluble 2-azobenzenoxy-ethoxyhydroxpropylcelluloses (azo-EHPC) were synthesized by etherification reaction of bromoethoxy-azobenzene (BEA) with hydroxypropylcellulose (HPC) to study their phase transition behavior in aq. solution. The degree of substitution (DS) of the water soluble azoEHPCs was less than 0.066. Their chemical structure and thermal property were characterized by proton nuclear magnetic resonance ( 1 H-NMR), fourier transform infrared spectroscopy (FT-IR), and differential scanning calorimetry. The azo-EHPC showed a reversible sol-gel transition behavior in its aq. solution, i.e. a clear azo-EHPC aq. solution became turbid when the solution temperature surpassed a lower critical solution temperature (LCST). The sol-gel transition phenomenon was investigated by optical microscopy and turbidimetric measurement. It was found that the LCST was related to the cis-/transconformation of the azobenzene side group, the type of cyclodextrin (CD), concentration of azo-EHPC, and NaCl concentration. The LCST of azo-EHPC was lower than that of HPC (36.6°C) by at most 13.6°C, and the LCST of trans-azo-EHPC was less than that of cis-azo-EHPC by ca. 3°C. Additionally, the presence of CD in solutions displayed a positive effect on the LCST, i.e. increasing the LCST by 3-5°C. And this impact was more profound on the azo-EHPC with higher DS values. The thermoreversible phase transition mechanism was discussed. We proposed that the effect of DS, conformation of azobenzene group, azo-EHPC concentration, salt concentration, and CD on the LCST of azo-EHPCs was a rearrangement of the hydrophilic/hydrophobic interaction between side azobenzene groups and water molecules.

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“…The thermally induced HPC nanospheres can be in situ chemically crosslinked using DVS to form narrowly distributed surfactant‐free thermal sensitive HPC microgels . In concentrated HPC aqueous solutions, a coil‐globule transition and then a sol‐gel transition occurred when the solutions were heated …”

Section: Physical Crosslinkingmentioning

confidence: 99%

Cellulose-Based Gels

Kang

Liu

Huang

2016

Macromol. Chem. Phys.

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Cellulose is the most available biomacromolecule in nature with the properties of renewability, biodegradability, biocompatibility, and environmental friendliness. Cellulose and its derivatives are excellent building blocks for fabrication of gels. In this review, the principles for preparing cellulose‐based gels are summarized in detail. Considering the native properties of cellulose and its derivatives, chemical and/or physical crosslinking can be introduced during the preparation of cellulose‐based gels. The chemical and physical crosslinking approaches are classified alongside the introduction of new concepts in polymer science, such as supramolecular interactions. Cellulose graft copolymers are another kind of building block in the fabrication of cellulose‐based gels. The properties of gels can be tailored by the chemical structure of the graft chains. Cellulose‐based gels can be applied in many fields depending on their properties.

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Study on the thermoresponsive two phase transition processes of hydroxypropyl cellulose concentrated aqueous solution: from a microscopic perspective

Cited by 20 publications

References 35 publications

Transmittance and Reflectance Studies of Thermotropic Material for a Novel Building Integrated Concentrating Photovoltaic (BICPV) ‘Smart Window’ System

Transmittance and Reflectance Studies of Thermotropic Material for a Novel Building Integrated Concentrating Photovoltaic (BICPV) ‘Smart Window’ System

Thermal inverse phase transition of azobenzene hydroxypropylcellulose in aqueous solutions

Cellulose-Based Gels

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