Fibrillar Structure in Aqueous Methylcellulose Solutions and Gels

Lott, Joseph; McAllister, John W.; Wasbrough, Matthew J.; Sammler, Robert L.; Bates, Frank S.; Lodge, Timothy P.

doi:10.1021/ma4021642

Cited by 77 publications

(149 citation statements)

References 71 publications

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“…The amount and size of the particles almost don't grow even temperature was increased to 45°C. These particles are indeed the azo-EHPC1 microgels, in which nanofibers are possibly formed, as in the MC gels recently revealed by cryo-TEM (Lott et al 2013b). This causes different refractive index between the microgels and the surrounding solution, resulting in appearance of solution turbidity.…”

Section: Phase Transition Measured By Microscopysupporting

confidence: 56%

“…Due to nontoxicity, biodegradability and biocompatibility, it has been generally recognized safe by the U.S. Food and Drug Administration for application in many fields as pharmaceutical, food, biomedical, thickener, and binder (Gong et al 2012;Patra et al 2012). It has attracted much research attention because it resonates with the concept of green chemistry and sustainable material world (Lott et al 2013b). Similar to the sol-gel transition behavior of other cellulose ethers such as methylcellulose (MC) and hydroxypropylmethylcellulose (HPMC) in water (Bajwa et al 2009;Fairclough et al 2012;Haque and Morris 1993;Kobayashi et al 1999), aq.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Phase Transition Measured By Microscopysupporting

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Thermal inverse phase transition of azobenzene hydroxypropylcellulose in aqueous solutions

Zhang

Liu

2016

Cellulose

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“…Between 55 and 75 °C, a large increase of G' is observed depending on the polymer concentration (when it is higher than C*) and the turbid strong gel is formed corresponding to the second step of gelation, together with the phase separation [20]. This second step has been more widely studied in the literature [6,22,64]. The mechanism of phase separation observed over 50 °C, dependent on the chemical structure, polymer concentration and molecular weight, is still under discussion.…”

Section: Influence Of the Molecular Weight And Concentration On The Mmentioning

confidence: 99%

“…Additionally, MC gelation is influenced by the substitution pattern [11] and co-ingredients like salts, sugars, and alcohols [16,17]. The influence of the molecular weight (MW) is still under discussion [6,7,[18][19][20] as well as the structure of the strong turbid gel [15,[21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Methylcellulose, a Cellulose Derivative with Original Physical Properties and Extended Applications

et al. 2015

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This review covers the preparation, characterization, properties, and applications of methylcelluloses (MC). In particular, the influence of different chemical modifications of cellulose (under both heterogeneous and homogeneous conditions) is discussed in relation to the physical properties (solubility, gelation) of the methylcelluloses. The molecular weight (MW) obtained from the viscosity is presented together with the nuclear magnetic resonance (NMR) analysis required for the determination of the degree of methylation. The influence of the molecular weight on the main physical properties of methylcellulose in aqueous solution is analyzed. The interfacial properties are examined together with thermogelation. The surface tension and adsorption at interfaces are described: surface tension in aqueous solution is independent of molecular weight but the adsorption at the solid interface depends on the MW, the higher the MW the thicker the polymeric layer adsorbed. The two-step mechanism of gelation is confirmed and it is shown that the elastic moduli of high temperature gels are not dependent on the molecular weight but only on polymer concentration. Finally, the main applications of MC are listed showing the broad OPEN ACCESSPolymers 2015, 7 778 range of applications of these water soluble cellulose derivatives.

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“…The same group of researchers has also demonstrated by cryogenic transmission electron microscopy and small-angle neutron scattering that MC hydrogels have a heterogeneous fibrillar structure that is responsible for their turbidity [66,67].…”

Section: Colloidal Dissolution and Gelation As Processes Involved In mentioning

confidence: 98%

Cellulose-Derivatives-Based Hydrogels as Vehicles for Dermal and Transdermal Drug Delivery

Vlaia¹,

Coneac²,

Olariu³

et al. 2016

Emerging Concepts in Analysis and Applications of Hydrogels

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The use of water-soluble polymers of natural, semisynthetic, and synthetic origin for dermal and transdermal drug delivery systems is manifold. Among the most used biopolymers in the formulation of skin preparations, the cellulose ether derivatives as representatives of semisynthetic polymers distinguish through their specific physicochemical properties, by which the pharmacist can select the appropriate cellulose derivative for a particular purpose. The hydrogels containing cellulose derivatives as gelling agents are widely used as water-soluble ointment bases, because they usually associate the characteristics of both conventional and innovative hydrogels, including especially safety, biocompatibility, biodegradability, and a relatively easy way of preparation and low price. The present chapter describes the following issues: the physicochemical properties of water-soluble cellulose derivatives in relationship with their type and grade; physical and chemical properties of cellulose-derivatives-based hydrogels and their compatibility with other auxiliary substances commonly used in the formulation of pharmaceutical hydrogels; the development and manufacturing of these hydrogels on both small and large scales; the characterization of cellulose derivatives hydrogels as pharmaceutical dosage forms through different compendial and noncompendial methods; and well-recognized and novel applications of cellulosederivatives-based hydrogels for dermal and transdermal drug delivery.

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Fibrillar Structure in Aqueous Methylcellulose Solutions and Gels

Cited by 77 publications

References 71 publications

Thermal inverse phase transition of azobenzene hydroxypropylcellulose in aqueous solutions

Thermal inverse phase transition of azobenzene hydroxypropylcellulose in aqueous solutions

Methylcellulose, a Cellulose Derivative with Original Physical Properties and Extended Applications

Cellulose-Derivatives-Based Hydrogels as Vehicles for Dermal and Transdermal Drug Delivery

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