Linked Life Data

16479588

Source:http://linkedlifedata.com/resource/pubmed/id/16479588

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
2006-5-15
pubmed:abstractText
Curious low-temperature solubility of cellulose triacetates (CTA; here we use nominally "CTA," but the sample still contains 7% of C-6 position hydroxyls) in an organic solvent, methyl acetate (MA), was studied by a newly designed low-temperature type of DLS apparatus, which enabled for the first time to investigate the structural change of CTA in solution from 45 degrees C down to -100 degrees C. A molecularly dissolved CTA was found to coexist with three types of self-assemblies over all the temperature ranges except for the three specific temperatures T* of 30, -10, and -75 degrees C. However, these multiple self-assemblies are not in real thermodynamic equilibrium but in a metastable state, which could be stabilized effectively by the intermolecular hydrogen bonding (HB) with the help of the dipole interaction at low temperatures. In more detail, with decreasing temperature, these assemblies performed the structural reorganization drastically at three T*'s and would finally be frozen in a physical gel structure at -99 degrees C; around the freezing temperature of MA, CTA molecules could be trapped homogeneously in the frozen MA. The crucial role in such structural reorganizations is played by the balance between the intermolecular HB and the dipole interaction worked in the highly electronegative solvent. Because these interactions, which are mediated by the solvent electronegativity, change drastically with temperature, they result in the control of not only the single CTA chain conformation (= the intramolecular HB) but also the binding ways of the intermolecular HBs between CTA molecules and they induce multitudinous metastable structures in solution. Here it is noted that HB could work mainly between the C-6 position hydroxyls in the anhydroglucose units of CTA and are essentially effective at low temperatures.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jun
pubmed:issn
0006-3525
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
82
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
222-33
pubmed:meshHeading
pubmed:year
2006
pubmed:articleTitle
Low-temperature dynamic light scattering. I. Structural reorganization and physical gel formation in cellulose triacetate/methyl acetate dilute solution at -99 - 45 degrees C.
pubmed:affiliation
Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan. yh-tsunashima@r7.dion.ne.jp
pubmed:publicationType
Journal Article