Interplay between gelation and phase separation in aqueous solutions of methylcellulose and hydroxypropylmethylcellulose.
Thermally induced gelation in aqueous solutions of methylcellulose (MC) and hydroxypropylmethylcellulose (HPMC) has been studied by rheological, optical microscopy, and turbidimetry measurements. The structural and mechanical properties of these hydrogels are dominated by the interplay between phase separation and gelation. In MC solutions, phase separation takes place almost simultaneously with gelation. An increase in the storage modulus is coupled to the appearance of a bicontinuous structure upon heating. However, a thermal gap exists between phase separation and gelation in the case of HPMC solutions. The storage modulus shows a dramatic decrease during phase separation and then rises in the subsequent gelation. A macroporous structure forms in the gels via "viscoelastic phase separation" linked to "double phase separation".
Department of Chemistry, The University of Sheffield, Sheffield S3 7HF, U.K.
J Patrick A
JP
Fairclough
Hao
H
Yu
Oscar
O
Kelly
Anthony J
AJ
Ryan
Robert L
RL
Sammler
Michael
M
Radler
D005782:Gels / Q000138:chemical synthesis / Q000737:chemistry; D065347:Hypromellose Derivatives; D008747:Methylcellulose / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry*; D015394:Molecular Structure; D012212:Rheology; D012996:Solutions; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
D005782:Gels; D012996:Solutions; D014867:Water; D065347:Hypromellose Derivatives; D008747:Methylcellulose