Prolonged Chaotic Oscillations During the Gel/Xerogel Transition in Silicon Tetramethoxide Polymerization as Detected by Pyrene Excimerization.

1986 ◽  
Vol 73 ◽  
Author(s):  
Vered R. Kaufman ◽  
David Avnir
Keyword(s):  
Phase Transitions ◽  
Excited State ◽  
Driving Forces ◽  
Sol Gel ◽  
Chaotic Oscillations ◽  
Gel Structure ◽  
Adsorption Sites ◽  
Surface Active Agents ◽  
Surface Active ◽  
Gel Phase

ABSTRACTWhen the polymerization of Si(OCH3)4 is carried out in the presence of surface active agents, prolonged oscillations (over 1000 hrs) at the gel/xerogel transition are observed. The oscillations are of large amplitude, they are slow (several hrs/period), and they exhibit a chaotic behaviour. The probe by which these oscillations are observed is emission from excited state monomeric and excimeric pyrene. It is suggested tentatively that the driving forces for this oscillation are the structural relaxation of the secondary polymeric gel structure and the dispersion of adsorbed pyrene to thermodynamically favored adsorption sites. Relevant models could be those of oscillatory sol/gel phase transitions and of oscillatory polymerization reactions. We are unaware of previous observations of oscillations in sol/gel systems.

Sol–Gel Phase Transitions in a Photochromic Spiropyran-Modified Material by Incorporation in a Hydrogel

2009 ◽  
Vol 9 (10) ◽  
pp. 5990-5996 ◽  
Author(s):  
Soo Jin Lee ◽  
Sung Ho Jung ◽  
Seok-Hoon Lee ◽  
Won Seok Han ◽  
Jong Hwa Jung
Keyword(s):  
Phase Transitions ◽  
Sol Gel ◽  
Gel Phase

scholarly journals Real-time characterization of hydrogel viscoelastic properties and sol-gel phase transitions using cantilever sensors

2020 ◽  
Vol 64 (4) ◽  
pp. 837-850
Author(s):  
Alexander P. Haring ◽  
Manjot Singh ◽  
Miharu Koh ◽  
Ellen Cesewski ◽  
David A. Dillard ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Real Time ◽  
Viscoelastic Properties ◽  
Sol Gel ◽  
Cantilever Sensors ◽  
Gel Phase

scholarly journals Non-invasive and continuous monitoring of the sol–gel phase transition of supramolecular gels using a fast (open-ended coaxial) microwave sensor

2015 ◽  
Vol 17 (9) ◽  
pp. 6212-6216 ◽  
Author(s):  
Adela I. Carrillo ◽  
Jürgen Bachl ◽  
Judith Mayr ◽  
Pedro J. Plaza-González ◽  
José M. Cátala-Civera ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Continuous Monitoring ◽  
Sol Gel ◽  
Non Invasive ◽  
Microwave Sensor ◽  
Supramolecular Gels ◽  
Gel Phase

A non-invasive open coaxial re-entrant microwave sensor allows for the continuous monitoring of sol–gel phase transitions in physical gels.

Porous Gel Coatings Obtained by Phase Separation in ORMOSIL System

2000 ◽  
Vol 628 ◽  
Author(s):  
Kazuki Nakanishi ◽  
Souichi Kumon ◽  
Kazuyuki Hirao ◽  
Hiroshi Jinnai
Keyword(s):  
Phase Separation ◽  
Reaction Time ◽  
Volume Fraction ◽  
Sol Gel ◽  
Reaction Times ◽  
Dip Coating ◽  
Coating Solution ◽  
Coating Method ◽  
Gel Phase ◽  
Dip Coating Method

ABSTRACTMacroporous silicate thick films were prepared by a sol-gel dip-coating method accompanied by the phase separation using methyl-trimethoxysilane (MTMS), nitric acid and dimethylformamide (DMF) as starting components. The morphology of the film varied to a large extent depending on the time elapsed after the hydrolysis until the dipping of the coating solution. On a glass substrate, the films prepared by early dipping had inhomogeneous submicrometer-sized pores on the surface of the film. At increased reaction times, relatively narrow sized isolated macropores were observed and their size gradually decreased with the increase of reaction time. On a polyester substrate, in contrast, micrometer-sized isolated spherical gel domains were homogeneously deposited by earlier dippings. With an increase of reaction time, the volume fraction of the gel phase increased, then the morphology of the coating transformed into co-continuous gel domains and macropores, and finally inverted into the continuous gel domains with isolated macropores. The overall morphological variation with the reaction time was explained in terms of the phase separation and the structure freezing by the forced gelation, both of which were induced by the evaporation of methanol during the dipping operation.

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