Amorphous phase separation

Wood Hill (1991b) induced phase-separation in the clear glasses by heating them at temperatures above their transition temperatures. They found evidence for amorphous phase-separation (APS) prior to the formation of crystallites. Below the first exotherm, APS appeared to take place by spinodal decomposition so that the glass had an intercoimected structure (Cahn, 1961). At higher temperatures the microstructure consisted of distinct droplets in a matrix phase. 

Cite the following fact to illustrate the difficulties in the phase analysis of polymer systems. For the poly(vinyl alcohol)- -water system, some researchers propose a state diagram of amorphous phase separation with an upper critical solution temperature, others — ainor]>hons separation with a lower critical solution temperature about 100 C there are some who think that there is no region of amorphous separation below 150 -instead, they observe liquid-crystal phase separation. Such are the discrepancies on the basic question of thermodynamics ... 

Ronarc h, D., Audren, P. et al, (1985) Amorphous phase separation in propylene block copolymers as revealed by thermostimulated depolarization measurements, I. Complex spectra study, /. Appl. Phys., 58, 466 73. 

Solid-state characterization of amorphous solid dispersion systems prepared by HME is essential to understand their physical behavior. Several tools and techniques to detect physical failure modes such as crystallization or amorphous-amorphous phase separation will be outlined with an emphasis on the strengths and weaknesses of each approach. Characterization tools such as thermal methods may help to inform process development, specifically the phase diagram, inherent restrictions in processing space, and potential thermal liabilities. Finally, approaches aimed at understanding the fundamentals of amorphous solid dispersions will be discussed. In particular, tools and techniques which offer insight into the thermodynamics and molecular mobility of amorphous systems will be emphasized. 

Detection of Crystallization and Amorphous-Amorphous Phase Separation... 

Okay Oguz. Macroporous copolymer networks. Prog. Polym. Sci. 25 no. 6 (2000) 711-779. Padilla Adora M., Chou Shin G., Luthra Sumit, and Pikal Michael J. The study of amorphous phase separation in a model polymer phase-separating system using Raman microscopy and a low-temperature stage Effect of cooling rate and nucleation temperature. J. Pharm. Sci. 100 no. 4 (2011) 1362-1376. 

Adachi T., Sakka S. Microstructural changes in sol-gel derived silica gel monolith with heating as revealed by the crack formation on immersion. J. Ceram. Soc. Jpn. 1989 97 203-207 Adachi T., Sakka S. Dependence ofthe elastic moduli of porous silica gel prepared by the sol-gel method on heat treatment. J. Mater. Sci. 1990 25 4732 737 Chen A., James P.F. Amorphous phase separation and crystallization in a lithium silicate glasses prepared by the sol-gel method. J. Non-Cryst. Solids 1988 100 353-358 Chen M., Lee W.E., James P.F. Preparation and characterization of alkoxide-derived celsian glass-ceramic. J. Non-Cryst. Solids 1991 130 322-325 Chen M., James P.F., Lee W.E. Densificaation and crystallization of celsian glass derived from alkoxide gel. J. Sol-Gel Sci. Tech. 1994a 2 233-237... 

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