scholarly journals Ring-opening Reactions of Cyclic Ethers. IX. Molecular Weight Distribution of Adducts in the Acid-catalyzed Reactions of Epichlorohydrin with Alcohols

1976 ◽  
Vol 49 (6) ◽  
pp. 1638-1641 ◽  
Author(s):  
Shizen Sekiguchi ◽  
Yasushi Hasegawa ◽  
Kenji Nakamura ◽  
Kohji Matsui ◽  
Kensuke Nagahama
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Ring Opening ◽  
Cyclic Ethers ◽  
Ring Opening Reactions ◽  
Acid Catalyzed ◽  
Catalyzed Reactions

29Si NMR Study of Distribution of Oligomers in Polycondensation of Tetraethoxysilane

1996 ◽  
Vol 61 (5) ◽  
pp. 691-703 ◽  
Author(s):  
Jiří Brus ◽  
Jiří Karhan ◽  
Petr Kotlík
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Sol Gel ◽  
29Si Nmr ◽  
Nmr Study ◽  
Nmr Spectrometry ◽  
Concentration Changes ◽  
Acid Catalyzed ◽  
The Moment

29Si NMR spectrometry has been used to determine the number molecular weight distribution of polymerization degrees of a system of oligomers formed in the sol-gel polycondensation of tetraethoxysilane (TEOS). On the basis of identification of the oligomers, monitoring of the concentration changes during the initial phase of the sol-gel polycondensation, and from the deviations observed between the experimentally determined number molecular weight distribution of polymerization degrees and the Flory-Stockmayer model it has been proved that cyclization represents a significant process in the acid-catalyzed polycondensation with substoichiometric amount of water (ratio of amounts TEOS/H2O = 1 : 1). The cyclization becomes important at the moment when the reaction mixture contains increased amounts of the linear tetramer and pentamer. The cyclization products form a basis for formation of polycyclic, highly condensed building units whose gradual aggregation produces the gel.

scholarly journals Modeling of Molecular Weight Distribution in Ring-Opening Polymerization of l,l-Lactide

2014 ◽  
Vol 53 (18) ◽  
pp. 7333-7342 ◽  
Author(s):  
Yingchuan Yu ◽  
Eric J. Fischer ◽  
Giuseppe Storti ◽  
Massimo Morbidelli
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Ring Opening ◽  
Ring Opening Polymerization
Sign in / Sign up

Export Citation Format

Share Document