Reduced viscosity stoichiometry

Polyelectrolyte complexation in aqueous solution between PEI and PMAA has been studied through viscometry, conductometry, potentiometry, and IR spectroscopy [90]. Upon addition of increasing concentrations of PMAA to an aqueous PEI solution, viscosity dropped suddenly around a 1 to 4 ratio of PMAA to PEI because of the complexation and subsequent coiling of the complexed chains. Reduced viscosity then rose past this ratio indicating that the stoichiometry of the complex occurs in a 1 4 (PMAA groups PEI groups) formation. Conductance and titration experiments agreed with this theory. The... 

To improve the toughness and reduce the viscosity of BMI, allyl compounds, diamine, or other compounds have been used as BMTs modifier. High-performance RTM bismaleimide resin with low cure temperature and post-cure temperature ( 200°C) based on BMI and A-aUyl diaminodiphenylether (DDO) was prepared (Gu 2005). The effect of DDO and its stoichiometry on the performance of the modified resin showed that the resulting resin has good processing characteristics, meeting the requirements of the RTM technique moreover, after cured and post-cured... 

Hadjichristidis and coworkers [228] have investigated the use of initiator 90 for the polymerization of isoprene using a variety of ratios of [scc-BuOLi]/ [CLi]. When this ratio was increased from 1 to 14, the polydispersity decreased from 1.20 to 1.03. In all cases the molecular weight distribution was monomodal. However, when this ratio was 8, a pale red color remained throughout the reaction, implying that unreacted initiator remained. When the ratio was 14, the red color disappeared and the viscosity was reduced as expected for the formation of cross-associated aggregates of the poly(butadie-nyl)lithium chain ends with the lithium sec-butoxide. These results confirm the earlier conclusion that the bimodal molecular weight distributions do not result from inexact stoichiometry [226], but are a consequence of chain end association effects [88]. 

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