Polyaddition and polycondensation. Substitution effects in polycondensation systems

Abstract

SynopsisDeviations occur from the classical postulate that all pairs of functionalities in a condensation reaction have equal rates of engaging in bond formation or bond breakage. In so-called first-shell substitution effects, which can be treated most readily, the rates involving functionalities X and Yare influenced at most by the existence or absence of other links borne by the two units to which X and Yare directly attached. Quantitative analyses are made of data on melamine and urea-formaldehyde systems in terms of first-shell substitution effects. 4567

Substitution Effects in Property Relations for Stepwise Polyfunctional Polymerization

“…Conformations of Polymers Attached to an Interface P. G. de Gennes College de France, 75231 Paris Cedex 05, France. Received April 10,1980 ABSTRACT: We discuss the conformations and the concentration profiles for long, flexible chains (N monomers per chain) grafted at one end on a solid surface (fraction of surface sites grafted ). The chains are immersed either in a pure (good) solvent or in a solution of the same polymer (P monomers per mobile chain, volume fraction ).…”

Production and thermal decomposition of polycondensates containing N,N′-disubstituted thiourea derivatives

“…The combination of urea and formaldehyde begins with a series of addition reactions, followed by the condensation of methylol groups in methylol bridges to form methylene ether bridges at higher temperature [8][9][10]. However, the mechanism of a reaction system such as urea-formaldehyde-N,N'-ethylenethiourea-silicon(IV) oxide (1) or urea-formaldehyde-N,N'-diisopropylthiourea-titanium(IV) oxide (2) involves a series of complex polycondensation processes.…”