title: Terminal index: a new way for precise description of topologic structure of highly branched polymers derived from A2 + B3 stepwise polymerization.
abstract: Terminal index (TI) was presented as a new characteristic parameter for quantitative description of branched and cyclic topology of highly branched soluble polymers derived from A2 + B3 stepwise polymerization. TI is defined as the ratio of terminal units of an A2 + B3 type highly branched polymer to those in its perfect hyperbranched counterpart. TI is concisely represented as T/(D + L), which can be conveniently calculated from a quantitative NMR spectrum. The model of soluble A2 + B3 type polymers is suggested as an intermediate between multicyclic polymers and perfect hyperbranched polymers. The TI ranges between 0 and 1 where a higher TI indicates a perfect hyperbranched topology while a low TI indicates a multicyclic structure. The analysis of soluble A2 + B3 type polyesters and polycarbosilanes as model polymers demonstrates that TI as a more precise parameter, along with degree of branching, can be generally applied to understand the fine topology of highly branched polymers derived from A2 + B3 polymerization.
authors.affiliation: Key Laboratory of Space Applied Physics and Chemistry of Ministry of Education, Department of Applied Chemistry, School of Science, Northwestern Polytechnical University , Xi'an, 710072, P. R. China.
authors.forename: Heng
authors.initials: H
authors.lastname: Chen
authors.forename: Jie
authors.initials: J
authors.lastname: Kong