Intramolecular Cyclization in A₂ + B₃ Polymers via Step-Wise Polymerization Resulting in a Highly Branched Topology: Quantitative Determination of Cycles by Combined NMR and SEC Analytics

Abstract

In this contribution, we report a convenient expression of average number of cyclic structures (ANC) and cyclic-average molecular weight (M C ) to quantificationally describe the topological defect of intramolecular cyclization in highly branched polymers synthesized via A 2 + B n (n ≥ 3) stepwise polymerization strategy by a combination of nuclear magnetic resonance spectrometry (NMR) and size exclusion chromatography (SEC). The ANC and M C depend on the number ratio of dendritic, linear, terminal units and numberaverage molecular weight of hyperbranched polymers, which can be derived from NMR and SEC, respectively. The analysis of hyperbranched polycarbosilanes with silicon hydrogen bonds (A) or vinyl groups (B) termini from A 2 + B 3 approach indicates that the quantificational description of ANC and MC make it easy to well understand intramolecular cyclic structures resulting in a highly branched topology. Regulating the flexibility and rigidness of internal units in A 2 monomers is an effective way to control the extent of intramolecular cyclization. Because of the general and convenient nature, the ANC and M C have potential for the quantificational description of intramolecular cyclization, i.e. one type of topological defect, in a variety of hyperbranched polymers synthesized via A 2 + B n strategy.

Evolution of surface chemistry and morphology of hyperbranched polysiloxane polyimides in simulated atomic oxygen environment

“…S2 (Supplementary Information). The Mark-Houwink-Sakurada (MHS) exponent is a parameter corresponding to the topology of a polymer in a good solvent [31]. Generally, for hyperbranched polymers, the exponent typically varies from 0.5 to 0.2.…”

Facile synthesis, microstructure and photophysical properties of core-shell nanostructured (SiCN)/BN nanocomposites

“…The first step was the hydrosilylation of the vinyl groups, which gave an explanation to the disappearance of vinyl groups and the decrease in the intensity of Si–H bonds. As the hydrosilation procedure started at 200 °C, almost no change for the intensities of the vinyl and Si–H vibrations were observed in PSBN138. However, the addition of [Co(en) 3 ]·Cl 3 to PSBN1 induced the disappearance of the absorption bands of the alkanes, which demonstrated that the [Co(en) 3 ]·Cl 3 acted as a catalyst for the hydrosilylation.…”

Hyperbranched Polymers with Controllable Topologies for Drug Delivery

“…Among these strategies, A 2 +B 3 ‐type DMM has been widely used to construct the hyperbranched topology. By regulating the feed ratio, Chen et al . outline the synthesis of two kinds of HPs to analyze the degree of intramolecular cyclization.…”