Investigation of the Multimer Cyclization Effect during Click Step-Growth Polymerization of AB-Type Macromonomers

Abstract

In this work, by combining size exclusion chromatography (SEC) and liquid chromatography at the critical condition (LCCC) techniques, we have studied the multimer cyclization effect during click step-growth polymerization of AB-type macromonomers. First, by atom transfer radical polymerization (ATRP), we have synthesized a series of alkynyl and azide functional AB-type polystyrene macromonomers with different molar masses, i.e., PS n . Second, via the click step-growth polymerization of a PS n macromonomer in dimethylformamide (DMF) at varied reaction concentrations (Cs), we have prepared polyaddition products [(PS n ) m ] with large polydispersity indices, where m represents the average degree of polymerization of the macromonomer. Further, narrowly distributed fractions have been obtained by SEC fractionation. Third, we have quantitatively analyzed how the macromonomer molar mass, reaction concentration, and multimer molar mass influence the percentage of a cyclic topoisomer (wtcyclic) for (PS n ) m samples. In particular, we have established the relation between wtcyclic and C for unfractionated (PS n ) m , i.e., wtcyclic = 0.86–0.32 log C, and the relation between wtcyclic and m for fractionated (PS n ) m prepared at a constant C = 100 g/L, i.e., log wtcyclic = −0.46m + 0.16. For the first time, our result has unambiguously pointed out that neither a cyclic topoisomer nor a linear topoisomer can be ignored when considering the structure–property quantitative relationship for polyaddition products.

Modeling Degradation of Thioester Networks Controlled by Oligomer Structures and Thiol–Thioester Exchange

“…While Figure evaluates the degradation of a monodisperse network, past theory , and experimental studies have shown that synthesized oligomers are often a polydisperse distribution of chain lengths. As oligomer distribution has been to shown to impact mass loss in traditional polymer networks, − this work investigated how dispersity in a thioester oligomer would influence degradation.…”

“…Several simplifying assumptions were made to develop this model: (i) the polymers under consideration formed ideal distributions, (ii) the kinetic coefficient for the TTE remained constant throughout degradation and for every thioester in the network, (iii) completely cleaved segments diffused nearly immediately out of the degrading network, and (iv) no further TTE reactions occurred in cleaved segments. These assumptions will not hold for all networks, such as in thick samples, systems with significant oligomer cyclization, 50 systems with pendant chain and cycle formation during polymerization, 49 and systems with nonisothermal exchange reactions that impact the reaction rate constant. 23 Structural Component of the Model.…”

Nickel-Catalyzed Azide–Alkyne Click Polymerization toward 1,5-Regioregular Polytriazoles

“…A turnaround took place in 2002 when the Cu­(I)-catalyzed azide–alkyne cycloaddition (CuAAC) was reported independently by Sharpless et al and Meldal et al , As a typical click reaction, CuAAC could produce sole 1,4-disubstituted 1,2,3-triazoles in excellent yields under mild conditions, which has been developed into a useful polymerization technique, i.e., Cu­(I)-catalyzed azide–alkyne click polymerization (CuAACP) . Thanks to its remarkable click features, CuAACP has been widely used for the preparation of 1,4-regioregular polytriazoles (PTAs) with advanced structures and desired functional properties, which could serve as biomaterials, photoelectric materials, nonlinear optical materials, shape memory materials, self-healing materials, − and so on. To avoid the detriment of the residue metallic species to the optoelectronic and bioapplication of the product, metal-free click polymerization (MFCP) of azides and alkynes was also reported by our groups for the preparation of 1,4-regioregular PTAs …”