Chain‐Growth Click Polymerization of AB₂ Monomers for the Formation of Hyperbranched Polymers with Low Polydispersities in a One‐Pot Process

Abstract

Hyperbranched polymers are important soft nanomaterials but robust synthetic methods with which the polymer structures can be easily controlled have rarely been reported. Fort he first time,w ep resent ao ne-pot one-batchs ynthesis of polytriazole-based hyperbranched polymers with both low polydispersity and ah igh degree of branching (DB) using ac opper-catalyzed azide-alkyne cycloaddition (CuAAC) polymerization. The use of atrifunctional AB 2 monomer that contains one alkyne and two azide groups ensures that all Cu catalysts are bound to polytriazole polymers at low monomer conversion. Subsequent CuAACpolymerization displayed the features of a" living" chain-growthm echanism with al inear increase in molecular weight with conversion and clean chain extension for repeated monomer additions.F urthermore,t he triazole group in al inear (L) monomer unit complexed Cu I , which catalyzedafaster reaction of the second azide group to quickly convert the Lunit into ad endritic unit, producing hyperbranched polymers with DB = 0.83.

Synthesis of structurally controlled hyperbranched polymers using a monomer having hierarchical reactivity

“…Therefore, the simple application of living polymerization to HBP synthesis by SCVP and SCVCP has so far been unsuccessful in achieving structural control under cationic 18 , anionic 20 , 21 , radical 22 – 26 , and group transfer polymerization conditions 27 , 28 . HBPs with narrow dispersity were only obtained at low monomer conversion 23 , under specific conditions such as emulsion polymerization to avoid intermicellar reactions 29 or the slow addition technique to avoid the step-growth mechanism 30 , 31 , or through the use of monomers with specific functional groups 32 , 33 . HBPs with a 100% degree of branching have been achieved, but only under specific reaction conditions 34 , 35 and without any molecular weight or distribution control.…”

Recent advances on synthesis and biomaterials applications of hyperbranched polymers

“…When all B groups share the same reactivity either in the monomer state or half-reacted intermediate state, the statistic reaction of B with A produces hyperbranched polymers with DB~0.5, in which the molar fraction of half-reacted linear unit (L) among all monomer units is roughly about 0.5 based on Equation DB = (D + T)/ (D + T + L), in which D stands for fully reacted dendritic unit and T stands for terminal unit with only A group reacted (Scheme 2). Despite this, some special monomers have been designed to deviate this equal reactivity scenario, creating (Zou et al, 2016) Monomer 2 Shi, Cao, Wang, & Gao, 2015; Examples of AB m monomers in step-growth polymerization Monomer 3 (Xue, Finke, & Moore, 2010) Monomer 4 Examples of divinyl monomers in radical polymerization…”

Polymer Synthesis with More Than One Form of Living Polymerization Method

“…A one‐pot controlled chain‐growth copper‐catalyzed azide–alkyne cycloaddition (CuAAC) polymerization has been developed. They utilize a trifunctional AB 2 monomer containing one alkyne group and two azide groups which reacts according to a chain‐growth polymerization pathway . CuAAC is also utilized in combination with SET‐LRP to mediate “click‐radical” concurrent polymerization for the formation of the brush‐like copolymer .…”