One‐Step Synthesis of Dendritic Highly Branched Polystyrenes by Organotellurium‐Mediated Copolymerization of Styrene and a Dienyl Telluride Monomer

Abstract

Dendritic highly branched polystyrenes (HB-PSts) were prepared by ao ne-step copolymerization of dienyl telluride 6 and St in the presence of organotellurium chain transfer agent 2.T he molecular weight (MW), dendritic generation, and branching density were easily controlled by the ratio of 2 to 6 to styrene (St) with maintaining monodispersity.The branching efficiency estimated by adeuteriumlabeling experiment showed that 6 quantitatively (> 95 %) served as the branching point. The end group fidelity was high (ca. 90 %) as determined by the end group transformation to pyrene-derivative.I ntrinsic viscosity of the HP-polystyrenes was significantly lower than that of linear polystyrenes and were easily tuned by the branching number and branching density.The method is compatible of various functional groups and chloro and acetoxy-substituted styrenes were also used as ac omonomer.Atadpole blockc opolymer was also synthesized starting from linear PSt as amacroinitiator.Highly branched polymers (HBPs) have attracted ag reat deal of attention owing to their unique topological structure associated with characteristic physical properties,s uch as alower intrinsic viscosity,lower glass transition temperature, and alarger number of terminal groups than the corresponding linear polymers. [1] Therefore,H BPs are promising for various applications including lubricants,c oatings,d rugdelivery vehicles,a nd catalysts. [2] However,t he development of ap ractical method for synthesizing structurally controlled HBPs has been asignificant challenge.Among HBPs,d endrimers and dendrons are the most precisely controlled three-dimensional (3D) structures,t hat is,m olecular weight, dispersity,b ranching number, and branching density.H owever, the necessity of am ultistep synthesis limits their applications in materials science. [3] In contrast, hyperbranched polymers can be easily synthesized by one-step methods,s uch as 1) the step-growth polycondensation of AB n monomers and the copolymerization of A 2 and B n monomers,i nw hich Aa nd Br efer to two functional groups that react with each other and nrepresents the numbers of Bg roups, [4] and 2) self-condensing vinyl (co)polymerization (SCV(C)P) and self-condensing ringopening polymerization using the AB* monomer,i nw hich

Synthesis of Structurally Controlled, Highly Branched Polymethacrylates by Radical Polymerization through the Design of a Monomer Having Hierarchical Reactivity

“…Furthermore, the method was extended to the synthesis of HB polystyrene (R 3 = Ph, R 4 = H) using 4aB (X = TeMe, R 1 = H, R 2 = C(CH3)=CH2) as a comonomer. 28 Our method uses radical polymerization, which is characterized by its high versatility in monomer species and can be extended to other important monomer classes, such as methacrylate derivatives (R 3 = CO2R, R 4 = CH3). However, extension of the use of 4aA and 4aB to methacrylates has been unsuccessful thus far (see below).…”

Recent advances on synthesis and biomaterials applications of hyperbranched polymers

“…In this study, new monomers, such as α‐bromo acrylates (Inibramer 1, Table 1) and α‐bromo styrenes, were used, where the initiating function of alkyl bromide was only enabled after the incorporation of monomer into polymer to convert the vinyl group to alkyl group so to effectively disable monomer‐monomer reactions in the polymerization (Li et al, 2019). Conditions have also been reported in the SCVP of AB 2 vinyl‐telluride monomers which follow the same pattern of initiator switching from inactive to active after vinyl radical addition (Inibramer 2, Table 1; Lu & Yamago, 2019).…”

“…To alter this scenario, two special inimers, for example, vinyl tellurides and vinyl bromides, were separately designed, which could switch the reactivity of inimer initiating groups from dormant to active only after the reaction of vinyl group occurs. Vinyl tellurides were first reported in 2017 by Yamago group as the alkyl telluride initiating group was only turned on to be active after the vinyl group participated in the polymerization, achieving selective polymer–inimer reaction to produce hyperbranched structure with functionalizable alkyl telluride chain ends (Scheme 2, Figure 1c; Lu et al, 2017; Lu & Yamago, 2019). More recently, Zhong group designed a vinyl bromide inimer, termed inibramers to distinguish from traditional inimers, which exhibited a chain‐growth ATRP to produce hyperbranched polymers with alkyl bromide compositions.…”

Synthesize Hyperbranched Polymers Carrying Two Reactive Handles via CuAAC Reaction and Thiol–Ene Chemistry

“…As precision synthesis has become a popular topic in polymer chemistry and materials, it is intriguing to find more research groups have showed interest to develop chain‐growth polymerization methods to achieve controlled synthesis of HBPs in one pot. These examples include i) the slow addition into dilute core method, ii) the use of a pair of B m core and AB n ( m , n ≥ 2) monomer with unequal reactivity of B group, iii) the use of monomers with to‐be‐activated initiating group to achieve polymerization‐induced branching …”

“…These examples include i) the slow addition into dilute core method, [17][18][19][20][21] ii) the use of a pair of B m core and AB n (m, n ≥ 2) monomer with unequal reactivity of B group, [22][23][24] iii) the use of monomers with to-be-activated initiating group to achieve polymerizationinduced branching. [25][26][27] In addition, efficient and quantitative installation of guest molecules onto selective domain of these HBP scaffolds was very difficult, which typically relies on chemical conjugation. Albeit dendritic polymers inherit abundant surface functional sites from their polymerization process, introduction of internal multi-functionality is synthetically complex and less reliable due to severe steric congestion.…”