Formation of long sub-chain hyperbranched poly(methyl methacrylate) based on inhibited self-cyclization of seesaw macromonomers

Abstract

Well-defined" long-subchain hyperbranched poly(methyl methacrylate) (lsc-hp PMMA) was obtained under the reaction condition in disfavor of self-cyclization of seesaw macromonomer as well as triggered by the intrinsic hindrance of 1,1disubstituted chain ends of seesaw macromonomer. Firstly, seesaw-type alkynyl-(PMMA-Br)2 with one alkynyl group at the chain center and two bromine groups at each chain end was synthesized by atom transfer radical polymerization (ATRP). After the azidation of alkynyl-(PMMA-Br)2, seesaw macromonomer of alkynyl-(PMMA-N3)2 underwent click reaction under high concentration in a good solvent to produce lsc-hp PMMA, almost without intrachain cyclization of macromonomer. Compared with our previous reports, steric hindrance of 1,1-disubstituted MMA units endowed almost no self-cyclization of alkynyl-(PMMA-N3)2 macromonomer. Therefore, lsc-hp PMMA with exact subchain length were obtained except the polydispersity of overall molecular weight. The chemical structure of lsc-hp PMMA was fully confirmed through the combination of gel permeation chromatography (GPC) with different detectors, proton nuclear magnetic resonance spectroscopy and Fourier transform infrared analyses. Furthermore, the formation kinetics for lsc-hp PMMA was monitored based on GPC with multi-angle laser light scattering detector and followed the equation: ln[(DPw + 1)/2] = [A]0kAB,0(1 -e -αt )/α, where DPw is absolute weight-average amount of macromonomers in hyperbranched polymers."Well-defined" hyperbranched PMMA almost without self-cyclization was obtained through click reaction, facilitated by high concentration, good solvent and di-substituted chain-ends.

A Humidity‐Induced Nontemplating Route toward Hierarchical Porous Carbon Fiber Hybrid for Efficient Bifunctional Oxygen Catalysis

“…Here, we succeeded in producing an HPC hybrid with distinct mesopores and interconnected cavity structures by carefully controlling the ingredient of polymer precursor and electrospinning environment. It is worth noting that, similar to the as‐prepared hyperbranched PI, many other polymers, such as polyethylene, [ 47 ] poly (methyl methacrylate), [ 48 ] and polyurethane, [ 49 ] can also be synthesized with controllable hyperbranched structures and hydrophobicity. Therefore, we believe that this template‐free strategy can be extended as a general strategy to prepare 1D HPCs.…”

Long‐Chain Hyperbranched Polymers: Synthesis, Properties, and Applications

“…Although LCHBPs now remain in a nascent stage when compared with well‐developed conventional HBPs with short subchains, many synthetic approaches have been developed . In situations where “living” or controlled polymerizations such as anionic polymerization, ring opening polymerization (ROP), nitroxide mediated polymerization (NMP), atom transfer radical polymerization (ATRP), or reversible addition‐fragmentation chain transfer (RAFT) polymerization are usually utilized to afford AB x ( x ≥ 2) or A x (B x , x ≥ 3) macromonomers bearing various reactive functional groups.…”

“…According to the different structures of AB x macromonomer, this strategy may be categorized into two main methods. One is based on a linear polymer AB x macromonomer with one A end group and x B groups at the other end, where x is a defined number greater than or equal to two . In contrast, the AB x macromonomer in the other method is composed of one A group at either end of the polymer chain and varying amount of B pendant groups .…”

“…Theoretically, AB x macromonomers with the amount of B end groups or x value varying from 2 to 3 to 4 and even larger number might be much easier to generate LCHBPs, but the drawback is increased synthetic difficulty of AB x macromonomer with a larger x value, and increased probability to intra‐chain cyclization. Therefore, the AB 2 strategy acts as the most popular and even exclusive method usually used to synthesize LCHBPs, although others may work well on conventional HBPs from small molecular AB x monomers. In this method, the AB 2 macromonomers are first prepared by a combination of “living” or controlled polymerization and subsequent end group functionalization.…”

“…In order to synthesize LCHBPs, a variety of methodologies have been developed, although in most cases long‐chain AB x ( x ≥ 2) macromonomer building blocks are needed, analogous to that in preparing classical HBPs with small molecular AB x monomers, where the group A can react with the B group . Moreover, LCHBPs can also be easily afforded through certain copolymerizations by using high molecular weight macromonomers or small molecular monomers, or simultaneously both, as building blocks via A 2 + B x ( x ≥ 3) or AB + AB x ( x ≥ 2) copolymerization process .…”