Stereoregular poly(methyl methacrylate) with double-clickable ω-end: synthesis and click reaction

Abstract

Isotactic and syndiotactic poly(methyl methacrylate)s with orthogonally double-clickable terminal ends, that is, α,β-unsaturated ester for Michael addition-type thiol-ene reaction and azide or alkynyl groups for azide-alkyne click reaction, were prepared via terminating reaction of stereospecific anionic polymerization with propargyl and 2-chloroethyl α-(chloromethyl)acrylates. The subsequent polymer modification via double click reaction proceeded quantitatively in one -pot system under ambient conditions. The facile and almost quantitative double-end-functionalization would open a new material design based on stereoregular PMMAs with controlled molecular weights.

Termination of Living Anionic Polymerization of Butyl Acrylate with α‐(Chloromethyl)acrylate for End‐Functionalization and Application to the Evaluation of Monomer Reactivity

“…[ 42 ] ECMA was synthesized according to our previous reports. [ 37 ] Other reagents were used as purchased without further purifi cation.…”

“…[17][18][19][20] In general, there are two approaches to end-functionalization. The fi rst strategy is that α-(halomethyl)acrylate [ 37 ] and α-(alkoxymethyl) acrylate [ 39 ] functioned as an effi cient terminator in stereospecifi c anionic polymerizations of methyl methacrylate (MMA); the poly(methyl methacrylate) (PMMA) living anion attacks the vinylidene group of the terminators, and the subsequent elimination of halogen atom or alkoxy group generates PMMA with α,β-unsaturated ester moiety at the ω-end. For example, the polymerization initiated by isopropyl α-lithioisobutyrate (Li-i PrIB) in the presence of ethylaluminum bis(2,6-di-tert -butylphenoxide) [EtAl(ODBP) 2 ] could be terminated with ethyl α-(chloromethyl)acrylate (ECMA) to afford highly syndiotactic ( st -) PMMA with ω-functionality (termination effi ciency: F ≈ 99%).…”

“…For example, the polymerization initiated by isopropyl α-lithioisobutyrate (Li-i PrIB) in the presence of ethylaluminum bis(2,6-di-tert -butylphenoxide) [EtAl(ODBP) 2 ] could be terminated with ethyl α-(chloromethyl)acrylate (ECMA) to afford highly syndiotactic ( st -) PMMA with ω-functionality (termination effi ciency: F ≈ 99%). [ 37 ] Furthermore, the incorporated α,β-unsaturated ester moiety allows quantitative postpolymerization modifi cation to incorporate ω-functional groups such as amino, hydroxyl, and carboxylic group via base-catalyzed thiol-ene reactions, one of the widely practiced click reactions. [ 37 ] In general, since a living polymer anion of polyacrylate has lower nucleophilicity than that of polymethacrylate, the end-functionalization of polyacrylate living anion through termination is expected to be more diffi cult.…”

“…[ 37 ] Furthermore, the incorporated α,β-unsaturated ester moiety allows quantitative postpolymerization modifi cation to incorporate ω-functional groups such as amino, hydroxyl, and carboxylic group via base-catalyzed thiol-ene reactions, one of the widely practiced click reactions. [ 37 ] In general, since a living polymer anion of polyacrylate has lower nucleophilicity than that of polymethacrylate, the end-functionalization of polyacrylate living anion through termination is expected to be more diffi cult. On the other hand, it is reported that polyacrylate living anion can attack to MMA in the presence of EtAl(ODBP) 2 , because MMA, which has relatively lower reactivity, is activated by the coordination of EtAl(ODBP) 2 .…”

“…We have been interested in the polymerization behavior of α-substituted acrylates [37][38][39] and recently have found…”