Synthesis of block or graft copolymers containing poly(styrene derivative) segments by living cationic polymerization using acetal moieties as latent initiating sites

Abstract

Selective acetal-initiated living cationic polymerization was successfully employed for the precision synthesis of block and graft copolymers containing poly(p-methylstyrene) and poly(alkyl vinyl ether) segments. The synthesis involved the living cationic polymerization of p-methylstyrene from the acetal moieties at the chain ends or in the side chains of poly(alkyl vinyl ether). Quantitative initiation of the reaction from the acetal moieties and efficient propagation were achieved via the use of a combined initiating system, TiCl4 and SnCl4, in the presence of ethyl acetate as an added base and 2,6-di-tertbutylpyridine as a proton trap reagent in CH2Cl2 at 0 °C. Appropriate ratios of acetal units, TiCl4, and SnCl4 were indispensable for the quantitative reaction. Solubility and thermal analyses indicated that the properties of the block and graft copolymers were mainly governed by the poly(p-methylstyrene) segments. The synthesis of block and graft copolymers using a more reactive alkoxystyrene was also achieved via the initiation reaction from acetal moieties.

Synthesis of Highly Defined Graft Copolymers Using a Cyclic Acetal Moiety as a Two-Stage Latent Initiating Site for Successive Living Cationic Polymerization and Ring-Opening Anionic Polymerization

“…In this regard, acetal moieties are possible candidates as reactive sites in prepolymers because of their stability under most nonacidic conditions and the simplicity of their introduction into polymers. In cationic polymerization, acetal compounds have been used as effective initiators of the living polymerization of vinyl ethers (VEs). − Recently, our group demonstrated that quantitative initiation reactions from an acyclic acetal proceeded in the living cationic polymerization of VEs or styrene derivatives using oxophilic metal chlorides such as TiCl 4 . This method was applicable to the synthesis of block or graft copolymers derived from monomers with completely different reactivities using a well-defined macroinitiator containing acetal moieties.…”

Alternating-like Cationic Copolymerization of Styrene Derivatives and Benzaldehyde: Precise Synthesis of Selectively Degradable Copoly(styrenes)

“…The pMeSt–BzA copolymer was demonstrated to exhibit thermal properties comparable to those of the pMeSt homopolymer. Differential scanning calorimetry (DSC) analysis of the copolymer detected a glass-transition temperature ( T g ) of 86 °C, which was a slightly lower value than the T g of a pMeSt homopolymer (109 °C) with a comparable MW (Figure A). In addition, the 5% weight loss temperature ( T d5 ) was 311 °C, as determined by thermogravimetric analysis (TGA) (Figure B).…”

“…(A) DSC thermograms and (B) TGA analysis of poly­(pMeSt- alt -BzA) (the sample in Figure (30 min); M n (GPC, polystyrene calibration) = 15.0 × 10 3 , M n (GPC, light-scattering detector) = 17.1 × 10 3 ) and poly­(pMeSt) (obtained under the conditions reported in ref ; M n (GPC, polystyrene calibration) = 17.2 × 10 3 ). DSC: second heating scan, heating rate = 10 °C/min.…”

Recent Advances in Living Cationic Polymerization with Emerging Initiation/Controlling Systems

“…In 2015, Aoshima and coworkers [ 35 ] first discovered the combination of ZrCl 4 and a salphen ligand could generate HCl in situ and trigger the LCP of IBVE ( Figure ). The bulky counteranion of the Zr‐complex could provide steric hinderance from one side of the propagation chain and enable stereoselective polymerization.…”

“…Based on the versatility and high tunability of Lewis acid/base pairs, judicious selection of appropriate combinations of such chemicals has allowed vigorous development of LCP and successfully broadened monomer scope, for example, various vinyl ethers [ 17,20–22 ] and electron‐rich styrenes. [ 15,23,24 ] Besides, rationally designed initiators with functional groups have enabled facile accesses to polymers with desirable physical properties (e.g., self‐aggregation, [ 25–27 ] thermoresponsiveness [ 27,28 ] ), and complex topological architectures including block copolymers, [ 29–31 ] bottlebrush copolymers, [ 27,32–36 ] and star shaped (multiarmed) polymers and others. [ 37–39 ]…”