One-Step Photocontrolled Polymerization-Induced Self-Assembly (Photo-PISA) by Using In Situ Bromine-Iodine Transformation Reversible-Deactivation Radical Polymerization

Abstract

Polymerization-induced self-assembly (PISA) has become an effective strategy to synthesize high solid content polymeric nanoparticles with various morphologies in situ. In this work, one-step PISA was achieved by in situ photocontrolled bromine-iodine transformation reversible-deactivation radical polymerization (hereinafter referred to as Photo-BIT-RDRP). The water-soluble macroinitiator precursor α-bromophenylacetate polyethylene glycol monomethyl ether ester (mPEG1k-BPA) was synthesized in advance, and then the polymer nanomicelles (mPEG1k-b-PBnMA and mPEG1k-b-PHPMA, where BnMA means benzyl methacrylate and HPMA is hydroxypropyl methacrylate) were successfully formed from a PISA process of hydrophobic monomer of BnMA or HPMA under irradiation with blue LED light at room temperature. In addition, the typical living features of the photocontrolled PISA process were confirmed by the linear increase of molecular weights of the resultant amphiphilic block copolymers with monomer conversions and narrow molecular weight distributions (Mw/Mn < 1.20). Importantly, the photocontrolled PISA process is realized by only one-step method by using in situ photo-BIT-RDRP, which avoids the use of transition metal catalysts in the traditional ATRP system, and simplifies the synthesis steps of nanomicelles. This strategy provides a promising pathway to solve the problem of active chain end (C-I) functionality loss in two-step polymerization of BIT-RDRP.

RAFT-mediated polymerization-induced self-assembly (RAFT-PISA): current status and future directions

“…Initially, only photo-RAFT have been implemented in the PISA process. More recently, other RDRP techniques, such as NMP, 125 ATRP, 75 and bromine–iodine transformation (BIT), 80 as well as some other polymerization techniques such as ring-opening polymerization 126 have been explored for the photo-PISA process. Nevertheless, the photo-RAFT technique remains the most robust and widely employed technique for the photo-PISA process.…”

“…[65][66][67][68][69][70] Theoretically, all RDRP techniques can produce block copolymer nano-objects via PISA. Indeed, many examples of PISA process using different RDRP techniques have been reported, including reversible addition-fragmentation chain transfer (RAFT) polymerization, nitroxide-mediated polymerization (NMP), [71][72][73] atom transfer radical polymerization (ATRP), [74][75][76][77] iodine-transfer polymerization (ITP), 78 bromineiodine transformation reversible-deactivation radical polymerization (BIT-RDRP), 79,80 telluride-mediated radical polymerization (TERP), 81 cobalt-mediated radical (CMR) polymerization 82 and reversible complexation mediated polymerization (RCMP); 83,84 other polymerization techniques such as ringopening metathesis polymerization (ROMP) [85][86][87][88][89] have been implemented as well. However, RAFT remains the most employed and robust technique for PISA due to its high compatibility with various monomers, solvents and reaction conditions.…”

Principles and Characteristics of Polymerization-Induced Self-Assembly with Various Polymerization Techniques

“…A similar procedure based on a light-driven bromide-iodine transformation was reported for an in situ generation of an iodine initiator around the same time. 133,134 The subsequent polymerization at room temperature led to the in situ formation of spheres and vesicles.…”

Modern Trends in Polymerization-Induced Self-Assembly

“…Besides OMRP, cobalt-mediated radical polymerization (CMRP) and bromine-iodine transformation (RDRP) were applied in PISA [267][268][269]. For example, N-vinyl-imidazolium-type monomers were involved in aqueous CMRP to produce block copolymers that self-assembled in the course of the synthesis (Scheme 21) [267].…”