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.
Highlights
In the past 20 years, the development of polymer synthesis technology has brought convenience to the preparation of polymers with different topologies, such as linear, grafted, branched, and ring-shaped.Intensive studies have shown that under certain conditions, existing polymers with different structures can self-assemble to form structured aggregates
Polymerization demonstrated that the type of light source has a significant effect on the monomer conversion, Firstly, blue light plays a vital role in the photo-BIT-radicalfor polymerization (RDRP) system
We have synthesized a water-soluble macroinitiator mPEG1k-BPA and realized a one-step in situ photo-BIT-RDRP-Polymerization-induced self-assembly (PISA) process under irradiation with blue light-emitting diode (LED) light at room temperature, successfully obtaining mPEG1k-b-PBnMA and mPEG1k-b-PHPMA amphiphilic block copolymer micelles in situ. This strategy effectively improves the problem of the active chain end (CI) loss caused by two-step bromine-iodine transformation RDRP-PISA process, and greatly simplifies the synthesis step, which provides a promising method for the synthesis of polymeric nanoparticles by photo-BIT-RDRP-PISA strategy
Summary
Intensive studies have shown that under certain conditions, existing polymers with different structures can self-assemble to form structured aggregates. Among these polymers, the linear block copolymer has the simplest structure, so the investigation of its self-assembly behaviour is the most extensive and in-depth [1,2]. The self-assembly of block copolymers has a wide range of applications in materials, chemistry, nanoscience, and biomedicine [3,4]. In the conventional method, obtain a better nanostructure morphology, the concentration the block copolymer solution needs to in order to obtain a better nanostructure morphology, theofconcentration of the block copolymer be highly diluted [5,6], which limits its potential application
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