Group‐Transfer Polymerization‐Induced Self‐Assembly (GTPISA) in Non‐polar Media: An Organocatalyzed Route to Block Copolymer Nanoparticles at Room Temperature

Abstract

Polymerization‐induced self‐assembly (PISA) enables the synthesis at large scale of a wide variety of functional nanoparticles. However, a large number of works are related to controlled radical polymerization (CRP) methods and are generally undertaken at elevated temperatures (>50 °C). Here is the first report on methacrylate‐based nanoparticles fabricated by group transfer polymerization‐induced self‐assembly (GTPISA) in non‐polar media (n‐heptane). This GTPISA process is achieved at room temperature (RT) using 1‐methoxy‐1‐(trimethylsiloxy)‐2‐methylprop‐1‐ene (MTS) and tetrabutylammonium bis‐benzoate (TBABB) as initiator and organic catalyst, respectively. Under these conditions, well‐defined metal‐free and colorless diblock copolymers are produced with efficient crossover from the non‐polar stabilizing poly(lauryl methacrylate) (PLMA) block to the non‐soluble poly(benzyl methacrylate) (PBzMA) segment. The resulting PLMA‐b‐PBzMA block copolymers simultaneously self‐assemble into nanostructures of various sizes and morphologies. GTPISA in non‐polar solvent proceeds rapidly at RT and avoids the use of sulfur or halogenated compounds or metallic catalysts associated with the implementation of CRP methods, thus expanding the potential of PISA formulations for applications in non‐polar environments.

Engineering Methacrylic Block Copolymers by Organic Catalysis Group Transfer Polymerization-Induced Self-Assembly in Nonpolar Media at Room Temperature

“…The GTP of SMA went to completion within 180 min, as evidenced by a monitoring of the reaction by 1 H NMR analysis. Note that the GTP route generally leads to faster reactions than RAFT polymerizations, while maintaining very good control until complete monomer conversion. , A typical 1 H NMR spectrum of a GTP-derived PSMA precursor is shown in Figure A (bottom). The ratio of the integrals of the methyl signals assigned to the PSMA end group, as detected at 3.65 ppm, to those of the signals due to the oxymethylene protons of SMA units appearing at 3.9 ppm allowed us to determine the average degree of polymerization of this polymer precursor, namely, DP n ,PSMA = 16, in excellent agreement with the expected value DP n ,th = 15.…”

“…In both cases, the blocking efficiency was improved as attested by lower dispersity values and absence of the parent PLMA precursor, in comparison to SEC traces of PLMA 30 -b-PMMA 25 and PLMA 30 -b-PMMA 50 (Figure 4B vs Figure 6A). For instance, the latter copolymer synthesized using rapid addition (0.07 mL/min) gave a dispersity of 1.35, against a D̵ value of 1.25 (Figure 4 and Table 2, runs 3 and 10) for the PLMA 30 copolymers gave stable dispersions of nanoparticles with an average diameter of 32 nm (PDI = 0.113) and 37 nm (PDI = 0.05), as determined by DLS, while TEM images showed spherical morphologies in both cases (see Figure S3).…”

“…In this context, we have recently developed a new synthetic approach to self-stabilized methacrylic-based polymeric nanoparticles in nonpolar media, at the crossroads of the GTP method and the polymerization-induced self-assembly (PISA) process. 30 PISA is a fast-developing research area as this process allows for a facile and direct design of functional nanoparticles of wide-ranging sizes and morphologies. 31−51 The ability to carry out a PISA process at relatively high solid contents, without the need for an external surfactant, is also particularly advantageous.…”

“…78,79 Therefore, in order to overcome some of the limitations of CRP methods and/or to achieve nanoparticles in a variety of dispersion solvents under mild conditions, further developments in the field of PISA formulations are still needed. The synthetic methodology we reported, 30 which was abbreviated as GTPISA, differs from many other PISA processes that either use colored and malodorous sulfur-containing controlling agents (RAFT-PISA), or involves a lithium-based initiator in large quantities (LAP-PISA), or concerns limited families of monomers (e.g., ROP-PISA or ROMP-PISA). In our previous work, the proof of concept of GTPISA was established for the synthesis of poly(lauryl methacrylate)-b-poly(benzyl methacrylate) (PLMA-b-PBzMA) diblock copolymers.…”

“…In our previous work, the proof of concept of GTPISA was established for the synthesis of poly(lauryl methacrylate)-b-poly(benzyl methacrylate) (PLMA-b-PBzMA) diblock copolymers. 30 Herein, we wish to exemplify the GTPISA method and describe through a more systematic study that this approach is applicable to a wider range of methacrylic monomers, thus enabling diversification of the structure of both the stabilizing and the core-forming segments of the as-derived nanoparticles. Namely, here we optimize the conditions to elaborate welldefined metal-free and odorless poly(stearyl methacrylate)-bpoly(benzyl methacrylate) (PSMA-b-PBzMA) and poly(lauryl methacrylate)-b-poly(methyl methacrylate) (PLMA-b-PMMA) diblock copolymers dispersed in n-heptane.…”