Abstract
A series of all-acrylic poly(lauryl acrylate)–poly(benzyl acrylate) (PLA–PBzA) diblock copolymer nanoparticles are prepared by reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization of benzyl acrylate in n-heptane, n-dodecane, or isohexadecane. As the PBzA block grows from the soluble PLA block it eventually becomes insoluble, which drives in situ polymerization-induced self-assembly (PISA). High monomer conversions (>99%) can be achieved and high blocking efficiencies are observed using 1H NMR spectroscopy and gel permeation chromatography, respectively. However, final Mw/Mn values range from 1.36 to 2.10, which suggests that chain transfer to polymer occurs in these all-acrylic PISA formulations. The soft, film-forming nature of these all-acrylic nanoparticles makes conventional TEM studies problematic. However, inspecting the visual appearance of these dispersions combined with DLS studies allows the construction of a phase diagram, which has been validated by cryo-TEM studie...
Highlights
The reversible addition-fragmentation chain transfer (RAFT) solution polymerization of benzyl acrylate (BzA) in toluene results in a slightly higher Mw/Mn value than the equivalent dispersion polymerization in n-heptane
A series of PLA−PBzA diblock copolymers have been prepared via RAFT dispersion polymerization in n-alkanes, with high monomer conversions being achieved for syntheses conducted at 15−40% w/w solids
This led to the construction of a phase diagram based on the visual appearance of the various dispersions combined with dynamic light scattering (DLS) data, rather than the extensive Transmission Electron Microscopy (TEM) studies described in earlier polymerization-induced self-assembly (PISA) studies
Summary
Dispersion polymerization has provided a facile route to well-defined, colloidally stable latexes in non-polar solvents via addition of a suitable steric stabilizer usually an adsorbed homopolymer, block copolymer, or graft copolymer.[1]In contrast to emulsion polymerization, the monomer is soluble in the solvent and the initial reaction mixture is homogeneous: polymerization leads to the formation of an insoluble polymer, which leads to nucleation and to sterically stabilized latex particles (usually in the 0.1−10 μm size range).[2−6]Dispersion polymerization was originally developed for paints and coatings applications,[7] but the relatively narrow particle size distributions[8,9] led to a broader range of applications ranging from biomedical assays to particulate modeling.[7,10−13] It is wellknown that AB diblock copolymers can self-assemble to form micelles in a solvent that is selective for one of the blocks.[14−24] A wide range of copolymer morphologies are known,[25] but postpolymerization processing (such as a solvent or pH switch,[26] thin film rehydration,[27−29] or electroformation30) is usually required, with this additional step normally being conducted at relatively high dilution (typically
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