Polymer Nanospheres with Hydrophobic Surface Groups as Supramolecular Building Blocks Produced by Aqueous PISA

Abstract

A robust and straightforward synthesis of waterborne polymer nanospheres bearing the supramolecular association unit dialkoxynapthalene at their surface is presented using polymerization-induced self-assembly (PISA). A RAFT agent bearing this unit is first employed to produce poly(acrylic acid) chains, which are then chain-extended with styrene (S) to spontaneously form the nano-objects via RAFT aqueous emulsion polymerization. The particular challenge posed by the dialkoxynapthalene hydrophobicity can be overcome by the use of PISA and the deprotonation of the poly(acrylic acid). At pH = 7, very homogeneous latexes are obtained. The particle diameters can be tuned from 36 to 105 nm (with a narrow particle size distribution) by varying the molar mass of the PS block. The surface accessibility of the dialkoxynapthalene moieties is demonstrated by complexation with the complementary host cyclobis(paraquat-p-phenylene) (CBPQT · Cl ), highlighting the potential of the nanospheres to act as building blocks for responsive supramolecular structures.

RAFT‐Mediated Polymerization‐Induced Self‐Assembly

“…NMP of either St or SSNa was then triggered from the particle surface, thereby leading to morphological changes under certain conditions. Aiming at the synthesis of building blocks for larger supramolecular structures, Ebeling et al . recently reported the synthesis of PS particles carrying naphthalene units that were initially present at the α‐chain end of the macroRAFT agent.…”

“…As an example, raspberry‐like nanoparticles have been produced by the controlled heterocoagulation of PEG‐stabilized and PAA‐stabilized nanoparticles through hydrogen‐bonding interactions between the PAA and PEG chains . More recently, the possibility to functionalize the surface of PS particles by naphthalene units, present at the α‐chain end of the PAA macroRAFT agent, was also demonstrated . The latter particles should be useful as building blocks to construct larger supramolecular structures through host–guest interactions.…”

A study on the preparation of alkyne functional nanoparticlesviaRAFT emulsion polymerisation

“…Similar observations were recently reported by Lansalot and co-workers using hydrophobic naphthalene functionalised macro-RAFT agents. 39 Although, stable latexes with narrow PDi values were obtained with 10, 25 and 50% TMS macro-RAFT agent, the poor molar mass distributions observed could indicate poor consumption of the macro-RAFT agent, and subsequently low level of alkyne functionality at the nanoparticle surface.…”

Polymerization‐Induced Self‐Assembly

“…Other RDRP techniques have also successfully been implemented in the past, such as atom transfer radical polymerization (ATRP), It is well established that the dispersion polymerization mechanism, where the monomer is soluble in the polymerization medium, favours the control over the polymerization and the formation of higher-order morphologies, and is therefore usually preferred over emulsion polymerization. Similarly, the majority of contributions report on dispersion polymerization systems-mostly performed in alcohols, water, or their mixtures-and generally a large variety of morphologies were generated, whereas the rarer examples performed in emulsion [11][12][13][14][15][16] yielded spherical particles apart from the work of Hawkett et al, [15] where nanofibers were formed. The presence of a crosslinker during PISA can also prevent nanoparticle reorganization and inhibit the formation of higher-order morphologies.…”

“…They demonstrated that the epoxy function was much more resistant towards hydrolysis when it was inserted within the polymer chain, than when it was exposed at the α-chain end, and that one single reactive group on average was sufficient to post-functionalize the particles by reaction with primary amines. Aiming at the synthesis of building blocks for larger supramolecular structures, Lansalot, D'Agosto et al [14] reported the possibility to functionalize the surface of polystyrene particles obtained in emulsion polymerization by naphthalene units present again at the α-chain end of the macroRAFT agents. They overcame the challenge to localize an intrinsically hydrophobic moiety at the surface of particles dispersed in water, by using charged polyacrylic acid (PAA) as a stabilizer.…”