RAFT‐Mediated Emulsion Polymerization‐Induced Self‐Assembly for the Synthesis of Core‐Degradable Waterborne Particles

Abstract

Poly(N-acryloylmorpholine) (PNAM)-decorated waterborne nanoparticles comprising a core of either degradable polystyrene (PS) or poly(n-butyl acrylate) (PBA) were synthesized by polymerizationinduced self-assembly (PISA) in water. A PNAM bearing a trithiocarbonate chain end (PNAM-TTC) was extended via reversible addition-fragmentation chain transfer (RAFT)-mediated emulsion copolymerization of either styrene (S) or n-butyl acrylate (BA) with dibenzo[c,e]oxepane-5-thione (DOT). Well-defined amphiphilic block copolymers were obtained. The in situ self-assembly of these polymers resulted in the formation of stable nanoparticles. The insertion of thioester units in the vinylic blocks enabled their degradation under basic conditions. The same strategy was then applied to the emulsion copolymerization of BA with DOT using a poly(ethylene glycol) (PEG) equipped with a trithiocarbonate end group, resulting in PEGdecorated nanoparticles with degradable PBA-based cores.

Emulsion Polymerization of 2-Methylene-1,3-Dioxepane and Vinyl Acetate: Process Analysis and Characterization

“…To the best of our knowledge, our initial report described the first successful copolymerization of MDO by emulsion polymerization, and many researchers are actively exploring related approaches to degradable latex particles. − , A recent report attempted to replicate our findings and found lower MDO incorporation, leading to scrutiny of our original results and data interpretation . Here, we report additional in-process and final characterization of the copolymerization of VA and MDO, as well as a series of studies reproducing both our initial results and those of other researchers.…”

“…The most well-studied CKA is 2-methylene-1,3-dioxepane (MDO) and recent work by many researchers has led to the development of MDO-based and ester bond-containing degradable polymers for functional coatings and interfaces, − nanoparticles, , drug delivery, , and a variety of other applications where degradability is desired. − MDO is synthesized from commodity starting materials in good yields and has been produced industrially in the past. − However, MDO and other related CKA derivatives suffer from a variety of problems including unfavorable reactivity ratios with other monomers, − the potential to polymerize in the unwanted ring-closed form, and hydrolytic instability in aqueous media. , Degradation in the presence of water has long been recognized as a key practical issue in working with MDO, , and past polymerizations have therefore been performed in anhydrous organic solvents. MDO-containing polymers can then be dispersed or dissolved in water, owing to the stability of the ring-opened unit under various conditions. ,,,,, Other work has sought to side-step MDO stability issues by designing related classes of heteroatom-containing monomers that can undergo productive radical ring-opening reactions in aqueous media with conventional monomers, including both CKA derivatives with increased hydrophobicity and thionolactones for polymerization-induced self-assembly (PISA) by controlled polymerization methods. − …”

RAFT‐Mediated Emulsion Polymerization‐Induced Self‐Assembly for the Synthesis of Core‐Degradable Waterborne Particles

“…In the case of the (co)polymerization of S, full conversion was achieved within about 2 h after an inhibition period of about 1 h, whether DOT was present or not (Figure 4). Like in the copolymerization of DOT with S under conventional emulsion conditions, DOT did not induce any retardation on the polymerization of S under rROPISA conditions [17] …”

“…We eventually assessed the degradability of the P(BA‐ co ‐DOT) and P(S‐ co ‐DOT) blocks. The dry extracts obtained from experiments PNAM‐BA, PNAM‐BA‐DOT, PNAM‐S and PNAM‐S‐DOT were treated with 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD), an organo‐soluble base [14, 17] . The treatment of PNAM‐BA‐DOT and PNAM‐S‐DOT induced a shift of the MMD toward the lower molar masses confirming the degradation of the copolymers (Figure 9).…”

“…In parallel to this work, [17] we investigate emulsion polymerization‐induced self‐assembly (PISA) mediated by reversible addition‐fragmentation chain transfer (RAFT) [18–20] for the synthesis of core‐degradable polymer particles. PISA involves the simultaneous synthesis and self‐assembly of amphiphilic block copolymers using a controlled polymerization process.…”