Chundong Huang

An insight into aqueous photoinitiated polymerization-induced self-assembly (photo-PISA) for the preparation of diblock copolymer nano-objects

A poly(glycerol monomethacrylate) (PGMA) chain transfer agent is used for aqueous reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization of 2-hydroxypropyl methacrylate (HPMA) via photoinitiation or thermal initiation. Kinetic studies showed that the rate of polymerization of photo-PISA was much faster than that of thermally initiated PISA, both at the homogeneous polymerization stage and the heterogeneous polymerization stage. The effect of light intensity on photo-PISA was investigated, which showed that increasing light intensity led to faster polymerization behavior. In virtue of the temperature-insensitive property of the photoinitiator, the sole effect of reaction temperature on PISA was studied in detail for the first time. Transmission electron microscopy (TEM) measurements indicated that higher reaction temperature facilitated the formation of higher order morphologies. Finally, a one-pot photoinitiated polymerization was conducted in water to prepare diblock copolymer nano-objects with different morphologies (spheres, worms, and vesicles).

Facile Preparation of CO2‐Responsive Polymer Nano‐Objects via Aqueous Photoinitiated Polymerization‐Induced Self‐Assembly (Photo‐PISA)

Carbon dioxide (CO2 )-responsive polymer nano-objects are prepared by photoinitiated reversible addition-fragmentation chain transfer dispersion polymerization of 2-hydroxypropyl methacrylate and 2-(dimethylamino)ethyl methacrylate (DMAEMA) in water at room temperature using a poly(poly(ethylene glycol) methyl ether methacrylate) macromolecular chain transfer agent. Kinetic studies confirm that full monomer conversions are achieved in all cases within 10 min of visible-light irradiation (405 nm, 0.5 mW cm-2 ). The effect of DMAEMA on the polymerization is studied in detail, and pure higher order morphologies (worms and vesicles) are prepared by this particular formulation. Finally, CO2 -responsive property of the obtained vesicles is investigated by dynamic light scattering, visual appearance, and transmission electron microscope.

Facile preparation of hybrid vesicles loaded with silica nanoparticles via aqueous photoinitiated polymerization-induced self-assembly

We report a room-temperature photoinitiated polymerization-induced self-assembly (photo-PISA) of 2-hydroxypropyl methacrylate (HPMA) in the presence of silica nanoparticles using a poly(ethylene glycol) methyl ether (mPEG) macromolecular chain transfer agent (macro-CTA). Hybrid vesicles loaded with silica nanoparticles were obtained by this one-pot approach. The solids content of the polymer vesicles can be up to 25% w/w. A control experiment was conducted to prove that free silica nanoparticles can be removed via centrifugation-redispersion. Finally, CO2-responsive hybrid vesicles were prepared by photo-PISA of HPMA and 2-(dimethylamino)ethyl methacrylate (DMAEMA). Silica nanoparticles were subsequently released from the vesicles via CO2 bubbling at room temperature.

Rapid synthesis of well-defined all-acrylic diblock copolymer nano-objects via alcoholic photoinitiated polymerization-induced self-assembly (photo-PISA)

A series of well-defined all-acrylic poly(hydroxyethyl acrylate)-poly(isobornyl acrylate) (PHEA-PIBOA) diblock copolymer nano-objects were prepared by photoinitiated polymerization-induced self-assembly (photo-PISA) of isobornyl acrylate in ethanol/water at 40 °C using poly(hydroxyethyl acrylate)-based macromolecular chain transfer agents (macro-CTAs). Polymerizations proceeded rapidly upon exposure to visible light irradiation (λmax = 405 nm, 0.46 mW cm−2) with high monomer conversion being achieved within 30 min. Gel permeation chromatography (GPC) demonstrated that good control was maintained throughout the photo-PISA process, and the final block copolymers exhibited relatively low polydispersities (Mw/Mn ≤ 1.55). By virtue of the high Tg value of PIBOA, a diverse set of block copolymer nano-objects having different morphologies (e.g. spheres, worms, and vesicles) were prepared and characterized by conventional transmission electron microscopy (TEM). Two phase diagrams were constructed by varying the DP of the PIBOA block or monomer concentration or the DP of the PHEA macro-CTA. Worm-like micelles were prepared by monitoring the viscosity of the reaction mixture in a proof-of-concept experiment. Finally, poly(acrylic acid) (PAA) and poly(2-(dimethylamino)ethyl acrylate) (PDMAEA) macro-CTAs were also utilized to mediate the photo-PISA process, demonstrating the versatility of this method.

Adding a solvophilic comonomer to the polymerization-induced self-assembly of block copolymer and homopolymer: a cooperative strategy for preparing large compound vesicles

We report a reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization of styrene (St) and 4-vinylpyridine (4VP) in methanol/water at 70 °C. The polymerization was mediated by a binary mixture of S-1-dodecyl-S′-(α,α′-dimethyl-α′′-acetic acid) trithiocarbonate (DDMAT) and monomethoxy poly(ethylene glycol)-based macromolecular RAFT agent (mPEG45-DDMAT). By varying the molar ratio of [St]0/[4VP]0, polymer nano-objects of different morphologies (porous vesicles, large compound vesicles (LCVs), and lamellae) were formed. Transmission electron microscopy (TEM) observations demonstrated that LCVs were formed by further aggregation and reorganization of vesicles during the process. Effects of [mPEG45-DDMAT]/[DDMAT] molar ratio, methanol/water ratio, and degree of polymerization (DP) of the core-forming block on the assemblies were also studied in detail. Ag@mPEG45-P(St108-co-4VP24)/P(St108-co-4VP24) LCVs were prepared by in situ reduction of AgNO3, as confirmed by TEM and UV-vis measurements. The obtained Ag@mPEG45-P(St108-co-4VP24)/P(St108-co-4VP24) LCVs exhibited catalytic activity for the catalysis of methylene blue (MB) using NaBH4.