Synthesis of Sterically-Stabilized Polystyrene Latexes Using Well-Defined Thermoresponsive Poly(N-isopropylacrylamide) Macromonomers

Exploiting Wavelength Orthogonality in Photoinitiated RAFT Dispersion Polymerization and Photografting for Monodisperse Surface-Functional Polymeric Microspheres

We report a strategy toward surface-functional polymeric microspheres using a wavelength orthogonality technique that employs photoinitiated reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization and the subsequent photografting under different wavelengths of light. Initial screening of reaction conditions indicated photoreactive polymeric microsphere with uniform sizes could be prepared by using photoinitiator-functionalized macro-RAFT agents under purple light irradiation. Photoreactive polymeric microspheres allowed photografting polymerizations under UV light irradiation, and we further demonstrated the broad scope of this method by photografting acrylamide, acrylic, and methacrylic monomers. Finally, carboxyl-functionalized polymeric microspheres with an exceptional high number of carboxyl groups were successfully prepared by this technique, which permitted extensive surface bioconjugation of model proteins (e.g., streptavidin). This method should expand the capabilities of RAFT dispersion polymerization to afford diverse surface-functional polymeric microspheres for some specific applications.

Evaluation of Self-Assembly Pathways to Control Crystallization-Driven Self-Assembly of a Semicrystalline P(VDF-co-HFP)-b-PEG-b-P(VDF-co-HFP) Triblock Copolymer

To date, amphiphilic block copolymers (BCPs) containing poly(vinylidene fluoride-co-hexafluoropropene) (P(VDF-co-HFP)) copolymers are rare. At moderate content of HFP, this fluorocopolymer remains semicrystalline and is able to crystallize. Amphiphilic BCPs, containing a P(VDF-co-HFP) segment could, thus be appealing for the preparation of self-assembled block copolymer morphologies through crystallization-driven self-assembly (CDSA) in selective solvents. Here the synthesis, characterization by 1H and 19F NMR spectroscopies, GPC, TGA, DSC, and XRD; and the self-assembly behavior of a P(VDF-co-HFP)-b-PEG-b-P(VDF-co-HFP) triblock copolymer were studied. The well-defined ABA amphiphilic fluorinated triblock copolymer was self-assembled into nano-objects by varying a series of key parameters such as the solvent and the non -solvent, the self-assembly protocols, and the temperature. A large range of morphologies such as spherical, square, rectangular, fiber-like, and platelet structures with sizes ranging from a few nanometers to micrometers was obtained depending on the self-assembly protocols and solvents systems used. The temperature-induced crystallization-driven self-assembly (TI-CDSA) protocol allowed some control over the shape and size of some of the morphologies.

Tuning CO2-induced reversible redispersion or irreversible destabilisation for latex separation

HYPOTHESIS

The CO₂-sensitive dispersion/precipitation transition of polymer latexes fabricated based on a responsive emulsifier is a promising way to conveniently acquire bulk polymer materials. Nevertheless, the tedious synthesis procedures for switchable surfactants and the harsh operating requirements for the sensitive latexes constrain the applicability of the approach for latex preparation. Therefore, a new strategy for generating latexes with tunable CO₂ responsiveness in a maneuverable way is urgently needed.

EXPERIMENTS

In this work, a CO₂-switchable electrostatic interaction is introduced to construct responsive latexes. A series of lightly crosslinked poly(diethylaminoethyl methacrylate-styrene) [P(DEA-St)] latexes with different PDEA contents were fabricated via one-pot emulsion copolymerization, with divinylbenzene and sodium dodecylsulfate (SDS) used as the crosslinker and anionic emulsifier, respectively. The influence of the DEA feeding ratio on the resulting P(DEA-St) colloids was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Then, a cyclic CO₂/N₂ input was introduced to verify the response transitions of polymer latexes.

FINDINGS

Accompanied by the stepwise decrease of DEA feeding ratio, the morphology of the resulting copolymerized nanoparticles changed from an ambiguous bulge to the typical spherical pattern. In addition, the P(DEA-St) latexes treated by cyclic CO₂/N₂ exhibit four different types of response modes, namely (i) CO₂-switchable swelling/deswelling transition, (ii) CO₂-reversible dispersion/coagulation transition, (iii) CO₂-induced irreversible destabilisation and (iv) CO₂-insensitive latexes. The CO₂-responsive destabilisation is highly applicable in the separation and transportation fields of commercial latex products, such as poly(methyl methacrylate), poly(n-butyl acrylate) and poly(butyl methacrylate) colloids.

“One-pot” aminolysis/thia-Michael addition preparation of well-defined amphiphilic PVDF-b-PEG-b-PVDF triblock copolymers: self-assembly behaviour in mixed solvents

Novel amphiphilic PVDF-based triblock copolymer (PVDF₅₀-b-PEG₁₃₆-b-PVDF₅₀) is synthesized using RAFT polymerization and a one-pot thia-Michael addition. Self-assembly of this ABA copolymer resulted in formation of original crystalline structures.

Protecting Group-Free Synthesis of Glycopolymer-Type Amphiphilic Macromonomers and Their Use for the Preparation of Carbohydrate-Decorated Polymer Particles

Polymer particles modified with carbohydrates on their surfaces are of significant interest, because their specific recognition abilities to biomolecules are valuable for developing promising materials in biomedical fields. Carbohydrate-decorated core-shell polymer particles are expected to be efficiently prepared by dispersion polymerization using a glycopolymer-based amphiphilic macromonomer as both a polymeric steric stabilizer and a monomer. To create glycopolymer-type macromonomers, we propose a new strategy combining living cationic polymerization of an alkynyl-functionalized vinyl ether (VE), and the click reaction for the preparation of glycopolymers having a polymerizable terminal group, and investigate their dispersion copolymerization with styrene for generating carbohydrate-decorated polymer particles. This study deals with (i) the synthesis of block copolymer-type amphiphilic macromonomers bearing a methacryloyl group at the α-terminus, and pendant alkynyl groups by living cationic polymerization of alkynyl-substituted VE (VEEP), (ii) the derivatization of maltose-carrying macromonomers by click chemistry of the pendant alkynyl groups of the precursor macromonomers with maltosyl azide without any protecting/deprotecting processes, and (iii) the preparation of maltose-decorated (Mal-decorated) polymer particles through the dispersion copolymerization of glycopolymer-type macromonomers with styrene in polar media. Moreover, this study concerns the specific interactions of the resultant polymer particles with the lectin concanavalin A (Con A).

Photocrosslinked PVDF-based star polymer coatings: an all-in-one alternative to PVDF/PMMA blends for outdoor applications

A 4-arm PVDF photocrosslinked coating displays outstanding adhesion properties to a metal surface, and tunable surface energy and water contact angle.

One-pot synthesis of poly(vinylidene fluoride) methacrylate macromonomers via thia-Michael addition

A comparison of two one-pot methods to prepare methacrylate PVDF-macromonomers and the synthesis of PVDF-containing block copolymers.

Synthesis of poly(N-acryloylmorpholine) macromonomers using RAFT and their copolymerization with methacrylic acid for the design of graft copolymer additives for concrete

Methacrylate end-capped poly(N-acryloylmorpholine) macromonomers (PNAM-MA) of number-average molar mass of about 2400 g mol⁻¹ have been synthesized by post-modification of PNAM chains obtained by RAFT.

Facile production of nanoaggregates with tuneable morphologies from thermoresponsive P(DEGMA-co-HPMA)

RAFT-mediated emulsion polymerization of styrene and subsequent morphological transition produces nanoaggregates with tuneable morphologies.

Synthesis and characterization of poly(amino acid methacrylate)-stabilized diblock copolymer nano-objects

Two amino acid methacrylates prepared via Michael addition are used as building blocks to prepare novel diblock copolymer nano-objects via polymerisation-induced self-assembly.

Fast and facile one-step synthesis of monodisperse thermo-responsive core–shell microspheres and applications

Highly monodisperse PMMA microspheres covered with a thermo-responsive shell were synthesized in a single step by means of photoinitiated RAFT dispersion polymerization at room temperature.

Synthetic protocols toward polypeptide conjugates via chain end functionalization after RAFT polymerization

We design protocols of conjugating synthetic polypeptides to RAFT-prepared polymers regardless of RAFT CTA structures.

Janus magnetic nanoparticles with a bicompartmental polymer brush prepared using electrostatic adsorption to facilitate toposelective surface-initiated ATRP

Utilizing the inherent negative charge of mica surfaces, amine-functionalized magnetic nanoparticles (Fe3O4/NH2) were electrostatically adsorbed onto the mica such that surface-initiated ATRP could be used to grow poly(n-isopropylacrylamide) (PNIPAM) from the exposed hemisphere. By reducing the solution pH, a positive charge generated on the mica was used to release the nanoparticles from the substrate. A second ATRP reaction was carried out to grow poly(methacrylic acid) (PMAA) from the initiated surfaces. As a result, the Fe3O4/NH2 core has a polymer shell with one hemisphere PMAA and the other hemisphere PNIPAM-b-PMAA resulting in the PMAA-Fe3O4-PNIPAM-b-PMAA bicompartmental polymer Janus nanoparticles. Elemental and functional group compositions were confirmed using ATR-FTIR, XPS, and EDS. Imaging with AFM, SEM, and TEM showed the evolution of the Janus nanoparticle morphology. This study demonstrates a facile and innovative scheme involving a noncovalent solid protection technique combined with sequential, surface-confined controlled radical polymerizations for the production of multicomponent nanocomposites.

RAFT polymerization of hydroxy-functional methacrylic monomers under heterogeneous conditions: effect of varying the core-forming block

Do isomeric core-forming blocks afford the same thermo-responsive behavior for diblock copolymer worm gels?

Thermoresponsive nanospheres with a regulated diameter and well-defined corona layer

In the present work, we prepared core-corona-type nanospheres bearing a thermoresponsive polymer with a controlled chain length on their surface. The corona layers were composed of poly(N-isopropylacrylamide) (PNIPAAm) chains (Mn = 3000-18,000) with a narrow polydispersity index prepared by atom-transfer radical polymerization (ATRP). Nanospheres were prepared by dispersion copolymerization of styrene with the PNIPAAm macromonomer in a polar solvent. The obtained nanospheres were monodisperse in diameter. The diameter of the nanospheres was regulated either by the number or chain length of the PNIPAAm macromonomers. In fact, the nanosphere diameter was regulated from ca. 100 to 1000 nm. When two types of PNIPAAm macromonomers are used, the obtained nanospheres have two different kinds of PNIPAAm on their surface. The surface of the nanospheres was observed to be thermoresponsive nanosphere in 0, 50, 100 mmol L(-1) NaCl aqueous solution. The nanosphere diameter and the surface-grafted polymer were concurrently adjusted for use in biomedical applications.

Preparation of well-defined poly(2-hydroxyethyl methacrylate) macromonomers via atom transfer radical polymerization

A series of six near-monodisperse methacrylic macromonomers is prepared via atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate using a tertiary amine-functionalized initiator at 50 °C, followed by quaternization with excess 4-vinylbenzyl chloride at 20 °C. GPC analyses indicate polydispersities of around 1.20 and their mean degrees of polymerization (DP) range from 20 to 70, as judged by both (1) H NMR and UV spectroscopy. The former technique is more convenient but the latter proved more accurate for the higher DP values, provided that an appropriate model compound is utilized for calibration. Finally, these new macromonomers are used to prepare sterically stabilized polystyrene latexes with relatively narrow size distributions via alcoholic dispersion polymerization.

Polymerization-induced self-assembly of galactose-functionalized biocompatible diblock copolymers for intracellular delivery

Recent advances in polymer science are enabling substantial progress in nanobiotechnology, particularly in the design of new tools for enhanced understanding of cell biology and for smart drug delivery formulations. Herein, a range of novel galactosylated diblock copolymer nano-objects is prepared directly in concentrated aqueous solution via reversible addition-fragmentation chain transfer polymerization using polymerization-induced self-assembly. The resulting nanospheres, worm-like micelles, or vesicles interact in vitro with galectins as judged by a turbidity assay. In addition, galactosylated vesicles are highly biocompatible and allow intracellular delivery of an encapsulated molecular cargo.