From Facile One-Pot Synthesis of Semi-Degradable Amphiphilic Miktoarm Polymers to Unique Degradation Properties

We report a one-pot synthesis of well-defined A5B and A8B miktoarm star-shaped polymers where N,N-dimethylaminoethyl methacrylate (DMAEMA) and various cyclic esters such as ε-caprolactone (ε-CL), lactide (LA) and glycolide (GA) were used for the synthesis. Miktopolymers were obtained by simultaneously carrying out atom transfer radical polymerization (ATRP) of DMAEMA, ring-opening polymerization (ROP) of cyclic esters, and click reaction between the azide group in gluconamide-based (GLBr5-Az) or lactonamide-based (GLBr8-Az) ATRP initiators and 4-pentyn-1-ol. The relatively low dispersity indices of the obtained miktoarm stars (Đ = 1.2-1.6) indicate that control over the polymerization processes was sustained despite almost complete monomers conversions (83-99%). The presence of salts from phosphate-buffered saline (PBS) in polymer solutions affects the phase transition, increasing cloud point temperatures (TCP) values. The critical aggregation concentration (CAC) values increased with a decreasing number of average molecular weights of the hydrophobic fraction. Hydrolytic degradation studies revealed that the highest reduction of molecular weight was observed for polymers with PCL and PLGCL arm. The influence of the composition on the miktopolymers hydrophilicity was investigated via water contact angle (WCA) measurement. Thermogravimetric analysis (TGA) disclosed that the number of arms and their composition in the miktopolymer affects its weight loss under the influence of temperature.

Synthesis of alkynyl-functionalized linear and star polyethers by aluminium-catalyzed copolymerization of glycidyl 3-butynyl ether with epichlorohydrin and ethylene oxide

A novel family of alkynyl-functional linear and star polyethers were prepared by the copolymerization of glycidyl 3-butynyl ether, ethylene oxide and epichlorohydrin catalyzed by i-Bu₃Al/H₃PO₄/DBU.

Synthesis of amphiphilic ABA triblock oligomer via ATRP and its surface properties

A series of novel amphiphilic ABA-type poly(tridecafluorooctylacrylate)-poly(ethylene glycol)-poly(tridecafluorooctylacrylate) (henceforth referred to as p-TDFA-PEG-p-TDFA) triblock oligomers were successfully synthesized via atom transfer radical polymerization (ATRP) using well-defined Br-PEG-Br as macroinitiator and copper as catalyst. The block oligomers were characterized by Fourier transform infrared (FTIR) spectroscopy and 1H and 19F nuclear magnetic resonances (NMR). Gel permeation chromatography (GPC) showed that the block oligomers have been obtained with narrow molecular weight distributions of 1.22–1.33. X-ray photoelectron spectroscopy (XPS) was carried out to confirm the attachment of p-TDFA-PEG-p-TDFA onto the silicon substrate, together with the chemical compositions of p-TDFA-PEG-p-TDFA. The wetabilities of the oligomer films were measured by water contact angles (CAs). Water CAs of p-TDFA-PEG-p-TDFA film were measured and their morphologies were tested by atomic force microscopy (AFM). The result showed that the CAs of the oligomer films, which possess fluoroalkyl groups assembled on the outer surface, increase after heating due to the migration of fluoroalkyl groups and the resulted microphase separation of the p-TDFA-PEG-p-TDFA.

Well-controlled ATRP of 2-(2-(2-Azidoethyoxy)ethoxy)ethyl Methacrylate for High-density Click Functionalization of Polymers and Metallic Substrates

The combination of atom transfer radical polymerization (ATRP) and click chemistry has created unprecedented opportunities for controlled syntheses of functional polymers. ATRP of azido-bearing methacrylate monomers (e.g. 2-(2-(2-azidoethyoxy)ethoxy)ethyl methacrylate, AzTEGMA), however, proceeded with poor control at commonly adopted temperature of 50 °C, resulting in significant side reactions. By lowering reaction temperature and monomer concentrations, well-defined pAzTEGMA with significantly reduced polydispersity were prepared within a reasonable timeframe. Upon subsequent functionalization of the side chains of pAzTEGMA via Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click chemistry, functional polymers with number-average molecular weights (Mn) up to 22 kDa with narrow polydispersity (PDI < 1.30) were obtained. Applying the optimized polymerization condition, we also grafted pAzTEGMA brushes from Ti6Al4 substrates by surface-initiated ATRP (SI-ATRP), and effectively functionalized the azide-terminated side chains with hydrophobic and hydrophilic alkynes by CuAAC. The well-controlled ATRP of azido-bearing methacrylates and subsequent facile high-density functionalization of the side chains of the polymethacrylates via CuAAC offers a useful tool for engineering functional polymers or surfaces for diverse applications.

One-Pot Synthesis of Block Copolymers by Orthogonal Ring-Opening Polymerization and PET-RAFT Polymerization at Ambient Temperature

Well-defined poly(ε-caprolactone)-b-poly(methyl acrylate) (PCL-b-PMA) block copolymers were synthesized at ambient temperature by one-pot combination of diphenyl phosphate (DPP)-catalyzed ring-opening polymerization (ROP) and photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. Full orthogonality of PET-RAFT polymerization and DPP-catalyzed ROP was confirmed by kinetic studies, which allowed facile synthesis of PCL-b-PMA block copolymers without a specific polymerization sequence. The resulting PCL-b-PMA block copolymers synthesized by either sequential or simultaneous ROP and PET-RAFT polymerization showed remarkably low molecular weight distributions (≤1.15), indicating that both ROP and PET-RAFT polymerizations proceeded in a controlled manner. In contrast to previous synthetic methods to prepare block copolymers, this facile one-pot method allows for rapid synthesis of block copolymers controlled via visible light.

New polymethylene-based AB2 star copolymers synthesized via a combination of polyhomologation of ylides and atom transfer radical polymerization

Polymethylene-based AB₂ star copolymers were synthesized. PM-b-(PS)₂ porous films and particles were fabricated via static breath-figure process and electrospraying, respectively.

Synthesis of polyethylene and polystyrene miktoarm star copolymers using an “in–out” strategy

Miktoarm star copolymers having multiple polyethylene and polystyrene arms joined at the crosslinked polydivinylbenzene core were synthesized using an “in–out” strategy with the combined Pd-catalyzed ethylene “living” polymerization and atom transfer radical polymerization.

Constructing star polymersvia modular ligation strategies

Over recent years, modular ligation reactions—some of which adhere to the click criteria—have enabled the synthesis of a variety of star polymers via efficient polymer–polymer conjugations. The copper catalyzed azide–alkyne cycloaddition (CuAAC), Diels–Alder (DA), and Hetero Diels–Alder (HDA) reactions are reviewed here in detail for the facile generation of various macromolecular star topologies.