We report the preparation of a series of fiber-like micelles of narrow length distribution with an oligo(p-phenylenevinylene) (OPV)-core and a poly(N-isopropylacrylamide) (PNIPAM) corona via two different crystallization-driven self-assembly (CDSA) strategies. The average length Ln of these micelles can be varied up to 870 nm by varying the temperature in self-seeding experiments. In addition, seeded growth was employed not only to prepare uniform micelles of controlled length, but also to form fiber-like A-B-A triblock comicelles with an OPV-core.

The monomer, 2,2,2-trifluoroethyl 3-(N-(2-(diethylamino)ethyl)acrylamido)propanoate (TF-DEAE-AM), which contains both O2 and CO2-responsive functionalities, was first synthesized from commercially available N,N-diethylethylenediamine, 2,2,2-trifluoroethyl acrylate, and acryloyl chloride. Subsequently, a series of dual-gas responsive polymers, poly(2,2,2-trifluoroethyl 3-(N-(2-(diethylamino)ethyl)acrylamido)propanoate) (poly(TF-DEAE-AM)) and poly(ethylene glycol)-b-poly(2,2,2-trifluoroethyl 3-(N-(2-(diethylamino)ethyl)acrylamido)propanoate) (PEG-b-poly(TF-DEAE-AM)), were synthesized by employing reversible addition–fragmentation chain transfer (RAFT) polymerization. Due to the protonation between CO2 and DEAE groups, and the specific van der Waals interactions between O2 and C–F bonds, micelles consisting of poly(TF-DEAE-AM) or PEG-b-poly(TF-DEAE-AM) display distinct CO2 and O2 responsiveness in aqueous media. Pyrene, which is a model hydrophobic drug, is able to be effectively encapsulated in the micelles based on PEG-b-poly(TF-DEAE-AM). It is found that the release of pyrene sharply increases after bubbling CO2 or O2 compared to N2, and the release rate of the solution bubbling with CO2 is the fastest. Since both CO2 and O2 are key gases for the human body, the CO2- and O2-induced release property of poly(TF-DEAE-AM) may open opportunities for the preparation of functional materials with special CO2 and O2 responsiveness for potential applications in biomedicine.

Well-defined ferrocene-containing homopolymers were synthesized by RAFT homopolymerization of an acrylate monomer bearing a ferrocene (Fc) unit and an N,N-diethylamino ethyl (DEAE) group, i.e. 2-(3-(N-(2-(diethylamino)ethyl)-acrylamido)propanoyloxy)ethyl ferrocenecarboxylate (Fc-DEAE-AM). As an ideal redox-responsive group, hydrophobic Fc can be easily oxidized into hydrophilic Fc+ by certain oxidants, providing tremendous opportunities to produce various Fc-containing redox-responsive materials. On the other hand, the pH/CO2-responsive reversible nature of the DEAE group makes it possible to construct a smart system to adapt to the complex environment in practical application. The stimuli-responsive aggregation behavior of the well-defined poly(Fc-DEAE-AM) homopolymer is examined by the combination of a fluorescent probe, UV/vis transmittance, zeta potential, transmission electron microscopy (TEM), and dynamic light scattering (DLS). In fact, due to the redox and pH/CO2-responsive character provided by the Fc and DEAE groups, the poly(Fc-DEAE-AM) homopolymer exhibits distinct phase transition in aqueous solution. In addition, such a homopolymer could form typical spherical particles in acid aqueous solution, and the redox agent could lead to changes in the size and morphology of the aggregates. Thus, we provide a new and efficient way to prepare triple-stimuli-responsive Fc-containing homopolymers, which might be used as interesting building block for the fabrication of multiple stimuli-responsive functional materials.

Surfaces modified with amphiphilic polymers can dynamically alter their physicochemical properties in response to changes of their environmental conditions; meanwhile, amphiphilic polymer coatings with molecular hydrophilic and hydrophobic patches, which can mitigate biofouling effectively, are being actively explored as advanced coatings for antifouling materials. Herein, a series of well-defined amphiphilic asymmetric polymer brushes containing hetero side chains, hydrophobic polystyrene (PS) and hydrophilic poly(ethylene glycol) (PEG), was employed to prepare uniform thin films by spin-casting. The properties of these films were investigated by water contact angle, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and quartz crystal microbalance (QCM). AFM showed smooth surfaces for all films with the roughness less than 2 nm. The changes in water contact angle and C/O ratio (XPS) evidenced the enrichment of PEG or PS chains at film surface after exposed to selective solvents, indicative of stimuli- responsiveness. The adsorption of proteins on PEG functionalized surface was quantified by QCM and the results verified that amphiphilic polymer brush films bearing PEG chains could lower or eliminate protein-material interactions and resist to protein adsorption. Cell adhesion experiments were performed by using HaCaT cells and it was found that polymer brush films possess good antifouling ability.Keywords: antifouling; polymer brush; spin-casting; stimuli-responsive; thin film;

A series of well-defined amphiphilic asymmetric polymer brushes containing hetero side chains, hydrophobic polystyrene (PS) and hydrophilic poly(ethylene glycol) (PEG), was synthesized by sequential reversible addition–fragmentation chain transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP). The well-defined polyacrylate-based backbones (Mw/Mn ≤ 1.22), PtBBPMA-co-PPEGMEMA, were first prepared by RAFT copolymerization of tert-butyl 2-((2-bromopropanoyloxy)methyl)acrylate (tBBPMA), which bears a Br-containing ATRP initiating group and a poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) macromonomer. The reactivity ratios determined by Fineman–Ross and Kelen–Tudos methods showed that both monomers tended to form random copolymers. The density of the Br-containing ATRP initiating group could be well tuned by the feeding ratio of comonomers. ATRP of styrene was directly initiated by PtBBPMA-co-PPEGMEMA without polymeric functionality transformation to afford well-defined (PtBA-g-PS)-co-PPEGMEMA polymer brushes (Mw/Mn ≤ 1.26) via the grafting-from strategy. The pendant tert-butoxycarbonyls in the backbone were selectively hydrolyzed to carboxyls for providing (PAA-g-PS)-co-PPEGMEMA polymer brushes. Both polymer brushes with the exact same side chains, but different backbones, self-assembled into large compound micelles and bowl-shaped micelles in aqueous media, respectively. This is a direct and strong example to address the importance of the properties of the backbone of a graft copolymer on its self-assembly behavior. Interestingly, different from common spherical micelles, which can just solubilize hydrophobic compounds within their core, the large compound micelles formed by (PtBA-g-PS)-co-PPEGMEMA polymer brushes can encapsulate hydrophilic Rhodamine 6G and hydrophobic pyrene separately or simultaneously.

A facile strategy of Ir-catalyzed visible light mediated atom transfer radical polymerization (ATRP) was reported toward direct modification of commercial poly(vinyl chloride) (PVC) by graft polymerization of methacrylate monomers, such as methyl methacrylate (MMA), pentafluorophenyl methacrylate (PFMA), and oligo(ethylene glycol) methyl ether methacrylate (OEGMA). This approach also allows (co)polymerization of acidic monomers of methacrylic acid (MAA), which is usually incompatible with conventional ATRP. In this approach, the structural defects of allyl chloride and tertiary chloride groups of PVC, along with some of the secondary chlorides of vinyl chloride repeated units, were activated to serve as initiating sites for photo-mediated ATRP by using Ir(ppy)3 as a photo-redox catalyst under low intensity blue LED light strips (10 W, 460–470 nm) in DMF, probably preserving secondary C–Cl bonds of VC repeated units. The polymerization can be effectively tuned between “activation” and “deactivation” states by alternating light “ON” and “OFF” with the maintenance of a linear increase in molecular weight with conversion and first order kinetics. Most importantly, this kind of polymerization shows great tolerance with oxygen, which can proceed in a closed vessel with a controlled/living manner without a deoxygenation procedure. Additionally, this strategy can be employed for the surface functionalization of commercial PVC sheets by surface-initiated ATRP of methacrylate monomers, i.e. PFMA and OEGMA, without prerequisite of functionality transformation and deoxygenation procedures. The surface water contact angles of the PVC sheet changed from 74° to 11° and above 92° after surface functionalization with POEGMA and PPFMA, respectively. Due to the spatially controlled ability of this strategy, the selective regulation in location and density of the surface functionalization of PVC, that is, surface patterning can be realized by modulating the dosage of light.

Photodynamic therapy (PDT) is a noninvasive therapeutic modality with fast healing process and little or no scarring. The production of reactive oxygen species is highly dependent on oxygen concentration, and thus, the therapeutic efficacy of PDT would be retarded by inefficient oxygen supply in hypoxic tumor cell and the oxygen self-consuming mechanism of PDT. It is well-known that perfluorocarbons are endowed with properties of enhanced oxygen solubility and transfer capacity. Herein, we prepared a series of nanoplatforms of spherical micelles with different ratios of pentafluorophenyl to porphyrin in the core and utilized these micelles as models to examine the influence of content of fluorinated segments on the PDT effect of porphyrins. It was found for the first time, as far as we are aware, that the production efficacy of singlet oxygen increased with the rising in the ratio of pentafluorophenyl to porphyrin. Thus, this work presents a new avenue to improve PDT efficacy by enhancing oxygen solubility and diffusivity of nanoplatforms with the incorporation of perfluorocarbon segments.

Graphite fluoride (GiF) and graphene fluoride (GeF) showed interesting electrochemical, electronic, and mechanical properties in comparison with their derivatives of graphite and graphene, respectively. Due to the chemical inertness of GiF and GeF, as far as we are aware, no report can be found on the modification of GiF and GeF with polymeric chains. Herein, we reported that photoredox-mediated atom transfer radical polymerization (ATRP) is able to directly introduce methacrylate-based polymers, including poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA), poly(methyl methacrylate) (PMMA), poly(pentafluorophenyl methacrylate) (PPFMA), and poly(methacrylic acid) (PMAA), onto the surface of GiF and GeF by utilizing C–F bonds of GiF and GeF as initiating sites and Ir(ppy)3 as a photoredox catalyst under low intensity blue LED light strips (10 W, 460–470 nm) in DMF for graft polymerization without a tedious deoxygenation procedure. Owing to the attractive properties of GiF and GeF, along with the capacity of spatial control over the formation of polymeric chains on the surface of GiF and GeF endowed by the inherent nature of photoredox-mediated ATRP, there is no doubt that the strategy developed in the current work shows a great potential in the preparation of polymer-decorated GiF and GeF and the corresponding functional materials.

A series of fluorine-containing amphiphilic graft copolymers consisting of a semi-fluorinated poly(2-methyl-1,4-bistrifluorovinyloxybenzene) (PMBTFVB) backbone and hydrophilic poly(acrylic acid) (PAA) side chains was synthesized by the combination of thermal cycloaddition polymerization and atom transfer radical polymerization (ATRP) through the grafting-from strategy. 2-Methyl-1,4-bistrifluorovinyloxybenzene was first homopolymerized via thermal step-growth [2π + 2π] cycloaddition polymerization to form a perfluorocyclobutyl aryl ether-based backbone. This fluoropolymer was transformed into the macroinitiator with the controllable density of the initiating functionality by the mono-bromination of pendant methyls. The target PMBTFVB-g-PAA amphiphilic graft copolymers were achieved by ATRP of tert-butyl acrylate initiated by the macroinitiator followed by the acidolysis of hydrophobic PtBA side chains into hydrophilic PAA segments. Critical micelle concentrations (cmc) of these amphiphilic graft copolymers were determined by fluorescence spectroscopy using N-phenyl-1-naphthylamine as fluorescent probe. Self-assembly behaviors of these fluorine-containing amphiphilic graft copolymers in aqueous media were investigated by transmission electron microscopy (TEM). Diverse micellar morphologies including vesicular, worm-like, and bowl-shaped nanostructures were obtained through tuning the water content and the length of PAA side chain.

Amphiphilic graft copolymers bearing a hydrophobic poly(2-methyl-1,4-bistrifluorovinyloxybenzene) (PMBTFVB) backbone and hydrophilic poly(ethylene glycol) (PEG) side chains were synthesized through the Williamson reaction between the hydroxyl end group of PEG and the pendant benzyl bromide functionality of the backbone introduced through the mono-bromination of the pendant methyls on the backbone by using N-bromosuccinimide and benzoyl peroxide, via the grafting-onto strategy. Critical micelle concentrations (cmc) of these amphiphilic graft copolymers were determined by fluorescence spectroscopy using N-phenyl-1-naphthylamine as a fluorescence probe. The studies on the morphologies of self-assembled aggregates of the resulting PMBTFVB-g-PEG graft copolymers with relatively narrow molecular weight distributions (Mw/Mn = 1.26–1.39) in aqueous solution showed that the observed morphologies were obviously affected by a number of factors including the method used for preparing micelles, the concentration of the copolymer in the cosolvent, and the water content.

•A new class of acrylamide monomer was prepared through Aza-Michael reaction.•Homopolymers with OEG and DEAE groups were prepared via RAFT.•LCSTs of homopolymer could be tuned by changing pH value.•CO2 gas can reversibly adjust the solubility of homopolymer.A homopolymer strategy was developed to synthesize temperature and pH/CO2 stimulus-responsive homopolymers. A new class of acrylamide monomers bearing oligo(ethylene glycol) unit and N,N-diethylaminoethyl group were designed and prepared through Aza-Michael addition reaction followed by amidation with acryloyl chloride using amino group as a linkage to connect oligo(ethylene glycol), N,N-diethylaminoethyl, and polymerizable double bond groups together. Subsequently, the corresponding homopolymers containing oligo(ethylene glycol) unit and N,N-diethylaminoethyl group in each repeated unit were prepared via RAFT polymerization with controlled molecular weights and relatively narrow molecular weight distributions. The lower critical solution temperature (LCST) of homopolymer was examined to be influenced by molecular weight, salt concentration, and pH value of aqueous solution. The LCSTs of homopolymers could be tuned in a wide temperature window by changing pH value of aqueous solution and it increased with the decrease of pH value. Particularly, CO2 gas as a unique pH stimulus can also reversibly adjust the solubility of homopolymer without the addition of acids or bases.

Gold nanoparticles (AuNPs) covered with a series of well-defined poly(ethylene glycol)-b-polystyrene (PEG-b-PS) amphiphilic diblock copolymers containing a thiol group at the end of PS block were prepared to explore the influence of chain length of PS segment on the colloidal stability and catalytic activity of AuNPs. PEG-b-PS amphiphilic diblock copolymers with different PS chain lengths and narrow molecular distributions (Mw/Mn ≤ 1.15) were synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization employing a PEG-based macromolecular chain transfer agent (Mn ≈ 2000 g/mol), followed by transforming the thiocarbonate end functionality into a thiol group in the presence of 2-aminoethanol and tributylphosphane. PEG-b-PS-stabilized gold nanoparticles (Au@PEG-b-PS) were prepared by ligand exchange reaction between citrate-stabilized AuNPs and the thiol end group of PEG-b-PS diblock copolymer. The presence of the hydrophobic PS layer not only improved the stability of Au@PEG-b-PS against electrolyte-induced aggregation but also greatly promoted the resistance of Au@PEG-b-PS against competitive displacement of dithiothreitol. Au@PEG-b-PS showed excellent catalytic activity in the reduction reaction of 4-nitrophenol into 4-aminophenol, and the catalytic activity increased with the decrease in the chain length of PS block. In addition, the high stability imparted by the PS layer endowed Au@PEG-b-PS with good reusability in catalysis without the loss of catalytic activity.

A new acrylamide monomer bearing isopropylamide and N,N-diethylamino ethyl groups in the side chain, i.e., N-(2-(diethylamino)ethyl)-N-(3-(isopropylamino)-3-oxopropyl)acrylamide (DEAE-NIPAM-AM), was synthesized through Aza-Michael addition reaction followed by amidation with acryloyl chloride. The homopolymers, poly(N-(2-(diethylamino)ethyl)-N-(3-(isopropylamino)-3-oxopropyl)acrylamide)s [poly(DEAE-NIPAM-AM)], with controlled molecular weights and relatively narrow molecular weight distributions were then prepared via RAFT polymerization. The lower critical solution temperature (LCST) of the homopolymer was examined to be influenced by molecular weight, salt concentration, and pH value of aqueous solution. The LCST of the homopolymer could be tuned in a wide temperature window by changing the pH value of aqueous solution, and it increased with the decrease of pH value. Particularly, CO2 gas as a unique pH stimulus can also reversibly adjust the solubility of homopolymer without the addition of acids or bases.

A series of amphiphilic ABA triblock copolymers containing polyisobutylene (PIB) and poly(p-(2-(4-biphenyl)perfluorocyclobutoxy)phenyl methacrylate) (PBPFCBPMA) segments was synthesized via sequential living carbocationic polymerization and atom transfer radical polymerization (ATRP). Living carbocationic polymerization of isobutylene was initially performed at −78 °C in n-hexane–CH3Cl followed by end-capping with 1,3-butadiene to provide a well-defined diallyl-Cl-terminated PIB with a narrow molecular weight distribution (Mw/Mn = 1.26). The PIB functionalized at both ends was further transformed into Br-PIB-Br, an ATRP macroinitiator bearing one ATRP initiating group at each end. The target triblock copolymers of PBPFCBPMA-b-PIB-b-PBPFCBPMA with a relatively narrow molecular weight distribution (Mw/Mn ≤ 1.42) were obtained via ATRP of BPFCBPMA at 70 °C in tetrahydrofuran initiated by Br-PIB-Br. The self-assembly behavior of these triblock copolymers in n-hexane, acetone, and 1,1,1-trifluoroacetone was investigated by transmission electron microscopy. It was found that large spherical compound micelles with PIB blocks as coronas were formed in n-hexane, whereas large compound micelles with fluorine-containing PBPFCBPMA blocks as coronas were formed in acetone and 1,1,1-trifluoroacetone.

A novel amphiphilic sun-shaped copolymer, c-PMBTFVB-g-PMAA (MBTFVB: 2-methyl-1,4-bistrifluorovinyloxybenzene, MAA: methacrylic acid) containing a cyclic perfluorocyclobutyl (PFCB) aryl ether-based backbone and PMAA lateral side chains with narrow molecular weight distribution (Mw/Mn ≤ 1.38), was synthesized via the site transformation strategy. First, a PMBTFVB linear precursor was prepared by thermal step-growth cycloaddition polymerization of MBTFVB trifluorovinyl monomer. After the end functionalization of the linear precursor with alkyne, Glaser coupling reaction was performed to produce c-PMBTFVB cyclic homopolymer. The pendant methyls on PFCB aryl ether-based backbone were then converted to Br-containing ATRP initiating groups by a mono-bromination reaction with N-bromosuccinimide (NBS) and benzoyl peroxide (BPO) to give c-PMBTFVB-Br cyclic macroinitiator without affecting the main chain, where the density of ATRP initiation groups could be tuned from 33% to 58% by varying the feeding ratio of NBS to the pendant methyl. Subsequently, c-PMBTFVB-g-PMAA sun-shaped amphiphilic copolymers with hydrophilic PMAA side chains were synthesized by ATRP of tert-butyl methacrylate (tBMA) initiated by c-PMBTFVB-Br, followed by the selective hydrolysis of hydrophobic PtBMA segment into hydrophilic PMAA segment using CF3COOH. The obtained c-PMBTFVB cyclic homopolymer and its precursor were well characterized by GPC, NMR, and DSC and all the observations indicated a high efficiency of the intra-macromolecular cyclization via Glaser coupling reaction. The critical micelle concentrations of the obtained amphiphilic copolymers were determined by fluorescence probe technique and the morphologies of the formed micelles were investigated by TEM.