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Organocatalysts are increasingly gaining attention for the ring opening polymerization (ROP) of lactones due to numerous advantages. In this work, the goal is to expand the scope of catalysts for the ROP of alkyl substituted caprolactones: a mixture of beta,delta-trimethyl-epsilon-caprolactones (TMCL). Several organocatalysts were evaluated, with a focus on bifunctional organophosphorus catalysts including two novel categories, namely phosphonic acids and phosphinic acids. The effects of initial monomer concentration, temperature, catalyst loading and catalyst type on the monomer conversion at equilibrium and the reaction kinetics were addressed. The ceiling temperature of TMCL is 302 degrees C in bulk and 34 degrees C at 1 M, as determined experimentally. During polymerization, higher conversion and reaction rates were observed for the most substituted lactone ( proximal lactone). This difference of reactivity between the two regio-isomeric lactones was greater for lower reaction temperatures. Density functional theory (DFT) calculations on the ring opening of the lactones demonstrated that the difference of reactivity can be attributed to a lower enthalpic contribution of the proximal lactone making the ring opening of this lactone more energetically favored. The difference in calculated Gibbs free energy was found to increase with lower temperature.

Reactive oxygen species (ROS) play crucial roles in biological metabolism and intercellular signaling. However, ROS level is dramatically elevated due to abnormal metabolism during multiple pathologies, including neurodegenerative diseases, diabetes, cancer, and premature aging. By taking advantage of the discrepancy of ROS levels between normal and diseased tissues, a variety of ROS-sensitive moieties or linkers have been developed to design ROS-responsive systems for the site-specific delivery of drugs and genes. In this review, we summarized the ROS-responsive chemical structures, mechanisms, and delivery systems, focusing on their current advances for precise drug/ gene delivery. In particular, ROS-responsive nanocarriers, prodrugs, and supramolecular hydrogels are summarized in terms of their application for drug/gene delivery, and common strategies to elevate or diminish cellular ROS concentrations, as well as the recent development of ROS-related imaging probes were also discussed.

A critical challenge in scaffold design for tissue engineering is recapitulating the complex biochemical patterns that regulate cell behavior in vivo. In this work, we report the adaptation of a standard sterilization methodology-UV irradiation-for patterning the surfaces of two complementary polymeric electrospun scaffolds with oxygen cues able to efficiently immobilize biomolecules. Independently of the different polymer chain length of poly(ethylene oxide terephthalate)/poly(butylene terephthalate) (PEOT/PBT) copolymers and PEOT/PBT ratio, it was possible to easily functionalize specific regions of the scaffolds by inducing an optimized and spatially controlled adsorption of proteins capable of boosting the adhesion and spreading of cells along the activated fibrous runways. By allowing an efficient design of cell attachment patterns without inducing any noticeable change on cell morphology nor on the integrity of the electrospun fibers, this procedure offers an affordable and resourceful approach to generate complex biochemical patterns that can decisively complement the functionality of the next generation of tissue engineering scaffolds.

Poly [(vinylbenzyl) trimethylammonium chloride] (PVBTMAC) has been used as a stabilizer in the polymerization-induced self-assembly polymerizations of diacetone acrylamide (DAAM). A whole spectrum of particle morphologies was obtained simply by adjusting the ionic strength of the reaction mixtures; no dilution of the cationic charges with noncharged comonomers or with noncharged polymers was needed. In addition to the ionic strength, the effects of solid content and the length of the PDAAM block on the morphologies of the particles were studied in detail. The experiments are a continuation to previous studies on solution properties of PVBTMAC. It has been shown earlier that the solubility of the polycation may be tuned with counterions. Hydrophobic triflate ions induce an upper critical solution temperature behavior. In the present case, the chains bound to hydrophobic cores of the particles show either a one-step phase separation in aqueous triflate solutions or under certain conditions, a two-step transition. The step-wise transition is typical for responsive polymers with limited mobility.

Control over dynamic functions in larger assemblies is key to many molecular systems, ranging from responsive materials to molecular machines. Here we report a molecular motor that forms bowl-shaped particles in water and how confinement of the molecular motor affects rotary motion. Studying the aggregation process in a broader context, we provide evidence that, in the case of bowl-shaped particles, the structures are not the product of self-assembly, but a direct result of the mixing a good solvent and a (partial) non-solvent and highly independent of the molecular design. Under the influence of the non-solvent, droplets are formed, of which the exterior is hardened due to the increase in the glass transition temperature by the external medium, while the interior of the droplets remains plasticized by the solvent, resulting in the formation of stable bowl-shaped particles with a fluid interior, a glass-like exterior, and a very specific shape: dense spheres with a hole in their side. Applying this to a bulky first-generation molecular motor allowed us to change its isomerization behavior. Furthermore, the motor shows in situ photo-switchable aggregation-induced emission. Strong confinement prohibits the thermal helix inversion step while altering the energy barriers that determine the rotary motion, such that it introduces a reverse trans- cis isomerization upon heating. These studies show a remarkable control of forward and backward rotary motion by simply changing solvent ratios and extent of confinement.

Block copolymers that accommodate both hydrophobic and ionic elements are interesting materials for numerous applications, such as stabilizing agents, lubricants and proton-exchange membranes. Frequently these copolymers are based on weak polyelectrolytes, but the pH-dependent charge density restricts their use to a limited pH window. Although strong polyelectrolytes do not suffer this problem, the most commonly employed post-modification approach limits the choice of the hydrophobic component, as harsh reaction conditions are usually involved. Moreover, this method often results in incomplete functionalization of the precursor copolymer. To avoid these difficulties a mild route was developed that is based on a hydrophobic protected poly(3-sulfopropyl methacrylate) intermediate that enables the preparation of well-defined strong anionic polyelectrolytes. The potential of this method was demonstrated by synthesizing hydrophobic/strong anionic diblock copolymers, and their self-assembly in aqueous solution was studied.

Chemical enhanced oil recovery (EOR) is surely a topic of interest, as conventional oil resources become more scarce and the necessity of exploiting heavy and unconventional oils increases. EOR methods based on polymer flooding, surfactant-polymer flooding and alkali-surfactant-polymer flooding are well established, but new challenges always emerge, which give impulse to the search for new solutions. Polymeric surfactants represent a very attractive alternative to these techniques, because they can provide simultaneously increase in water viscosity and decrease in interfacial tension, both beneficial for the efficiency of the process. The analysis of the literature shows that the use of polymeric surfactants as displacing fluid has the potential to improve the performances of EOR in some cases. However, the synthesis are often challenging and costly and the available data about the real performances of such systems in oil recovery are still sparse. This holds back the possibility of a significant use of polymeric surfactants for EOR This review collects the relevant work done in the last decades in developing and testing polymeric surfactants for EOR, with a particular emphasis on the chemical aspects, the patent literature and bio-based systems. (c) 2016 The Authors. Published by Elsevier B.V.

Chemical enhanced oil recovery (EOR) is surely a topic of interest, as conventional oil resources become more scarce and the necessity of exploiting heavy and unconventional oils increases. EOR methods based on polymer flooding, surfactant-polymer flooding and alkali-surfactant-polymer flooding are well established, but new challenges always emerge, which give impulse to the search for new solutions. Polymeric surfactants represent a very attractive alternative to these techniques, because they can provide simultaneously increase in water viscosity and decrease in interfacial tension, both beneficial for the efficiency of the process. The analysis of the literature shows that the use of polymeric surfactants as displacing fluid has the potential to improve the performances of EOR in some cases. However, the synthesis are often challenging and costly and the available data about the real performances of such systems in oil recovery are still sparse. This holds back the possibility of a significant use of polymeric surfactants for EOR This review collects the relevant work done in the last decades in developing and testing polymeric surfactants for EOR, with a particular emphasis on the chemical aspects, the patent literature and bio-based systems. (c) 2016 The Authors. Published by Elsevier B.V.

Well-defined amphiphilic triblock poly(sodium methacrylate)-polystyrene-poly(sodium methacrylate) (PMAA-b-PS-b-PMAA) copolymers characterized by a different length of either the hydrophilic or the hydrophobic block have been synthesized by ATRP. In solution the micelle-like aggregates consist of a collapsed PS core surrounded by stretched charged PMAA chains. The micelles are kinetically ‘frozen’ and as a consequence the triblock copolymers do not show a significant surface activity. The hydrophilic block length has a major influence on the rheology, the shortest PMAA blocks yielding the strongest gels (at the same total weight concentration). The hydrophobic block length has only a minor influence until a certain threshold, below which the hydrophobic interactions are too weak resulting in weak gels. A mathematical model is used to describe the micelle radius and the results were in good agreement with the experimentally found radius in transmission electron microscopy. The influences of the ionic strength, pH and temperature on the rheology has also been investigated, showing the potential of these polymers as smart hydrogels. The change in conformation of the hydrophilic corona from the collapsed state to the stretched state by changing the pH was quantified with zeta-potential measurements. To the best of our knowledge, this is the first systematic investigation of this kind of triblock copolymers in terms of their rheological behavior in water.

Polymeric vesicles known as polymersomes are formed by the self-assemble of amphiphilic block copolymers and have structural organization similar to liposomes. However, polymersomes present higher physicochemical stability and structure versatility due to their polymeric nature. In this review we describe the main aspects related to the structure and applications of these systems for drug delivery.

Polymeric vesicles known as polymersomes are formed by the self-assemble of amphiphilic block copolymers and have structural organization similar to liposomes. However, polymersomes present higher physicochemical stability and structure versatility due to their polymeric nature. In this review we describe the main aspects related to the structure and applications of these systems for drug delivery.

Porous materials are powerful functional devices that can find applications in many fields, from nanotechnology to biomedicine, from catalysis to membrane separation. In general, porous materials can be processed in various forms, but a rising interest is growing around inorganic thin films and coatings, due to the increased number of applications based on their use. Among the different strategies proposed till now for preparing inorganic porous thin layers/coatings, a simple and versatile route consists in the combined use of sol-gel chemistry, templating, and spin-coating deposition. Therefore, in order to provide a helpful toolbox for users, an extended discussion around the physico-chemical principles behind each of these steps is here reported, also highlighting the advantages and disadvantages of each procedure, together with critical points.

Symmetrical poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEG-PPG-PEG) triblock copolymer with 82.5% PEG as the hydrophilic end blocks, and PPG as the hydrophobic middle block, was chosen to study the effect of ionic liquids (ILs) on the critical micellization temperature (CMT) of block copolymers in aqueous solution. In the present work, cholinium-based ILs were chosen to explore the effect of the anions on the copolymer CMT using fluorescence spectroscopy, dynamic light scattering (DLS), viscosity (η), FT-IR spectroscopy, nuclear magnetic resonance (NMR), and direct visualization of the various self-assembled nanostructures by scanning electron microscopy (SEM). The result suggests that ILs have the ability to decrease the CMT of the aqueous copolymer solution which is dependent on the nature of the anions of the ILs. The present study reveals that the hydrophobic part PPG of the copolymer has more influence on this behavior than the PEG hydrophilic part.

Poly(lactic acid)-block-poly(ethylene glycol) copolymers (PLA-b-PEG) featuring varying tacticities (atactic, heterotactic, isotactic) in the PLA block were synthesized and investigated for their micellar stability, degradation, and thermal properties. Utilizing tin(II) bis(2-ethylhexanoate), aluminum salan, and aluminum salen catalysts, the copolymers were synthesized through the ring-opening polymerization of d-, l-, rac-, or a blend of l- and rac-lactide using monomethoxy-poly(ethylene glycol) as a macroinitiator. The critical micelle concentration, which reflects the micellar stability, was probed using a fluorescence spectroscopic method with pyrene as the probe. The copolymers were degraded in a methanolic solution of 1,5,7-triaza-bicyclo[4.4.0]dec-5-ene and the degradation was measured by H-1 NMR spectroscopic and gel permeation chromatographic analyses. Differential scanning calorimetry and thermogravimetric analysis provided information on the thermal properties of the copolymers. Atactic and heterotactic microstructures in the PLA block resulted in lower micellar stability, as well as faster degradation and shorter erosion time compared to polymers with high isotactic enchainment (P-m). By modification of the P-m, micellar stability, degradation, and erosion rates of the copolymers can be tuned to specific biomedical applications. Interestingly, while tin(II) bis(2-ethylhexanoate) and aluminum salan-catalyzed PLA-b-PEG copolymers exhibited similar micellization behavior, the aluminum salen-catalyzed PLA-b-PEG exhibited unique behavior at high micelle concentration in the presence of the pyrene probe. This unique behavior can be attributed to the disintegration of the micelles through the interactions of long isotactic stereoblock segments.

International audience; The reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylic acid (AA) in water was studied in detail at different pHs using 4-cyano-4-thiothiopropylsulfanyl pentanoic add (CTPPA) as a control agent and 4,4'-azobis(4-cyanopentanoic acid) (ACPA) as an initiator. Well-defined hydrophilic macromolecular RAFT agents (PAA-CTPPA) were obtained and further used directly in water for the polymerization of styrene. The corresponding polymerization-induced self-assembly (PISA) process was evaluated at different pHs and it was shown that working in acidic conditions (pH = 2.5) led to well-defined amphiphilic block copolymer particles (D < 1.4) of small size (below 50 nm). When the pH increased, the control over the growth of the polystyrene (PS) block was gradually lost. Chain extension experiments of PAA-CTPPA with N-acryloylmorpholine (NAM), a hydrosoluble and non-pH sensitive monomer, performed at different pHs showed that the very first addition-fragmentation steps that occurred in water were impeded when PAA was ionized leading to partial consumption of PAA-CTPPA and thus to PS molar masses higher than expected. Varying the PAA-CTPPA concentration at pH = 2.5 led in all cases to stable particles composed of well-defined block copolymers with PS segments of different molar masses.

We present the morphological phase map of semicrystalline poly(butadiene)-b-poly(ethylene oxide) (PB-b-PEO) diblock copolymers (BCP) in dilute n-heptane solutions. The solutions of the diblock copolymer have been quenched from 70 degrees C, that is above the melting temperature T-m of the PEO block, following two thermal pathways: (A) by direct immersion into liquid nitrogen and (B) by quenching to the crystallization temperature T-c of the PEO block. Scanning force microscopy (SFM) and transmission electron microscopy (TEM) allowed imaging of the dried crystalline morphologies, whereas in solution the micelles have been visualized by cryogenic transmission electron microscopy (cryo-TEM). The apparent hydrodynamic radii of the micellar structures in solution were determined by dynamic light scattering (DLS). The effects of the block length and block ratio, and the influence of the thermal history on the morphology have been systematically investigated for the series of PB-b-PEO BCP. In pathway A, different morphologies such as spheres, rods, worms and entangled cylinders have been observed; whereas in pathway B, as the weight fraction and the length of the PEO block increased, the morphology changed from spherical to cylindrical or to lamellar, and finally to large dendritic micelles. This tailoring of morphologies is fully reversible with temperature and was found to correlate to the crystalline state of the PEO chains.

This study investigates the effect of alcohols on the solution and adsorption properties of symmetric triblock nonionic copolymers comprising blocks of ethylene oxide (EO) and propylene oxide (PO) (EO(37)PO(56)EO(37)). The cloud point, surface tension, critical micelle concentration (CMC), and maximum packing at the air-water interface are determined, and the latter is compared to the amount of polymer that adsorbs from solution onto polypropylene (PP) and cellulose surfaces. The interaction energy and radius of micelles are calculated by using molecular dynamics (MD) simulations. Equivalent MD bead parameters were used in dynamic density functional theory (DDFT) simulations to study the influence of alcohols on the phase behavior of EO(37)PO(56)EO(37) and its adsorption on PP from aqueous solutions. The simulation results agree qualitatively with the experimental observations. Ethanol acts as a good cosolvent for EO(37)PO(56)EO(37) and reduces the amount of EO(37)PO(56)EO(37) that adsorbs on PP surfaces; however, little or no influence is observed on the adsorption on cellulose. Interestingly, longer chain alcohols, such as 1-pentanol, produce the opposite effect. Overall, the solution and adsorption properties of nonionic symmetric triblock copolymers in the presence of alcohols are rationalized by changes in solvency and the hydrophobic effect.

We report the formation and characterisation of easily functionalisable mixed micelles with DNA/PEO corona and PPO core which can be loaded with hydrophobic molecules and stabilised by the formation of a cross-linked semi-interpenetrating network. Furthermore, the corona is functionalised by hybridisation either with dye-modified complementary DNA, with demonstrable distance control, or with DNA-labelled gold nanoparticles.

International audience; Herein we report the preparation of hierarchically micro- and nanostructured polymer surfaces in block copolymer/homopolymer blends. The structural order at different length scales was obtained combining two methodologies, e.g., the breath figures method to produce porous microstructures ("top-down" approach) with block copolymer self-assembly to induce microphase separation at the nanometer length scale ("bottom-up" approach). The interplay of the breath figure formation during the spin-coating and self-assembly of the triblock copolymer allowed the preparation of polymer surfaces having micrometer-sized cavities decorated with nanostructured block copolymers. The system described herein possesses unique characteristics. First, the surface chemical composition can be varied by a surface rearrangement upon annealing either to dry or humid air. Moreover, surface rearrangement is accompanied with structural changes, i.e. both topography and nanostructuration can be reversibly modified upon annealing. In terms of topograghy, a transition between holes and hills was obtained upon soft annealing to water vapor and can be recovered upon annealing to dry air. Finally, the pore nanostructure can be modulated from a micellar array to a lamellar phase when the film is exposed either to air or to tetrahydrofuran vapor.

We describe the preparation and characterisation of inorganic-organic hybrid block copolymer silver nanoparticles via the preparation of spherical multi-responsive polymeric micelles of poly(N-methyl-2-vinyl pyridinium iodide)-block-poly(ethylene oxide), P2MVP38-b-PEO211 and poly(acrylic acid)-block-poly(isopropyl acrylamide), PAA55-b-PNIPAAm88 in the presence of AgNO3. Hence, the P2MVP and PAA segments were employed to fix Ag+ ions within the micellar core (25 °C) or shell (60 °C), while the PEO segments ensured spontaneous reduction of Ag+ ions into metallic Ag, as well as colloidal stabilisation. Spherical and elongated composite core-shell(-corona) nanoparticles (CNPs) were formed containing several small, spherical silver nanoparticles within the micellar core or shell. As the co-assembly of the oppositely charged copolymers into micelles is electrostatically driven, the CNPs can be destabilised by, for example, addition of simple salts, i.e., the CNPs are stimuli responsive. CNP size and morphology control can be achieved via the preparation protocol. For example, heating to 60 °C, i.e., above the PNIPAAm LCST, results in core-shell-corona CNPs with the Ag-NPs situated in the aggregate shell.

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International audience; The synthesis of well-defined second-generation PS(n)PtBA(2n) dendrimer-like copolymers based on polystyrene (PS) and poly(tert-butylacrylate) (PtBA) is described. The synthetic procedure involves a combination of atom transfer radical polymerization (ATRP) using multifunctional initiators and chain end modification reactions. These structures are composed of a PS core with 2, 4, 6, or 8 arms and a corona of PtBA with 4, 8, 12, or 16 arms, respectively. Third-generation PS(n)PS(2n)PtBA(4n) dendrimer-like copolymers were also derived by repetition of chain end modification and ATRP. Characterization was carried out by size exclusion chromatography online with multiangle laser light scattering and by H-1 NMR spectroscopy. PS(n)PAA(2n) amphiphilic structures based on PS and poly(acrylic acid) (PAA) were subsequently generated by hydrolysis of the tert-butylester groups. Langmuir monolayer studies of PS(n)PtBA(2n) showed the formation of stable films. AFM images demonstrated a significant change in morphology upon increasing surface pressures.

A facile concept to prepare nano-objects based on self-organizing polymeric supramolecules (also called supramolecular block copolymers) is demonstrated using one particular shape, i.e., nanorods or nanofibers. Cylindrical aggregates consisting of a polystyrene (PS) core and a thin corona of poly(4-vinylpyridine) (P4VP) chains are prepared from P4VP(pentadecylphenol)-block-PS comb-coil supramolecules. Diblock copolymers P4VP-block-PS are stoichiometrically (with respect to the number of pyridine groups) hydrogen-bonded with pentadecylphenol (PDP) amphiphiles to yield P4VP(PDP)-block-PS comb-coil supramolecules. By the selection of appropriate relative block lengths for P4VP(PDP) and PS, a micro-phase-separated cylindrical morphology of PS cylinders inside a P4VP(PDP) matrix is obtained. Subsequent removal of the amphiphiles, accounting for ca. 75% of the matrix material, results in cylinders with a core of PS and a corona of easily adjustable thickness of P4VP. The advantages of the present concept compared to the existing procedures are discussed.

International audience; Polymersomes are vesicles made of amphiphilic diblock copolymers. Giant polymersomes of several tens of microns in diameter can be prepared from low T(g) (glass transition temperature) flexible (coil-coil) copolymers by processes such as rehydration swelling or electroformation. These techniques are, however, inefficient in producing giant polymersomes composed of high T(g) and/or rigid-flexible (rod-coil) copolymers. We have used an alternative method based on the formation of an inverted emulsion to produce giant unilamellar rod-coil polymersomes. We have selected copolymers whose hydrophobic moieties are glassy liquid crystalline polymers. The viscoelasticity of individual polymersomes has been measured by micropipette aspiration. Whereas the elastic modulus was found to be of the same order of magnitude as the one of prototypical vesicles made of coil-coil copolymers, the membrane viscosity of this new class of polymersomes was about three orders of magnitude more viscous than their coil-coil counterparts. The versatile method used here to form giant polymersomes could be useful for designing and studying novel functional polymer capsules. The results highlight the possibility of widely tuning the mechanical properties of polymersomes by selecting or synthesizing the proper copolymer.