Semiflexible grafted polymers in poor solvents: toroidal, archway, and tower micelles

We study a system of grafted semiflexible polymers in a poor solvent which form toroidal or rodlike conformations in the bulk. However, because of the physical constraint of surface grafting, macrophase separation is inhibited and a number of different polymer aggregates (or micelles) form which can be related to the chains' stiffness and their affinity for each other. In contrast to the fully flexible Gaussian case, we observe a number of novel micelle structures, including tower micelles, archway micelles, and spider micelles. We also attempt to develop a phase diagram for the occurrence of these structures with respect to the variables of chain length, chain stiffness, and polymer grafting density.     

Interfacial micellar structures from novel amphiphilic star polymers

An amphiphilic heteroarm star polymer containing 12 alternating hydrophobic/hydrophilic arms of polystyrene (PS) and poly(acrylic acid) (PAA) connected to a well-defined rigid aromatic core was studied at the air-water and the air-solid interfaces. At the air-water interface, the molecules spontaneously form pancakelike micellar aggregates which measure up to several microns in diameter and 5 nm in thickness. Upon reduction of the surface area per molecule to 7 nm2, the two-dimensional micelles merged into a dense monolayer. We suggest that confined phase separation of dissimilar polymer arms occurred upon their segregation on the opposite sides of the rigid disklike aromatic core, forcing the rigid cores to adopt a face-on orientation with respect to the interface. Upon transfer onto solid supports the PS chains face the air-film interface making it completely hydrophobic, and the PAA chains were found to collapse and form a thin flattened underlayer. This study points toward new strategies to create large 2D microstructures with facial amphiphilicity and suggests a profound influence of star molecular architecture on the self-assembly of amphiphiles at the air-water interface.     

Monolayers and membranes from amphiphilic polymers

Nanometer thin, elastomeric membranes with considerable application potential in micro mechanics and materials science can be prepared by transferring monomolecular layers of polymers with ionic head groups from the water surface to solid substrates with holes. If monolayers of liquid polymers are transferred to substrates with openings they initially cover the openings, but finally rupture within a couple of minutes after transfer. However, if the polymer monolayers are stabilised by vitrification, chemical or physical cross-linking, they can be transferred to cover openings in solids substrates as stable membranes. Especially if monolayers of low glass transition polymers are cross-linked, elastomeric membranes are obtained, which might find application in micro mechanical devices like membrane valves and pumps. Incorporation of either a second, incompatible polymer or hydrophobised colloids leads to laterally structured and porous membranes.     

Preparation and properties of some water-soluble,comb-shaped,amphiphilic polymers

Water-soluble comb-shaped polymers were prepared through grafting of poly(ethylene glycol) monomethyl ethers (MPEG) onto acrylic and methacrylic ester copolymers by transesterification reactions. The grafting was alkali-catalyzed, and performed in refluxing toluene solution or in melt at 155°C. The grafting efficiency was found to be on the order of 1 graft/10 monomer units. Epoxy groups in glycidyl methacrylate copolymers were also utilized for grafting. The crude graft copolymers were purified through chromatography and characterized by NMR and IR spectroscopy. Polymers prepared from MPEG 2000 were crystalline with melting points 10–15°C lower than the MPEG used. All polymers were shown to be surface active with CMC on the order of 1.5 g/L, and surface tensions of 38–45 dyn/cm. When used as emulsifiers the graft copolymers containing bulky lipophilic ester groups (2-ethylhexyl t-butyl) gave oil-in-water (o/w) and water-in-oil (w/o) emulsions from xylene/water with higher stability than those containing straight chain ester groups (methyl nbutyl n-docecyl). The most stable emulsions were obtained by dissolving the polymers in the organic phase.     

New amphiphilic polymers: Poly(N-alkylacrylamide-CO-vinylpyridinium)

A series of new amphiphilic polymers containing various amounts of N-methyl-4-vinylpyridinium units as hydrophilic part and N-dodecylacrylamide or N-decylacrylamide units as hydrophobic part have been prepared by quaternizing the cognate copolymers. Their behaviour in aqueous solutions has been studied by viscometry, as well as by fluorescence spectroscopy and tensiometry. Results are discussed in detail and a conformational model of the macromolecules at the interface (water/methylcyclohexane) is proposed in relation to the formation of microdomains in the aqueous media.     

New comb-like polymers: Synthesis,structures and reactivity

Comb-like polymers have been widely investigated mainly to correlate their structures with the thermal behaviour. Our interests are directed on the synthesis of new types of comb-like polymers bearing reactive groups in the side chains, main chain or as end groups. One part of the investigations deals with the behaviour of photosensible polymers containing azobenzene, cinnamic acid and mesoionic moieties. The use of enzymes as catalysts for the synthesis of new methacrylic derivatives and for the modification of polymers illustrates a fascinating contribution to polymer chemistry. The classical Diels-Alder addition was also used for the synthesis and modification of polymers. Finally, the construction of polymers containing rotaxanes in the side chains is presented.     

Design,synthesis, and surface activity of amphiphilic perfluorinated oxazoline polymers

Polymers derived from 2-[2-(perfluoroalkyl)ethyl]-2-oxazolines have been prepared in very good yields with molecular weights up to 50000. The polymers are crystalline with melting temperatures (Tm's) varying from 180 to 232°C depending on the length and type of the perfluorinated side chain, have good thermal stability and are soluble in fluorinated solvents. They are effective as modifiers of surfaces of hydrophilic polymers, such as nylon-6,6, and give acceptable complement activation parameters. Factor C3a (μg/ml) released is 5.3 in contrast to positive control value of 45.2 (activated sepharose) and negative control = 4.8. A 1:1 mixture of 2-octyl-2-oxazoline and 2-[2-(perfluorohexyl)ethyl]-2-oxazoline copolymerize to give a block copolymer that exhibits two separate Tm's. The partially perfluorinated polymers also form stable monolayers at air-water interface.     

Polymersome‐forming amphiphilic glycosylated polymers: Synthesis and characterization

Copper‐catalyzed azide‐alkyne cycloaddition (CuAAC) was used to prepare glycosylated polyethylene (PE)–poly(ethylene glycol) (PEG) amphiphilic block copolymers. The synthetic approach involves preparation of alkyne‐terminated PE‐b‐PEG followed by CuAAC reaction with different azide functionalized sugars. The alkyne‐terminated PE‐b‐PEG was prepared by etherification reaction between hydroxyl‐terminated PE‐b‐PEG (M_n ～ 875 g mol^?1) and propargyl bromide and azidoethyl glycosides were prepared by glycosylation of 2‐azidoethanol. Atmospheric pressure solids analysis probe‐mass spectrometry was used as a novel solid state characterization tool to determine the outcome of the CuAAC click reaction and end‐capping of PE‐b‐PEG by the azidoethyl glycoside group. The aqueous solution self‐assembly behavior of these amphiphilic glycosylated polymers was explored by TEM and dye solubilization studies. Carbohydrate‐bearing spherical aggregates with the ability to solubilize a hydrophobic dye were observed. The potential of these amphiphilic glycosylated polymers to self‐assemble via electro‐formation into giant carbohydrate‐bearing polymersomes was also investigated using confocal fluorescence microscopy. An initial bioactivity study of the carbohydrate‐bearing aggregates is furthermore presented. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5184–5193     

Imparting nanoparticle function with size-controlled amphiphilic polymers

Herein we report our method of water solubilization and subsequent functionalization of a variety of nanoparticle systems with amphiphilic polymers containing build-in "chemical handles". We have used these polymers, which have narrow polydispersity indices, to impart water solubility and chemical sensitivity toward targeted species (here: pH). These material systems have high chemical conjugation efficiencies in aqueous conditions which may be used to create a variety of chemical and biological multifunctional materials.     

Double-polyelectrolyte, like-charged amphiphilic diblock copolymers: swollen structures and pH- and salt-dependent lyotropic behavior

We consider a symmetrical poly(styrene- stat-(acrylic acid))- block-poly(acrylic acid), i.e., PSAA- b-PAA, diblock copolymer, with a molar fraction phi AA = 0.42 of acrylic acid, in the more hydrophobic PSAA statistical first block. We investigate its structural behavior at constant concentration in water using small-angle neutron scattering (SANS) by varying (i) the ionization of its acrylic acid motives via the pH by adding NaOH and (ii) the ionic strength of the solution by increasing the NaCl salt concentration c S. We present the resulting morphological phase diagram {pH, c S}, in which we identified two different lamellar phases presenting a smectic long-range order at small-to-intermediate ionizations and a spherical phase with a liquid-like short-range order at larger ionization. In the low-ionization regime, the first lamellar phase comprises a water-free PSAA lamellar core surrounded by a dense poly(acrylic acid) brush swollen with water. Its mostly hydrophobic core still being glassy, this phase is unable to reorganize and is frozen in. A detailed analysis of the SANS data shows the osmotic nature of the polyelectrolyte brush, in which the Na+ counterions are confined so that local electroneutrality is satisfied. Above the pH at which the PSAA statistical block starts ionizing, the PSAA lamellar core melts. The second lamellar phase identified then comprises a PSAA core thinner than that of the frozen-in previous phase, implying a significant increase of the core/water interface and a decrease of the brush surface density. The transition from the first lamellar phase to the second one can be quantitatively shown to result from the balance between the two contributions: (i) the extra interfacial cost between the thinner core and water and (ii) the associated gain in entropy of mixing for the counterions confined inside the brush. At even higher ionization, the diblocks finally form spherical objects with a very small, pH-dependent aggregation number and reach an apparent onset of self-association. When the highest ionization investigated is reached, the cores of these final spherical core-shell objects are found to contain a significant amount of water. We thereby demonstrate that at constant concentration, pH, and ionic strength both trigger a transition from frozen to molten hydrophobic phases as well as unexpected morphological transitions.     

Disclinations in systems of amphiphilic molecules: Cubic structures

Possible ordered geometrical configurations with bicontinuous or cellular topologies, optimizing the frustration of a periodic system of frustrated fluid films, are analyzed in terms of topological defects. The solutions found have the same symmetries as those observed for cubic phases of amphiphilic molecules. This agreement leads to consider the latter as structures of defects of rotation, or disclinations.     

Coordination polymers with adamantanediacetate bridges: syntheses, structures, and magnetic properties

Abstract  Two new coordination polymers, [CoL(bpp)] _n (1) and [MnL(bipy)] _n ·0.25nH₂L·0.5nH₂O (2) (H₂L = 1,3-adamantanediacetic acid, bpp = 1,3-bis(4-pyridyl)propane, bipy = 4,4′-bipyridine), were synthesized and characterized by single crystal X-ray diffraction, IR spectroscopy, and thermal analysis. Complex 1 is an one-dimensional (1D) chain structure of Co(II) bridged by L²⁻ as well as bpp. Complex 2 consists of a two-dimensional (2D) (3,6)-connected topology layer structure. Variable temperature magnetic susceptibility measurements in the range of 2–300 K reveal the existence of weak antiferromagnetic interactions in two complexes with J = −1.74 cm⁻¹, g = 2.26 for 1 and J = −0.10 cm⁻¹, g = 1.67 for 2. Index abstract  Two mental-organic frameworks, namely [CoL(bpp)] _n (1) and [MnL(bipy)] _n ·0.25nH₂L·0.5nH₂O (2) (H₂L = 1,3-adamantanediacetic acid, bpp = 1,3-bis(4-pyridyl)propane, bipy = 4,4′-bipyridine), have been synthesized based on 1,3-adamantanediacetic acid and N-donor coligand with metal ions Co(II) and Mn(II). The magnetic measurement of the two polymers reveals typical antiferromagnetism exchange. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Phase behavior of amphiphilic polymers: A dissipative particles dynamics study

Dissipative particle dynamics is a mesoscopic simulation method which allows one to predict the self-assembly of amphiphilic polymers and surfactants. It was possible to reproduce the formation of microemulsions of the oil/water (o/w), water/oil (w/o), and L₃-type of C10E4 in water and n-decane with excellent accuracy. We are able to predict the experimentally not investigated emulsion formation of a poly(ethylene butylene)–poly(ethylene oxide) in water and methylcyclohexane.     

Rational design of amphiphilic polymers to make carbon nanotubes water-dispersible, anti-biofouling, and functionalizable

We report rational design of amphiphilic polymers capable of making carbon nanotubes (CNTs) highly water dispersible and resistant to biofouling; such CNTs can be conjugated with bioactive molecules so as to be potential drug delivery vehicles.     

Criss‐cross amphiphilic polymers and analogous model systems

A new class of amphiphilic polymers carrying two pendant docosyl (C22) chains, located at periodic intervals that are separated by PEG chains of varying lengths, was synthesized via a simple melt‐transesterification polymerization, using dimethyl, 2,5‐didocosyloxyterephthalate as one of the monomers. DSC, variable temperature FT‐IR, and WAXS studies demonstrated that immiscibility between the pendant docosyl units and the backbone PEG segments drives their self‐segregation; this results in the crystallization of the pendant docosyl segments and the generation of a lamellar morphology with the alkyl segments and the PEG chains occupying alternate layers. Based on the study of model criss‐cross amphiphiles that resemble the polymer repeat unit, it is postulated that the chains reconfigure such that both the docosyl chains fold to one side of the terephthalate unit while the PEG segments form a loop on the other side; these chains then organize in a bilayer to form the lamellar structure. The simplicity of the synthesis and the rather unique properties of these polymers suggests that such a design could be translated to develop other interesting functional materials that could exploit the immiscibility‐driven microphase separation for the generation of sub‐10 nm domains; these could have potential applications, such as in membranes, solid polymer electrolyte formulations, and so forth. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1554–1563     

Highly congested liquid crystal structures: dendrimers, dendrons, dendronized and hyperbranched polymers

In this tutorial review we describe some studies concerning liquid crystal dendritic polymers. We have chosen to present several representative examples that illustrate the diverse kinds of LC dendritic structures, namely: dendrimers, dendrons, dendronized polymers and hyperbranched polymers. We review their synthesis, mesogenic properties and the way that they are arranged to form supramolecular liquid crystal assemblies.     

Forming biocompatible and nonaggregated nanocrystals in water using amphiphilic polymers

High-quality nanocrystals formed in organic solvents can be completely solubilized in water using amphiphilic copolymers containing poly(ethylene glycol) or PEG. These copolymers are generated using a maleic anhydride coupling scheme that permits the coupling of a wide variety of PEG polymers, both unfunctionalized and functionalized, to hydrophobic tails. Thermogravimetric analysis, size exclusion chromatography, cryogenic transmission electron microscopy, and infrared spectroscopy all indicate that the copolymers effectively coat the nanocrystals surfaces. The composite nanocrystal-polymer assemblies can be targeted to recognize cancer cells with Her2 receptor and are biocompatible if their surface coatings contain PEG. In the particular case of semiconductor nanocrystals (e.g., quantum dots), the materials in water have the same optical spectra as well as quantum yield as those formed initially in organic solutions.     

Novel one-dimensional polymers generated from p-Ferrocenylbenzoate: syntheses, structures, and magnetic properties

Treatment of p-ferrocenylbenzoate [p-HOOCH4C6Fc, Fc = (eta5-C5H5)Fe(eta5-C5H5)] with Mn(OAc)2 x 2H2O or Cd(OAc)2 x 2H2O afforded one-dimensional linear chain polymer [[Mn(OOCH4C6Fc)2(mu2-OH2)(H2O)2](H2O)]n (1), double-bridge polymer [Mn(mu2-OOCH4C6Fc)2(phen)]n (phen = phenanthroline) (2), and ladderlike framework [[Cd(mu2-OOCH4C6Fc)(eta2-OOCH4C6Fc)(bbp)](CH3OH)]n (bbp = 4,4'-trimethylene-dipyridine) (3). The solution-state cyclic voltammograms indicate that the half-wave potentials of the ferrocenyl moieties in these polymers are all shifted to positive potential compared to that of sodium p-ferrocenylbenzoate. Both 1 and 2 behave as 1D Heisenberg Mn(II) chains with weak intrachain antiferromagnetic interactions between the local high-spin Mn(II) ions, and the exchange coupling parameters J (-5.20 and -3.25 cm(-1) for 1 and 2, respectively) are larger than those of most of the reported di-Mn(II) complexes that contain mu2-aqua and mu2-carboxylato units and one-dimensional Mn(II) carboxylic polymers.     

Recent advances in acetylene-based helical oligomers and polymers: Synthesis,structures, and properties

In this review, we describe the recent advances in the chemistry of helical polymers and oligomers containing acetylene units in the main chain. Owing to their great benefits such as high availability and handleability, good reactivity, rigidity, linearity, and low bulkiness, acetylene units have been utilized and incorporated in helical folding oligomers and polymers such as oligo- and poly(m-phenylene ethynylene)s. General synthetic methods as well as the structures, functions, and properties of acetylene-based helical oligomers and polymers are discussed by focusing on recent examples from 2009 to 2017.