Collapse of Cylindrical Brushes with 2‐Isopropyloxazoline Side Chains Close to the Phase Boundary

A high‐molar‐mass cylindrical brush polymer with a main chain degree of polymerization of P_w = 1047 is synthesized by free‐radical polymerization of a poly‐2‐isopropyloxazoline macromonomer with P_n = 28. The polymerization is conducted above the lower phase transition temperature of the macromonomer, i.e., in the phase‐separated regime, which provides a sufficiently concentrated macromonomer phase mandatory to obtain high‐molar‐mass cylindrical brushes. Upon heating to the phase transition temperature, the hydrodynamic radius is observed to shrink from 34 to 27 nm. Further increase in temperature resulted in aggregated chains which were observed to coexist with single chains until eventually only aggregates of μm size were detectable.

     

Polymer Brushes with Phototriggered and Phototunable Swelling and pH Response

Photolabile polymer brushes with tailored length containing a photoremovable protecting group (NVOC) are prepared via the SI‐ATRP method. Upon light irradiation, the NVOC group is removed to generate controlled densities of free amine groups (PAMA) randomly distributed along the brush. The presence of the ionizable groups induces a photo‐triggered swelling response. The swelling degree can be tuned by the irradiation dose. A dual (light and pH), tunable response is demonstrated.

     

Biopolymers and biomaterials based on elastomeric proteins

Elastomeric proteins represent a very interesting subject of investigation, not only for their molecular mechanism(s) of elasticity, but also for their great potential as novel biomaterials. This review is intended to give an overview of the properties of the main elastic proteins, with particular focus on elastin and, at the same time, a report on the most recent acquisitions in the field of elastomeric biomaterials.

TEM image of poly(OrnGlyGlyOrnGly) after crosslinking reaction with GTA. The bar represents 100 nm.     

Effect of the Molecular Weights of Poly‐L‐Arginine on Membrane Strength and Permeability of Poly‐L‐Arginine Group Microcapsules

A novel poly‐L ‐arginine group microcapsule was produced to investigate its nutritional function and pharmacological efficacy. The molecular weight of poly‐L ‐arginine is an important parameter for its membrane strength, but does not obviously affect its release property. Thus, poly‐L ‐arginine can be used as a kind of new membrane material in microcapsules, and it is expected to be used as an therapeutic and biodegradable drug carrier.

Influence of the molecular weight of poly‐L ‐arginine on membrane thickness.     

Fluorescence Investigations of Oxygen‐Doped Simple Amine Compared with Fluorescent PAMAM Dendrimer

Blue emission of oxygen‐doped tertiary amine (triethylamine), a key unit of fluorescent poly(amido amine) dendrimer, was demonstrated. It was found that the fluorescence intensity could be further enhanced if the tertiary amines locate densely in the dendrimer interior as the branching sites. Moreover, a solvatochromic phenol blue, instead of oxygen, is able to induce the blue fluorescence of the tertiary amino‐branching sites based on a guaranteed host‐guest complexation of phenol blue molecules and dendrimer interior.

     

Construction of Large‐Scale Highly Ordered Macroporous Monoliths of π‐Conjugated Polymers

Large scale of well‐ordered macroporous π‐conjugated polymer monoliths have been successfully prepared through a new approach using micrometer‐sized naphthalene crystals as templates. The macroporous monoliths of poly(p‐phenylenevinylene) (PPV) and poly(p‐phenyleneethynylene) (PPE) grew along the unidirectional freezing direction inside the template naphthalene crystals which lead to the formation of controlling morphologies and homogeneous diameters. The polymer monoliths show straight and lamella macroporous structures. The diameters of pores and the thickness of pore walls can be controlled by tuning the freezing temperature.

     

Direct Synthesis of Poly(potassium 3‐sulfopropyl methacrylate) Cylindrical Polymer Brushes via ATRP Using a Supramolecular Complex With Crown Ether

A supramolecular complex between an ionic monomer 3‐sulfopropyl methacrylate (SPMAK) and crown ether 18‐crown‐6 (18C6) has been employed to prepare a strong anionic cylindrical polyelectrolyte brush poly(potassium 3‐sulfopropyl methacrylate) (PSPMAK) by atom transfer radical polymerization (ATRP) in polar solvent dimethyl sulfoxide (DMSO). This strategy solved the problem of the solubilities of the incompatible hydrophobic poly‐initiator and hydrophilic ionic monomer. The formation of the PSPMAK brush is well proven by ¹H NMR, aqueous gel permeation chromatography (GPC), dynamic light scattering (DLS), static light scattering (SLS), atomic force microscopy (AFM), and cryogenic transmission electron microscopy (cryo‐TEM) measurements. Cleavage of the side chains and further analysis reveal that the initiating efficiency of the polymerization is as low as 0.35.

     

Photoactive Modified Hydroxyethylcellulose

A water‐soluble polymeric photosensitizer that contains naphthalene chromophores and absorbs light in the near UV region was obtained by modification of hydroxyethylcellulose. The excitation energy migrates along the naphthalene chromophores covalently attached to the polymer chain and can be used to induce photochemical reactions such as photoinduced electron transfer.

UV‐vis absorption (○), fluorescence emission (□), and fluorescence excitation (×) spectra of HENC in water at c_HENC = 0.232 g/L, and (+) emission spectrum of the lamps used for irradiations.     

Stable Aqueous Dispersion of PEGylated Nanoparticles by Polyelectrolyte Complex Formation

Stable aqueous dispersions of nanoparticles were prepared by polyelectrolyte complex formation between well‐defined poly(ethylene glycol)‐block‐poly(2‐acrylamido‐2‐methyl‐1‐propane sodium sulfonate) and poly(ethylene glycol)‐block‐poly[2‐(dimethylamino)ethyl methacrylate] diblock copolymers. Controlled synthesis of the copolymers was achieved by water‐based atom transfer radical polymerization (ATRP). The nanoparticles were characterized by a quite narrow and monomodal size distribution as evidenced by dynamic light scattering (DLS) and confirmed by atomic force microscopy (AFM) after solution casting and freeze‐drying.

     

Preparation of Antimicrobial Ultrafine Cellulose Acetate Fibers with Silver Nanoparticles

Summary: A feasible method for the preparation of antimicrobial ultrafine fibers with silver nanoparticles was developed by direct electrospinning of a cellulose acetate (CA) solution with small amounts of silver nitrate followed by photoreduction. Silver nanoparticles in ultrafine CA fibers were stabilized by interactions with carbonyl oxygen atoms in CA. Ultrafine CA fibers with silver nanoparticles showed very strong antimicrobial activity.

TEM image of an ultrafine CA fiber electrospun from 10 wt.‐% CA solution with 0.5 wt.‐% AgNO₃.     

Multiphase‐Separated Polyurethanes Studied by Micro‐Raman Spectroscopy

Micro‐Raman spectroscopy has been used to investigate the chemical micro‐heterogeneity of multiphase‐separated poly(ether urethanes) (PETU). Analysis of PETU cross‐sections by means of micro‐Raman spectroscopy revealed the nearly complete absence of soft segments in AI aggregates (called globules). These aggregates are in the order of a few micrometers in size. The composition of the matrix and the AII aggregates (spherulites) was comparable.

Example of an AFM image (sample 706, scan size 25 μm, converted to monochromatic image).     

Block Copolymer Micellar Nanoreactors for the Directed Synthesis of ZnO Nanoparticles

We report the simple one‐pot synthesis of size tunable zinc oxide nanoparticles (ZnO NPs) out of an organometallic ZnO precursor using the self‐assembly of solution phase polystyrene‐block‐poly(2‐vinylpyridine) micelles. The resulting hybrid material could be deposited on various substrates in a straightforward manner with the NPs showing size‐dependent absorption and photoluminescence due to the quantum‐size effect. We compare the results to the assembly of preformed NPs which are selectively incorporated in the poly(2‐vinylpyridine) core of the micelles due to the high affinity of ZnO to vinylpyridine.

     

Magnetic Microcapsules with Low Permeable Polypyrrole Skin Layer

Summary: The paper describes a perspective approach to significantly decrease permeability of polyelectrolyte multilayered capsules and, therefore, to make them more efficient for encapsulation of small molecule species. The polyelectrolyte shell modification by a dense polymer (polypyrrole) provides the capsule shell with water‐resistant and sufficient barrier properties. However, high brittleness of polypyrrole coatings demands more gentle capsule processing conditions. Magnetite iron oxide nanoparticles were used as a shell constituent to provide the capsules with magnetic properties and, therefore, to propose a mild technological protocol for capsule treating.

CLSM image of TRITC filled PPy covered capsules prepared by magnetic sedimentation.     

A Magnetically Tunable Colloidal Crystal Film for Reflective Display

A general approach to fabricate a magnetic field responsive colloidal crystal film has been developed. This is carried out by depositing monodisperse Fe₃O₄/PS composite magnetic nanospheres on the surface of an agarose‐gel coated substrate. The optical properties of the resultant film can be easily controlled by an external magnetic field, which is caused by assembly of the magnetic nanospheres and alteration of the interparticle distance. With the help of a designed array of small magnets, both the color and pattern of the film can be conveniently modulated and the tuning range covers almost the whole visible spectrum. This work will be important for the potential application of monodisperse magnetic nanospheres in fabricating novel sensors, displays and optoelectronic devices.

     

Synthesis of Novel Thermo‐ and pH‐Responsive Poly(L‐lysine)‐Based Copolymer and its Micellization in Water

A series of novel temperature and pH responsive block copolymers composed of poly(N‐isopropylacrylamide) (PNIPAM) and poly(L ‐lysine) (PLL) were synthesized. The effect of pH and the length of PLL on the lower critical solution temperature (LCST) of PNIPAM, and the self‐assembly of these PLL‐based copolymers induced by temperature and pH changes were investigated by the cloud point method, dynamic light scattering (DLS) and environmental scanning electron microscopy (ESEM). These PNIPAM‐b‐PLL copolymers can self‐assemble into micelle‐like aggregates with PNIPAM as the hydrophobic block at acidic pH and high temperatures; and at alkaline pH and low temperatures, they can self‐assemble into particles with PLL as the hydrophobic block. The copolymers may have potential applications in biotechnological and biomedical areas as drug release carriers.

     

Synthesis and Self‐Assembly of Amphiphilic Diblock Copolymers using a Fluorescently Labeled N‐Alkoxyamine Initiator

Summary: An initiator for nitroxide mediated ‘living’ free radical polymerization was prepared with a fluorescent tag attached to the initiating alkyl radical terminus. This was used to synthesize amphiphilic poly(acrylic acid)‐block‐polystyrene diblock copolymers, which self assembled in a tetrahydrofuran/buffer solution to form structures that are visible by fluorescence.

     

Novel Structured Composites Formed from Gold Nanoparticles and Diblock Copolymers

We report a simple procedure to prepare a novel Au‐micelle composite with a core‐shell‐corona structure. This composite is prepared by reduction of tetrachloroauric acid (HAuCl₄ · 3H₂O) in dilute aqueous solution containing polystyrene‐block‐poly(4‐vinylpyridine) micelles and poly(ethylene oxide)‐block‐poly(4‐vinylpyridine) copolymers. The micelles with a polystyrene core and a poly(4‐vinylpyridine) shell are transformed into Au‐micelle composites with a polystyrene core, a swollen hybrid Au/poly(4‐vinylpyridine) inner shell, and a poly(ethylene oxide) corona by direct physisorption of gold particles with poly(4‐vinylpyridine) chains.