A two‐step method for the preparation of spherical polyelectrolyte brushes (SPBs) has been developed. Copolymerization of styrene and divinyl benzene at the particle surface resulted in a large number of accessible vinyl groups. These vinyl groups reacted with sodium styrene sulfonate to give SPBs. The SPBs were used as carriers for conducting polymers resulting in redispersible conducting inks with good film forming properties. Direct current (DC) conductivity of the polypyrrole (PPy) loaded samples showed a percolating behavior as probed by impedance spectroscopy. Finally, device performance of organic light‐emitting diodes based on the conducting thin films assembled from the PPy loaded particles was tested.
Branched α‐olefin 4‐methyl‐1‐pentene (4MP) is polymerized with a cationic α‐diimine palladium catalyst. The influences of polymerization parameters including reaction temperature and monomer concentration on polymer architecture are evaluated in detail. Increasing temperature and lowering monomer concentration can lead to the formation of more complex branched polyolefin because of chain walking. At 0 °C, complex branched polyolefins are generated from quasi‐living polymerization of 4MP with α‐diimine palladium catalyst.
Well‐defined diblock poly(L ‐lactide)‐block‐poly(dimethylamino‐2‐ethyl methacrylate) (PLLA‐b‐PDMAEMA) copolymers were synthesized by combining ROP of LLA and ATRP of DMAEMA, from a dual‐initiator 2‐hydroxylethyl 2‐bromoisobutyrate. The molecular characterization of these diblock copolymers was performed using 1H NMR, FT‐IR, and GPC‐MALLS analysis. The responsive behavior of these diblock copolymers in aqueous solutions at different pH and temperatures were investigated using DLS. Results show that both higher pH and temperature result in a higher degree of neutralization, weaker hydrogen bonding, and micellar aggregation. As observed by TEM, changes in micellar morphology are in accordance with DLS results.
Hyperbranched aliphatic polyesters functionalized with carboxylic or sulfonic acid groups have been synthesized and employed as crystallization modifiers for calcium carbonate. The functionalized polyesters exhibit remarkable polymorph selectivity and morphology control. Stable spherical vaterite particles of diameter less than 10 µm with narrow size distribution were easy to produce on a large scale. With an increase in the concentration and monomer/core ratio of the polyester, the vaterite content increases accordingly with promoted morphology control to monodisperse spheres. The CaCO3 concentration and the initial pH can also influence the morphology and polymorphism of the produced calcium carbonate. Under certain conditions, well‐defined core‐shell structured vaterite spheres are obtained with obvious radial organization by nano‐aggregation of about 70 ± 10 nm crystallites, which may mediate and combine the nano‐aggregation and crystal growth formation mechanism of vaterite polymorph.
Preparation of discrete PPPI microspheres was examined using the crystallization of oligomers during isothermal polymerization of PMDA and p‐phenylene diisocyanate, and that of pyromellitic dithioanhydride and PPDA in poor solvents. In contrast to PPPI microspheres with smooth surfaces that were previously prepared by phase‐separation during the polymerization of PPDA and PMDA, the microspheres obtained here consisted of flake‐like lamellae with rugged surfaces. The diameters of the microspheres ranged from 0.5 to 6.7 µm. They exhibited excellent thermal stability depending on the monomers. These results provide a new preparative procedure of the PPPI microsphere with a rugged surface.
Two‐dimensional chromatographic methods were developed using LC‐CC in the first and SEC in the second dimension. These methods were applied for the investigation of PS‐b‐PI diblock copolymers synthesized by different approaches: sequential living anionic polymerization and coupling of living precursor blocks. The first dimension separates according to the individual block length of PS or PI blocks, whereas the second dimension separates with respect to the total molar masses of components. 2D‐LC analysis provides information on the purity of the reaction products, the presence of by‐products, the chemical compositions and the molar masses of all product components. The accuracy and selectivity of 2D‐LC is discussed.
Various polyurethane‐based SMPUs were synthesized using five types of polyols as soft segments and two different diisocyanates as hard segments. The effects of diisocyanate concentration on material properties such as crystallinity, transition temperature, shape‐memory effect and tensile strength were investigated. SMPUs with a maximum strain near 1 000%, recovery rate up to ≈98%, fixity up to ≈90% and Tgs of 35–45 °C were obtained. A high MDI content results in SMPUs with better shape‐memory effect, whereas increasing IPDI content leads to a weaker shape‐memory effect. High IPDI concentration seems to prevent or restrict chemical reactions and crosslinks between the polyols and the hard segments, leading to large phase separation and coexistence of soft and hard segments in the macrophases.
Terpyridine‐modified hydrophobic poly(dimethylsiloxane) and hydrophilic poly(ethylene oxide) were combined to new metallo‐supramolecular AB‐diblock copolymers by utilizing Ru(II) ions. The polymers were synthesized by hydrosilylation of heteroleptic allyloxy‐functionalized Ru(II) complexes. The amphiphilic AB‐diblock copolymers were used to prepare micelles in an aqueous environment, which were subsequently characterized by dynamic light scattering and cryogenic transmission electron microscopy.
PHA‐based nano‐biocomposites have been prepared by melt intercalation. Two main PHAs, poly(hydroxybutyrate) and poly(hydroxybutyrate‐co‐hydroxyvalerate) have been studied. Structural characterizations were conducted by advanced techniques like SAXS and TEM. A recent method has determined the degree of clay intercalation and dispersion using solid‐state NMR. Well intercalated small tactoids (3–10 layers) homogeneously dispersed into the polymer are obtained when good PHA–clay affinity exists, i.e., with organo‐modified MMT. In the case of non‐modified MMT, microcomposites are evidenced. Crystallization, mechanical, and thermal properties have been correlated to the materials structures.
Photoreorientation of a stripe pattern consisting of an MPS structure in a Langmuir‐Blodgett monolayer by irradiation with linearly polarized light is achieved for the first time using a PDMS/poly(methacrylate) diblock copolymer with a liquid crystalline azobenzene‐containing side chain. The stripe MPS pattern in the trans azobenzene state is diminished by photoisomerization to the cis form upon UV light irradiation. By the erasure of the MPS structure, the anisotropic photo‐oriented stripe pattern is generated upon irradiation with linearly polarized visible light, the orientation of the stripe pattern being orthogonal to the electric vector of the light.
A π‐conjugated polymer having 1,4‐bismercapto‐substituted 1,3‐diene units in the main chain was prepared by the novel polymer reaction of a regioregular organometallic polymer having titanacyclopentadiene‐2,5‐diyls units with benzenesulfenyl chloride. The number‐average molecular weight and the molecular weight distribution of the polymer derived from 1,4‐diethynyl‐2,5‐di(2‐ethylhexyloxy)benzene were estimated to be 5 700 and 1.6, respectively, from the GPC analysis. The π‐conjugated character, photoluminescence behavior both in solid‐state and solutions, and the electron‐donating properties of the π‐conjugated polymer are discussed on the basis of its UV‐vis spectrum, photoluminescence spectrum, and CV analysis.
Spontaneous deposition of fluorescein isothiocyanate labeled dextran (FITC‐dextran) in covalently assembled poly(glycidyl methylacrylate) (PGMA)/poly(allylamine hydrochloride) (PAH) microcapsules was studied and its mechanism was proposed. Incubation of the microcapsules in the FITC‐dextran solution resulted in strong fluorescence emission from the capsule interiors. The deposition was found to be molecular weight ( ) dependent and the number of capsules filled with FITC‐dextran was increased along with the of FITC‐dextran. Furthermore, the correlation between the deposited substances and the charged species in the capsules was explored quantitatively through UV–Vis and fluorescence spectroscopy.
High‐molecular‐weight polythiocaprolactone (PTCL) was prepared in a green process via lipase‐catalyzed ROP of a cyclic 6‐mercaptohexanoic acid (6MH) oligomer. PTCL was readily depolymerized by lipase to cyclic 6MH in dilute toluene solution, which was then readily repolymerized by the same lipase to produce PTCL with the same $\overline {M} _{{\rm w}} $ as the initial PTCL in a chemical recycling process. The Tm of PTCL was higher than that of the corresponding PCL. A P(TCL‐co‐CL) copolymer with 60 mol‐% TCL (6MH) units showed a higher Tm as the PCL homopolymer. Similar apparent Km values were obtained for the cyclic 6MH oligomers and caprolactone oligomers, however, the Vmax of cyclic 6MH oligomers was significantly lower than that of the corresponding caprolactone oligomers.
Synthesis and characterization of a series of new emissive flexible copolymers composed of two kinds of special side‐chain functional groups is demonstrated. One of the side‐chain groups provides emissive properties, while the other serves as the ligand unit. The copolymers are used to prepare a new kind of CdTe nanocrystal‐based semiconductor nanocomposite. Their structures and morphologies are characterized and their optoelectronic properties are studied. The results reveal that an energy‐transfer process from the emissive random copolymers to the CdTe nanocrystals occurs, while a photoinduced charge transfer is estimated to be thermodynamically forbidden.
Magnetite nanoparticles are synthesized and functionalized with vinyl groups (by silanization reaction with VTMS) and further coated with poly(ethylene glycol) dithiol under UV activation via thiol‐ene addition. TEM analysis is in a good agreement with DLS analyses and shows that by vinyl functionalization and following PEG coating it was possible to achieve nanometer‐sized particles with an average size of about 20–50 nm, well distributed and not‐aggregated. Superparamagnetic‐like behavior of coated Fe3O4 nanoparticles, which is typically looked for in biomedical applications, is ensured by the Brownian motion of the magnetic NPs in the ferrofluid. The polymeric coating does not modify the magnetic response of the magnetite nanoparticles.
Alkynyldextrans with a DS in the range 0.1–1.67 have been prepared as reactive intermediates for further polymer‐analogous functionalisation. DS and substituent distribution were determined by GLC and GLCMS after hydrolysis and acetylation, or methanolysis and trimethylsilylation. Reactivity was in the order O‐2 > O‐4 ≥ O‐3 with pronounced differences in the distinct patterns for propargyl ethers and its higher homologous. A large deviation from a random substituent distribution was observed. Propargyldextrans were not stable during long‐time storage in the solid state, while terminal pentynyl and hexynyl ethers are. Pentynyldextrans showed structure formation of various geometries. They bound silver efficiently, yielding silver nanoparticles by reduction.
We report the large scale preparation of nanostructured polyaniline‐Pd nanoparticles composites (designated as PANI(NS)‐PdNPs) through a “seed” induced bulk polymerization. Initially, a small quantity of PANI(NS)‐PdNPs was formed inside the cavities of MCM‐41 and used as the “seed” for the bulk preparation of PANI(NS)‐PdNPs composite. For a comparative purpose a PANI‐PdNPs composite was also prepared in the absence of the seed. FESEM image of PANI(NS)‐PdNPs composite (bulk) shows nanofibrillar morphology. Further, transmission electron microscopy reveals the presence of spherical Pd nanoparticles. PANI(NS)‐PdNPs composite (bulk) showed a good catalytic activity towards reduction of 4‐nitrophenol.
Self‐assembly has emerged as a powerful approach to control nanostructure in materials containing globular proteins, both through templated self‐assembly and direct self‐assembly of globular protein‐polymer conjugates or fusion proteins. The folded structures of globular proteins that are critical to their function introduce complex shapes and interactions into block copolymers that significantly alter the physics of self‐assembly. This article discusses the different methods for controlling the nanostructure of globular proteins using block copolymers, highlighting efforts at understanding the physics of self‐assembly in concentrated solution and solid‐state bioconjugate copolymers.
Colloidal nanosized folate‐conjugated hydrogels for targeted chemotherapy were prepared via a versatile and efficient postsynthetic modification pathway starting from P(NPA‐co‐NIPAM). The modifications included the introduction of 4‐methylpyridine as pH‐sensitive pendant groups and the conjugation of folic acid to the microgel network. The microgels showed a specific swelling at pH < 6 (endosomes) as judged by DLS studies varying the external pH. The relative composition of the microgels shows a clear influence on the pH volume transition shifting. The potential of the microgels for anticancer drug release at pH = 5.0 was confirmed. Therefore, they are a promising targeting carrier for improved anticancer chemotherapy.
Reverse‐micelle‐like CAMs derived from HPEI, which exist as either aggregates or unimolecular micelles, show selectivity upon the encapsulation of water‐soluble and ionic dyes. For rigid dyes, the encapsulating ability is very weak, while for less rigid ones, the encapsulation is dependent on their electronic properties. Through electronic engineering of the CAM, the complementary CAM/dye interaction strengths can be greatly favored or disfavored. Electronic engineering of the CAM can also exert a non‐linear effect on the guest affinities and thus amplify the difference of the competitive guest species and further lead to highly selective encapsulations. Even if one dye species is complexed by another dye species, highly selective encapsulation can still be realized by a CAM.
