Poly(4‐methyl‐2‐pentyne) (PMP)/TiO2 hybrid nanocomposite membranes have been investigated for natural gas conditioning. Tailor‐made PMP with 35% cis‐content was identified as an attractive material to prepare nanocomposite membranes; it presented good stability towards organic vapors and optimal properties for butane/methane separation. The PMP/TiO2 hybrid nanocomposite membranes presented an improvement of butane permeability and butane/methane selectivity. The addition of TiO2 nanoparticles to the PMP enhanced the selectivity more effectively than fumed‐silica, and it is attractively higher than those currently reported in the open literature.
The micellization on surfaces of two series of quasi‐diblock copoly(2‐oxazoline)s consisting of 2‐phenyl‐2‐oxazoline (PhOx) segments linked to either 2‐methyl‐2‐oxazoline (MeOx) or 2‐ethyl‐2‐oxazoline (EtOx) segments is investigated in detail. Those micelles are not pre‐existing in the initial ethanol solution but are formed during the spin‐coating process by the evaporation of the solvent inducing the precipitation of the less soluble PhOx segments. The morphology and size of the surface micelles vary according to the fraction of PhOx in the copolymers. Moreover, it is demonstrated that the chemical nature of the more soluble MeOx or EtOx segments also has an influence on the morphology of the resulting surface micelles.
Clickable poly(ethylene glycol) (PEG) derivatives are used with two sequential aqueous two‐phase systems to produce microsphere‐based scaffolds for cell encapsulation. In the first step, sodium sulfate causes phase separation of the clickable PEG precursors and is followed by rapid geleation to form microspheres in the absence of organic solvent or surfactant. The microspheres are washed and then deswollen in dextran solutions in the presence of cells, producing tightly packed scaffolds that can be easily handled while also maintaining porosity. Endothelial cells included during microsphere scaffold formation show high viability. The clickable PEG‐microsphere‐based cell scaffolds open up new avenues for manipulating scaffold architecture as compared with simple bulk hydrogels.
The amphiphilic triblock copolymer PLA‐b‐PLL‐b‐MPEG is prepared in three steps through acylation coupling between the terminal amino groups of PLA‐b‐PZLL‐NH2 and carboxyl‐terminal MPEG, followed by the deprotection of amines. The block copolymers are characterized via FT‐IR, 1H NMR, DSC, GPC, and TEM. TEM analysis shows that the triblock polymers can form polymeric micelles in aqueous solution with a homogeneous spherical morphology. The cytotoxicity assay indicates that the final triblock polymer micelles after deprotection show low cytotoxicity against Bel7402 human hepatoma cells. MPEG and PLL were introduced into the main chain of PLA affording a kind of ideal bioabsorbable polymer materials, which is expected to be useful in drug and gene delivery.
The synthesis and phase behaviour of PB32 is reported. The results indicate that PB32 develops a low‐ordered smectic mesophase of the type SmCalt. The slow formation of such a mesophase allows the quenching of the isotropic melt into an amorphous state so that both amorphous glass and smectic glass can be obtained, which exhibit different glass‐transition temperatures. Mechanical tests indicate that the macromolecular chains in the mesophase of PB32 can be oriented either parallel or perpendicularly in relation to the streching direction, depending on the deformation conditions. Solid‐state 13C NMR spectroscopy results show that the mobility of the chains is rather similar in both phases.
Biodegradable supermacroporous PHEMA cryogels were produced by combining two crosslinkers, poly(ethylene glycol) diacrylate and a newly developed disulfide water soluble crosslinker, N,N′‐bis(methacryloyl)‐L ‐cystine. The biodegradable PHEMA cryogels were prepared with gel fraction yields up to 70% and were characterized by highly interconnected pores of micrometer size and good mechanical stability. When subjected to reductive agents like DTT, the biodegradable PHEMA cryogels disintegrated into small pieces. The rate of disintegration was controlled by the crosslinking density in the cryogels and the DTT concentration.
The preparation of poly[2,6‐(1,4‐phenylene)‐benzobisimidazole] (PPBI) nanofibers was examined using the crystallization of oligomers during isothermal polymerization of self‐polymerizable 2‐(1,4‐carbophenoxyphenyl)‐5,6‐diaminobenzimidazole. The polymerization was carried out at 350 °C at a concentration of 1wt.‐% for 6 h in three kinds of solvent. The solvent influenced the morphology of PPBI precipitates significantly, and PPBI nanofiber networks were successfully formed in DBT, of which the width ranged from 30 to 110 nm. Molecules were aligned along the long axis of nanofibers. A fibrillar morphology with molecular orientation is ideal for high performance materials such as reinforcements, non‐woven fabrics and so on. The nanofiber networks exhibit the highest thermal stability.
AFM imaging was used to investigate the influence of molecular structure and composition on the formation of Langmuir monolayers by arborescent PS‐graft‐PEO copolymers at the air/water interface. Even without compression, these molecules associate spontaneously at the air/water interface and form stable monolayers that are easily transferred onto solid substrates as Langmuir/Blodgett films. The copolymers either form aggregates with a low association level, large island‐like clusters, or ribbon‐like superstructures. The different behaviors of the copolymers are rationalized in terms of the influence of their composition and of the structure of the arborescent PS cores on the assembly process.
A new range of end‐functionalized poly(1,1,2,2‐tetrahydroperfluorodecyl acrylate)s was synthesized by ATRP. Such macromonomers were used as reactive and steric stabilizers for the preparation of original core‐shell polyurethane particles in supercritical carbon dioxide. The nature of the chain end functionality, as well as the molar mass of the reactive stabilizer, were varied in order to investigate the role of such parameters on the properties of the resulting materials. Due to the low surface energy of PFDA combined with the high surface roughness induced by the specific microstructure of particles deposited on a silica plate, PUR materials exhibited super‐hydrophobic behavior with a water CA above 150°.
The Ni‐catalyzed polymerization of P3AOTs was studied and compared with the controlled chain‐growth polymerization of P3ATs. By varying the ratio of the initial monomer concentration to the initiator concentration, no linear dependence of the molar mass was observed, revealing that the polymerization does not proceed via a controlled mechanism. This was also confirmed by analyzing the end‐groups of the polymer with MALDI‐TOF mass spectrometry. To acquire more information on the polymerization mechanism, the formation of the actual monomer and the polymerization reaction were studied into more detail. These experiments proved that the polymerization proceeds via a chain‐growth mechanism, although not in a controlled way.
A new fluorescing, water‐soluble derivative of poly(p‐phenylene vinylene), poly[2,5‐bis(oligooxyethylene)‐1,4‐phenylene vinylene], P(OE‐PV), is synthesized via a multistep route. The UV‐vis absorption and photoluminescence properties of the polymer are studied in aqueous solutions in the presence of 25 different metal ions. Among the ions studied, Fe(III), Os(III) and Ru(III) are found to effectively quench the fluorescence of P(OE‐PV). The Ru(III) is the most efficient in the fluorescence quenching. This observation implies that the polymer is a sensitive and selective chemosensor for these ions. It is suggested that the photoinduced electron transfer from the excited state of P(OE‐PV) to the metal ions may be the quenching mechanism application to the present systems.
Tunable alkaline anion‐exchange membranes based on QPMBV are synthesized using a bottom‐up approach, miniemulsion copolymerization, which can incorporate functional groups into the copolymers with designated composition and high molecular weight. The mechanical and electrochemical properties of the obtained QPMBV membranes are tuned by varying the composition. It is found that the ion exchange capacity of the copolymer, the hydrophilicity of the copolymer chains, the molecular weight, and the glass transition temperature of the copolymers are essential to balance the mechanical and OH– transport properties of QPMBV membranes. QPMBV membrane fuel cells show the best power output and the long‐lasting fuel cell performance among the APE membranes in open literature.
A straightforward synthesis of a conjugated rod/spacer/rod‐type block copolymer containing PCz electron‐donor and PDI electron‐acceptor blocks is described. Two chromophores are covalently connected through sebacate units as saturated spacer. The resulting donor/spacer/acceptor‐type block copolymer (PCz‐S‐PDI) can be applied to limit charge recombination between donor/acceptor interfaces and to control the scale length of nanostructure formation. PCz‐S‐PDI was used to produce a solar cell with the power conversion efficiency of 0.004%.
Oriented films of miscible polymer blends of poly(vinylidene fluoride) and poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] were prepared using a flow‐orientation technique. The lamellar structure and crystal orientation depended upon composition and flow temperature (Tflow). An interlamellar exclusion structure was induced in the blend flow‐oriented below 150 °C, whereas an interlamellar inclusion structure was developed above 150 °C. The crystal orientation of PHBHV was affected by the lamellar structures because the PHBHV chains crystallized in the pre‐existing crystalline morphology of PVDF. Crystallization of PHBHV was markedly restricted at lower PHBHV contents.
Functional polyolefins are prepared from poly‐CPE via ROMP by the action of a designed Ru‐alkylidene initiator followed by quantitative hydroboration with 9‐borabicyclo[3.3.1]nonane. The borylated polymers prepared in this way are then converted into hydroxy‐, amino‐, and silyloxy‐functionalized polyolefins. With increasing polarity of the substituents, the glass‐transition temperatures of the modified polymers increase significantly. Perhydrobrominated poly‐CPE is prepared from poly‐CPE and HBr and subjected to Cu(I)‐mediated ATRP‐based grafting to yield poly(tert‐butyl acrylate)‐grafted polyethylene (PE). The synthetic routes reported here present a straightforward access to functional and polar olefins.
A series of coumarins were reacted with methacrylate or styrene derivatives to form new olefinic coumarin monomers that were polymerized using 2,2′‐azoisobutyronitrile (AIBN). These polymers were highly insoluble in organic solvents and displayed good thermal stability with glass‐transition temperatures between 70 °C and 130 °C. Luminescence studies on some of the coumarin‐containing polymers (CCPs) showed some fluorescence (ΦF around 0.1). Some of the newly‐prepared coumarins and benzocoumarins were reacted with azo dyes to form mixed coumarin‐azo dye complexes. These mixed complexes were further reacted to prepare acrylic monomers and polymerized using AIBN. These polymers were thermally stable and poorly soluble in organic solvents.
A novel ‐type triamine was synthesized for the first time and employed to prepare a series of amine‐ and anhydride‐terminated triphenylpyridine‐containing hyperbranched polyimides under microwave irradiation. The structure of the triamine monomer and polymers were verified by FTIR and 1H NMR spectroscopy. The predominantly amorphous polyimides were soluble in m‐cresol, NMP, DMSO, DMAc and DMF at room temperature or upon heating. The polymers showed glass transition temperatures above 310 °C and a 5 and 10% weight‐loss temperature above 482 and 559 °C. Tensile strength and modulus were higher than 53.1 MPa and 1.01 GPa, respectively. AM‐HBPI‐2 and AD‐HBPI‐2 showed UV‐Vis absorptions in the region 200–400 and 200–350 nm and displayed strong purple and blue fluorescence.
A novel approach to amphiphilic polymeric Janus micelles based on the protonation/deprotonation process of poly(2‐vinylpyridine)‐block‐poly(ethylene oxide) (P2VP‐b‐PEO) diblock copolymers in THF is presented. It is found that addition of HCl to the micelles solution of P2VP‐b‐PEO copolymers leads to the formation of vesicles. Subsequently mixing a small amount of hydrazine monohydrate with the vesicle solution can induce the dissociation and reorganization of the vesicles into Janus micelles. When HCl is replaced by HAuCl4 precursors, composite Janus particles containing gold in P2VP blocks are obtained.
The influence of magnesium acetate on the non‐solvent‐induced phase separation (NIPS) process of amphiphilic polystyrene‐block‐poly(4‐vinylpyridine)s to gain integral‐asymmetric membranes is investigated. Highly uniform pores over the large areas of the membrane can be achieved, and the average pore diameter is adjusted by varying the total molar mass of the block copolymers used. These stimuli‐responsive membranes, which are solution cast in the absence or the presence of small amounts of magnesium acetate, are directly compared, showing a remarkable effect on the pore structures and their openness. Minor salt addition is considered to influence the polarity of the solvents used in a positive manner such that the NIPS process can be improved significantly.
Maleimido‐terminated PCL (M‐PCL) and alkyne‐terminated PCL (A‐PCL) are prepared by the ring‐opening polymerization of ε‐caprolactone with N‐hydroxyethyl maleimide and 4‐pentyn‐1‐ol as initiators catalyzed by tin(II ) trifluoromethane sulfonate at 25 °C, respectively. A series of saccharide‐terminated PCLs have also been synthesized under mild conditions by two chemical strategies: 1). Michael addition of M‐PCL and amino‐containing maltose, and 2). a ‘click’ reaction of A‐PCL and azide‐containing saccharide. The amphiphilic nature of these maltose‐terminated PCLs make self‐assembly into aggregates in water possible. These aggregates have been characterized by transmission electron microscopy and dynamic light scattering measurements.
