We report here a facile synthesis of high performance electro‐active polymer actuator based on a sulfonated polyimide with well‐defined silver electrodes via self‐metallization. The proposed method greatly reduces fabrication time and cost, and obviates a cation exchange process required in the fabrication of ionic polymer‐metal composite actuators. Also, the self‐metallized silver electrodes exhibit outstanding metal‐polymer adhesion with high conductivity, resulting in substantially larger tip displacements compared with Nafion‐based actuators.
Novel side‐chain‐type sulfonated poly(arylene ether) with pendant sulfoalkyl group copolymers (PSA‐SPAE‐6F) have been synthesized by direct copolymerization from a new sulfonated monomer, sodium 3‐(4‐(2,6‐difluorobenzoyl)phenyl)propane‐1‐sulfonate. The sulfonate content could be easily controlled by adjusting the sulfonated and the unsulfonated monomer feed ratio. The obtained copolymers all show good thermal and mechanical properties. It should be noted that the most highly sulfonated copolymer, PSA‐SPAE‐6F90 with an ion exchange capacity of 1.30 mequiv · g−1, shows a proton conductivity of 0.11 S · cm−1 and a water swelling ratio of only 12.9% at 100 °C, which indicates its high proton conductivity and excellent dimensional stability in hot water.
Versatile synthetic methods towards a variety of thiophene‐nucleobase hybrid systems are reported. Adenine‐ and thymine‐based modified nucleosides characterized by a bithiophene unit linked to the C5′ or C8 position through an ethylenamino or an ethylensulfanyl bridge were synthesized and successfully polymerized in the presence of FeCl3. The self‐organization properties of the pure polymers as well as their mixtures ‐ with complementary nucleobases ‐ were investigated by means of optical microscopy and AFM in cast film showing complex supramolecular structures resulting from the interplay of multiple intermolecular interactions.
Soft nanotechnology requires new approaches and materials to efficiently convert chemical energy into mechanical motion and vice versa. A number of key design parameters, such as responsiveness to external stimuli, directionality of response through alignment, transduction via surface stresses or changes in ionic conductivity can be found in polymer brushes and several recent examples of actuation and transduction in polymer brushes will be explored.
Layer‐by‐layer (LbL) assembly was conducted on CaCO3 microparticles pre‐doped with polystyrene‐block‐poly(acrylic acid) (PS‐b‐PAA) micelles, and resulted in micelles encapsulation in the microcapsules after core removal. Distribution of the micelles in the templates and capsules was characterized by transmission electron microscopy and confocal laser scanning microscopy. The micelles inside the capsules connected with each other to form a chain and network‐like structure with a higher density near the capsule walls. The hydrophobic PS cores were then able to load small uncharged hydrophobic drugs while the negatively charged PAA corona could induce spontaneous deposition of water‐soluble positively charged drugs such as doxorubicin.
The importance of taking into account the principle of microscopic reversibility in the analysis of complex copolymerization systems is demonstrated. The analysis of a reversible copolymerization system in which segmental exchange is possible from the point of view of the reaction microreversibility proves that hetero‐reshuffling rate constants depend on homo‐reshuffling rate constants and copolymerization thermodynamics.
A novel top‐surface imaging process was successfully established using selective chemisorption of amine‐functionalized poly(dimethyl siloxane) onto the carboxylic groups formed on the surface of diazoketo‐functionalized polymer film by UV light irradiation. The chemisorbed poly(dimethyl siloxane) worked as an efficient etch mask for the subsequent oxygen plasma etching process for pattern generation. High‐resolution patterns were resolved with the new imaging process.
A two‐armed polymer with a crown ether core self‐assembles to produce macroporous films with pores perpendicularly reaching through the film down to the substrate. A possible assembling mechanism is discussed. The pore size can be conveniently adjusted by changing the solution concentration. These through‐hole macroporous films provide a template for fabricating an array of Cu nanoparticle aggregates.
High‐solid‐content low‐viscosity bimodal latexes with very small particles (<200 nm) are obtained using two emulsion polymerization approaches. In the first approach, the PSD is controlled by using highly crosslinked nanolatex particles (<30 nm) as seeds for the small mode to minimize their growth during the growth of the large mode. These particles are shown to grow at a volumetric rate that is 25 times lower than the larger particles. Latexes with 57 wt% solids content and viscosities <1400 mPa · s at 20 s?1 are produced. The second approach is based on the re‐nucleation of the small particles by addition of a shot of surfactant in the presence of large particles to produce bimodal latexes. Latexes with 60 wt% solid content with viscosity of 490 mPa · s at 20 s?1 are produced using this approach.
Polycondensation of 1‐(2‐pyrimidinyl)pyrrole with 2,7‐dibromo‐9,9‐dioctylfluorene via Ru‐catalyzed direct arylation gives the corresponding conjugated polymer with a molecular weight of 19 800 in 86% yield. The introduction of directing group, 2‐pyrimidinyl substituent, into the pyrrole monomer induces ortho‐metalation and provides the site‐selective direct arylation polycondensation at the α‐position of pyrrole unit without the protection of β‐position. The removal of 2‐pyrimidinyl substituent on the pyrrole unit proceeds efficiently and results in the enhancement of coplanarity along the main chain of the polymer.
The intracellular delivery of Doxorubicin (Dox) from poly(lactide‐co‐glycolide) (PLGA) nanoparticles stabilised with bovine serum albumin, in HepG2 cells, is studied via flow cytometry, fluorescence lifetime imaging microscopy (FLIM), confocal Raman microscopy (CRM) and cell viability studies. Flow cytometry shows that the initial uptake of PLGA and Dox follow the same kinetics. However, following 8 h of incubation, the fluorescence intensity and cellular uptake of Dox decreases, while in the case of PLGA both parameters remain constant. FLIM shows the presence of a single‐lifetime species, with a lifetime of 1.15 ns when measured inside the cells. Cell viability decreases by approximately 20% when incubated for 24 h with PLGA loaded with Dox, with a particle concentration of 100 µg · mL?1. At the single‐cell level, CRM shows changes in the bands from DNA and proteins in the cell nucleus when incubated with PLGA loaded with Dox.
Polymer‐dispersed liquid crystals (PDLCs) represent an important new class of materials with electro‐optic applications such as flexible displays, large‐area devices projection displays, electrically switchable windows, etc. On considering such applications of these materials, many studies have been performed on the experimental side. Similarly, research on the simulation side for the PDLCs is of the fundamental interest too. The present article contains a short review on the present and past simulation studies of PDLCs. Various molecular simulation approaches applied to PDLC systems by different groups are reviewed here. In addition some new findings of the bulk phases are also extensively described.
Radical copolymerizations of heterologous comonomers are compositionally heterogeneous, unless the reaction is performed in continuous conditions. A bicomponent network prepared from a heterogeneous reaction like the mentioned before is therefore a complex structure where chains with different compositions are linked through the cross‐linker molecules. It is theoretically shown here that the use of cross‐linkers with different structural homologies toward the two comonomers may lead to very different topologies. Thus, a mixture of symmetric cross‐linkers, each one homologous to each comonomer, tends to form interpenetrated networks (IPNs). However, the use of a single bihomologous asymmetric cross‐linker, where each of the functionalities is homologous toward each of the comonomers, tends to form conetworks. It is shown here that the higher the differential reactivity between the groups, the higher is the tendency toward these extreme structures.
Summary: Fabrication of honeycomb‐patterned films from amphiphilic dendronized block copolymer (PEO113‐b‐PDMA82) by ‘on‐solid surface spreading’ and ‘on‐water spreading’ method is reported. Highly ordered honeycomb films with quasi‐horizontally paralleled double‐layered structure can be fabricated by the on‐solid surface spreading method. This work raises the possibility that such structures can be formed in amphiphilic dendronized block copolymers and extends the family of source materials.
A new concept to build shape memory polymers (SMP) combining outstanding fixity and recovery ratios (both above 99% after only one training cycle) typical of chemically crosslinked SMPs with reprocessability restricted to physically crosslinked SMPs is demonstrated by covalently bonding, through thermoreversible Diels–Alder (DA) adducts, star‐shaped poly(ε‐caprolactones) (PCL) end‐functionalized by furan and maleimide moieties. A PCL network is easily prepared by melt‐blending complementary end‐functional star polymers in retro DA regime, then by curing at lower temperature to favour the DA cycloaddition. Such covalent network can be reprocessed when heated again at the retro DA temperature. The resulting SMP shows still excellent shape memory properties attesting for its good recyclability.
Recently, it has been recognized the shape of particles plays an essential role in the design of materials with unique properties. In this study, PLGA non‐spherical microarchitectures, rods and fibers, were fabricated successfully in high yield by single emulsion‐solvent evaporation method in the presence of sodium tripolyphosphate. The assay of PVA residue was carried out and the hydrogen bonds formation was verified as well. The presented data show that viscosity and coagulation agent have a synergistic effect on forming the rod‐ and fiber‐like microarchitectures in the shear response and the formation mechanisms were proposed accordingly.
