Preparation of a Rapidly Forming Poly(ferrocenylsilane)‐Poly(ethylene glycol)‐based Hydrogel by a Thiol‐Michael Addition Click Reaction

The synthesis of a rapidly forming redox responsive poly(ferrocenylsilane)‐poly(ethylene glycol) (PFS‐PEG)‐based hydrogel is described, achieved by a thiol‐Michael addition click reaction. PFS bearing acrylate side groups (PFS‐acryl) was synthesized by side group modification of poly(ferrocenyl(3‐iodopropyl)methylsilane) (PFS‐I) and characterized by ¹H NMR, ¹³C NMR, and FT‐IR spectroscopy. The equilibrium swelling ratio, morphology, rheology, and redox responsive properties of the PFS‐PEG‐based hydrogel are reported.

     

Synthesis of Poly(lactide)s with Modified Thermal and Mechanical Properties

The use of poly(lactide)‐based materials is, in part, limited by their physical and mechanical properties. This article reviews the methods that have been employed to enable enhancement of the materials properties through synthetic manipulation of the polymer structure including block copolymer synthesis and modification of the lactide monomer structure, focusing on the application of ring‐opening polymerization. In turn the effect of these structural modifications on the properties of the resultant materials are reported.

     

The Use of a Low‐Molar‐Mass Self‐Assembled Template to Direct the Crystallisation of Poly(ε‐caprolactone)

Summary: We show that small quantities of dibenzylidene sorbitol dispersed in poly(ε‐caprolactone) provide a self‐assembling nanoscale framework to yield high levels of crystal orientation. During modest shear flow of the melt, the additive forms highly extended nanoparticles which adopt a preferred alignment with respect to the flow field and, on cooling, polymer crystallisation is directed by these particles. We speculate that atomistic level epitaxy is unlikely to be the only directing influence.

SAXS pattern of PCL/DBS in the melt at 80 °C and subjected to a shear flow of 10 s⁻¹ for 1 000 shear units. The flow direction is vertical.     

Growing Nanoballoons and Nanotubes of Pure Polymer from a Microcapsule

Abundant nanoballoons and nanotubes (less than 100 nm) of pure polymer have been grown from a hybrid microcapsule by programed heating. The hybrid microcapsule, comprising an organosilica shell and styrene core, was synthesized by a sol–gel reaction. Electronic microscopy confirmed that most of the growing nanostructures were nanoballoons of less than 100 nm with a thickness of 15 nm, while a few nanostructures were nanotubes with outer diameters around 20 nm. Infrared spectroscopy and thermogravimetric measurements were employed to analyze the composition of the hybrid spheres both qualitatively and quantitively. Based on the pore distribution on the microcapsule surface, the formation mechanism of these nanostructures was proposed in a schematic way. These interesting results encouraged us to develop a microdevice ‘nano‐extruder’ from existing porous templates.

     

Preparation of Hybrid Microgels Functionalized by Silver Nanoparticles

Summary: Hybrid microgels functionalized with silver nanoparticles (AgNP) have been prepared and their physico‐chemical properties examined. Composite particles have been obtained by formation of AgNP in presence of poly[vinylcaprolactam‐co‐(acetoacetoxyethyl methacrylate)] (VCL/AAEM) microgel particles. It has been demonstrated that hybrid particles with different AgNP amounts can be prepared. Hybrid particles are sensitive to temperature and swelling, and collapse processes are reversible. Incorporation of AgNP leads to shrinkage of microgel template due to the partial immobilization of polymer chains on the microgel surface. As a consequence, gradual loss of temperature sensitivity is observed. Hybrid microgels form highly transparent well‐organized films on solid substrates, providing homogeneous distribution of AgNP in bulk material. Presence of AgNP increases considerably the thermal stability of composite films.

Schematic representation (left) and TEM image (right) of hybrid microgels containing silver nanoparticles (AgNP).     

The Effect of Substrate on the Annealing of Poly(butylene succinate) Single Crystals

The morphological evolution of poly(butylene succinate) (PBS) solution‐grown single crystals during annealing was studied using hot‐stage atomic force microscopy. Their morphology changed with increasing temperature and annealing time. The annealing behavior and melting temperature were found to be affected by the substrate. Morphological changes occurred at a much lower temperature on an amorphous carbon film than that on a mica surface. Moreover, the pattern of morphological evolution of the single crystals on a carbon film was different from that on a mica surface. Since the PBS melt had a larger contact angle on the mica surface, these differences in the melting behavior were ascribed to the different interfacial interactions between the chain‐folded surface of the single crystal and the substrate.

     

Polytellurophenes

Will polytellurophenes bridge the gap between conjugated polymer and inorganic solid‐state semiconductors? Polytellurophenes are a virtually unexplored class of conjugated polymer. In this paper, the synthetic methodologies that have been used to prepare polytellurophenes are chronicled. The properties of the resulting polymers are discussed and their potential for use as electronic materials is evaluated. It is far too early to know if these materials will lead to a useful class of thin‐film semiconductors, however some key challenges associated with their synthesis and implementation are outlined. These challenges will need to be addressed as the conjugated polymer research community begins to utilize this area of the periodic table.

     

Fluorene‐Based Co‐polymer with High Hole Mobility and Device Performance in Bulk Heterojunction Organic Solar Cells

A new donor–acceptor polymer based on 9,9‐dioctylfluorene is synthesized and tested in organic photovoltaic devices. Results show that the polymer exhibits good solubility in a range of organic solvents and has a high hole mobility. When blended with a PC₇₀BM acceptor and fabricated into a bulk heterojunction, photovoltaic devices having a maximum power conversion efficiency (PCE) of 6.2% and a peak external quantum efficiency of 74% are created. Such efficiencies are realized without any necessity for solvent additives or thermal annealing protocols.

     

Multicomponent Phase Change Microfibers Prepared by Temperature Control Multifluidic Electrospinning

Multicomponent phase change microfibers, which can storage and release thermal energy in a stepwise manner, are firstly prepared through a facile one‐step multifluidic compound‐jet electrospinning with temperature control. The multiresponsive effect benefits from a special multichannel tubular microstructure that could controllably encapsulate different phase change materials into the channels independently. Aside from the fabrication of multicomponent phase change microfibers, the melt multifluidic compound‐jet electrospinning is promising for applications related to microencapsulation and multifunctional material fields.

     

Uniform Sub‐Micron Polymer Spheres Coated with Ag Nanoparticles

Summary: The synthesis of well‐defined uniform and spherical sub‐micron polymeric spheres, specifically poly[styrene‐co‐(glycidyl methacrylate)] (PSGMA) with a uniform size distribution and surface chemical functionality, is described. It is shown that the surface can be modified with a multi‐amine functional polymer, polyethyleneimine (PEI), most likely through covalent bonding in addition to electrostatic attraction. The PEI acts both as a stabilizing agent and a complexation agent for the deposition of noble metal Ag nanoparticles.

Reaction of PSGMA samples with excess PEI, and its TEM image.     

Self‐Assembly of Poly(2‐alkyl‐2‐oxazoline)s by Crystallization in Ethanol–Water Mixtures Below the Upper Critical Solution Temperature

Crystallization of poly(2‐isobutyl‐2‐oxazoline) and poly(2‐nonyl‐2‐oxazoline) is found to occur by room temperature annealing below the upper critical solution temperature in ethanol–water solvent mixtures. Both polymers produce similar self‐assembled structures (see image), resembling the previously reported crystalline hierarchical structures obtained from hot aqueous poly(2‐isopropyl‐2‐oxazoline) solutions above the lower critical solution temperature. These observations suggest that the crystallization induced self‐assembly process is a rather general phenomenon occurring for semicrystalline polymers in liquid–liquid two phase systems.

     

Tunable Smart Surface of Gold Nanoparticles Achieved by Light‐Controlled Molecular Recognition Effection

Thermosensitive poly(N‐isopropylacrylamide) (PNIPAm)‐coated gold nanoparticles (AuNPs) were prepared by self‐assembly of the azobenzene‐terminated PNIPAm on the surface of the α‐cyclodextrin (α‐CD)‐capped AuNPs via the host–guest molecular recognition between α‐CD and azobenzene. Reversible attachment–detachment of azobenzene‐terminated PNIPAm on the surface of α‐CD‐capped AuNPs was achieved when subjected to visible and UV light irradiation alternately, which endowed thermosensitive AuNPs with tunable smart properties.

     

Heterogeneous ‘Organoclick’ Derivatization of Polysaccharides

Summary: A simple method for the direct catalytic heterogeneous modification of polysaccharides is presented. The novel method is exemplified by the combination of organic acid‐catalyzed esterification and copper‐catalyzed Huisgen reaction (click chemistry) to attach a fluorescent probe to solid cellulose. The heterogeneous ‘organoclick’ derivatization of cellulose allows for a mild, highly modular surface modification of cellulose under environmentally benign reaction conditions.

Schematic of the combined organic acid‐catalyzed esterification and copper‐catalyzed Huisgen reaction (click chemistry) to modify a polysaccharide with a fluorescent probe.     

Electron impact studies. CVII—Negative ion mass spectra of the oxime group. Monoximes derived from α-dicarbonyl systems

Specific losses of water are observed from the molecular anions of monoximes of α-diketones. Labelling studies, kinetic energy release values and the +E spectra of ions have been used to aid in the elucidation of the fragmentation pathways. It is proposed that the majority of ions have α-keto nitrile structures.     

Electrophoresis of Bottle‐Brush Polyelectrolytes in an Attractive Nanochannel

A molecular dynamics study of the electrophoresis of bottle‐brush polyelectrolytes (BPEs) through nanochannels is reported. The BPE molecules consist of a neutral backbone with charged side chains. For strong attractive interactions between the BPE and the wall, the BPE is being trapped on the channel surface. A stretching–shrinking migration of the BPE in a channel of radius 6σ is observed at relatively strong electric fields. The stretching–shrinking transition is periodic for intermediate electric fields but not for stronger electric fields. The BPE also shows a transverse migration toward the wall at weak electric fields, while toward the center with further enhancing the electric field. For a channel with larger radius 12σ, the BPE does not migrate in the stretching–shrinking manner.

     

Functional Microgels Tailored by Droplet‐Based Microfluidics

Monodisperse polymer gel particles with micrometer‐scale dimensions serve for a variety of applications, including those as microcapsules for actives or as micrometer‐sized matrixes for mesoscopic additives. These particles can be produced with exquisite control through the use of droplet‐based microfluidic templating followed by subsequent droplet solidification. This can be achieved by two ways: One way is to use pre‐microgel solutions of low molecular weight monomers and to form microgels by polymerizing these monomers. Another way is to use pre‐polymerized, high molecular weight precursors and to gel them by polymer‐analogous crosslinking. Both approaches have their specific advantages, allowing microgels to be tailored and optimized for specific needs such as those as delivery systems or scaffolds for living cells. This article highlights some recent achievements in the development and use of these microfluidic techniques to fabricate functional microgel particles.