In general, when a crystal is molten, all molecules forget about their mutual correlations and long-range order is lost. Thus, a regrown crystal does not inherit any features from an initially present crystal. Such is true for materials exhibiting a well-defined melting point. However, polymer crystallites have a wide range of melting temperatures, enabling paradoxical phenomena such as the coexistence of melting and crystallization. Here, we report a self-seeding technique that enables the generation of arrays of orientation-correlated polymer crystals of uniform size and shape ('clones') with their orientation inherited from an initial single crystal. Moreover, the number density and locations of these cloned crystals can to some extent be predetermined through the thermal history of the starting crystal. We attribute this unique behaviour of polymers to the coexistence of variable fold lengths in metastable crystalline lamellae, typical for ordering of complex chain-like molecules.
A new strategy to achieve easily
scalable triple stimuli-responsive
elastomeric opal films for applications as stretch-tunable photonic
band gap materials is reported. Novel monodisperse highly functional
core-interlayer-shell beads are obtained by semicontinuous emulsion
polymerization featuring a temperature-sensitive fluorescent rhodamine
dye either locally restricted in the core or the shell of prepared
beads. After extrusion and compression molding, homogeneous elastomeric
opal films with fascinating stretch-tunable and temperature-dependent
fluorescent properties can be obtained. Applying strains of only a
few percent lead to significant blue shift of the reflected colors
making these films excellent candidates for applications as deformation
sensors. Higher strains up to 90% lead to a tremendous Bragg reflection
color change caused by transition from the (111) to the (200) lattice
plane. The well-ordered opaline structure with its stop band at the
emission frequency of the incorporated fluorescent dye shows remarkable
angle-dependent fluorescence suppression. Herein described elastomeric
opal films can be valuable in a wide range of applications such as
rewritable 3D optical data storage, tunable laser action, and sensing
This review draws a rather comprehensive picture of how Suzuki polycondensation was discovered in 1989 and how it was subsequently developed into the most powerful polymerization method for polyarylenes during the last 20 years. It combines insights into synthetic issues with classes of polymers prepared and touches upon aspects of this method's technological importance. Because a significant part of the developmental work was carried out in industry, the present review makes reference to an unusually large number of patents.
The study of metallopolymers has blossomed into a mature field over the last few decades. Especially, polyferrocenylsilane (PFS) chemistry has taken a tremendous leap and continues to raise intense interest. Since the discovery of thermal ring-opening polymerization (ROP) of silaferrocenophanes, PFSs have been also accessed by anionic, cationic, transition-metal-catalyzed, and photolytic anionic ROP methodologies. A plethora of synthetic strategies have been devised, enabling access to a wide variety of copolymers, polyelectrolytes, and nanostructured materials. The distinctive physical properties and functions of many PFS-based polymers have been explored, leading to their apt exploitation in technical applications. Therefore, it is conceivable that PFS-related platforms might be indispensable nano-objects in the near future, as they stand on the verge of a new generation of sophisticated materials.
Nanocapsules composed of a poly(vinylferrocene)-block-poly(methyl methacrylate) shell and a hydrophobic liquid core are prepared in water. The nanocapsule shells display a patchy structure with poly(vinylferrocene) patches with sizes of 25 ± 3 nm surrounded by poly(methyl methacrylate). The functional nanopatches can be selectively oxidized, thereby influencing the colloidal morphology and introducing polar domains in the nanocapsule shell. The hydrophobic to hydrophilic transition in the redox-responsive nanopatches can be advantageously used to release a hydrophobic payload encapsulated in the core by an oxidation reaction.
Rodlike ruthenium(II) coordination polymers have been prepared via the conversion of 4,4′′bis(2,2′:6′,2′′-terpyridine)-2′,5′-dihexyl-p-terphenyl and an appropriately reactive ruthenium(III) species in 1-butanol/DMA. The diamagnetic polymers readily dissolve in polar organic solvents, and their homogeneous constitution could thus be proven and their degrees of polycondensation could be estimated to be Pn g 30, using 1 H and 13 C NMR spectroscopy. The Pd-catalyzed polycondensation of bis[4′-(pbromophenyl)-2,2′:6′,2′′-terpyridine]ruthenium(II) tetrafluoroborate and 2,5-dihexylbenzene-1,4-diboronic acid, on the other hand, which should lead to a constitutionally identical polymer, only resulted in oligomers under all tested conditions. The intrinsic viscosity [η] of the high-molecular-weight polymers (determined in 0.02 M NH4PF6/DMA) is of the order of 300 mL g -1 . In salt-free DMA solution and thus at low ionic strengths, the polymers display the characteristic polyelectrolyte behavior in viscosity experiments which becomes more and more pronounced with increasing Pn. The UV-vis absorption spectra recorded in DMA solution do not show any evidence of intramolecular electronic interactions of the metal centers along the polymer chains: on the contrary, the coordination polymers behave like sequences of electronically independent ruthenium(II) complexes.
Well-defined poly(2-(methacryloyloxy)ethyl ferrocenecarboxylate)
(PFcMA) brushes were synthesized by surface-initiated atom transfer
radical polymerization (SI-ATRP) on cross-linked polystyrene particles.
The ATRP of FcMA monomer was reinvestigated leading to molar masses
up to 130 kg mol–1 with a good reaction control
and high monomer conversion (91%). The SI-ATRP was done with different
amounts of initiator in the PS particle shell leading to PFcMA surface
conformations from “mushroom-like” to dense “brush-like”
polymers, which could be confirmed by dynamic light scattering (DLS)
experiments. Redox-responsive behavior of the PFcMA shell was investigated
by DLS and cyclic voltammetry (CV) measurements indicating a tremendous
increase in the hydrodynamic volume of the ferrocene-containing shell.
The transformation of PFcMA-grafted PS particles to magnetic iron
oxides after thermal treatment could be investigated by SQUID magnetization
measurements showing the typical hysteresis for ferromagnetic material.
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