In this work, secondary reactions involved in the free radical polymerization of butyl acrylate are investigated using quantum chemistry. First, various backbiting reactions are studied by adopting a simplified molecular model suitable for treating long polymer chains. The predicted reaction kinetics suggest the possibility of a radical migration along the poly(butyl acrylate) (PBA) chain as a consequence of subsequent j:j + 4 hydrogen abstractions, which are characterized by a low activation energy. Moreover, branching propagation and β‐scission reactions originating from mid‐chain radicals are investigated using a complete PBA model composed of five monomer units. The reaction kinetics involving short‐branch radicals are also examined, and a novel backbiting step leading to the formation of short branches is proposed.
This paper highlights the powerful combination of reversible addition–fragmentation chain transfer (RAFT) radical polymerization and various click/coupling chemistries. This is not an exhaustive review but rather an overview demonstrating the impressive possibilities that the “marriage” of these two synthetic approaches offers in modern macromolecular design and synthesis.
One‐dimensional methyl orange fibrils can be easily prepared. They are stable in acidic aqueous solutions and soluble in neutral water. When used to synthesize conducting polymer microtubules, the fibrils act as “hard templates” formally but as “soft templates” effectively. Microtubular structures of polypyrrole, polyaniline, and poly(3,4‐ethylenedioxythiophene) have been achieved successfully via such water‐soluble versatile templates.
Twin polymerization is a novel technique for synthesizing hybrid polymers with domain sizes in the nanometer range. While a broad variety of monomers have been investigated, the mechanistic details and the most important influences on the nanostructure formation are unknown. A scale bridging approach is presented to simulate the twin polymerization of 2,2'‐spirobi[4H‐1,3,2‐benzodioxasiline]. This approach is based on detailed quantum chemical calculations that yield insight into reactivity and structure at the molecular level while the kinetics of the network formation process and the influences that govern structure formation are investigated at the mesoscopic level by a coarse‐grained simulation.
The synthesis of water soluble star‐block copolypeptides and their encapsulation properties are described. The star‐block copolypeptides, obtained by ring‐opening polymerization of amino acid N‐carboxyanhydrides, consist of a PEI core, a hydrophobic polyphenylalanine or polyleucine inner shell, and a negatively charged polyglutamate outer shell. The encapsulation study showed that these water soluble, amphiphilic star‐block copolypeptides could simultaneously encapsulate versatile compounds ranging from hydrophobic to anionic and cationic hydrophilic guest molecules.
A reverse‐barrier technique is used to enable the treatment of electrospun poly(vinylidene fluoride) nanofibrous membranes with supercritical carbon dioxide. The treatment induces the formation of nanopores and extended‐chain β crystallites of small lateral dimensions in the nanofibers. It also creates interfiber junctions, resulting in a remarkable improvement in mechanical properties of the membranes. The treated membranes are able to retain their shape very well after loading with an ionic liquid (IL). The ionic conductivity of the IL‐loaded membrane is very close to that of the neat IL.
A unique example of macromolecular self‐assembly, where a mono‐component homopolyimide bearing carboxy end‐groups spontaneously forms nanopartilces with novel dimple‐like morphology in a single good solvent, is presented. The self‐assembly process is dramatically affected by the solution concentration and the temperature. It is proposed that such an unexpected self‐assembly behavior is a synergistic result of the self‐complementary hydrogen bonding between carboxy end‐groups and the propensity to parallel packing of polyimide chains through aromatic interactions.
We report the formation of poly(propylene) spherical and ellipsoidal particles templated by carbon nanotubes via solution crystallization. With an increase in nanotube loading, the particle shape changes from sphere to ellipsoid. In the intermediate concentration range, both spherical and ellipsoidal shapes coexist. The particle size decreases with an increase in nanotube loading.
Preparation and Stability of Aroxy-fluoro-silanes. Different possibilities for preparation of aroxy-fluoro-silanes (esp. substituted phenoxy-fluoro-silanes) are investigated. The reaction was proved as the best method of preparation. The aroxy-fluoro-silanes are disposed to dismutation reactions. 相似文献
Summary: Magnetic nanoparticles have been prepared by a co‐precipitation method and modified with methacryloxypropyltrimethoxysilane. Magnetic molecularly imprinted polymer particles have been prepared by suspension polymerization in silicone oil. The particles possess a high affinity to the template molecules and are rapidly separated under a magnetic field.
This communication reports a strategy for scale‐up of an in situ polymerization technique for polyolefin‐based nanocomposites preparation, taking layered silicate (clay) and multi‐walled carbon nanotubes (MWCNTs) as examples of nanofillers. The strategy is realized by transforming the nanofillers into granular “nanosupports” for Ziegler‐Natta catalysts. With a catalyst to polymer replication effect on particle morphology, the in situ prepared nanocomposites are of controlled granular particle morphology. With the polymer particle morphology controlled, the in situ polymerization technique becomes suitable for industrial olefin polymerization processes for mass production of polyolefin nanocomposites.
Organic polymers that contain ligated metals offer a variety of unique properties which include luminescence, electro‐ and photochemistry, catalysis, charge, magnetism, and thermochromism. These organic–inorganic hybrid materials have the potential to offer novel active matrixes for advanced devices. Continued progress in synthetic chemistry and molecular characterization will enable such advanced materials. Here the focus is restricted to side‐chain metal complexes with emissive properties that highlight the use of lanthanide ions as opposed to the often‐studied transition metal complexes.
Poly(dimethylsiloxane) copolymers were synthesized directly from AA/BB monomers employing a CuAAC reaction (click chemistry) in a polyaddition approach. Using organic dialkynes and oligo(siloxane)s end‐functionalized with azide moieties it was possible to obtain siloxane‐based copolymers with TPE properties by click chemistry for the first time. As seen from DSC experiments, properties were strongly dependent on the incorporated organic comonomer.
Summary: The evolution of the photoinduced birefringence in thin films of narrow polymer fractions is studied and compared with the behavior of the non‐fractionated polymer. The Δnind value decreases by increasing the degree of polymerization ( ) within the oligomeric range but becomes independent of molecular weight starting from a of ≈70. Thermal pretreatment of the films results in higher photoinduced birefringence. The films show good stability of the photorecording.
Birefringence induced after 10 min, Δnind(600) and its growth rate at the same moment versus molecular weight. 相似文献
