Synthesis of Silver Nanoparticles Using a Novel Graft Copolymer and Enhanced Particle Stability via a “Polymer Brush Effect”

Polymer‐encapsulated silver nanoparticles were synthesized and sterically stabilized by a new core‐shell type system consisting of poly(S‐alt‐MA)‐graft‐PMMA copolymer that acts as a scaffold for the synthesis of size confined nanoparticles. The graft copolymer is synthesized via ambient temperature ATRP using the CuBr/PMDETA catalytic system at ambient temperature. The graft copolymer is hypothesized to function as a scaffold with the anhydride part interacting strongly with the silver ions, while the PMMA graft functions as a polymer brush that stabilizes the dispersion and prevents the particle aggregation due to a ‘polymer brush effect’. UV absorption and TEM studies confirm that the synthesized silver composite particles have a core‐shell structure.

     

Alternating Poly(Pt‐salphen)‐(p‐phenyleneethynylene) as Phosphorescent Conjugated Linear‐Rod and Coilable Sensory Materials

Phosphorescent conjugated polymers consisting of alternating p‐phenylene‐ethynylene and ‘para‐’ or ‘meta‐type’ Pt(II)‐salphen luminophore units have been synthesized. Side‐arms bearing different substituents (n‐alkoxy and acetylated‐sugar) have afforded contrasting emission properties that are attributed to the polymer conformation, extent of π‐stacking interactions and differences in chemical structure. Intriguing selectivity in luminescent sensing of metal ions has been observed.

     

Self‐Assembled Monolayer Formed by a Rhenium Complex Containing Hyperbranched Polymer

Summary: The synthesis of a hyperbranched polymer containing a rhenium bipyridine complex is reported. The polymer was synthesized from a monomer that contains two chlorotricarbonyl rhenium(I ) bipyridine moieties and a stilbazole ligand, and the polymer was formed by the coordination reaction in one single step. Gel permeation chromatography results showed that the resulting polymer had a strong interaction with the column packing material, which was reduced when the eluent was added with an electrolyte. Both atomic force microscopy and laser light scattering showed that the size of the polymer molecules was in the range between 25–30 nm. A monolayer of polymer molecules could form on a pretreated substrate by the self‐assembly process, which can serve as the building block for multilayer ultrathin film devices.

The metal‐containing hyperbranched polymer synthesized here.     

Spinodal Decomposition in Ternary Systems with Significantly Different Component Diffusivities

A numerical method for simulating spinodal decomposition in ternary systems with order‐of‐magnitude differences in diffusion coefficients is presented. The method has been partially verified by molecular dynamic simulations and gives results equivalent to the standard technique when the diffusivities are equal. A two‐dimensional simulation of an asymmetric polymer/polymer/polymer system reproduces an experimentally observed bimodal distribution of dispersed‐phase particle sizes. The ripening exponent for the larger particles is near the expected value of 0.33, but that for the smaller particles is only about 0.1. The method was also used for a polymer/polymer/solvent system.

     

Exploring Actuation and Mechanotransduction Properties of Polymer Brushes

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.

     

RIS Model of the Helix‐Kink Conformation of Erythro Diisotactic Polynobornene

Computer simulations reveal the unique conformation of or erythro diisotactic polynorbornene, a polymer with numerous important applications in microelectronics. While previous simulations suggested that this polymer adopts a helix‐kink morphology, the results presented herein indicate that the reversal of the helix symmetry is the origin of such kinks which cause a transition from a rigid‐rod conformation to a random coil with increasing molecular weight. An RIS model was developed that accurately predicts the unique conformation of this polymer. This model predicts a rigid‐rod helical conformation that eventually transitions to a random coil at a degree of polymerization of approximately 500.

     

Novel Electrochromic Displays Using Monodisperse Viologen‐Modified Porous Polymeric Microspheres

Summary: In order to achieve a reasonable response time in an electrochromic display, viologen‐modified porous polymeric microspheres of various porosities have been used as substrates. Porous microspheres are prepared using seeded polymerization in the presence of a porogen. Based on ionic conductivity and the chronocoulometry measurements, it is confirmed that the electrolyte content increases, and the resistance of the polymer particles in the device decreases as the specific surface area of the porous particles increases. This results in a rapid response time of 270 ms.

Schematic representation of the viologen‐modified porous polymeric microspheres in the manufactured ECD device (A). Images of the device (B) in the OFF state (left) and in the ON state (right).     

Thiol‐alkyne Chemistry for the Preparation of Micelles with Glycopolymer Corona: Dendritic Surfaces versus Linear Glycopolymer in Their Ability to Bind to Lectins

A poly(tert‐butyl acrylate) (P(tBA)) with a glycodendric endfunctionality with eight glucose moieties was synthesised in four steps via a combination of esterification, thiol‐alkyne conjugation and hetero‐Diels–Alder (HDA) cycloaddition. A linear glycopolymer of similar size and composition was also synthesised in order to compare the protein binding characteristics of the polymer with glycodendritic endfunctionality to the linear glycol blockcopolymer. The two amphiphilic polymers were self‐assembled in water into micelles. These particles were then tested for their ability to bind to Concanavalin A (Con A). In a turbidity assay, the polymer glycodendron exhibited a significantly faster clustering rate to the lectin as compared to the linear glycopolymer. In a precipitation assay, it is found that significantly less glucose residue is required for binding per Con A for the polymer with the glycodendritic endfunctionality.

     

Polymerization of Aniline by Auric Acid: Formation of Gold Decorated Polyaniline Nanoballs

Summary: We report a new method for the preparation of polyaniline nanoballs by using HAuCl₄ as an oxidizing agent. During the reaction, aniline is oxidized and forms polyaniline whilst the hydrogen tetrachloroaurate is reduced and forms gold nanoparticles. These gold nanoparticles are found to decorate the nanoballs.

The resultant precipitate and corresponding TEM image of the gold‐nanoparticle covered polyaniline nanoball.     

All‐in‐one Layer: Anisotropic Emission due to Light‐Induced Orientation of a Multifunctional Polymer

An efficient procedure to create oriented polymer films with strongly anisotropic properties is described. It is based on a two‐step process combining a photochemical and a thermal aligning step. The orientation of the polymer parallel or perpendicular to linearly polarised incident light can be adjusted. The method presented allows for simple fabrication of films with anisotropic absorption and emission characteristics with a dichroism of 0.7 and a fluorescence anisotropy of about 8.

     

Novel Two‐Compartment Micelles Formed by Self‐Assembly of Linear Pentablock Copolymers in Selective Solvents

In this work, the formation of two‐compartment micelles from symmetric pentablock copolymers in selective solvents was studied using the dissipative particle dynamics simulation technique, and the effects of block lengths and solvent quality were investigated. The simulations revealed several new morphologies and their formation mechanisms were elucidated at the molecular level, providing useful information that may contribute to the future rational design and synthesis of novel multicompartment micelles with tailored structures.

     

Photomechanical Switching Behavior of Semi‐Interpenetrating Polymer Network Consisting of Azobenzene‐Carrying Crosslinked Poly(vinyl ether) and Polycarbonate

Summary: A novel semi‐interpenetrating polymer network (semi‐IPN) with photomechanical switching ability was developed by a cationic copolymerization of azobenzene‐containing vinyl ethers in a matrix of a linear polycarbonate (PC). The semi‐IPN film showed reversible deformation upon switching the UV irradiation on and off and responded with unprecedented rapidity. The photomechanical effect is attributed to a reversible change between the highly aggregated and dissociated states of the azobenzene groups.

The reversible UV response of the length of the semi‐IPN film at 25 °C.     

High Temperature Free Radical Copolymerization with Depropagation and Penultimate Kinetic Effects

Summary: Methacrylate copolymers produced under higher temperature starved‐feed conditions are affected by depropagation, and some binary systems also experience a penultimate effect. In this work a generalized set of equations has been developed to describe the combined effect of depropagation and penultimate copolymerization kinetics on instantaneous copolymer composition and average copolymerization rate coefficients. Limiting cases applicable to the methacrylate/styrene system are examined. When combined with depropagation, penultimate kinetics not only decrease the effective propagation rate coefficient but also deviate from terminal model predictions of polymer composition.

Copolymerization chain growth with penultimate kinetics and depropagation.     

Enzymatic Polymerization towards Biodegradable Polyester Nanoparticles

The direct enzymatic polymerization of miniemulsions consisting of lactone nanodroplets represents a new and convenient pathway for the synthesis of biodegradable polymer nanoparticles, where the chemical composition and molecular weight can be varied in a certain range. Oligoesters completely end‐capped with an alkene or diene group can also be prepared by this technique. These building blocks extend polyester application as they allow to impart improved biodegradability to both siloxane and resin chemistry.

TEM image of the polyester particles obtained by enzymatic polymerization in miniemulsion.