Low‐Temperature Growth of Thick Polystyrene Brushes via ATRP

Summary: This contribution describes the graft polymerization of polystyrene (PS) by atom transfer radical polymerization at 50, 60, and 75 °C. Thick PS brushes were grown from initiator‐functionalized PGMA layers on silicon, and constant growth rates provide indirect evidence that the polymerizations were controlled.

Formation of polystyrene brushes at T < T_g by ATRP of styrene from α‐bromoester initiator‐functionalized poly(glycidyl methacrylate) layers.     

Nanostructured Heteroarm Star Block Terpolymers via an Extension of the “In–Out” Polymerization Route

In this communication an extended “in–out” polymerization method is presented, which leads to the synthesis of novel heteroarm star block terpolymers of the type A_n(B‐b‐C)_n. A four step/one‐pot synthetic procedure is pursued using anionic polymerization under an inert atmosphere. The resulted star‐shaped terpolymer consists of a divinyl benzene nodule bearing pure polystyrene and poly(hexyl methacrylate)‐block‐poly(methyl methacrylate) diblock copolymer arms. It is shown that this kind of star terpolymers can self‐assemble in the bulk forming lamellae mesophase by arm and block segregation. The mechanical properties of the terpolymer have been examined in detail. Finally, the proposed synthetic procedure can be easily employed in other controlled polymerization methods.

     

Co‐Continuous Polymeric Nanostructures via Simple Melt Mixing of PS/PMMA

Blends of polystyrene/poly(methyl methacrylate) (PS/PMMA) (30/70) prepared by simple melt mixing form a droplet (PS) in‐matrix (PMMA) morphology. It is found that addition of a carefully designed copolymer PS‐b‐P(S‐ran‐MMA) (SSM) compatibilizer could convert the morphology into a co‐continuous system. Indeed, the continuity of the dispersed PS phase increased with an increase in PS‐b‐P(S‐ran‐MMA) content, and a fully co‐continuous morphology (continuity = 100%) was obtained at 20% SSM fraction with a characteristic size of 100 nm.

     

Supramolecular Assembly of Gold Nanoparticles Mediated by Polypseudorotaxane with Thiolated β‐Cyclodextrin

Summary: A water‐soluble gold nanoparticle aggregate 2 was prepared by chloroauric acid and a polypseudorotaxane 1 of mono‐6‐thio‐β‐cyclodextrin with poly(propylene glycol) bis(2‐aminopropyl ether) ( ≈ 2 000) in the presence of sodium borohydride in N,N‐dimethylformamide (DMF) solution. The investigative results indicated that the gold nanoparticle aggregate 2 might act as an efficient DNA‐cleavage reagent.

A typical TEM image of gold nanoparticle aggregate 2 .     

Ring and Disk‐Like CdSe Nanoparticles Stabilized with Copolymers

CdSe nanoparticles stabilized with the amphiphilic diblock copolymer polystyrene‐block‐poly(4‐vinylpyridine) were spread from toluene dispersion on the water surface. Monolayers could be transferred onto solid substrates using the Langmuir‐Blodgett technique. By means of atomic force and scanning electron microscopy highly symmetric ring and disk‐like structures with diameters ranging between 150 nm and 1200 nm were observed.

AFM image of a mixed monolayer of copolymer 12 and CdSe nanoparticles stabilized with polystyrene‐block‐poly(4‐vinylpyridine).     

Synthesis of Well‐Defined Polybenzamide‐block‐Polystyrene by Combination of Chain‐Growth Condensation Polymerization and RAFT Polymerization

Well‐defined diblock copolymers composed of poly(N‐octylbenzamide) and polystyrene were synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization of styrene with a polyamide chain transfer agent (CTA) prepared via chain‐growth condensation polymerization. Synthesis of a dithioester‐type macro‐CTA possessing the polyamide segment as an activating group was unsatisfactory due to side reactions and incomplete introduction of the benzyl dithiocarbonyl unit. On the other hand, a dithiobenzoate‐CTA containing poly(N‐octylbenzamide) as a radical leaving group was easily synthesized, and the RAFT polymerization of styrene with this CTA afforded poly(N‐octylbenzamide)‐block‐polystyrene with controlled molecular weight and narrow polydispersity.

     

Synthesis of Block Copolymers Modified with Phosphonate Ester Groups Using Nitroxide‐Mediated Radical Polymerization

Summary: Phosphonate groups were introduced into block copolymers of styrene derivatives either as single end‐groups or as small blocks using nitroxide‐mediated radical polymerization. In order to combine the hydrophobic and hydrophilic segments, block copolymers with N,N‐dimethyl acrylamide were synthesized. After hydrolysis to phosphonic acid groups, adsorption of the polymer onto metal oxides was possible.

Conversion of the phosphonate groups by transesterification with trimethylbromosilane (TMBS), followed by hydrolysis of the silylester group.     

Raspberry‐Like Aggregates Containing Secondary Nanospheres of Polystyrene‐block‐poly(4‐vinylpyridine) Micelles

Summary: Raspberry‐like aggregates containing secondary nanospheres were studied. The formation of raspberry‐like aggregates was due to complexation between core‐shell microspheres and core‐corona micelles. The core‐shell microspheres were synthesized with soap‐free polymerization of styrene and methyl acrylic acid, which included carboxyl groups in the periphery. The micelles were self‐assembled by polystyrene‐block‐poly(4‐vinylpyridine), which contained pyridine groups in the corona. The driven force to form raspberry‐like aggregates was due to the affinity between the carboxyl and pyridine groups. The morphology of the raspberry‐like aggregates could be tuned by changing the ratio of the microspheres to micelles. IR measurements suggested that the raspberry‐like aggregates were like zwitterions.

TEM image of the raspberry‐like aggregates formed at a molar ratio of MAA to 4VP at 1:4.     

Self‐Assembling Nanomaterials using Magnetic Nanoparticles Modified with Polystyrene Brushes

Magnetic nanomaterials have been studied in order to generate novel nanocomposites that display both the magnetic properties of the nanoparticles and the ability to self‐assemble of the amorphous block copolymer matrix. Towards this goal, iron oxide magnetic nanoparticles have been modified with PS brushes by ATRP in order to improve both the dispersion and the affinity of the nanoparticles with one of the blocks of a polystyrene‐block‐polybutadiene‐block‐polystyrene block copolymer. This method of preparation of nanocomposites opens new strategies for the generation of magnetic nanomaterials. The samples are characterized using DSC and atomic and magnetic force microscopies.

     

Penultimate Propagation Kinetics of Butyl Methacrylate,Butyl Acrylate,and Styrene Terpolymerization

The pulsed‐laser polymerization technique is used to determine the composition‐averaged free‐radical propagation rate coefficient (k_p,ter) for terpolymerization of butyl methacrylate, butyl acrylate, and styrene between 60 and 120 °C. A significant deviation from terminal model predictions is observed for the ternary system, indicating that penultimate kinetics are important at these industrially relevant temperatures. The implicit penultimate propagation model, with all the coefficients taken from previous studies of the binary systems, provides a good prediction of the experimental k_p,ter results.

     

α,ω‐Nitroxide‐Capped Polystyrenes and Poly(butyl acrylate)s as Macroinitiators for the Free‐Radical Polymerization of Methyl Methacrylate

The use of a bisaminooxy compound as initiator for nitroxide‐mediated radical polymerization (NMRP) of styrene or n‐butyl acrylate allows the synthesis of α,ω‐nitroxide‐capped polymers. At high temperatures and with the addition of acetic anhydride, it was found that these polymers could be applied as macroinitiators in the free‐radical polymerization of methyl methacrylate. This enables the synthesis of block copolymers with only minor contents of homopolymer.

The structure of bis‐TIPNO, the bisaminooxy compound used as an initiator for the nitroxide‐mediated radical polymerization of styrene or n‐butyl acrylate.     

A Strategy for Synthesis of Ion‐Bonded Supramolecular Star Polymers by Reversible Addition‐Fragmentation Chain Transfer (RAFT) Polymerization

We have developed a novel strategy for the preparation of ion‐bonded supramolecular star polymers by RAFT polymerization. An ion‐bonded star supramolecule with six functional groups was prepared from a triphenylene derivative containing tertiary amino groups and trithiocarbonate carboxylic acid, and used as the RAFT agent in polymerizations of tert‐butyl acrylate (tBA) and styrene (St). Molecular weights and structures of the polymers were characterized by ¹H NMR and GPC. The results show that the polymerization possesses the character of living free‐radical polymerization and the ion‐bonded supramolecular star polymers PSt, PtBA, and PSt‐b‐PtBA, with six well‐defined arms, were successfully synthesized.

     

Synthesis of Branched Polyglucans by the Tandem Action of Potato Phosphorylase and Deinococcus geothermalis Glycogen Branching Enzyme

An enzymatic tandem reaction is described in which the enzymes phosphorylase and Deinococcus geothermalis glycogen branching enzyme (Dg GBE) catalyze the synthesis of branched polyglucans from glucose‐1‐phosphate (G‐1‐P). Phosphorylase consumes G‐1‐P and polymerizes linear amylose while Dg GBE introduces branching points on the α‐(1 → 6) positions by reshuffling short oligosaccharides. The resulting branched polyglucans have an unusually high degree of branching of 11%.

     

Synthesis and Characterization of Helix‐Coil Diblock Copolymers with Controlled Supramolecular Architectures in Aqueous Solution

Summary: A series of helix‐coil diblock copolymers based on poly(ethylene oxide) and optically active helical poly{(+)‐2,5‐bis[4′‐((S)‐2‐methylbutoxy)phenyl]styrene} (PMBPS) were synthesized via atom transfer radical polymerization (ATRP). The synthetic methodology permitted straightforward preparation of the diblock copolymers with relatively low polydispersities and a broad range of compositions and molecular weights. Depending on the composing block length and the initial concentration, the copolymers self‐assembled into different supramolecular structures in aqueous solution, including spherical micelles, vesicles, multilamellar vesicles, large compound vesicles, and tubules.

Schematic representation of the synthesis of PEO‐b‐PMBPS block copolymers and their aggregation in aqueous solution.     

Characterization of Chlorine‐, Amine‐ and Acrylate‐Functionalized TEMPO‐Capped and Bis‐TEMPO‐Capped Polystyrenes Using MALDI‐TOF MS

Chlorine‐functionalized TEMPO‐capped polystyrenes were investigated using the matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) technique. Amine‐ and acrylate‐functionalized agents and bifunctional TEMPO‐capped polystyrene were also analyzed to demonstrate the applicability of this method. Using this technique allowed to analyze the conversion of the chlorine function to an acrylate function, which was previously difficult to detect with other methods.

MALDI‐TOF mass spectrum of a polystyrene described in this article, as obtained with DHB as the matrix.     

Atom Transfer Radical Polymerization of Styrene and Methyl Methacrylate from Mesoporous Ordered Silica Particles

Summary: Mesoporous silica was used as substrate for the grafting of alkyl halides initiators. The control over the surface‐initiated polymerization of styrene and MMA, in terms of molar mass and molar mass distribution, was successfully achieved using an ATRP mechanism. The occurrence of the polymerization inside the mesopores was confirmed by thermogravimetric analysis.

Transmission electron microscopy and schematic representation of mesoporous silica functionalized by the anchored iniator (left) and the grafted polymer (right).     

Cross‐Linked Conjugated Polymers for Achieving Patterned Three‐Color and Blue Polymer Light‐Emitting Diodes with Multi‐Layer Structures

Reactions between the ethylene groups in the backbone of conjugated polymers under UV illumination and heat treatment result in the cross‐linking of the main polymer chains. The cross‐linking leads to two simultaneous results in the polymer: excellent solvent resistance and increased bandgap. Using this reaction, three‐color polymer light‐emitting diodes (PLEDs) with a multi‐layer structure can be easily realized by a dry photo‐pattern in an active‐gas‐free environment. Multi‐layer blue devices with dramatically enhanced efficiency can also be achieved conveniently.

     

Electro‐active Polymer Actuator Based on Sulfonated Polyimide with Highly Conductive Silver Electrodes Via Self‐metallization

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.

     

Importance of the Position of the Chromophore Group on the Dissociation Process of Light Sensitive Alkoxyamines

New photosensitive alkoxyamines have been designed using molecular orbital calculations to improve the selective C O versus N O cleavage. The targeted light‐sensitive alkoxyamine is synthesized in one step and its reactivity under UV has been investigated using both ESR and LFP. The ability of this alkoxyamine to control the photopolymerization of n‐butyl acrylate is evidenced through a process called nitroxide‐mediated photopolymerization NMP². The selected alkoxyamine is finally used to prepare covalently bonded multilayered micropatterns. This original application highlights the high potential of this technique for some specific applications that require spatial control.

     

Defined Poly[styrene‐block‐(ferrocenylmethyl methacrylate)] Diblock Copolymers via Living Anionic Polymerization

Ferrocenylmethyl methacrylate (FMMA) is one of the very few metallocene‐based monomers that are promising candidates for truly living anionic polymerization. Nevertheless, FMMA homopolymers with a narrow polydispersity, or block copolymerization studies that result in satisfying blocking efficiencies, are unknown so far. Here we describe a procedure that leads to highly regular FMMA‐based polymers for the first time, characterized by polydispersity indices (PDI) of less that 1.05 and very high blocking efficiencies (>95%) in sequential copolymerization with styrene. Some of the obtained poly[styrene‐block‐(ferrocenylmethyl methacrylate)]s show unusual microphase morphologies, presumably the consequence of high T_gs causing ‘frustrated’ non‐equilibrium states.