Preparation and SO2 Absorption/Desorption Properties of Crosslinked Poly(1,1,3,3‐Tetramethylguanidine Acrylate) Porous Particles

Summary: Novel crosslinked porous particles based on the ionic copolymer of 1,1,3,3‐tetramethylguanidine acrylate (TMGA) and N,N‐methylenebisacrylamide (MBA) were prepared via an inverse suspension polymerization using cyclohexane as continuous phase and Span 60 as the dispersant. The SO₂ absorption–desorption properties of the P(TMGA‐co‐MBA) particles were studied for the first time. The particles showed excellent SO₂ absorption properties: high capacity and rate. These absorption properties, as well as the particle volume, shape, and morphology, remained unchanged during the SO₂ absorption–desorption cycles. The material appeared to be a good candidate as SO₂ absorbent for fuel gas desulfurization (FGD) and purification of other SO₂‐containing gases.

Optical microscope image of the P(TMGA‐co‐MBA) porous particles.     

Multi‐Morphological Complex Aggregates Formed from Amphiphilic Poly(ethylene oxide)‐block‐Polydimethylsiloxane‐block‐Poly(ethylene oxide) Triblock Copolymers

Summary: Amphiphilic triblock copolymers (PEO_x‐b‐PDMS_y‐b‐PEO_x) with different block lengths were synthesized and multi‐morphological complex crew‐cut, star‐like, and short‐chain aggregates were prepared by self‐assembly of the given copolymers. The morphologies and dimensions of the aggregates can be well controlled by variation of the preparation conditions. TEM, SEM, FFR‐TEM, and LLS studies show the resulting morphologies range from LCMs, unilamellar or multilayer vesicles, LCVs, porous spheres to nanorods.

TEM images of the vesicles formed from PEO‐b‐PDMS‐b‐PEO.     

Direct Catalytic Hydrogenation of an Acrylonitrile‐Butadiene Rubber Latex Using Wilkinson's Catalyst

Summary: Hydrogenated acrylonitrile‐butadiene rubber is a high‐performance elastomer that has found important applications in the automobile industry and petroleum fields. A new catalytic process has been investigated for producing hydrogenated acrylonitrile‐butadiene rubber by direct hydrogenation of the rubber in latex form using RhCl(PPh₃)₃ as catalyst. The reactions were achieved without the addition of any organic solvents. This is the first time that the direct catalytic hydrogenation of an acrylonitrile‐butadiene rubber latex has been successfully realized in the absence of any organic solvent with a conversion of higher than 95% without cross‐linking of the polymer.

Effect of RhCl(PPh₃)₃/acrylonitrile‐butadiene rubber ratio on hydrogenation.     

Micelles Formed by Cylindrical Brush‐Coil Block Copolymers

Summary: Amphiphilic cylindrical brush‐coil block copolymers consisting of a polystyrene coil and a cylindrical brush block with poly(acrylic acid) side chains are prepared by ATRP of t‐butylacrylate from a block comacroinitiator. Upon acidolysis of the poly(t‐butylacrylate), water‐soluble polymers were obtained that were observed to form micelles consisting of 4–5 block copolymers on average in aqueous solution. The star‐like nature of such micelles was clearly visualized by scanning force microscopy.

Schematic of coil‐cylindrical brush block copolymer PS‐b‐(PⁱBEMA‐g‐PAA), its AFM image clearly showing the main chain and the PAA corona of the cylindrical brush block.     

Precision Synthesis of Poly(3‐hexylthiophene) from Catalyst‐Transfer Suzuki−Miyaura Coupling Polymerization

^tBu₃ PPd(Ph)Br ( 1 )‐catalyzed Suzuki‐Miyaura coupling polymerization of 2‐(4‐hexyl‐5‐iodo‐2‐thienyl)‐4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolane ( 2 ) was investigated. Monomer 2 was polymerized with 1 at 0 °C in the presence of CsF and 18‐crown‐6 in THF containing a small amount of water to yield P3HT with a narrow molecular weight distribution and almost perfect head‐to‐tail regioregularity. The values increased up to 11 400 g · mol⁻¹ in proportion to the feed ratio of 2 to 1 . The MALDI‐TOF mass spectra showed that P3HT with moderate molecular weight uniformly had a phenyl group at one end and a hydrogen atom at the other, indicating involvement of a catalyst‐transfer mechanism. Successive 1 ‐catalyzed polymerization of fluorene monomer 3 and then 2 yielded a well‐defined block copolymer of polyfluorene and P3HT.

     

Synthesis of Well‐Defined Rod‐Coil‐Rod Polyhexylisocyanate‐block‐polystyrene‐block‐polyhexylisocyanate via One‐Pot Anionic Polymerization

A rod‐coil‐rod block copolymer, polyhexylisocyanate‐block‐polystyrene‐block‐polyhexylisocyanate, of controlled molecular weight was synthesized quantitatively via living anionic polymerization using potassium naphthalenide in the presence of sodium tetraphenylborate. The use of K⁺ as the counterion for the polymerization of styrene, and Na⁺ (NaBPh₄) for the polymerization of isocyanate leads to the formation of a well‐controlled novel triblock copolymer.

     

Ordered Honeycomb‐Structured Films from Dendronized PMA‐b‐PEO Rod‐Coil Block Copolymers

Summary: Fabrication of honeycomb‐patterned films from amphiphilic dendronized block copolymer (PEO₁₁₃‐b‐PDMA₈₂) by ‘on‐solid surface spreading’ and ‘on‐water spreading’ method is reported. Highly ordered honeycomb films with quasi‐horizontally paralleled double‐layered structure can be fabricated by the on‐solid surface spreading method. This work raises the possibility that such structures can be formed in amphiphilic dendronized block copolymers and extends the family of source materials.

     

Hetero Diels–Alder Chemistry for the Functionalization of Single‐Walled Carbon Nanotubes with Cyclopentadienyl End‐Capped Polymer Strands

Single‐walled carbon nanotubes (SWCNTs) are pre‐functionalized with a pyridinyl‐based dithioester to undergo a hetero Diels–Alder (HDA) reaction with cyclopentadienyl end‐capped poly(methyl)methacrylate (M _n = 2700 g mol⁻¹, PDI = 1.14). Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis (EA), and X‐ray photoelectron spectroscopy (XPS) evidence the success of the grafting process. The estimated resulting grafting density (from XPS and EA) via the HDA reaction increases by a factor of more than two (0.0774 chains·nm⁻² via XPS) compared with typical values obtained via a direct cyclopentadiene driven Diels–Alder conjugation onto non‐functional SWCNTs under similar conditions.

     

Cationic Salt‐Responsive Bottle‐Brush Polymers

A class of cationic bottle‐brush polymers that show ionic strength‐dependent stimuli responsiveness is prepared. Brush polymers with norbornene as backbone and quaternary ammonium (QA)‐containing polycaprolactone copolymers as side chains are synthesized by a combination of ring‐opening metathesis polymerization, ring‐opening polymerization, and click reaction. In water with low ionic strength, brush polymers are soluble due to the strong electrostatic repulsion between cationic QA groups. As the addition of salt to increase ionic strength, single brush polymers undergo a transition from extended conformation to collapsed state and finally become insoluble in solution due to the screening effect of salts that yield the once‐dominant electrostatic interactions among QA species to hydrophobic–hydrophobic interactions.

     

Nanoporous Network Channels from Self‐Assembled Triblock Copolymer Supramolecules

Supramolecular complexes of a poly(tert‐butoxystyrene)‐block‐polystyrene‐block‐poly(4‐vinylpyridine) triblock copolymers and less than stoichiometric amounts of pentadecylphenol (PDP) are shown to self‐assemble into a core–shell gyroid morphology with the core channels formed by the hydrogen‐bonded P4VP(PDP)complexes. After structure formation, PDP was removed using a simple washing procedure, resulting in well‐ordered nanoporous films that were used as templates for nickel plating.

     

Synthesis of Oligosaccharide‐Branched Ribofuranan by Ring‐Opening Polymerization of a New Anhydroribo Trisaccharide Monomer

A new anhydroribotrisaccharide monomer, A2B3LR ( 1 ), was synthesized and ROP was carried out to elucidate the polymerizability and to obtain oligosaccharide‐branched polysaccharides with defined structures. The new trisaccharide monomer was found to be polymerized readily with BF₃ · OEt₂ as a catalyst at ?40 °C to give a lactose‐branched polymer. Copolymerization with ADBR gave the corresponding copolymers in good yields. After removal of protective benzyl groups, D ‐lactose‐branched ribofuranans with free hydroxyl groups were obtained in good yields. The structure of polymers was analyzed by ¹H, ¹³C, and two‐dimensional NMR measurements, suggesting that D ‐lactose‐branched ribofuranans had (1 → 5)‐α stereoregularity.

     

Diameter‐Dependence of the Morphology of PS‐b‐PMMA Nanorods Confined Within Ordered Porous Alumina Templates

Summary: Polystyrene‐block‐poly(methyl methacrylate) nanorods were prepared by wetting ordered porous alumina templates. We systematically investigated the diameter‐dependence of their morphologies by varying the pore diameters of the templates from 400 nm down to 25 nm. If the pore diameter exceeds the period of the block copolymer, the pores accommodate a non‐integer number of repeat periods. In case of smaller pores the occurrence of an ordered state could not be unambiguously verified.

TEM image of an ultra‐thin slice containing a cross‐section of a polystyrene‐block‐poly(methyl methacrylate) nanorod embedded in epoxy resin.     

3‐Ethylated N‐Vinyl‐2‐pyrrolidone with LCST Properties in Water

The monomer 3‐ethyl‐1‐vinyl‐2‐pyrrolidone ( 3 ) and the homopolymer poly(3‐ethyl‐1‐vinyl‐2‐pyrrolidone) ( 5 ) have been synthesized. Polymer 5 is soluble in water and shows a critical temperature (T_c) of 27 °C. The presence of cyclodextrin causes a slight shift of the T_c. The lower critical solution temperature (LCST) could be varied between 27 and 40 °C by copolymerization with N‐vinyl‐2‐pyrrolidone. A linear correlation between the T_c and the copolymer composition is observed.

     

In situ Synthesis of Magnetic Iron Oxide Nanoparticles in Thermally Responsive Alginate‐Poly(N‐isopropylacrylamide) Semi‐Interpenetrating Polymer Networks

A novel semi‐interpenetrating polymer network based on alginate and poly(N‐isopropylacrylamide) (PNiPAAm) has been synthesized that shows response to temperature and magnetic fields. Highly homogeneous porous hydrogels are obtained by copolymerizing N‐isopropylacrylamide and bis‐acrylamide in the presence of an aqueous alginate solution. The synthesis of magnetic iron oxides by in‐situ oxidation of iron cations coordinated to the alginate network results in a hydrogel with an enhanced deswelling rate with respect to pure PNiPAAm.

     

Coordination Polymer Nanobelts as an Effective Sensing Platform for Fluorescence‐enhanced Nucleic Acid Detection

In this communication, the application of coordination polymer nanobelts (CPNs) assembled from H₂PtCl₆ and 3,3′,5,5′‐tetramethylbenzidine (TMB) are explored as an effective fluorescent sensing platform for nucleic acid detection for the first time. The suggested method has a high selectivity down to single‐base mismatch. DNA detection is accomplished by the following two steps: (1) CPN binds fluorecent dye‐labeled single‐stranded DNA (ssDNA) probe via both electrostatic attraction and π‐π stacking interactions between unpaired DNA bases and CPN. As a result, the fluorescent dye is brought into close proximity to CPN and substantial fluorescence quenching occurs due to photoinduced electron transfer from the nitrogen atom in CPN to the excited fluorophore. (2) The hybridization of adsorbed ssDNA probe with its target generates a double stranded DNA (dsDNA). The duplex cannot be adsorbed by CPN due to its rigid conformation and the absence of unpaired DNA bases, leading to an obvious fluorescence enhancement.

     

Highly Active Syndiospecific Living Polymerization of Higher 1‐Alkene with ansa‐Fluorenylamidodimethyltitanium Complex

1‐Hexene polymerization was conducted by [t‐BuNSiMe₂(3,6‐t‐Bu₂Flu)]TiMe₂ ( 1 ) using trialkylaluminum‐free modified methylaluminoxane (dMMAO) as a cocatalyst in toluene. The system produced living syndiotactic poly(1‐hexene) with high turnover frequency of propagation (TOF, 98 s⁻¹) at 0 °C. The propagation rate was increased linearly against the 1‐hexene concentration, which indicates that the first‐order dependence of the propagation rate on monomer concentration. Polymerizations of 1‐octene, 1‐decene and 1‐dodecene were also conducted for investigating the effect of chain length of 1‐alkene on propagation rate by means of the livingness of this system. The propagation rate decreased according to the chain length until 1‐decene but almost unchanged in longer 1‐alkene: TOF, 1‐octene (62 s⁻¹)>1‐decene (32 s⁻¹) ≈ 1‐dodecene (31 s⁻¹).

     

Vapor‐Based Synthesis of Poly[(4‐formyl‐p‐xylylene)‐co‐(p‐xylylene)] and Its Use for Biomimetic Surface Modifications

Summary: The vapor‐based synthesis and characterization of a reactive polymer, poly[(4‐formyl‐p‐xylylene)‐co‐(p‐xylylene)] ( 1 ), have been reported. The reactive polymer coating enables the immobilization of oligosaccharides via the chemoselective aldehyde‐hydrazide coupling reaction.

     

Surfactant‐Induced Helix Formation of Cylindrical Brush Polymers with Poly(L‐lysine) Side Chains

The complex formation of oppositely charged surfactants with some polypeptides is known to induce β‐sheet or helix formation. Here, we report on the complex formation of cylindrical brush polymers with poly(L ‐lysine) side chains and sodium dodecylsulfate (SDS). With increasing amount of added surfactant the cylindrical polymers first adopt a helical conformation with a pitch of approximately 14–24 nm followed by a spherically collapsed structure before eventually precipitation occurs. CD measurements suggest that the helix formation of the cylindrical brush polymers is driven by the hydrophobicity of the β‐sheets formed by the PLL side chain–SDS complexes.

     

4H‐1‐Benzopyrans by a tandem SN2‐SNAr reaction

Treatment of 2‐fluoro‐5‐nitrobenzyl bromide with active methylene compounds in the presence of excess potassium carbonate in acetone leads to the formation of highly functionalized 4H‐1‐benzopyrans by a tandem S_N2‐S_NAr reaction sequence. The reaction works well with β‐keto esters, β‐keto sulfones, β‐keto phosphine oxides, β‐keto phosphonates and β‐keto nitriles. The reaction is simple to perform and affords products in 50‐92% yields.     

Fabrication of Patterned Polydiacetylene Composite Films Using a Replica‐Molding (REM) Technique

Functional three‐dimensional (3D) micropatterns of diacetylene supramolecules embedded in a host polymer have been successfully fabricated by a replica‐molding (REM) technique. Dimensional reduction as a result of liquid evaporation during the curing process does not affect the conformational features of the transferred patterns. Polymerization of the diacetylene vesicles using 254 nm UV‐light irradiation from the back‐side of the transparent substrate induces blue colored polydiacetylene (PDA) micro‐images. Interestingly, the polymerization selectively occurs in the molded areas because of the sub‐300 nm light blocking property of SU‐8. 3D fluorescence patterns are readily obtained by heat treatment of the blue images on the film.