Enhancement of Photostability in Blue‐Light‐Emitting Polymers Doped with Gold Nanoparticles

A dramatic increase in the photostability of a blue‐light‐emitting polymer, poly(9,9‐dioctylfluorene), was achieved by the addition of 5–10 nm gold nanoparticles. The optical absorption band of the gold nanoparticles was tuned to resonate the triplet exciton ground state bandgap energy of the polymer. Photo‐oxidation rate of poly(9,9‐dioctylfluorene) was effectively reduced by doping the polymer with very small amounts (≈10⁻⁶–10⁻⁵ volume fraction) of the gold nanoparticles.

Retarded photo‐oxidation in PDOF nanocomposite films with various doped gold nanoparticles.     

Facile Fabrication of Functional Polypyrrole Nanotubes via a Reactive Self‐Degraded Template

Summary: Polypyrrole nanotubes with high electric conductivity and azo function have been fabricated in high yield via an in‐situ polymerization. During the process fibrillar complex of FeCl₃ and methyl orange (MO), acting as a reactive self‐degraded template, directed the growth of polypyrrole on its surface and promoted the assembly into hollow nanotubular structures.

TEM image of uncompleted PPy nanotubes synthesized in MO solutions after reaction for 40 min.     

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.

     

Binary Reactive/Inert Non‐Fouling Polymeric Surfaces

Binary reactive/inert antifouling polymer brushes were grafted via a two step surface initiated polymerization from printed initiator monolayer and provided robust, effective polymeric surfaces for bioattachment with distinguishably reduced non‐specific adsorption. This synthetic strategy can be harnessed to build complex binary polymeric structures on substrate surfaces and the polymer brush surfaces reported in the present paper can be widely used for versatile biological study.

     

Addition‐Fragmentation Chain Transfer Involving Dimers of α‐Methylvinyl Monomers Studied by ESR Spectroscopy: Competition between Fragmentation and Bimolecular Termination

Detection of the adduct radical by ESR spectroscopy and after‐effect ESR measurements of the adduct radical concentrations in the photosensitized polymerization of styrene (St) in the presence of dimers of α‐methylstyrene (MSD) and methyl methacrylate have revealed that the dominant mechanism of adduct radical loss changes from bimolecular termination to fragmentation as the temperature is increased beyond 90 °C for St/MSD.

     

Novel Chromophore‐Functionalized Poly[2‐(trifluoromethyl) adamantyl acrylate‐methyl vinyl urethane]s with High Poling Stabilities of the Nonlinear Optical Effect

Nonlinear optical vinyl polymers with high glass transition temperature (T_g) were prepared by the functionalization of a fluorinated acrylate‐methyl vinyl isocyanate copolymer. A modified pathway to obtain a thiophene bridged chromophore was worked out. Poled films of the polymers show a fairly high and stable nonlinear optical response, even at elevated temperatures.

The thiophene‐bridged chromophore, based on a substituted dicyanomethylene‐dihydrofuran acceptor, synthesized here.     

A Facile Strategy for Constructing Boron‐Rich Polymer Nanoparticles via a Boronic Acid‐Related Reaction

We present here a facile strategy for constructing Dextran‐poly(3‐acrylamidophenylboronic acid) (Dextran‐PAPBA) nanoparticles (NPs) through a radical polymerization of the monomer 3‐acrylamidophenylboronic acid (APBA) bound by dextran via a boronic acid‐diol reaction in aqueous solution. The synthesized Dextran‐PAPBA NPs are stable in a wide pH range. Their size and composition are tunable by varying the feeding molar ratio of the glucopyranoside unit in dextran to APBA. Additionally, the NPs have good biocompatibility and cell membrane penetrability, as demonstrated by in vitro experiments. Doxorubicin was encapsulated in the NPs and exhibited a sustained and strongly pH‐dependent release profile that would greatly favor the in vivo drug delivery performance of the NPs. The facility of this strategy together with the tunable boron content and outstanding drug release and cellular membrane crossing performance of the produced NPs should greatly boost their applications in boron neutron capture therapy (BNCT) and chemotherapy for cancer treatment.

     

Poly(amidoamine)s with 2‐Dithiopyridine Side Substituents as Intermediates to Peptide–Polymer Conjugates

Cystamine, when employed as a cross‐linking agent, leads to poly(amidoamine) networks, which on reaction with 2,2′‐dithiodipyridine turn into linear poly(amidoamine)s with side dithiopyridyl groups that easily undergo exchange reactions with reduced L ‐glutathione, a model thiol‐containing biologically active peptide. The resultant products represent the first examples of soluble poly(amidoamine)–peptide conjugates in which the peptide moieties are linked to the polymer chain by S S bonds stable in blood, but cleavable inside cells.

     

Chitinase‐Catalyzed Synthesis of a Chitin‐Xylan Hybrid Polymer: A Novel Water‐Soluble β(1 → 4) Polysaccharide Having an N‐Acetylglucosamine‐Xylose Repeating Unit

Summary: A chitin‐xylan hybrid polysaccharide having β(1 → 4)‐linked alternating structure of N‐acetyl‐D ‐glucosamine and D ‐xylose was synthesized via chitinase‐catalyzed polymerization. An oxazoline derivative of D ‐xylosyl‐β(1 → 4)‐N‐acetyl‐D ‐glucosamine ( 1 ) was effectively polymerized by the catalysis of chitinase from Bacillus sp., giving rise to a water‐soluble chitin‐xylan hybrid polysaccharide ( 2 ) in good yields. Molecular weights ( ) of 2 reached 1 500, which corresponds to 8–10 saccharide units.

A chitin‐xylan hybrid polysaccharide ( 2 ) synthesized via chitinase‐catalyzed polymerization.     

Water‐Soluble Carbon Nanotubes by Redox Radical Polymerization

Water‐soluble single‐ and multi‐walled carbon nanotubes (CNTs) were prepared by grafting polyacrylamide chains from the graphitic surface via ceric ion‐induced redox radical polymerization. The reducing functionalities were covalently attached to the tubes by peroxide‐assisted radical reaction. The results showed that polymer chains were grafted onto CNTs by the redox process. The redox radical polymerization initiated by carbon nanotube‐bearing functionalities not only provides a powerful strategy for modifying the carbon nanostructures but also gives us the knowledge of their sidewall chemistry.

     

Reversible Photocontrolled Swelling‐Shrinking Behavior of Micron Vesicles Self‐Assembled from Azopyridine‐Containing Diblock Copolymer

Poly(N‐isopropylacrylamide)‐block‐poly{6‐[4‐(4‐pyridyazo)phenoxy] hexylmethacrylate} (PNIPAM‐b‐PAzPy) was synthesized by successive reversible addition‐fragmentation chain transfer (RAFT) polymerization. In a water/tetrahydrofuran (H₂O/THF) mixture, amphiphilic PNIPAM‐b‐PAzPy self‐assembles into giant micro‐vesicles. Upon alternate ultraviolet (UV) and visible light irradiation, obvious reversible swelling‐shrinking of the vesicles was observed directly under an optical microscope. The maximum percentage increase in volume, caused by the UV light, reached 17%. Moreover, the swelling could be adjusted using the UV light power density. The derivation of this effect is due to photoinduced reversible isomerization of azopyridine units in the vesicles.

     

Stable Aqueous Dispersion of PEGylated Nanoparticles by Polyelectrolyte Complex Formation

Stable aqueous dispersions of nanoparticles were prepared by polyelectrolyte complex formation between well‐defined poly(ethylene glycol)‐block‐poly(2‐acrylamido‐2‐methyl‐1‐propane sodium sulfonate) and poly(ethylene glycol)‐block‐poly[2‐(dimethylamino)ethyl methacrylate] diblock copolymers. Controlled synthesis of the copolymers was achieved by water‐based atom transfer radical polymerization (ATRP). The nanoparticles were characterized by a quite narrow and monomodal size distribution as evidenced by dynamic light scattering (DLS) and confirmed by atomic force microscopy (AFM) after solution casting and freeze‐drying.

     

Synthesis of Folic Acid Functionalized PLLA‐b‐PPEGMA Nanoparticles for Cancer Cell Targeting

Poly(L ‐lactic acid)‐block‐poly(poly(ethylene glycol) monomethacrylate) (PLLA‐b‐PPEGMA) has been prepared by the ring‐opening polymerization of lactide with a double‐headed initiator, 2‐hydroxyethyl 2′‐methyl‐2′‐bromopropionate (HMBP), followed by atom transfer radical polymerization (ATRP) of poly(ethylene glycol) monomethacrylate (PEGMA). PLLA‐b‐PPEGMA nanoparticles with encapsulated Fe₃O₄ are prepared by a solvent evaporation/extraction technique, and then further functionalized with folic acid, a cancer targeting ligand. Our results show that such functionalized PLLA‐b‐PPEGMA nanoparticles have good potential as carriers for targeted drug delivery in cancer treatment.

     

Entanglement Transition in Hyperbranched Polyether‐Polyols

Are hyperbranched polymers capable of forming entanglements? This is the central issue of this contribution. Hyperbranched polyglycerol (hbPG) samples with different molecular weights (600–106 000 g · mol⁻¹), narrow polydispersities (1.2–1.8) and high degrees of branching (≈0.6) were prepared by anionic ring‐opening polymerization. The viscoelastic properties of these polymers with respect to molecular architecture and molar mass were investigated. At low molecular weights “classical” scaling behavior between zero shear viscosity and molecular weight can be observed, whereas between 3 000 and 10 000 g · mol⁻¹ a plateau‐like area is found. The results indicate entanglement dynamics when exceeding a critical molar mass ( ≈ 20 000 g · mol⁻¹) due to entangled hyperbranched polyglycerols.

     

Simulation of Styrene Polymerization by Monomolecular and Bimolecular Nitroxide‐Mediated Radical Processes over a Range of Reaction Conditions

Simulations of polymerization rate, molecular weight development and evolution of the concentrations of species participating in the reaction mechanism over a range of operating conditions, and a parameter sensitivity analysis showing the effects of temperature, activation/deactivation equilibrium constant and initial concentrations of controller and initiator (if present) on these variables are presented for the nitroxide‐mediated radical polymerization of styrene. The simulations were performed with a computer program based on a detailed reaction mechanism. The simulated profiles of conversion, number average molecular weight ( ), and polydispersity agree well with experimental data. Previously unknown activation energies for reactions involved in the mechanism are estimated. The temperature dependence of the kinetic rate constants obtained in this study will be useful for future modeling and optimization studies.

     

One‐Pot Fabrication of Supramolecular Polymer Particles via Situ Polymerization Stringed Assembly of a Two‐Monomer Microemulsion

Summary: A novel method, situ polymerization stringed assembly (SPSA), is proposed to prepare stable solid or hollow supramolecular polymer particles, which are assembled by numerous nanoparticles. By this method, the fabrication of primary nanoparticles (poly(methyl methacrylate), PMMA), the linkers (polyvinylpyrrolidone, PVP, chains) between the nanoparticles, and the final assembled solid or hollow particles could be achieved in just one‐pot by methyl methacrylate (MMA)/N‐vinylpyrrolidone (NVP) microemulsion polymerization under UV irradiation. The structures of the supramolecular particles can be changed from solid to hollow by tuning the mass ratio of MMA/NVP in the microemulsion. AFM, TEM, and SEM experiments are performed to identify the results.

AFM image of the PMMA/PVP solid particles obtained from the photopolymerization of the microemulsion containing 20 wt.‐% MMA, 10 wt.‐% NVP, and 5 × 10⁻² wt.‐% BP.     

Synthesis and Characterization of Novel Biodegradable Copolymers of 5‐Benzyloxy‐1,3‐dioxan‐2‐one and Glycolide

A series of novel biodegradable random copolymers of 5‐benzyloxy‐1,3‐dioxan‐2‐one (5‐benzyloxy‐trimethylene carbonate, BTMC) and glycolide were synthesized by ring‐opening polymerization. The copolymers were characterized by nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC). The incorporation of BTMC units into the copolymer chains results in good solubility of the polymers in common solvents. The in vitro degradation rate can be tailored by adjusting the composition of the copolymers.

The in vitro degradation of the homopolymers and poly(BTMC‐co‐GA) copolymers.     

Synthesis and Properties of Oligophenylene‐Layered Polymers

We report syntheses of phenylene‐, biphenylene‐, and terphenylene‐layered polymers with a xanthene scaffold by the modified Suzuki‐Miyaura coupling reaction. Their optical properties were studied in detail. The polymer end‐capped by nitrobenzene units, which act as fluorescence quenchers, exhibited the photo‐excited energy transfer from the layered oligophenylenes to the terminal units.

     

Optical Non‐Linearity from Montmorillonite Intercalated with a Chromophore‐Containing Dendritic Structure: A Self‐Assembly Approach

Chromophore‐containing dendritic structures (G1, G2) are utilized to intercalate layered silicates, which results in a large d‐spacing up to 126 Å. An exfoliated morphology is obtained by mixing the dendritic structure intercalated layered silicates with polyimide in N,N‐dimethylacetamide solution. The dendritic structures attached on the clay template would arrange in a non‐centrosymmetric manner. This self‐assembled arrangement brought about the electro‐optical coefficients of 5–6 pm · V⁻¹ for these relatively low chromophore‐containing organic/inorganic nanocomposites without resorting to poling. Excellent temporal stability (100 °C) is also achieved.