Positively charged nanoparticles (NPs) are very interesting for biomedical and pharmaceutical applications, such as nonviral gene delivery. Here, the synthesis of SiO2 nanoparticles with a covalently grafted poly(2‐ethyl‐2‐oxazoline) (PEtOx) shell (SiO2@PEtOx) is presented. PEtOx with a degree of polymerization of 20 and 38 is synthesized via microwave supported cationic ring‐opening polymerization and subsequently end‐functionalized with a triethoxysilyl linker for subsequent grafting to silica particles with hydrodynamic radii of 7, 31, and 152 nm. The resulting SiO2@PEtOx particles are characterized by using dynamic light scattering (DLS), transmission electron microscopy (TEM, cryoTEM), and scanning electron microscopy (SEM) to determine changes in particle size. Thermal gravimetrical analysis is used to quantify the amount of polymer on the silica surface. Subsequent in situ transformation of SiO2@PEtOx particles into SiO2@P(EtOx‐stat‐EI) (poly(2‐ethyl‐2‐oxazoline‐stat‐ethylene imine) grafted silica particles) under acidic conditions inverts the surface charge from negative to positive according to ζ‐potential measurements. The P(EtOx‐stat‐EI) shell could be used for the deposition of Au NP afterward.
Photoinitiated reversible addition‐fragmentation chain transfer (RAFT) dispersion polymerization of 2‐hydroxypropyl methacrylate is conducted in water at low temperature using thermoresponsive copolymers of 2‐(2‐methoxyethoxy) ethyl methacrylate and oligo(ethylene glycol) methacrylate (Mn = 475 g mol−1) as the macro‐RAFT agent. Kinetic studies confirm that quantitative monomer conversion is achieved within 15 min of visible‐light irradiation (405 nm, 0.5 mW cm−2), and good control is maintained during the polymerization. The polymerization can be temporally controlled by a simple “ON/OFF” switch of the light source. Finally, thermoresponsive diblock copolymer nano‐objects with a diverse set of complex morphologies (spheres, worms, and vesicles) are prepared using this particular formulation.
Here, the synthesis and the characterization of novel amphiphilic graft copolymers with tunable properties, useful in obtaining polymeric fluorescent nanoparticles for application in imaging, are described. These copolymers are obtained by chemical conjugation of rhodamine B (RhB) moieties, polylactic acid (PLA), and O‐(2‐aminoethyl)‐O′‐methyl poly(ethylene glycol) (PEG) on α,β‐poly(N‐2‐hydroxyethyl)‐d,l ‐aspartamide (PHEA). In particular, PHEA is first functionalized with RhB to obtain PHEA–RhB with a derivatization degree in RhB (DDRhB) equal to 0.55 mol%. By varying the reaction conditions, different amounts of PLA are grafted on PHEA–RhB to obtain PHEA‐RhB‐PLA with DDPLA equal to 1.9, 4.0, and 6.2 mol%. Then, PEG chains are grafted on PHEA‐RhB‐PLA derivatives to obtain PHEA‐RhB‐PLA‐PEG graft copolymers. The preparation of polymeric fluorescent nanoparticles with tunable properties and spherical shape is described by using PHEA‐RhB‐PLA‐PEG with DD in PLA and PEG equal to 4.0 and 4.9 mol%, by following easily scaling up processes, such as emulsion‐solvent evaporation and high pressure homogenization (HPH)‐solvent evaporation techniques.
The synthesis and formulation of organic semiconductors for the emerging technology of organic electronics requires the use of preparative methods and solvents being environment friendly. Today most of the active layer materials for the organic photovoltaic devices and modules are using chlorinated solvents, which are toxic and hazardous. In this work, the synthesis of poly[N‐9′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4,7‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole] (PCDTBT) in propan‐1‐ol is presented as the dispersant continuous phase in the presence of poly(vinylpyrrolidone) used as stabilizer. Suzuki–Miyaura polycondensation of 9‐(9‐heptadecanyl)‐9H‐carbazole‐2,7‐diboronic acid bis(pinacol) ester and 4,7‐bis(2‐bromo‐5‐thienyl)‐2,1,3‐benzothiadiazole in alcohol dispersion yields colloidally stable nanoparticles of PCDTBT with particles size of 330–1300 nm, depending on the stabilizer concentration. Other reaction parameters are also discussed such as the amount of base or Pd catalyst.
A supramolecular block copolymer is prepared by the molecular recognition of nucleobases between poly(2‐(2‐methoxyethoxy)ethyl methacrylate‐co‐oligo(ethylene glycol) methacrylate)‐SS‐poly(ε‐caprolactone)‐adenine (P(MEO2MA‐co‐OEGMA)‐SS‐PCL‐A) and uracil‐terminated poly(ethylene glycol) (PEG‐U). Because the block copolymer is linked by the combination of covalent (disulfide bond) and noncovalent (A U) bonds, it not only has similar properties to conventional covalently linked block copolymers but also possesses a dynamic and tunable nature. The copolymer can self‐assemble into micelles with a PCL core and P(MEO2MA‐co‐OEGMA)/PEG shell. The size and morphologies of the micelles/aggregates can be adjusted by altering the temperature, pH, salt concentration, or adding dithiothreitol (DTT) to the solution. The controlled release of Nile red is achieved at different environmental conditions.
The hierarchical self‐assembly of an amphiphilic block copolymer, poly(N,N‐dimethylacrylamide)‐block‐polystyrene with a very short hydrophilic block (PDMA10‐b‐PS62), in large granular nanoparticles is reported. While these nanoparticles are stable in water, their disaggregation can be induced either mechanically (i.e., by applying a force via the tip of the cantilever of an atomic force microscope (AFM)) or by partial hydrolysis of the acrylamide groups. AFM force spectroscopy images show the rupture of the particle as a combination of collapse and flow, while scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of partly hydrolyzed nanoparticles provide a clear picture of the granular structure.
The step‐wise solution self‐assembly of double crystalline organometallic poly(ferrocenyldimethylsilane)‐block‐poly(2‐iso‐propyl‐2‐oxazoline) (PFDMS‐b‐PiPrOx) diblock copolymers is demonstrated. Two block copolymers are obtained by copper‐catalyzed azide‐alkyne cycloaddition (CuAAC), featuring PFDMS/PiPrOx weight fractions of 46/54 (PFDMS30‐b‐PiPrOx75) and 30/70 (PFDMS30‐b‐PiPrOx155). Nonsolvent induced crystallization of PFDMS in acetone leads in both cases to cylindrical micelles with a PFDMS core. Afterward, the structures are transferred into water for sequential temperature‐induced crystallization of the PiPrOx corona, leading to hierarchical double crystalline superstructures, which are investigated using scanning electron microscopy, wide angle X‐ray scattering, and differential scanning calorimetry.
Well‐defined poly(2,5‐dihexyloxyphenylene‐1,4‐diyl) (PPP) is successfully synthesized by the Negishi catalyst‐transfer polycondensation (NCTP) using dilithium tetra(tert‐butyl)zincate (tBu4ZnLi2). The obtained PPP possesses the number‐averaged molecular weight (M n) values in the range of 2100–22 000 and the molar‐mass dispersity (Ð M) values in the range of 1.09–1.23. In addition, block copolymers containing PPP and poly(3‐hexylthiophene) (P3HT) segments (PPP‐b‐P3HT) are synthesized to confirm the feasibility of chain extension between the different monomers based on NCTP.
Development of self‐healing polymers with spontaneous self‐healing capability and good mechanical performance is highly desired and remains a great challenge. Here, mechanical robust and self‐healable supramolecular hydrogels have been fabricated by using poly(2‐dimethylaminoethyl methacrylate) brushes modified silica nanoparticles (SiO2@PDMAEMA) as multifunctional macrocrosslinkers in a poly(acrylic acid) (PAA) network structure. The SiO2 nanoparticles serve as noncovalent crosslinkers, dissipating energy, whereas the electrostatic interactions between cationic PDMAEMA and anionic PAA render the hydrogel self‐healing property. This process provides a simple and broadly applicable strategy to produce mechanical strong and self‐healable materials.
(Co)Polymers containing pentafluorophenylacetylene (F5PA) have been prepared for the first time mediated by [Rh(nbd)Cl]2/NEt3 to give materials with properties typical of poly(phenylacetylene)s prepared with this catalyst/co‐catalyst combination. It is demonstrated that the F5PA repeat units in these new (co)polymers serve as convenient reactive species for post‐polymerization modification with thiols via para‐fluoro aromatic nucleophilic substitution reactions to give an entirely new family of novel thioether‐functional polyene materials accompanied by absorption maxima shifts of up to 130 nm. Finally, the electrochemical properties of these new fluorinated polyene materials are briefly examined and the distinct difference in behavior of the F5PA homopolymer versus polyphenylacetylene, copolymers, and functional derivatives is highlighted.
A commercially available palladium N‐heterocyclic carbene (Pd‐NHC) precatalyst is used to initiate chain‐growth polymerization of 2‐bromo‐3‐hexyl‐5‐trimethylstannylthiophene. The molecular weight of the resultant poly(3‐hexylthiophene) can be modulated (7 to 73 kDa, Đ = 1.14 to 1.53) by varying the catalyst concentration. Mass spectrometry data confirm control over the polymer end groups and 1H NMR spectroscopy reveals that the palladium catalyst is capable of “ring‐walking”. A linear relationship between Mn and monomer conversion is observed. Atomic force microscopy and X‐ray scattering verify the regioregular nature of the resultant polythiophene.
Two soluble poly(phenyltriazolylcarboxylate)s (PPTCs) with high molecular weights (M w up to 26 800) are synthesized by the metal‐free 1,3‐dipolar polycycloadditions of 4,4′‐isopropylidenediphenyl diphenylpropiolate ( 1 ) and tetraphenylethene‐containing diazides ( 2 ) in dimethylformamide at 150 °C for 12 h in high yields (up to 93%). The resultant polymers are soluble in common organic solvents and are thermally stable with 5% weight loss temperatures higher than 375 °C. The PPTCs are nonemissive in solutions, but become highly luminescent upon aggregation, showing a phenomenon of aggregation‐induced emission. Their aggregates can be used as fluorescent chemosensors for high‐sensitivity detection of explosives.
Low‐molecular‐weight poly(ethylene glycol) (PEG) is deliberately incorporated into synthesized swellable poly(ethylene oxide) (PEO) membranes via a facile post‐treatment strategy. The membranes exhibit both larger fractional free volume (FFV) and a higher content of CO2‐philic building units, resulting in significant increments in both CO2 permeability and CO2/H2 selectivity. The separation performance correlates nicely with the microstructure of the membranes. This study may provide useful insights in the formation and mass transport behavior of highly efficient polymeric membranes applicable to clean energy purification and CO2 capture, and possibly bridge the material‐induced technology gap between academia and industry.
Two donor–acceptor copolymers based on isomeric acceptor units, [7,7′‐bithieno[2′,3′:4,5]thieno[2,3‐d ]thieno[3,2‐b ]pyridine]‐5,5′(4H ,4′H )‐dione (BTTP) and [2,2′‐bithieno[2′,3′:4,5]thieno[2,3‐d ]thieno[3,2‐b ]pyridine]‐5,5′(4H ,4′H )‐dione (iBTTP), are developed to study the effect of isomeric structures on photovoltaic performance. Compared with PBDTBTTP, PBDTiBTTP possesses a smaller bandgap for good light harvesting and a better π–π stacking for higher hole mobility. PBDTiBTTP solar cells present balanced mobilities and good nanoscale phase separation, giving a power conversion efficiency (PCE) of 6.51%, with higher short‐circuit current (J sc) and fill factor (FF).
To enhance the limited degradability of poly(ethylene glycol) (PEG), a straightforward method of synthesizing poly[(ethylene glycol)‐co‐(glycolic acid)] (P(EG‐co‐GA)) via a ruthenium‐catalyzed, post‐polymerization oxyfunctionalization of various PEGs is developed. Using this method, a set of copolymers with GA compositions of up to 8 mol% are prepared with minimal reduction in molecular weight (<10%) when compared to their commercially available starting materials. The P(EG‐co‐GA) copolymers are shown to undergo hydrolysis under mild conditions.
Two novel copolymers based on benzothiadiazole (BT) or difluorobenzothiadizole (ffBT) with 2,2′‐(perfluoro‐1,4‐phenylene)dithiophene (2TPF4), namely PBT‐2TPF4 and PffBT‐2TPF4, are synthesized for applications in polymer solar cells (PSCs). A noticeably high open‐circuit voltage (V oc) of 1.017 and 0.87 V are achieved for PffBT‐2TPF4 and PBT‐2TPF4‐based devices, respectively. Although only a moderate efficiency (5.7%) of PBT‐2TPF4‐based devices is obtained, it is first demonstrated that 2TPF4 is a promising acceptor block for construction of the donor copolymers which possess high V oc, prominent crystallinity, and long‐term stability, simultaneously. Besides, two thienyl flanking the tetrafluorophenylene can decrease torsion angle between conjugated units, resulting in a high coplanar structure of copolymers to enhance their charge carrier mobility. The findings may open a promising and practical way to accelerate the commercialization of PSCs by developing a series of new donor copolymers for efficient and long‐term stable thickness bulk heterojunction PSCs.
The controlled synthesis of poly(oligo(2‐ethyl‐2‐oxazoline)methacrylate) (P(OEtOxMA)) polymers by Cu(0)‐mediated polymerization in water/methanol mixtures is reported. Utilizing an acetal protected aldehyde initiator for the polymerization, well‐defined polymers are synthesized (>99% conversion, Ð < 1.25) with subsequent postpolymerization deprotection resulting in α‐aldehyde end group containing comb polymers. These P(OEtOxMA) are subsequently site‐specifically conjugated, via reductive amination, to a dipeptide (NH2‐Gly‐Tyr‐COOH) as a model peptide, prior to conjugation to the functional peptide oxytocin. The resulting oxytocin conjugates are evaluated in comparison to poly(oligo(ethylene glycol) methyl ether methacrylate) combs synthesized in the same manner for potential effects on thermal stability in comparison to the native peptide.
How to simply and efficiently separate and recycle catalyst has still been a constraint for the wide application of atom transfer radical polymerization (ATRP), especially for the polymerization systems with hydrophilic monomers because the polar functional groups may coordinate with transition metal salts, resulting in abundant catalyst residual in the resultant water‐soluble polymers. In order to overcome this problem, a latent‐biphasic system is developed, which can be successfully used for ATRP catalyst separation and recycling in situ for various kinds of hydrophilic monomers for the first time, such as poly(ethylene glycol) monomethyl ether methacrylate (PEGMA), 2‐hydroxyethyl methacrylate (HEMA), 2‐(dimethylamino)ethyl methacrylate (DMAEMA), N,N‐dimethyl acrylamide (DMA), and N‐isopropylacrylamide (NIPAM). Herein, random copolymer of octadecyl acrylate (OA), MA‐Ln (2‐(bis(pyridin‐2‐ylmethyl)amino)ethyl acrylate), and POA‐ran‐P(MA‐Ln) is designed as the macroligand, and heptane/ethanol is selected as the biphasic solvent. Copper(II) bromide (CuBr2) is employed as the catalyst, PEG‐bound 2‐bromo‐2‐methylpropanoate (PEG350‐Br) as the water‐soluble ATRP initiator and 2,2′‐azobis(isobutyronitrile) (AIBN) as the azo‐initiator to establish an ICAR (initiators for continuous activator regeneration) ATRP system. Importantly, well‐defined water‐soluble polymers are obtained even though the recyclable catalyst is used for sixth times.
For the first time, the successful Gilch synthesis of poly(ortho‐phenylene vinylenes) (ortho‐PPVs) is reported. The molar mass of the constitutionally homogeneous ortho‐PPVs reaches values as high as Mw ≈ 300 000 Da. The ortho‐connectivity of the repeating units forces the chains to assume closely packed conformations even in good solvents. Significant perturbation of the π–electron systems and considerable shortening of the conjugation lengths are the consequences. UV–vis absorption and photoluminescence maxima consequently are shifted clearly toward shorter wavelengths compared to, e.g., classic para‐PPVs.
Vinyl acetate is polymerized in the living way under the irradiation of blue light‐emitting diodes (LEDs) or sunlight without photocatalyst at ambient temperature. 2‐(Ethoxycarbonothioyl)sulfanyl propanoate is exclusively added and acts as initiator and chain transfer agent simultaneously in the current system. Poly(vinyl acetate) with well‐regulated molecular weight and narrow molecular weight distribution (Đ < 1.30) is synthesized. Near quantitative end group fidelity of polymer is demonstrated by nuclear magnetic resonance (NMR) and matrix‐assisteed laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS).
