The isotropic melt of poly(l ‐lactic acid) (PLLA) and random l /d ‐lactide copolymers with 2% and 4% d ‐isomer co‐units in the chain has been crystallized at 90 °C, which leads to growth of α′‐crystals. The maximum melting temperature of the α′‐crystals is around 150 °C in case of the homopolymer, and decreases by about 10 and 15 K in the random copolymers containing 2% and 4% d ‐isomer co‐units, respectively. Analysis of the stability of the α′‐crystals requires suppression of formation of α‐structure, which is achieved by fast heating using a fast scanning chip calorimeter. For the PLLA homopolymer, the critical heating rate above which the α′/α‐transition is completely suppressed is around 30 K s–1, which significantly decreases in the copolymers due to the presence of d ‐isomer co‐units. The slower kinetics of the melting‐recrystallization process in such random l /d ‐lactide copolymers is explained by the required segregation of the chain defects.
Copolymerization of carbon dioxide (CO2) and propylene oxide (PO) is employed to generate amphiphilic polycarbonate block copolymers with a hydrophilic poly(ethylene glycol) (PEG) block and a nonpolar poly(propylene carbonate) (PPC) block. A series of poly(propylene carbonate) (PPC) di‐ and triblock copolymers, PPC‐b‐PEG and PPC‐b‐PEG‐b‐PPC, respectively, with narrow molecular weight distributions (PDIs in the range of 1.05–1.12) and tailored molecular weights (1500–4500 g mol?1) is synthesized via an alternating CO2/propylene oxide copolymerization, using PEG or mPEG as an initiator. Critical micelle concentrations (CMCs) are determined, ranging from 3 to 30 mg L?1. Non‐ionic poly(propylene carbonate)‐based surfactants represent an alternative to established surfactants based on polyether structures.
Here, the synthesis, characterization, and photovoltaic properties of four new donor–acceptor copolymers are reported. These copolymers are based on 4,4‐difluoro‐cyclopenta[2,1‐b:3,4‐b′] dithiophene as an acceptor unit and various donor moieties: 4,4‐dialkyl derivatives of 4H‐cyclopenta[2,1‐b:3,4‐b′]dithiophene and its silicon analog, dithieno[3,2‐b:2′,3′‐d]‐silol. These copolymers have an almost identical bandgap of 1.7 eV and have a HOMO energy level that varies from ?5.34 to ?5.73 eV. DSC and X‐ray diffraction (XRD) investigations reveal that linear octyl substituents promote the formation of ordered layered structures, while branched 2‐ethylhexyl substituents lead to amorphous materials. Polymer solar cells based on these copolymers as donor and PC61BM as acceptor components yield a power conversion efficiency of 2.4%.
A dual‐pH switchable zwitterionic copolymer, poly(2‐(dimethylamino)ethyl methacrylate‐co‐acrylamide‐co‐acrylic acid) (poly(DMAEMA‐co‐AM‐co‐AA)), is synthesized by random copolymerization. Characterized by a sharp change in solution turbidity, the conformation of such polymers in aqueous solutions can be switched at both acidic (low pH) and alkaline (high pH) conditions, with the switching pH being finely tunable by controlling the molar ratio of cationic and anionic functional groups of the copolymer. Study with quartz crystal microbalance with dissipation confirm the origin of the conformational change from electrostatic attractions between cationic DMAEMA and anionic AA functional groups.
A convenient one‐pot method for the controlled synthesis of polystyrene‐block‐polycaprolactone (PS‐b‐PCL) copolymers by simultaneous reversible addition–fragmentation chain transfer (RAFT) and ring‐opening polymerization (ROP) processes is reported. The strategy involves the use of 2‐(benzylsulfanylthiocarbonylsulfanyl)ethanol (1) for the dual roles of chain transfer agent (CTA) in the RAFT polymerization of styrene and co‐initiator in the ROP of ε‐caprolactone. One‐pot polymerizations using the electrochemically stable ROP catalyst diphenyl phosphate (DPP) yield well‐defined PS‐b‐PCL in a relatively short reaction time (≈4 h; = 9600?43 600 g mol?1; / = 1.21?1.57). Because the hydroxyl group is strategically located on the Z substituent of the CTA, segments of these diblock copolymers are connected through a trithiocarbonate group, thus offering an easy way for subsequent growth of a third segment between PS and PCL. In contrast, an oxidatively unstable Sn(Oct)2 ROP catalyst reacts with (1) leading to multimodal distributions of polymer chains with variable composition.
A family of novel (X‐TATAT)n‐type conjugated polymers based on the carbazole (X), thiophene (T), and benzoxadiazole (A) moieties is designed and explored as electron‐donor materials for organic bulk heterojunction solar cells. Incorporation of the branched side chains of different size and shape affects significantly the optoelectronic properties of the materials, particularly frontier energy levels of polymers translated to the open circuit voltages of the photovoltaic cells. The revealed unprecedented correlation between the parameters of the solar cells (V OC, fill factor (FF), J SC) and bulkiness of the alkyl side chains provides useful guidelines for rational design of novel materials for organic photovoltaics.
Histidine–zinc interactions are believed to play a key role in the self‐healing behavior of mussel byssal threads due to their reversible character. Taking this as inspiration, the authors synthesize here histidine‐rich copolymers, as well as model histidine compounds and characterize them using isothermal titration calorimetry (ITC). With this approach, the influence of two different zinc(II) salts and the role in the complex formation of the amine function of the imidazole ring are investigated in detail. The extracted metal–ligand ratios are utilized to design novel self‐healing metallopolymers. For this purpose, n‐lauryl methacrylate is copolymerized with the histidine monomer via reversible addition‐fragmentation chain transfer polymerization. The copolymers are crosslinked using different zinc salts, and the resulting coatings are characterized with Raman spectroscopy to investigate the metal coordination behavior and with scratch healing tests to investigate the self‐healing capacity. Finally, the self‐healing behavior of the different materials is correlated with the metal–ligand binding affinity measured by ITC.
A two‐step synthesis of high‐molecular‐weight and bio‐based poly(butylene succinate) (PBS) from succinic anhydride and butane‐1,4‐diol is established, in which the first step is a 12 h atmospheric polycondensation at 95 °C in the presence of succinic acid. The subsequent polymerization, catalyzed by Novozym 435 suspended in toluene, yields PBS with a molecular weight above 73 000 g mol?1. The recovered lipase catalyst appears to give similar performance after six cycles. The versatility of this atmospheric synthetic route to PBS copolymers is validated through the syntheses of poly(butylene succinate‐co‐butylene malate) (PBSM), poly(butylene succinate‐co‐butylene fumarate) (PBSF), and poly(butylene succinate‐co‐butylene terephthalate) (PBST), in which succinic acid is replaced by corresponding di‐acids as monomers.
The radical copolymerization of N‐substituted maleimides containing polymethylene and poly(ethylene oxide) side chains as the N‐substituent groups with isobutene, styrene, and α‐methylstyrene as the electron‐donating monomers is carried out in order to investigate the structure and thermal properties of the resulting comb‐like copolymers. The obtained copolymers show excellent thermal stability and their glass transition temperatures vary depending on the chain length of the introduced N‐substituents. The main‐ and side‐chain motions of the copolymers are investigated by dynamic mechanical analysis at various frequencies over the temperature range of ?150 to 100 °C.
Amphiphilic block copolymers based on sucrose methacrylate (SMA) and alkyl methacrylates (alkyl = ethyl, butyl, and hexyl) are synthesized by atom transfer radical polymerization, employing CuBr/CuBr2/2,2,2‐tribromoethanol/1,1,4,7,10,10‐hexamethyltriethylenetetramine as a catalyst/deactivator/initiator/ligand system. Poly(alkyl methacrylate)s with similar polymerization degrees are used as macroinitiators for SMA polymerization. The introduction of PSMA blocks with molar mass varying from 2000 to 12 000 g mol−1 results in changes in the solubility, thermal stability, and water swelling capacity. The copolymers are able to stabilize water/oil emulsion and also to self‐assemble in solution, as verified by gel permeation chromatography and dynamic light scattering, as well as in solid state, as verified by atomic force microscopy.
The application of selenol‐X chemistry in nucleophilic substitution and Se‐Michael addition reactions for polymer chain end modification is presented. Selenol‐labeled polystyrene can easily react with alkyl halides, methyl methacrylate, methyl acrylate, pentafluorostyrene, etc. The mild conditions make it attractive for the synthesis of macromonomers. The resulting polymers are analyzed and characterized by UV, size‐exclusion chromatography (SEC), NMR, and matrix assisted laser desorption/ionization time of flight mass spectroscopy.
Graft polymers with poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) as backbones are successfully prepared via two convenient steps. The utilization of semiflexible PPO as backbones offers unique properties for the graft polymers. Thermal, rheological, and phase behaviors of these new graft polymers are well controlled via the precise design of architectural parameters. The disordered microphase separation in melt state and the proper composition of side grafts provide the ease of thermal processing for these graft polymers. The graft density shows impact on the relaxation and mechanical properties of the thermoplastics. This work shows the possibility to use lots of semiflexible engineering polymers as backbones to construct new thermoplastics.
Polyetherethersulfones with double bonds inserted along the main polymer chain are synthesized by polycondensation. The glass transition is modulated by increasing the size of aromatic etherethersulfone rigid blocks and decreasing the ratio of flexible allyl segments which contain a double bond. Resulting copolymers have a Mn of up to 60 000 g mol?1, moderate polydispersity indices (? or Ip) of 1.70 to 2.11, and are shown, by the presence of a single glass transition temperature in differential scanning calorimetry and by matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry, to be random. The glass transition of copolymers follows the Gordon–Taylor relationship. The thermal resistance of copolymers increases when decreasing the amount of the flexible segment and increasing the length of the rigid block. Chemical aging of films is investigated by immersion in bleach, which is commonly used to clean membranes. Films show high resistance to bleach, therefore making this approach relevant to membrane fabrication.
Inspired by the well‐known amphiphilic block copolymer platform known as Pluronics or poloxamers, a small library of ABA and BAB triblock copolymers comprising hydrophilic 2‐methyl‐2‐oxazoline (A) and thermoresponsive 2‐n‐propyl‐2‐oxazoline (B) is synthesized. These novel copolymers exhibit temperature‐induced self‐assembly in aqueous solution. The formation and size of aggregates depend on the polymer structure, temperature, and concentration. The BAB copolymers tend to agglomerate in water, with the cloud point temperature depending on the length of poly(2‐n‐propyl‐2‐oxazoline) chain. On the other hand, ABA copolymers form smaller aggregates with hydrodynamic radius from 25 to 150 nm. The dependence of viscosity and viscoelastic properties on the temperature is also studied. While several Pluronic block copolymers are known to form thermoreversible hydrogels in the concentration range 20–30 wt%, thermogelation is not observed for any of the investigated poly(2‐oxazoline)s at the investigated temperature range from 10 to 50 °C.
Cu(I)‐catalyzed azide–alkyne cycloaddition is shown here to be an efficient method to create adhesive materials in situ between glass and copper surfaces. Twelve formulations show adhesive strengths greater than a commercial product under comparable conditions, with the best combination of monomers the same as that previously developed for copper–copper adhesion. Strong adhesion is also achieved under water, an environment in which the commercial glue fails. Brass, iron, and stainless steel could also be adhered to glass using different formulations, but aluminum could not. The concentration and molar ratio of monomers, curing temperature, prefunctionalization of the glass surface, and the incorporation of flexibility‐inducing components all have significant effects on adhesive performance.
Novel dual‐functional PEI‐poly(γ‐cholesterol‐l ‐glutamate) (PEI‐PCHLG) copolymers are developed for the first time. A series of PEI‐PCHLG (PEI‐1, PEI‐2, PEI‐3, and PEI‐4) with various PEI percentages and molecular weights are successfully synthesized, among which the poor organic solvent solubility of PEI‐1 precludes its further application. The other three copolymers can spontaneously self‐assemble into micelles; the critical micelle concentration (CMC) values are 0.66, 1.3, and 0.95 μmol L?1, respectively. PEI‐2 and PEI‐4, with lower CMC, are worth being further developed as promising drug carriers because of their resistance to dilution in circulation after systemic administration. However, PEI‐4 can form smaller‐sized micelles than PEI‐2 and has similar in vitro cytotoxicity to PEI. Thus, PEI‐4 is further investigated. PEI‐4 micelles can not only incorporate docetaxel (DTX) with high encapsulation efficiency (91.0%) and drug loading (4.3%), but also load pDNA efficiently at a ratio of 8:1 (w/w). DTX‐loaded PEI‐4 micelles (DTX‐PEI‐4) can also carry genes with the same gene‐binding capacity as PEI‐4 micelles. The above three micelles (DTX‐PEI‐4, pDNA‐PEI‐4, and pDNA/DTX‐PEI‐4) are sub‐micrometer‐sized and spherical. The results indicate that PEI‐4 containing 28.9% PEI, one of the PEI‐PCHLG copolymers, is a potential carrier for gene delivery, drug delivery, or even drug/gene co‐delivery.
A novel type of single white‐light‐emitting copolymers, PF‐DTFOx, derived from poly(9,9‐dioctylfluorene) (PF) in which 2,7‐di‐(2‐thienyl)‐9‐fluorenone (DTFO) is introduced as an orange‐emitting unit, is reported, and their application in white‐light polymer light‐emitting devices (PLEDs) is explored. Because of the very simple structure of DTFO, the synthetic routes to PF‐DTFOx are not complicated, and the raw materials are cheap; these are advantageous in reducing the fabrication cost of white‐light PLEDs. In the fluorescence spectra, PF‐DTFOx in solid powder shows dual peaks at around 460 and 560 nm. In white‐light PLEDs, the color of the white‐light emission is tunable; this can be achieved by changing the content of DTFO in PF‐DTFOx. The light‐emission color varies from blue‐white to pure white and orange‐white when the composition of DTFO increases. All the PLEDs based on PF‐DTFOx exhibit maximum luminance above 1800 cd m?2 and a color rendering index above 80.
New composite layer architecture of 3D hydrogel polymer network that is loaded with molecularly imprinted polymer nanoparticles (nanoMIP) is reported for direct optical detection of low‐molecular‐weight compounds. This composite layer is attached to the metallic surface of a surface plasmon resonance (SPR) sensor in order to simultaneously serve as an optical waveguide and large capacity binding‐matrix for imprinted target analyte. Optical waveguide spectroscopy (OWS) is used as a label‐free readout method allowing direct measurement of refractive index changes that are associated with molecular binding events inside the matrix. This approach is implemented by using a photo‐crosslinkable poly(N‐isopropylacrylamide)‐based hydrogel and poly[(ethylene glycol dimethylacrylate)‐(methacrylic acid)] nanoparticles that are imprinted with l ‐Boc‐phenylalanine‐anilide (l ‐BFA, molecular weight 353 g mol?1). Titration experiments with the specific target and other structurally similar reference compounds show good specificity and limit of detection for target l ‐BFA as low as 2 × 10?6 m .
Ion transport and selectivity are compared across a polymer inclusion membrane (PIM) containing dicyclohexano‐18‐crown‐6 (DCH18C6, K+ selective) under two driving forces: concentration gradient (diffusion) and electrical potential gradient (migration). The K+ flux is much larger under diffusion (140 mmol cm?2 h?1) than under migration (≈4 mmol cm?2 h?1). The selectivity of NH4+ over K+ is 86.0 for diffusion and 1.0 for migration. The selectivity of Na+ over K+ is 21.4 for diffusion and 1.16 for migration. Migration transport might induce a change in the orientation of DCH18C6 and reduce selectivity. Therefore, it is more favorable to apply diffusion rather than migration.
Polyacrylonitrile (PAN) with high molecular weight and low dispersity is successfully synthesized by visible‐light‐induced metal‐free radical polymerization at room temperature. This polymerization technique uses organic dye Eosin Y as photocatalyst and benzenediazonium tetrafluoroborates as initiator. Gel permeation chromatography‐multiangle laser light scattering shows the absolute molar weight of the PAN more than 1.50 × 105 g mol−1 with a polydispersity index < 1.3 while MALDI‐TOF MS and 19F NMR spectroscopy indicate the F‐chain‐end process. The first‐order kinetic behavior, molecular weight distributions shifting, and “ON/OFF” experiment results suggest this reaction may follow the atom‐transfer‐like radical polymerization mechanism. In addition, this new approach allows for the efficient synthesis of well‐defined random copolymers.
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