Graft copolymers with thermo‐sensitive PNIPAAm backbone and hydrophilic PEtOxa graft chains demonstrated typical amphiphilic behavior. For specific compositions stable micelle‐like aggregates were formed depending on the temperature. Applying long polyoxazoline side chains ( > 120), stable reversible micelle‐like aggregates with hydrodynamic radii of 30–40 nm could be obtained between 33 and 55 °C. These graft copolymers have been successfully crosslinked by electron‐beam irradiation in the micellar state yielding core/shell type nanogels with thermo‐reversible swelling behavior. The temperature dependent volume change of the new thermo‐responsive nanogels due to the phase transition of the PNIPAAm core has been verified by DLS.
A novel thermoresponsive polymer based on adamantyl‐terminated hyperbranched polyglycerol (HPG‐AD) is reported. The hydroxy‐terminated hyperbranched polyglycerol (HPG) is functionalized by esterification of HPG with 1‐adamantanecarbonyl chloride. The resulting HPG‐AD shows interesting lower critical solution temperature (LCST) phase transitions in aqueous solution, depending on polymer concentration and AD graft ratio. In addition, the LCST transition can be controlled by adding various amounts of β‐cyclodextrin (β‐CD) by a host/guest interaction. The adjustable thermoresponsive behaviors are studied by UV‐vis spectroscopy and dynamic light scattering.
A novel approach to amphiphilic polymeric Janus micelles based on the protonation/deprotonation process of poly(2‐vinylpyridine)‐block‐poly(ethylene oxide) (P2VP‐b‐PEO) diblock copolymers in THF is presented. It is found that addition of HCl to the micelles solution of P2VP‐b‐PEO copolymers leads to the formation of vesicles. Subsequently mixing a small amount of hydrazine monohydrate with the vesicle solution can induce the dissociation and reorganization of the vesicles into Janus micelles. When HCl is replaced by HAuCl4 precursors, composite Janus particles containing gold in P2VP blocks are obtained.
A combination of NMP and photoinitiated polymerization is suggested as a new strategy for the synthesis of graft copolymers. First, P(S‐co‐CMS) copolymer backbones with different chloromethyl content are prepared by NMP. The chloro functions are then converted into photosensitive 4‐phenyl pyridinium‐N‐oxide ion functions. Finally, these photoactive polymers are irradiated in the presence of MMA to obtain the graft copolymers. They and their precursors at various stages are characterized by spectroscopy and GPC. It is demonstrated that the irradiation of photoactive polymers in the presence of a hydrogen donors such as THF facilitates the conversion of pyridinium ions to hydroxyl groups.
Linear and branched poly(lactide)s and poly(lactide‐co‐glycolide)s are synthesized using stannous (II) 2‐ethylhexanoate and alcoholic co‐initators resulting in polymers with 1, 2, 25, or 51 arms. 1‐dodecanol is used to produce the 1‐arm polymer, poly(ethylene glycol) is used for the 2‐arm polymers, and poly(glycidol)s of appropriate molecular weights are used to initiate the 25‐ and 51‐arm branched polyesters. The polymers are evaluated by melt rheology and dynamic mechanical analysis. In vitro degradation is investigated in phosphate buffer pH 7.4 at 37 °C for 28 d for moisture uptake and mass loss. Degraded samples are analyzed by gravimetry, differential scanning calorimetry, dilute solution viscometry (Cannon‐Fenske), and gel‐permeation chromatography.
Large‐core star polymers (LCSPs) and polymer networks were prepared using sequential group transfer polymerization (GTP) for the synthesis of linear poly(methyl methacrylate) (polyMMA) arms, followed by their cross‐linking using a mixture of MMA monomer and ethylene glycol dimethacrylate (EGDMA) cross‐linker. High monomer/cross‐linker molar ratios and short arms favored the formation of polymer networks, whereas the opposite conditions favored the formation of LCSPs. LCSPs presented two populations: star polymers and covalently linked star polymer aggregates. The size of the non‐aggregated star polymers, and the size and fraction of the star polymer aggregates passed through a maximum as the amount of the monomer in the cross‐linking mixture increased. The degrees of swelling in tetrahydrofuran (THF) of the networks, the sol fraction extracted from them, and the percentage of linear polymer in the sol fraction increased as the degree of polymerization of the arms increased.
PEO‐based amphiphilic block copolymers that exhibit a pH responsive phase transition behavior are synthesized. The amphiphilic block copolymers show sharp phase transitions in the physiological pH (7.2) range of aqueous media. The block copolymers were efficient stabilizers for the preparation of superparamagnetic iron oxide nanoparticles in aqueous media. The resulting iron oxide nanoparticles in the size range of 5–30 nm showed a relatively good image on the basis of the results on their phantom test. All the materials were characterized by the combination of 1H NMR spectroscopy, size exclusion chromatography, UV/visible spectroscopic analysis, magnetization, transmission electron microscopy, electron diffraction, and X‐ray diffraction pattern analysis.
Pyrrole/EDOT copolymers were synthesized using environmentally benign enzyme catalysis. PSS was used as the solubilizing template and charge‐balancing dopant. Soybean peroxidase was utilized as a catalyst for the copolymerization reactions to yield poly(pyrrole‐EDOT)/PSS complex. Systematic studies were conducted with varying monomer feed ratios, temperature, and pH. Here we report for the first time, the enzyme catalyzed polymerization of pyrrole and EDOT at an elevated pH = 5. The polymer composition was determined using X‐ray photoelectron spectroscopy. Spectroscopic characterization [UV‐Vis, FTIR], thermal analysis, and electrical conductivity measurements for these complexes indicated the formation of stable conducting copolymers.
Three soluble electrochromic copolymers based on 4,4‐di‐octyl‐cyclopentadithiophene (DOCPDT): PDOCPDT‐OT, PDOCPDT‐PT, and PDOCPDT‐Cz were synthesized and the electrochromic properties were investigated. Colorimetric analysis revealed that red‐colored PDOCPDT‐OT, green‐colored PDOCPDT‐PT and their blue mother polymer PDOCTDT are cathodic coloration polymers. PDOCPDT‐Cz is yellow in its neutral state and shows an anodic electrochromism. The structural flexibility, color diversity, processibility and good electrochromic performance make octyl‐cyclopentadithiophene‐containing polymers prominent candidates for electrochromic applications.
PS‐b‐PMMA copolymers and blends of PS and PMMA were analyzed by the online coupling of LC at the critical point of adsorption and 1H NMR. The separation of the polymers was carried out at chromatographic conditions which correspond to the critical point of PMMA and the size exclusion mode of PS. It was shown that blends of PS and PMMA homopolymers could be well separated at critical conditions of PMMA. The analysis of both the copolymers and the blends were carried out by online coupled 1H NMR. The block copolymers were analyzed with respect to the chemical composition. LCCC‐NMR coupling was allowed to determine the individual blocks of the copolymers regarding molar mass. The data were compared with the separation at critical conditions of PS.
Three new low‐bandgap copolymers containing 3,6‐linked carbazole units are synthesized and characterized using a combination of spectroscopic and electrochemical techniques and DFT calculations. The electron‐withdrawing effect of the BTD units leads to a significant decrease of the optical bandgap from 2.59 eV for PBTC to 1.81 eV for PCDTBT, whereas pendant octyl chains on the thiophene ring lead to an increase of the gap to 2.05 eV for PCDOTBT due to steric hindrance. PBTC:PCBM photovoltaic devices exhibit a PCE of 0.35% with an EQE reaching 35% in the blue region of the solar spectrum whereas PCDTBT:PCBM blends are efficient over a wider spectral range due to the lower bandgap of PCDTBT.
The RAFT synthesis and solution properties of AB block copolymers of 4‐vinylbenzyltrimethylphosphonium chloride (TMP) and N,N‐dimethylbenzylvinylamine (DMBVA) is described. The pH‐dependent self‐assembly properties of the AB diblock copolymers were examined using of 1H NMR, DLS, and fluorescence spectroscopy. The size of the polymeric aggregates depends on the block copolymer composition/molecular mass. The self assembly is completely reversible, as predicted from the tunable hydrophilicity/hydrophobicity of the DMBVA residues. The AB diblock copolymers can be effectively locked in the self‐assembled state using a straightforward core crosslinking reaction between the tertiary amine residues of DMBVA and difunctional 1,4‐bis(bromomethyl)benzene.
Starting from THF and protected glycidols, linear multifunctional polyethers were prepared. Random copolymers were synthesized via cationic ROP while block copolymers were obtained via anionic ROP. Kinetic studies were carried out for the random copolymers. Poly(THF‐co‐glycidol) was converted in polymer‐analogous reactions first to phenoxy‐carbonyloxy‐methyl‐substituted polyethers and then to amphiphilic polyethers by conversion of the former substituted polyethers with different functional amines. The resulting amphiphilic polyesters were tested for their bacteriostatic effect.
Novel fluorinated polymer nanoparticles (PNPs) for 19F MRI were prepared by living radical polymerization initiated by a dendrimer. The dendritic macroinitiator with Br substituents was synthesized from hydroxy‐group‐terminated G2 polyamidoamine dendrimers. The arborescent fluorinated polymers of 2,2,3,3‐tetrafluoropropyl methacrylate and 2,2,2‐trifluoroethyl methacrylate were characterized in molecular weight, the number of arms, the degree of polymerization per arm, and the diameter as a whole. The PNP diameter was precisely controlled by the molecular weight in the range of 3–25 nm. In addition, the fluorinated PNP gave a narrow resonance by 19F NMR spectroscopy. These results indicate that the fluorinated PNP can be used as a new type of 19F MRI agent.
Two‐dimensional chromatographic methods were developed using LC‐CC in the first and SEC in the second dimension. These methods were applied for the investigation of PS‐b‐PI diblock copolymers synthesized by different approaches: sequential living anionic polymerization and coupling of living precursor blocks. The first dimension separates according to the individual block length of PS or PI blocks, whereas the second dimension separates with respect to the total molar masses of components. 2D‐LC analysis provides information on the purity of the reaction products, the presence of by‐products, the chemical compositions and the molar masses of all product components. The accuracy and selectivity of 2D‐LC is discussed.
Thermally stable copolymers with an alternating repeating structure, poly(RMI‐alt‐IB)s, were synthesized by radical copolymerization of N‐substituted maleimides containing a polar group with isobutene. The onset temperature of decomposition was higher than 300 °C and the glass‐transition temperature increased by the introduction of hydroxy and carboxy groups. IR spectroscopic analysis revealed the role of intermolecular hydrogen bonding on the thermal stability of the copolymers. It was also revealed that the amount of water absorbed into poly(RMI‐alt‐IB)s with a hydroxymethyl substituent was as high as 270% of the weight of the used polymer, while the introduction of a carboxy group resulted in lower water absorption properties.
The self‐assembly of PVPh‐b‐PS in different solvents was studied. Upon replacing toluene by THF as the solvent, the morphology of the resulting aggregates change from core‐shell spheres, rod‐like micelles and vesicles to onion‐like aggregates. With increasing block copolymer concentration, morphologies such as honeycomb‐like films, surfaces of aggregated large porous spheres, or pincushion‐like spheres with protruding tubular vesicle aggregates are observed. These surface‐patterned films show significantly enhanced hydrophobicity. The results suggest that a superhydrophobic behavior can be achieved, with a maximum contact angle of 158°, by using the pincushion‐like micellar structure.
We present an analysis of the temperature‐dependent dynamic behavior of the minority phase of photoaddressable block copolymers. Solid‐state 2H NMR investigations are compared with holographic experiments. The samples are diblock copolymers based on polystyrene (PS) and poly(1,2‐butadiene) (PB), where the PB minority segment is functionalized with different deuterated moieties. Solid‐state 2H NMR investigations were performed from 320 to 380 K in order to study the thermal behavior of the minority segment. Holographic experiments on thin films of the block copolymers yielded the photoinduced diffraction efficiency at different temperatures. The comparison of both datasets enables us to identify the glass transition temperature Tg of the minority phase.
The effect of sonication on the size and structure of polymeric aggregates formed by amphiphilic block copolymers was studied by the combination of dynamic and static light scattering. Poly(ethylene oxide)‐block‐polyisoprene, poly(ethylene oxide)‐block‐polystyrene diblock copolymers, and poly(ethylene oxide)‐block‐polyisoprene‐block‐poly(ethylene oxide) triblock copolymer were used as typical polymeric amphiphiles. Sonication was found to be an effective method to break up inter‐micellar associations and split large polymeric aggregates, present initially in the aqueous solutions, into monodisperse micelles. The content and type of hydrophobic block, copolymer solution‐preparation protocol, and copolymer concentration were also investigated as co‐factors in conjunction to the effect of sonication time.
The preparation and self‐assembly of poly(2‐glucopyranosyl‐1,6‐naphthalene‐1,4‐phenylene), P16NP2Glu , an amphiphilic, blue‐light‐emitting copolymer, is reported. The copolymer is soluble in polar solvents such as methanol/THF mixtures and even in water. The emission spectrum of P16NP2Glu shows a maximum at ≈400 nm for solutions containing the above solvents. Owing to the highly polar nature of the glucopyranose rings of P16NP2Glu , the formation of aggregates is observed. Uniform‐size nanospheres capable of emitting blue light are prepared in the solid phase. The critical micelle concentration and micelle sizes are determined by light‐scattering measurements. It is found that the emission maximum and fluorescence quantum yields depend on the aggregate formation of the copolymer.
