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.
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 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.
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.
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.
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.
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.
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.
Amino acid‐based block copolymers containing poly(A‐Pro‐OMe) have been synthesized by RAFT polymerization using the dithioester‐terminated poly(DMA) as a macro‐CTA. An amphiphilic block copolymer composed of polystyrene as a hydrophobic segment and poly(A‐Pro‐OMe) as a hydrophilic segment was also prepared using polystyrene as the macro‐CTA. The chiroptical properties of the block copolymer, poly(DMA)‐block‐poly(A‐Pro‐OMe), was evaluated by specific rotation, CD, and UV‐vis spectroscopy. The assembled structure of the block copolymer on a mica surface was characterized by SFM. Thermally induced phase separations of the random and block copolymers were also studied in aqueous solution.
A comb copolymer with a fluorinated FPAE main chain and narrowly dispersed PMS graft chains has been prepared. The micellization behavior of this copolymer in a methanol/acetone mixture was studied. DLS studies showed hydrodynamic diameters of the micelles between 50 and 80 nm, while the diameters of dry micelles were ≈40 nm in TEM images. Micelle films with an interesting porous composite structure of nanofibers bearing micelle particles on the surface have been prepared by double coating the micelle solution. Superhydrophobicity with a WCA of 165° and a sliding angle of 3° was observed. As comb copolymers can adjust their molecular weight and block length independently, materials with a high physical strength and controllable morphological structure can be obtained.
The synthesis of a polymeric, photoresponsive drug‐delivery system on the basis of 4‐methylcoumarin‐side‐chain‐functionalized methacrylic copolymers with different degrees of functionalization is reported. Drug‐release experiments in solution indicated a maximum release of 22 µg of 5‐fluorouracil per 1 mg of polymer. Polymer analogous photochemical drug immobilization does not lead to observable intermolecular cross‐linking. Miscibility experiments with PMMA suggest that the bulk polymerization of homogeneous, transparent polymer sheets for intraocular lens fabrication, using MMA as the matrix monomer and incorporating the polymer‐drug conjugates as a functional component, is possible.
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.
Living free‐radical copolymerization of the inimer 4‐vinylbenzyl N,N‐diethyldithiocarbamate with maleic anhydride in the presence of methyl methacrylate produces highly branched poly(methyl methacrylate) star polymers. Subsequently, mikto‐arm stars can be synthesized by condensation of poly(ethylene glycol methyl ether) monosodium alkoxide with functional maleic anhydride sites in the hyperbranched core. The solution properties of these mikto‐arm star copolymers are discussed.
Homo‐ and copolymers of aniline and o‐toluidine have been synthesized using an inverse emulsion pathway; the copolymerization was initiated by benzoyl peroxide. The resulting homo‐ and copolymers are soluble in common organic solvents such as chloroform. Fairly higher doping percentages and polymerization yields for POT suggests that DBSA (a bulky molecule) can efficiently dope the polymer backbone by overcoming the steric hindrances created by the methyl substituent. However, in contrast to the PATs reported so far, solubility of POT as well as copolymers is lower than that of PANI. The homo‐ and copolymers have been characterized with UV‐Vis and FT‐IR spectroscopy, CV, in situ conductivity measurements and SEM. When dissolved in a 2:1 mixture of toluene and 2‐propanol, POT, unlike PANI and the copolymers, does not undergo any conformational rearrangement. A copolymer containing equimolar feed fractions of the comonomers has been obtained in higher yield and its morphology is similar to that of polyaniline.
A series of amphiphilic graft copolymers of poly(ethylene glycol)‐co‐glycidol‐graft‐(ε‐caprolactone) (PEG‐co‐PGL‐g‐PCL) with PEG as the hydrophilic backbone chain and hydrophobic PCL as side chains have been synthesized by living anionic polymerization and ring‐opening polymerization. By changing the composition of the PEG‐co‐PGL backbone chains, and the molar ratio of CL monomer to PEG‐co‐PGL in the feed, copolymers with well‐defined architecture and controllable numbers and length of graft chains can be obtained. The micellization and drug release of the PEG‐co‐PGL‐g‐PCL graft copolymers have been studied in terms of dependence on graft numbers and length, and the results indicate that the micelles with shorter PCL side chains have more compact cores and a relatively small size which are favorable for drug loading and controlled release.
It is demonstrated that copolymers of ethylene with higher 1‐olefins can be separated using bare silica gel as the stationary phase and a gradient of ethylene glycol monobutyl ether and 1,2,4‐trichlorobenzene as the mobile phase at 160 °C. The separation of ethylene 1‐hexene copolymers according to their composition is confirmed by linking the chromatographic separation to infrared spectroscopy. Using well‐characterised model fractions from temperature rising elution fractionation or solvent/non‐solvent fractionation (“Holtrup”), it can be shown that both the content and type of the comonomer mainly govern the elution in two peaks which differ in their comonomer content. The molar mass only plays a subordinate rule.
