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.
The cationic copolymerization of 2‐phenoxymethyl‐1,4,6‐trioxaspiro[4,4]nonane with DGEBA under microwave irradiation using ytterbium and lanthanum triflates as initiators is described. A comparison with thermal heating showed a great enhancement in the reaction rates and a higher SOE incorporation in the network. The double ring opening of SOE reduces the usual shrinkage of epoxy resins on curing, and it was lower under microwave irradiation. Moreover, the ytterbium triflate initiator lead to a higher incorporation of linear ester moieties in the network than lanthanum triflate.
Amphiphilic ABCBA pentablock copolymers based on PVP, PS, and PDMS were synthesized using a combination of ATRP and RAFT polymerizations. The PVP‐block‐PS‐block‐PDMS‐block‐PS‐block‐PVP pentablock copolymer was characterized using a variety of chromatography and spectroscopic methods which showed that a high degree of end group and molecular weight control can be achieved. Preliminary analysis of the aqueous solution behavior of the pentablock copolymer showed that it self‐assembles in water in order to shield the PDMS and PS segments from the water.
A self‐assembled lamellar‐within‐lamellar structure of a side chain liquid crystalline diblock copolymer was shear aligned to induce overall alignment and to direct the smectic layer orientation within the copolymer lamellae. The copolymer consisted of a polystyrene block and a poly(methyl methacrylate) block bearing cholesteryl mesogens with only short oxycarbonyloxyethyl spacers separating the mesogens from the backbone. Upon shearing, the copolymer lamellae exhibited uniaxial alignment whereas the smectic layers of the mesogens showed coexisting perpendicular and parallel orientations with respect to the copolymer lamellae. The fraction of the parallel oriented domains could be systematically increased by tuning the oscillation frequency and strain amplitude.
Organometallic‐mediated radical polymerization (OMRP) has emerged as a powerful new class of living controlled radical polymerization. In order to fulfill its potential in the polymerization of vinyl acetate (VOAc) and other challenging monomers, the effects of ancillary ligands on the metal‐alkyl bond dissociation energy in OMRP reagents must be thoroughly explored. Recent results investigating structure‐activity relationships in well‐defined cobalt, iron and chromium complexes will be discussed. The involvement of radical intermediates in oxidative addition of secondary alkyls for catalytic cross‐coupling reactions catalyzed by first row transition metals will also be examined for relevant design concepts.
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.
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.
Pressure‐volume‐temperature and surface tension behaviour were studied for random copolymers of styrene and acrylonitrile (SAN) and for poly(butylene terephthalate) (PBT). Results served to determine reduction parameters for the equation‐of‐states by Flory‐Orwoll‐Vrij and by Simha‐Somcynsky as well. Surface tension as a function of copolymer composition displays negative deviation from additivity. It indicates surface excess of styrene units. Similar behaviour with respect to copolymer composition was found for variation of interfacial tension between SAN and PBT. Thickness of surface region is around 1 nm and does not change with copolymer composition whereas extension of interfacial region between PBT and SAN copolymers varies strongly with copolymer composition between around 2 and 60 nm.
A straightforward synthesis of a conjugated rod/spacer/rod‐type block copolymer containing PCz electron‐donor and PDI electron‐acceptor blocks is described. Two chromophores are covalently connected through sebacate units as saturated spacer. The resulting donor/spacer/acceptor‐type block copolymer (PCz‐S‐PDI) can be applied to limit charge recombination between donor/acceptor interfaces and to control the scale length of nanostructure formation. PCz‐S‐PDI was used to produce a solar cell with the power conversion efficiency of 0.004%.
Tunable alkaline anion‐exchange membranes based on QPMBV are synthesized using a bottom‐up approach, miniemulsion copolymerization, which can incorporate functional groups into the copolymers with designated composition and high molecular weight. The mechanical and electrochemical properties of the obtained QPMBV membranes are tuned by varying the composition. It is found that the ion exchange capacity of the copolymer, the hydrophilicity of the copolymer chains, the molecular weight, and the glass transition temperature of the copolymers are essential to balance the mechanical and OH– transport properties of QPMBV membranes. QPMBV membrane fuel cells show the best power output and the long‐lasting fuel cell performance among the APE membranes in open literature.
A supramolecular polymer gel is formed by host‐guest interactions between a DB24C8‐based bis(crown ether) and a copolymer containing the dibenzylammonium moiety. The formation of the gel and its cross‐linked networks structure are evidenced by 1H NMR spectroscopy, viscometry, and SEM. Interestingly, the gel shows both pH‐ and thermoesponsive behaviors, and excellent self‐healing properties. The self‐healing property of the gel is tested by rheological measurements, and it can also be seen visually and directly. The presented work provides a new strategy for the construction of the self‐healing supramolecular polymer gels with potential applications in smart materials.
Multi‐walled carbon nanotubes (MWNT) were oxidized with nitric acid and resulting carboxy groups were transformed to amino groups with a diamine under microwave irradiation. Grafting of bisphenol‐A‐polycarbonate onto carboxy‐ and amino‐functional MWNT through transesterification or aminolysis resulted in weight increase up to 300%. The morphology of functionalized and grafted MWNTs was investigated with scanning force microscopy (SFM) and transmission electron microscopy (TEM). Depending on the type of functionalisation and the extent of grafting different morphologies were observed. Aminofunctional MWNT‐g‐PCs showed more “ball‐like” or irregular protrusions of grafted PC. Carboxyfunctional MWNT‐g‐PCs were more smoothly covered with PC.
Homopolypeptides of linear and star‐like architectures were prepared by polymerizing benzylic‐protected L ‐glutamic acid and L ‐aspartic acid N‐carboxyanhydrides (Glu NCA, Asp NCA) in DMF. The polymerization rate of the Glu NCA is faster than that of Asp NCA. Using a simple monoamino initiator, its hydrochloride, di‐, tri‐, and tetraamino functional initiators, homopolypeptides with well‐defined structures and molar masses were obtained. The molar‐mass averages of the poly(γ‐benzyl‐L ‐glutamate)s lie very close to calculated values, according to the initial [M]:[I] ratios, while those of the linear poly(β‐benzyl‐L ‐aspartate)s were lower than the predicted ones. PBAs had somewhat broader molar‐mass distributions than PBGs.
A novel tertiary amine and amino acid‐based “schizophrenic” pH‐responsive block copolymer, PDEA‐b‐PAP, has been synthesized by RAFT polymerization. By directly dissolving this copolymer in acid or basic aqueous solution block copolymer vesicles with switchable coronas and membranes were prepared. These novel assemblies were characterized using TEM, DLS, zeta potential, and SLS analysis.
Well‐defined six‐armed star poly(L ‐lactic acid) (PLLA) with a triphenylene core has been prepared by ring‐opening polymerization of L ‐lactide. As a result of strong π–π interactions between the triphenylene core and the multi‐walled carbon nanotubes (MWCNTs), the polymer was conveniently immobilized on the surface of the as‐received MWCNTs by a simple ultrasonic process while the intrinsic graphitic structure of the pristine MWCNTs is retained. The non‐covalent interaction between the carbon nanotubes and the polymer has been proven by the UV‐vis absorption spectra, the fluorescence spectra, the Raman spectra, and the X‐ray photoelectron spectra.
The morphological behavior of PS‐containing diblock copolymer blends is reported. Three sets of PS/PLA and PS/PEO blends are prepared and evaluated by SAXS, WAXS, DSC, and DMA. No macrophase separation is observed, and the formation of PLA/PEO composite cylinders is identified by SAXS for all compositions. The PLA and PEO segments in these blends have been found to be miscible and the crystallization of the confined PEO is suppressed in the ordered nanostructures. The domain spacing, diameter of composite cylinders, and order/disorder transition temperature could be tuned by varying the blend composition in the binary blends.
Photoreorientation of a stripe pattern consisting of an MPS structure in a Langmuir‐Blodgett monolayer by irradiation with linearly polarized light is achieved for the first time using a PDMS/poly(methacrylate) diblock copolymer with a liquid crystalline azobenzene‐containing side chain. The stripe MPS pattern in the trans azobenzene state is diminished by photoisomerization to the cis form upon UV light irradiation. By the erasure of the MPS structure, the anisotropic photo‐oriented stripe pattern is generated upon irradiation with linearly polarized visible light, the orientation of the stripe pattern being orthogonal to the electric vector of the light.
P2VN‐b‐PAA is a novel diblock copolymer which has potential as a self‐assembled nanoscale patterning material. Thin spin cast P2VN‐b‐PAA films rapidly reorganize to vertical lamellar with exposure to acetone vapor. P2VN‐b‐PAA lamellar morphology was aligned by electric field under acetone vapor at a significantly faster rate and at lower electric field strengths than other polymer systems. Observed dry etching selectivity for P2VN to PAA were comparatively high for a variety of etch gases, consistent with estimations from Ohnishi and ring parameters. Block copolymer self assembled patterns were transferred to silicon via two‐step CF4 and SF6 etching.
Butadiene/isoprene copolymers were prepared using the catalyst system V(acac)3‐MAO. The structure of the comonomers is trans‐1,4 and the butadiene and isoprene units are statistically distributed along the polymer chain. The attitude of the butadiene sequences to crystallize in the monoclinic form and to evolve in the hexagonal form is preserved in the copolymer for a certain range of composition. The temperature interval between the two endothermic events is progressively reduced by increasing the isoprene content. The monoclinic/hexagonal transition produces a considerable increase in the lamellar thickness of the polymers. Thermal degradation of the copolymers is influenced by the composition and takes place in two different stages: a series of cyclization and cross‐linking reactions occur before the decomposition step.
Well‐defined self‐assembled structures are obtained in the form of block copolymer (BCP) nanocomposites, prepared by blending octuply adenine (A)‐functionalized polyhedral oligomeric silsesquioxane (OBA‐POSS) nanoparticles (NPs) with a thymine (T)‐containing BCP (PS‐b‐PVBT); these nanocomposites are stabilized through complementary multiple hydrogen bonding interactions between the A and T units. A transition from one ordered morphology to another occurs upon increasing the content of OBA‐POSS NPs in the PS‐b‐PVBT diblock copolymer, namely lamellar structures at relatively low OBA‐POSS NP contents (<25 wt%) and cylindrical structures at higher OBA‐POSS NP contents (>25 wt%), with concomitant variations in the effective interaction parameter and the overall volume fractions of the two microphase‐separated domains.
