摘要:

AbstractDoping with iodine of a liquid crystalline polymer in its different states was investigated for the first time. It was established that the polymer cannot be doped in solution, but it was doped to different, but rather high levels in the solid state and in frozen liquid crystalline and isotropic states. The products obtained exhibit intensive absorption in the visible region, higher electrical conductivity and paramagnetism. The successful doping of this non‐conjugated polymer in the solid state was explained by a collective interaction of several conjugated parts of the macromolecules (acting as extended conjugation) with iodin

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980401

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractDiblock copolymers of ethylene oxide andDL‐lactide (EmLncopolymers) were prepared by sequential anionic polymerisation and characterised by gel permeation chromatography (GPC) and13C NMR. Their association and surface properties in aqueous solution were studied by surface tension and dynamic and static light scattering. Comparison of the critical micelle concentrations (cmc) and micelle association numbers (Nw) of the EmLncopolymers with published values for oxyethylene/oxybutylene (EmBn) copolymers indicated a slightly lower hydrophobicity for a lactide unit: i.e. L ≃ 0.75B. The temperature dependence of the cmc of copolymer E42L12was analysed to obtain a standard enthalpy of micellisation ΔmicH0≈ 40 kJ

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980402

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractKinetics of radically initiated copolymerization of 6‐deoxy‐6‐methacryloylamido‐D‐glucopyranose (MAG) with 2‐hydroxyethyl methacrylate (HEMA) was investigated at 60°C in water using 4,4′‐azobis(4‐cyanopentanoic acid) as initiator. Reactivity ratios of the binary system were determined to berHEMA= 3.50 andrMAG= 0.60, indicating a strong copolymerization drift as polymerization proceeds. Copolymers with homogeneous composition were prepared using a simple and easy method based on the knowledge of the consumption rate of each monomer. These copolymers were then characterized with regard to composition (by1H NMR) and physicochemical properties in aqueous media (using SEC with MALLS and refractometry detection and viscosime

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980403

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractMetallopolymers in which bis(2,2′‐bipyridine)ruthenium(II) complexes are coordinated to imidazolyl residues on partially quaternized poly(1‐vinylimidazole) having different degree of quaternization (RuQPIm) were synthesized. The luminescence quenching of the photoexcited RuQPIms with various alkylviologens having different length of alkyl group was investigated in MeOH. In quenching of RuQPIm with methylviologen (MV2+), the efficiency of quenching decreases with increasing degree of quaternization. This was attributed to the electrostatic repulsion between the MV2+species and the quaternized imidazolium residue on the polymer backbone and steric hindrance of the alkyl side chain. Furthermore, the efficiency of quenching depends on the length of the alkyl group in viologen. These results suggest that the alkyl side chain on the polymer backbone exerts steric hindrance at low degree of quaternization and van der waals interaction at high degree of quaterniz

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980404

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe crystal structure, morphology and polymorphism induced by uniaxial drawing of poly(ether ether ketone ketone) [PEEKK] have been studied by transmission electron microscopy (TEM), electron diffraction (ED) and wide angle X‐ray diffraction (WAXD). On the basis of WAXD and ED patterns, the crystal structure of unoriented PEEKK is determined to have two‐chain orthorhombic packing with unit cell parameters ofa= 0.772 nm,b= 0.600 nm,c= 1.004 nm (form I). A stress‐induced crystal modification (form II) is identified and found to possess a two‐chain orthorhombic lattice with unit cell dimensions ofa= 0.461 nm,b= 1.074 nm,c= 1.080 nm. The 7.5% increase inc‐axis dimension for form II is attributed to an overextended chain conformation, arising from extensional deformation during uniaxial drawing and fixed “in‐situ” through strain‐induced crystallization. The average ether‐ketone bridge bond angles in form II crystal are determined to be 148.9° by using standard bond lengths. The crystal morphology of PEEKK bears a great similarity to that of PEEK. The crystals grow in the form of spherulites and have theb‐axis of unit cell radial. The effects of draw rate on strain‐induced crystallization and induction of form II stru

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980405

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe self‐diffusion coefficients of a styrene‐isoprene diblock and a styrene‐isoprene‐styrene triblock copolymer have been measured as functions of concentration in the neutral good solvent toluene. The sample block molecular weights are 1.0 × 104and 5.0 × 104g/mol for the diblock, and 1.0 × 104, 1.0 × 105and 1.0 × 104g/mol for the triblock, and the samples are designated SI‐60 and SIS‐120, respectively. Synchrotron small‐angle X‐ray scattering was utilized to locate the ordering transitions, and to identify the morphologies. SI‐60 exhibited an order‐order transition from a hexagonal to a cubic structure (i.e., from cylinders to spheres), prior to disordering, whereas SIS‐120 only exhibited the hexagonal phase. These results were compared to the melt, where both materials exhibit the cylinder‐to‐sphere transition. The concentration range for diffusion measurements extended into the ordered state: weight fractions up to 0.78 for SI‐60 and 0.62 for SIS‐120, where the corresponding ordering concentrations are 0.67 and 0.56. Diffusion measurements were performed by forced Rayleigh scattering and by pulsed‐field‐gradient NMR. The results indicate that substantial concentration fluctuations arise in solution prior to the ordering transition, and that these fluctuations act to retard chain diffusion. However, from comparison of the diblock and triblock mobilities, it appears that the retardation of mobility in the fluctuating and ordered states is due more to the increased monomeric friction in the (cylindrical) styrene‐rich microdomains, than to the thermodynamic barrier for escape of th

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980406

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractHeteroarm star copolymers bearing poly(2‐vinylpyridine) and polystyrene arms (AnBntype) were synthesized by a three‐step anionic polymerization method. Polystyrene arms are synthesized first, and they are used to initiate the polymerization of a small amount of divinylbenzene, yielding polystyrene star molecules bearing a number of active sites within its cores. In a subsequent step poly(2‐vinylpyridine) arms are growing from the cores. Poly(2‐vinylpyridine)‐block‐poly(tert‐butyl acrylate) star block copolymers [(AB)ntype] were also prepared using the same synthetic route. In this case, short polystyryllithium is used to build grafted poly(DVB) cores. These living plurifunctional initiators can easily polymerize 2‐vinylpyridine and subsequentlytert‐butyl acrylate, yielding star molecules bearing diblock copolymers as arms. The short polystyrene grafts of the core can be neglected and the star molecules are considered of the (AB)ntype. These star polymers have been characterized adequately and shown to exhibit rather well‐defined structures. The advantages and the drawbacks of the m

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980407

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe synthesis of a model water‐soluble drug carrier system based on poly(ethylene glycol) (PEG) block copolymers is described. In the system, two blocks of PEG are connected via a biodegradable oligopeptide or amino acid linkage incorporating at least one glutamic acid residue. A drug model (4‐nitroaniline) is attached to the γ‐carboxyl group of glutamic acid of the polymer carrier via an enzymatically degradable oligopeptide spacer. All oligopeptides were prepared as potential substrates for cathepsin B, a representative of lysosomal enzymes. The relationship between the structure of oligopeptides forming the linkage between two PEG molecules and the rate of cathepsin B‐catalyzed polymer chain degradation is evaluated. The relationship between the structure of the spacer and kinetics of drug model release from the carrier after incubation in cathepsin B solution is also discussed in detail. The results show that, by altering the structure of oligopeptides in the polymer construct, marked changes in the rate of both polymer degradation and the drug model release can be

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980408

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractWater sorption by amorphous statistical butyl acrylate (A unit) zwitterionomers bearing ammoniopropanesulfonate (B unit, N+(CH2)3SO 3−, μ = 24.0 D) or ammonioethoxydicyanoethenolate (B′ unit, N+(CH2)2OCOC−(CN)2, μ = 25.9 D) dipolar functional groups was studied at 23°C over a broad range of water activity (0.22

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980409

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe melting behavior of two non‐oriented poly(3‐alkylthiophene)s (P3ATs) containing 12 and 14 carbon atoms, respectively, in the alkyl side chain was investigated by means of differential scanning calorimetry. We show that the two P3ATs display three melting endotherms after an isothermal annealing from the melt. Two of the melting peaks arise from the ordered structures which are completed in the course of the quenching of the sample from the melt, and judging from the essentially constant melting temperatures and heats of fusion, they are not influenced by the subsequent isothermal annealing conditions. On the other hand, a much slower crystallization induced by the annealing, which occurs over a wide range of temperatures, is responsible for the appearance of a third melting endotherm which is strongly dependent on the crystallization condition. We show that this secondary crystallization is not a perfection of the existing ordered structures, rather it results in distinct crystals which melt at a temperatureTmslightly above the crystallization temperatureTc. Moreover, it is shown that the plot ofTmversusTcparallels the line ofTm=Tc, and that the differenceTm−Tcincreases linearly as the number of carbon atoms in the side chain decreases. On the basis of the calorimetric and X‐ray diffraction measurements, it is suggested that the secondary crystallization originates from the alkyl side

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980410

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY